Method for determining line angle and rotation of multiple patterns

Abstract

Disclosed herein are methods and apparatus for determining line angles and line angle rotations of raster or line features. One aspect of the disclosure involves using a measurement tool to measure coordinate points of a first line feature, determining a first slope of the first line feature from the coordinate points, and determining a first line angle from the slope of the first line feature. This process can be repeated to find a second slope of a second line feature adjacent to the first line feature. The slopes of the first and second line features can be compared to find the line angle rotation. The line angle rotation is compared to design specifications to determine the quality of the stitching.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to apparatus and methods for optical device fabrication. More particularly, embodiments of the present disclosure relate to apparatus and methods for measuring the splicing quality of grating structures incorporated in waveguides. Background Art

[0002] Virtual reality is generally considered a computer-generated simulated environment in which the user has a tangible physical presence. Virtual reality experiences can be generated in three dimensions (3D) and viewed using 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 as a substitute for the real environment.

[0003] However, augmented reality enables an experience in which the user still sees their surroundings through the display lenses of glasses or other HMD devices, but also sees virtual images of objects generated for display and appearing as part of that environment. Augmented reality can include any type of input, such as audio or tactile input, as well as virtual images, graphics, and video that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality has many challenges and design limitations.

[0004] One challenge is to display a virtual image superimposed on the surrounding environment. Waveguides are used to assist in superimposing the image. The generated light propagates through the waveguide until the light exits the waveguide and is superimposed on the surrounding environment. Manufacturing waveguides can be challenging because waveguides tend to have non-uniform properties. A common issue in manufacturing waveguides is the ability to measure the stitching quality of the grating lines. Previous attempts at measuring stitching quality have proven to be expensive and time consuming. Therefore, what is needed in the art is an improved method and system for quantifying the stitching quality of grating lines on a grating structure. Summary of the Invention

[0005] In one embodiment, a method for measuring line angles is provided. The method includes selecting a field of view of a grating structure, identifying a line feature using a measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, wherein the primary coordinate includes a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate. A secondary coordinate is measured along the line feature, wherein the secondary coordinate includes a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measurement between the theoretical line feature and a reference axis is calculated.

[0006] In another embodiment, a method for measuring a line angle rotation of a grating structure is provided. The method includes measuring a first line angle. Measuring the first line angle includes selecting a field of view of the grating structure, identifying a line feature using a measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, and the primary coordinate includes a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate. A secondary coordinate is measured along the line feature, and the secondary coordinate includes a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measurement between the theoretical line feature and a reference axis is calculated. A second line angle is measured using the same method used to measure the first line angle. A difference between the first and second line angles is calculated to determine the line angle rotation, and the line angle rotation is compared to a design specification line angle measurement.

[0007] In another embodiment, a method for measuring line angle rotation of a grating structure is provided. The method includes positioning a measurement tool to measure a first image exposure in the grating structure. The method further includes measuring a first line angle. Measuring the first line angle includes selecting a field of view of the grating structure, identifying a line feature using the measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, and the primary coordinate includes a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate. A secondary coordinate is measured along the line feature, and the secondary coordinate includes a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measurement between the theoretical line feature and a reference axis is calculated. The measurement tool is positioned to measure a second image exposure in the grating structure. A second line angle is measured using the same method used to measure the first line angle. A difference between the first and second line angles is calculated to determine the line angle rotation, and the line angle rotation is compared to a design specification line angle measurement. The quality of the splicing is determined from a difference between the first line angle and the second line angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Thus, in order to understand in detail the manner in which the above-described features of the present disclosure may be understood, a more particular description of the disclosure, briefly summarized above, may be obtained by reference to its embodiments, some of which are illustrated in the accompanying drawings. It will be noted, however, that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, which may admit to other equally effective embodiments.

[0009] Figure 1Illustrated is a plan view of a waveguide combiner according to an embodiment of the present disclosure.

[0010] Figure 2 A schematic plan view illustrating a plurality of gratings formed by two adjacent image exposures according to an embodiment of the present disclosure is shown.

[0011] Figure 3 Schematic plan view illustrating a grating and measurement characteristics of the grating according to an embodiment of the present disclosure.

[0012] Figure 4 A schematic diagram illustrating an interface boundary between two adjacent line features according to an embodiment of the present disclosure.

[0013] Figure 5 The operation of a method for determining line angles of grating lines according to an embodiment of the present disclosure is illustrated.

[0014] Figure 6 The operation of a method for determining the stitching quality of a grating structure according to an embodiment of the present disclosure is illustrated.

