Method for high resolution, stable measurement of pitch and orientation in optical gratings

Abstract

Embodiments described herein provide a measurement system having an aperture filter member and a method of utilizing the measurement system. A measurement system described herein includes a measurement arm and a platform. The measurement arm projects the light beam onto a top surface of the optics structure. Multiple reflected beams reflected and diffracted from other surfaces of a non-opaque substrate result in interference. The measurement arm includes an aperture (e.g., an aperture filtering member) that filters the multi-reflected beam from the multi-reflected beam being relayed into the detector. Accordingly, only the image of the light beam is relayed to the detector.

Description

[0001] background

[0002] field

[0003] Embodiments of the present disclosure relate to a measurement system. Specifically, embodiments of the present disclosure relate to a measurement system having an aperture filter component and a method using the measurement system.

[0004] Description of Related Technology

[0005] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has an apparent physical presence. The virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display the virtual reality environment in place of the actual environment.

[0006] However, augmented reality enables the experience that the user can still view the surrounding environment through the display lenses of glasses or other HMD devices, but can also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and videos that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality has many challenges and design constraints.

[0007] One such challenge is to display a virtual image superimposed on the surrounding environment. Optics are used to assist in superimposing the image. Manufacturing optics can be challenging because optics tend to have properties that need to be manufactured to specific tolerances, such as optic structure spacing and optic structure orientation. Measurement devices are used to ensure that the intended spacing and orientation are achieved. When measuring optic structures on transparent substrates, conventional systems will experience a decrease in accuracy and repeatability due to multi-reflection beam interferometry. Thus, there is a need in the art for an improved measurement device and method of filtering multi-reflection beams.

[0008] Overview

[0009] In one embodiment, a measurement system is provided. The measurement system includes: a light source configured to project a light beam to a substrate disposed below the light source; a first lens disposed between the substrate and the light source and configured to focus the light beam to the substrate; and a first beam splitter disposed between the first lens and the light source. The measurement system further includes: a second lens disposed adjacent to the first beam splitter and configured to direct the light beam to the second lens, and configured to direct the light beam to a mirror; an aperture disposed in front of the mirror; a second beam splitter configured to direct the light beam from the mirror to a third lens; and a detector, wherein the light beam is projected to the detector by the third lens.

[0010] In another embodiment, a measurement system is provided. The measurement system includes: a platform having a substrate support surface, wherein the platform is coupled to a platform actuator, the platform actuator being configured to move the platform in a scanning path and rotate the platform around an axis; a measurement arm disposed above the platform and configured to direct a light beam to a substrate disposed on the substrate support surface. The measurement arm includes: a light source configured to project a light beam to a substrate disposed below the light source; a first lens disposed between the substrate and the light source and configured to focus the light beam to the substrate; a first beam splitter disposed between the first lens and the light source; a second lens disposed adjacent to the beam splitter and configured to direct the light beam to the second lens; an aperture, wherein the second lens is configured to direct the light beam through the aperture; a third lens; and a detector, wherein the light beam is projected to the detector by the third lens.

[0011] In yet another embodiment, a method is provided. The method includes projecting a light beam from a measuring arm to a first optical device structure, the light beam diffracted from a top surface of the first optical device structure of a substrate, wherein the substrate is disposed on a platform. The method further includes projecting the light beam through an aperture disposed in front of a mirror in the measuring arm, wherein the aperture is operable to only allow the light beam to contact the mirror; relaying a first raw image of the light beam to a detector in the measuring arm; moving the platform along a scanning path; and projecting the light beam to a second optical device structure. The second raw image is relayed to the detector. The method further includes forming a high resolution map of the pitch and orientation angle of at least the first optical device structure and the second optical device structure.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to be able to understand in detail the manner in which the above-mentioned features of the present disclosure are used, a more particular description of the present disclosure briefly summarized above may be made with reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only exemplary embodiments and are not therefore to be considered limiting of their scope, as the present disclosure may admit to other equally effective embodiments.

[0014] Figure 1is a schematic diagram of a measurement system according to one embodiment.

[0015] Figure 2A is a schematic side view of a first configuration of a measuring arm according to an embodiment.

[0016] Figure 2B is a schematic side view of a second configuration of the measuring arm according to an embodiment.

[0017] Figure 3A is a schematic diagram of a first light beam and a second light beam according to one embodiment.

[0018] Figure 3B is a schematic top view of a detector according to one embodiment.

[0019] Figure 4 is a flow chart of a method for determining a change in pitch P and a change in orientation angle φ using a measurement system according to an embodiment described herein.

[0020] FIG. 5A to FIG. 5F is a schematic side view of a configuration of a measuring arm according to one embodiment.

[0021] Figure 5G is a schematic side view of a sixth configuration of a measuring arm and a reflecting arm according to one embodiment.

[0022] To facilitate understanding, identical reference numerals have been used, where possible, to identify identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0023] Specific description

[0024] Embodiments of the present disclosure relate to a measurement system having an aperture filter component and a method of using the measurement system. The measurement system includes a platform and a measurement arm. Light projected from the measurement arm is reflected from a substrate disposed on the platform, and light reflected from the substrate surface is incident on the measurement arm. When the orientation and / or spacing of the optical device structure changes, the offset of the image projected to the detector will shift. The embodiments disclosed herein may be particularly useful for, but not limited to, measuring local uniformity in an optical system.

[0025] Figure 11 is a schematic diagram of a measurement system 101 according to one embodiment. As shown, the measurement system 101 includes a platform 102 and a measurement arm 104. In some embodiments, a reflective arm 112 is included in the measurement system 101. The arm actuator is configured to rotate the reflective arm 112 around the z-axis and scan the reflective arm 112 in the z-direction. The measurement system 101 is configured to diffract the light projected by the measurement arm 104. The light projected by the measurement arm 104 is guided at a substrate 103 disposed above the platform 102. The light beam reflected and diffracted from the substrate 103 is incident on the measurement arm 104. The measurement arm 104 is disposed above the platform 102. The reflective arm 112 is disposed above the platform 102.

