阅读说明：本技术 曝光装置、用于控制曝光装置的方法、以及物品制造方法 (Exposure apparatus, method for controlling exposure apparatus, and article manufacturing method ) 是由 加贺明久 水元一史 于 2020-01-03 设计创作，主要内容包括：本发明公开了曝光装置、用于控制曝光装置的方法、以及物品制造方法。曝光装置包括被配置为将掩模的图案投影到基板上的投影光学系统、被配置为保持和移动所述基板的基板台架、以及被配置为控制由所述基板台架保持的基板的曝光的控制器,其中所述控制器基于远心度信息和高度信息来获得投影到所述基板上的图案的图像相对于所述掩模的图案的偏离量,并且基于获得的偏离量来校正所述图像的偏离以使所述基板曝光,所述远心度信息是关于所述投影光学系统的各个图像高度的远心度的信息,所述高度信息是关于所述基板的表面的高度的信息。(The invention discloses an exposure apparatus, a method for controlling the exposure apparatus, and an article manufacturing method. An exposure apparatus includes a projection optical system configured to project a pattern of a mask onto a substrate, a substrate stage configured to hold and move the substrate, and a controller configured to control exposure of the substrate held by the substrate stage, wherein the controller obtains a deviation amount of an image of the pattern projected onto the substrate from the pattern of the mask based on telecentricity information, which is information on telecentricity of respective image heights of the projection optical system, and height information, which is information on a height of a surface of the substrate, and corrects deviation of the image based on the obtained deviation amount to expose the substrate.)

1. An exposure apparatus operable to expose a substrate, the apparatus comprising:

a projection optical system configured to project a pattern of a mask onto the substrate;

a substrate stage configured to hold and move the substrate; and

a controller configured to control exposure of the substrate held by the substrate stage, wherein

The controller obtains a deviation amount of an image of a pattern projected onto the substrate from a pattern of the mask based on telecentricity information and height information, the telecentricity information being information on telecentricity of each image height of the projection optical system, and corrects the deviation of the image based on the obtained deviation amount to expose the substrate.

2. The exposure apparatus according to claim 1, wherein

In the control unit, the controller is provided with a plurality of control circuits,

obtaining a difference between an optimum focus position in an optical axis direction of the projection optical system and a height of the surface of the substrate obtained from the height information as a defocus amount, and

the amount of deviation is obtained based on the defocus amount and telecentricity information.

3. The exposure apparatus according to claim 1, wherein a resolution of a surface height of the substrate included in the height information is higher than a resolution of a focus drive of the substrate stage.

4. The exposure apparatus according to claim 1, comprising

A height measuring device for measuring a surface height of the substrate, wherein

The controller obtains the height information from a result of measurement using the height measuring device.

5. The exposure apparatus according to claim 1, wherein

The controller obtains the height information based on design information of the substrate.

6. The exposure apparatus according to claim 1, comprising

A telecentricity measuring device for measuring the telecentricity at each image height of the projection optical system, and

the controller obtains the telecentricity information from a result of measurement using the telecentricity measuring apparatus.

7. The exposure apparatus according to claim 1, wherein the controller obtains the telecentricity information based on design information of the projection optical system.

8. The exposure apparatus according to claim 1, comprising

A mask stage configured to hold the mask,

an illumination optical system configured to illuminate the mask while the mask is held by a mask stage, wherein

The controller corrects the deviation of the image during exposure of the shot region of the substrate by performing at least one of: driving of the substrate stage, driving of the mask stage, driving of an optical element of the projection optical system, driving of an optical element of the illumination optical system, and adjusting a pulse oscillation frequency of a light source of the illumination optical system.

9. A method for controlling an exposure apparatus that projects a pattern of a mask onto a substrate through a projection optical system and exposes the substrate, the method comprising:

obtaining telecentricity information, which is information on the telecentricity of each image height of the projection optical system;

obtaining height information, which is information on a height of a surface of the substrate;

obtaining a deviation amount of an image of the pattern projected onto the substrate from the pattern of the mask based on the telecentricity information and the height information; and

correcting the deviation of the image based on the obtained deviation amount to expose the substrate.

10. A method of manufacturing an article comprising

Exposing a substrate using the exposure apparatus according to any one of claims 1 to 8;

developing the exposed substrate; and

an article is fabricated from the developed substrate.

Technical Field

The invention relates to an exposure apparatus, a method for controlling the exposure apparatus, and an article manufacturing method.

