阅读说明：本技术 测量系统与衍射光的方法 (Measurement system and method for diffracting light ) 是由 傅晋欣 王诣斐 伊恩·马修·麦克马金 罗格·梅耶·蒂默曼·蒂杰森 卢多维克·戈代 约瑟夫· 于 2020-04-06 设计创作，主要内容包括：本公开内容的实施方式涉及测量系统和用于衍射光的方法。该测量系统包括台架、光学臂和一个或多个检测器臂。衍射光的方法包括提供一种衍射光的方法,该方法包括以固定的光束角θ-(0)和最大定向角φ-(max)将具有波长λ-(laser)的光束投射到第一基板的第一区域；获得位移角Δθ；确定目标最大光束角θ-(t-max),其中θ-(t-max)＝θ-(0)+Δθ,并通过经修改的光栅间距公式P-(t-grating)＝λ-(laser)/(sinθ-(t-max)+sinθ-(0))确定测试光栅间距P-(t-grating)。该测量系统和方法允许测量光学元件的区域的非均匀特性,例如光栅间距和光栅取向。(Embodiments of the present disclosure relate to measurement systems and methods for diffracting light. The measurement system includes a gantry, an optics arm, and one or more detector arms. The method of diffracting light includes providing a method of diffracting light, the method including at a fixed beam angle θ 0 And a maximum orientation angle phi max Will have a wavelength λ laser Is projected to the first substrateAn area; obtaining a displacement angle delta theta; determining a target maximum beam angle θ t‑max Wherein theta t‑max ＝θ 0 + Δ θ, and by a modified grating pitch formula P t‑grating ＝λ laser /(sinθ t‑max +sinθ 0 ) Determining a test grating pitch P t‑grating . The measurement system and method allow for measurement of non-uniform characteristics of an area of an optical element, such as grating pitch and grating orientation.)

1. A measurement system, comprising:

a stage having a substrate support surface, the stage coupled to a stage actuator configured to move the stage in a scan path and rotate the stage about an axis;

an optical arm coupled to an arm actuator configured to scan the optical arm and rotate the optical arm about the axis, the optical arm having:

a laser adjacent to a beam splitter located in an optical path adjacent to a light detector, the laser operable to project a plurality of light beams to the beam splitter, the plurality of light beams deflected along the optical path at a beam angle θ to the stage; and

a detector arm comprising:

a detector actuator configured to scan the detector arm and rotate the detector arm about the axis;

a first focusing lens; and

a detector.

2. The measurement system of claim 1, wherein the optics arm further comprises:

a white light source operable to project white light at the beam angle θ along the optical path to the stage; and

a spectrometer coupled to the optical detector to determine a wavelength of the light beam deflected to the optical detector.

3. The measurement system of claim 1, wherein the optics arm further comprises:

a polarizer located between the laser and the beam splitter; and

a quarter wave plate located adjacent to the beam splitter on the optical path.

4. The measurement system of claim 1, wherein the beam of light is reflected to an initial R₀Light beam, the initial R₀A light beam is incident on the first focusing lens at a first point of incidence, wherein the first point of incidence is separated from the optical center of the first focusing lens by a first incremental distance Δ₁。

5. The measurement system of claim 4, wherein the detector has a resolution of less than about Δ₁。

6. The measurement system of claim 4, further comprising a second focusing lens and a third focusing lens.

7. The measurement system of claim 6, wherein the initial R₀The light beam is focused to a first R by the first focusing lens₀Light beam, the first R₀The light beam is focused to a second R by the second focusing lens₀A light beam, and the second R₀The light beam is focused to a third R by the third focusing lens₀A light beam.

