Measuring system and method of diffracted light

Abstract

Embodiments of the present disclosure relate to a measurement system and a method for diffracting light. The measurement system includes a stage, an optical arm, and one or more detector arms. The method for diffracting light includes providing a method for diffracting light, the method including providing a method for diffracting light with a fixed beam angle θ0 and a maximum orientation angle φ max will have a wavelength λ laser The light beam is projected onto the first area of ​​the first substrate; a displacement angle Δθ is obtained; and a target maximum beam angle θ is determined. t‑max , where θ t‑max =θ0+Δθ, and through the modified grating spacing formula P t‑grating =λ laser / (sinθ t‑max +sinθ0) to determine the test grating spacing P t‑grating The measurement system and method allow for the measurement of non-uniform properties of a region of an optical element, such as grating pitch and grating orientation.

Description

[0001] This application is a divisional application of the invention patent application with application date of April 6, 2020, application number 202080027552.5, and invention name “Measuring system and method of diffracted light”. Technical Field

[0002] Embodiments of the present disclosure relate to apparatus and methods, and more particularly, to systems and methods of measuring diffracted light. Background Art

[0003] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has a palpable physical presence. Virtual reality experiences can be generated in 3D and viewed using a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces the actual environment.

[0004] However, augmented reality technology provides an experience where the user can still see the surrounding environment through the display lenses of glasses or other HMD devices, while also seeing virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and images that can enhance or augment the environment experienced by the user. To achieve an augmented reality experience, virtual images are superimposed on the surrounding environment, and the superposition is performed by optical elements.

[0005] One disadvantage of the art is that the fabricated optical elements tend to have non-uniform properties, 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 deposition is performed on a substrate that is disposed on an uneven support surface (e.g., where there are defects or particles on the support surface), the substrate may be tilted and the deposited optical element may also inherit these deformations.

[0006] Therefore, there is a need in the art for apparatus and methods for detecting inhomogeneities in optical elements. Summary of the invention

[0007] In one embodiment, a measurement system is provided, which includes a stage; an optical arm connected to an arm actuator, the arm actuator being configured to scan the optical arm and rotate the optical arm around an axis, and a detector arm. The stage has a substrate support surface. The stage is coupled to the stage actuator, the stage actuator being configured to move the stage in a scanning path and rotate the stage around an axis. The optical arm includes a laser located adjacent to a beam splitter, the beam splitter being located in an optical path adjacent to an optical detector, the laser being operable to project a light beam to the beam splitter, the light beam being deflected along the optical path at a beam angle θ to reach the stage. The detector arm includes a detector actuator, a first focusing lens, and a detector, the detector actuator being configured to scan the detector arm and around the axis detector arm.

[0008] In another embodiment, a measurement system is provided, including a stage; an optical arm connected to an 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 stage is coupled to the stage actuator, which is configured to move the stage in a scanning path and rotate the stage about an axis. The optical arm includes a laser located adjacent to a beam splitter, the beam splitter is located in an optical path adjacent to the optical detector, the laser is operable to project a light beam to the beam splitter, and the light beam is deflected along the optical path at a beam angle θ to reach the stage. Each detector arm includes a detector actuator configured to scan the detector arm, a first focusing lens, and a detector.

[0009] In yet another embodiment, a method for diffracting light is provided, the method comprising: max will have a wavelength λ laser The light beam is projected onto the first area of ​​the first substrate; a displacement angle Δθ is obtained; and a target maximum beam angle θ is determined. t-max , where θ t-max =θ0+Δθ; and through the modified grating spacing formula P t-grating =λ laser / (sinθ t-max +sinθ0) to determine the test grating spacing P t-grating .

[0010] The measurement system and the measurement method measure the local inhomogeneity of the area of ​​the optical element, such as the grating pitch and the grating orientation. The local inhomogeneity value can be used to evaluate the performance of the optical element. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order that the manner in which the above-mentioned features of the present disclosure can be understood in detail, a more detailed description of the present disclosure briefly summarized above can be obtained by reference to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the drawings only show exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, and other equivalent embodiments may be allowed.

[0012] Figures 1A to 1C A schematic diagram showing the configuration of a measurement system according to some embodiments is shown.

