阅读说明：本技术 检查设备和检查方法、以及半导体器件制造方法
(Inspection apparatus and inspection method, and semiconductor device manufacturing method
) 是由 李明俊
小泽谦
金郁来
朴光植
姜智薰
金洸秀 于 2019-05-20 设计创作，主要内容包括：描述了与基于结构照明(SI)的检查设备有关的系统和方法。基于SI的检查设备可以能够以高分辨率实时精确地检查检查对象,同时减少光的损失。还描述了检查方法,以及包括基于SI的检查方法的半导体器件制造方法。检查设备可包括：光源,配置为产生并输出光束；相移光栅(PSG),配置为将来自光源的光束转换成SI；分束器,配置为使SI入射到检查对象上并输出来自检查对象的反射光束；台架,能够移动检查对象并且在其上布置检查对象；以及延时积分(TDI)相机,配置为通过检测反射光束来捕获检查对象的图像。(Systems and methods related to a structured lighting (SI) based inspection apparatus are described. The SI-based inspection apparatus may be capable of accurately inspecting an inspection object in real time with high resolution while reducing loss of light. Inspection methods, and semiconductor device fabrication methods including SI-based inspection methods, are also described. The inspection apparatus may include: a light source configured to generate and output a light beam; a phase-shift grating (PSG) configured to convert a light beam from a light source into SI; a beam splitter configured to make the SI incident on the inspection object and output a reflected beam from the inspection object; a stage capable of moving an inspection object and arranging the inspection object thereon; and a Time Delay Integration (TDI) camera configured to capture an image of the inspection object by detecting the reflected light beam.)
1. An inspection apparatus based on structured lighting, the inspection apparatus comprising:
a light source configured to generate and output a light beam;
a phase-shifting grating configured to convert the light beam from the light source into the structured illumination;
a beam splitter configured to cause the structured illumination to be incident on an inspection object and to output a reflected beam from the inspection object;
a gantry configured to receive and move the inspection object; and
a time-lapse integrating camera configured to capture an image of the inspection object by detecting the reflected light beam.
2. The inspection apparatus of claim 1, wherein the phase-shift grating comprises a chrome-free phase-shift grating and is configured to transmit all of the light beams.
3. The inspection apparatus of claim 2, wherein
The phase-shift grating includes a first region of a first thickness and a second region of a second thickness greater than the first thickness, and
wherein the phase-shift grating is configured to modify a phase of the optical beam such that a phase of a first portion of the optical beam passing through the first region is different from a phase of a second portion of the optical beam passing through the second region.
4. The inspection apparatus of claim 3,
the phase shift grating has a line and space structure in which the first region and the second region are alternately arranged in a line pattern, and
the structure illumination is a bipolar illumination based on the line and space structure.
5. The inspection apparatus of claim 3,
the phase shift grating has an orthogonal structure in which the first region and the second region are alternately arranged in a first direction and a second direction perpendicular to the first direction, and
the structure illumination is based on quadrupole illumination of the orthogonal structure.
6. The inspection apparatus of claim 5,
the first region and the second region include a checkered shape, and
when the structured light is included in a rectangle, four illumination poles are formed near each side of the rectangle or near each vertex of the rectangle.
7. The inspection apparatus of claim 5,
the first region and the second region include a mesh shape, and
the second region is arranged at a junction position of the mesh shape.
8. The inspection apparatus of claim 1, wherein the reflected beam is detected by the time delay integration camera without passing through a grating.
9. The inspection apparatus of claim 1, wherein the time-lapse integrating camera is configured to photograph the inspection object while the inspection object moves in a first direction due to movement of the gantry in the first direction.
10. The inspection apparatus of claim 9, wherein the inspection apparatus is configured to integrate the images of the inspection object by accumulating and summing phases of the images captured by the time-lapse integrating camera.
11. The inspection device of claim 9, wherein the inspection device is configured to inspect the inspection object in real-time while the image of the inspection object is captured by the time-lapse integrating camera.
12. An inspection apparatus based on structured lighting, the inspection apparatus comprising:
a light source configured to generate and output a light beam;
a phase-shifting grating configured to transmit all of the light beams from the light source and produce illumination of the structure;
a beam splitter configured to cause the structured illumination to be incident on an inspection object and to output a reflected beam from the inspection object;
a gantry configured to receive and move the inspection object; and
a time-lapse integrating camera configured to detect the reflected light beam and capture an image of the inspection object,
wherein the inspection apparatus is configured to inspect the inspection object in real time by capturing an image of the inspection object using the time-delay integration camera while the inspection object is moving.
13. The inspection apparatus of claim 12, wherein the phase-shift grating does not include chrome and includes a first region of a first thickness and a second region of a second thickness greater than the first thickness.
14. The inspection apparatus of claim 13,
the phase-shift grating includes:
a line and space structure in which the first regions and the second regions are alternately arranged in a line shape, or
An orthogonal structure in which the first region and the second region are alternately arranged in a first direction and a second direction perpendicular to the first direction.
15. The inspection apparatus of claim 12,
the phase-shift grating is arranged between the light source and the beam splitter, and
the path from the inspection object to the time-delay integration camera does not pass through a grating.
16. The inspection apparatus of claim 12,
the inspection apparatus is configured to capture an image of the inspection object using the time-delay integration camera while the inspection object is moved in a first direction by movement of the gantry in the first direction, and
the inspection apparatus is further configured to integrate the images of the inspection object by accumulating and summing phases of the images captured by the time-lapse integrating camera.
17. An inspection method based on structured lighting, the inspection method comprising:
generating and outputting a light beam, wherein the generating and outputting are performed by a light source;
producing illumination of the structure in a phase-shifting grating by transmitting all of the light beam from the light source;
illuminating the structure via a beam splitter onto an inspection object;
outputting a reflected light beam from the inspection object; and
in a time-lapse integrating camera, an image of the inspection object is captured by detecting the reflected light beam.
18. The inspection method according to claim 17,
the phase shift grating comprises a chromeless phase shift grating and comprises a first region of a first thickness and a second region of a second thickness greater than the first thickness, wherein a phase of a first portion of the beam passing through the first region is different from a phase of a second portion of the beam passing through the second region, and
the phase-shifting grating is configured to produce the structured illumination by diffraction and phase shifting.
19. The inspection method according to claim 18,
the phase-shifting grating comprises a line and space structure in which the first and second regions are alternately arranged in a line, and wherein the phase-shifting grating is configured to produce dipole illumination.
20. The inspection method of claim 18, wherein the phase-shift grating comprises an orthogonal structure in which the first and second regions are alternately arranged in a first direction and a second direction perpendicular to the first direction, and wherein the phase-shift grating is configured to produce quadrupole illumination.
21. The inspection method of claim 17, further comprising:
capturing an image of the inspection object using the time-lapse integrating camera while the inspection object moves in a first direction; and
integrating the images by accumulating and averaging the phases of the images enables inspection of the inspection object to be performed without requiring post-image processing for integrating the images of each phase.
22. A semiconductor device manufacturing method, comprising:
generating and outputting a light beam, wherein the generating and outputting the light beam is performed by a light source;
producing structured illumination in a phase-shifting grating by transmitting all of the light beams from the light source;
illuminating the structure via a beam splitter onto an inspection object;
outputting a reflected light beam from the inspection object;
capturing an image of the inspection object using a time-delay integration camera by detecting the reflected light beam;
determining, based at least in part on the captured image, that there are no defects in the inspection object; and
performing semiconductor processing on the inspection object based on the determination.
