Apparatus and method for optical reflectance measurement

Abstract

The present disclosure relates to metrology measurement assemblies and related methods. In one or more embodiments, the 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 an axis of rotation. The laser arm assembly also includes an optical unit coupled 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 counterweight disposed on the second end of the arm, and a motor coupled to the motor mount of the arm. The motor includes a brake, a laser motor shaft coaxial with the rotating shaft, and an encoder.

Description

Technical Field

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

[0002] Virtual reality is generally considered a computer-generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed using a head-mounted display (HMD), such as glasses or other wearable display devices having a near-eye display panel as a lens to display a virtual reality environment that replaces the actual environment.

[0003] However, augmented reality enables the following experience, where a user can still view the surrounding environment through the display lens of glasses or other HMD devices and can also see an image of a virtual object that is generated for display and appears as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and videos of the environment that enhance or augment the user experience. As an emerging technology, augmented reality faces many challenges and design limitations.

[0004] One such challenge is measuring the image quality standards of optical devices. To ensure that the image quality standards are met, metrology metrics of the manufactured optical devices must be obtained. However, existing measurement systems lack the desired field of view and suffer from inaccurate readings and noise. Therefore, there is a need in the art for measurement components and methods of using measurement systems with improved accuracy and features to reduce noise. Summary of the Invention

[0005] The present disclosure relates to metrology measurement components 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 further includes an optical unit coupled to the laser end of the arm. The optical unit includes a light source that points to the rotation axis. The laser arm assembly further includes a counterweight disposed on the second end of the arm, and a motor coupled 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, a measurement assembly includes a laser arm assembly. The laser arm assembly includes 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 further includes a reflective arm assembly including a reflective arm, a reflective motor having a motor axis coaxial with the rotation axis of the laser arm, and a second optical unit disposed at a first end of the reflective arm. The measurement assembly further includes a platform assembly disposed between the laser arm assembly and the reflective arm assembly. The platform assembly includes: a base defining a process plane; and a movement mechanism configured to translate the platform assembly.

[0007] In one or more embodiments, a measurement assembly includes a laser arm assembly, a reflective arm assembly, a platform 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 that defines a rotation axis; and a first optical unit disposed at the laser end of the laser arm. The reflective arm assembly includes: a reflective arm having a first end; a reflective motor including a motor axis that is coaxial with the rotation axis of the laser arm assembly; and a second optical unit disposed at the first end of the reflective arm. The platform assembly is disposed between the laser arm assembly and the reflective arm assembly. The platform assembly includes a base defining a process plane and a movement mechanism configured to bring the process plane coplanar with the rotation axis. The controller controls the measurement assembly. The non-transitory computer-readable medium includes instructions stored thereon that, when executed by a processor, cause the process to perform a measurement method. The method includes moving a substrate to a first position, rotating the laser arm assembly to align the first optical unit at an orientation angle substantially perpendicular to a grating on the substrate, rotating the reflective arm assembly to align the second optical unit at an orientation angle substantially parallel to the grating, and performing an optical measurement of the grating. Brief Description of the Drawings

[0009] For a more particular understanding of the features described above of the present disclosure, a more specific description of the present disclosure briefly summarized above may be obtained by reference to the embodiments, some of which are illustrated in the drawings. It should be noted, however, that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and other equally effective embodiments are contemplated.

[0010] Figure 1 is a schematic diagram of a measurement assembly according to an embodiment described herein.

[0011] Figure 2 is a perspective schematic diagram of a measurement assembly according to an embodiment described herein.

[0012] Figure 3 is according to an embodiment described herein Figure 2 of the arm assembly of the measurement assembly in

[0013] Figure 4 is a perspective schematic view of a motor assembly according to an embodiment described herein.

[0014] Figure 5 is a flowchart of a method for optical device metrology according to an embodiment described herein.

[0015] For ease of understanding, the same element symbols are used as much as possible to label the same elements common to the various figures. Elements and features of one embodiment may be advantageously incorporated into other embodiments without further recitation. Detailed Description

[0016] Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, the embodiments described herein provide metrology measurement components and methods. Metrology measurement systems and methods are shown and described herein.

[0017] The components enhance the accuracy of information derived from gratings through the features of the measurement components described herein. The embodiments described herein allow for accurate local measurements of individual structures, gratings, and optical devices on a surface. The measurements are accomplished by integrating individual arm assemblies, balance weights, and a substrate that serves as a reference for the components and movement mechanisms. The measurement components further enable non-destructive testing. The local measurements are also accomplished in part through the configuration of the components and focus on the rigidity of the arm assemblies. For example, in one or more embodiments, the arms of the measurement components have substantially the same dimensions to ensure repeatability, accuracy, and uniform deflection of the measurements.

