Apparatus and method for measuring optical reflectance

Abstract

The present disclosure relates to metrology measurement assemblies and related methods. In one or more embodiments, a laser arm assembly includes a laser arm. The laser arm includes a motor mount disposed between a laser end of the laser arm and a second end of the laser arm, the motor mount defining a rotation axis. The laser arm assembly also includes an optical unit connected to the laser end of the arm. The optical unit includes a light source directed toward the rotation axis. The laser arm assembly also includes a weight disposed at the second end of the arm and a motor connected to the motor mount of the arm. The motor includes a brake, a laser motor shaft coaxial with the rotation axis, and an encoder.

Description

[Technical Field]

[0001]

[0001] Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, embodiments described herein provide metrology methods and assemblies. [Background technology]

[0002]

[0002] Virtual reality is generally thought of as a computer-generated simulated environment in which a user has an apparent physical presence. Virtual reality experiences are generated in 3D and can be viewed on a head-mounted display (HMD) (e.g., glasses or other wearable display device with near-eye display panels as lenses for displaying a virtual reality environment that replaces the real environment).

[0003]

[0003] Augmented reality, however, provides an experience in which a user not only sees their surroundings through the display lenses of glasses or other HMD devices, but also sees images of virtual objects that are generated for display and appear as part of the environment. Augmented reality may include any type of input (e.g., audio input and haptic input), as well as virtual images, graphics, and video that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality presents many challenges and design constraints.

[0004] One such challenge is measuring optical devices to image quality standards. Metrology metrics of manufactured optical devices must be obtained to ensure image quality standards are met. However, existing measurement systems lack the desired field of view and suffer from inaccurate readings and noise. Therefore, what is needed in the art is a measurement assembly and method for using a measurement system with features that improve accuracy and reduce noise. Summary of the Invention

[0005]

[0005] The present disclosure relates to metrology measurement assemblies and related methods. In one or more embodiments, a laser arm assembly includes a laser arm. The laser arm includes a motor mount disposed between a laser end of the laser arm and a second end of the laser arm, the motor mount defining a rotation axis. The laser arm assembly also includes an optical unit connected to the laser end of the arm. The optical unit includes a light source directed toward the rotation axis. The laser arm assembly also includes a weight disposed at the second end of the arm and a motor connected to the motor mount of the arm. The motor includes a brake, a laser motor shaft coaxial with the rotation axis, and an encoder.

[0006] In one or more embodiments, the measurement assembly includes a laser arm assembly including a laser arm, a laser motor defining a rotation axis, and a first optical unit disposed at a laser end of the laser arm. The measurement assembly also includes a reflector arm assembly including a reflector arm, a reflector motor having a motor axis coaxial with the rotation axis of the laser arm, and a second optical unit disposed at the first end of the reflector arm. The measurement assembly also includes a stage assembly disposed between the laser arm assembly and the reflector arm assembly, the stage assembly including a pedestal defining a process plane and a translation mechanism configured to translate the stage assembly.

[0007] In one or more embodiments, the measurement assembly includes a laser arm assembly, a reflecting arm assembly, a stage assembly, a controller, and a non-transitory computer-readable medium. The laser arm assembly includes a laser arm having a laser end, a laser motor defining a rotation axis, and a first optical unit disposed at the laser end of the laser arm. The reflecting arm assembly includes a reflecting arm having a first end, a reflecting motor including a motor axis coaxial with the rotation axis of the laser arm assembly, and a second optical unit disposed at the first end of the reflecting arm. The stage assembly is disposed between the laser arm assembly and the reflecting arm assembly. The stage assembly includes a pedestal defining a process plane and a translation mechanism configured to enable the process plane to be coplanar with the rotation axis. The controller controls the measurement assembly. The non-transitory computer-readable medium has stored thereon instructions that, when executed by a processor, cause the process to perform a measurement method. The method includes moving the substrate to a first position, rotating a laser arm assembly to align a first optical unit approximately perpendicular to an orientation angle of a grating on the substrate, rotating a reflecting arm assembly to align a second optical unit approximately parallel to the orientation angle of the grating, and performing an optical measurement on the grating.

[0008]

[0008] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, which may also admit of other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1]

[0009] FIG. 1 is a schematic diagram of a measurement assembly according to an embodiment described herein. [Figure 2]

[0010] 1 is a perspective schematic diagram of a measurement assembly according to embodiments described herein. [Figure 3]

[0011] 3 is a schematic cross-sectional view of an arm assembly of the measurement assembly of FIG. 2 according to embodiments described herein. [Figure 4]

[0012] FIG. 1 is a perspective schematic view of a motor assembly according to embodiments described herein. [Figure 5]

[0013] FIG. 1 is a flow diagram of a method for optical device metrology according to embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0014] For ease of understanding, where possible, identical reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further description.

[0011]

[0015] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to optical devices for augmented reality, virtual reality, and mixed reality. More specifically, embodiments described herein provide metrology measurement assemblies and methods. Metrology measurement systems and methods are illustrated and described herein.