23. The semiconductor device manufacturing method according to claim 22,
the phase-shift grating comprises a chromeless phase-shift grating and comprises a first region of a first thickness and a second region of a second thickness greater than the first thickness, wherein a phase of a first portion of the beam passing through the first region is different from a phase of a second portion of the beam passing through the second region; and is
The phase-shift grating includes: a line and space structure in which the first and second regions are alternately arranged in a line shape configured to produce bipolar illumination; or an orthogonal structure in which the first region and the second region are alternately arranged in a first direction and a second direction perpendicular to the first direction to generate quadrupole illumination.
24. The semiconductor device manufacturing method according to claim 22, wherein the reflected light beam does not pass through a grating;
capturing the image while the inspection object is moving in a first direction; and is
The manufacturing method further includes integrating the images by accumulating and averaging phases of the images, so that the manufacturing method can perform inspection of the inspection object without post-image processing for integrating the images per phase.
25. A method of inspecting an object under examination, comprising:
forming the light beam into a structured illumination pattern using a phase-shifting grating of an illumination optical system;
reflecting the light beam onto the inspection object using an imaging optical system different from the illumination optical system;
capturing a first image of the inspection object by detecting the reflected beam using a first sensor region of a line scan camera when the inspection object is at a first position;
capturing a second image of the inspection object by detecting the reflected beam using a second sensor region of the line scan camera when the inspection object is at a second position different from the first position;
integrating the first image and the second image by averaging a phase of the first image and a phase of the second image to produce an integrated image; and
determining in real time whether the inspection object includes a defect based on the integral image.
Technical Field
The present inventive concept relates to an inspection apparatus and an inspection method, and more particularly, to an inspection apparatus and an inspection method based on Structured Illumination (SI).
Background
As design rules in semiconductor manufacturing processes decrease, smaller anomalies on the wafer surface may become relevant. That is, the size of the potential defect may be reduced. As a result, it may become more difficult to detect these defects. In some cases, increasing the optical resolution of the inspection apparatus may enable the apparatus to detect smaller defects. For example, the optical resolution of the inspection apparatus can be improved by increasing the Numerical Aperture (NA) of the objective lens. However, the effectiveness of the high NA method may be limited based on the wavelength of the light used for inspection.
Another method of increasing optical resolution may include the use of Structured Illumination (SI). However, SI approaches may also be limited because they may be difficult to apply to certain optical systems, they may cause significant light loss, and they may rely on post-image processing.
Disclosure of Invention
The present inventive concept provides a Structure Illumination (SI) -based inspection apparatus and an inspection method for accurately inspecting an object in real time with high resolution and reducing light loss, and a semiconductor device manufacturing method based on the inspection method.
According to an aspect of the inventive concept, there is provided a Structure Illumination (SI) -based inspection apparatus, comprising: a light source configured to generate and output a light beam; a phase-shift grating (PSG) configured to convert a light beam from a light source into SI; a beam splitter configured to make the SI incident on the inspection object and output a reflected beam from the inspection object; a gantry configured to receive and move an inspection object; and a time-delayed integration (TDI) camera configured to capture an image of the inspection object by detecting the reflected light beam.
According to another aspect of the inventive concept, there is provided an SI-based inspection apparatus including: a light source configured to generate and output a light beam; a PSG configured to transmit substantially all of the light beam from the light source and to generate SI; a beam splitter configured to make the SI incident on the inspection object and output a reflected beam from the inspection object; a gantry configured to receive and move an inspection object; and a TDI camera configured to detect the reflected light beam and capture an image of the inspection object, wherein the inspection apparatus is configured to inspect the inspection object in real time by capturing the image of the inspection object using the TDI camera while the inspection object is moved.
According to another aspect of the inventive concept, there is provided an SI-based inspection method including: generating and outputting a light beam, wherein the generating and outputting are performed by a light source; in a PSG, SI is generated by transmitting substantially all of the light beam from the light source; making the SI incident on the inspection object via a beam splitter; outputting a reflected light beam from the inspection object; and in the TDI camera, capturing an image of the inspection object by detecting the reflected light beam.
According to another aspect of the inventive concept, there is provided a semiconductor device manufacturing method including: generating and outputting a light beam by a light source; in a PSG, SI is generated by transmitting substantially all of the light beam from the light source; in the beam splitter, making SI incident on the inspection object and outputting a reflected light beam from the inspection object; capturing an image of an inspection object by detecting a reflected light beam in a time-delay integration (TDI) camera; and performing semiconductor processing on the inspection object when there is no defect in the inspection object.
According to another aspect of the inventive concept, there is provided a method of inspecting an inspection object, including: forming the light beam into an SI pattern using a PSG of the illumination optical system; reflecting the light beam onto the inspection object using an imaging optical system different from the illumination optical system; capturing a first image of the inspection object by detecting a reflected beam using a first sensor region of the line scan camera when the inspection object is located at a first position; capturing a second image of the inspection object by detecting the reflected beam using a second sensor region of the line scan camera when the inspection object is at a second position different from the first position; integrating the first image and the second image by averaging a phase of the first image and a phase of the second image to produce an integrated image; and determining in real time whether the inspection object includes a defect based on the integrated image.
Drawings
Embodiments of the inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
fig. 1 is a conceptual diagram schematically illustrating a Structure Illumination (SI) based inspection apparatus according to an embodiment of the present disclosure;
fig. 2A-2E are conceptual diagrams illustrating various types of phase-shifted gratings (PSGs) used in the SI-based inspection apparatus of fig. 1 according to embodiments of the present disclosure;
FIG. 3A shows a cross-sectional view of the PSG of FIG. 2C taken along line I-I' and an intensity map of the illumination corresponding thereto;
FIG. 3B illustrates a cross-sectional view of a generic binary grating and an intensity map of illumination corresponding thereto, in accordance with an embodiment of the present disclosure;
fig. 4A-4E illustrate various types of PSGs and their corresponding SI and amplitude maps according to embodiments of the present disclosure;
fig. 5A and 5B are conceptual diagrams for designing a bipolar PSG and a quadrupole PSG, respectively, according to an embodiment of the present disclosure;
fig. 6A to 6C are conceptual diagrams illustrating an operation principle of a Time Delay Integration (TDI) camera included in the SI-based inspection apparatus of fig. 1 according to an embodiment of the present disclosure and illustrating an image capturing process by the TDI camera while an inspection object is moved;
fig. 7 is a conceptual diagram schematically illustrating an SI-based inspection apparatus according to an embodiment of the present disclosure;
fig. 8 is a flow chart of an SI-based inspection method according to an embodiment of the present disclosure; and
fig. 9 is a flow chart of a method of manufacturing a semiconductor device including an SI-based inspection method according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same constituent elements in the drawings, and repeated description thereof is omitted.
The present disclosure describes methods and apparatus for obtaining high resolution images using structured lighting techniques. In particular, the apparatus may be configured to perform a scanning method check using a Time Delay Integration (TDI) camera. The apparatus may also reduce optical loss by using a two-dimensional (2D) orthogonal chromeless phase shift grating. The methods and apparatus described herein may perform object examination in real-time by reducing the need for post-image processing.