[0015] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0016] Aspects of the present disclosure relate to apparatus and methods for determining line angles and the quality of stitching of grating structures. In one example, line angles are determined by measuring discrete coordinates along a line feature. In another example, line angle rotation is determined by measuring the line angles of multiple adjacent line grating segments.

[0017] Figure 1 A plan view of a waveguide combiner 100 is shown, in accordance with an embodiment of the present disclosure. It will be understood that the waveguide combiner 100 described below is an exemplary waveguide combiner, and that other waveguide combiners having different designs may benefit from the embodiments described herein. The waveguide combiner 100 includes an input coupling region 102 defined by a plurality of gratings 108, an intermediate region 104 defined by a plurality of gratings 110, and an output coupling region 106 defined by a plurality of gratings 112. Grating segments 120 of the plurality of gratings 112 are located within the output coupling region 106. The grating segments 120 encompass a small portion of the entire output coupling region 106 and will be described in greater detail below. The input coupling region 102 receives an incident light beam having an intensity (virtual image) from a microdisplay.

[0018] Each grating (such as a fin structure or the like) of the plurality of gratings 108 separates the incident light beam into multiple modes, each having one mode. The zero-order mode (T0) beam is reflected back or transmitted through the waveguide combiner 100, the positive first-order mode (T1) beam is coupled into the intermediate region 104 through the waveguide combiner 100, and the negative first-order mode (T-1) beam propagates in the waveguide combiner 100 in the opposite direction of the T1 beam. Ideally, these incident light beams are separated into T1 beams having the full intensity of the incident light beams so as to direct the virtual image toward the intermediate region 104. One approach to separating the incident light beams into T1 beams having the full intensity of the incident light beams is to employ fins (including the gratings 108) with tilted angles to suppress the T-1 and T0 beams. The T1 beams undergo total internal reflection (TIR) ​​through the waveguide combiner 100 until they contact the plurality of gratings 110 in the intermediate region 104. A portion of the in-coupling region 102 may have a grating 108 with a tilt angle that is different from the tilt angle of the grating 108 from an adjacent portion of the in-coupling region 102 .

[0019] The T1 beam contacts the fins of the plurality of gratings 110. The T1 beam is split into a T0 beam that is reflected back or transmitted through the waveguide combiner 100, a T1 beam that undergoes TIR in the intermediate region 104 until it contacts another fin of the plurality of gratings 110, and a T-1 beam that is coupled to the output coupling region 106 by the waveguide combiner 100. The T1 beam that undergoes TIR in the intermediate region 104 continues to contact the gratings of the plurality of gratings 110 until the intensity of the T1 beam coupled to the intermediate region 104 by the waveguide combiner 100 is exhausted, or until the remaining T1 beam propagating through the intermediate region 104 reaches the end of the intermediate region 104.

[0020] The plurality of gratings 110 are tuned to control the T1 beam coupled into the intermediate region 104 through the waveguide combiner 100, thereby controlling the intensity of the T-1 beam coupled into the output coupling region 106. This modulates the field of view of the virtual image generated by the microdisplay as viewed from the user's perspective and increases the viewing angle at which the user can view the virtual image. One approach to controlling the T1 beam coupled into the intermediate region 104 through the waveguide combiner 100 is to adjust the tilt angle of each fin of the plurality of gratings 110 to control the intensity of the T-1 beam coupled into the output coupling region 106. A portion of the intermediate region 104 may have gratings 110 having a tilt angle that is different from the tilt angle of gratings 110 in adjacent portions of the intermediate region 104. Furthermore, the gratings 110 may have fins having a tilt angle that is different from the tilt angle of the fins of the gratings 108.

[0021] The T-1 beams coupled to the output coupling region 106 by the waveguide combiner 100 undergo TIR in the waveguide combiner 100 until they contact one of the plurality of gratings 112, where they are split into TO beams that are reflected back or transmitted through the waveguide combiner 100. The T1 beams undergo TIR in the output coupling region 106 until they contact another fin of the plurality of gratings 112 and are coupled out of the waveguide combiner 100. The T1 beams that undergo TIR in the output coupling region 106 continue to contact the fins of the plurality of gratings 112 until the intensity of the T-1 beams coupled to the output coupling region 106 by the waveguide combiner 100 is exhausted, or until the remaining T1 beams propagating through the output coupling region 106 have reached the end of the output coupling region 106. The plurality of gratings 112 are tuned to control the T-1 beam coupled to the output coupling region 106 through the waveguide combiner 100, thereby controlling the intensity of the T-1 beam coupled out of the waveguide combiner 100, thereby further modulating the field of view of the virtual image generated by the microdisplay observed from the user's perspective and further increasing the viewing angle at which the user can view the virtual image.