[0012]

[0016] The assembly enhances the accuracy of information obtained from the grating through the features of the measurement assembly described herein. The embodiments described herein enable precise localized measurements of individual structures, gratings, and optical devices on a surface. Measurements are achieved by incorporating independent arm assemblies, counterweights, and a reference base for the components and movement mechanisms. The measurement assembly also enables non-destructive testing. Localized measurements are also achieved in part by the configuration of the assembly, with emphasis placed on the stiffness of the arm assembly. For example, in one or more embodiments, the arms of the measurement assembly have approximately the same dimensions to ensure repeatability and measurement accuracy and have uniform deflections.

[0013]

[0017] 1 is a schematic diagram of a measurement assembly 100 according to an embodiment described herein. The measurement assembly 100 includes a laser arm assembly 101 and a reflector arm assembly 102.

[0014]

[0018] The laser arm assembly 101 includes a laser arm 105. The laser arm 105 is a rigid arm. In some embodiments, the laser arm 105 may be a metal arm. The laser arm assembly 101 includes a first optical unit 103, which is disposed at a laser end 105a of the laser arm 105. In one or more embodiments, the first optical unit 103 is a laser assembly including a light source, a lens, a detector, and an aperture. The first optical unit 103 is connected to the laser arm 105 such that it can be positioned to perform a measurement operation (e.g., a grating orientation measurement).

[0015]

[0019] The first optical unit 103 directs a first beam 131 to the region 121. The first beam 131 is directed at an angle of incidence 123. The angle of incidence 123 is the angle between a major surface of the optical device 109 and the first beam 131. In one or more embodiments, the first optical unit 103 is a Littrow unit for performing metrology measurements. In one or more embodiments, the first optical unit 103 is a Littrow unit. The Littrow unit is for performing metrology measurements. The first optical unit 103 may include a multi-axis position module connected to an aperture, a light source, and a sensor.

[0016]

[0020] Region 121 includes optical devices 109. Optical devices 109 include one or more gratings 111. Gratings 111 are formed by structures 113. Optical devices 109 include measurement points for measurement assembly 100 during measurement operations. The measurement points can be multiple points on each structure 113 for each grating 111 of each optical device 109. Optical devices 109 are positioned over substrate 107. Structures 113 provide pitch and grating orientation to gratings 111. During operation, a first beam 131 is projected by a light source in first optical unit 103. The first beam 131 is projected toward optical device 109. The first beam 131 is reflected from optical device 109. A second beam 132 is reflected toward first optical unit 103. A third beam 141 is reflected from optical device 109 toward a detector in second optical unit 104. For example, the first beam 131 impinges on the structure 113 of the optical device 109. The impingement of the structure 113 is repeated until the optical device 109 is imaged by the first optical unit 103 and the second optical unit 104.

[0017]

[0021] The reflecting arm assembly 102 includes a reflecting arm 106. The reflecting arm 106 is a rigid arm. In some embodiments, the reflecting arm 106 can be a metal arm. In some embodiments, the reflecting arm 106 is substantially identical to the laser arm 105. In one or more embodiments, the arms 105, 106 are made of the same metal and have the same dimensions. This similarity increases the reproducibility of measurements. Ensuring that the arms 105, 106 have similar mechanical properties also results in similar deflections. Therefore, problems due to mechanical errors can be uniformly explained without having to diagnose the error for each arm. The reflecting arm assembly 102 includes a second optical unit 104. The second optical unit 104 is disposed at a first end 106a of the reflecting arm 106.

[0018]

[0022] A portion of the first beam 131 is reflected towards the second optical unit 104. The portion of the first beam 131 reflected towards the second optical unit 104 is a third beam 141. The second optical unit 104 includes a detector for imaging the third beam 141. The third beam 141 travels towards the second optical unit 104 at a reflection angle 125. The reflection angle 125 is the angle between a major surface of the optical device 109 and the third beam 141. This is achieved by making the measurement point of the first optical unit 103 approximately the same as the measurement point of the second optical unit 104. The measurement spot is located within the region 121.

[0019]

[0023] The measurement assembly, according to some embodiments, may be disposed within an enclosure 150. The enclosure may include an atmospheric control unit 170. The atmospheric control unit 170 may control or monitor one or more of the gas composition within the enclosure 150, the temperature within the enclosure 150, and the moisture level within the enclosure 150. The enclosure 150 and the atmospheric control unit 170 improve the performance of the measurement assembly 100 by eliminating the possibility of contaminants affecting the measurement assembly during operation. The enclosure also enhances safety by preventing potentially harmful light from escaping.

[0020]

[0024] As shown, a controller 160 is in communication with the measurement assembly 100 and is used to control processes and methods (such as at least some of the steps of the methods described herein).