Fig. 1 is a conceptual diagram schematically illustrating a Structure Illumination (SI) based inspection apparatus 100 according to an embodiment of the present disclosure.
Referring to fig. 1, an SI-based inspection apparatus 100 according to the present embodiment may include a light source 110, a phase-shift grating (PSG)130, a beam splitter 140, an objective lens 150, a stage 170, and a Time Delay Integration (TDI) camera 180.
The light source 110 may include a laser device that generates and outputs a laser beam. The laser beam from the light source 110 may be a pulsed laser. For example, the beam may be a Low Power Pulse (LPP) laser. The light beam of the light source 110 is not limited to the pulsed laser. For example, according to an embodiment, the light beam of the light source 110 may be a continuous wave laser.
The light source 110 may generate and output light beams of various wavelengths. For example, the light source 110 may generate and output light having a wavelength of about 248nm (KrF), about 193nm (ArF), or about 157nm (F)2) Of the light beam of (1). However, the light beam of the light source 110 is not limited to those of these wavelengths. For example, light source 110 may generate andan Extreme Ultraviolet (EUV) beam corresponding to several tens of nanometers is output.
The PSG130 may convert the light beam of the light source 110 into SI using diffraction and phase shift phenomena. For example, the PSG130 may convert the beam of the light source 110 into dipole illumination or quadrupole illumination. The SI generated by the PSG130 is not limited to dipole illumination and quadrupole illumination. For example, the PSG130 may produce octupole (8-pole) illumination or any other suitable illumination. SI may improve the resolution of the image. This may be because the incident angle of the adjacent light beams in SI is larger than that of general illumination, and thus, the resolution of the image may be improved due to the reduced limit resolution.
In some examples of the SI-based inspection apparatus 100, the PSG130 may not include a metal such as chromium. For example, the PSG130 may be a chrome-free PSG. Thus, the PSG130 may transmit substantially all of the light beam from the light source 110. However, since the speed of the light beam at each region through the PSG130 is different, a phase shift may occur. In addition, since the beam is diffracted while penetrating each region of the PSG130, the SI may be formed. The cross section, grating configuration and SI of the PSG130 are described in more detail in the description given with reference to fig. 2A to 6B.
The beam splitter 140 may make the SI formed by the PSG130 incident on the inspection object 200 and output a reflected beam from the inspection object 200 toward the TDI camera 180. For example, the beam splitter 140 may cause SI from the PSG130 to be incident on the inspection object 200 by transmitting or reflecting the SI, and may cause a beam reflected from the inspection object 200 to travel toward the TDI camera 180 by further reflecting or transmitting the reflected beam.
The objective lens 150 may cause the SI from the beam splitter 140 to be collected and incident on the inspection object 200. In addition, the objective lens 150 may cause a reflected light beam from the inspection object 200 to be incident on the beam splitter 140.
The examination object 200 may be disposed on the gantry 170. The stage 170 may move the inspection object 200 by linear movement in the x-direction, the y-direction, and the z-direction. Accordingly, the gantry 170 may also be referred to as an x-y-z gantry. According to various embodiments, the gantry 170 may move the inspection object 200 by a linear movement and/or a rotational movement.
As the gantry 170 moves in the scanning direction S as indicated by the arrow, the inspection object 200 may move in the scanning direction S. Accordingly, the TDI camera 180 can capture an image of the inspection object 200 while the inspection object 200 is moving in the scanning direction S. The image capture of the inspection object 200 by the TDI camera 180 is described in more detail with reference to fig. 6A to 6C.
The inspection object 200 may include various elements including a wafer, a semiconductor package, a semiconductor chip, a display panel, and the like. For example, in the SI-based inspection apparatus 100 of the present embodiment, the inspection object 200 may be a wafer including a plurality of semiconductor elements. For reference, the SI-based inspection apparatus 100 of the present embodiment may inspect the inspection object 200 to detect a defect thereof. The defects may be, for example, fine particles on the inspection object 200 and scratches formed on the inspection object 200. However, the defect is not limited to fine particles or scratches. Further, a defect may not represent all particles or all scratches, but may represent particles or scratches with dimensions that are out of tolerance. Hereinafter, the defect of the inspection object 200 can be understood from the above description.
Defects may result in poor quality of the inspection object 200 during subsequent processing. For example, when the inspection object 200 is a wafer, in subsequent semiconductor processing of the wafer, the defect may cause a poor quality of a semiconductor element in the wafer. By detecting a defect of the inspection object 200 and removing the defect in advance, it is possible to prevent the inspection object 200 from being poor in quality. In another example, by discarding the inspection object 200 based on detecting one or more defects, subsequent processing of the inspection object 200 that would result in unsuitable products may be omitted. Further, the method of preventing the occurrence of the defect can be identified by analyzing the cause of the defect.
The TDI camera 180 may be a camera that includes a plurality of pixels (in some examples, the pixels may be formed in a line shape). The TDI camera 180 may obtain a composite image by photographing an object at certain time intervals, and overlap and integrate images obtained at each interval. The TDI camera 180 may integrate the image in such a way that: the phases of the images are accumulated and averaged. Accordingly, the SI-based inspection apparatus 100 of the present embodiment can reduce or eliminate the need to perform post-image processing (e.g., in post-image processing, the phases of the images are considered and combined). The TDI camera 180 is described in more detail with reference to fig. 6A-6C.
The SI-based inspection apparatus 100 of the present embodiment may include an illumination relay lens unit 120, the illumination relay lens unit 120 including at least two relay lenses (120-1 and 120-2) for transmitting a light beam from the light source 110 to the inspection object 200. In addition, the SI-based inspection apparatus 100 may include an imaging relay lens unit 160, the imaging relay lens unit 160 including at least two relay lenses (160-1 and 160-2) for transmitting a reflected beam from the inspection object 200 to the TDI camera 180. In addition, the SI-based inspection apparatus 100 of the present embodiment may further include a collimating lens, a general filter, a plurality of mirrors, and the like, which are omitted and not shown.
The SI-based inspection apparatus 100 of the present embodiment can greatly improve the resolution of an image while reducing the loss of light by generating SI through the PSG130 and capturing the image of the inspection object 200 using the generated SI. Therefore, the SI-based inspection apparatus 100 of the present embodiment can use a light source of relatively low illumination, and furthermore, can acquire a high-resolution image of the inspection object 200 to accurately inspect the inspection object 200 for defects.
The SI-based inspection apparatus 100 of the present embodiment can perform high-speed capturing of the inspection object 200, and can reduce or eliminate the need to perform post-image processing. For example, the SI-based inspection apparatus 100 may alleviate the need to integrate an image in consideration of the phase of the image by capturing the image of the inspection object 200 using the TDI camera 180. Therefore, the SI-based inspection apparatus 100 can inspect the inspection object 200 in real time and significantly improve the inspection speed for inspecting the inspection object 200.
The SI-based inspection apparatus 100 of the present embodiment can arrange the PSG130 in the illumination optical system Ill-Optics by using the TDI camera 180. Therefore, the SI-based inspection apparatus 100 of the present embodiment can be easily used for a Bright Field (BF) method of a split optical system configuration in which the illumination optical system Ill-Optics and the imaging optical system Ima-Optics are separated from each other. Here, the illumination optical system Ill-Optics may denote an optical system on a path from the light source 110 to the objective lens 150, and the imaging optical system Ima-Optics may denote an optical system on a path from the objective lens 150 to the TDI camera 180. The BF method may denote a method of observing the inspection object 200 using direct illumination on the inspection object 200, and may be contrasted with a Dark Field (DF) method of observing the inspection object 200 using a scattered light beam.