8. The measurement system of claim 7, wherein:

the third R₀The light beam is incident on said third focusing lens at a third point of incidence,

the third point of incidence is separated from the optical center of the third focusing lens by a second incremental distance Δ₂And is and

the second incremental distance Δ₂Greater than the first incremental distance Δ₁。

9. A measurement system, comprising:

a stage having a substrate support surface, the stage coupled to a stage actuator configured to move the stage in a scan path and rotate the stage about an axis;

an optical arm coupled to an arm actuator configured to scan the optical arm and rotate the optical arm about the axis, the optical arm comprising:

a laser positioned adjacent to a beam splitter disposed in an optical path adjacent to a light detector, the laser operable to project a plurality of light beams onto the beam splitter, the plurality of light beams deflected along the optical path at a beam angle θ to the stage; and

a primary detector arm and a secondary detector arm, each of the primary and secondary detector arms comprising:

a detector actuator configured to scan the primary detector arm or the secondary detector arm;

a first focusing lens; and

a detector.

10. The measurement system of claim 9, wherein the secondary detector arm is disposed behind the optical arm.

11. The measurement system of claim 10, wherein:

the light beam is reflected to the initial R₀Light beam, the initial R₀A light beam is incident on the first focusing lens of the main detector arm at the first point of incidence of the main detector arm,

the first point of incidence of the main detector arm is separated from the optical center of the first focusing lens of the main detector arm by a first incremental distance Δ₁，

The light beam is reflected from a workpiece placed on the stage to a reflected R₁Light beam, said reflected R₁The light beam is incident on a first focusing lens of the secondary detector arm at a first point of incidence of the secondary detector arm, and

the first point of incidence of the secondary detector arm is separated from the optical center of the first focusing lens of the secondary detector arm by a third incremental distance Δ₃。

12. A method of diffracting light, comprising the steps of:

at a wavelength of λ_laserAt a fixed beam angle theta₀And a maximum orientation angle phi_maxProjecting to a first area of a first substrate;

obtaining a displacement angle delta theta;

determining a target maximum beam angle θ_t-maxWherein, theta_t-max＝θ₀+ Δ θ; and

by modified grating pitch formula P_t-grating＝λ_laser/(sinθ_t-max+sinθ₀) Determining a test grating pitch P_t-grating。

13. The method of claim 12, wherein the steps of projecting the beam, obtaining the displacement angle Δ θ, determining the target maximum beam angle θ are repeated for subsequent regions_t-maxAnd determining the test grating pitch P_t-gratingThe step (2).

14. The method of claim 12, wherein the step of obtaining the displacement angle Δ θ comprises the steps of:

reflecting the plurality of light beams off the first region and to an initial R₀Light beam, so that the initial R₀The light beam is incident on the focusing lens at a first point of incidence spaced apart from the optical center of the focusing lens by a first incremental distance Δ₁(ii) a And

according to the first incremental distance delta₁Determining a first angle Δ θ₁。

15. The method of claim 14, wherein the first angle Δ θ is determined₁Comprises using the formula Δ₁＝f₁*tan(Δθ₁) Wherein f is₁Is the focal length of the focusing lens.

Technical Field

Embodiments of the present disclosure relate to devices and methods, and more particularly, to measurement systems and methods of diffracting light.

Background

Virtual reality is generally considered a computer-generated simulated environment in which a user has an apparent physical presence. The virtual reality experience may be generated in 3D and viewed using a Head Mounted Display (HMD), such as glasses or other wearable display devices having a myopic display panel as a lens to display a virtual reality environment that may replace the actual environment.

However, augmented reality technology provides an experience that allows the user to still see the surrounding environment through the display lens of glasses or other HMD devices, while also seeing virtual objects that are generated for display and displayed as part of the environment. Augmented reality may include any type of input, such as audio and tactile input, as well as virtual images, graphics, and imagery, which may augment or augment the environment experienced by the user. To obtain an augmented reality experience, the virtual image is superimposed in the surrounding environment and the superimposition is performed by the optical element.