[0026] As shown, the platform 102 includes a support surface 106 and a platform actuator 108. The platform 102 is configured to fix a substrate 103 on the support surface 106. In one embodiment that can be combined with other embodiments described herein, the substrate 103 is a transparent substrate. The platform 102 is coupled to the platform actuator 108. The platform actuator 108 is configured to move the platform 102 in a scanning path 110 along the x-direction and the y-direction. The platform actuator 108 is also configured to rotate the platform 102 around the z-axis. The platform 102 is configured to move and rotate the substrate 103 in the scanning path so that the light beam projected from the measurement arm 104 is incident on different portions or gratings of the substrate 103 during operation of the measurement system 101.

[0027] The substrate 103 includes one or more optical devices 105 having one or more gratings 107 of an optical device structure 109. Each of the gratings 107 includes a region of the optical device structure 109. Each of the optical device structures 109 has an orientation angle φ and a pitch P (shown in FIG. 2 ). The pitch P is defined as the distance between adjacent points, such as adjacent first edges or adjacent centroids of the optical device structures 109. The pitch P and the orientation angle φ of the optical device structure 109 for the first grating 111 may be different from the pitch P and the orientation angle φ of the optical device structure 109 for the second grating 113 of the one or more gratings 107. In addition, due to local warping or other deformations of the substrate 103, there may be local pitch P' variations and local orientation angle φ' variations of the optical device structure 109. The measurement system 101 may be used to measure the pitch P and the orientation angle φ of the optical device structure 109 for each of the gratings 107 for each of the optical devices 105. The substrate 103 may be a single crystal wafer of any size, such as having a radius from about 150 mm to about 450 mm.

[0028] The measurement arm 104 and the platform 102 communicate with a controller 130. The controller 130 facilitates control and automation of the method for measuring the pitch P and orientation angle φ of the optical device structure 109 described herein. The controller may include a central processing unit (CPU) (not shown), a memory (not shown), and support circuits (or I / O) (not shown). The CPU may be one of any form of computer processor used in industrial settings to control various processes and hardware (e.g., motors and other hardware) and monitor processes (e.g., transfer device position and scan time). The memory (not shown) is connected to the CPU and may be readily available memory such as random access memory (RAM). Software instructions and data may be encoded and stored in the memory for instructing the CPU. Support circuits (not shown) are also connected to the CPU for supporting the processor. The support circuits may include cache, power supplies, clock circuits, input / output circuit systems, subsystems, and the like. The program (or computer instructions) readable by the controller determines which tasks may be performed on the substrate 103. The program may be software readable by the controller and may include code for monitoring and controlling, for example, the position of the substrate and the position of the measurement arm.

[0029] Figure 2A 2 is a schematic side view of a first configuration 200A of the measurement arm 104. The measurement arm 104 is configured to direct a light beam 202 toward the substrate 103. The measurement arm 104 is configured to measure a pitch P and an orientation angle φ of an optical device structure 109 formed on the substrate 105. The optical device structure 109 forms a grating 107. The light beam 202 is projected onto a top surface 201 of the optical device structure 109 to be measured. As shown in FIG. 2 , the light beam 202 is projected onto a plurality of optical device structures 109 of the grating 107.

[0030] In embodiments where the substrate 103 is non-opaque (e.g., transparent), which can be combined with other embodiments described herein, the multiple reflected beams 204 of light will be reflected from at least the bottom surface 203 of the substrate 103. When the measurement arm 106 is used, the multiple reflected beams 204 cause interference. The interference will cause an asymmetric image of the light beam 202, for example, the image of the light path diffracted or reflected from the substrate 103 is not circular or substantially circular, which reduces the measurement accuracy of the pitch P and the orientation angle φ. To solve this problem, the measurement system 101 uses an aperture filtering component to reduce interference.

[0031] The first configuration 200A of the measuring arm 104 includes a light source 206, a first lens 208, a first beam splitter 210, a second lens 212, an aperture 214, a mirror 216, a second beam splitter 218, a third lens 220, and a detector 222. The measuring arm 104 and the controller 130 ( Figure 1 The controller 130 is configured to facilitate the operation and movement of the measurement arm 104. The measurement arm 104 may also include an arm actuator 224 ( Figure 1 ). The arm actuator 224 is configured to rotate the measuring arm 104 around the z-axis and scan the measuring arm in the z-direction. The measuring arm 104 may also be fixed when performing measurements.

[0032] The light source 206 is configured to project a light beam 202 toward the substrate 103. For example, the light source 206 is an LED or a laser. The light source operates in a wavelength range from about 400 nm to about 700 nm. For example, the light source 206 is an LED light source operating at one of 450 nm, 530 nm, or 650 nm. The light beam 202 is projected at a beam angle θ relative to the bottom surface 203 of the substrate 103. In one embodiment that may be combined with other embodiments described herein, the light beam 202 is a collimated laser beam. In another embodiment that may be combined with other embodiments described herein, the light beam 202 has a circular or substantially circular cross-section (e.g., Figure 3A As depicted by first arrow 240, light beam 202 is projected from light source 206, transmitted through first beam splitter 210 (some light beam 202 is reflected from first beam splitter 210), and projected by first lens 208 to optical device structure 109.

[0033] The light source 206 projects the light beam 202 toward the first lens 208. The first lens 208 is a converging lens or a focusing lens that focuses the light beam 202. The first lens 208 is adjacent to the substrate 103. The first lens 208 is disposed between the light source 206 and the substrate 103. The first lens 208 is configured to focus the light beam 202 on the top surface 201 of the optical device structure 109 to be measured. The optical device structure 109 causes a phase change of the light beam 202 after reflection from the optical device structure 109. The first lens 208 is configured to focus the light beam 202, for example, to reduce the beam diameter of the light beam 202, to improve the spatial resolution of the measuring arm 104. In addition, the improved spatial resolution will better distinguish the light beam 202 from the multi-reflected beam 204.