Some inspection systems may utilize multiple shots for the same field of view (FOV) while rotating the grating, and a process of combining images of different phases by performing a Fast Fourier Transform (FFT) to integrate the images in the frequency domain and then restoring the images to the time domain by performing an inverse FFT. In other words, such systems may require significant post-image processing. This post-image processing can prevent the inspection of the inspection object 200 from occurring in real time.
To avoid post-image processing, the inspection apparatus may utilize a structure (not shown) of: by rotating the grating, the light beam passes through the grating twice, wherein the grating is arranged between the beam splitter and the objective lens. However, an inspection apparatus having such a structure may have a large amount of light loss, and may not be used in a separate optical system in which the illumination optical system Ill-Optics and the imaging optical system Ima-Optics are separated from each other. Further, the inspection apparatus of such a structure may not use the TDI camera because an area camera (area camera) may be required to capture an area image. Thus, the speed of the inspection apparatus can be very slow.
On the other hand, the SI-based inspection apparatus 100 of the present embodiment can solve these problems by including the PSG130 and the TDI camera 180. For example, the SI-based inspection apparatus 100 of the present embodiment can be easily used for a general separation optical system, can use a light source of relatively low illumination, and can inspect the inspection object 200 at high speed and in real time with high resolution.
Therefore, the SI-based inspection apparatus 100 can inspect the inspection object 200 by: forming the light beam into a Structured Illumination (SI) pattern in an illumination optical system Ill-Optics; an imaging optical system Ima-Optics different from the illumination optical system Ill-Optics is used to reflect the light beam onto the inspection object 200; capturing a first image of the inspection object 200 by detecting a reflected light beam using a first sensor region of a line scan camera (i.e., the TDI camera 180) while the inspection object 200 is at a first position; capturing a second image of the inspection object 200 by detecting the reflected beam using a second sensor region of the line scan camera while the inspection object 200 is located at a second position different from the first position; integrating the first image and the second image by averaging a phase of the first image and a phase of the second image to produce an integrated image; and determining in real time whether the inspection object includes a defect based on the integrated image.
Fig. 2A to 2E are conceptual diagrams illustrating various types of PSGs 130 used in the SI-based inspection apparatus 100 of fig. 1. Fig. 2A to 2E are described together with fig. 1, and a description of elements already given with reference to fig. 1 is briefly provided or omitted.
Fig. 2A illustrates the shape of illumination il before the beam passes through PSG130, according to an embodiment of the present disclosure. The illumination il may be formed by the light source 110 itself or when the light beam of the light source 110 passes through an aperture stop having the shape of the respective illumination il. For reference, the shape of the illumination il may be referred to as small sigma (σ) illumination, and sigma σ may correspond to the diameter or the value of the diameter multiplied by the Numerical Aperture (NA). The great circle on the outer side may correspond to a pupil plane.
Referring to fig. 2B, in the SI-based inspection apparatus 100, the PSG130a may have a line and space shape according to an embodiment of the present disclosure. Here, in the line and space shape of the PSG130a, the space may not be an empty space, but may be a thinner portion than the line (i.e., in a direction perpendicular to the surface of the PSG130 a). For example, the first portion 130a-1 corresponding to the space may be thinner than the second portion 130a-2 corresponding to the line. Regarding the cross-sectional structure of the PSG130a, a more detailed description is given with reference to fig. 3A and 3B.
PSG130a may produce bipolar illumination S-Illa, as shown at the bottom of FIG. 2B. The dipole illumination S-ila may be formed by diffraction and a phase shift that occurs when the small sigma illumination il in fig. 2A passes through the PSG130 a. Diffraction may occur when the beam passes through the first portion 130a-1 of the PSG130 a. For example, assuming that the second portion 130a-2 of the PSG130a is opaque and the light beam does not pass through, and assuming that the first portion 130a-1 and the second portion 130a-2 are equally spaced, the path of the diffracted light beam may be calculated by the following equation 1.
[ equation 1] Sin (θ) -Sin (θ i) ═ m λ/2d
Here, θ and θ i may denote a diffraction angle of a diffracted light beam and an incident angle of an incident light beam, respectively, 2d may denote a period of a pattern formed by the first and second portions 130a-1 and 130a, and m may be a diffraction order having 0, ± 1, ± 2, ·. As can be understood from equation 1, for incident beams of the same wavelength λ and the same incident angle θ i, as the period 2d of the pattern decreases, the diffraction angle of the diffracted beam increases. Therefore, by adjusting the period of the pattern, the position of the dipole illumination S-ila shown at the bottom of fig. 2B can be adjusted.
In the case of a binary grating, a metal layer such as chromium may be formed in the second portion 130a-2, and the light beam may not pass through the second portion 130 a-2. In this binary grating, an illumination pole can be further formed at the central portion by the 0-order diffracted beam component (see fig. 4A). However, in some embodiments of the SI-based inspection device 100 and the PSG130a, at least a portion of the beam may pass through the second portion 130 a-2. Since the light beam having passed through the second portion 130a-2 and the light beam having passed through the first portion 130a-1 may have a phase difference, an illumination pole may not be formed at the central portion.
The method of removing the center illumination pole can be implemented not only by modifying the PSG130a, but also by an off-axis binary grating. For example, by tilting the incident angle of the incident beam, only 0 order diffracted beam components and +1 or-1 order diffracted beam components may appear on the pupil plane.
Referring to fig. 2C, in the SI-based inspection apparatus 100, the PSG130b may have a checkered shape according to an embodiment of the present disclosure. In particular, the first portion 130b-1 and the second portion 130b-2 may be alternately arranged in the first direction (x direction) and the second direction (y direction). PSG130b may produce quadrupole illumination S-Illb, as shown at the bottom of fig. 2C. The quadrupole illumination S-Illb may be formed by diffraction and phase shift, both of which occur when the small sigma illumination Ill in fig. 2A passes through the PSG130 b.
Referring to fig. 2D, in the SI-based inspection apparatus 100, according to an embodiment of the present disclosure, the PSG 130C may have a checkered shape similar to the PSG130b of fig. 2C but rotated with respect to the PSG130b of fig. 2C.
For example, the first and second portions 130c-1 and 130c-2 may be alternately arranged in two diagonal directions (D1 and D2) between the first direction (x direction) and the second direction (y direction). PSG130 c may produce quadrupole illumination S-Illc, as shown at the bottom of fig. 2D. Quadrupole illumination S-Illc may be formed by diffraction and phase shift, both of which occur when the small sigma illumination Ill in fig. 2A passes through PSG130 c.
Comparing the PSG130b of fig. 2C with the PSG 130C of fig. 2D, a rotation of the PSG130b of fig. 2C by about 45 ° clockwise or counterclockwise may result in the PSG 130C of fig. 2D. Additionally, it is also understood that the quadrupole illumination S-Illc of the PSG 130C of FIG. 2D corresponds to a result of the quadrupole illumination S-Illb of the PSG130b of FIG. 2C rotating about 45. Thus, the PSG130b of fig. 2C and the PSG 130C of fig. 2D may not need to be manufactured separately in order to utilize both of them. In contrast, one of the PSG130b of fig. 2C and the PSG 130C of fig. 2D may be manufactured and disposed at the front end of the light source 110, and the other of the PSG130b of fig. 2C and the PSG 130C of fig. 2D may be obtained by rotation.