One disadvantage of the art is that the manufactured optical elements tend to have non-uniform characteristics, such as grating pitch and grating orientation. In addition, the deposited optical element may inherit non-uniformities of its substrate, such as local warping or deformation of the substrate. In addition, if the deposition is performed on a substrate that is disposed on a support surface that is not flat (e.g., there are defects or particles on the support surface), the substrate may be tilted and the deposited optical element may also inherit these deformations.

Accordingly, there is a need in the art for an apparatus and method for detecting non-uniformities in optical elements.

Disclosure of Invention

In one embodiment, a measurement system is provided that includes a gantry; an optical arm coupled to an arm actuator, the arm actuator configured to scan the optical arm and rotate the optical arm about an axis, and a detector arm. The stage has a substrate support surface. The gantry is coupled to a gantry actuator that is configured to move the gantry in a scan path and rotate the gantry about an axis. The optical arm includes a laser positioned adjacent to a beam splitter positioned in the optical path adjacent to an optical detector, the laser operable to project a beam of light onto the beam splitter, the beam of light deflected along the optical path at a beam angle θ to the stage. The detector arm includes a detector actuator configured to scan the detector arm and to surround the axial detector arm, a first focusing lens, and a detector.

In another embodiment, a measurement system is provided, comprising a gantry; an optical arm connected to the arm actuator; an optical detector configured to scan the optical arm and rotate the optical arm about an axis; a primary detector arm and a secondary detector arm. The stage has a substrate support surface. The gantry is coupled to a gantry actuator that is configured to move the gantry in the scan path and rotate the gantry about an axis. The optical arm includes a laser positioned adjacent to a beam splitter positioned in an optical path adjacent to the optical detector, the laser operable to project a beam of light onto the beam splitter, the beam of light deflected along the optical path at a beam angle θ to the stage. Each detector arm includes a detector actuator configured to scan the detector arm, a first focusing lens, and a detector.

In yet another embodiment, a method of diffracting light is provided, the method comprising at a fixed beam angle θ₀And a maximum orientation angle phi_maxWill have a wavelength λ_laserIs projected to a first area of a first substrate; obtaining a displacement angle delta theta; determining a target maximum beam angle θ_t-maxWherein theta_t-max＝θ₀+ Δ θ; and by the modified grating pitch formula P_t-grating＝λ_laser/(sinθ_t-max+sinθ₀) Determining a test grating pitch P_t-grating。

The measurement system and method measure local non-uniformities, such as grating pitch and grating orientation, in the area of the optical element. The local non-uniformity values can be used to evaluate the performance of the optical element.

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of the scope of the disclosure, for the description may admit to other equally effective embodiments.

Fig. 1A-1C show schematic views of a configuration of a measurement system according to some embodiments.

Fig. 2A-2C show schematic views of a beam position detector according to some embodiments.

Fig. 3 shows a schematic cross-sectional view of a first region according to an embodiment.

Fig. 4A-4D show schematic views of a measurement system including one or more detector arms, according to some embodiments.

FIG. 5 is a flowchart of the method operations for diffracting light, according to one embodiment.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

Detailed Description

Embodiments of the present disclosure relate to measurement systems and methods for measuring local non-uniformities of optical elements. The measurement system includes a gantry, an optical arm, and one or more detector arms including one or more focusing lenses. Light projected from the optical arm is reflected from a substrate placed on the stage, and light reflected from the substrate surface may be incident on the detector. The deflection from the optical center of the focusing lens is used to determine the local inhomogeneity of the optical element. The method of diffracting light includes measuring a scattered light beam from a surface of a substrate, and obtaining a local distortion from the measured value. Embodiments disclosed herein may be particularly useful for (but not limited to) measuring local uniformity in an optical system.

As used herein, the term "about" refers to +/-10% from the nominal value. It is to be understood that such variations may be included in any of the values provided herein.