Background

In an exposure apparatus for transferring a pattern of an original plate (mask or reticle) onto a substrate, various corrections are performed to deformation, distortion, and the like of shot (shot) regions of the substrate. These corrections are generally performed independently of the control (correction) of the focus position. This is because the projection optical system of the exposure apparatus is telecentric, and even if the focus position is changed, the magnification factor deviation, the rotational deviation, and the distortion of the shot region are not changed. However, the projection optical system of the exposure apparatus is not strictly telecentric, and telecentricity (telecentricity) exists due to the influence of aberration in the projection optical system.

Japanese patent laid-open No.2017-90778 discloses a technique for improving the overlay accuracy by correcting the defocus amount generated by the telecentricity.

With the recent miniaturization of patterns and the increase in the number of processes performed on thick film photoresists, it has become impossible to ignore the influence of distortion according to the amount of defocus, variation in the projection magnification factor, or image shift caused by the fact that the degree of telecentricity is not zero. Therefore, there is a need to correct image deviation with higher accuracy.

Disclosure of Invention

The present invention provides a technique advantageous for improving the accuracy of image deviation correction, for example.

The present invention provides, in one aspect thereof, an exposure apparatus operable to expose a substrate, the apparatus comprising: a projection optical system configured to project a pattern of a mask onto the substrate; a substrate stage configured to hold and move the substrate; and a controller configured to control exposure of a substrate held by the substrate stage, wherein the controller obtains an amount of deviation of an image of a pattern projected onto the substrate from a pattern of the mask based on telecentricity information and height information, the telecentricity information being information on telecentricity of each image height of the projection optical system, and corrects deviation of the image based on the obtained amount of deviation to expose the substrate.

The present invention in its second aspect provides a method for controlling an exposure apparatus that projects a pattern of a mask onto a substrate through a projection optical system and exposes the substrate, the method comprising: obtaining telecentricity information, which is information on the telecentricity of each image height of the projection optical system; obtaining height information, which is information on a height of a surface of the substrate; obtaining a deviation amount of an image of the pattern projected onto the substrate from the pattern of the mask based on the telecentricity information and the height information; and correcting the deviation of the image based on the obtained deviation amount to expose the substrate.

The present invention provides, in a third aspect thereof, a method of manufacturing an article, comprising: exposing the substrate using the exposure apparatus defined in the first aspect; developing the exposed substrate; and fabricating an article from the developed substrate.

Other features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

Drawings

Fig. 1 is a configuration diagram of an exposure apparatus according to an embodiment.

Fig. 2 is a diagram illustrating an example of positional deviation due to defocus caused by a thick film photoresist.

Fig. 3 is a diagram illustrating an example of a positional deviation due to defocusing caused by a thick film photoresist and a step (step) type underlayer.

Fig. 4 is a flowchart illustrating a method for controlling an exposure apparatus according to an embodiment.

Fig. 5 is a schematic diagram illustrating the level difference of the bottom layer in the shot region.

Fig. 6 is a diagram illustrating an image deviation including high-order components due to a step in the underlayer caused by telecentricity.

Fig. 7 is a diagram illustrating an example of a pattern for correcting a high-order component in a shot region.

Detailed Description

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The embodiments described herein are to be considered as examples only and are not intended to limit the scope of the patent claims. Although a plurality of features are described in the embodiments, not all of the plurality of features are essential to the present invention, and the plurality of features may be freely combined. Further, in the drawings, the same reference numerals are assigned to the same or similar components, and a repetitive description thereof is omitted.

Fig. 1 is a diagram illustrating a configuration example of an exposure apparatus 100 according to an embodiment. In the present specification, directions are illustrated in an XYZ coordinate system in which a horizontal plane is an XY plane. The substrate 5 is placed on the substrate stage 6 such that the surface thereof is parallel to a horizontal plane (XY plane), and the optical axis of the projection optical system 4 is parallel to a Z axis orthogonal to the XY plane.

The exposure apparatus 100 includes an illumination optical system 1, a mask stage 3 for holding and moving a mask 2 as an original, a projection optical system 4, a substrate stage 6 for holding and moving a substrate 5, and a controller 7. The light beam from the illumination optical system 1 passes through a mask 2 held by a mask stage 3, and enters a projection optical system 4. A pattern to be transferred to the substrate 5 is formed on the mask 2. Since the mask 2 and the substrate 5 are in an optically conjugate positional relationship, the pattern of the mask 2 is projected onto the substrate 5 held by the substrate stage 6 via the projection optical system 4, whereby the pattern is transferred onto the substrate 5. The controller 7 includes a CPU 7a, a memory 7b, and the like, and controls the entire exposure apparatus 100. The controller 7 controls the operation of the exposure apparatus 100, that is, the exposure process for exposing the substrate 5 (such as, for example, the calculation required to implement the exposure method in the present embodiment) by comprehensively controlling each unit of the exposure apparatus 100.