Referring to fig. 2E, in the SI-based inspection apparatus 100, the PSG130 d may have a mesh shape according to an embodiment of the present disclosure. In particular, the first portion 130d-1 may continuously extend in the first direction (x-direction) and the second direction (y-direction) like a mesh of a mesh. In addition, the second portion 130d-2 may be disposed at a knot position of the mesh and alternately disposed with the first portion 130d-1 in the first direction (x-direction) and the second direction (y-direction).
PSG130 d may produce quadrupole illumination S-Illd, as shown at the bottom of FIG. 2E. The quadrupole illumination S-Illd may be formed by diffraction and phase shift, both of which occur when the small sigma illumination il in fig. 2A passes through the PSG130 d.
It is understood that the quadrupole illumination S-Illd of PSG 130D of FIG. 2E and the quadrupole illumination S-Illc of PSG130 c of FIG. 2D may have similar structures. In both the quadrupole illumination S-Illc of PSG130 c of FIG. 2D and the quadrupole illumination S-Illd of PSG 130D of FIG. 2E, four illumination poles may be arranged adjacent to respective sides of the square. However, the quadrupole illumination S-Illb of the PSG130b of fig. 2C may be arranged such that the four illumination poles are adjacent to respective corners of the square. For reference, a structure in which the first portions (130b-1, 130C-1, and 130D-1) and the second portions (130b-2, 130C-2, and 130D-2) are alternately arranged in the first direction (x-direction) and the second direction (y-direction), respectively, such as the PSGs (130b, 130C, and 130D) in fig. 2C, 2D, and 2E, may be referred to as an orthogonal structure.
Fig. 3A illustrates a cross-sectional view of the PSG130B in fig. 2C taken along line I-I' and an intensity map of the illumination corresponding thereto, and fig. 3B illustrates a cross-sectional view of a general binary grating and an intensity map of the illumination corresponding thereto, according to an embodiment of the present disclosure.
Referring to fig. 3A, in the SI-based inspection apparatus 100, the PSG130b may include a first transparent layer 132 and a second transparent layer 134 according to an embodiment of the present disclosure. The first and second transparent layers 132 and 134 may include the same transparent material or different transparent materials. In one example, both the first and second transparent layers 132, 134 may include quartz. According to another example, only the first transparent layer 132 may include quartz, and the second transparent layer 134 may include another transparent material (e.g., glass and silicon oxide) instead of quartz. However, the materials of the first and second transparent layers 132 and 134 are not limited to the above materials.
The PSG130b may include a first region a1 including only the first transparent layer 132 and a second region a2 including both the first and second transparent layers 132 and 134. The first region a1 may correspond to a first portion of the PSG130b (refer to 130b-1 in fig. 2C), and the second region a2 may correspond to a second portion of the PSG130b (refer to 130b-2 in fig. 2C). In addition, structurally, the first and second regions a1 and a2 may correspond to the first and second portions (130a-1, 130c-1, and 130D-1) and (130a-2, 130c-2, and 130D-2) of the PSG (130a, 130c, and 130D) in fig. 2B, 2D, and 2E, respectively.
The first incident light beam L1in incident on the first region a1 and the second incident light beam L2in incident on the second region a2 may have the same phase at the interface surface between the second transparent layer 134 and the air. However, the first exit light beam L1out emitted through the first area a1 of the PSG130b may be out of phase with the second exit light beam L2out emitted through the second area a 2. In some cases, the first incident light beam L1in and the first exiting light beam L1out may correspond to a first portion of the light beam output by the light source 110. Similarly, the second incident light beam L2in and the second exiting light beam L2out may correspond to a second portion of the light beam output by the light source 110.
The first incident light beam L1in may pass through air up to the interface surface between the first transparent layer 132 and the air, and the second incident light beam L2in may pass through the second transparent layer 134 up to the interface surface between the first transparent layer 132 and the second transparent layer 134. Since the refractive indices of the air and the second transparent layer 134 are different from each other, the phases of the first and second incident light beams Llin and L2in at the interface surface between the first transparent layer 132 and the air or the interface surface between the first and second transparent layers 132 and 134 may be changed, and a phase difference may occur. Since both the first incident light beam Llin and the second incident light beam L2in pass through the first transparent layer 132, the first transparent layer 132 may have substantially the same thickness throughout, so the phase difference at the interface surface between the first transparent layer 132 and the air on the exit surface may remain as it is. As a result, the first outgoing light beam L1out and the second outgoing light beam L2out can maintain the phase difference that has been generated when they pass through the air and the second transparent layer 134.
Fig. 3B illustrates a generic binary grating 30, which generic binary grating 30 may include a quartz transparent layer 32 and an opaque chromium layer 34 on the quartz transparent layer 32, according to embodiments of the disclosure. In other words, the binary grating 30 may include a first region B1 including only the quartz transparent layer 32 and a second region B2 including both the quartz transparent layer 32 and the opaque chrome layer 34. The general binary grating 30 may have a form similar to the PSGs (130b, 130C, and 130d) in fig. 2C to 2E. However, the opaque chrome layer 34 may be disposed in the second portion (130b-2, 130c-2, and 130d-2) instead of the second transparent layer 134.
The first incident light beam L1in incident on the first region B1 of the binary grating 30 may pass through the quartz transparent layer 32 and travel as the first outgoing light beam L1out in the same direction as the first incident light beam L1 in. In contrast, the second incident light beam L2in incident on the second region B2 of the binary grating 30 may be reflected by the opaque chrome layer 34 and travel as a second reflected light beam L2re in a direction opposite to the direction of the first incident light beam L1 in. In other words, the second incident light beam L2in may not pass through the binary grating 30.
In some examples of the SI-based inspection apparatus 100, all or substantially all of the incident light beam may substantially pass through the PSG130 (e.g., pass through the PSG130b of fig. 3A). In other words, the second region a2 of the PSG130b may delay the light beam and make the phase of the second region a2 different from the phase of the light beam passing through the first region a1, but may not actually block the light beam.
On the other hand, in the case of the binary grating 30, the light beam may not pass through the second region B2 at all. Therefore, as shown in the following graph, the intensities of the PSG130b and the binary grating 30 may be significantly different from each other. For example, in the case of the binary grating 30 of fig. 3B, light loss may occur (possibly over 50%) due to the second region B2. Therefore, the light beam having passed through the PSG130b and the light beam having passed through the binary grating 30 may show a difference of intensity greater than 2 times. However, the intensity difference of the light beam having passed through the binary grating 30 and the PSG130b is not limited to this value.
Fig. 4A-4E illustrate various types of PSGs and their corresponding SI and amplitude maps, according to embodiments of the present disclosure. In the magnitude graph, the x-axis and y-axis may represent position, the z-axis may represent magnitude of illumination, and the units may be related. The description that has been given with reference to fig. 1 to 3B is briefly provided or omitted.