[0013] Figures 2A to 2C A schematic view of a beam position detector according to some embodiments is shown.

[0014] Figure 3 A schematic cross-sectional view of a first region according to one embodiment is shown.

[0015] Figures 4A to 4D Shown is a schematic view of a measurement system including one or more detector arms according to some embodiments.

[0016] Figure 5 is a flow chart of method operations for diffracting light according to one embodiment.

[0017] 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

[0018] Embodiments of the present disclosure relate to a measurement system and method for measuring local non-uniformity of an optical element. The measurement system includes a stage, 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 is incident on a detector. Deflection from the optical center of the focusing lens is used to determine the local non-uniformity of the optical element. The method of diffracting light includes measuring a scattered light beam from the surface of the substrate, and obtaining a local deformation based on the measured value. The embodiments disclosed herein may be particularly useful for (but not limited to) measuring local uniformity in an optical system.

[0019] As used herein, the term "about" refers to a + / - 10% variation from the nominal value. It should be understood that such variations can be included in any value provided herein.

[0020] Figure 1AA schematic view of a first configuration 100A of a measurement system 101 according to one embodiment is shown. As shown, the measurement system 101 includes a stage 102, an optical arm 104A, and one or more detector arms 150. The measurement system 101 is configured to diffract light generated by the optical arm 104. The light generated by the optical arm 104 is directed to a substrate disposed above the stage 102, and the diffracted light is incident on the one or more detector arms 150.

[0021] As shown, the stage 102 includes a support surface 106 and a stage actuator 108. The stage 102 is configured to hold the substrate 103 on the support surface 106. The stage 102 is coupled to the stage actuator 108. The stage actuator 108 is configured to move the stage 102 along the x-direction and the y-direction in the scanning path 110, and to rotate the stage 102 about the z-axis. The stage 102 is configured to move and rotate the substrate 103 so that during operation of the measurement system 101, light from the optical arm 104A is incident on different portions or areas of the substrate 103.

[0022] The substrate 103 includes one or more optical elements 105 having one or more regions 107 of gratings 109. Each of the regions 107 has a grating 109 ( Figure 3 ), 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 orientation angle φ of the grating 109 used for the first region 111 may be different from the pitch P and orientation angle φ of the grating 109 used for the second region 113 of one or more regions 107. In addition, there may be local pitch P' variations and local orientation angle φ' variations due to local warping or other deformations of the substrate 103. The measurement system 101 can be used to measure the pitch P and orientation angle φ of the grating 109 for each region 107 of each optical element 105. The substrate 103 can be a single crystal wafer of any size, for example having a radius of about 150 mm to about 450 mm. As shown, the beam 126A from the optical arm 104A is scattered from the region 107 into the initial R0 beam 450, which will be described in more detail below.

[0023] The optical arm 104, the detector arm 150, and the stage 102 are coupled to a controller 130. The controller 130 facilitates control and automation of the method for measuring the pitch P and orientation angle φ of the grating 109 described herein. The controller may include a central processing unit (CPU) (not shown), a memory (not shown), and support circuits (or I / O) (not shown). The CPU may be one of any form of computer processor used in industrial settings to control various processes and hardware (e.g., motors and other hardware) and monitor processes (e.g., transport element position and scan time). The memory (not shown) is connected to the CPU and may be readily available memory, such as random access memory (RAM). Software instructions and data may be encoded and stored in the 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 caches, power supplies, clock circuits, input / output circuits, subsystems, etc. A program (or computer instructions) readable by the controller determines which tasks may be performed on the substrate 103. The program may be software readable by the controller and may include code for monitoring and controlling, for example, the position of the substrate and the position of the optical arm.

[0024] As shown, the optical 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 can be a fiber-coupled light source. The first beam splitter 116A is located adjacent to the white light source 114 in the optical path 126A. According to one embodiment, the white light source 114 is operable to project white light along the optical path 126A to the substrate 103 at a beam angle θ. The laser 120 can be a fiber-coupled light source. The laser 120 is positioned near the first beam splitter 116A. The laser 120 is operable to project a light beam having a wavelength to the first beam splitter 116A, so that the light beam is deflected along the optical path 126A at a beam angle θ and reaches the substrate 103. The second beam splitter 118A is located adjacent to the first beam splitter 116A in the optical path 126A. The second beam splitter 118A is operable to deflect the light beam reflected by the substrate 103 to the detector 122. The spectrometer 124 is coupled to the detector 122 to determine the wavelength of the light beam deflected to the detector 122. The light beam described herein may be a laser beam. The optical arm 104 delivers 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.

