Geometric parameter measurement method for optical grating

Abstract

The present disclosure relates to metrology measurement systems and related methods. In one or more embodiments, a system includes: a substrate support; and an optical arm. The optical arm includes a light source operable to project a first beam on a first optical path. The optical arm also includes a first lens, a first beam splitter, a second lens, a first detector, and a diaphragm. The first lens is disposed on the first optical path and between the substrate support and the light source. The first beam splitter is arranged on the first light path. The first beam splitter is positioned between the substrate support and the light source. And the first detector is arranged on the second light path. The second lens focuses a second beam to a second beam diameter. The diaphragm is disposed between the second lens and the first detector.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to measurement systems and methods for measuring properties of measurement optics. Background Art

[0002] Virtual reality is generally regarded as a computer-generated simulated environment in which a user has an apparent 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 having a near-eye display panel as a lens to display a virtual reality environment in place of the actual environment).

[0003] However, augmented reality enables an experience where a user can still view the surrounding environment through the display lens of glasses or other HMD devices, but also sees an image of a virtual object that is generated for display and appears to be part of that environment. Augmented reality can include any type of input that enhances or augments the environment experienced by the user, such as audio and tactile inputs, as well as virtual images, graphics, and video. As an emerging technology, augmented reality presents many challenges and design constraints.

[0004] One such challenge is to display virtual images superimposed on the surrounding environment. Optics are used to assist in the superimposed image. Fabricating the optics can be challenging because the optics often have properties that need to be manufactured according to specific tolerances, such as the spacing of the optical device structures and the orientation of the optical device structures. When measuring the optical device structures on an opaque substrate, due to the reflection and diffraction of light, conventional systems will experience a reduction in accuracy and repeatability. Therefore, there is a need in the art for improved devices and methods for measuring the properties of optical device structures with increased accuracy and repeatability. Summary of the Invention

[0005] The present disclosure relates to metrology measurement systems and related methods. In one or more embodiments, a system includes a substrate support and an optical arm. The optical arm includes a light source operable to project a first beam on a first optical path. The optical arm also includes a first lens, a first beam splitter, a second lens, a first detector, and a diaphragm. The first lens is disposed on the first optical path and between the substrate support and the light source. The first beam splitter is disposed on the first optical path. The first beam splitter is positioned between the substrate support and the light source. The first detector is disposed on a second optical path. The second lens focuses a second beam to a second beam diameter. The diaphragm is disposed between the second lens and the first detector.

[0006] In one or more embodiments, a system is provided. The system includes a substrate support, an optical arm, and a detector arm. The optical arm includes a light source, a first plurality of lenses, a first beam splitter, a first detector, and a first aperture. The light source is operable to project a first beam on a first optical path. The first plurality of lenses includes a first lens and a second lens. The first lens is disposed on the first optical path and between the substrate support and the light source, and the first lens is operable to focus the first beam to a beam diameter. The first beam splitter is disposed on the first optical path and between the substrate support and the light source. The first beam splitter is operable to allow the first beam to be projected on the substrate support on the first optical path and is operable to reflect a second beam on a second optical path. The first detector is disposed on the second optical path. The second lens of the first plurality of lenses is operable to focus the second beam to a second beam diameter. The first aperture is disposed on the second optical path between the second lens and the first detector. The aperture is operable to receive the second beam of the second beam diameter from the second lens. The detector arm includes a second plurality of lenses having a first lens and a second lens, a second aperture disposed between the first lens and the second lens of the second plurality of lenses, and a sensor. The second aperture is disposed on the reflected optical path. The sensor is disposed on the reflected optical path.

[0007] In one or more embodiments, a method is provided. The method includes rotating a substrate to position a plurality of gratings having an orientation angle perpendicular to a first optical path pointing to a first region of the substrate. The first region has a plurality of gratings disposed therein. The method further includes projecting a first beam at the first region, the first beam on the first optical path passing through a first lens to form a first beam diameter of the first beam at a first grating of the plurality of gratings. The method further includes reflecting the first beam from the first grating to form a second beam on a second optical path. The method further includes: passing the second beam through a second lens disposed on the second optical path, the second lens forming a second beam diameter; passing the second beam through a first aperture disposed on the second optical path, the first aperture receiving the second beam of the second beam diameter; passing the second beam through a third lens on the second optical path, the third lens disposed after the first aperture. The method further includes forming a first image of the second beam with a first detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] To enable a manner of understanding the features set forth above in detail, a more particular description of the disclosure briefly summarized above may be had by reference to the embodiments. However, it should be noted that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of the scope of the disclosure, and other equally effective embodiments are admitted.