The exposure apparatus 100 may include a height measurement device 8 (focus detection system) for measuring the height of the surface of the substrate. In the height measuring device 8, light emitted from the light projector 81 is reflected by the mirror 82 and projected onto the substrate 5 from an oblique direction. The light projected onto the substrate 5 is reflected by the substrate surface and reaches the light receiver 84 via the mirror 83 formed on the opposite side. The light receiver 84 includes a photoelectric converter such as a CCD, and the controller 7 processes signals obtained by the photoelectric converter to detect the position in the height direction (Z direction) of the surface of the substrate 5.

The position in the optical axis direction of the projection optical system 4 at which the optimum CD (or image quality) is obtained by exposure is defined as the best focus position. The optimum focus position is adjusted in advance as the origin of the focus detection system, and is information held for each apparatus. In the embodiment, the information of the best focus position is stored in the memory 7b of the controller 7. In the exposure apparatus 100, the focal position of the projection optical system 4 may change due to changes in atmospheric pressure, ambient temperature, and the like due to heat generation of the exposure light. Therefore, it is necessary to regularly calibrate the best focus position before exposing the substrate. Generally, the influence of the above-mentioned variation factors is predicted in advance, and the best focus position is calibrated accordingly, but for more accurate calibration, it is necessary to actually measure the best focus position of the projection optical system and then perform calibration. The best focus position may be defined, for example, at a position where the substrate stage 6 is sequentially driven in the Z direction to maximize the signal level obtained by the height measuring device 8.

The height measuring device 8 may also be used to obtain a height distribution of the surface of the substrate 5. The height measuring device 8 irradiates measuring light onto the substrate 5, and the measuring light reflected by the substrate 5 is received by the light receiver 84. The measurement light received by the light receiver 84 is photoelectrically converted and sent to the controller 7. The controller 7 performs signal processing on this, and measures the focus position (Z-direction position) of the substrate 5. By repeatedly moving the substrate 5 in the X and Y directions, information (height information) on the height of the surface of the substrate 5 is obtained. As explained with reference to fig. 3, in the embodiment, the resolution of the height of the surface of the substrate included in the height information is higher than the resolution of the focus drive of the substrate stage 6. If a photoresist is coated on the substrate, it may be necessary to consider an error of the measurement sensor due to the thickness of the photoresist.

The exposure apparatus 100 may include a telecentricity measuring device 15, and the telecentricity measuring device 15 measures the telecentricity at each image height of the projection optical system 4. The chief ray passing through the center of the pupil being parallel to the optical axis of the optical system is said to be "the optical system is telecentric". The optical system is telecentric ensures that even if the object is defocused, the image is only blurred and does not become laterally offset. Although the optical system in the exposure apparatus is designed to be as telecentric as possible, it is extremely difficult to prevent the occurrence of a tilt in the principal ray at each image height due to a manufacturing error or the like. Hereinafter, the tilt in the principal ray of the illumination optical system 1 and the projection optical system 4 will be referred to as "telecentricity".

In practice, it is difficult to accurately null the telecentricity, but the telecentricity can be kept small. Furthermore, telecentricity is not uniform over the entire image height, but there is a different error for each image height. Therefore, when the substrate is defocused from the best focus position of the projection optical system, the image is displaced (shifted) in a direction orthogonal to the optical axis of the projection optical system according to the defocus amount. As a result, the projection magnification of the projection optical system for the image changes, or distortion (distortion aberration) as optical aberration changes. Here, the amount of shift and the projection magnification are linearly changed with respect to the defocus amount of the substrate with respect to the best focus position, and the distortion is nonlinearly changed.

Conventionally, since the defocus amount falls within the depth of the focal point of the projection optical system, adverse effects on the imaging characteristics due to the remaining telecentricity are not so great a problem. However, with the recent miniaturization of patterns and the increase in the number of processes performed on thick film photoresists, it has become impossible to ignore the influence of distortion according to the amount of defocus, variation in the projection magnification factor, or image shift caused by the fact that the degree of telecentricity is not zero. In particular, the influence on telecentricity is large due to the thick film photoresist. In the exposure apparatus, the telecentricity may be considered to be approximately several milliradians to several tens of milliradians in value. For example, if the defocus amount is 100 nm and the telecentricity is 10 mrad, the image shift amount is 1 nm. Due to the miniaturization of current semiconductor devices, a deviation amount of 1 nm may be a problem with respect to the requirement of high-precision overlay.