[0022] One approach to controlling the T-1 beam coupled to the output coupling region 106 through the waveguide combiner 100 is to manipulate the tilt angle of each fin of the plurality of gratings 112 to further modulate the field of view and increase the viewing angle. A portion of the intermediate region 104 may have gratings 110 with a tilt angle that differs from the tilt angle of the fins of the gratings 110 in an adjacent portion of the intermediate region 104. Furthermore, the gratings 112 may have fins with a tilt angle that differs from the tilt angles of the fins of the gratings 108 and 110. In some embodiments, the structures in 108, 110, and 112 are 2D patterns, such as rotated elongated pillars, via features, or cylinders.

[0023] Figure 2 A schematic plan view of a plurality of gratings 112 formed by two image exposures is shown in accordance with an embodiment of the present disclosure. Figure 2 exist Figure 1 1 and 2. A grating segment 120 is shown in FIG. 1 as encompassing a portion of the output coupling region. The grating segment 120 is shown with reference to the x-coordinate, the y-coordinate, and the z-coordinate. The plurality of gratings 112 includes a grating structure 200. The grating structure 200 includes a first set of line features 204 formed by a first image exposure and a second set of line features 206 formed by a second image exposure. The first set of line features 204 and the second set of line features 206 intersect at a junction 202. The junction 202 can be considered the point where the two sets of line features 204, 206 join together during processing. The junction 202 results from using multiple masks or image exposures to create the grating structure 200.

[0024] Using multiple masks to create the grating structure 200 significantly reduces the cost of mask design and fabrication. Some attempts have been made to create masks large enough to create multiple gratings 112 covering the entire output coupling region 106, but using a single mask has proven prohibitively expensive. Current methods for fabricating multiple gratings 112 employ multiple masks or reuse the same mask to pattern the grating structure 200. For example, the grating structure 200 is formed into multiple segments, including a first segment S1 and a second segment S2. The first and second segments S1, S2 can be described as being image-wise exposed. The first segment S1 includes a first set of line features 204, while the second segment S2 includes a second set of line features 206. In some embodiments, additional segments are used and these additional segments are joined together by the junctions 202 between the segments. These additional segments can be joined together to form the entire plurality of gratings 112 within the output coupling region 106. The stitching process described above with respect to the plurality of gratings 112 and the output coupling region 106 may be similarly applied to the plurality of gratings 108 and the input coupling region 102 , or the plurality of gratings 110 and the intermediate region 104 .

[0025] Each line feature 204, 206 includes a line angle θ1, θ2, respectively. The first line angle θ1 is defined as the angle between the plurality of gratings 112 within the first set of line features 204 and the x-axis. The second line angle θ2 is defined as the angle between the plurality of gratings 112 within the second set of line features 206 and the x-axis. Representative line angles θ1 and θ2 are shown on the bottom gratings of each of segments S1 and S2. However, the line angles θ1 and θ2 are determined for each of the plurality of gratings 112 in segments S1 and S2. In some embodiments, individual line angles θ1 and θ2 are determined for each of the plurality of gratings 112 within the first and second segments S1 and S2. Based on this, a line angle measurement relative to the x-axis can be obtained for each grating. The line angle measurements within segment S1 are averaged to determine a first average line angle. The line angle measurements within segment S2 are averaged to determine a second average line angle.

[0026] In an alternative embodiment, the line angles θ1, θ2 are calculated relative to the y-axis. These line angles can be found relative to any line or axis within the same plane as the line angles, as long as the axis is used consistently for all line angle measurements. The consistent use of a line or axis as a reference line provides a common reference point to enable comparisons between line angle measurements.

[0027] Figure 3 Schematic plan view illustrating a grating and measurement characteristics of the grating according to an embodiment of the present disclosure. Figure 3 Further illustrating the field of view 300 of the measurement tool. In some embodiments, the measurement tool comprises a scanning electron microscope. The field of view 300 comprises a grating structure. The grating structure may be similar to Figure 2 grating structure 200 is shown in FIG. Within the field of view 300 of the measurement tool are line features 302. The measurement tool is capable of identifying one or more line features 302. Figure 3 The line feature 302 may be similar to that for Figure 1 and Figure 2 Any of the plurality of gratings 112 described. Although Figure 3 Only one line feature 302 is shown, with the understanding that there will be multiple line features 302 within the field of view 300 of the measurement tool at a given moment. The measurement tool is part of a measurement tool assembly that is capable of distinguishing between line features 302, such that when there are multiple line features 302 within the field of view 300, the measurement tool can lock focus on one line feature 302. The measurement tool assembly distinguishes between the line features by utilizing a line tracking program. The line tracking program can be part of a controller or computer that measures data from the measurement tool. Figure 3 The line feature 302 in question is a segment of the line feature 302, such as Figure 2 Line features 204 and 206 in . Figure 3 Only one line feature 302 is shown in FIG. In another embodiment (not shown here), the line feature is in the shape of an elongated rod, a cylinder, or a via.