[0018] Figure 1 is a schematic view of a measurement component 100 according to an embodiment described herein. The measurement component 100 includes a laser arm assembly 101 and a reflective arm assembly 102.

[0019] 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, and the first optical unit 103 is disposed on the laser end 105a of the laser arm 105. In one or more embodiments, the first optical unit 103 is a laser component that includes a light source, a lens, a detector, and an aperture. The first optical unit 103 is disposed and coupled to the laser arm 105 such that the first optical unit 103 can be positioned to perform measurement operations, such as grating orientation measurements.

[0020] The first optical unit 103 guides the first light beam 131 to the area 121. The first light beam 131 is guided at an incident angle 123. The incident angle 123 is the angle between the principal plane of the optical device 109 and the first light 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 used to perform metrology measurements. The first optical unit 103 may include a multi-axis positioning module coupled to the aperture, a light source, and a sensor.

[0021] The area 121 includes the optical device 109. The optical device 109 includes one or more gratings 111. The gratings 111 are formed by the structures 113. The optical device 109 includes the measurement points of the measurement assembly 100 during the measurement operation. The measurement points may be multiple points on each structure 113 of each grating 111 in each optical device 109. The optical device 109 is disposed above the substrate 107. The structure 113 gives the grating 111 pitch and the orientation of the grating. In operation, the first light beam 131 is projected by the light source of the first optical unit 103. The first light beam 131 is projected towards the optical device 109. The first light beam 131 is reflected from the optical device 109. The second light beam 132 is reflected back towards the first optical unit 103. The third light beam 141 is reflected from the optical device 109 and towards the detector of the second optical unit 104. For example, the first light beam 131 impinges on the structure 113 of the optical device 109. The impinging on the structure 113 is repeated until the optical device 109 is imaged by the first optical unit 103 and the second optical unit 104.

[0022] The reflection arm assembly 102 includes a reflection arm 106. The reflection arm 106 is a rigid arm. In some embodiments, the reflection arm 106 may be a metal arm. In some embodiments, the reflection arm 106 is substantially the same as 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 enhances the repeatability of the measurement. By making the arms 105, 106 have similar mechanical qualities, their respective deflections will also be similar. Therefore, the problems caused by mechanical errors can be considered in a unified manner without having to diagnose the errors on a per-arm basis. The reflection arm assembly 102 includes a second optical unit 104. The second optical unit 104 is disposed on the first end 106a of the reflection arm 106.

[0023] A portion of the first light beam 131 is reflected towards the second optical unit 104. The portion of the first light beam 131 reflected towards the second optical unit 104 is the third light beam 141. The second optical unit 104 includes a detector to image the third light beam 141. The third light beam 141 travels towards the second optical unit 104 at a reflection angle 125. The reflection angle 125 is the angle between the principal plane of the optical device 109 and the third light beam 141. This is accomplished by making the measurement points of the first optical unit 103 substantially the same as the measurement points of the second optical unit 104. The measurement points are set within the region 121.

[0024] According to some embodiments, the measurement assembly may be disposed within the housing 150. The housing may include an atmosphere control unit 170. The atmosphere control unit 170 may control or monitor one or more of the gas composition within the housing 150, the temperature within the housing 150, and the humidity level within the housing 150. The housing 150 and the atmosphere control unit 170 enhance the capabilities of the measurement assembly 100 by eliminating the possibility of contaminants affecting the measurement assembly during operation. The housing also enhances safety by preventing the escape of potentially harmful light.

[0025] As shown, the controller 160 communicates with the measurement assembly 100 and is used to control processes and methods, such as at least some operations of the methods described herein.

[0026] The controller 160 is configured to receive data or inputs as sensor readings from a plurality of sensors. The sensors may include sensors in the first optical unit 103, sensors in the second optical unit 104, rotational sensors, encoders, and distance sensors of the measurement assembly 100. The controller 160 is equipped with or communicates with a system model of the measurement assembly 100. The controller 160 is further configured to store readings and calculations. The readings and calculations include previous sensor readings, such as any previous sensor readings within the measurement assembly 100. The readings and calculations further include calculated values stored after the sensor readings are measured by the controller 160 and run through the system model. Thus, the controller 160 is configured to retrieve the stored readings and calculations and save the readings and calculations for future use. Maintaining previous readings and calculations enables the controller 160 to adjust the system model over time to reflect a more accurate version of the measurement assembly 100.