[0034] The light beam 202 is diffracted from the top surface 201 of the optical device structure at a beam angle θ. As depicted by the second arrow 242, the light beam 202 is projected through the first lens 208 toward the first beam splitter 210 and onto the mirror 216. The first beam splitter 210 reflects the light beam 202 to the second lens 212 (some of the light beam 202 is transmitted through the first beam splitter 210). The first beam splitter 210 is disposed between the first lens 208 and the light source 206. The second lens 212 is disposed between the second beam splitter 218 and the aperture 214. The second lens 212 is a converging lens that focuses the light beam 202.

[0035] The second lens 212 focuses the light beam 202 onto a reflective surface 226 of the mirror 216. The second lens 212 directs the light beam 202 through an aperture 214. The aperture 214 is disposed in front of the mirror 216. The aperture 214 is positioned so as to allow the light beam 202 to pass through the aperture 214 to contact the reflective surface 226. The aperture 214 includes an aperture size 215. The aperture size 215 is determined based on a predetermined spatial resolution of the result. For example, the aperture size 215 is about 50 μm to about 1 mm.

[0036] Mirror 216 reflects light beam 202 to second beam splitter 218. As depicted by third arrow 244, the light beam reflects from mirror 216 through second lens 212, second beam splitter 218 reflects light beam 202 to third lens 220 (some of light beam 202 is transmitted through second beam splitter 218), and is projected to detector 222. Second beam splitter 218 is disposed adjacent to mirror 216. Third lens 220 is disposed adjacent to detector 222. Third lens 220 is disposed between second beam splitter 218 and detector 222.

[0037] The third lens 220 relays the raw image at the Fourier plane 228 to the detector 222. The third lens 220 is a relay lens. The third lens 220 may be a single lens or a plurality of lenses. The Fourier plane 228 is disposed between the second beam splitter 218 and the second lens 212. The raw image of the light beam 202 at the Fourier plane 228 is projected to the detector 222. The detector 222 relays the raw image at the Fourier plane 228 to observe the shift in the chief ray angle of the light beam 202 projected to the different optical device structures 109 ( Figure 3A and Figure 3B Detector 222 is any optical device known in the art for detecting light, such as a charge-coupled device (CCD) array or an active pixel sensor (CMOS array).

[0038] The position of Fourier plane 228 is defined as the Fourier plane of mirror 216 and the plane on substrate 103. Fourier plane 228 is the relayed image of the original profile of beam 202 and the original image relayed to detector 222. When the spacing changes, Fourier plane 228 and the original image on detector 222 will shift, but the position of beam 202 on substrate 103 and mirror 216 will not shift.

[0039] Since the substrate 103 is non-opaque, when the light source 206 projects light through the substrate 103, multiple reflection beams 204 are formed. Figure 2A As shown, the multi-reflected beam 204 is diffracted from the bottom surface 203 of the substrate 103. Due to diffraction from the bottom surface 203 (and in some embodiments, from other optical device structures 109 or the upper surface of the substrate 103), the multi-reflected beam 204 is not projected along the same path through the measurement arm 104 as the light beam 202. For example, Figure 2A As shown, the multi-reflected beam 204 is directed to the second lens 212 via the first beam splitter 210. The second lens 212 focuses the multi-reflected beam 204 toward the mirror 216. The second lens 212 is adjacent to the aperture 214. However, the aperture 214 filters the multi-reflected beam 204 from contacting the mirror 216. The aperture 214 is positioned so that the multi-reflected beam 204 will not contact the reflective surface 226. The multi-reflected beam 204 will have an image point that exceeds the image point of the beam 202. The multi-reflected beam 204 will also be offset from the beam 202. Thus, the aperture 214 filters the multi-reflected beam 204 from being relayed to the detector 222. The precision and accuracy of the original image relayed to the detector 222 will be improved without interference from the multi-reflected beam 204.

[0040] Figure 2B2 is a schematic side view of a second configuration 200B of the measuring arm 104. The second configuration 200B of the measuring arm 104 includes a light source 206, a first lens 208, a first beam splitter 210, a second lens 212, an aperture 214, a mirror 216, a third lens 220, a detector 222, a first linear polarizer 230, a second linear polarizer 232, a first wave plate 234, and a second wave plate 236. The first linear polarizer 230, the second linear polarizer 232, the first wave plate 234, and the second wave plate 236 are configured to increase the efficiency of the light beam in the measuring arm 104 and reduce the light beam reflected between the components of the measuring arm 104. The first linear polarizer 230, the second linear polarizer 232, the first wave plate 234, and the second wave plate 236 are interchangeable to accommodate a predetermined wavelength. For example, the first wave plate 234 and the second wave plate 236 can be quarter wave plates. Compared to the first configuration 200A, the second configuration 200B allows for a compact design. However, the first linear polarizer 230 , the second linear polarizer 232 , the first wave plate 234 , and the second wave plate 236 are included to avoid undesired beam diffraction and reflection within the measurement arm 104 .

[0041] The light source 206 is configured to project a light beam 202 toward the substrate 103. The light beam 202 is projected at a beam angle θ relative to the bottom surface 203 of the substrate 103. In one embodiment that may be combined with other embodiments described herein, the light beam 202 is a collimated laser beam. In another embodiment that may be combined with other embodiments described herein, the light beam 202 has a circular or substantially circular cross-section (e.g., Figure 3A 246 ) and / or projected shape. As depicted by the first arrow 246, the light beam 202 is projected from the light beam 206 to the first linear polarizer 230, transmitted through the first beam splitter 210 (some of the light beam 202 is reflected from the first beam splitter 210), passed through the first wave plate 234, and projected by the first lens 208 to the optical device structure 109. The first beam splitter 210 is a polarized beam splitter. The first linear polarizer 230, the second linear polarizer 232, the first wave plate 234, and the second wave plate 236 maximize the efficiency of the light beam 202 transmitted to the substrate 103, so that the light beam 202 remains along the path defined by the first arrow 246. The first linear polarizer 230 is disposed between the light source 206 and the first beam splitter 210. The first wave plate 234 is disposed between the first beam splitter 210 and the first lens 208. The first beam splitter 210 will transmit a polarized light beam and reflect another polarized light beam. The first linear polarizer 230 , the second linear polarizer 232 , the first wave plate 234 , and the second wave plate 236 change the polarization of the light beam 202 before contacting the first beam splitter 210 to control whether the light beam 202 is reflected or transmitted by the first beam splitter 210 .