Fig. 2 is a diagram illustrating an example of positional deviation due to defocus caused by a thick film photoresist. When a thick film photoresist is exposed, image deviation (positional deviation) occurs due to the photoresist thickness and telecentricity. In the case of typical photoresist thicknesses, the image deviation is very small, which is not a problem. However, thick film photoresists are expected to be as thick as 10 microns, in which case on average ± 5 microns of defocus may occur. Therefore, according to this defocus amount, a non-negligible image deviation may occur. Therefore, when a thick film resist is used, a countermeasure against image deviation corresponding to the defocus amount is required.

In addition, in the process using the thick film photoresist, a multilayer structure is assumed, and as shown in fig. 3, a case where the underlayer has a stepwise shape is also assumed. Currently, it is difficult to make the best focus position follow such a level difference of the bottom layer due to insufficient resolution of focus driving. Therefore, the defocus amount also changes according to the shape of the underlayer, and the influence of telecentricity changes.

In the embodiment, the controller 7 obtains the amount of deviation of the image of the pattern projected onto the substrate (image deviation amount) with respect to the pattern of the mask based on the information related to the telecentricity of each image height of the projection optical system (hereinafter referred to as "telecentricity information") and the information related to the height of the surface of the substrate (hereinafter referred to as "height information"). As described above, the height information can be obtained from the result of measurement using the height measuring device 8. Alternatively, the height information may be obtained by inputting external data. Alternatively, the height information may be stored in the memory 7b in advance, and the controller 7 may obtain the height information by reading the height information from the memory 7 b. Alternatively, the board design information (process design information) may be stored in the memory 7b in advance, and the controller 7 may obtain the height information based on the design information. The telecentricity information can be obtained from the result of telecentricity measurement using the telecentricity measuring device 15. For measurement of telecentricity, for example, there is a method of measuring a deviation amount at each image height at each of an optimal focus position and a defocus position, and obtaining telecentricity from a relationship between the defocus amount and the deviation amount. The telecentricity can be measured using a sensor, and it is not necessary to form a mark on the substrate in advance. Alternatively, instead of performing the measurement, the telecentricity information may be obtained by the user inputting telecentricity information or the like. Alternatively, the telecentricity information may be stored in the memory 7b in advance, and the controller 7 may obtain the telecentricity information by reading it from the memory 7 b. Alternatively, design information of the projection optical system 4 may be stored in the memory 7b in advance, and the controller 7 may obtain telecentricity information based on the design information.

In the embodiment, the controller 7 corrects the influence of telecentricity according to the shape of the underlayer during the process for exposing the shot region (hereinafter, also simply referred to as "shot") of the substrate 5. In the exposure process, aberrations generated by thermal deformation and optical characteristics of the projection optical system 4 are also corrected. Aberration correction can be achieved by driving the optical elements of the projection optical system 4, driving the optical elements of the illumination optical system 1, adjusting the laser frequency (light source), driving the mask stage 3, driving the substrate stage 6, and the like. Even for high-order components, aberration correction can be performed in real time within the shot region. Image deviations caused by telecentricity can also be considered as aberrations. Therefore, the controller 7 performs, for example, at least one of the following in order to reduce the obtained image deviation amount.

(a) The substrate stage 6 is driven.

(b) The mask stage 3 is driven.

(c) The optical elements of the projection optical system 4 are driven.

(d) The optical elements of the illumination optical system 1 are driven.

(e) The pulse oscillation frequency of the light source of the illumination optical system 1 is adjusted.

A flowchart of a control method of the exposure apparatus 100 according to the present embodiment is illustrated in fig. 4. In step S401, the controller 7 obtains telecentricity information in the above-described manner. In step S402, the controller 7 obtains height information. The height information can be obtained in the above-described manner. Note that here, the defocus amount may be estimated from step information on the design of the substrate using the process design information. It is more effective to combine the relief information of the substrate plane according to the detection of the positional deviation by the oblique light incidence as described above. In the present embodiment, the height of the substrate surface refers to the defocus amount per image height generated by the shape of the underlayer. Alternatively, the height of the substrate surface may be the height difference from the plane of best focus generated by the shape of the underlayer.