Referring to FIG. 4A, a tripolar illumination S-Ill may be formed by the binary grating 30. Here, the binary grating 30 may have a line and space structure similar to the PSG130a in fig. 2B. In other words, the binary grating 30 may comprise a transparent layer (see 32 in FIG. 3B) in a first portion (see 130a-1 in FIG. 2B) corresponding to the space, and a quartz transparent layer 32 and a chromium layer (see 34 in FIG. 3B) in a second portion (see 130a-2 in FIG. 2B). As described above, the tripolar illumination S-Ill caused by the binary grating 30 may include an illumination pole caused by a 0-order diffracted beam component at the central portion.
In the amplitude map, the amplitude may be relatively small because about 50% or less of the beam passes through the binary grating 30. However, when the pattern formed by the first and second portions of the binary grating 30 has the first pitch P1, the waveform of the three-pole illumination S-Ill may accordingly have the first pitch P1.
Referring to fig. 4B, a bipolar illumination S-ila may be formed by PSG130a in fig. 2B, according to an embodiment of the present disclosure. As described above, the bipolar illumination S-ila may not include an illumination pole at the central portion. In the amplitude map, the amplitude may be relatively large since the light beam passes through the PSG130a with an intensity of about 100%. When the pattern formed by the first portion (see 130a-1 in fig. 2B) and the second portion (see 130a-2 in fig. 2B) of the PSG130a has the second pitch P2, the illumination waveform may have a pitch of P2 x 0.5 corresponding to half of the second pitch P2. A more detailed description of the calculation of the second pitch P2 of the waveform of the PSG130a is given with reference to fig. 5A.
Referring to FIG. 4C, a bi-polar illumination S-Ill 'may be formed by the off-axis binary grating 30', according to embodiments of the present disclosure. Here, the off-axis binary grating 30' may have substantially the same structure as the line and space structure of the binary grating 30 of fig. 3B. The off-axis binary grating 30' may include a first portion of a quartz transparent layer 32 and a second portion of the quartz transparent layer 32 and an opaque chromium layer 34. However, in the case of the off-axis binary grating 30', the incident angle at which the light beam is incident may be different from that in the case of the binary grating 30 in fig. 4A. The dipole illumination S-Ill 'due to the off-axis binary grating 30' may not include an illumination pole at the center portion. In the bipolar illumination S-Ill', the left illumination is most likely due to the 0-order diffracted beam component, and the right illumination is most likely due to the + 1-order diffracted beam component.
In the amplitude map, the amplitude of the beam may also be relatively small since less than about 50% of the beam passes through the off-axis binary grating 30'. When the pattern formed by the first and second portions of the off-axis binary grating 30' has a first pitch P1, the illumination waveform may have a pitch of about 0.5 × P1 corresponding to half of the first pitch P1.
Referring to fig. 4D, a quadrupole illumination S-Illb may be formed by PSG130b in fig. 2C, according to an embodiment of the present disclosure. In the amplitude map, since the light beam passes through the PSG130b (i.e., corresponding to the PSG130b of fig. 3A) with an intensity of about 100%, the amplitude of the light beam may be relatively large. However, when the pattern formed by the first portion (see 130b-1 in fig. 2C) and the second portion (see 130b-2 in fig. 2C) of the PSG130b has a third pitch P3 of about P3 in both the first direction (x-direction) and the second direction (y-direction), the illumination waveform may have a pitch of about 0.5P 3 corresponding to half of the third pitch P35 3 in both the first direction (x-direction) and the second direction (y-direction). A more detailed description of the calculation of the third pitch P3 of the waveform of the PSG130B is given with reference to fig. 5B.
Referring to fig. 4E, a quadrupole illumination S-Illc may be formed by PSG130 c in fig. 2D, according to an embodiment of the present disclosure. In the amplitude map, the amplitude of the beam may be relatively large since the beam passes through the PSG130 c with substantially about 100% intensity. The illumination waveform of the PSG130 c in fig. 4E may correspond to the case where the illumination waveform of the PSG130b in fig. 4D is rotated about 45 ° clockwise or counterclockwise. Accordingly, the relationship between the pitch of the PSGs 130c and the pitch of the illumination waveform in fig. 4E may be substantially the same as the pitch of the PSGs 130b and the pitch of the illumination waveform in fig. 4D.
As described above, it can be easily understood that the quadrupole illumination (see the quadrupole illumination S-Illd in fig. 2E) substantially the same as the form of the quadrupole illumination S-Illc is realized by the PSG130 d in fig. 2E.
For reference, by comparing fig. 4A to 4E with each other, when the contrast of the dipole illumination S-ila, the quadrupole illumination S-Illb, and the quadrupole illumination S-Illc in fig. 4B, 4D, and 4E is defined as about 1, the contrast of the quadrupole illumination S-Ill and S-Ill' in fig. 4A and 4C may be significantly lower (e.g., at about 0.38 and about 0.20, respectively). As described above, this may be because more than about 50% of the incident beam does not pass through the binary grating 30 or the off-axis binary grating 30 'and is blocked by the binary grating 30 or the off-axis binary grating 30'.
Fig. 5A and 5B are conceptual diagrams for designing a bipolar PSG S-ila and a quadrupole PSGs-Illb, respectively, according to embodiments of the present disclosure. Fig. 5A and 5B combine aspects described with reference to fig. 1, and briefly provide or omit descriptions that have been given with reference to fig. 1 to 4E.
Referring to fig. 5A, when the SI-based inspection apparatus 100 of the present embodiment inspects the inspection object 200 using a line and space pattern, the resulting dipole illumination may improve the resolution of the inspection image. For example, when lines and spaces are alternately arranged in the first direction (x direction) and the line and space pattern is formed in a shape extending in the second direction (y direction) in the inspection object 200, as shown in fig. 5A, the bipolar illumination S-ila in which two illumination poles are separated from each other in the first direction (x direction) can improve the resolution. In addition, when lines and spaces of the line and space pattern are alternately arranged in the second direction (y direction) and have a shape extending in the first direction (x direction) in the inspection object 200, bipolar illumination in which two illumination poles are separated from each other in the second direction (y direction) can improve resolution.
The bipolar illumination S-ila in fig. 5A may be realized by using the PSG130a of the line and space type in fig. 2A. When the first and second portions 130a-1 and 130a-2 of the PSG130a are alternately arranged with substantially the same width in the first direction (x-direction), the pattern period Px of the pattern including the first and second portions 130a-1 and 130a-2 in the first direction (x-direction) and the bipolar illumination S-ila may have a relationship of the following formula 2.
[ equation 2] Px ═ λ/(NA- σ)
Here, the wavelength λ may be an illumination wavelength, NA may be a numerical aperture of the objective lens, and sigma σ may represent a value obtained by multiplying a diameter of the illumination pole by NA. Depending on the measurement configuration on the examination object 200, the optimum angle of incidence for increasing the resolution can be changed. Here, the incident angle may increase as the distance of the illumination pole from the center increases. In addition, as the pitch of the grating decreases, the distance between the two illumination poles may increase. Therefore, in order to improve the resolution, the two illumination poles may be adjusted at appropriate positions in the circle by adjusting the pattern period Px of the PSG130a as long as the two illumination poles do not deviate from the circle corresponding to the NA.
Therefore, after NA, sigma σ, and wavelength λ are determined, the pattern period Px of the PSG130a can be determined by equation 2. Accordingly, when determining the conditions (i.e., NA, sigma σ, and wavelength λ) of the optical system optimized for pattern inspection of the line and space type on the inspection object 200, the PSG130a may be designed accordingly based on equation 2.