[0009] Figure 1 is a schematic diagram of a measurement system according to an embodiment.

[0010] Figures 2A to 2DSchematic diagram of the configuration of a measurement system according to some embodiments.

[0011] Figure 3 Schematic diagram of the configuration of a measurement system according to some embodiments.

[0012] Figure 4 Flowchart of a method for measuring properties of an optical device according to some embodiments.

[0013] For ease of understanding, the same element symbols have been used as much as possible to label the common elements of each figure. It is contemplated that the elements and features of one embodiment can also be beneficially incorporated in other embodiments without further statement. Detailed Description

[0014] Embodiments of the present disclosure relate to a measurement system for an optical device. More specifically, the embodiments described herein provide metrology measurement systems and methods. The metrology measurement systems and methods are shown and described herein.

[0015] The system improves the accuracy of information derived from a grating by the features of the measurement components described herein. Prior art grating measurements are inaccurate due to factors such as non-local measurements. In other words, prior art grating measurements cannot accurately image a single grating orientation and pitch P ( Figure 2A ). Other grating measurement options also require destructive testing. Additionally, the design of the grating measurement component lacks rigidity, which results in optical noise during operation.

[0016] Figure 1 Schematic diagram of measurement system 101. As shown, measurement system 101 includes a substrate support 102, an optical arm 104, and a detector arm 112. Measurement system 101 is configured to diffract light projected by optical arm 104. The light projected by optical arm 104 is directed towards a substrate 103 disposed above substrate support 102. The light reflected and diffracted from substrate 103 is incident on optical arm 104 and is reflected to detector arm 112. In one embodiment combinable with other embodiments described herein, measurement system 101 includes optical arm 104 and detector arm 112. In another embodiment combinable with other embodiments described herein, measurement system 101 includes only optical arm 104.

[0017] As shown in the figure, the substrate support 102 includes a support surface 106 and a support actuator 108. The substrate support 102 is configured to hold the substrate 103 on the support surface 106. The substrate support 102 is coupled to the support actuator 108. The support actuator 108 is configured to move the substrate support 102 along the x-direction and the y-direction on the scan path 110, and rotate the substrate support 102 about the z-axis around the axis R1. The substrate support 102 is configured to move and rotate the substrate 103 during the operation of the measurement system 101 such that the light projected from the optical arm 104 can be incident on different parts or gratings of the substrate 103.

[0018] The substrate 103 includes one or more optical devices 105, and the one or more optical devices include one or more gratings 107 having an optical device structure 109. Each of the gratings 107 includes a region of the optical device structure 109. For example, the grating 107 may be in the first region 115. The optical device structure 109 has an orientation angle 265 (see Figure 2A ) and a pitch P (see Figure 2A ).

[0019] The pitch P is defined as the distance between adjacent points, such as adjacent first edges or adjacent mass centers of the optical device structure 109. The pitch P and the orientation angle 265 of the optical device structure 109 of the first grating 111 may be different from the pitch P and the orientation angle 265 of the optical device structure 109 of the second grating 113 in one or more gratings 107. Additionally, due to local warping or other deformations of the substrate 103, there may be local variations in the pitch P and local variations in the orientation angle 265 of the optical device structure 109. The measurement system 101 can be used to measure the pitch P and the orientation angle 265 of the optical device structure 109 in each of the gratings 107 in each of the optical devices 105. The substrate 103 can be a single wafer of any size (such as having a radius of about 150 mm to about 450 mm).

[0020] The optical arm 104, the detector arm 112, and the substrate support 102 are coupled to a controller 130. The controller 130 facilitates the control and automation of a method 400 for measuring the pitch P and the orientation angle 265 of the grating 107 of the optical device structure 109 described herein. The controller may include a central processing unit (CPU) (not shown), a memory (not shown), and support circuitry (or I / O) (not shown). The CPU can be any form of computer processor used in an industrial setting for controlling various processes and hardware (e.g., motors and other hardware) and monitoring these processes (e.g., transport device position and scan time). The memory (not shown) is connected to the CPU and can be an accessible memory such as random access memory (RAM). Software instructions and data can be encoded and stored in the memory to instruct the CPU. The support circuitry (not shown) is also connected to the CPU to support the processor in a conventional manner. The support circuitry can include conventional caches, power supplies, clock circuits, input / output circuitry, subsystems, and the like. The program readable by the controller (or computer instructions) determines the tasks programmable on the substrate 103. The program can be software readable by the controller and can include code for monitoring and controlling such things as substrate position and optical arm position.