[0028] Line feature 302 can be measured using discrete coordinate point measurements along a central axis running through the long end of line feature 302. For example, these discrete coordinate point measurements include primary coordinate 320, secondary coordinate 330, tertiary coordinate 340, and n-level coordinate 350. The n-level coordinate represents any coordinate in the coordinate sequence that follows tertiary coordinate 340. In some embodiments, the n-level coordinate is a quaternary coordinate, a quinary coordinate, a hexalevel coordinate, or greater. Figure 3There may be discrete coordinate points (not shown) in the image. Coordinates 320, 330, 340, and 350 are located at the center of the measurement zones. Primary coordinate 320 is located at the center of first measurement zone 304. Secondary coordinate 330 is located at the center of second measurement zone 306. Tertiary coordinate 340 is located at the center of third measurement zone 308. The nth-level coordinate is located at the center of nth measurement zone 310. The starting point along line feature 302 can be primary coordinate 320 or the intersection of the line feature 302 closest to primary coordinate 320 and the edge of field of view 300. Alternatively, the starting point can be a point between primary coordinate 320 and the intersection of the line feature 302 closest to primary coordinate 320 and the edge of field of view 300. The distance from the edge of field of view 300 intersecting with line feature 302 to primary coordinate 320 is less than approximately 500 nm, such as less than 400 nm, such as less than 300 nm. In some embodiments, the distance from the edge of the field of view 300 that intersects the line feature 302 to the primary coordinate 320 is between about 300 nm and about 400 nm, such as about 350 nm. In some embodiments, the distance from the edge of the field of view 300 that intersects the line feature 302 to the starting point is less than about 400 nm, such as less than about 350 nm, such as less than about 250 nm, or such as less than 150 nm.

[0029] In some embodiments, the primary coordinate 320, secondary coordinate 330, tertiary coordinate 340, and nth-level coordinate 350 can all be measured relative to an x-axis and a y-axis. The x-axis and the y-axis can be any xy reference axes selected by the user. In this embodiment, the primary coordinate 320 includes a first x-coordinate and a first y-coordinate, and the first x-coordinate is a first distance from the edge of the field of view 300 to the primary coordinate 320. In this embodiment, the origin of the y-axis and the x-axis is the edge of the field of view 300. The edge of the field of view 300, including the y-axis, is parallel to the edge of the line feature 302. The y-axis can also be in the same plane as the z-axis. The y-coordinate of the primary coordinate is any y-coordinate along the y-axis.

[0030] Secondary coordinate 330 includes a second x-coordinate and a second y-coordinate, and the second x-coordinate is a second distance from the edge of field of view 300 to secondary coordinate 330. The second x-coordinate and the second y-coordinate are found using the same x-axis and y-axis used to find the first x-coordinate and the first y-coordinate.

[0031] Tertiary coordinate 340 includes a third x-coordinate and a third y-coordinate, and the third x-coordinate is a third distance from the edge of field of view 300 to tertiary coordinate 340. The third x-coordinate and the third y-coordinate are found using the same x-axis and y-axis used to find the first x-coordinate and the first y-coordinate.

[0032] The n-th x-coordinate 350 includes an n-th x-coordinate and an n-th y-coordinate, and the n-th x-coordinate is the n-th distance from the edge of the field of view 300 to the n-th x-coordinate 350. The n-th x-coordinate and the n-th y-coordinate are found using the same x-axis and y-axis used to find the first x-coordinate and the first y-coordinate.

[0033] Each of the primary, secondary, tertiary, and nth-level coordinates are found relative to each other and using the same x-axis and the same y-axis. Alternative methods may utilize a coordinate system other than the xy axis, such as a radial coordinate system.