[0021]

[0025] The controller 160 is configured to receive data or input as sensor readings from multiple sensors. The sensors may include sensors in the first optical unit 103, sensors in the second optical unit 104, rotation sensors, encoders, and distance sensors of the measurement assembly 100. The controller 160 includes or is in communication with a system model of the measurement assembly 100. The controller 160 is further configured to store the readings and calculations. The readings and calculations include previous sensor readings, such as any previous sensor readings in the measurement assembly 100. The readings and calculations also include stored calculations after sensor readings have been measured by the controller 160 and run through the system model. As such, the controller 160 is configured not only to retrieve the saved readings and calculations, but also to save the readings and calculations for future use. By maintaining previous readings and calculations, the controller 160 can adjust the system model over time to reflect more accurate versions of the measurement assembly 100.

[0022]

[0026] The controller 160 can monitor and estimate the optimized parameters, adjust the angular position of the pedestal 203 (FIG. 2), adjust the orientation of the pedestal and / or the height of the pedestal 203, adjust the angular position of the laser arm assembly 101, and adjust the angular position of the reflector arm assembly 102.

[0023]

[0027] Controller 160 includes a central processing unit (CPU) 160a (e.g., processor), memory 160b containing instructions, and support circuits 160c for CPU 160a. Controller 160 controls various items directly or through other computers and / or controllers. In one or more embodiments, controller 160 is communicatively connected to a dedicated controller, and controller 160 functions as a central controller.

[0024]

[0028] The controller 160 is any form of general-purpose computer processor used in industrial environments to control various substrate processing chambers and equipment and their associated sub-processors. The memory 160b, or non-transitory computer-readable medium, is one or more of readily available memory such as random access memory (RAM), dynamic random access memory (DRAM), static RAM (SRAM), and synchronous dynamic RAM (SDRAM (e.g., DDR1, DDR2, DDR3, DDR3L, LPDDR3, DDR4, LPDDR4, etc.)), read-only memory (ROM), floppy disk, hard disk, flash drive, or any other form of digital storage (local or remote). The support circuits 160c of the controller 160 are connected to the CPU 160a to support the CPU 160a. The support circuits 160c include cache, power supplies, clock circuits, input / output circuits, and subsystems.

[0025]

[0029] The operational parameters (e.g., center-to-edge profile, angular position of pedestal 203, and height of pedestal 203) and operations are stored in memory 160b as software routines that are executed or invoked to transform controller 160 into an application-specific controller and control the operation of the various chambers / modules described herein. Controller 160 is configured to perform any of the operations described herein. The instructions stored on memory, when executed, cause one or more of the steps of a method associated with measurement assembly 100 (such as method 500 described below). Controller 160 and measurement assembly 100 are at least part of a measurement system that uses metrology.

[0026]

[0030] The various steps described herein (such as the steps of method 500) may be performed automatically using controller 160, or may be performed automatically or manually with certain steps performed by a user.

[0027]

[0031] In one or more embodiments, the controller 160 includes a mass storage device, an input control unit, and a display unit.

[0028]

[0032] The controller 160 is configured to control the sensor devices, rotational position, heating, and atmospheric conditions within the enclosure 150 by providing an output to the control of the atmospheric control unit 170 .

[0029]

[0033] The controller 160 is configured to adjust the output to the control based on the sensor readings, the system model, and the stored readings and calculations. The controller 160 includes embedded software and correction algorithms to calibrate the measurements.

[0030]

[0034] One or more machine learning and / or artificial intelligence algorithms may implement, adjust, and / or refine one or more of the algorithms, inputs, outputs, or variables described above. Additionally or alternatively, one or more machine learning and / or artificial intelligence algorithms may rank or prioritize certain aspects of adjustments to measurement assembly 100 and / or method 500 compared to other aspects of measurement assembly 100 and / or method 500. One or more machine learning and / or artificial intelligence algorithms may account for other changes in the measurement assembly, such as hardware replacement and / or degradation.

[0031]

[0035] In one or more embodiments, the one or more machine learning and / or artificial intelligence algorithms account for upstream or downstream changes that may occur in the measurement assembly due to variable changes in the measurement assembly 100 and / or method 500. For example, if variable "A" is adjusted to cause a change in process aspect "B," and such adjustment unintentionally causes a change in process aspect "C," the one or more machine learning and / or artificial intelligence algorithms may account for such change in aspect "C." In such embodiments, the one or more machine learning and / or artificial intelligence algorithms embody predictive aspects associated with implementing the measurement assembly 100 and / or method 500. The predictive aspects may be utilized to proactively mitigate unintended changes in the processing system.

[0032]

[0036] One or more machine learning and / or artificial intelligence algorithms can use, for example, regression models (such as linear regression models) or clustering techniques to estimate the optimized parameters. The algorithms can be unsupervised or supervised.

[0033]

[0037] In one or more embodiments, controller 160 performs one or more of the operations described herein automatically without the use of one or more machine learning or artificial intelligence algorithms.