[0025] Figure 1BA schematic view of a second configuration 100B of the measurement system 101 according to one embodiment is shown. As shown, the 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. The beam splitter 128 is located adjacent to the beam position detector 132 in the optical path 126B. The laser 120 is located adjacent to the beam splitter 128. The laser 120 is operable to project a beam having a wavelength to the beam splitter 128 so that the beam reaches the substrate 103 with a deflection at a beam angle θ along the optical path 126B. According to one embodiment, the optical arm 104B includes a polarizer 156 (e.g., a half-wave plate) and a quarter-wave plate 158. The 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 a beam angle θ. The quarter wave plate 158 is located in the optical path 126B and is located adjacent to the beam splitter 128. The quarter wave plate 158 maximizes the efficiency of the light beam reflected by the substrate 103 to the beam position detector 132 and reduces the light beam reflected to the laser 120.

[0026] Figure 1C A schematic view of a third configuration 100C of the measurement system 101 according to one embodiment is shown. The optical arm 104C includes lasers 134a, 134b...134n (collectively referred to as "plurality of lasers 134") and beam splitters 136a, 136b...136n (collectively referred to as "plurality of beam splitters 136"). The plurality of beam splitters 136 are adjacent to the beam position detector 132 in the optical path 126C and are positioned adjacent to each other. The laser 134a is configured to project a light beam having a first wavelength to the beam splitter 136a, so that the light beam of the first wavelength is deflected at a beam angle θ along the optical path 126C and reaches the substrate 103. The laser 134b is configured to project a light beam having a second wavelength to the beam splitter 136b, so that the light beam of the second wavelength is deflected at a beam angle θ along the optical path 126C and reaches the substrate 103. The laser 134 n is configured to project a light beam having a third wavelength to the beam splitter 136 n , so that the light beam having the third wavelength is deflected along the optical path 126C at a beam angle θ and reaches the substrate 103 .

[0027] The optical arm 104C may include polarizers 156a, 156b ... 156n (collectively referred to as "plurality of polarizers 156C") and a quarter wave plate 158. The plurality of polarizers 156C are between the plurality of lasers 134 and the plurality of beam splitters 136. The plurality of polarizers 156C maximizes the efficiency of the beams deflected at the beam angle θ by the plurality of beam splitters 136. The quarter wave plate 158 is located in the optical path 126C and is adjacent to the beam splitter 136n. 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.

[0028] In any of the above 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 around the z-axis and scan the optical arm in the z-direction. The optical arm 104 may be fixed while performing measurements.

[0029] The beam position detectors 132 of the second configuration 100B and the third configuration 100C may be used to determine the beam position of the beam reflected by the substrate 103 to the beam position detector 132 . Figure 2A The beam position detector 132 is shown as a position sensitive detector 201A, ie a lateral sensor, according to one embodiment. Figure 2B The beam position detector 132 is shown as a quadrant sensor 201B according to one embodiment. Figure 2C The beam position detector 132 is shown as an image sensor array 201C, such as a charge coupled device (CCD) array or a complementary metal oxide semiconductor (CMOS) array, according to some embodiments.

[0030] Figure 4A 1 shows a schematic view of a detector arm 150 according to one 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. Figures 4A to 4D , light from the optical path 126 is reflected from the region 107 of the substrate 103. The light is reflected into an initial R0 beam 450, which is focused by the first focusing lens 401 into a first R0 beam 411. The first R0 beam 411 is incident on the detector 410. The detector 410 is any optical element in the art for detecting light, such as a CCD array or a CMOS array.