[0034] First separation distance 312 is the distance between first measurement zone 304 and second measurement zone 306. Second separation distance 314 is the distance between second measurement zone 306 and third measurement zone 308. In some embodiments, first separation distance 312 and second separation distance 314 are the same distance. Alternatively, first separation distance 312 and second separation distance 314 are different distances, such that first separation distance 312 is smaller than second separation distance 314. In another embodiment, first separation distance 312 is larger than second separation distance 314.

[0035] There can be subsequent spacing distances between each measurement zone until the nth measurement zone 310. In this embodiment, the spacing distances 312, 314, and so on between each measurement zone can be the same distance or different distances. In some embodiments, the distances between each measurement zone alternate between a first spacing distance 312 and a second spacing distance 314. In some embodiments, the spacing distances 312, 314 between each measurement zone 304, 306, 308, and 310 are between about 200 nm and about 2000 nm. For example, the spacing distances 312, 314 between each measurement zone 304, 306, 308, and 310 are between about 500 nm and about 1500 nm, such as between about 750 nm and about 1250 nm. In some embodiments, each measurement zone 304, 306, 308, and 310 is considered a region of interest. Figure 3 In the illustrated embodiment, the measurement areas 304 , 306 , 308 , and 310 are measurement blocks having two sets of parallel lines forming a closed parallelogram.

[0036] Another measurement utilized is inner zone length 318. Inner zone length 318 is the distance from coordinates 320, 330, 340, and 350 to the edges of measurement zones 304, 306, 308, and 310 that are perpendicular to line feature 302. For example, inner zone length 318 is the distance from primary coordinate 320 to the edge of first measurement zone 304 that is perpendicular to line feature 302. This inner zone length 318 can be taken from either side of the line feature 302. Regardless of which edge of first measurement zone 304 it is taken from, inner zone length 318 will be the same because primary coordinate 320 is located at the center of measurement zone 304. When the edge of measurement zone 304 is perpendicular to line feature 302, twice inner zone length 318 is the distance from the edge of first measurement zone 304 to the opposite edge of measurement zone 304. The same method can be used to measure inner zone length 318 within any of the other measurement zones 306, 308, and 310. In some embodiments, the inner zone length 318 is the same for all measurement zones 304 , 306 , 308 , 310 and coordinates 320 , 330 , 340 , 350 .

[0037] This inner zone length can be added to the spacing distances 312 and 314 in various combinations to represent the total distance between one coordinate point and another. In one embodiment, the total distance between the primary coordinate 320 and the secondary coordinate 330 is twice the first spacing distance 312 plus the inner zone length 318. The total distance between the secondary coordinate 330 and the tertiary coordinate 340 is twice the second spacing distance 314 plus the inner zone length 318. This relationship remains the same for all subsequent distances between coordinate points.

[0038] In some embodiments, the total distance between each set of adjacent coordinate points is the same. The total distance between each set of adjacent coordinate points can be pre-set or automatically determined by a controller programmed to determine the measurement distance. In various examples, there can be a pre-set distance for inner zone length 318. In some embodiments, inner zone length 318 is pre-set while spacing distances 312 and 314 vary. Spacing distances 312 and 314 can vary automatically to reduce noise or can have a preset variation pattern. In some embodiments, spacing distances 312 and 314 vary between each measurement zone to optimize the measurement position relative to the entire line feature 302. This allows measurements to be taken within a specific range on the line feature 302. For example, it may not be desirable to measure near the edge of the line feature 302. The user may wish to obtain data at a set distance from the edge of each set of line features 302.

[0039] In some embodiments, the total distance between a set of adjacent coordinates is between about 200 nm and about 2000 nm, for example, between about 500 nm and about 1500 nm, such as between about 750 nm and about 1250 nm. In some embodiments, the total distance between a set of adjacent points approaches 1000 nm.

[0040] A variable distance 316 may also be determined. The variable distance 316 is the distance from a reference axis to the line feature 302 at any given point along the line feature 302. In some embodiments, the variable distance 316 is described as the x-coordinate of a point along the line feature 302. The reference axis is any axis that is parallel to the line feature 302 and in the same plane as the line feature 302. In some embodiments, the reference axis is an edge of the field of view 300 that is parallel to the line feature 302. In yet another embodiment, the reference axis may be any axis that is parallel to the line feature 302, as long as the same axis is used when measuring all points along a segment of the line feature 302. In some embodiments, the same reference axis may be used for one segment of the line feature 302 as for another segment of the line feature. In this embodiment, the reference axis used for Figure 2 The reference axis of segment S1 will be used for Figure 2 In some embodiments, the reference axis may be the same reference axis used for segment S1 as the reference axis used for segment S2. However, the two reference axes are parallel to each other.