[0034]

[0038] 2 is a perspective schematic diagram of a measurement assembly according to an embodiment 100 described herein. The measurement assembly 100 includes a stage assembly 201. The stage assembly 201 is disposed between the laser arm assembly 101 and the reflecting arm assembly 102. The stage assembly 201 includes a pedestal 203. The pedestal 203 defines a process plane P1. The substrate 107 is disposed on the pedestal 203. The pedestal 203 includes a node 250. The node 250 can be used to calibrate the laser arm assembly 101 and / or the reflecting arm assembly 102. In one or more embodiments, the process plane P1 of the pedestal can be positioned on the rotation axis A1. The pedestal 203 can be coplanar with the rotation axis A1, thereby improving the accuracy and precision of the measurement assembly 100. Measurement assembly 100 can use axis A1 to calibrate pedestal 203 to ensure that pedestal 203 is flat because axis A1 is parallel to base 207. Also, keeping the measurement point constant along axis A1 reduces potential errors due to deflections in the orientation of assemblies 101, 102 and pedestal 203.

[0035]

[0039] By mounting the stage assembly 201 between the laser arm assembly 101 and the reflector arm assembly 102, the rotation of each arm assembly 101, 102 can move independently of the other without risk of collision. Furthermore, the configuration in which the stage assembly 201 is located between the laser arm assembly 101 and the reflector arm assembly 102 allows for alignment between the assemblies 101 and 102, reducing the number of sources of variability.

[0036]

[0040] As shown, the laser arm assembly 101 includes a laser motor 219. The laser motor 219 is connected to the laser arm 105. The laser motor 219 includes a laser motor shaft. The shaft of the laser motor 219 is coaxial with the rotation axis A1. For example, the shaft of the laser motor 219 is approximately coaxial with the rotation axis A1 of the laser arm assembly 101.

[0037]

[0041] The laser arm assembly 101 also includes a weight 225 and a base mount 223. The weight 225 is located at the end of the laser arm 105 opposite the first optical unit 103. The laser arm 105 is located between the first optical unit 103 and the weight 225. The weight 225 is located away from the axis A1. The weight 225 is adjustable. The weight 225 has a mass of about 30 kilograms to about 90 kilograms. The mass of the weight 225 can have a ratio to the mass of the first optical unit 103. For example, the ratio of the mass of the weight 225 to the mass of the first optical unit 103 is about 1:2 to about 1:4 (e.g., about 1:3, where the mass of the weight 225 is about three times the mass of the first optical unit 103). In one or more embodiments, the first optical unit 103 is removable and modular.

[0038]

[0042] The laser arm 105 and first optical unit 103 are configured to be able to deflect by less than approximately 20 microns during operation. The laser arm can rotate at least 180 degrees. For example, the laser arm 105 can rotate ±80 degrees from a vertical position. In other words, the laser arm 105 can rotate ±80 degrees in the XZ plane from the positive Z direction about the rotation axis A1, resulting in a deflection of less than approximately 25 microns when the laser arm assembly 101 is rotated.

[0039]

[0043] As shown, the reflective arm assembly 102 includes a reflective motor 220. The reflective motor 220 is connected to the reflective arm 106. The reflective motor 220 has an axis aligned with the axis A1. In other words, the axis of the reflective motor 220 is coaxial with the axis of rotation A1. The axis of each motor 219, 220 is coaxial with the axis of rotation A1. In one or more embodiments, the motors 219, 220 are direct drive motors.

[0040]

[0044] The reflecting arm assembly 102 also includes a weight (not shown) and a base mount 222. The weight is located at the end of the reflecting arm 106 opposite the second optical unit 104. The reflecting arm 106 is located between the second optical unit 104 and the weight. The weight is located away from the axis A1. The weight is adjustable. The weight 225 has a mass of about 30 kilograms to about 90 kilograms. The mass of the weight can have a ratio to the mass of the second optical unit 104. For example, the ratio of the mass of the weight to the mass of the second optical unit 104 is about 1:2 to about 1:4 (e.g., about 1:3, where the mass of the weight is about three times the mass of the first optical unit 103). In one or more embodiments, taking into account variations in the components of the optical units 103 and 104, the weight of the laser arm assembly 101 is within about 15% of the weight of the reflecting arm assembly 102.

[0041]

[0045] In one or more embodiments, the weight 225 of the laser arm assembly 101 and the weight of the reflecting arm assembly 102 have approximately the same mass. In one or more embodiments, the weight 225 of the laser arm assembly 101 and the weight of the reflecting arm assembly 102 have different masses. The measurement assembly 100 includes a base 207. The weight 225 counterbalances the weights of the arm 105 and the first optical unit 103. This counterbalance reduces strain on the motor 219, thereby allowing for fine adjustment of the measurement assembly 100. The smaller the required force, the more precise the control of the movement. Although not shown, the reflecting arm assembly 102 also includes a weight on the opposite side of the second optical unit 104.

[0042]

[0046] In one or more embodiments, to account for variations in the weights of the optical units 103, 104, a first precision gear reducer is included in the laser arm assembly 101 and a second precision gear reducer is included in the reflector arm assembly 102 instead of the weight 225.