[0021] The optical arm 104 is coupled to a first arm actuator 125. The first arm actuator 125 is configured to rotate the optical arm 104 about the substrate support 102. The optical arm 104 is coupled to the first arm actuator 125 by an optical arm rod 120. The first arm actuator 125 rotates the optical arm 104 above and around the substrate support 102 about an arm axis 140. According to some embodiments, the arm axis 140 is aligned with the substrate support surface 106.

[0022] The detector arm 112 is coupled to a second arm actuator 135. The second arm actuator 135 is configured to rotate the detector arm 112 about the substrate support 102. The detector arm 112 is coupled to the second arm actuator 135 by a detector arm rod 136. In some embodiments, the second arm actuator 135 rotates the detector arm 112 above and around the substrate support 102 about an arm axis 140. According to some embodiments, the arm axis 140 aligns the first arm actuator 125, the second arm actuator 135, and the substrate support surface 106 in the same plane.

[0023] Figures 2A to 2DIt is a schematic diagram of configurations 200A to 200D of the measurement system 101. In an embodiment where the substrate 103 is opaque and can be combined with other embodiments described herein, the reflection and diffraction of light from multiple surfaces of the substrate 103 will cause interference to the optical arm 104 and the detector arm 112. This interference is asymmetric, that is, the image of the optical path diffracted or reflected from the substrate 103 is not circular or substantially circular when reflected into the sensor in the optical arm 104. The sensor receives the image of the optical path diffracted or reflected from the substrate 103 on the sensors of the optical arm 104 and the detector arm 112, as further described below. To address this situation, the measurement system 101 utilizes one or more of the first beam splitter 211a, the second beam splitter 211b, the first plurality of lenses 220a, the second plurality of lenses 220b, the first aperture 260, the tilted aperture 263, and the second aperture 360. Multiple images are combined to generate a symmetric beam, that is, a circular beam. The centroid of the beam is determined using an image processing algorithm. The image processing algorithm can be executed at least in part by the controller 130. The optical arm 104 communicates with the controller 130. The optical arm 104 may include an arm actuator 203. The arm actuator 203 is configured to rotate the optical arm 104 about the z-axis and scan the optical arm in the z-direction. When performing measurements, the optical arm 104 can be fixed.

[0024] The controller is operable and configured to communicate with at least one or more of the first detector 208, the second detector 218, the third detector 217, and the sensor 308 ( Figure 3 ). The controller 130 is capable of imaging light and determining one or more grating properties based on the information received from the first optical path 231, the second optical path 232, the third optical path 233, and the reflected optical path 334. The grating properties include one or more of the grating pitch, the grating orientation, the problems caused by the non-uniformity of the substrate support surface 106, and the light intensity from the light source 204 and / or the light intensity of the reflection from the grating 107. The controller 130 is capable of executing method 400. Method 400 is stored in the memory of the controller. The CPU of the controller 130 can cause the CPU to send instructions to the measurement system 101 to execute method 400.

[0025] Figure 2A A schematic diagram of configuration 200A of the measurement system 101 is shown. Configuration 200A includes a portion 202 of the cross-sectional line 201 passing through the substrate 103 ( Figure 1 as shown). The substrate 103 includes one or more gratings 107 having an optical device structure 109. As shown, the optical arm 104 has a light source 204, a first plurality of lenses 220a, a first beam splitter 211, a first aperture 260, a first detector 208, and a second detector 218.

[0026] The light source 204 causes a first beam 271 to be projected onto a first optical path 231. The first beam 271 travels on the first optical path through a first photomask 207 and a polarizer 209. The light source 204 is operable to project a collimated beam of light.

[0027] The first plurality of lenses 220a includes a first lens 221, a second lens 222, and a third lens 223. The first lens 221 is on the first optical path 231. The first lens 221 is between the light source 204 and the substrate support 102. The first lens 221 focuses the first beam 271 into a first beam diameter 206. The first beam diameter 206 is disposed on the angled surface 261 of the grating 107. The angled surface 261 is set at an orientation angle 265. In one embodiment combinable with other embodiments described herein, the first optical path 231 has a circular or substantially circular cross-section. The first lens 221 is on the first optical path 231 after a first beam splitter 211.