[0031] Prior to measuring region 107, the measurement system 101 may be calibrated using a known substrate 103, and the detector arm 150 may be positioned such that a first R0 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 may be calibrated using a known substrate 103. Due to local deformations in region 107, the initial R0 beam 450 used to reference region 107 is no longer incident on the optical center 401c of the focusing lens 401. For example, there may be local warping of the substrate 103 at region 107, or overall wafer tilt, wedge, warp, or bend. The substrate 103 may tilt on the support surface 106 due to the presence of particles on the support surface, and particles disposed between the substrate 103 and the support surface may cause local and / or overall deformations, such as the height of the raised region 107 or the tilt of the region toward the support surface (in Figures 4A to 4D 1 is shown as a tilted substrate 103t). According to one embodiment, in these cases where there is a tilted substrate 103t, the initial R0 beam 450t is incident on the first focusing lens 401 at a first angle Δθ1, and the first R0 beam 411t is focused to a portion of the detector 410 that is approximately a first incremental distance Δ1 away from the focused first R0 beam 411 of the known substrate 103. The first incremental distance Δ1 is given by Δ1=f1*tan(Δθ1), where f1 is the focal length of the focusing lens 401. Therefore, the first incremental distance Δ1 and the first angle Δθ1 can be used to obtain local distortion information, as described in further detail below. According to one embodiment, the resolution of the detector 410 is less than approximately Δ1.

[0032] Figure 4BA schematic view of a detector arm 150 according to one embodiment is shown. As shown, the detector arm 150 also includes a second focusing lens 402 and a third focusing lens 403. An initial R0 beam 450t is incident on the first focusing lens 401 at an angle of Δθ1, and the first focusing lens focuses the initial R0 beam to a first R0 beam 411t. The first R0 beam 411t is incident on the second focusing lens 402, and the second focusing lens focuses the first R0 beam to a second R0 beam 412t. According to one embodiment, the second R0 beam 412 is incident on the third focusing lens 403 at a second incident point, and the third focusing lens focuses the second R0 beam to a third R0 beam 413t to reach a portion of the detector 410 that is approximately a second incremental distance Δ2 from the focused third R0 beam of the known substrate, where Δ2=Δ1*f3 / f2, f2 is the focal length of the second focusing lens, and f3 is the focal length of the third focusing lens. Additionally, Δ2=f3*f1*tan(Δθ1) / f2. Thus, the second incremental distance Δ2 can be used to obtain local distortion information using the first angle Δθ1, as described in further detail below. In some embodiments, the second incremental distance Δ2 is greater than the first incremental distance Δ1, which allows the use of a detector 410 with a lower resolution because the detector is only limited by the size of the second incremental distance Δ2. According to one embodiment, the resolution of the detector 410 is less than about Δ2.

[0033] Although three focusing lenses 401 , 402 , 403 are included in the detector arm 150 as described above, it is contemplated that any number of focusing lenses may be used and that the lenses may be constructed similarly to those described above in order to produce even greater incremental distances measured by the detector 410 .

[0034] Figure 4C A schematic view of a measurement system 101 having a primary detector arm 150 and a secondary detector arm 150' is shown according to one embodiment. The primary detector arm 150 is substantially similar to that described above in Figure 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, the light following the optical path 126 is scattered back to produce a reflected R1 beam 450t'. According to one embodiment, the secondary detector arm 150t' is located behind the optical arm 104, and the optical arm is at least partially transparent to the reflected R1 beam 450t'.

[0035] According to one embodiment, the reflected R1 beam 450t' is incident on a third focus point on the first focusing lens 401', the third focus point is separated from the optical center 401c' of the first focusing lens by a third incremental distance Δ3, and the first focusing lens focuses the reflected R1 beam into the first R1 beam 411t'. The third incremental distance Δ3 is given by Δ3=f 1′ *tan(Δθ2) is given by, where f 1′ is the focal length of the focusing lens 401'. Therefore, the third incremental distance Δ3 and the second angle Δθ2 can be used to obtain local distortion information, as described in further detail below. According to one embodiment, the resolution of the detector 410' is less than about Δ3. The displacement angle Δθ is given by Δθ=Δθ2-Δθ1, and the displacement angle Δθ gives the grating P t-grating local deformation of the spacing, as described in more detail below.

[0036] Figure 4D A schematic view of a measurement system 101 having a primary detector arm 150 and a secondary detector arm 150' is shown in accordance with one embodiment. The primary detector arm 150 is substantially similar to that described above in Figure 4B . As shown, the 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, the light following the optical path 126 is scattered back to produce a reflected R1 beam 450t'. According to one embodiment, the secondary detector arm 150' is located behind the optical arm 104, and the optical arm is at least partially transparent to the reflected R1 beam 450'.