FIG. 1A shows a schematic view of a first configuration 100A of a measurement system 101 according to one embodiment. As shown, the measurement system 101 includes a gantry 102, an optical arm 104A, and one or more detector arms 150. The measurement system 101 is configured to diffract light generated by the optics arm 104. Light generated by the optics arm 104 is directed toward a substrate disposed above the stage 102, and diffracted light is incident on the one or more detector arms 150.

As shown, the gantry 102 includes a support surface 106 and a gantry actuator 108. The stage 102 is configured to hold the substrate 103 on a support surface 106. The gantry 102 is coupled to a gantry actuator 108. The gantry actuator 108 is configured to move the gantry 102 in the x-direction and the y-direction in a scan path 110 and to rotate the gantry 102 about the z-axis. The stage 102 is configured to move and rotate the substrate 103 such that light from the optical arm 104A is incident on different portions or areas of the substrate 103 during operation of the measurement system 101.

The substrate 103 includes one or more optical elements 105, the one or more optical elements 105 having one or more regions 107 of a grating 109. Each of the regions 107 has a grating 109 (FIG. 3) with an orientation angle φ and a pitch P, and P is defined as the distance between adjacent points, such as adjacent first edges 301 or adjacent centroids of the grating 109. The pitch P and the orientation angle phi of the grating 109 for the first region 111 may be different from the pitch P and the orientation angle phi of the grating 109 for the second region 113 of the one or more regions 107. In addition, there may be local pitch P 'variations and local orientation angle φ' variations due to local warpage or other deformation of the substrate 103. The measurement system 101 may be used to measure the pitch P and the orientation angle φ of the grating 109 for each region 107 of each optical element 105. The substrate 103 may be a single crystal wafer of any size, for example, having a radius of about 150mm to about 450 mm. As shown, the beam 126A from the optical arm 104A is scattered from the region 107 to the initial R₀In beam 450, as will be described in more detail below.

The optics arm 104, the detector arm 150, and the gantry 102 are coupled to a controller 130. The controller 130 facilitates control and automation of the methods for measuring the pitch P and the orientation angle φ of the gratings 109 described herein. The controller may include a Central Processing Unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processor used in an industrial setting for controlling various processes and hardware (e.g., motors and other hardware) and monitoring processes (e.g., transport element position and scan time). A memory (not shown) is connected to the CPU and may be a readily available memory such as a Random Access Memory (RAM). Software instructions and data may be encoded and stored in memory to instruct the CPU. Support circuits (not shown) are also connected to the CPU to support the processor in a conventional manner. The support circuits may include conventional cache, power supplies, clock circuits, input/output circuits, subsystems, and the like. A program (or computer instructions) readable by the controller determines which tasks are executable on the substrate 103. The program may be software readable by a controller and may include code for monitoring and controlling, for example, the substrate position and the optical arm position.

As shown, the optics arm 104A includes a white light source 114A, a first beam splitter 116A, a second beam splitter 118A, a laser 120, a detector 122, and a spectrometer 124. The white light source 114 may be a fiber coupled light source. The first beam splitter 116A is located in the optical path 126A adjacent the white light source 114. According to one embodiment, the white light source 114 is operable to project white light at a beam angle θ to the substrate 103 along the optical path 126A. The laser 120 may be a fiber coupled light source. Laser 120 is positioned adjacent first beam splitter 116A. The laser 120 is operable to project a beam having a wavelength to the first beam splitter 116A such that the beam is deflected along the optical path 126A at a beam angle θ to the substrate 103. The second beam splitter 118A is located in the optical path 126A adjacent to the first beam splitter 116A. The second beam splitter 118A is operable to deflect the beam reflected by the substrate 103 to the detector 122. Spectrometer 124 is coupled to detector 122 to determine the wavelength of the light beam deflected to detector 122. The light beam described herein may be a laser beam. The optical arm 104 conveys the light beam along the optical path 126 so that the light can be deflected by the substrate 103 and measured by one or more detector arms 150.