[0028] The first lens 221 is operable to focus the first beam 271 into a first beam diameter 206. The first beam diameter 206 is between about 1 micron and about 15 microns, such as about 10 microns. The first beam diameter 206 is the focal point of the first lens 221. The first beam diameter 206 is directed at the angled surface 261 of the grating 107. The first beam 271 is focused as it passes through the first lens 221. Focusing the first beam 271 makes the measurement point the first beam diameter 206.

[0029] The first beam 271 is reflected from the angled surface 261 of the grating 107 onto a second optical path 232 to form a second beam 272. The first optical path 231 is incident on the substrate 103 and reflects the second optical path 232 back to the optical arm 104. In one embodiment combinable with other embodiments described herein, the second optical path 232 is a first-order diffraction. The first beam 271 is the beam before reflection from the substrate 103. The second beam 272 is the beam reflected from the substrate 103. A portion of the first optical path 231 becomes the second optical path 232 after reflection from the substrate 103. The second beam 272 is the light reflected from the substrate.

[0030] The first beam splitter 211 is disposed on the first optical path 231. The first beam splitter 211 is positioned on the first optical path 231 between the substrate support 102 and the light source 204. The beams described herein may be laser beams. According to one embodiment, the light source 204 is operable to project light at a beam angle A1 ( Figure 1 as shown) along the first optical path 231 onto the substrate 103.

[0031] The first beam splitter 211 is operable to allow the first beam 271 on the first optical path 231 to be directed at the substrate support to deflect the second beam 272 on the second optical path 232 from the substrate 103 to the first detector 208.

[0032] The first beam splitter 211 forms a third optical path 233 from the first optical path 231. The first beam splitter 211 is operable to deflect a second beam 272 on the second optical path 232 from the substrate 103 to the first detector 208.

[0033] The first detector 208 is disposed on the second optical path 232. A first image of the second optical path 232 is projected onto the first detector 208. The first detector 208 is any optical device in the art for detecting light, such as a CCD array or a CMOS array.

[0034] The second lens 222 is operable to focus the second beam 272 into a second beam diameter 269. The second beam diameter 269 is close to the focal point of the second lens 222. The first aperture 260 may be disposed where the second beam 272 becomes the second beam diameter 269. For example, the first aperture 260 is disposed at the focal point of the second lens 222. In one or more embodiments, the first aperture 260 is disposed between the focal point of the second lens 222 and the second lens 222. In some embodiments, the first aperture 260 is disposed between the second beam diameter 269 and the second lens 222. The first aperture 260 includes a mechanism for adjusting the first aperture 260 to maximize the effectiveness of the first aperture 260. For example, the first aperture 260 can be adjusted closer to or farther from the second lens 222. For example, the first aperture 260 is adjusted by angling the first aperture 260 with respect to the principal axis of the second beam 272. The first aperture 260 has a diameter of about 1 micron to about 50 microns. For example, the first aperture 260 has a diameter of about 5 microns to about 20 microns, such as about 15 microns.

[0035] The first aperture 260 is disposed on the second optical path 232 between the first beam splitter 211 and the first detector 208. The first aperture 260 is operable to rotate the second image at any angle. The first aperture 260 is operable to reduce noise caused by at least one or more of the first plurality of lenses 220a and / or reflections from surfaces that are not angled surfaces 261. Before contacting the first detector 208, the second optical path 232 passes through the first aperture 260. The first aperture 260 rotates the image of the second optical path 232 onto the first detector 208.

[0036] The third lens 223 is on the second optical path 232 between the first aperture 260 and the first detector 208. Thus, after passing through the third lens 223, the image of the second optical path 232 is projected onto the first detector 208. The third lens 223 collimates the second beam 272 after the second beam 272 passes through the first aperture 260. By collimating the second beam 272, the first detector 208 can capture and analyze changes in the light at least in terms of the pitch P and / or orientation of the grating 107.

[0037] The configuration of the second lens 222, the first aperture 260, and the third lens 223 enables the first detector 208 to receive filtered light. The filtered light refers to the light reflected from the angled surface 261 of the grating 107 and has less noise from the light reflected from other surfaces of the substrate 103 and the grating 107.

[0038] In one or more embodiments combinable with other embodiments, the optical arm 104 may further include a first mask 207 and a polarizer 209.