[0037] According to one embodiment, the reflected R1 beam 450t' is incident on a third focusing point on the first focusing lens 401', the third focusing point is a third incremental distance Δ3 from the optical center 401c' of the first focusing lens, and the first focusing lens focuses the reflected R1 beam into a first R1 beam 411t'. The first R1 beam 411t' is incident on the second focusing lens 402', and the second focusing lens focuses the first R1 beam into a second R1 beam 412t'. The second R1 beam 412t' is incident on a fourth focusing point a fourth incremental distance Δ4 from the optical center 403c' of the third focusing lens 403', and the third focusing lens focuses the second R1 beam into a third R1 beam 413t' to a portion of the detector 410', which is a fourth incremental distance Δ4 from the focused third R1 beam of the known substrate. Therefore, similar to the second incremental distance Δ2, the fourth incremental distance Δ4 can be used to obtain local distortion information.

[0038] In some embodiments, the fourth incremental distance Δ4 is ​​greater than the third incremental distance Δ3, which allows the use of a detector 410' with a lower resolution, since the detector is only limited by the size of the fourth incremental distance Δ4. The two incremental distances Δ2, Δ4 allow for an even more detailed measurement of the local distortion of the region 107. According to one embodiment, the third incremental distance Δ3 is greater than the first incremental distance Δ1. According to one embodiment, the resolution of the 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.

[0039] Although Figures 4C to 4D A measurement system 101 with two detector arms 150, 150' is shown with both detector arms 150, 150' having the same number of focusing lenses, it being 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.

[0040] In all above and below embodiments, Δ1, Δ2, Δ3 and Δ4 range from about 10 μm to about 1 mm, and Δθ1, Δθ2, Δθ3 and Δθ4 range from about 0.001° to about 1°, for example, about 0.001° to about 0.1°.

[0041] Figure 5 is a flow chart of the operation of a method 500 for diffracting light according to one embodiment. Figure 5 Having described method operations, one skilled in the art will understand that any system configured to perform the method operations, in any order, falls within the scope of the embodiments described herein.

[0042] The method 500 begins with operation 540, where a light beam having a wavelength λ is directed at a fixed beam angle θ0 and a maximum orientation angle φ max projected onto the first region 107 of the first substrate 103. The method 500 may utilize Figure 1A 4A-D and any configuration 100A, 100B, 100C of the measurement system 101 and any configuration of the detector arm 150. The white light source 114 projects white light along the optical path 126A to the reference area 107 at a fixed beam angle θ0, wherein the reference area 107 has one or more gratings 109, θ0=arcsin(λ laser / 2P grating ), and Pgrating is the design / average spacing of the grating.

[0043] At operation 550, a displacement angle Δθ is obtained. According to some embodiments, the displacement angle Δθ is equal to the first angle Δθ1, where Δθ1 is given by Δ1=f1*tan(Δθ1), and the displacement distance Δ1 is measured as described above. In some embodiments, as described above, the displacement angle Δθ is given by Δθ=Δθ2-Δθ1, where the second angle Δθ2 is given by Δ2=f1*f3*tan(Δθ2) / f2.

[0044] At operation 560, the gantry 102 is rotated until an initial intensity maximum (initial I max ) to obtain the maximum orientation angle φ max . Maximum orientation angle φ max Corresponds to the orientation angle φ of one or more gratings 109 at the reference area 107. Calculate the target maximum beam angle θ t-max , where θ t-max =θ0+Δθ. Use Δθ to calculate the target maximum beam angle θ t-max Overall deformation of the substrate, such as by tilting or warping, is taken into account.

[0045] At operation 570, at the maximum orientation angle φ max Determine the test grating spacing P t-grating Determining the initial spacing involves fixing the beam angle θ0 and the maximum orientation angle φ max Project white light and solve the formula P t-grating =P grating +ΔP=λ laser / (sinθ t-max +sinθ0). In addition, the measured spacing change ΔP is given by:

[0046]

[0047] The measured change in spacing ΔP can be from about 1 pm to about 5 nm.