FIG. 1B shows a schematic view of a second configuration 100B of a measurement system 101 according to one embodiment. As shown, optical arm 104B includes a laser 120, a beam splitter 128, and a beam position detector 132. The beam position detector 132 may include an image sensor, such as a CCD or CMOS sensor. A beam splitter 128 is located in the optical path 126B adjacent to a beam position detector 132. Laser 120 is located adjacent to beam splitter 128. The laser 120 is operable to project a beam having a wavelength to the beam splitter 128 such that the beam is deflected at a beam angle θ along the optical path 126B to the substrate 103. According to one embodiment, optical arm 104B includes a polarizer 156 (e.g., a half-wave plate) and a quarter-wave plate 158. A polarizer 156 is located between the laser 120 and the beam splitter 128. The polarizer 156 maximizes the efficiency of the beam deflected by the beam splitter 128 at the beam angle θ. Quarter wave plate 158 is positioned in optical path 126B and is positioned adjacent to beam splitter 128. The quarter wave plate 158 maximizes the efficiency of the beam reflected by the substrate 103 to the beam position detector 132 and reduces the beam reflected to the laser 120.

FIG. 1C shows a schematic view of a third configuration 100C of a measurement system 101 according to one embodiment. The optical arm 104C includes lasers 134a, 134b.. 134n (collectively, "lasers 134") and beam splitters 136a, 136b.. 136n (collectively, "beam splitters 136"). A plurality of beam splitters 136 are positioned adjacent to the beam position detector 132 and adjacent to each other in the optical path 126C. The laser 134a is configured to project a beam having a first wavelength to the beam splitter 136a such that the beam of the first wavelength is deflected along the optical path 126C at the beam angle θ to reach the substrate 103. The laser 134b is configured to project the beam having the second wavelength to the beam splitter 136b such that the beam of the second wavelength is deflected along the optical path 126C at the beam angle θ to reach the substrate 103. The laser 134n is configured to project the beam having the third wavelength to the beam splitter 136n such that the beam of the third wavelength is deflected along the optical path 126C at the beam angle θ to reach the substrate 103.

Optical arm 104C may include polarizers 156a, 156b.. 156n (collectively "polarizers 156C") and a quarter wave plate 158. A plurality of polarizers 156C are between the plurality of lasers 134 and the plurality of beam splitters 136. The plurality of polarizers 156C maximize the efficiency of the beam deflected by the plurality of beam splitters 136 at the beam angle θ. A quarter wave plate 158 is located in the optical path 126C and adjacent to the beam splitter 136 n. The quarter wave plate 158 maximizes the efficiency of the beam reflected by the substrate 103 to the beam position detector 132. The quarter wave plate 158 is interchangeable for the desired wavelength.

In any of the above-described configurations 100A, 100B, 100C, the optical arm 104A, 104B, 104C may include an arm actuator 112, and the arm actuator is configured to rotate the optical arm 104 about the z-axis and scan the optical arm in the z-direction. The optical arm 104 may be fixed while the measurement is being performed.

The beam position detectors 132 of the second and third configurations 100B, 100C may be used to determine the beam position of the beam reflected by the substrate 103 to the beam position detector 132. Fig. 2A shows the beam position detector 132 as a position sensitive detector 201A, i.e. a lateral sensor, according to an embodiment. FIG. 2B shows the beam position detector 132 as a quadrant sensor 201B according to one embodiment. Fig. 2C illustrates a beam position detector 132, such as a Charge Coupled Device (CCD) array or a Complementary Metal Oxide Semiconductor (CMOS) array, as an image sensor array 201C, according to some embodiments.

Fig. 4A shows a schematic view of a detector arm 150 according to an embodiment. As shown, the detector arm 150 includes a detector 410, a detector arm actuator 152, and a first focusing lens 401. The detector arm actuator 152 is configured to rotate the detector arm 150 about the z-axis and scan the detector arm 150 in the z-direction. In fig. 4A to 4D, light from the optical path 126 is reflected from the region 107 of the substrate 103. Light is reflected to the initial R₀Of the light beam 450, the light beam is focused to a first R by the first focusing lens 401₀A light beam 411. First R₀Light beam 411 is incident on detector 410. The detector 410 is any optical element known in the art for detecting light, such as a CCD array or CMOS array.