[0043]

[0047] The stage assembly 201 is disposed on a base 207. The base 207 is a single piece. For example, the base 207 is a single piece of granite. In another example, the base 207 is a single piece of metal with a machined surface. The base 207 forms a flat surface with a tolerance of approximately 0.1 microns and 2 microns, with a variation of less than 2 microns across the entire 400 x 400 millimeter surface of the base 207. The base 207 acts as a reference surface for calibrating the measurement assembly 100. A base mount 222 for the laser arm assembly 101 and a base mount 223 for the reflector arm assembly 102 are disposed on the base 207. The base mounts 222, 223 and the motors 219, 220 are similar to ensure that the axes of the motors 219, 220 are aligned with the central axis A1.

[0044]

[0048] The stage assembly 201 also includes a translation mechanism 205. The translation mechanism 205 is configured to translate the pedestal 203. The translation mechanism 205 is disposed between the pedestal 203 and a base 207.

[0045]

[0049] The movement mechanism 205 includes a carriage 209 and a rail 211. The carriage 209 is disposed between the rail 211 and the pedestal 203. The carriage 209 includes a bearing (not shown). The bearing of the carriage 209 is an air bearing disposed between the rail 211 and the carriage 209. The air bearing improves the measurement capability of the measurement assembly 100 by reducing the unsupported loads caused by typical ball bearings. In one or more embodiments, the carriage 209 and the pedestal 203 form an air-bearing stage assembly. The carriage 209 allows the pedestal to rotate about the X-, Y-, and Z-axes. The carriage 209 can also translate in the X-, Y-, and Z-directions. The carriage 209 can raise and lower the pedestal 203 along the Z-axis. The carriage 209 can translate the pedestal 203 in the X- and Y-directions along the rail 211 and guide 213. The pedestal 203 includes a chuck for holding the substrate 107. In one or more embodiments, the pedestal 203 includes a vacuum chuck. The pedestal 203 can translate at least ±300 millimeters along the X direction. For example, the pedestal can translate about 350 millimeters or more from the axis A1. The pedestal 203 can translate at least ±300 millimeters along the Y direction. For example, the pedestal 203 can translate about 320 millimeters or more from a center position on the axis A1. The pedestal 203 can translate at least ±2 millimeters along the Z direction. For example, the pedestal 203 can translate about 2.5 millimeters or more along the Z direction. The pedestal 203 can tilt along the XZ and YZ directions. For example, the pedestal 203 can tilt about 0.1° to about 2° along the XZ and YZ directions.

[0046]

[0050] The guides 213 are disposed on the base 207. The guides 213 are parallel to each other. The laser arm assembly 101 and the reflecting arm assembly 102 are disposed between the guides 213. The guides 213 are aligned parallel to the rotation axis A1. The rail 211 is disposed between the guides 213. The rail 211 is disposed perpendicular to the guides 213. The guides 213 move the rail 211 parallel to the Y-axis. Translation of the rail 211 translates the pedestal 203. The carriage 209 and the guide 213 comprise a device for moving the pedestal 203 in the X-direction parallel to the X-axis. By arranging the rail 211 perpendicular to the guides, the laser arm assembly 101 and the reflecting arm assembly 102 can be closer to the pedestal 203. This reduces the moment caused by the overhang of the optical units 103 and 104, improving the precision and accuracy of the measurement assembly 100. The rail 211 is elevated from the base 207 by the guide 213. This configuration allows the guide 213 to move the rail 211. The carriage 209 and the guide 213 are configured so that the pedestal 203 remains stationary when no power is applied to the pedestal 203, the carriage 209, and the guide 213.

[0047]

[0051] The movement mechanism 205, laser arm assembly 101, and reflecting arm assembly 102 are configured to position the substrate 107 in a position that allows the measurement assembly 100 to perform metrology operations with high precision relative to the optical device 109. The laser arm assembly 101 is similar in configuration to the reflecting arm assembly 102 in that at least one or more corresponding parts of each assembly 101, 102 are substantially identical. For example, the arms 105, 106, motors 219, 220, and base mounts 222, 223 are substantially the same in size, shape, and materials. In one or more embodiments, the parts of the reflecting arm assembly 102 and the laser arm assembly 101 are substantially identical, except for the first optical unit 103 and the second optical unit 104.

[0048]

[0052] The base, which provides a consistent reference surface for portions of the measurement assembly 100, allows for a high level of precision and accuracy. For example, the pedestal 203 may have a flatness and straightness accuracy of 30 micrometers or better. For example, the flatness and straightness of the pedestal 203 is accurate to 17 micrometers or better.

[0049]

[0053] FIG. 3 is a schematic diagram of the laser arm assembly 101 of the measurement assembly 100 of FIG. 2 according to embodiments described herein.

[0050]

[0054] The laser arm assembly 101 includes a mount assembly 400. The mount assembly 400 includes a motor mount 311, a motor frame 305, a brake 307, and a base mount 223.