[0039] In one or more embodiments, the first mask 207 is on the first optical path 231. The first mask 207 adds a mark to the image of the first beam 271. In one or more embodiments, the polarizer 209 is disposed on the first optical path 231. The polarizer 209 polarizes the first beam 271.

[0040] In one or more embodiments, the first beam splitter 211 reflects a portion of the first beam 271 and / or a portion of the second beam 272 to the third optical path 233. The third optical path 233 directs the light to the second detector 218. The second detector 218 is a sensor, such as an integrating sphere. The second detector 218 improves the efficiency measurement of the grating 107. The second detector 218 can measure the rate of change of the height of the grating. The second detector 218 can measure the intensity and / or intensity of the reflection from the grating 107. The second detector 218 can measure the intensity of the light from the light source 204 to account for changes in the light source 204.

[0041] The first lens 221 enhances the resolution of the data collected from the light. The first lens 221 focuses the first beam 271 to a diameter smaller than that of the grating 107. Focusing the first beam 271 to a diameter smaller than that of the grating 107 enables each grating 107 to be analyzed at least in terms of the pitch P and orientation. Focusing the first beam 271 with the first lens 221 can enhance the spatial resolution by minimizing the surface area of the first beam 271 to be smaller than the size of the angled surface 261 of the grating 107.

[0042] The first aperture 260 is operable to reduce the second beam 272 to almost the light reflected from the angled surface 261. The first aperture 260 minimizes the amount of light received by the first detector 208 from the light not reflected from the angled surface 261 of the grating 107. Light noise from the light reflected from other surfaces may cause inaccurate readings. The first aperture 260 is operable to filter the noise from the light reflected from the grating 107 before the light is received by the first sensor.

[0043] By making the first aperture 260 perpendicular to the second beam 272, the first detector 208 can detect any change in the grating orientation. This configuration enables the first detector 208 to form a first image. The first image is used to detect changes in the grating orientation and pitch P. To ensure accurate information reception, the position of the aperture relative to the second lens 222 and / or the third lens 223 can be adjusted to ensure that the light received by the first detector is focused. The first aperture 260 operates as a conjugate plane, enabling the first detector 208 to have better lateral resolution. The first aperture 260 can also be operated to enhance the resolution in the direction perpendicular to the substrate 103 and the support surface 106.

[0044] The grating 107 has a pitch P. The pitch P is determined based on the distance between the gratings 107. The grating 109 has a duty cycle determined by dividing the line width of each grating by the pitch P.

[0045] Figure 2B is a schematic diagram of the configuration 200B of the measurement system 101. As shown, the optical arm 104 has a light source 204, a first plurality of lenses 220a, a first beam splitter 211, a first aperture 260, a first detector 208, a second detector 218, a first mask 207, and a polarizer 209.

[0046] Figure 2B The illustrated implementation includes a fourth lens 224 among the first plurality of lenses 220a. In some embodiments, the fourth lens 224 is disposed between the first beam splitter 311 and the second detector 218. The fourth lens 224 focuses the third beam 273 onto the second detector 218.

[0047] The fourth lens 224 is disposed on the third optical path 233. The fourth lens 224 is disposed between the first beam splitter 211 and the second detector 218. The fourth lens 224 focuses the light onto the second detector 218. By enabling the second detector 218 to receive focused light, the second detector 218 can use the image in the light as a reference to improve resolution and analyze non-collimated light. By analyzing the focused light, the second detector can provide a reference for the light having a second beam diameter 269 at the first aperture 260.

[0048] Figure 2C is a schematic diagram of the configuration 200C of the measurement system 101. As shown, the optical arm 104 has a light source 204, a first plurality of lenses 220a, a first beam splitter 211, a first detector 208, and a second detector 218. The implementation shown in FIG. 2 also includes a tilted aperture 263 and a fifth lens 225 among the first plurality of lenses 220a.

[0049] As shown, the first beam diameter 206 points to the top surface 267. In some embodiments, the top surface 267 is angled with respect to the angled surface 261 of the grating 107 (Figure 2B at an angle of inclination 266. In some embodiments, the top surface 267 may also be at an angle of inclination 266 with respect to the vertical plane formed by the first beam 271.

[0050] The tilted aperture 263 is disposed between the second lens 222 and the third lens 223. The tilted aperture 263 is disposed on the second optical path 232, after the second lens 222 and after the first beam splitter 211. When the first lens 221 is focused on the top surface 267 of the grating 107, the first beam 271 is not perpendicular to the top surface 267. The first beam 271 is projected at the top surface 267 at an angle of inclination 266.

