Methods of geometrical parameter measurement for optical gratings

Abstract

The present disclosure relates to a metrology measurement system and an associated method. In one or more embodiments, the system includes a substrate support and an optical arm. The optical arm includes a light source operable to project a first beam onto a first optical path. The optical arm also includes a first lens, a first beam splitter, a second lens, a first detector, and an aperture. 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 the second optical path. The second lens focuses the second beam to a second beam diameter. The aperture is disposed between the second lens and the first detector.

Description

[Technical Field]

[0001] SUMMARY Embodiments of the present disclosure relate to measurement systems and methods for measuring attributes of optical devices. [Background technology]

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has an apparent physical presence. Virtual reality experiences can be generated and viewed in 3D with 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 real environment.

[0003] Augmented reality, however, enables an experience in which the user still sees the surrounding environment through the display lenses of the glasses or other HMD device, and also sees images of 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 haptic input, as well as virtual images, graphics, and video that enhance or augment the environment the user experiences. As an emerging technology, there are many challenges and design constraints associated with augmented reality.

[0004] One such challenge is displaying a virtual image that is superimposed on a surrounding environment. Optical devices are used to assist in superimposing the image. Fabricating optical devices can be difficult because optical devices tend to have properties such as optical device structure pitch and optical device structure orientation that must be manufactured according to specific tolerances. Conventional systems will experience reduced accuracy and repeatability when measuring optical device structures on transparent substrates due to light reflection and diffraction. Therefore, what is needed in the art are improved apparatus and methods for measuring attributes of optical device structures with increased accuracy and repeatability. Summary of the Invention

[0005] The present disclosure relates to a metrology measurement system and an associated method. In one or more embodiments, the system includes a substrate support and an optical arm. The optical arm includes a light source operable to project a first beam onto a first optical path. The optical arm also includes a first lens, a first beam splitter, a second lens, a first detector, and an aperture. The first lens is disposed on the first optical path 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 the second optical path. The second lens focuses the second beam to a second beam diameter. The aperture 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 onto a first optical path. The first plurality of lenses includes a first lens and a second lens. The first lens is provided on the first optical path and is provided between the substrate support and the light source, and is operable to focus the first beam to a beam diameter. The first beam splitter is provided on the first optical path and is positioned on the first optical path between the substrate support and the light source. The first beam splitter is operable to allow the first beam projected onto the first optical path to the substrate support and is operable to reflect the second beam onto a second optical path. The first detector is provided on the second optical path. A second lens of the first plurality of lenses is operable to focus the second beam to a second beam diameter. A first aperture is provided on a second optical path between the second lens and the first detector. The aperture is operable to receive the second beam diameter of the second beam from the second lens. The detector arm includes a second plurality of lenses having a first lens and a second lens, a second aperture provided between the first lens and the second lens of the second plurality of lenses, and a sensor. The second aperture is provided on the reflected optical path. The sensor is provided 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 light path directed toward a first zone of the substrate. The first zone has a plurality of gratings disposed therein. The method also includes projecting a first beam into the first zone, the first beam on the first light 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 also includes reflecting the first beam from the first grating to form a second beam on a second light path. The method also includes passing the second beam through a second lens on the second optical path, the second lens forming a second beam diameter, passing the second beam through a first aperture on the second optical path, the first aperture receiving the second beam diameter of the second beam, and passing the second beam through a third lens on the second optical path, the third lens being located after the first aperture. The method also includes forming a first image from the second beam with a first detector.

[0008] A more particular description of the present disclosure briefly summarized above can be made by reference to embodiments so that the manner in which the features of the present disclosure are recited above can be understood in detail. It should be noted, however, that the drawings illustrate only illustrative embodiments and therefore should not be considered limiting of the scope thereof, which may be susceptible to other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a measurement system according to an embodiment. [Figure 2A] 1 is a schematic diagram of a measurement system configuration, according to some embodiments. [Figure 2B] 1 is a schematic diagram of a measurement system configuration, according to some embodiments. [Figure 2C]1 is a schematic diagram of a measurement system configuration, according to some embodiments. [Figure 2D] 1 is a schematic diagram of a measurement system configuration, according to some embodiments. [Figure 3] 1 is a schematic diagram of a measurement system configuration, according to some embodiments. [Figure 4] FIG. 1 is a flow diagram of a method for measuring attributes of an optical device, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] For ease of understanding, the same reference numerals have been used, wherever 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.