[0051]

[0055] The motor mount 311 is connected to the laser arm 105. The motor mount 311 is also connected to the laser motor 219 of the laser arm assembly 101. The laser motor 219 is disposed on a motor frame 305. The motor frame 305 holds the laser motor 219 in place. The motor frame 305 is disposed on a base mount 223. The base mount 223 is disposed between the motor frame 305 and the base 207. The base mount 223 lifts the motor frame 305 and provides clearance for the laser arm assembly 101 to rotate and utilize the weight 225.

[0052]

[0056] The laser arm 105 includes a laser end 105a and a second end 105b. The second end 105b is disposed opposite the laser end 105a. The weight 225 is disposed proximate to the second end 105b. For example, the weight 225 is connected to the second end 105b of the laser arm 105.

[0053]

[0057] The first optical unit 103 is disposed at the laser end 105a of the laser arm 105. The first optical unit 103 may include a housing 301 and an analyzing unit 303. In one or more embodiments, the analyzing unit 303 is connected to the housing 301. In one or more embodiments, the analyzing unit 303 is disposed within the housing 301. The analyzing unit 303 projects the first beam 131 toward the optical device 109 and / or the substrate 107 ( FIG. 1 ). In one or more embodiments, the first beam 131 is projected toward the axis A1 so as to be perpendicular to the axis A1. In one or more embodiments, the first beam 131 originates from the housing 301 and passes through a lens to focus the first beam 131 so that the focal position is located on the structure 113, the grating 111, the optical device 109, the substrate 107, or other measurement surface. The first optical unit 103 also includes one or more sensors that receive the reflected light. For example, a sensor in the first optical unit 103 receives the second beam 132. The housing 301 of the first optical unit improves accuracy by providing a more rigid support for the components of the first optical unit 103.

[0054]

[0058] The motor mount 311 defines an axis of rotation. The motor mount 311 is disposed within the laser arm 105. The motor mount 311 is disposed between the laser end 105a and the second end 105b. The motor mount is disposed closer to the second end 105b than to the laser end 105a. For example, the motor mount 311 is disposed close to and / or adjacent to the second end 105b.

[0055]

[0059] The motor mount 311 is aligned with axis A1. The configuration described above is configured so that axis A1 is parallel to base 207. The relationship between axis A1 and the base enhances accuracy by providing a consistent geometry to reference during the calibration and measurement processes.

[0056]

[0060] The laser arm 105 also includes one or more alignment features 315. In one or more embodiments, the alignment features 315 are one or more lasers that align the arms 105, 106. In one or more embodiments, the alignment features 315 are one or more alignment pins located on one or more sides of the laser arm 105. In one or more embodiments, the alignment features 315 are one or more apertures located on one or more sides of the laser arm 105. One or more alignment features 315 are also present on the reflector arm 106 of the reflector arm assembly 102 (FIG. 2). The alignment features 315 allow for calibration of both the reflector arm assembly 102 and the laser arm assembly 101.

[0057]

[0061] The brake 307 is connected to the laser motor 219 and the motor frame 305. In one or more embodiments, the brake 307 is located on the motor frame 305 opposite the laser arm 105. In other words, the laser motor 219 is located between the laser arm 105 and the brake 307.

[0058]

[0062] FIG. 4 is a schematic cross-sectional view of a mount assembly 400 according to embodiments described herein.

[0059]

[0063] Although described above in the context of the laser arm assembly 101, one or more of the described embodiments may also be applied to the reflector arm assembly 102 (FIGS. 1 and 2). In one or more embodiments, the motor mount 311 is connected to the shaft 403. The motor mount 311 is connected to the shaft 403 by one or more pieces of hardware 407. The hardware 407 may be, but is not limited to, a bolt, a screw, a pin, or any other hardware meant to affix two or more bodies together. The shaft 403 is aligned with axis A1. The shaft 403 extends through the laser motor 219 along axis A1. The laser motor 219 is configured to rotate the shaft 403 and rotate the motor mount 311.

[0060]

[0064] In one or more embodiments, the laser motor 219 is connected to the motor frame 305. The laser motor 219 is connected to the motor frame 305 by one or more pieces of hardware 407. The laser motor 219 is configured to rotate the shaft 403, which in turn rotates the motor mount 311 such that the motor mount 311 receives rotation from the shaft 403.

[0061]

[0065] Mount assembly 400 includes brake 307 and brake plate 401. Motor frame 305 is disposed between brake 307 and brake plate 401. Brake 307 is connected to shaft 403. In one or more embodiments, brake 307 includes spring 409. Brake 307 and brake plate 401 are connected by spring 409. In one or more embodiments, brake 307 includes actuator 405. In one or more embodiments, brake 307 is a spring brake and actuator 405 is a normally closed solenoid. For example, the brake is a spring brake connected to a normally closed solenoid. Brake plate 401 is disposed on outer surface 305a of motor frame 305. For example, inner surface 401a of brake plate 401 is connected to outer surface 305a of motor frame 305 by hardware 407.