[0027] The controller 160 may monitor, estimate optimization parameters, adjust the angular position of the base 203 ( Figure 2 ), adjust the orientation and / or the height of the base, adjust the angular position of the laser arm assembly 101, and adjust the angular position of the reflecting arm assembly 102.

[0028] The controller 160 includes a central processing unit (CPU) 160a (e.g., a processor), a memory 160b containing instructions, and support circuitry 160c for the CPU 160a. The controller 160 directly controls various items, or controls via other computers and / or controllers. In one or more embodiments, the controller 160 is communicatively coupled to a dedicated controller, and the controller 160 serves as a central controller.

[0029] The controller 160 is any form of general-purpose computer processor used in an industrial environment to control various substrate processing chambers and equipment, as well as sub-processors thereon or therein. The memory 160b or non-transitory computer-readable medium is one or more randomly accessible memories, 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 disks, hard disks, flash drives, or any other form of digital memory, local or remote. The support circuitry 160c of the controller 160 is coupled to the CPU 160a to support the CPU 160a. The support circuitry 160c includes a cache, power supply, clock circuit, input / output circuit, and subsystems, etc.

[0030] Operating parameters (e.g., center-to-edge profile, angular position of the pedestal 203, and height of the pedestal 203) and operations are stored in the memory 160b as software routines that are executed or called to turn the controller 160 into a dedicated controller to control the operations of the various chambers / modules described herein. The controller 160 is configured to perform any of the operations described herein. The instructions stored in the memory, when executed, cause one or more operations of a method (such as method 500 described below) to be performed on the measurement component 100. The controller 160 and the measurement component 100 are at least part of a system for making measurements using metrology.

[0031] The various operations described herein (such as the operations of method 500) can be automatically performed using the controller 160, or can be performed automatically or manually with certain operations performed by a user.

[0032] In one or more embodiments, the controller 160 includes a mass storage device, an input control unit, and a display unit.

[0033] The controller 160 is configured to control the sensor device, rotational position, heating, and atmospheric conditions in the housing 150 by providing an output to the control of the atmosphere control unit 170.

[0034] The controller 160 is configured to adjust the output of the control based on sensor readings, system models, and stored readings and calculations. The controller 160 includes embedded software and compensation algorithms for correcting measurements.

[0035] One or more machine learning algorithms 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 algorithms and / or artificial intelligence algorithms may rank or prioritize certain aspects of the adjustments of the measurement component 100 and / or method 500 relative to other aspects of the measurement component 100 and / or method 500. One or more machine learning algorithms and / or artificial intelligence algorithms may consider other changes within the measurement component, such as hardware replacement and / or degradation.

[0036] In one or more embodiments, one or more machine learning algorithms and / or artificial intelligence algorithms take into account upstream or downstream changes that may occur in the measurement component due to changes in the variables of the measurement component 100 and / or method 500. For example, if variable "A" is adjusted to cause a change in aspect "B" of the process, and this adjustment inadvertently causes a change in aspect "C" of the process, then one or more machine learning algorithms and / or artificial intelligence algorithms may take this change in aspect "C" into account. In such an embodiment, one or more machine learning algorithms and / or artificial intelligence algorithms embody the predictive aspect related to implementing the measurement component 100 and / or method 500. The predictive aspect can be used to prophylactically reduce unexpected changes within the processing system.

[0037] One or more machine learning algorithms and / or artificial intelligence algorithms may use, for example, regression models (such as linear regression models) or clustering techniques to estimate optimization parameters. The algorithms may be unsupervised or supervised.

[0038] In one or more embodiments, the controller 160 automatically performs one or more of the operations described herein without using one or more machine learning algorithms or artificial intelligence algorithms.

[0039] Figure 2is a perspective view of the measurement assembly 100 according to an embodiment described herein. The measurement assembly 100 includes a platform assembly 201. The platform assembly 201 is disposed between a laser arm assembly 101 and a reflection arm assembly 102. The platform assembly 201 includes a base 203. The base 203 defines a process plane P1. A substrate 107 is disposed on the base 203. The base 203 includes nodes 250. The nodes 250 can be used to calibrate the laser arm assembly 101 and / or the reflection arm assembly 102. In one or more embodiments, the process plane P1 of the base can be disposed on a rotation axis A1. The ability to coplane the base 203 with the rotation axis A1 enhances the accuracy and precision of the measurement assembly 100. The measurement assembly 100 can use the rotation axis A1 to calibrate the base 203 and ensure that the base 203 is flat because the axis A1 is parallel to the base 207. Additionally, by making the measurement points along the axis A1 consistent, the potential error of the deflection of the orientation of the components 101, 102, and the base 203 can be reduced.