Prior to measuring region 107, measurement system 101 may be calibrated using known substrate 103, and detector arm 150 may be positioned such that the first R₀The light beam 411 is incident on the optical center 401c of the first focusing lens 401. As described herein, any of the measurement systems 101 described above and below can be calibrated with a known substrate 103. Initial R for reference region 107 due to local deformation in region 107₀The light beam 450 is no longer incident on the optical center 401c of the focusing lens 401. For example, there may be local warpage of the substrate 103 at region 107, or global wafer tilt, wedge, warpageOr curved. The substrate 103 may tilt on the support surface 106 due to the presence of particles on the support surface, and particles arranged between the substrate 103 and the support surface may cause local and/or global deformations, such as the height of the raised area 107 or the tilting of this area towards the support surface (shown as tilted substrate 103t in fig. 4A-4D). According to one embodiment, in these cases where there is a tilted substrate 103t, the initial R is₀Light beam 450t is at a first angle Δ θ₁Is incident on the first focusing lens 401, and the first R₀The light beam 411t is focused to a portion of the detector 410 that is in contact with the focused first R of the known substrate 103₀Beams 411 are spaced apart by about a first incremental distance Δ₁. First incremental distance Δ₁By a₁＝f₁*tan(Δθ₁) Given therein, f₁Is the focal length of the focusing lens 401. Thus, the first incremental distance Δ₁And a first angle delta theta₁May be used to obtain local distortion information as described in further detail below. According to one embodiment, the resolution of detector 410 is less than about Δ₁。

Fig. 4B shows a schematic view of a detector arm 150 according to an embodiment. As shown, the detector arm 150 also includes a second focusing lens 402 and a third focusing lens 403. Initial R₀Beam 450t is at Δ θ₁Is incident on the first focusing lens 401, and the first focusing lens will initially R₀The light beam is focused to a first R₀Light beam 411 t. First R₀Light beam 411t is incident on second focusing lens 402, and first focusing lens will first R₀The light beam is focused to a second R₀Light beam 412 t. According to one embodiment, the second R₀Light beam 412 is incident on third focusing lens 403 at a second point of incidence, and the third focusing lens directs a second R₀The light beam is focused to the third R₀Beam 413t reaches a portion of detector 410 that is in contact with a focused third R of the known substrate₀The beams are spaced apart by about a second incremental distance Δ₂In which Δ₂＝Δ₁*f₃/f₂，f₂Is the focal length of the second focusing lens, f₃Is the focal length of the third focusing lens. In addition, Δ₂＝f₃*f₁*tan(Δθ₁)/f₂. Thus, the second incremental distance Δ₂May be used to pass through the first angle Δ θ₁To obtain local distortion information as described in further detail below. In some embodiments, the second incremental distance Δ₂Greater than a first incremental distance Δ₁This allows the use of a detector 410 with a lower resolution, since the detector is only subject to the second incremental distance Δ₂Is limited in size. According to one embodiment, the resolution of detector 410 is less than about Δ₂。

Although three focusing lenses 401, 402, 403 are included in detector arm 150 as described above, it is contemplated that any number of focusing lenses may be used and that the lenses may be configured similarly to the lenses described above in order to produce an even greater incremental distance measured by detector 410.

Fig. 4C shows a schematic view of the measurement system 101 with the primary detector arm 150 and the secondary detector arm 150' according to an embodiment. The main detector arm 150 is substantially similar to the detector arm described above in fig. 4A. As shown, the secondary detector arm 150 'includes a first focusing lens 401', a detector 410', and a detector actuator 152'. In this embodiment, light following the light path 126 is backscattered to produce a reflected R₁Light beam 450 t'. According to one embodiment, the secondary detector arm 150t' is located behind the optical arm 104, and the optical arm is responsible for the reflected R₁The light beam 450t' is at least partially transparent.