[0048] In one embodiment, operations 540, 550, 560, and 570 are repeated. At operation 570, the stage 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 for subsequent regions. Additionally, operations 540, 550, 560, and 570 are repeated after the entire substrate 103 is rotated about 180° about the z-axis, which allows for overall measurement of the wafer wedge.

[0049] As described above, an apparatus and method configured to measure local non-uniformity of an optical element are included. 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 the light onto a detector, such as a camera. The reflected light is displaced relative to a test substrate and used to calculate the local non-uniformity present. The substrate can be scanned so that the non-uniformity of different regions of the substrate can be measured.

[0050] The measurement system and method allow for the measurement of non-uniform properties of an optical element on a substrate, such as grating spacing and grating orientation. Additionally, the measurement system and method can determine localized warping or deformation in the underlying substrate. Moreover, defects in the underlying support surface, such as particles, can be located to determine whether the substrate and optical element have acceptable properties. Measurements can be performed on substrates or optical elements of various sizes or shapes.

[0051] 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 of the disclosure is determined by the claims that follow.

Claims

1. A measurement system comprising: a stage having a substrate supporting surface, the stage connected to a stage actuator configured to move the stage in a scanning path and to rotate the stage about an axis perpendicular to the substrate supporting surface; an optical arm coupled to an arm actuator configured to scan the optical arm in a direction along which the axis extends and to rotate the optical arm about the axis to cause the optical arm to project a light beam along an optical path at a beam angle θ onto a substrate disposed on the substrate supporting surface, the optical arm having: a laser adjacent to a beam splitter, the beam splitter being located in an optical path adjacent to an optical detector disposed in the optical arm, the laser being operable to project a plurality of light beams to the beam splitter, the plurality of light beams being deflected along the optical path at a beam angle θ to reach the stage, wherein the optical detector is operable to detect light beams reflected to the optical arm along the optical path through the beam splitter to reach the optical detector; and Detector arm, comprising: a detector actuator configured to scan the detector arm in a direction along which the axis extends and to rotate the detector arm about the axis so that diffracted light of the light beam generated by the optical arm is incident on the detector arm; a first focusing lens; and a detector configured to acquire a first incremental distance Δ1 separating a first incident point of an initial R0 light beam to be projected onto the first focusing lens from an optical center of the first focusing lens, Wherein a first angle Δθ1 is determined according to the first incremental distance Δ1 using the formula Δ1=f1*tan(Δθ1), wherein the first angle Δθ1 is the angle at which the initial R0 light beam is incident on the first focusing lens, f1 is the focal length of the first focusing lens, and wherein the first incremental distance Δ1 and the first angle Δθ1 are used to determine local distortion information.

2. The measurement system according to claim 1, wherein: The optical arm further comprises: a polarizer positioned between the laser and the beam splitter; and A quarter wave plate is located on the optical path adjacent to the beam splitter.

3. The measurement system according to claim 1, wherein: The detector has a resolution of less than about Δ1. The measurement system according to claim 1 , further comprising a second focusing lens and a third focusing lens.

5. The measurement system according to claim 4, wherein: The initial R0 beam is focused into a first R0 beam by the first focusing lens, the first R0 beam is focused into a second R0 beam by the second focusing lens, and the second R0 beam is focused into a third R0 beam by the third focusing lens.

6. The measurement system according to claim 5, wherein: The third R0 light beam is incident on the third focusing lens at a third incident point, The third point of incidence is separated from the optical center of the third focusing lens by a second incremental distance Δ2, and The second incremental distance Δ2 is greater than the first incremental distance Δ1.