[0011] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to measurement systems for optical devices. More particularly, embodiments described herein provide metrology measurement systems and methods. A metrology measurement system and method are shown and described herein.

[0012] The system enhances the accuracy of information derived from the grating through the features of the measurement assembly described herein. Prior grating measurements were inaccurate due to factors such as non-local measurements. In other words, prior grating measurements were unable to accurately image a single grating orientation and pitch P (FIG. 2A). Other grating measurement options also required destructive testing. Additionally, grating measurement assemblies utilized designs that lacked rigidity and introduced optical noise during operation.

[0013] 1 is a schematic diagram of a measurement system 101. As shown, the measurement system 101 includes a substrate support 102, an optical arm 104, and a detector arm 112. The measurement system 101 is configured to diffract light projected by the optical arm 104. The light projected by the optical arm 104 is directed toward a substrate 103 disposed over the substrate support 102. Light reflected and diffracted from the substrate 103 is incident on the optical arm 104 and reflected to the detector arm 112. In one embodiment, which may be combined with other embodiments described herein, the measurement system 101 includes the optical arm 104 and the detector arm 112. In another embodiment, which may be combined with other embodiments described herein, the measurement system 101 includes only the optical arm 104.

[0014] As shown, the substrate support 102 includes a support surface 106 and a support actuator 108. The substrate support 102 is configured to hold a 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 in a scan path 110 along the x and y directions and to rotate the substrate support 102 about axis R1 and about the z axis. The substrate support 102 is configured to move and rotate the substrate 103 such that light projected from the optical arm 104 is incident on different portions or gratings of the substrate 103 during operation of the measurement system 101.

[0015] The substrate 103 includes one or more optical devices 105 having one or more gratings 107 of optical device structures 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 zone 115. The optical device structure 109 has an orientation angle 265 (FIG. 2A) and a pitch P (FIG. 2A).

[0016] The pitch P is defined as the distance between adjacent points, such as adjacent first edges or adjacent centers of mass, of the optical device structures 109. The pitch P and orientation angle 265 of the optical device structures 109 for the first grating 111 can be different from the pitch P and orientation angle 265 of the optical device structures 109 for the second grating 113 of one or more gratings 107. In addition, there may be local pitch P variations and local orientation angle 265 variations of the optical device structures 109 due to local warpage or other deformations of the substrate 103. The measurement system 101 can be utilized to measure the pitch P and orientation angle 265 of the optical device structures 109 for each of the gratings 107 of each of the optical devices 105. The substrate 103 can be a single crystal wafer of any size, such as having a radius of about 150 mm to about 450 mm.

[0017] The optical arm 104, the detector arm 112, and the substrate support 102 are coupled to a controller 130. The controller 130 facilitates control and automation of the method 400 for measuring the pitch P and 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), 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 device position and scan time). The memory (not shown) is connected to the CPU and may be a readily available memory such as random access memory (RAM). Software instructions and data can be coded 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 cache, power supplies, clock circuits, input / output circuitry, subsystems, etc. A program (or computer instructions) readable by the controller determines which tasks can be performed on the substrate 103. The program may be software readable by the controller and may include, for example, code that monitors and controls the substrate position and the optical arm position.

[0018] 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 bar 120. The first arm actuator 125 rotates the optical arm 104 about an arm axis 140 and about the substrate support 102. The arm axis 140 is aligned with the substrate support surface 106 according to some embodiments.

[0019] 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 bar 136. In some embodiments, the second arm actuator 135 rotates the detector arm 112 about an arm axis 140 and about the substrate support 102. The arm axis 140, according to some embodiments, aligns the first arm actuator 125, the second arm actuator 135, and the substrate support surface 106 in the same plane.