[0051] The tilted aperture 263 is at an angle of inclination 266. Angling the tilted aperture 263 enables the first detector 208 to analyze the reflected light when the first beam 271 is not perpendicular to the surface being measured.

[0052] Figure 2C The illustrated implementation also moves the first lens 221. The first lens 221 is disposed between the light source 204 and the first beam splitter 211. Moving the first lens 221 before the first beam splitter 211 can increase the ratio of filtered light to noise received by the first detector 208.

[0053] The fifth lens 225 is disposed between the first beam splitter 211 and the second lens 222. The fifth lens is on the second optical path 232. The fifth lens 225 receives and collimates the second beam 272.

[0054] Figure 2C The illustrated implementation may also include a first mask 207a and a second mask 207b. The first mask 207a and the second mask 207b enhance the measurement capabilities of the measurement system 101.

[0055] Figure 2D is a schematic diagram of the configuration 200D of the measurement system 101. As shown, the optical arm 104 includes a light source 204, a first plurality of lenses 220a, a first detector 208, and a second detector 218. Figure 2D The illustrated implementation also includes a tilted aperture 263, a third detector 217, a first beam splitter 211a, a second beam splitter 211b, and a sixth lens 226 of the first plurality of lenses 220a.

[0056] The second beam splitter 211b is disposed on the second optical path 232 after the tilted aperture 263. The second beam splitter 211b directs a portion of the second beam 272 to the first detector 208 and a portion of the second beam 272 to the third detector 217. The third lens 223 is disposed on the second optical path 232 between the first detector 208 and the second beam splitter 211b.

[0057] The sixth lens 226 among the first plurality of lenses 220a is disposed between the third detector 217 and the second beam splitter 211b on the second optical path 232. The sixth lens 226 ensures that light is fully collected by the third detector 217. In one or more embodiments, the sixth lens 226 is a low-power lens such that when the third detector 217 is disposed at a relatively far distance from the tilt aperture 263, the third detector 217 can receive light from the tilt aperture 263.

[0058] In one or more embodiments, the third detector 217 is disposed at a tilt angle 266. In other embodiments, the third detector 217 is disposed at another angle to enhance image quality or focus. In other embodiments, the third detector 217 is disposed perpendicular to the second beam 272. The third detector 217 enables simultaneous imaging of the surface of the substrate 103 and the top surface 267 of the grating 107. Concurrent analysis enables enhanced alignment of the system and monitors changes in focus during measurement operations.

[0059] Figure 3 is a schematic diagram of the configuration 300 of the measurement system 101. As shown, the optical arm 104 includes Figure 2D a configuration having a detector arm 112.

[0060] The detector arm 112 includes a second plurality of lenses 320. The second plurality of lenses 320 includes a first lens 327, a second lens 328, and a third lens 329.

[0061] The detector arm 112 includes a second aperture 360. The second aperture 360 is disposed between the first lens 327 and the second lens 328 among the second plurality of lenses 320. The second aperture 360 is disposed on the reflection optical path 334.

[0062] The detector arm 112 includes a sensor 308. The sensor 308 is disposed on the reflection optical path 334.

[0063] The arrangement of the second aperture 360 between the second lens 328 and the third lens 329 among the second plurality of lenses 320 is operable to filter optical noise before the third beam 373 reaches the sensor 308. In some embodiments, the second aperture 360 is disposed perpendicular to the third beam 373. In other embodiments, the second aperture 360 is disposed at an angle with respect to the third beam 373.

[0064] In some embodiments, the third beam 373 is light oriented parallel to the grating 107. In other embodiments, the third beam 373 is light at an angle to the surface of the grating 107. The sensor 308 reads and images the third beam 373 so that the measurement system 101 can determine the properties of any non-uniformities of the support surface 106 of the substrate support 102. Understanding whether the problem is caused by the support surface 106 or the grating 107 helps improve the efficiency of the measurement system 101.

[0065] The third beam 373 moves on the reflection optical path 334 towards the detector arm 112 to the sensor 308. The detector arm 112 enables the analysis of the substrate support 102. The detector arm 122 is used to measure the deflection of the third beam 373. The third beam 373 is light reflected from the grating 107. For example, the third beam 373 is light reflected from one or more of the angled surface 261 of the grating 107, the top surface 267 of the grating 107, the support surface 106 of the substrate support 102, the surface of the substrate 103, or any combination thereof.