[0042] The light source 206 projects the light beam 202 toward the first lens 208. The first lens 208 is a converging lens that focuses the light beam 202. The first lens 208 is adjacent to the substrate 103. The light beam 202 is projected from the first linear polarizer 230 to the first lens 208. The first lens 208 is configured to focus the light beam 202 on the top surface 201 of the optical device structure 109 to be measured. The first lens 208 is configured to focus the light beam 202, for example, to reduce the beam diameter of the light beam 202, to improve the spatial resolution of the measuring arm 104. In addition, the improved spatial resolution will better distinguish the light beam 202 from the multi-reflected beam 204. The optical device structure 109 causes a phase change of the light beam 202 after reflection from the optical device structure 109. The first lens 208 is disposed between the first wave plate 234 and the substrate 103.

[0043] The light beam 202 is diffracted from the top surface 201 at a beam angle θ. As depicted by the second arrow 248, the light beam 202 is projected through the first lens 208 toward the first beam splitter 210 and onto the mirror 216. After reflection, the light beam 202 passes through the first lens 208 and the first wave plate 234 before contacting the first beam splitter 210. The first beam splitter 210 reflects the light beam 202 to the second wave plate 236, passes through the second lens 212, and reflects to the mirror 216. The second wave plate 236 is disposed between the second lens 212 and the first beam splitter 210. The first linear polarizer 230, the second linear polarizer 232, the first wave plate 234, and the second wave plate 236 maximize the efficiency of the light beam 202 reflected to the mirror 216 so that the light beam 202 remains along the path defined by the second arrow 248.

[0044] The second lens 212 is disposed between the second wave plate 236 and the aperture 214. The first beam splitter 210 is disposed between the first linear polarizer 230, the second linear polarizer 232, the first wave plate 234, and the second wave plate 236. The distance between the first lens 208 and the second lens 212 is defined by the sum of each respective focal length. The second lens 212 focuses the light beam 202 onto the reflective surface 226 of the mirror 216. The second lens 212 directs the light beam 202 through the aperture 214. The aperture 214 is disposed in front of the mirror 216. The aperture 214 is positioned so as to allow the light beam 202 to contact the reflective surface 226. The aperture 214 includes an aperture size 215.

[0045] Mirror 216 reflects light beam 202 to detector 222. As depicted by third arrow 250, the light beam reflects from mirror 216, passes through second lens 212, passes through second wave plate 236, first beam splitter 210 transmits light beam 202 (some of light beam 202 is transmitted through second beam splitter 218) to second linear polarizer 232 and third lens 220, and is projected to detector 222. The second linear polarizer is disposed between first beam splitter 210 and third lens 220. First linear polarizer 230, second linear polarizer 232, first wave plate 234, and second wave plate 236 maximize the efficiency of light beam 202 transmitted to detector 222, such that light beam 202 remains along the path defined by third arrow 250.

[0046] The third lens 220 relays the raw image at the Fourier plane 228 to the detector 222. The third lens 220 is adjacent to the detector 222. The third lens 220 is disposed between the second linear polarizer 232 and the detector 222. The raw image of the light beam 202 at the Fourier plane 228 is projected to the detector 222. The detector 222 is any optical device in the art for detecting light, such as a charge coupled device (CCD) array or an active pixel sensor (CMOS array).

[0047] Since the substrate 103 is non-opaque, when the light source 206 projects light through the substrate 103, multiple reflection beams 204 are formed. Figure 2B As shown, the multi-reflected beam 204 is diffracted from the bottom surface 203 of the substrate 103. Due to diffraction from the bottom surface 203 (and in some embodiments, from other optical device structures 109), the multi-reflected beam 204 is not projected along the same path through the measurement arm 104 as the light beam 202. For example, Figure 2B As shown, the multi-reflected beam 204 is directed to the second lens 212 via the first beam splitter 210. The second lens 212 focuses the multi-reflected beam 204 toward the mirror 216. The second lens 212 is adjacent to the aperture 214. However, the aperture 214 filters the multi-reflected beam 204 from contacting the mirror 216. The aperture 214 is positioned so that the multi-reflected beam 204 will not contact the reflective surface 226. The multi-reflected beam 204 will have an image point that exceeds the image point of the beam 202. The multi-reflected beam 204 will also be offset from the beam 202. Thus, the aperture 214 filters the multi-reflected beam 204 from being relayed to the detector 222. The precision and accuracy of the original image relayed to the detector 222 will be improved without interference from the multi-reflected beam 204.

[0048] Figure 3A is a schematic diagram of the first light beam 302 and the second light beam 304. In one example, the first light beam 302 and the second light beam 304 correspond to Figure 2A and Figure 2BIn another example, the first light beam 302 and the second light beam 304 correspond to FIG. 5A to FIG. 5G Light beam 502 is shown. To facilitate explanation, Figure 3A refer to Figure 2A and Figure 2B describe.

[0049] The first light beam 302 corresponds to a beam projected onto a first optical device structure (eg, Figure 2A and Figure 2B The first beam 302 is projected by the measuring arm 104 to measure the pitch P and orientation angle φ of the first optical device structure. The second beam 304 corresponds to the beam projected onto the second optical device structure (e.g., Figure 2A and Figure 2B The second optical device structure 109 is shown as a light beam 202. The second light beam 304 is projected by the measuring arm 104 to measure the pitch P and the orientation angle φ of the second optical device structure.