[0020] 2A-2D are schematic diagrams of configurations 200A-200D of measurement system 101. In embodiments in which substrate 103 is transparent, which can be combined with other embodiments described herein, reflection and diffraction of light from multiple surfaces of substrate 103 will cause interference in optical arm 104 and detector arm 112. The interference is asymmetric, i.e., the image of the light path diffracted or reflected from substrate 103 is not circular or substantially circular when reflected to the sensor in optical arm 104. The sensor receives the image of the light path diffracted or reflected from substrate 103 on the sensor in optical arm 104 and detector arm 112, as described further below. To address this, measurement system 101 utilizes one or more of a first beam splitter 211a, a second beam splitter 211b, a first plurality of lenses 220a, a second plurality of lenses 220b, a first aperture 260, an angled aperture 263, and a second aperture 360. The multiple images are combined to produce a symmetrical, i.e., circular, beam. The center of gravity of the beam is determined using an image processing algorithm. The image processing algorithm may be at least partially performed by the controller 130. The optical arm 104 is in communication 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. The optical arm 104 may be fixed while measurements are taken.

[0021] The controller 130 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 ( FIG. 3 ). The controller 130 can image the light and determine one or more grating attributes based on information received from the first light path 231, the second light path 232, the third light path 233, and the reflected light path 334. The grating attributes include one or more of the grating pitch, the grating orientation, issues caused by non-uniformity in the substrate support surface 106, and the light intensity from reflections from the light source 204 and / or the grating 107. The controller 130 can perform a method 400. The method 400 is stored in the memory of the controller. A CPU of the controller 130 can send instructions to the measurement system 101 to perform the method 400.

[0022] 2A is a schematic diagram of a configuration 200A of the measurement system 101. The configuration 200A includes a portion 202 of a cross-section line 201 (shown in FIG. 1) across a substrate 103. The substrate 103 has one or more gratings 107 of an optical device structure 109. As shown, the optical arm 104 includes 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.

[0023] The light source 204 projects a first beam 271 onto a first light path 231. The first beam 271 travels along the first light path through a first reticle 207 and a polarizer 209. The light source 204 is operable to project a parallel beam of light.

[0024] 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 a 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 provided on an oblique surface 261 of the grating 107. The oblique surface 261 is provided at an orientation angle 265. In one embodiment, which can be combined 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 the first beam splitter 211.

[0025] The first lens 221 is operable to focus the first beam 271 to a first beam diameter 206. The first beam diameter 206 is between about 1 micrometer and about 15 micrometers, for example, about 10 micrometers. The first beam diameter 206 is the focal point of the first lens 221. The first beam diameter 206 is directed toward the oblique surface 261 of the grating 107. The first beam 271 is focused as the beam passes through the first lens 221. Focusing the first beam 271 causes the measurement point to have the first beam diameter 206.

[0026] The first beam 271 is reflected from the oblique surface 261 of the grating 107 to form the second beam 272 in the second optical path 232. 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, which can be combined with other embodiments described herein, the second optical path 232 is a first-order diffraction. The first beam 271 is a light ray before being reflected from the substrate 103. The second beam 272 is a 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 light reflected from the substrate.

[0027] A first beam splitter 211 is provided 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 light beam described herein can be a laser beam. The light source 204, according to one embodiment, is operable to project light along the first optical path 231 onto the substrate 103 at a beam angle A1 (shown in FIG. 1 ).

[0028] The first beam splitter 211 is operable to allow a first beam 271 on a first optical path 231 to be directed towards the substrate support and to deflect a second beam 272 on a second optical path 232 from near the substrate 103 to a first detector 208.

[0029] 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 the second beam 272 on a second optical path 232 from beside the substrate 103 to the first detector 208.

[0030] The first detector 208 is provided on the second light path 232. A first image of the second light path 232 is projected onto the first detector 208. The first detector 208 is any optical instrument used in the art to detect light, such as a CCD array or a CMOS array.

[0031] The second lens 222 is operable to focus the second beam 272 to a second beam diameter 269. The second beam diameter 269 is proximate to the focal point of the second lens 222. The first aperture 260 may be provided where the second beam 272 will be at the second beam diameter 269. For example, the first aperture 260 is provided at the focal point of the second lens 222. In one or more embodiments, the first aperture 260 is provided between the focal point of the second lens 222 and the second lens 222. In some embodiments, the first aperture 260 is provided 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 is adjusted closer to or farther from the second lens 222. For example, the first aperture 260 is adjusted by angling the first aperture 260 from the major axis of the second beam 272. The first aperture 260 has a diameter of about 1 micrometer to about 50 micrometers. For example, the first aperture 260 has a diameter of about 5 micrometers to about 20 micrometers, e.g., about 15 micrometers.