[0040] By placing the platform assembly 201 between the laser arm assembly 101 and the reflection arm assembly 102, the rotation of each arm assembly 101, 102 can move independently of the other arm assemblies without worrying about collisions. Additionally, the configuration of the platform assembly 201 between the laser arm assembly 101 and the reflection arm assembly 102 achieves consistency between the components 101, 102, thereby reducing the number of factors that will cause variations.

[0041] As shown, the laser arm assembly 101 includes a laser motor 219. The laser motor 219 is coupled 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 generally coaxial with the rotation axis A1 of the laser arm assembly 101.

[0042] The laser arm assembly 101 further includes a counterweight 225 and a base mount 223. The counterweight 225 is disposed at an end of the laser arm 105 opposite to the first optical unit 103. The laser arm 105 is disposed between the first optical unit 103 and the counterweight 225. The counterweight 225 is disposed at a certain distance from the axis A1. The counterweight 225 is an adjustable counterweight. The mass of the counterweight 225 is about 30 kg to about 90 kg. There may be a certain ratio between the mass of the counterweight 225 and the mass of the first optical unit 103. For example, the ratio of the mass of the counterweight 225 to the mass of the first optical unit 103 is about 1:2 to about 1:4, such as about 1:3, such that the mass of the counterweight 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.

[0043] The laser arm 105 and the first optical unit 103 are configured to be deflectable by less than about 20 microns during operation. The laser arm can rotate at least 180°. For example, the laser arm 105 can rotate ±80° from the vertical position. In other words, the laser arm 105 can rotate ±80° about the axis of rotation A1 in the XZ plane from the positive Z direction, such that the laser arm assembly 101 will deflect less than about 25 microns when rotated.

[0044] As shown, the reflecting arm assembly 102 includes a reflecting motor 220. The reflecting motor 220 is coupled to the reflecting arm 106. The axis of the reflecting motor 220 is aligned with the axis A1. In other words, the axis of the reflecting motor 220 is coaxial with the axis of rotation A1. The axes of each of the motors 219, 220 are coaxial with the axis of rotation A1. In one or more embodiments, the motors 219, 220 are direct drive motors.

[0045] The reflecting arm assembly 102 further includes a counterweight (not shown) and a base mount 222. The counterweight is disposed at an end of the reflecting arm 106 opposite to the second optical unit 104. The reflecting arm 106 is disposed between the second optical unit 104 and the counterweight. The counterweight is disposed at a distance from the axis A1. The counterweight is an adjustable counterweight. The counterweight 225 has a mass of about 30 kg to about 90 kg. The mass of the counterweight may have a certain ratio to the mass of the second optical unit 104. For example, the ratio of the mass of the counterweight to the mass of the second optical unit 104 is about 1:2 to about 1:4, for example, about 1:3, such that the mass of the counterweight is about three times the mass of the first optical unit 103. In one or more embodiments, the counterweight of the laser arm assembly 101 is within about 15% of the counterweight of the reflecting arm assembly 102 to account for variations in the components in the optical units 103, 104.

[0046] In one or more embodiments, the counterweight 225 of the laser arm assembly 101 and the counterweight of the reflecting arm assembly 102 have substantially the same mass. In one or more embodiments, the counterweight 225 of the laser arm assembly 101 and the counterweight of the reflecting arm assembly 102 have different masses. The measuring assembly 100 includes a base 207. The counterweight 225 balances the counterweight of the arm 105 and the first optical unit 103. This balance imposes less strain on the motor 219, and thus more precise adjustability of the measuring assembly 100 can be achieved. The smaller the force required, the more precise the movement control. Although not shown, the reflecting arm assembly 102 also includes a counterweight opposite to the second optical unit 104.

[0047] In one or more embodiments, a first precision gear reducer is included in the laser arm assembly 101, and a second precision gear reducer is included in the reflecting arm assembly 102 to replace the counterweight 225 to account for variations in the counterweights in the optical units 103, 104.