[0041] Variable distances 316 are found for each coordinate point along the line feature 302, such that a first variable distance is found between the reference axis and the primary coordinate, a second variable distance is found between the reference axis and the secondary coordinate, a third variable distance is found between the reference axis and the tertiary coordinate, and an nth variable distance is found between the reference axis and the nth coordinate.

[0042] like Figure 3 As shown in FIG, line feature 302 is a 2D line feature 360. 2D line feature 360 ​​can be a rotation of an elongated column, a cylinder, a through-hole feature, or any other suitable 2D pattern. In this embodiment, Figure 3 The line feature 302 shown in is the central axis of the 2D line feature 360 ​​. Figure 3 2D line feature 360 ​​is shown as a rectangle, but it is generally understood that 2D line feature 360 ​​can be any two-dimensional shape. Such two-dimensional shapes include elongated rods of revolution, cylinders, and through-hole features. In embodiments where line feature 302 is 2D line feature 360 ​​and the line feature 302 being measured is the central axis of the 2D line feature, the central axis is parallel to the length 370 of 2D line feature 360. The length 370 of 2D line feature 360 ​​is further defined as the long edge of 2D line feature 360.

[0043] Figure 4Schematic diagram of an interface boundary between two adjacent line features 302 according to an embodiment of the present disclosure. The interface boundary 400 includes two adjacent groups of line features 302 and a junction point 410 between the two adjacent groups of line features 302. The two adjacent groups of line features 302 may be similar to Figure 2 The first set of line features 204 and the second set of line features 206. Similar to Figure 2 ,like Figure 2 As shown in FIG, the first and second groups of line features 204 and 206 are grouped into segment 1S1 and segment 2S2.

[0044] The example interface boundary 400 has a first segment and a second segment, the first segment having a first segment length 406 and the second segment having a second segment length 408. The first segment length 406 and the second segment length 408 approach or are equal to the distance from a junction point on a first end 420 of a group of line features 302 to another junction point (not shown) on a second end 422 of the same group of line features 302. The junction point 410 is the point where the two groups of line features 302 meet. Each group of line features 302 has a set of measurement points 402 and 404. Segment S1 includes the measurement point 402 and segment S2 includes the measurement point 404. The measurement points 402 and 404 are any of the primary coordinates 320, the secondary coordinates 330, the tertiary coordinates 340, and the n-level coordinates 350 and points therebetween. Each of the measurement points 402 and 404 has a Figure 4 4 and 5. Reference arrows 416 and 418 are shown in FIG. 5 to indicate the positions of each of measurement points 402 and 404 on the horizontal axis. A first set of reference arrows 416 is shown in section S1, while a second set of reference arrows 418 is shown in section S2. Reference arrows 416 and 418 are oriented perpendicular to line feature 302.

[0045] A first edge distance 412 is calculated by taking the distance between the intersection point 410 and the first point of the first set of measurement points 402. The first point of the first set of measurement points 402 can be defined as the point in the first set of measurement points 402 that is closest to the intersection point 410. A second edge distance 414 is calculated by taking the distance between the intersection point 410 and the first point in the second set of measurement points 404. The first point in the second set of measurement points 404 can be defined as the point in the second set of measurement points 404 that is closest to the intersection point 410. This can be more easily seen by observing the intersection point 410 and the sets of reference arrows 416 and 418. The first intersection between the measurement points 402, 404 and the sets of reference arrows 416, 418 can be measured as the first and second edge distances 412, 414.

[0046] First edge distance 412 and second edge distance 414 may be within a range between approximately 100 nm and approximately 500 nm, such as between approximately 200 nm and approximately 400 nm. In one embodiment, either first edge distance 412 or second edge distance 414 is approximately 350 nm. Measurements are generally not taken within first edge distance 412 or second edge distance 414 from junction point 410. This is because points within this range of interface boundary 400 contain a significant amount of noise and variation. This noise can significantly distort the data collected from measurement points 402 and 404. First edge distance 412 and second edge distance 414 are selected to reduce noise while still maintaining accurate measurements.

[0047] Will note that although Figure 4 , 18 measurement points 402, 404 are shown, but other numbers of measurement points 402, 404 may be used. The minimum number of measurement points 402, 404 that can be used is two measurement points 402, 404. The number of measurement points 402, 404 ranges from approximately two measurement points 402, 404 to approximately 50 measurement points 402, 404. The number of measurement points 402, 404 can generally be described as a plurality of measurement points 402, 404. In one example, the number of measurement points 402, 404 is increased to obtain a larger amount of data.