[0050] like Figure 3A As shown, the first light beam 302 includes a first chief ray angle (CRA) 306 defined as the centerline of the first light beam 302. The second light beam 304 includes a second CRA 308 defined as the centerline of the second light beam 304. Figure 2A and Figure 2B As discussed, the raw image at the Fourier plane 228 is relayed to the detector 222 in the measurement arm 104 of the measurement system 101. The detector 222 is configured to detect an offset 310 between the positions of the first CRA 306 and the second CRA 308 on the Fourier plane 228. The offset 310 corresponds to a change in the spacing P and the orientation angle φ between the first optics structure and the second optics structure.

[0051] Figure 3B is a schematic top view of the detector 222. To facilitate explanation, Figure 3B refer to Figure 2A and Figure 2B Description, however, it is expected that the first detector 522 and the second detector 534 are still Figure 3B The detector 222 includes a first light beam 302 and a second light beam 304. The first light beam 302 and the second light beam 304 are reflected by the third lens 220 ( Figure 2A and Figure 2B 2) is relayed from the Fourier plane 228 to the detector 222. The offset 310 between the first CRA 306 and the second CRA 308 corresponds to a pitch change, for example, a change from a pitch P to a pitch P' ( Figure 2A and Figure 2B), and a change in orientation angle φ, for example, a change from orientation angle φ to orientation angle φ' ( Figure 2A and Figure 2B ). The detector 222 includes only the first light beam 302 and the second light beam 304. Figure 2A and Figure 2B The aperture 214 shown filters the multi-reflected beam 204, and the detector 222 is able to detect the first beam 302 and the second beam 304 without interference. Reducing interference on the aperture 214 increases precision, accuracy, and reliability when determining the pitch P and the orientation angle φ.

[0052] The offset 310 has an x-component 312 and a y-component 314. In one embodiment that may be combined with other embodiments described herein, the x-component 312 corresponds to a change in pitch and the y-component corresponds to a change in orientation angle φ. In another embodiment that may be combined with other embodiments described herein, the x-component 312 corresponds to a change in orientation angle φ and the y-component corresponds to a change in pitch. The pitch direction and the orientation direction may be pre-calibrated by adjusting the measurement arm 104 and the platform 102. The offset 310 is decomposed into a predefined pitch direction and an orientation direction. The pitch and orientation angle φ are determined at least in part using a software algorithm executed by a controller 130 in communication with the measurement system 101. Utilizing the measurement system 101 will allow a high resolution map of the pitch P and the orientation angle φ to be formed in a two-dimensional region of the substrate 103.

[0053] Figure 4 4 is a flow chart of a method 400 for determining a change in spacing P and a change in orientation angle φ using the measurement system 101. In one example, the method 400 may be performed by the first configuration 200A or the second configuration 200B of the measurement system 101. In another example, the method 400 may be performed by the following FIG. 5A to FIG. 5G The method 400 is performed in the illustrated configurations 500A-500G of the measurement system 101. To facilitate explanation, the method 400 will be described with reference to the first configuration 200A of the measurement system 101. The controller 130 is operable to facilitate the operation of the method 400.

[0054] In operation 401, a light beam 202 is projected onto a first optical device structure. The light beam 202 is projected from a light source 206 onto a top surface 201 of the first optical device structure. The light beam 202 is diffracted from the top surface 201 of the first optical device structure.

[0055] At operation 402, the light beam 202 is projected through the aperture 214. The mirror 216 is disposed behind the aperture 214. The light beam is operable to be projected through the aperture 214. The image point of the light beam 202 is located on the reflective surface 226 of the mirror 216. The aperture 214 is positioned so that the light beam 202 is allowed to contact the reflective surface 226. The aperture 214 filters out the multi-reflected beam 204 from contacting the mirror 216. The aperture 214 is positioned so that the multi-reflected beam 204 will not contact the reflective surface 226. Filtering the multi-reflected beam 204 will allow for improved precision, accuracy, and reliability of measuring the raw image that will be relayed to the detector 222.

[0056] At operation 403, the raw image of the beam 202 is relayed to the detector 222. The mirror 216 reflects the beam 202 to the detector 222 via the second beam splitter 218. The third lens 220 relays the raw image at the Fourier plane 228. The beam 202 includes the first CRA 306 ( Figure 3A and Figure 3B In addition, the original image is recorded from the detector 222. The original image is saved to the controller 130.

[0057] In operation 404, the platform 102 moves along the scanning path 110 ( Figure 1 The platform 102 is moved so that the measuring arm 104 is arranged so that the light beam 202 can be projected onto the second optical device structure.

[0058] At operation 405 , operations 401 - 404 are repeated for at least a second optical device structure. Operations 401 - 404 are repeated until raw images of a predetermined number of optical device structures have been acquired by the detector 222 .

[0059] At operation 406, a high resolution map of pitch P and orientation angle φ is formed. The high resolution map has improved accuracy, precision, and reliability due to aperture 214 filtering out interference from multiple reflected beams 204. In addition, controller 130 applies an algorithm to the raw image and generates a high resolution map of pitch P and orientation angle φ.

[0060] Figure 5A5 is a schematic side view of a third configuration 500A of the measuring arm 104. The measuring arm 104 is configured to direct a light beam 502 toward a substrate 103. The measuring arm 104 is configured to measure a pitch P and an orientation angle φ of an optical device structure 109 formed on the substrate 103. The optical device structure 109 forms a grating 107. The light beam 502 is projected onto a top surface 201 of the optical device structure 109 to be measured. As shown in FIG. 5 , the light beam 502 is projected onto a plurality of optical device structures 109 of the grating 107. In an embodiment in which the substrate 103 is non-opaque (e.g., transparent), which can be combined with other embodiments described herein, a multi-reflected beam 504 of light will be reflected from at least the bottom surface 203 of the substrate 103. When the measuring arm 104 is used, the multi-reflected beam 504 causes interference. To address this problem, the measuring system 101 utilizes an aperture filtering component to reduce interference.