[0048] The platform component 201 is disposed on a base 207. The base 207 is a single body. For example, the base 207 is a single granite body. In another example, the base 207 is a single metal body with a machined surface. The base 207 forms a flat surface with a tolerance between about 0.1 micrometer and 2 micrometers such that the base varies by less than 2 micrometers over a 400 x 400 millimeter surface of the base 207. The base 207 operates as a reference plane for calibrating the measurement assembly 100. The base mounts 222, 223 of the laser arm assembly 101 and the reflection arm assembly 102 are disposed on the base 207. The base mounts 222, 223 and the motors 219, 220 are similar to ensure alignment of the axes of the motors 219, 220 with the central axis A1.

[0049] The platform component 201 further includes a moving mechanism 205. The moving mechanism 205 is configured to translate the base 203. The moving mechanism 205 is disposed between the base 203 and the base 207.

[0050] The moving mechanism 205 includes a carriage 209 and a track 211. The carriage 209 is disposed between the track 211 and the base 203. The carriage 209 includes bearings (not shown). The bearings of the carriage 209 are air bearings disposed between the track 211 and the carriage 209. The air bearings enhance the measurement capabilities of the measurement assembly 100 by reducing any unsupported loads generated by conventional ball bearings. In one or more embodiments, the carriage 209 and the base 203 form an air bearing platform assembly. The carriage 209 rotates the base 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 base 203 along the Z axis. The carriage 209 can translate the base 203 along the track 211 and the guide 213 in the X and Y directions. The base 203 includes a fixture for securing the substrate 107. In one or more embodiments, the base 203 includes a vacuum fixture. The base 203 is capable of translating along the X direction by + / - at least 300 millimeters. For example, the base can translate about 350 millimeters or more from the axis A1. The base 203 is capable of translating along the Y direction by + / - at least 300 millimeters. For example, the base 203 can translate about 320 millimeters or more from the central position on the axis A1. The base 203 is capable of translating along the Z direction by + / - at least 2 millimeters. For example, the base 203 can translate about 2.5 millimeters or more along the Z direction. The base 203 is capable of tilting along the XZ and YZ directions. For example, the base 203 can tilt about 0.1° to about 2° along the XZ and YZ directions.

[0051] The guide members 213 are disposed on the base 207. The guide members 213 are parallel to each other. The laser arm assembly 101 and the reflection arm assembly 102 are disposed between the guide members 213. The guide members 213 are aligned parallel to the rotation axis A1. The rails 211 are disposed between the guide members 213. The rails 211 are disposed perpendicular to the guide members 213. The guide members 213 translate the rails 211 parallel to the Y-axis. Translating the rails 211 then translates the base 203. The carriage 209 and the guide members 213 include means for translating the base 203 parallel to the X-axis in the X-direction. By making the rails 211 perpendicular to the guide members, the laser arm assembly 101 and the reflection arm assembly 102 can be brought closer to the base 203. This enhances the accuracy and precision of the measurement assembly 100 by reducing the moment generated by the cantilever of the optical units 103, 104. The rails 211 are lifted from the base 207 by the guide members 213. This configuration enables the guide members 213 to move the rails 211. The carriage 209 and the guide members 213 are configured such that the base 203 is stationary when no power flows to the base 203, the carriage 209, and the guide members 213.

[0052] The moving mechanism 205, the laser arm assembly 101, and the reflection arm assembly 102 are configured to position the substrate 107 such that the measurement assembly 100 can perform metrology operations on the optical device 109 with high accuracy. The configuration of the laser arm assembly 101 is similar to that of the reflection arm assembly 102 in that at least one or more of the corresponding parts in each of the assemblies 101, 102 are substantially the same. For example, the arms 105, 106, the motors 219, 220, and the base mounts 222, 223 are of substantially the same size, shape, and material. In one or more embodiments, the parts of the reflection arm assembly 102 and the laser arm assembly 101 are substantially the same except for the first optical unit 103 and the second optical unit 104.

[0053] The base that provides a consistent reference plane for the parts of the measurement assembly 100 achieves a high level of accuracy and precision. For example, the base 203 can have a flatness and straightness of 30 microns or less. For example, the flatness and straightness of the base 203 are accurate to 17 microns or less.

[0054] Figure 3 For the measurement assembly 100 according to the embodiments described herein Figure 2 Schematic diagram of the laser arm assembly 101 of the measurement assembly 100.

[0055] The laser arm assembly 101 includes a mounting assembly 400. The mounting assembly 400 includes a motor mount 311, a motor frame 305, a brake 307, and a base mount 223.