[0048] Figure 5 The operations of method 500 for determining line angles of grating lines according to an embodiment of the present disclosure are illustrated. Operation 510 includes using a measurement tool to trace a line feature. The measurement tool may be a scanning electron microscope. The line feature may be as described above and shown in FIG. Figure 1 and Figure 2 The line feature may also be a set of line features 204 and 206. In this embodiment, multiple line features may be tracked at any given moment. The line feature may also be a set of line features 204 and 206. Figure 3 and Figure 4 FIG. 302 depicts a line feature.

[0049] In operation 520, the distance between each region of interest is set. In the current embodiment, the region of interest is referenced Figure 3 The measurement zones in question are 304, 306, 308, and 310. The distance between the regions of interest may be either a first separation distance 312 or a second separation distance 314. The set distance between the regions of interest is predetermined so that a sufficient number of measurements are taken to ensure correct measurement results.

[0050] At operation 530, Cx and Cy values ​​are found along the line feature. The Cx and Cy values ​​are equal to or approximately equal to the x and y coordinates of each coordinate point. This includes primary, secondary, tertiary, and n-level coordinates, so that at least three or more coordinate points are measured. Cx and Cy values ​​can be found relative to any xy axis, as long as these axes are used consistently for all coordinate measurements of the line feature.

[0051] In operation 540, the slope and line angle of the line feature are found using the set of coordinate points found in operation 530. The set of coordinate points is used to graph a theoretical line feature within a computer or controller. The slope of the theoretical line feature is calculated using a mathematical formula or program within the computer or controller. In some embodiments, the slopes of multiple line features within a single segment are calculated after graphing multiple theoretical line features. If multiple theoretical line feature slopes are calculated, the slopes of the multiple theoretical line features are averaged to create an average theoretical line feature slope.

[0052] The line angle of each theoretical line feature can also be calculated using this slope. The line angle of each theoretical line feature is calculated using a mathematical formula and program in a computer or controller.

[0053] As mentioned above, it is possible to utilize measurements from a single line feature, or a group of line features. One advantage of utilizing measurements from a single line feature is that measurements from a single line feature are more efficient and utilize less processing power to complete these measurements. An advantage of utilizing measurements from a group of line features is that the measurements can be averaged, which can provide more accurate and reliable measurements.

[0054] Figure 6 The operations of a method 600 for determining the stitching quality of a grating structure according to an embodiment of the present disclosure are illustrated. Operation 610 includes determining a line angle for two separate line features, operation 620 includes calculating the difference in line angle between the first and second line features to find a line angle rotation, operation 630 includes comparing the line angle rotation to design specifications, and operation 640 includes determining the stitching quality.

[0055] At operation 610, line angles are calculated for a plurality of line features. Calculating the line angles involves finding the line angles for two line features (or multiple additional line features if the average line feature slope within a segment is taken). These line angles are determined using the method described in method 500. Operation 610 differs from method 500 in that the slopes and line angles for lines in a plurality of adjacent segments are measured and calculated. The steps described in method 500 must be completed a second time for a second set of three or more coordinates, which are found for a second line feature in a separate, but adjacent, line feature segment.

[0056] In operation 620, a difference is calculated between a first line angle of the line feature of the first segment and a second line angle of the line feature of the second segment. In operation 620, the difference is obtained by subtracting one of the first or second line angles from the other. The result of the difference between the first and second line angles is defined as a line angle rotation.

[0057] In operation 630, the line angle rotation found in operation 620 is compared to a design specification. The design specification can be the maximum line angle rotation allowed in the raster. In some embodiments, the design specification can be as small as 1 / 100 of a degree or less, such as 1 / 250 of a degree or less, 1 / 500 of a degree or less, or 1 / 1000 of a degree or less. The line angle rotation is compared to the design specification by determining whether the calculated line angle rotation is less than the design specification, greater than the specification, or approximately equal to the specification.

[0058] At operation 640, the quality of the stitching process is determined. The degree to which the line angle is rotated compared to the design specification determines the quality of the stitching process. The quality of the stitching process can be determined on any specified scale. In some embodiments, the quality of the stitching process can be a pass or fail decision, such that if the line angle is rotated less than the design specification, the quality of the stitching process is considered sufficient to pass. If the line angle is rotated greater than the design specification, the quality of the stitching process is considered to be failed. Operation 640 can be calculated on a computer and displayed on a digital interface display, or operation 640 can be performed by manually checking whether the stitching process falls within the expected design specifications. Other methods of determining the quality of the stitching process are also conceivable, such as grading the quality of the stitching process on a scale of 1 to 100% or 1 to 10.