Referring to fig. 5B, when the SI-based inspection apparatus 100 of the present embodiment inspects the inspection object 200 using a pattern corresponding to a checkered shape or a grid shape, the resulting quadrupole illumination may improve the resolution of the resulting image. For example, when a pattern arranged in a checkered shape or a grid shape in the first direction (x direction) and the second direction (y direction) is formed on the inspection object 200, as shown in fig. 5B, quadrupole illumination S-Illb in which four illumination poles are separated from each other in both the first direction (x direction) and the second direction (y direction) can improve resolution.
In addition, in the case where the checkered pattern is arranged in two diagonal directions (see D1 coordinates and D2 coordinates in fig. 2D) on the inspection object 200, quadrupole illumination (see S-Illc in fig. 2D) in which four illumination poles are separated from each other in two diagonal directions (D1 and D2) can improve the resolution. Similarly, even when a grid-shaped pattern is formed on the inspection object 200, quadrupole illumination (see S-Illd in fig. 2E) in which four illumination poles are separated from each other in diagonal directions (D1 and D2) can improve resolution.
The quadrupole illumination S-Illb in fig. 5B can be realized by using the square-grid shaped PSG130B in fig. 2C. When the first and second portions 130b-1 and 130b-2 of the PSG130b are alternately arranged with substantially the same width in the first direction (x-direction) and the second direction (y-direction), the pattern period Px in the first direction (x-direction) and the pattern period Py in the second direction (y-direction) of the pattern formed by the first and second portions 130b-1 and 130b-2 of the PSG130b may have a relationship defined by the following equations 3 and 4, respectively.
[ equation 3 ]]Px＝(2)1/2λ/(NA-σ)
[ formula 4 ]]Py＝(2)1/2λ/(NA-σ)
Here, too, the wavelength λ may be an illumination wavelength, NA may be NA of the objective lens, and sigma σ may denote a value obtained by multiplying the diameter of the illumination pole by NA. As described with reference to fig. 5A, by adjusting the pattern periods (Px and Py) of the PSG130a to improve the resolution, the four illumination poles can be located at appropriate positions in a circle without deviating from the circle corresponding to NA. After determining NA, sigma σ, and wavelength λ, the pattern period Px in the first direction (x-direction) and the pattern period Py in the second direction (y-direction) of the PSG130b may be determined by equation 2 and equation 3, respectively. Accordingly, when determining the conditions (e.g., NA, sigma σ, and wavelength λ) of the optical system optimized for the pattern inspection of the checkered shape on the inspection object 200, the PSG130b may be designed accordingly based on formula 3 and formula 4.
Fig. 6A to 6C are conceptual diagrams illustrating an operation principle of a Time Delay Integration (TDI) camera 180 included in the SI-based inspection apparatus 100 of fig. 1 according to an embodiment of the present disclosure, and also illustrate a process of capturing an image by the TDI camera 180 while moving an inspection object 200. Fig. 6A to 6C are described together with fig. 1, and the description that has been given with reference to fig. 1 to 5B is briefly provided or omitted.
Referring to fig. 6A, in the SI-based inspection apparatus 100 of the present embodiment, the TDI camera 180 may be a line scan camera. The differences between a line scan camera and a general area scan camera are briefly described as follows. An area-array scanning camera in which pixels are arranged in a two-dimensional matrix type can scan and transfer only one frame at a time, and can capture an image only in a state in which the area-array scanning camera is stationary. On the other hand, a line scan camera in which pixels are arranged in a line may capture an image while an inspection object and the line scan camera are moved.
In general, line scan cameras may be less expensive than area scan cameras, as line scan cameras may have fewer pixels. Further, the line scan camera may not be limited to being related to the length of the inspection object. However, due to the short exposure time, the sensitivity of the line scan camera may be relatively low. The TDI camera 180 may be configured to overcome the disadvantages of the line scan camera so that it may obtain a clear image of the inspection object 200 by photographing the same portion of the inspection object 200 a plurality of times using a plurality of pixels in a line shape.
A detailed description of the operating principle of the TDI camera 180 is given below.
Assuming that an object corresponding to the inspection object 200 moves in the scanning direction (1 → 2 → 3) as illustrated in fig. 6A, an image of the object can be captured at each stage (St1, St2, and St3) of the TDI image sensor included in the TDI camera 180. Since the same subject needs to be photographed at each gantry (St1, St2, and St3), the subject can be photographed at a subsequent gantry later than the previous gantry depending on the moving speed of the subject. In other words, the moving speed of the FOV of the TDI camera 180 corresponding to each stage may be synchronized with the moving speed of the object. Reference to "latency" in the name of TDI camera 180 may refer to this characteristic of its operation.
In some line scan cameras, a metal halide light source with high illumination may be used to improve sensitivity. However, the TDI camera 180 can obtain high definition while using illumination, for example, with LEDs having lower illumination intensity. Accordingly, the TDI camera 180 may reduce installation and maintenance costs of illumination and may be installed for high speed applications where replacement line scan cameras cannot be installed. In addition, the TDI camera 180 may increase inspection speed by efficient and fast integration of images. Further, in the TDI camera 180, since images are integrated in such a manner that the phases of the respective images are accumulated and averaged, it is possible to eliminate the need for integrating the images based on fourier transform of the phases. Although the operation of the TDI camera 180 may be based on synchronization and alignment with the inspection object 200, the level of synchronization and alignment may not be high and a small number of misalignment defects may not significantly affect the quality of the image.
Referring to fig. 6B, the inspection object 200 may be moved in the scanning direction S by the movement of the stage 170 in the scanning direction S. The grating of the PSG130 implementing SI may be fixed. Accordingly, the pattern "a" formed on the inspection object 200 may move in the scanning direction S in which the inspection object 200 moves, and the relative position of the pattern "a" with respect to the grating may be changed. For reference, fig. 6B shows the relative position of the pattern "a" on the inspection object 200 according to Time, and as indicated by a Time arrow Time, the Time may advance in the direction from the top to the bottom.
Referring to fig. 6C, as the inspection object 200 moves in the scanning direction S as shown in fig. 6B, the TDI camera 180 may photograph the inspection object 200 in synchronization with the movement of the inspection object 200. As the inspection object 200 is moved, the phase of the captured image may be changed accordingly. For example, as shown in fig. 6C, the image at the first position from the top may correspond to a phase of about 0 °, the image at the second position from the top may correspond to a phase of about 132 °, the image at the third position from the top may correspond to a phase of about 265 °, and the last fourth image from the top may correspond to a phase of about 38 °. The TDI camera 180 may integrate the images together by accumulating and averaging the phases of the images. Therefore, in the SI-based inspection apparatus 100, post-image processing of integrating images by taking into account fourier transform and/or inverse fourier transform of the phase of each image may not be required.
Fig. 7 is a conceptual diagram schematically illustrating an SI-based examination apparatus 100a according to an embodiment of the present disclosure. The description that has been given with reference to fig. 1 to 6C is briefly provided or omitted.
Referring to fig. 7, the SI-based inspection apparatus 100a of the present embodiment may further include a magnification control optical system 190. In addition, the SI-based inspection apparatus 100a of the present embodiment may include a rod lens 112, a collimator lens 114, a plurality of filters 116, a diaphragm (or aperture) 165, and first to fourth mirrors M1 to M4.