[0056] The motor mount 311 is coupled to the laser arm 105. The motor mount 311 is also coupled to the laser motor 219 of the laser arm assembly 101. The laser motor 219 is disposed on the motor frame 305. The motor frame 305 secures the laser motor 219 in place. The motor frame 305 is disposed on the base mount 223. The base mount 223 is disposed between the motor frame 305 and the base 207. The base mount 223 raises the motor frame 305 to provide clearance for the laser arm assembly 101 to rotate and utilize the counterweight 225.

[0057] 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 counterweight 225 is disposed near the second end 105b. For example, the counterweight 225 is coupled to the second end 105b of the laser arm 105.

[0058] The first optical unit 103 is disposed on the laser end 105a of the laser arm 105. The first optical unit 103 may include a housing 301 and an analysis unit 303. In one or more embodiments, the analysis unit 303 is coupled to the housing 301. In one or more embodiments, the analysis unit 303 is disposed within the housing 301. The analysis unit 303 projects a first light beam 131 toward the optical device 109 and / or the substrate 107 ( Figure 1 )). In one or more embodiments, the first light beam is projected toward the axis A1 such that the first light beam 131 is perpendicular to the axis A1. In one or more embodiments, the first light beam 131 starts from the housing 301 and passes through a lens that focuses the first light beam 131 such that the focal point is disposed on the structure 113, the grating 111, the optical device 109, the substrate 107, or other measurement surfaces. The first optical unit 103 further includes one or more sensors that receive the reflected light. For example, the sensors of the first optical unit 103 receive a second light beam 132. The housing 301 of the first optical unit enhances accuracy by providing a more rigid support for the components of the first optical unit 103.

[0059] The motor mount 311 defines a rotation axis. 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 near and / or adjacent to the second end 105b.

[0060] The motor mount 311 is aligned with the axis A1. The above configuration is configured such that the axis A1 is parallel to the base 207. The relationship between the axis A1 and the base enhances accuracy by providing a consistent geometry during calibration and measurement operations.

[0061] 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 for aligning the arms 105, 106. In one or more embodiments, the alignment features 315 are one or more alignment pins disposed on one or more sides of the laser arm 105. In one or more embodiments, the alignment features 315 are one or more holes disposed on one or more sides of the laser arm 105. One or more alignment features 315 are also on the reflecting arm 106 of the reflecting arm assembly 102( Figure 2 ). The alignment features 315 effect calibration of both the reflecting arm assembly 102 and the laser arm assembly 101.

[0062] The brake 307 is coupled to the laser motor 219 and the motor frame 305. In one or more embodiments, the brake 307 is disposed on the motor frame 305 opposite the laser arm 105. In other words, the laser motor 219 is disposed between the laser arm 105 and the brake 307.

[0063] Figure 4 is a schematic cross-sectional view of the mounting assembly 400 according to the embodiments described herein.

[0064] Although previously discussed in the context of the laser arm assembly 101, the one or more embodiments described may also apply to the reflecting arm assembly 102( Figure 1 and Figure 2 ). In one or more embodiments, the motor mount 311 is coupled to the shaft member 403. The motor mount 311 is coupled to the shaft member 403 by one or more pieces of hardware 407. The hardware 407 can be, but is not limited to, screws, bolts, pins, or any other hardware intended to secure two or more bodies together. The shaft member 403 is aligned with the axis A1. The shaft member 403 extends along the axis A1 through the laser motor 219. The laser motor 219 is configured to rotate the shaft member 403 and rotate the motor mount 311.

[0065] In one or more embodiments, the laser motor 219 is coupled to the motor frame 305. The laser motor 219 is coupled to the motor frame 305 by one or more pieces of hardware 407. The laser motor 219 is configured to rotate the shaft member 403 and rotate the motor mount 311 such that the motor mount 311 receives rotation from the shaft member 403.

[0066] The mounting assembly 400 includes a brake 307 and a brake plate 401. The motor frame 305 is disposed between the brake 307 and the brake plate 401. The brake 307 is coupled to the shaft 403. In one or more embodiments, the brake 307 includes a spring 409. The brake 307 and the brake plate 401 are coupled by the spring 409. In one or more embodiments, the brake 307 includes an actuator 405. In one or more embodiments, the brake 307 is a spring brake and the actuator 405 is a normally closed solenoid. For example, the brake is a spring brake coupled to a normally closed solenoid. The brake plate 401 is disposed on the outer surface 305a of the motor frame 305. For example, the inner surface 401a of the brake plate 401 is coupled to the outer surface 305a of the motor frame 305 by hardware 407.