[0066] Figure 4 is a flowchart for measuring the properties of the optical device structure 109 according to some embodiments. At operation 401, the substrate 103 is rotated to position the plurality of gratings 107 of the optical device structure 109. The grating 107 has an orientation angle 265 and a pitch P ( Figure 2A ). The substrate 103 is rotated to a desired position. For example, the substrate 103 is rotated such that the orientation angle 265 is approximately perpendicular to the light beam. In some embodiments, the light beam is at an angle to the orientation angle 265 of the grating 107. In some embodiments, the light beam is the first beam 271. The first beam 271 is directed to the first region 115 of the substrate. The first region 115 includes a plurality of gratings 107 disposed therein.

[0067] At operation 403, the first beam 271 is projected at the first region 115. The first beam 271 is on the first optical path 231. The first beam 271 passes through the first lens 221 to form a first beam diameter 206 of the first beam 271. The first beam 271 of the first beam diameter 206 is directed to the first grating 111 among the plurality of gratings 107 ( Figure 1 ).

[0068] The first beam 271 is reflected from the first grating among the gratings 107. The reflected beam forms the second beam 272. The second beam 272 is on the second optical path 232.

[0069] The light source 204 generates a first beam 271 and initiates a first optical path 231. The first beam 271 is focused by a first lens 221. The first lens 221 can be on the first optical path 231 either before or after the first beam splitter 211. In one or more embodiments, the first beam 271 travels to the first beam splitter 211, and a portion of the first beam 271 becomes a third beam 273. The third beam is directed to a second detector 218 on a third optical path 233. In one or more embodiments, a second beam 272 travels to the first beam splitter 211, and a portion of the second beam 272 becomes the third beam 273. The third beam is directed to the second detector 218 on the third optical path 233.

[0070] At operation 405, the second beam 272 is passed through a second lens 222. The second lens 222 is disposed on a second optical path 232. The second lens 222 forms a second beam diameter 269 from the second beam. The second beam diameter 269 can be approximately equal to the first beam diameter 206.

[0071] At operation 407, the second beam 272 is passed through a first aperture 260. The first aperture 260 is disposed on the second optical path 232. The first aperture 260 receives the second beam 272. In some embodiments, the second beam 272 passes through the first aperture 260 when the second beam 272 reaches the second beam diameter 269 through the second lens 222. In other embodiments, the second beam 272 reaches the first aperture 260 before the second beam 272 reaches the second beam diameter 269. In one or more embodiments, the first aperture 260 is perpendicular to the second beam 272. In other embodiments, the first aperture 260 is an inclined aperture 263. The inclined aperture 263 is angled with respect to the second beam 272 at an inclination angle 266.

[0072] At operation 409, the second beam 272 is passed through a third lens 223. The third lens 223 is on the second optical path 232. The third lens is disposed on the second optical path 232 after the first aperture 260. The third lens 223 receives the focused second beam 272 from the first aperture 260 and collimates the second beam 272.

[0073] At operation 411, a first image is formed from the second beam 272 by at least a first detector 208. In one or more embodiments, the first image is formed by one or more of the first detector 208, the second detector 218, the sensor 308, and the controller 130. The first detector 208 receives the collimated light from the third lens 223. The first image includes information about the grating 107. The first image provides at least one or more of the grating pitch P, the grating orientation, and the grating depth.

[0074] In some embodiments, the first image is also formed using one or more of the second detector 218, the third detector 217, the sensor 308, and the controller 130. The first image can provide information about the grating 107. This information includes one or more of the grating pitch P, the grating orientation, the reflectance intensity of the grating, and the grating depth.

[0075] Benefits of the present disclosure include improved resolution of the grating. The first lens focuses light to a much smaller spot to enable local grating analysis. Passing the focused light through the first aperture helps minimize noise caused by light reflected from other surfaces.

[0076] It is contemplated that one or more aspects disclosed herein can be combined. As an example, Figures 2A to 2D the optical arm 104, the first lens 221, the second lens 222, the third lens 223, the first aperture 260, the tilt aperture 263, the first detector 208, the second detector 218, and the third detector 217, Figure 3 the detector arm 112, the first lens 327, the second lens 328, the third lens 329, the second aperture 360, and the sensor 308 and / or Figure 4 one or more aspects, features, components, operations, and / or properties of the method 400 therein can be combined. Additionally, it is contemplated that one or more aspects disclosed herein can include some or all of the above benefits.