[0062]

[0066] In one or more embodiments, the actuator 405 is a solenoid that releases tension on the spring 409 upon receiving an electromagnetic signal. For example, when there is no signal to the actuator 405, the spring 409 biases the inner surface 307a into contact with the outer surface 401b of the brake plate 401, preventing movement of the brake 307 and shaft 403. When the actuator 405 receives a signal, the shaft 403 can rotate. The controller 160 (FIG. 1) communicates with the actuator 405 to control when the brake 307 is engaged. The controller 160 controls the laser arm assembly 101 through closed-loop control, and the brake 307 acts as a safety mechanism that locks the laser motor 219 in place if the controller 160 loses power and / or receives an error warning. In one or more embodiments, the laser motor 219 instead controls the actuator 405. In one or more embodiments, the brake 307 and actuator 405 form a spring brake connected to a normally closed solenoid.

[0063]

[0067] The motors 220, 219 include one or more encoders 411. The encoder 411 of each motor is configured to measure the rotation of the laser arm assembly 101 and / or the reflector arm assembly 102. The encoders 411 provide the angular position of the laser arm assembly 101. The encoders 411 enable the measured motion of the laser arm and reflector arm to have an angular accuracy and / or repeatability of approximately 30 microradians or less. For example, the accuracy of the encoder 411 is 17 microradians. This improves the accuracy of the measurement assembly 100. In one or more embodiments, the encoder 411 is an optical encoder that directly reads the angular position of the arm itself. The use of an optical encoder improves accuracy because positioning does not affect the arm position.

[0064]

[0068] 5 is a flow diagram of a method for optical device metrology according to an embodiment described herein. The CPU 160a of the controller 160 is configured to execute the method 500. The method 500 is a measurement process stored in the memory 160b of the controller 160.

[0065]

[0069] In step 501, the substrate 107 ( FIG. 1 ) is moved to a first position, where the pedestal 203 ( FIG. 2 ) is positioned and the structure 113 or grating 111 of the optical device 109 is ready for metrology operations. The pedestal 203 can rotate about the X-axis, Y-axis, and / or Z-axis to orient the substrate 107 so that the grating 111 of the optical device 109 can be positioned in the path of the first beam 131. The pedestal 203 can translate the substrate parallel to the X-axis, Y-axis, and / or Z-axis to orient the substrate 107 so that the grating 111 of the optical device 109 can be positioned in the path of the first beam 131.

[0066]

[0070] In step 503, the laser arm assembly 101 is rotated to align the first optical unit 103 approximately perpendicular to the orientation angle of the grating 111 on the substrate, and the reflecting arm assembly 102 is rotated to align the second optical unit 104 approximately parallel to the orientation angle of the first optical device.

[0067]

[0071] In step 505, the measurement assembly performs an optical measurement on the first optical device. The optical measurement includes projecting a first beam 131 from the first optical unit 103 toward a grating 111 of the substrate 107 and / or optical device 109. A second beam 132 is reflected from the grating 111 back to the first optical unit 103. A third beam 141 is reflected from the grating 111 toward the second optical unit 104.

[0068]

[0072] In step 507, sensors in first optical unit 103 and second optical unit 104 image the first optical device. Steps 501, 503, and 505 are repeated until optical device 109 has been imaged and one or more of the pitch, orientation, duty cycle, and reflectivity of grating 111 have been determined.

[0069]

[0073] Advantages of the present disclosure include the ability of the brake 307 to hold the laser arm assembly 101 and the reflector arm assembly 102 in place in the event of a power failure or unsafe condition. For example, if the housing 150 (FIG. 1) is opened during operation. Another advantage is that the base 207 and axis A1 can be used as a reference for calibrating the pedestal 203. This improves accuracy by referencing all components from a single plane. Another advantage is that the configuration of the guides 213 and rails 211 allows the pedestal 203 to move along and around the X-, Y-, and Z-axes. The similarity of the assemblies 101 and 102 ensures consistency and repeatability of movement. Specifically, when the assemblies 101 and 102 are positioned closer to a horizontal position, the assemblies 101 and 102 exhibit approximately uniform deflection characteristics. Therefore, the assemblies 101 and 102 will have a uniform tolerance rather than a tolerance specific to each specific assembly 101 and 102. Uniform deflection results in uniform error, which allows for quick root cause analysis to find the source of the error and subsequent correction.

[0070]

[0074] 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 measurement assembly 100, laser arm assembly 101, reflecting arm assembly 102, pedestal 203, rail 211, guide 213, weight 225, base 207 shown in FIG. 2, brake 307, first optical unit 103 shown in FIG. 3, actuator 405, encoder 411, spring 409 shown in FIG. 4, and method 500 may be combined. Furthermore, it is contemplated that one or more aspects disclosed herein may include some or all of the advantages described above.