7. A measurement system comprising: a stage having a substrate supporting surface, the stage connected to a stage actuator configured to move the stage in a scanning path and to rotate the stage about an axis perpendicular to the substrate supporting surface; an optical arm coupled to an arm actuator configured to scan the optical arm in a direction along which the axis extends and to rotate the optical arm about the axis to cause the optical arm to project a light beam along an optical path at a beam angle θ onto a substrate disposed on the substrate supporting surface, the optical arm comprising: a laser located adjacent to a beam splitter disposed in an optical path adjacent to an optical detector disposed in the optical arm, the laser being operable to project a plurality of light beams to the beam splitter, the plurality of light beams being deflected along the optical path at a beam angle θ to reach the stage, wherein the optical detector being operable to detect light beams reflected to the optical arm along the optical path through the beam splitter to reach the optical detector; and a primary detector arm and a secondary detector arm, each of the primary detector arm and the secondary detector arm comprising: a detector actuator configured to scan the primary detector arm or the secondary detector arm in a direction along which the axis extends and to rotate the detector arm around the axis so that diffracted light of the light beam generated by the optical arm is incident on the primary detector arm or the secondary detector arm; a first focusing lens; and a detector configured to acquire a first incremental distance Δ1 separating a first incident point of an initial R0 light beam to be projected onto the first focusing lens from an optical center of the first focusing lens, Wherein, the first angle Δθ1 is determined according to the first incremental distance Δ1 using the formula Δ1=f1*tan(Δθ1), the first angle Δθ1 is the angle at which the initial R0 light beam is incident on the first focusing lens, and f1 is the focal length of the first focusing lens, wherein the first incremental distance Δ1 and the first angle Δθ1 are used to determine local distortion information.

8. The measurement system according to claim 7, wherein: The secondary detector arm is arranged behind the optical arm.

9. The measurement system according to claim 8, wherein: The plurality of light beams are reflected from the workpiece placed on the stage into a reflected R1 light beam, the reflected R1 light beam is incident on a first focusing lens of the secondary detector arm at a first incident point 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.

10. The measurement system of claim 9, wherein the first incremental distance Δ1 is less than about 1 mm.

11. The measurement system of claim 7, wherein the focal length of the first focusing lens of the primary detector arm is different from the focal length of the first focusing lens of the secondary detector arm.

12. A method for measuring the inhomogeneity of an optical element using the measuring system according to claim 1 or 7, comprising the following steps: The wavelength λ is transmitted from the optical arm laser Multiple beams with fixed beam angle θ0 and maximum orientation angle φ max projected onto a first area of ​​a first substrate disposed on a stage and having a grating thereon, the beam angle θ0 being the angle of the beam relative to an axis perpendicular to the first substrate, and the maximum orientation angle φ max is the angle at which the gantry is rotated about the axis when the initial intensity maximum of the beam is measured at the beam angle θ0, and the maximum orientation angle φ max an orientation angle corresponding to the grating at the first region; Obtaining a displacement angle Δθ, wherein the displacement angle Δθ is an angle between a reflected light of the light beam leaving the first substrate and a reflected light of the light beam leaving a known substrate used for calibration; Determine the target maximum beam angle θ t-max , where θ t-max =θ0+Δθ; and By the modified grating spacing formula P t-grating =λ laser / (sinθ t-max +sinθ0) to determine the test grating spacing P t-grating .

13. The method according to claim 12, wherein: Repeat the steps of projecting multiple beams, obtaining the displacement angle Δθ, and determining the target maximum beam angle θ for subsequent areas. t-max Steps and determination of the test grating pitch P t-grating steps.

14. The method according to claim 12, wherein: The step of obtaining the displacement angle Δθ comprises the following steps: reflecting the plurality of light beams away from the first region and onto an initial R0 light beam such that the initial R0 light beam is incident on a focusing lens at a first incident point that is spaced a first incremental distance Δ1 from the optical center of the focusing lens; and A first angle Δθ1 is determined based on the first incremental distance Δ1.

15. The method according to claim 14, wherein: The step of determining the first angle Δθ1 includes using the formula Δ1=f1*tan(Δθ1), where f1 is the focal length of the focusing lens.

16. The method according to claim 15, wherein the step of obtaining the displacement angle Δθ further comprises: Focusing the initial R0 light beam into a first R0 light beam by the focusing lens; Focusing the first R0 light beam into a second R0 light beam through a second focusing lens; focusing the second R0 beam into a third R0 beam by a third focusing lens, so that the third R0 beam is incident on the third focusing lens at a third incident point, so that the third incident point is separated from the optical center of the third focusing lens by a second incremental distance Δ2, and The first angle Δθ1 is determined from the second incremental distance Δ2 using the formula Δ2=f1*tan(Δθ1)*f3 / f2, where f2 is the focal length of the second focusing lens and f3 is the focal length of the third focusing lens. The method of claim 14 , wherein the first angle Δθ1 is in a range of about 0.001° to about 0.1°.

Images