[0061] The third configuration 500A of the measurement arm 104 includes a light source 506 , a first lens 508 , a first beam splitter 510 , a second lens 512 , an aperture 514 , a reticle 516 , a third lens 520 , and a first detector 522 .

[0062] Light source 506 is configured to project light beam 502 toward substrate 103. Light source 506 operates in a wavelength range from about 250nm to about 530nm. Light beam 502 is projected at a beam angle θ relative to bottom surface 203 of substrate 103. In one embodiment that can be combined with other embodiments described herein, light beam 502 is a collimated laser beam. As depicted by first arrow 540, light beam 502 is projected from light source 506, transmitted through first beam splitter 510 (some light beam 502 is reflected from first beam splitter 510), and projected to optical device structure 109 by first lens 508. Reticle 516 is arranged between first beam splitter 510 and light source 506. Reticle 516 includes a mark thereon. The mark may be a cross, a circle, a triangle, or other suitable shapes. Reticle 516 can adjust light beam 502 to project the mark onto substrate 103. The marking will help locate the center of the beam 502 and will allow for easier tracking on the first detector 522, resulting in improved measurement performance.

[0063] The light source 506 projects the light beam 502 toward the first lens 508. The first lens 508 is a converging lens that focuses the light beam 502. The first lens 508 is adjacent to the substrate 103. The first lens 508 is disposed between the light source 506 and the substrate 103. The first lens 508 is configured to focus the light beam 502 on the top surface 201 of the optical device structure 109 to be measured. The raw image of the top surface 201 of the optical device to be measured will be associated with the first detector 522. The optical device structure 109 causes a phase change of the light beam 502 after reflection from the optical device structure 109. The first lens 508 is configured to focus the light beam 502, for example, to reduce the beam diameter of the light beam 502, to improve the spatial resolution of the measuring arm 104. In addition, the improved spatial resolution better distinguishes the light beam 502 from the multi-reflected beam 504.

[0064] The light beam 502 is diffracted from the top surface 201 of the optical device structure at a beam angle θ. As depicted by the second arrow 542, the light beam 502 is projected through the first lens 508 toward the first beam splitter 510 and onto the mirror 216. The first beam splitter 510 reflects the light beam 502 to the second lens 512 (some of the light beam 502 is transmitted through the first beam splitter 502, for example, 50% of the light beam 502 is transmitted). The first beam splitter 510 is disposed between the first lens 508 and the light source 506. The second lens 512 is disposed between the first beam splitter 510 and the aperture 514. The second lens 512 is a converging lens that focuses the light beam 502.

[0065] The second lens 512 focuses the light beam 502 through the aperture 514. The aperture 514 is disposed between the second lens 512 and the third lens 520. The aperture 514 is positioned so as to allow the light beam 502 to pass through the aperture 514. In one embodiment that can be combined with other embodiments described herein, the aperture 514 can be perpendicular to the projection direction of the light beam 502 (e.g., perpendicular to the second arrow 542). In another embodiment that can be combined with other embodiments described herein, the aperture 514 can be at an aperture angle relative to the projection direction of the light beam 502 (e.g., not perpendicular to the second arrow 542).

[0066] exist Figure 5AThe aperture 514, illustrated in dashed lines, has an aperture angle. The aperture angle can be predetermined based on the beam angle θ. The aperture angle of the aperture 514 improves the alignment of the aperture 514 relative to the top surface 201 of the optical device structure 109. The predetermined aperture angle will ensure that the aperture 514 allows the original image focused on the top surface 201 of the optical device structure 109 to pass therethrough and preferably blocks the light beam 502 from undesired areas of the top surface 201 of the optical device structure 109. The aperture position of the aperture 514 can then be determined. The aperture position is selected to ensure that the original image to be captured is aligned in the XY plane on the substrate 103. The aperture position is also adjusted to ensure that the mark is projected through the aperture 514 to the first detector 522.

[0067] The third lens 520 is adjacent to the first detector 522. The third lens 520 is disposed between the aperture 514 and the first detector 522. The third lens 520 relays the raw image at the Fourier plane 528 to the first detector 522. The third lens 520 may be a single lens or a plurality of lenses. The Fourier plane 528 is disposed between the first beam splitter 510 and the second lens 512. The raw image of the light beam 502 at the Fourier plane 528 is projected to the first detector 522. The first detector 522 relays the raw image at the Fourier plane 528 to observe the shift in the chief ray angle of the light beam 502 projected to the different optical device structures 109 ( Figure 3A and Figure 3B shown).

[0068] The aperture 514 filters the multi-reflected beam 504 from contacting the first detector 522. The multi-reflected beam 504 will have an image point that is beyond or in front of the image point of the beam 502. The multi-reflected beam 504 will also be offset from the beam 502. Thus, the aperture 514 filters the multi-reflected beam 504 from being relayed to the first detector 522. The precision and accuracy of the original image relayed to the first detector 522 is improved without interference from the multi-reflected beam 504.

[0069] Figure 5B 5 is a schematic side view of a fourth configuration 500B of the measuring arm 104. The fourth configuration 500B of the measuring arm 104 is similar to the third configuration 500A. However, in the fourth configuration 500B, the light beam 502 contacting the first beam splitter 510 after being incident on the top surface 201 of the optical device structure 109 is directed to the mirror 524. The light beam 502 is directed to the mirror 524 via the second lens 512.

[0070] The second lens 512 focuses the light beam 502 onto the reflective surface 526 of the mirror 524. The second lens 512 directs the light beam 502 through an aperture 514. The aperture 514 is disposed in front of the mirror 524. The aperture 514 is positioned so as to allow the light beam 502 to contact the reflective surface 526 through the aperture 514.

[0071] Mirror 524 reflects beam 502 to second beam splitter 518. As depicted by third arrow 544, beam 502 reflects from mirror 524 through second lens 512, and second beam splitter 518 reflects beam 502 to first detector 522 (some beam 502 is transmitted through second beam splitter 518).