[0077] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure can be conceived without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the appended claims.

Claims

1. A system, the system comprising: A substrate support; And An optical arm, the optical arm comprising: A light source operable to project a first beam on a first optical path; A first lens disposed on the first optical path and between the substrate support and the light source, the first lens operable to focus the first beam to a first beam diameter; A first beam splitter disposed on the first optical path, the first beam splitter positioned on the first optical path between the substrate support and the light source, the first beam splitter operable to allow the first beam to be projected onto the substrate support on the first optical path and operable to reflect a second beam on a second optical path; A first detector disposed on the second optical path; A second lens operable to focus the second beam to a second beam diameter; and An aperture disposed on the second optical path between the second lens and the first detector.

2. The system of claim 1, the system further comprising a controller in communication with the first detector, the controller configured to measure grating properties based on information received from at least the second optical path.

3. The system of claim 1, wherein the first lens is on the first optical path between the first beam splitter and the light source.

4. The system of claim 1, wherein the first beam splitter is on the first optical path between the first lens and the light source.

5. The system of claim 1, wherein the aperture is disposed at an inclined angle with respect to the second optical path.

6. The system of claim 5, wherein the first detector is disposed at the inclined angle.

7. The system of claim 1, the system further comprising a second detector disposed on a third optical path that is reflected from the first beam splitter before the first beam passes through the first beam splitter.

8. The system of claim 1, the system further comprising a second lens on the second optical path between the aperture and the first beam splitter.

9. The system of claim 8, the system further comprising a third lens on the second optical path between the aperture and the first detector.

10. The system of claim 1, the system further comprising a mask between the light source and the first beam splitter.

11. The system of claim 1, the system further comprising a third detector disposed at an angle with respect to the second beam.

12. The system of claim 11, the system further comprising a second beam splitter on the second optical path after the aperture, the second beam splitter disposed before the first detector and the third detector.

13. A system, the system comprising: A substrate support; An optical arm having: A light source operable to project a first beam on a first optical path; A first plurality of lenses, the first plurality of lenses having a first lens, the first lens being on the first optical path and disposed between the substrate support and the light source, the first lens being operable to focus the first beam to a beam diameter; A first beam splitter, the first beam splitter being disposed on the first optical path, the first beam splitter being positioned between the substrate support and the light source, the first beam splitter being operable to allow the first beam to be projected onto the substrate support on the first optical path and being operable to reflect a second beam on a second optical path; A first detector, the first detector being disposed on the second optical path; A second lens of the first plurality of lenses, the second lens being operable to focus the second beam to a second beam diameter; A first aperture, the first aperture being disposed on the second optical path between the second lens and the first detector, the first aperture being operable to receive the second beam of the second beam diameter from the second lens; And A detector arm, the detector arm comprising: A second plurality of lenses, the second plurality of lenses having a first lens and a second lens; A second aperture, the second aperture being disposed between the first lens and the second lens of the second plurality of lenses, the second aperture being disposed on a reflected optical path; and A sensor, the sensor being on the reflected optical path.

14. The system of claim 13, wherein the first aperture is disposed at an inclined angle with respect to the second beam.

15. The system of claim 14, wherein the second aperture is disposed at the inclined angle with respect to the second beam.

16. The system of claim 13, the system further comprising a second lens of the first plurality of lenses, the second lens being disposed on the second beam between the first aperture and the first beam splitter.

17. The system according to claim 13, wherein, The substrate support is disposed between the optical arm and the detector arm.

18. A method, the method comprising: Rotating a substrate to position a plurality of gratings having an orientation angle perpendicular to a first optical path pointing to a first region of the substrate, the first region having the plurality of gratings disposed therein; Projecting a first beam at the first region, the first beam on the first optical path passing through a first lens to form a first beam diameter of the first beam at a first grating of the plurality of gratings; Reflecting the first beam from the first grating to form a second beam on a second optical path; Passing the second beam through a second lens disposed on the second optical path, the second lens forming a second beam diameter; Passing the second beam through a first aperture disposed on the second optical path, the first aperture receiving the second beam of the second beam diameter; Passing the second beam through a third lens on the second optical path, the third lens being disposed after the first aperture; And Forming a first image from the second beam with a first detector.

19. The method of claim 18, wherein the first beam diameter of the first lens points to an angled surface of the first grating.

20. The method according to claim 18, wherein the first beam diameter of the first lens is directed to the top surface of the first grating.

Images