[0067] In one or more embodiments, the actuator 405 is a solenoid that releases the tension on the spring 409 when the actuator 405 receives an electromagnetic signal. For example, when there is no signal to the actuator 405, the spring 409 forces the inner surface 307a to contact the outer surface 401b of the brake plate 401, thereby preventing movement of the brake 307 and the shaft 403. When the actuator 405 receives a signal, the shaft 403 can rotate. The controller 160 ( Figure 1 ) controls when to engage the brake 307 by communicating with the actuator 405. The controller 160 controls the laser arm assembly 101 by closed-loop control, and when the controller 160 loses power and / or receives an error alert, the brake 307 operates as a safety mechanism to lock the laser motor 219 in place. In one or more embodiments, the laser motor 219 optionally controls the actuator 405. In one or more embodiments, the brake 307 and the actuator 405 form a spring brake coupled to a normally closed solenoid.

[0068] 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 encoder 411 provides the angular position of the laser arm assembly 101. The encoder 411 enables the measured movement of the laser arm and the reflector arm to have an angular accuracy and / or repeatability of approximately 30 micro-radians or less. For example, the encoder 411 is accurate to 17 micro-radians. This enhances 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. By using an optical encoder, positioning does not affect the arm position, thereby improving accuracy.

[0069] Figure 5is a flowchart of an optical device metrology method according to an embodiment described herein. The CPU 160a of the controller 160 is configured to execute method 500. Method 500 is a measurement operation stored on the memory 160b of the controller 160.

[0070] At operation 501, the substrate 107 ( Figure 1 ) is moved to a first position. The first position sets the pedestal 203 ( Figure 2 ) such that the grating 111 of the structure 113 or the optical device 109 is ready for a metrology operation. The pedestal 203 can rotate about the X, Y, and / or Z axes to orient the substrate 107 such that the grating 111 of the optical device 109 can be in the path of the first beam 131. The pedestal 203 can translate the substrate along the X, Y, and / or Z axes to orient the substrate 107 such that the grating 111 of the optical device 109 can be on the path of the first beam 131.

[0071] At operation 503, the laser arm assembly 101 rotates to align the first optical unit 103 at an orientation angle substantially perpendicular to the grating 111 on the substrate, and the reflection arm assembly 102 rotates to align the second optical unit 104 at an orientation angle substantially parallel to the first optical device.

[0072] At operation 505, the measurement assembly performs an optical measurement on the first optical device. The optical measurement includes projecting a first beam 131, guiding it from the first optical unit 103 towards the substrate 107 and / or the grating 111 of the 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 towards the second optical unit 104.

[0073] At operation 507, sensors within the first optical unit 103 and the second optical unit 104 image the first optical device. Operations 501, 503, and 505 are repeated until the optical device 109 is imaged and one or more of the pitch, orientation, duty cycle, and reflectivity of the grating 111 are determined.

[0074] Benefits of the present disclosure include being able to fix the laser arm assembly 101 and the reflection arm assembly 102 in place by the brake 307 in the event of a power failure or an unsafe condition. For example, if the housing 150 is opened during operation ( Figure 1)。Another benefit is the ability to use the base 207 and axis A1 as a reference for calibrating the base 203, which enhances accuracy as all components can be referenced outside of a single plane. Another benefit is that the base 203 is capable of translating along and around the X, Y, and Z axes, which is achieved by the configuration of the guides 213 and tracks 211. The similarity of the assemblies 101, 102 ensures that the movement is consistent and repeatable. Specifically, when the assemblies 101, 102 are set closer to a horizontal position, the assemblies 101, 102 experience approximately uniform deflection characteristics. As a result, the assemblies 101, 102 will have uniform errors rather than errors relative to each specific assembly 101, 102. Due to having uniform errors caused by uniform deflection, the root cause analysis of finding the error source and subsequent correction are accelerated.

[0075] 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 the measurement assembly 100, laser arm assembly 101, reflective arm assembly 102, base 203, track 211, guide 213, counterweight 225, Figure 2 the base 207 shown, brake 307, Figure 3 the first optical unit 103 shown, actuator 405, encoder 411, Figure 4 the spring 409 shown, and method 500 may be combined. Additionally, it is contemplated that one or more aspects disclosed herein may include some or all of the benefits mentioned above.

[0076] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from its basic scope, and its scope is determined by the claims that follow.