According to one embodiment, the reflected R₁Light beam 450t ' is incident on a third focal point of first focusing lens 401', which is a third incremental distance Δ from optical center 401c ' of the first focusing lens₃And the first focusing lens will reflect the R₁The light beam is focused to a first R₁In beam 411 t'. Third incremental distance Δ₃By a₃＝f_1′*tan(Δθ₂) Given therein, f_1′Is the focal length of the focusing lens 401'. Thus, the third incremental distance Δ₃And a firstTwo angles delta theta₂May be used to obtain local distortion information as described in further detail below. According to one embodiment, the resolution of detector 410' is less than about Δ₃. The displacement angle delta theta is changed from delta theta to delta theta₂–Δθ₁Given that the displacement angle Δ θ gives the grating P_t-gratingAs described in more detail below.

Fig. 4D shows a schematic view of the measurement system 101 with the primary detector arm 150 and the secondary detector arm 150' according to an embodiment. The main detector arm 150 is substantially similar to the detector arm described above in fig. 4B. As shown, secondary detector arm 150 'includes a first focusing lens 401', a second focusing lens 402', a third focusing lens 403', a detector 410', and a detector actuator 152'. In this embodiment, light following the light path 126 is backscattered to produce a reflected R₁Light beam 450 t'. According to one embodiment, the secondary detector arm 150' is located behind the optical arm 104, and the optical arm is directed to the reflected R₁The light beam 450' is at least partially transparent.

According to one embodiment, the reflected R₁Light beam 450t ' is incident on a third focal point of first focusing lens 401', which is a third incremental distance Δ from optical center 401c ' of the first focusing lens₃And the first focusing lens focuses the reflected R1 light beam to a first R₁In beam 411 t'. First R₁Light beam 411t 'is incident on second focusing lens 402', and first focusing lens will first R₁The light beam is focused to a second R₁Light beam 412 t'. Second R₁Light beam 412t 'is incident a fourth incremental distance Δ from optical center 403c' of third focusing lens 403₄And the third focusing lens focuses the second R onto the fourth focusing point₁The light beam is focused to the third R₁Beam 413t 'reaches a portion of detector 410' that is in focus with a third R of the known substrate₁The beams are a fourth incremental distance Δ from each other₄. Thus, similar to the second incremental distance Δ₂Fourth incremental distance Δ₄May be used to obtain local distortion information.

In some implementationsIn this manner, the fourth incremental distance Δ₄Greater than a third incremental distance Δ₃This allows the use of a detector 410' with a lower resolution, since the detector is only subject to the fourth incremental distance Δ₄Is limited in size. Two incremental distances Δ₂、Δ₄Allowing an even more detailed measurement of the local distortion of the region 107. According to one embodiment, the third incremental distance Δ₃Greater than a first incremental distance Δ₃. According to one embodiment, the resolution of detector 410' is less than about Δ₄. According to one embodiment, the focal length of the first focusing lens 401 of the main detector arm 150 is different from the focal length of the second focusing lens 402 of the main detector arm, and the focal length of the second focusing lens of the main detector arm is different from the focal length of the third focusing lens 403 of the main detector arm.

Although fig. 4C-4D show the measurement system 101 having two detector arms 150, 150 'with the two detector arms 150, 150' having the same number of focusing lenses, it should be understood that any odd number of lenses may be used in each detector arm. For example, the primary detector arm 150 may have one focusing lens and the secondary detector arm 150' may have three focusing lenses, or vice versa. In other examples, the primary detector arm 150 has five focusing lenses and the secondary detector arm 150' has three focusing lenses.