[0032] The first aperture 260 is provided 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 by any angle. The first aperture 260 is operable to reduce noise caused by reflections from at least one or more lenses of the first plurality of lenses 220a and / or surfaces other than the bevel 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 on the first detector 208.

[0033] The third lens 223 is on the second light path 232 between the first aperture 260 and the first detector 208. Thus, an image of the second light path 232 is projected onto the first detector 208 after passing through the third lens 223. The third lens 223 collimates the second beam 272 after it passes through the first aperture 260. By collimating the second beam 272, the first detector 208 can image and analyze the light with respect to changes in at least the pitch P and / or orientation of the grating 107.

[0034] The arrangement of second lens 222, first aperture 260, and third lens 223 allows first detector 208 to receive filtered light. The filtered light is light reflected from oblique surface 261 of grating 107 and has less noise from light reflected from other surfaces of substrate 103 and grating 107.

[0035] In one or more embodiments, which may be combined with other embodiments, the optical arm 104 may also include a first reticle 207 and a polarizer 209 .

[0036] In one or more embodiments, a first reticle 207 is provided on the first light path 231. The first reticle 207 adds markers to the image of the first beam 271. In one or more embodiments, a polarizer 209 is provided on the first light path 231. The polarizer 209 polarizes the first beam 271.

[0037] In one or more embodiments, first beam splitter 211 reflects a portion of first beam 271 and / or a portion of second beam 272 into third optical path 233. Third optical path 233 directs the light toward second detector 218. Second detector 218 is a sensor, such as an integrating sphere. Second detector 218 enhances the efficiency measurement of grating 107. Second detector 218 may measure the rate of change of grating height. Second detector 218 may measure the magnitude and / or intensity of the reflection from grating 107. Second detector 218 may measure the intensity of light from light source 204 to account for fluctuations from light source 204.

[0038] The first lens 221 enhances the resolution of the data obtained from the light. The first lens 221 focuses the first beam 271 to a diameter smaller than the gratings 107. Focusing the first beam 271 to a diameter smaller than the gratings 107 allows each grating 107 to be analyzed with respect to at least the pitch P and the orientation. Focusing the first beam 271 with the first lens 221 enhances the spatial resolution by minimizing the surface area of ​​the first beam 271 to a size smaller than the slope 261 of the grating 107.

[0039] The first aperture 260 operates to reduce the second beam 272 to mostly light reflected from the beveled surface 261. The first aperture 260 minimizes the amount of light received by the first detector 208 from light that is not reflected from the beveled surface 261 of the grating 107. Noise from light reflected from other surfaces can cause inaccurate readings. The first aperture 260 operates to filter noise from the light reflected from the grating 107 before the light is received by the first sensor.

[0040] By orienting the first aperture 260 perpendicular to the second beam 272, the first detector 208 can detect any changes in the grating orientation. This configuration allows 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 is received, 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 acts as a conjugate plane so that the first detector 208 has better lateral resolution. The first aperture 260 also acts to enhance resolution in a direction perpendicular to the substrate 103 and support surface 106.

[0041] Gratings 107 have a pitch P. The pitch P is determined from the distance between gratings 107. Gratings 109 have a duty cycle determined by dividing the linewidth of each grating by the pitch P.

[0042] 2B is a schematic diagram of configuration 200B of measurement system 101. As shown, optical arm 104 includes 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 reticle 207, and a polarizer 209.

[0043] 2B includes a fourth lens 224 of 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.

[0044] A fourth lens 224 is provided on the third optical path 233. The fourth lens 224 is provided between the first beam splitter 211 and the second detector 218. The fourth lens 224 focuses the light onto the second detector 218. By having the second detector 218 receive the focused light, the second detector 218 can use an image in the light as a reference to improve resolution and analyze the non-collimated light. By analyzing the focused light, the second detector may provide a reference for the light at the second beam diameter 269 at the first aperture 260.