Claims

1. A laser arm assembly, the laser arm assembly comprising: A laser arm, the laser arm comprising: A motor mount disposed between the laser end and the second end of the laser arm, the motor mount defining a rotation axis; An optical unit coupled to the laser end of the arm, the optical unit including a light source pointing to the rotation axis; A counterweight disposed on the second end of the arm; and A motor coupled to the motor mount of the arm, the motor comprising: A brake; A laser motor shaft coaxial with the rotation axis; and An encoder.

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

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

4. The laser arm assembly according to claim 1, wherein the optical unit further comprises: A multi-axis position module coupled to a hole; And A sensor.

5. The laser arm assembly according to claim 1, wherein the brake is a spring brake coupled to a normally closed solenoid.

6. A measuring assembly, the measuring assembly comprising: A laser arm assembly, the laser arm assembly comprising: A laser arm; A laser motor defining a rotation axis; and A first optical unit disposed on the laser end of the laser arm; A reflecting arm assembly, the reflecting arm assembly comprising: A reflecting arm; A reflecting motor, the reflecting motor including a motor shaft coaxial with the rotation axis of the laser arm; and A second optical unit disposed on the first end of the reflecting arm; and A platform assembly disposed between the laser arm assembly and the reflecting arm assembly, the platform assembly comprising: A base defining a process plane; and A moving mechanism configured to translate the platform assembly.

7. The measuring assembly according to claim 6, further comprising a base, the laser arm assembly, the reflecting arm assembly, and the platform assembly disposed on the base.

8. The measuring assembly according to claim 6, wherein the measurement points of the first optical unit and the second optical unit are the same.

9. The measuring assembly according to claim 6, further comprising a base having tracks disposed substantially perpendicular to the rotation axis.

10. The measuring assembly according to claim 9, wherein the platform assembly is an air bearing platform assembly.

11. The measuring assembly according to claim 6, further comprising a housing disposed around the measuring assembly, the housing including an atmosphere control unit.

12. The measuring assembly according to claim 6, wherein the moving mechanism is configured such that the platform assembly can translate the base parallel to the X-axis, Y-axis, and Z-axis, and rotate the base about the X-axis, Y-axis, and Z-axis.

13. The measuring assembly according to claim 6, wherein the movements of the laser arm, the reflecting arm, and the platform assembly are repeatable, with an angular accuracy of 30 micro-radians or less, and the base has a flatness of 20 microns or less.

14. The measuring assembly according to claim 6, wherein the laser arm and the reflection arm are substantially the same.

15. The measuring assembly according to claim 6, wherein the base further comprises a vacuum chuck.

16. The measuring assembly according to claim 6, wherein the first optical unit is removable.

17. A measuring assembly, the measuring assembly comprising: A laser arm assembly, comprising: A laser arm having a laser end; A laser motor defining a rotation axis; and A first optical unit disposed on the laser end of the laser arm; A reflection arm assembly, comprising: A reflection arm having a first end; A reflection motor including a motor shaft coaxial with the rotation axis of the laser arm assembly; and A second optical unit disposed on the first end of the reflection arm; A platform assembly disposed between the laser arm assembly and the reflection arm assembly, the platform assembly comprising: A base defining a process plane; and A movement mechanism configured to enable the process plane to be coplanar with the rotation axis; A controller for controlling the measuring assembly; and A non-transitory computer-readable medium having instructions stored thereon that, when executed by a processor, cause the process to perform a measurement method, the method comprising: Moving a substrate to a first position; Rotating the laser arm assembly to align the first optical unit at an orientation angle substantially perpendicular to a grating on the substrate; Rotating the reflection arm assembly to align the second optical unit at an orientation angle substantially parallel to the grating; and Performing an optical measurement on the grating.

18. The measuring assembly according to claim 17, wherein the method further comprises: Moving the base to a second position; Rotating the laser arm assembly to align the first optical unit at a second orientation angle substantially perpendicular to a second optical device on the substrate; Rotating the reflection arm assembly to align the second optical unit at the second orientation angle substantially parallel to the second optical device; And Performing a measurement on the second optical device.

19. The measuring assembly according to claim 17, wherein moving the base comprises at least one of: rotating the base about the X-axis, Y-axis, or Z-axis, and translating the base along the X-axis, Y-axis, or Z-axis.

20. The measuring assembly according to claim 17, wherein the method further comprises: Calibrating the measuring assembly by aligning the first optical unit with a node disposed on the base.

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