[0059] It is generally understood that the line features referenced in the above description may be two-dimensional line features in some embodiments. For example, line features 204, 206, 302, and 360 may be 2D line features.

[0060] 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, which is determined by the claims that follow.

Claims

1. A method for determining the splicing quality of a grating structure incorporated in a waveguide, the method comprising the following steps: Select the field of view of the grating structure; Use measurement tools to identify line features; selecting a starting point along the line feature; measuring a primary coordinate, the primary coordinate comprising a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate; measuring coordinates of at least one secondary coordinate along the line feature, the secondary coordinate comprising a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate; estimating theoretical line features using the primary coordinates and the secondary coordinates; and A line angle measurement is calculated between the theoretical line feature and a reference axis.

2. The method of claim 1, wherein the measuring tool is a scanning electron microscope. The method of claim 1 , wherein the line features are lines in a grating structure.

4. The method of claim 1, wherein the line feature comprises a two-dimensional line feature, and wherein the two-dimensional line feature comprises one or more of the following: an elongated post, a cylinder, or a contact hole. The method of claim 4 , wherein the first distance is a predetermined distance in a range between 100 nm and 500 nm. The method of claim 1 , wherein the starting point is greater than 150 nm from a first edge of the field of view, and wherein the first edge of the field of view intersects the line feature. The method according to claim 1 , wherein the theoretical line feature is calculated using three or more coordinate points. The method according to claim 7 , wherein the three or more coordinate points are spaced apart by a predetermined distance.

9. The method of claim 8, wherein the predetermined distance varies between each pair of adjacent points.

10. A method of determining the stitching quality of a lithographic grating structure incorporated in a waveguide, the method comprising the steps of: Measuring the first line angle, the measuring step includes the following operations: (a) Select the field of view of the grating structure; (b) Use measurement tools to identify line features; (c) selecting a starting point along the line feature; (d) measuring a primary coordinate, the primary coordinate comprising a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate; (e) measuring coordinates of at least one secondary coordinate along the line feature, the secondary coordinate comprising a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate; (f) estimating theoretical line features using the primary coordinates and the secondary coordinates; and (g) calculating a line angle measurement between the theoretical line feature and a reference axis; measuring a second line angle, wherein the step of measuring the second line angle comprises operations (a)-(g); calculating a difference between the first line angle and the second line angle to determine the line angle rotation; and The line angle rotation is compared to the design specification line angle measurement. The method of claim 10 , wherein the measuring tool is a scanning electron microscope. The method of claim 10 , wherein the line features are lines in a grating structure.

13. The method of claim 10, wherein the line feature comprises a two-dimensional line feature, and wherein the two-dimensional line feature comprises one or more of the following: an elongated post, a cylinder, or a contact hole. The method of claim 10 , wherein the first distance is a predetermined distance in a range between 100 nm and 500 nm.

15. The method of claim 10, wherein the starting point is greater than 150 nm from a first edge of the field of view, and wherein the first edge of the field of view intersects the line feature. The method of claim 10 , wherein the theoretical line feature is calculated using three or more coordinate points. The method according to claim 16 , wherein the three or more coordinate points are spaced apart by a predetermined distance. The method of claim 17 , wherein the predetermined distance varies between each pair of adjacent points.

19. The method of claim 10, wherein the design specification line angle measurement is 1 / 500 of a degree or less.

20. A method of measuring line angle rotation of a lithographic grating structure incorporated in a waveguide, the method comprising the steps of: positioning a measurement tool to measure a first image exposure in the grating structure; Measuring the first line angle, the measuring step includes the following operations: (a) Select the field of view of the grating structure; (b) using the measurement tool to identify line features; (c) selecting a starting point along the line feature; (d) measuring a primary coordinate, the primary coordinate comprising a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate; (e) measuring coordinates of at least one secondary coordinate along the line feature, the secondary coordinate comprising a second x-coordinate and a second y-coordinate, wherein the second x-coordinate is a second distance from the edge of the field of view to the secondary coordinate; (f) estimating theoretical line features using the primary coordinates and the secondary coordinates; and (g) calculating a line angle measurement between the theoretical line feature and a reference axis; positioning a measurement tool to measure a second image exposure in the grating structure; measuring a second line angle, wherein the step of measuring the second line angle comprises operations (a)-(g); calculating a difference between the first line angle and the second line angle to determine the line angle rotation; comparing the line angle rotation to the design specification line angle measurement; and A splice quality is determined from the difference between the first line angle and the second line angle.

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