[0045] 2C is a schematic diagram of configuration 200C of measurement system 101. As shown, optical arm 104 includes light source 204, first plurality of lenses 220a, first beam splitter 211, first detector 208, and second detector 218. The implementation shown in FIG. 2C also includes angled aperture 263 and fifth lens 225 of first plurality of lenses 220a.

[0046] As shown, first beam diameter 206 is directed toward top surface 267. In some embodiments, top surface 267 is angled at tilt angle 266 from oblique surface 261 (FIG. 2B) of grating 107. In some embodiments, top surface 267 may also be angled at tilt angle 266 from a vertical plane formed by first beam 271.

[0047] The tilted aperture 263 is provided between the second lens 222 and the third lens 223. The tilted aperture 263 is provided 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 onto the top surface 267 at an oblique angle 266.

[0048] The oblique aperture 263 is angled at an oblique angle 266. Angling the oblique aperture 263 allows the first detector 208 to analyze the reflected light when the first beam 271 is not perpendicular to the surface being measured.

[0049] 2C 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 enhances the ratio of filtered light to noise received by the first detector 208.

[0050] 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.

[0051] 2C may also include a first reticle 207a and a second reticle 207b, which enhance the measurement capabilities of the measurement system 101.

[0052] 2D is a schematic diagram of a 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. The implementation shown in FIG. 2D 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.

[0053] A second beam splitter 211b is provided on the second optical path 232 after the angled 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. A third lens 223 is provided on the second optical path 232 between the first detector 208 and the second beam splitter 211b.

[0054] A sixth lens 226 of the first plurality of lenses 220a is disposed on the second light path 232 between the third detector 217 and the second beam splitter 211b. 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 magnification lens so that the third detector 217 can receive light from the angled aperture 263 when the third detector 217 is disposed far from the angled aperture 263.

[0055] In one or more embodiments, the third detector 217 is positioned at an oblique angle 266. In other embodiments, the third detector 217 is positioned at another angle to enhance image quality or focus. In other embodiments, the third detector 217 is positioned perpendicular to the second beam 272. The implementation of the third detector 217 allows for simultaneous imaging of the surface of the substrate 103 and the top surface 267 of the grating 107. Parallel analysis allows for enhanced alignment of the system and monitoring changes in focus during the measurement operation.

[0056] 3 is a schematic diagram of a configuration 300 of the measurement system 101. As shown, the optical arm 104 includes the configuration of FIG.

[0057] 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.

[0058] The detector arm 112 includes a second aperture 360. The second aperture 360 ​​is located between a first lens 327 and a second lens 328 of the second plurality of lenses 320. The second aperture 360 ​​is located on the reflected light path 334.

[0059] The detector arm 112 includes a sensor 308. The sensor 308 is disposed on the reflected light path 334.

[0060] The placement of the second aperture 360 ​​between the second lens 328 and the third lens 329 of the second plurality of lenses 320 is operable to filter out 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 to the third beam 373.

[0061] In some embodiments, the third beam 373 is light parallel to the orientation of the grating 107. In other embodiments, the third beam 373 is light angled away from the surface of the grating 107. The sensor 308 reads and images the third beam 373, allowing the measurement system 101 to determine attributes of any non-uniformity in the support surface 106 of the substrate support 102. Knowing whether the problem is caused by the support surface 106 or the grating 107 enhances the efficiency of the measurement system 101.

[0062] The third beam 373 travels along a reflected light path 334 towards the detector arm 112 to the sensor 308. The detector arm 112 enables analysis of the substrate support 102. The detector arm 122 is used to measure the polarization 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 oblique 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.

[0063] 4 is a flow diagram of a method for measuring attributes of an optical device structure 109, according to some embodiments. In operation 401, the substrate 103 is rotated to position a plurality of gratings 107 of the optical device structure 109. The gratings 107 have an orientation angle 265 and a pitch P (FIG. 2A). The substrate 103 is rotated to a desired position. For example, the substrate 103 is rotated so that the orientation angle 265 is approximately perpendicular to the light beam. In some embodiments, the light beam is at an angle from the orientation angle 265 of the grating 107. In some embodiments, the light beam is a first beam 271. The first beam 271 is directed toward a first zone 115 of the substrate. The first zone 115 includes a plurality of gratings 107 disposed therein.