In all the above and below embodiments, Δ₁、Δ₂、Δ₃And Δ₄Is in the range of about 10 μm to about 1mm, and Δ θ₁、Δθ₂、Δθ₃And Δ θ₄Ranges from about 0.001 ° to about 1 °, for example from about 0.001 ° to about 0.1 °.

FIG. 5 is a flowchart of the method 500 operations for diffracting light, according to one embodiment. Although the method operations are described in conjunction with fig. 5, those skilled in the art will understand that any system configured to perform the method operations in any order is within the scope of the embodiments described herein.

The method 500 begins at operation 540 where a beam having a wavelength λ is at a fixed beam angle θ at operation 540₀And a maximum orientation angle phi_maxIs projected onto a first area 107 of the first substrate 103. The method 500 may utilize any of the configurations 100A, 100B, 100C of the measurement system 101 and any of the detector arm 150 configurations of FIGS. 1A-C and 4A-D. The white light source 114 is at a fixed beam angle θ along the optical path 126A₀Projecting the white light onto a reference area 107, wherein the reference area 107 has one or more gratings 109, θ₀＝arcsin(λ_laser/2P_grating) And P is_gratingIs the design/average pitch of the grating.

In operation 550, a displacement angle Δ θ is obtained. According to some embodiments, the displacement angle Δ θ is equal to the first angle Δ θ₁Where Δ θ₁By a₁＝f₁*tan(Δθ₁) Given, and the displacement distance Δ₁Measured as described above. In some embodiments, the displacement angle Δ θ is defined by Δ θ ═ Δ θ, as described above₂-Δθ₁Given, wherein the second angle Δ θ₂By a₂＝f₁*f₃*tan(Δθ₂)/f₂It is given.

In operation 560, the gantry 102 is rotated until at a fixed beam angle θ₀Where the initial intensity maximum (initial I) is measured_max) To obtain a maximum orientation angle phi_max. Maximum orientation angle phi_maxCorresponding to the orientation angle phi of the one or more gratings 109 at the reference region 107. Calculating a target maximum beam angle θ_t-maxWherein theta_t-max＝θ₀+ Δ θ. Calculating a target maximum toe angle θ using Δ θ_t-maxThe overall deformation of the substrate, such as by tilting or warping, is taken into account.

At operation 570, at a maximum orientation angle φ_maxDetermining a test grating pitch P_t-grating. Determining the initial spacing includes determining the initial spacing at a fixed beam angle θ₀And a maximum orientation angle phi_maxProjecting white light and solving the formula P_t-grating＝P_grating+ΔP＝λ_laser/(sinθ_t-max+sinθ₀). Furthermore, the measured pitch change Δ P is given by:

the change in measured pitch Δ P may be from about 1pm to about 5 nm.

In one embodiment, operations 540, 550, 560, and 570 are repeated. At operation 570, the gantry 102 is scanned along the scan path 110 and operations 540, 550, and 560 are repeated for subsequent regions of the one or more regions 107 of the one or more optical elements 105, or operations 540, 550, and 560 are repeated for subsequent regions. In addition, operations 540, 550, 560, and 570 are repeated after the entire substrate 103 is rotated about the z-axis by about 180 °, which allows for an overall measurement of the wafer wedge.

As described above, apparatus and methods configured to measure local non-uniformities of optical elements are included. The reflected laser light is detected by a detector arm. The detector arm includes one or more focusing lenses, and the one or more focusing lenses focus light onto a detector, such as a camera. The reflected light is used to calculate the local non-uniformity present as compared to the test substrate displacement. The substrate may be scanned so that non-uniformities may be measured in different areas of the substrate.

The measurement system and method allow for measurement of non-uniform characteristics of optical elements on a substrate, such as grating pitch and grating orientation. In addition, the measurement system and method may determine local warpage or deformation in the underlying substrate. Furthermore, defects, such as particles, of the support surface of the underlayer may be located to determine whether the substrate and optical element have acceptable characteristics. Measurements may be performed on substrates or optical elements of various sizes or shapes.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.