[0071]

[0075] While the foregoing is directed to embodiments of the present disclosure, other and additional embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A laser arm assembly comprising: A laser arm, a motor mount disposed between a laser end of the laser arm and a second end of the laser arm, the motor mount defining an axis of rotation; a laser arm including: an optical unit connected to the laser end of the arm, the optical unit including a light source directed towards the axis of rotation; a weight disposed at the second end of the arm; a motor connected to the motor mount of the arm, brake, a laser motor shaft coaxial with the rotation shaft; and Encoder a motor; 1. A laser arm assembly comprising:

2. The laser arm assembly of claim 1 , further comprising an alignment pin disposed on a side of the laser arm.

3. 10. The laser arm assembly of claim 1, wherein the motor is a direct drive motor connected to the encoder, the encoder configured to measure rotation of the laser arm assembly.

4. The optical unit further comprises: a multi-axis position module connected to the aperture; and Sensor 10. The laser arm assembly of claim 1, comprising:

5. 10. The laser arm assembly of claim 1, wherein said brake is a spring brake connected to a normally closed solenoid.

6. 1. A measurement assembly comprising:

1. A laser arm assembly comprising: Laser arm, a laser motor defining an axis of rotation; and a first optical unit disposed at the laser end of the laser arm; a laser arm assembly including: A reflector arm assembly comprising: Reflex arm, a reflective motor including a motor shaft coaxial with the rotational axis of the laser arm; and a second optical unit disposed at the first end of the reflecting arm; a reflector arm assembly including: a stage assembly disposed between the laser arm assembly and the reflector arm assembly, a pedestal defining a process surface; and a translation mechanism configured to translate the stage assembly; a stage assembly including: A measurement assembly comprising:

7. The measurement assembly of claim 6 , further comprising a base, the laser arm assembly, the reflecting arm assembly, and the stage assembly being disposed on the base.

8. The measurement assembly of claim 6 , wherein the measurement point of the first optical unit is the same as the measurement point of the second optical unit.

9. The measurement assembly of claim 6 , further comprising a base with a rail, said rail disposed substantially perpendicular to said axis of rotation.

10. The measurement assembly of claim 9 , wherein the stage assembly is an air bearing stage assembly.

11. The measurement assembly of claim 6 , further comprising a housing disposed around the measurement assembly, the housing including an atmospheric control unit.

12. 7. The measurement assembly of claim 6, wherein the movement mechanism is configured such that the stage assembly can move the pedestal parallel to an X-axis, a Y-axis, and a Z-axis, and rotate the pedestal about the X-axis, the Y-axis, and the Z-axis.

13. 7. The measurement assembly of claim 6, wherein movement of the laser arm, the reflecting arm, and the stage assembly is repeatable to an angular accuracy of 30 microradians or better, and the pedestal has a flatness of 20 micrometers or better.

14. The measurement assembly of claim 6 , wherein the laser arm and the reflective arm are substantially identical.

15. The measurement assembly of claim 6 , wherein the pedestal further comprises a vacuum chuck.

16. The measurement assembly of claim 6 , wherein the first optical unit is removable.

17. 1. A measurement assembly comprising:

1. A laser arm assembly comprising: a laser arm having a laser end; a laser motor defining an axis of rotation; and a first optical unit disposed at the laser end of the laser arm; a laser arm assembly including: A reflector arm assembly comprising: a reflective arm having a first end; a reflective motor including a motor shaft, the motor shaft being coaxial with the rotational axis of the laser arm assembly; and a second optical unit disposed at the first end of the reflecting arm; a reflector arm assembly including: a stage assembly disposed between the laser arm assembly and the reflector arm assembly, a pedestal defining a process surface; and a movement mechanism configured to allow the process surface to be coplanar with the rotation axis; a stage assembly including: a controller for controlling the measurement assembly; 1. A non-transitory computer-readable medium having stored thereon instructions that, when executed by a processor, cause the processor to perform a measurement method, the method comprising: moving the substrate to a first position; rotating the laser arm assembly to align the first optical unit approximately perpendicular to an orientation angle of a grating on the substrate; rotating the reflecting arm assembly to align the second optical unit substantially parallel to the orientation angle of the grating; and performing optical measurements on said grating; a non-transitory computer-readable medium, A measurement assembly comprising:

18. The method further comprises: moving the pedestal to a second position; rotating the laser arm assembly to align the first optical unit approximately perpendicular to a second orientation angle of a second optical device on the substrate; rotating the reflecting arm assembly to align the second optical unit substantially parallel to the second orientation angle of the second optical device; and performing a measurement of the second optical device; 20. The measurement assembly of claim 17, comprising:

19. 18. The measurement assembly of claim 17, wherein moving the pedestal comprises at least one of rotating the pedestal about an X-axis, a Y-axis, or a Z-axis, and translating the pedestal along the X-axis, the Y-axis, or the Z-axis.

20. The method further comprises: calibrating the measurement assembly by aligning the first optical unit with a node disposed on the pedestal; 20. The measurement assembly of claim 17, comprising:

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