[0064] In operation 403, a first beam 271 is projected onto a first zone 115. The first beam 271 is in a first optical path 231. The first beam 271 passes through a first lens 221 to form a first beam diameter 206 of the first beam 271. The first beam diameter 206 of the first beam 271 is directed to a first grating 111 ( FIG. 1 ) of the plurality of gratings 107.

[0065] The first beam 271 is reflected from a first one of the gratings 107. The reflected beam forms a second beam 272. The second beam 272 is in the second optical path 232.

[0066] The light source 204 creates 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 may be before or after the first beam splitter 211 on the first optical path 231. In one or more embodiments, the first beam 271 travels to the first beam splitter 211, where a portion of the first beam 271 becomes a third beam 273. The third beam is directed to the second detector 218 on the third optical path 233. In one or more embodiments, the second beam 272 travels to the first beam splitter 211, where a portion of the second beam 272 becomes a third beam 273. The third beam is directed to the second detector 218 on the third optical path 233.

[0067] In operation 405, the second beam 272 is passed through a second lens 222. The second lens 222 is disposed on the second optical path 232. The second lens 222 forms a second beam diameter 269 from the second beam. The second beam diameter 269 may be approximately equal to the first beam diameter 206.

[0068] In operation 407, the second beam 272 is passed through the first aperture 260. The first aperture 260 is located 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 as the second beam 272 reaches the second beam diameter 269 from 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 oblique aperture 263. The oblique aperture 263 is angled at an oblique angle 266 from the second beam 272.

[0069] In operation 409, second beam 272 is passed through third lens 223. Third lens 223 is on second optical path 232. Third lens 223 is provided on second optical path 232 after first aperture 260. Third lens 223 receives second beam 272 focused from first aperture 260 and collimates second beam 272.

[0070] In operation 411, a first image is formed from the second beam 272 by at least the 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 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.

[0071] 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. The information includes one or more of the grating pitch P, the grating orientation, the magnitude of the grating reflectivity, and the grating depth.

[0072] Benefits of the present disclosure include improved grating resolution. A first lens focuses light to a very small spot, allowing for localized grating analysis. Passing the focused light through a first aperture helps minimize noise caused by light reflected from other surfaces.

[0073] It is contemplated that one or more aspects disclosed herein may be combined. By way of example, one or more aspects, features, components, operations, and / or properties of optical arm 104, first lens 221, second lens 222, third lens 223, first aperture 260, angled aperture 263, first detector 208, second detector 218, and third detector 217 shown in Figures 2A-2D, detector arm 112, first lens 327, second lens 328, third lens 329, second aperture 360, and sensor 308 shown in Figure 3, and / or method 400 in Figure 4 may be combined. Furthermore, it is contemplated that one or more aspects disclosed herein may include some or all of the benefits described above.

[0074] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, the scope of which is defined by the following claims.

Claims

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

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

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

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

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

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

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

11. The system of claim 1 further comprising a third detector disposed at an angle from the second beam.

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

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

14. The system of claim 13 , wherein the first aperture is disposed at an oblique angle from the second beam.

15. The system of claim 14 , wherein the second aperture is disposed at the oblique angle from the second beam.

16. 14. The system of claim 13, further comprising a second lens, the second lens being 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 of claim 13 , wherein the substrate support is disposed between the optical arm and the detector arm.

18. rotating a substrate to position a plurality of gratings having an orientation angle perpendicular to a first light path directed toward a first zone of the substrate, the first zone having the plurality of gratings disposed therein; projecting a first beam into the first zone, 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 in 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 located on the second optical path, the first aperture receiving the second beam diameter of the second beam; passing the second beam through a third lens on the second optical path, the third lens being disposed after the first aperture; forming a first image from the second beam with a first detector; A method comprising:

19. 20. The method of claim 18, wherein the first beam diameter of the first lens is directed onto a hypotenuse of the first grating.

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

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