In addition, for example, as shown in fig. 5, when there is a step in the ground layer in one shot, the image deviation appears as a high-order component including a transverse trapezoidal shape, a longitudinal trapezoidal shape, and a longitudinal barrel shape, as shown in fig. 6. In the embodiment, the image deviation due to the step in the underlayer in one shot can be understood as a high-order component of the aberration, and the image deviation in shot can be corrected by performing the shot middle-high order correction in real time during the exposure process. As a basic correction pattern for correcting a high-order component in the shot, for example, as shown in fig. 7, there are correction patterns of 0-order offset, magnification factor, and first-order, second-order, third-order, or fourth-order skew. The correction is performed by appropriately combining these correction patterns. The offset may be corrected by driving the substrate stage and/or the mask stage. Magnification factor, skew, and higher order components can be corrected by driving the optical elements of the optical system. However, these are merely examples. For example, a second-order or higher component, a third-order or higher component, or the like may be used as the higher-order component.

In step S403, the controller 7 calculates an image deviation amount generated by the telecentricity. At the time of exposure processing, the mark on the substrate surface is detected by a focus detection system so that correction is performed in real time, and the stage is driven to a focus position where imaging performance is within an allowable range, thereby maintaining an optimum focus position. In step S403, the controller 7 calculates an image deviation amount caused by the telecentricity of each image height by using the following information.

(1) The telecentricity information (telecentricity per image height) obtained in step S401,

(2) height information (height distribution (defocus amount) of the substrate surface) obtained in step S402, and

(3) the best focus position in the memory 7b is maintained.

If the height of the surface of the substrate is H, the best focus position is BF, and the defocus amount is DF, the defocus amount DF is represented by:

DF＝BF-H

when the telecentricity [ rad ] is θ and the image deviation amount is S, the image deviation amount S is represented by the following equation:

S＝DF·cosθ

the telecentricity defined here is a unit [ nm/um ] representing the amount of change [ nm ] in telecentricity at 1[ um ] defocus.

In step S404, the controller 7 corrects the image deviation amount obtained in step S403 as a high-order component in shot-by-shot processing during exposure processing. Specifically, the controller 7 performs at least one of: the substrate stage 6 is driven, the mask stage 3 is driven, the projection optical system 4 is driven, the illumination optical system 1 is driven, and the pulse oscillation frequency of the light source of the illumination optical system 1 is adjusted so as to reduce the amount of deviation of the obtained image.

By the above processing, it is possible to correct the image deviation caused by telecentricity at the time of exposure based on the height distribution and telecentricity of the underlayer per shot.

< example of article production method >

The article manufacturing method according to the embodiment of the present invention is suitable for, for example, manufacturing an article such as a microdevice (such as a semiconductor device) or an element having a microstructure. The article manufacturing method of the present embodiment includes a step of forming a latent image pattern on a photosensitive agent applied to a substrate by using the above-mentioned exposure device (a step of exposing the substrate), and a step of developing the substrate on which the latent image pattern is formed by such a step. In addition, such fabrication methods include other well-known processes (such as oxidation, deposition, evaporation, doping, planarization, etching, photoresist stripping, dicing, bonding, and packaging). The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article, as compared with the conventional method.

OTHER EMBODIMENTS

Embodiments of the present invention may also be implemented by reading out and executing computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a 'non-transitory computer-readable storage medium') to perform the above-described implementationsThe functions of one or more of the embodiments and/or a computer of a system or apparatus including one or more circuits (e.g., an Application Specific Integrated Circuit (ASIC)) for performing the functions of one or more of the above-described embodiments, as well as methods performed by a computer of a system or apparatus by, for example, reading and executing computer executable instructions from a storage medium to perform the functions of one or more of the above-described embodiments and/or controlling one or more circuits to perform the functions of one or more of the above-described embodiments. The computer may include one or more processors (e.g., Central Processing Unit (CPU), Micro Processing Unit (MPU)) and may include a separate computer or a network of separate processors to read out and execute computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, a hard disk, Random Access Memory (RAM), Read Only Memory (ROM), storage devices for a distributed computing system, an optical disk such as a Compact Disk (CD), Digital Versatile Disk (DVD), or Blu-ray disk (BD)^TM) One or more of a flash memory device, a memory card, etc.

The embodiments of the present invention can also be realized by a method in which software (programs) that perform the functions of the above-described embodiments are supplied to a system or an apparatus through a network or various storage media, and a computer or a Central Processing Unit (CPU), a Micro Processing Unit (MPU) of the system or the apparatus reads out and executes the methods of the programs.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.