[0072] In the fourth configuration 500B, the first lens 508 is used to project and collect the light beam 502. The top surface of the first lens 508 reflects the light beam 502 into a path indicated by a second arrow 542. This portion of the light beam 502 does not pass through the substrate 103, but is collected by the first detector 522.

[0073] Figure 5C 500C is a schematic side view of the fifth configuration 500C of the measuring arm 104. The fifth configuration 500C of the measuring arm 104 includes all the elements described above about the third configuration 500A. However, the fifth configuration 500C includes a first lens 508 disposed between the first beam splitter 510 and the reticle 516. The fifth configuration 500C further includes a fourth lens 530. The fourth lens 530 is disposed between the aperture 514 and the first detector 522. The fourth lens 530 is configured to collect the light beam 502. The fifth configuration 500C allows minimization of the reverse reflection from the first lens 508 back to the light beam 502. Thus, the signal-to-noise ratio is improved. The distance from the reticle 516 to the first lens 508 is equal to the focal length of the first lens 508. In the fifth configuration 500C, the first lens 508 (projection lens) and the second lens 512 (collection lens) are separated, so the reflection from the top surface of the first lens 508 will not proceed to the first detector 522. Thereby, back reflections are reduced.

[0074] Figure 5D500D is a schematic side view of a sixth configuration 500D of the measuring arm 104. The sixth configuration 500D of the measuring arm 104 includes all of the elements described above with respect to the fifth configuration 500C plus a second beam splitter 518, a fifth lens 532, and a second detector 534. The second beam splitter 518 is disposed between the aperture 514 and the fifth lens 532. The fifth lens 532 is disposed between the second beam splitter 518 and the second beam splitter 518. The light beam 502 passes through the aperture 514 and is incident on the second beam splitter 518 (as indicated by the second arrow 542). The second beam splitter 518 reflects the light beam 502 to the fourth lens 530 (some of the light beam 502 is transmitted through the second beam splitter 518, for example, 50% of the light beam 502 is transmitted, as indicated by the third arrow 544). The light beam 502 transmitted through the second beam splitter 518 is directed to the fifth lens 532. The fifth lens 532 directs the light beam 502 to the second detector 534. The second detector 534 is disposed at an angle relative to the projection direction of the light beam 502 (eg, at an angle relative to the third arrow 544).

[0075] Including the second detector 534 allows for monitoring the alignment of the substrate 103 and the aperture 514. In particular, the configuration facilitates monitoring the aperture position and monitoring how the light beam 502 is focused on the top surface 201 of the optics structure 109. The fifth lens 532 relays the raw image to the second detector 534 to ensure that the top surface 201 of the optics structure 109 and the aperture 514 are aligned as intended. Thus, the second detector 534 is used to monitor focus changes by scanning the substrate 103.

[0076] Figure 5E 5 is a schematic side view of a seventh configuration 500E of the measuring arm 104. The seventh configuration 500E of the measuring arm 104 includes all of the elements described above with respect to the sixth configuration 500D plus a third beam splitter 538 and a fourth beam splitter 546. The third beam splitter 538 is disposed between the light source 506 and the reticle 516. The fourth beam splitter 546 is disposed between the first detector 522 and the fourth lens 530. The light beam 502 is projected from the light source 506 and is incident on the third beam splitter 538. The third beam splitter 538 reflects the light beam 502 to form a reference beam 548. Some of the light beam 502 is transmitted through the third beam splitter 538 to the reticle 516. The seventh configuration 500E includes an aperture 514 having an aperture angle.

[0077] Reference beam 548 is included to generate an interference pattern between light beam 502 and reference beam 548 directly from light source 506. The interference pattern will be displayed on first detector 522, which will have improved contrast to better locate the markings of reticle 516. Without reference beam 548, the markings on first detector 522 will be blurred, which limits the sharpness of the original image and the accuracy of the system. Generating interference fringes on second detector 534 will help locate the markings more accurately.

[0078] Fig. 5F 5 is a schematic side view of an eighth configuration 500F of the measuring arm 104. The eighth configuration 500F of the measuring arm 104 includes all the elements described above with respect to the seventh configuration 500E, however, the first detector 522 and the fourth lens 530 are removed. Compared to the seventh configuration, the second beam splitter 518 reflects the light beam 502 to the fifth lens 532. The fifth lens 532 relays the light beam 502 to the second detector 534. The second detector 534 is arranged at an angle relative to the projection direction of the light beam 502 (e.g., at an angle relative to the second arrow 542). The reference beam 548 will display an interference pattern on the second detector 534. The spacing and orientation of the fringes indicate the spacing / orientation of the optical device structure 109 on the substrate 103.

[0079] Figure 5G 1 is a schematic side view of a sixth configuration 500G of the measuring arm 104 and the reflecting arm 112. The sixth configuration 500G of the measuring arm 104 is described above. The reflecting arm 112 includes a first reflecting arm lens 562, a second reflecting arm lens 564, a third reflecting arm lens 566, a reflecting arm detector 568, and a reflecting arm aperture 570. The reflecting arm 112 is operable to measure a reflected beam 560 reflected from the top surface 201 of the optical device structure 109 to be measured. In one example, the reflecting arm 112 is disposed directly opposite the measuring wall 104. Although in Figure 5G While the reflective arm 112 is illustrated in the sixth configuration 500G with the measurement arm 104 , any configuration of the measurement arm 104 may be paired with the reflective arm 112 .

[0080] The reflection arm aperture 570 is disposed between the second reflection arm lens 564 and the third reflection arm lens 566. The reflection arm aperture 570 is positioned so as to allow the reflected beam 560 to pass through the reflection arm aperture 570. In one embodiment that can be combined with other embodiments described herein, the reflection arm aperture 570 can be perpendicular to the projection direction of the reflected beam 560 (e.g., perpendicular to the propagation direction of the reflected beam 560). In another embodiment that can be combined with other embodiments described herein, the reflection arm aperture 570 can have a reflection aperture angle relative to the projection direction of the reflected beam 560.