The magnification control optical system 190 may further include first to fourth mirrors m1 to m 4. The magnification control optical system 190 may change the magnification of the SI-based inspection apparatus 100a by replacing the first mirror m1 to the fourth mirror m4, or by changing the relative positions of the first mirror m1 to the fourth mirror m 4. In fig. 7, xM1 and xM2 written in the magnification control optical system 190 may indicate magnifications by replacement. Although only two magnifications are shown, according to various embodiments, the magnification may be increased by three or more times.
For reference, the plurality of filters 116 may include a spatial filter, a spectral filter, a Neutral Density (ND) filter, and the like. Further, according to an embodiment, the plurality of filters 116 may include polarization filters.
The SI-based inspection apparatus 100a of the present embodiment may further include a PSG130 and a TDI camera 180 to solve problems related to the SI-based inspection apparatus. For example, PSG130 and TDI camera 180 may help solve problems related to the inapplicability of separate optical systems, the use of high illumination sources, slow inspection speed, required implementation of post-image processing, and the corresponding lack of real-time inspection capabilities.
Fig. 8 is a flow chart of an SI-based inspection method according to an embodiment of the present disclosure. Fig. 8 is described together with fig. 1, and the description that has been given with reference to fig. 1 to 7 is briefly provided or omitted.
Referring to fig. 8, the SI-based inspection method of the present embodiment may first generate and emit a light beam from the light source 110 (S110). The beam from the light source 110 may be, for example, an LPP laser beam. However, the light beam from the light source 110 is not limited to the pulsed laser.
Next, the PSG130 may convert the light beam of the light source 110 into SI, and may then emit the SI (S120). For example, as the beam of light source 110 passes through PSG130, the beam of light source 110 may be converted to SI characterized by dipole illumination or quadrupole illumination. The PSG130 may have a structure of: the first regions of the thin layer (see a 1in fig. 3A) and the second regions of the thick layer (see a 2in fig. 3A) are arranged in a line and space shape, a checkered shape, or a grid shape. In addition, since the PSG130 may not include a metal such as chromium, the PSG130 may pass substantially all of the light of the incident light beam. In other words, both the first region a1 and the second region a2 of the PSG130 may include a transparent material, such as quartz without chromium.
The PSG130 may have a form capable of generating an appropriate SI corresponding to the shape of the pattern formed on the inspection object 200. For example, when a line and space shape is included on the inspection object 200, the PSG130 may have a line and space shape as in the PSG130a of fig. 2B. Additionally or alternatively, when a checkered shape or a grid shape is included on the inspection object 200, the PSG130 may also have a checkered shape or a grid shape similar to the PSGs (130b, 130C, and 130d) in fig. 2C to 2E. To improve resolution, the pitch of the pattern formed by the first and second regions a1 and a2 of the PSG130 may be designed based on the conditions of the optical system in the inspection apparatus 100.
Next, the SI from the PSG130 may be incident on the inspection object 200 through the beam splitter 140, and a reflected light beam from the inspection object 200 may be output toward the TDI camera 180 through the beam splitter 140 (S130). For example, the beam splitter 140 may transmit or reflect SI incident from the PSG130 to be incident on the inspection object 200, and may reflect or transmit a reflected beam from the inspection object 200 toward the TDI camera 180.
The TDI camera 180 may capture an image of the inspection object 200 by detecting a reflected light beam emitted from the beam splitter 140 (S140). The capturing of the image of the inspection object 200 by the TDI camera 180 may be performed in synchronization with the movement of the inspection object 200 in the scanning direction S by the stage 170 and the movement of the FOV of the TDI camera 180. As described above, the TDI camera 180 may integrate multiple images of the inspection object 200 by accumulating and averaging the phases of the images. Therefore, the SI-based inspection method of the present embodiment can avoid the necessity of a post-image processing process using fourier transform and/or inverse fourier transform based on the phase of each image.
Fig. 9 is a flowchart of a method of manufacturing a semiconductor device including an SI-based inspection method according to an embodiment of the present disclosure. Fig. 9 is described with reference to the above-described components (e.g., with reference to fig. 1). The description already given with reference to fig. 8 is briefly provided or omitted.
Referring to fig. 9, the semiconductor device manufacturing method of the present embodiment may proceed from operation S110 of generating and emitting a light beam to operation S140 of capturing an image of an inspection object 200. The contents of the above operation are as described with reference to fig. 8.
Next, it is determined whether there is a defect in the inspection object 200 (S150). Whether there is a defect in the inspection object 200 may be determined based on an image captured by the TDI camera 180. For example, whether there is a defect in the inspection object 200 may be determined by determining whether there is a fine particle or a scratch on the inspection object based on an image captured by the TDI camera 180. However, as noted above, not all particles or scratches may be identified as defects. For example, only particles or scratches with dimensions that are out of tolerance (i.e., larger than a threshold size) may be identified as defects.
When a defect is not identified in operation S150 (no), a semiconductor process may be performed on the inspection object 200 (S160). For example, when the inspection object 200 is a wafer, semiconductor processing for the wafer may be performed. Semiconductor processing for wafers may include various sub-processes. For example, semiconductor processing for a wafer may include deposition processing, etching processing, ionization processing, cleaning processing, and the like. Semiconductor processing for wafers may result in integrated circuits and wiring required to form corresponding semiconductor devices. Semiconductor processing for wafers may also include test processing on semiconductor devices at the wafer level.
After the semiconductor chips in the wafer are completed by semiconductor processing for the wafer, the wafer may be individualized into individual semiconductor chips. Singulation into individual semiconductor chips may be achieved by a sawing process using a blade or a laser. Next, a packaging process may be performed on the semiconductor chip. The packaging process may refer to a process in which a semiconductor chip is mounted on a Printed Circuit Board (PCB) and sealed with a sealing material. The packaging process may include forming a stack package by stacking a plurality of semiconductor chips on a PCB, or forming a Package On Package (POP) structure by stacking individual stack packages on the stack package. The semiconductor device or the semiconductor package may be completed by a packaging process of the semiconductor chip. The test process may be performed on the semiconductor package after the packaging process.
When it is determined that there is a defect in the inspection object 200 during operation S150 (yes), the type and cause of the defect may be analyzed (S170). According to the embodiments of the present disclosure, a process of removing a defect or discarding a corresponding inspection object by cleaning may be performed according to the type of the defect.
According to an embodiment of the present disclosure, an SI-based inspection apparatus may reduce loss of light by generating SI through a PSG and capturing an image of an inspection object using the SI, while improving resolution of an inspection image. Therefore, the SI-based inspection apparatus can accurately inspect the inspection object for defects using a relatively low-illumination light source while still obtaining a high-resolution image of the inspection object.
In addition, the SI-based inspection apparatus described herein can perform high-speed capturing of an inspection object by capturing an image of the inspection object using a TDI camera, and can inspect the inspection object at high speed in real time because a post-image processing operation of integrating the image in consideration of the phase of the image is not necessary.
Further, embodiments of the SI-based inspection apparatus of the present disclosure can be easily applied to a BF system having a separation optical system structure in which an illumination optical system and an imaging optical system are separated by arranging a PSG only on the illumination optical system.
While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims. Accordingly, the true scope of the inventive concept should be determined by the following claims.