[0081] The third reflector arm lens 566 relays the reflected beam 560 from the second reflector arm lens 564 to a reflector arm detector 568. The reflector arm detector 568 is operable to obtain data regarding a platform condition of the platform 102. The reflector arm 112 will monitor the angular changes from the platform 102 as it is scanned so that the effects of the platform condition (e.g., the platform tipping or tilting) during scanning are excluded from the measurements obtained using the measurement arm 104. The reflector arm 112 collects the reflected beam from the substrate 103 and can collect data regarding the curvature of the substrate 103. The reflector arm 112 serves as a reference for the data determined in the measurement arm 104.

[0082] In summary, a measurement system with an aperture filter component and a method using the measurement system are described herein. The measurement system described herein includes a measurement arm and a platform. The measurement arm projects a light beam onto the top surface of an optical device structure. Multiple reflected beams obtained by reflection and diffraction from other surfaces of a non-opaque substrate cause interference. The measurement arm includes an aperture (e.g., an aperture filter component) that filters the multiple reflected beams so as not to be relayed to a detector. Therefore, only an image of the light beam is relayed to the detector. The image allows measurement of spacing and orientation angles across substrates. The aperture allows the accuracy, precision, and reliability of the measurement to be improved by filtering interference from the multiple reflected beams.

[0083] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A measurement system, include: a light source configured to project a light beam onto a substrate disposed below the light source; a first lens disposed between the substrate and the light source, the first lens being configured to focus the light beam onto the substrate; A first beam splitter is arranged between the first lens and the light source; a second lens disposed adjacent to the first beam splitter, the first beam splitter being configured to direct the light beam to the second lens, the second lens being configured to direct the light beam to a mirror; an aperture, disposed in front of said mirror; a second beam splitter configured to direct the light beam from the mirror to a third lens; and A detector, wherein the light beam is projected by the third lens onto the detector.

2. The measurement system of claim 1, wherein the first lens is a focusing lens.

3. The measurement system of claim 1, wherein the third lens is configured to relay a raw image of the light beam at a Fourier plane to the detector, wherein the Fourier plane is formed adjacent to the second lens.

4. The measurement system of claim 1, wherein the aperture has a pore size between about 50 μm and about 1 mm. 5 . The measurement system of claim 1 , further comprising a reticle disposed between the first beam splitter and the light source.

6. The measurement system of claim 5, wherein the reticle includes markings thereon, wherein the markings are cross-shaped, circular, or triangular.

7. The measurement system of claim 1, wherein the detector is a charge coupled device (CCD) array or an active pixel sensor (CMOS array).

8. A measurement system, include: a stage having a substrate supporting surface, the stage coupled to a stage actuator configured to move the stage in a scan path and to rotate the stage about an axis; and A measuring arm is disposed on the platform, the measuring arm being configured to direct a light beam to a substrate disposed on the substrate supporting surface, the measuring arm comprising: a light source configured to project the light beam onto the substrate disposed below the light source; a first lens disposed between the substrate and the light source, the first lens being configured to focus the light beam onto the substrate; A first beam splitter is arranged between the first lens and the light source; a second lens disposed adjacent to the first beam splitter, the first beam splitter being configured to direct the light beam to the second lens; an aperture, the second lens being configured to direct the light beam through the aperture; A third lens; and A detector, wherein the light beam is projected onto the detector by the third lens.

9. The measurement system of claim 8, wherein the first lens is a focusing lens.

10. The measurement system of claim 8, wherein the third lens is configured to relay a raw image of the light beam at a Fourier plane to the detector, wherein the Fourier plane is disposed adjacent to the second lens.

11. The measurement system of claim 8, wherein the measurement arm is coupled to an arm actuator configured to scan the measurement arm and rotate the measurement arm around the axis.

12. The measuring system of claim 8, wherein the measuring arm further comprises: a first linear polarizer disposed adjacent to the light source; a second linear polarizer, disposed between the beam splitter and the third lens; a first wave plate, disposed between the beam splitter and the first lens; and The second wave plate is arranged between the second lens and the beam splitter.

13. The measurement system of claim 8, wherein the detector is a charge coupled device (CCD) array or an active pixel sensor (CMOS array).

14. The measurement system of claim 8, further comprising a reflective arm disposed above the platform.

15. The measurement system of claim 14, wherein the reflective arm is coupled to an arm actuator configured to scan the measurement arm and rotate the measurement arm around the axis.

16. The measurement system of claim 15, wherein the reflective arm include: a first reflector arm lens; a second reflector arm lens, adjacent to the first reflector arm lens; A third reflector arm lens; a reflective arm aperture, disposed between the second reflective arm lens and the third reflective arm lens; and A reflector arm detector, wherein the third reflector arm lens directs the reflected beam to the reflector arm detector.

17. The measurement system of claim 8, wherein the aperture is arranged at an aperture angle, wherein the aperture angle is non-perpendicular to a projection direction of the light beam.

18. A method, The following steps are involved: projecting a light beam from the measuring arm to a first optical device structure, the light beam diffracting from a top surface of the first optical device structure of a substrate, the substrate being disposed on a platform; projecting the light beam through an aperture disposed in front of a mirror in the measuring arm, the aperture being operable to allow only the light beam to contact the mirror; relaying a first raw image of the light beam to a detector in the measuring arm; moving the stage along a scan path and projecting the beam to a second optics structure where a second raw image is relayed to the detector; and A high resolution map of the pitch and orientation angles of at least the first optics structure and the second optics structure is formed.

19. The method of claim 18, wherein multiple reflected beams formed by the light beam reflected from at least a bottom surface of the substrate are filtered out by the aperture.

20. The method of claim 18, further comprising: The following steps are involved: An aperture position of the aperture is determined, wherein the aperture position is determined to align the first original image in an XY plane on the substrate.

Images