A method for measuring etching pattern structure and drilling erosion amount

Abstract

The present invention provides an etching measurement pattern structure and a method for measuring undercutting. The etching measurement pattern structure is used to measure wafer etching amounts. The etching measurement pattern structure includes measurement patterns arranged in a linear array; the spacing between the measurement patterns sequentially forms an arithmetic progression. In the undercutting measurement method of the present invention, the etching measurement pattern structure is provided so that the measurement patterns form an arithmetic progression. Without affecting the overall wafer process, the undercutting value is obtained based on the edge connectivity of the measurement patterns, achieving high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of MEMS technology, in particular to an etching measurement pattern structure and a method for measuring the amount of undercutting. Background Art

[0002] Etching is one of the most important machining processes in MEMS (Micro-electro-mechanical System) manufacturing. It aims to remove material at a specific location and depth within the material being processed. Etching processes can be categorized into wet and dry etching based on the material removal mechanism. Wet etching, also known as wet etching, primarily utilizes chemical etching solutions to etch the material, transferring the photolithography mask pattern to the wafer or material being processed. While wet etching is typically isotropic, it can also exhibit anisotropic etching for crystalline materials, as the etching rate varies with crystal orientation (i.e., exhibits anisotropy). However, this method cannot achieve high aspect ratio etching. While wet etching offers low cost, corrosion control is more difficult, and the etching pattern accuracy is limited. Dry etching, also known as dry etching, primarily removes the material through physical or physicochemical effects. While this process is more expensive, it offers high pattern accuracy and the ability to achieve high aspect ratios, making it more widely used. Dry etching utilizes the resistivity ratio between the mask material and the material being etched, as well as the anisotropic etching characteristics of dry etching, to etch the pattern on the photoresist mask onto the wafer or the material being etched, thereby producing the designed microstructure. In MEMS processing, pattern fidelity (whether the pattern on the photoresist mask can be faithfully transferred) is a key indicator for judging process quality. It directly affects the size and fineness of MEMS microstructures and is the primary indicator of the level of MEMS processing.

[0003] Undercut is the difference between the dimensions of the pattern after etching the material being processed and the dimensions of the pattern on the photoresist mask. The magnitude of this deviation is called the undercut amount or undercut size, which directly affects the pattern fidelity of MEMS fabrication. The fidelity of the designed pattern directly affects the quality of MEMS devices. Controlling the undercut amount in MEMS fabrication is a key technology. Etching undercut primarily originates from two process steps: pattern lithography and pattern etching. Both steps introduce pattern deviation, known as undercut. Pattern undercut in photolithography occurs when, after exposure and development, the final developed pattern on the wafer deviates in size from the pattern on the photoresist mask due to the interplay of light diffraction, the properties of the photoresist and developer during development, and process parameters. This deviation can be positive or negative. Both wet and dry etching processes introduce pattern dimensional deviation, and each exhibits distinct undercutting characteristics. As a purely chemical solution etching process, wet etching lacks directionality and poor controllability, resulting in greater undercutting than the pattern on the photoresist mask. Dry etching is an anisotropic, high-precision process, but it also involves lateral etching beneath the etch mask, causing some lateral undercutting of the wafer or film being processed. Dry etching also causes a small amount of corrosion to the mask material, which can also lead to dimensional deviation in the etched area. Furthermore, dry etching deviation is also related to the etch depth, etch rate, and etch temperature, making high-precision control of etch deviation difficult. In comparison, wet etching has larger deviations, ranging from several microns to more than ten microns, while dry etching has smaller deviations, typically ranging from submicron to several microns. Etching undercutting significantly impacts the precision of MEMS processing, especially fine pattern processing.

[0004] Undercutting is often unavoidable during MEMS etching processes, and high-quality MEMS devices require precise microstructure dimensions. Therefore, addressing undercutting during MEMS etching is a key technical challenge in MEMS manufacturing. Two approaches exist to addressing undercutting: etching process optimization and layout compensation. Etching process optimization is fundamental to improving etching process accuracy, and this requires accurate measurement of the undercutting amount to provide feedback control parameters. Process optimization typically focuses on layout compensation, and the compensation amount is determined by accurately measuring the undercutting amount of the fabricated pattern. Therefore, measuring undercutting during MEMS fabrication is crucial for high-precision MEMS fabrication. Rapid, high-precision measurement of undercutting not only characterizes and evaluates the level and quality of MEMS fabrication, but also guides MEMS fabrication process development and allows process parameter adjustments to achieve higher fidelity of the designed pattern. Furthermore, it allows for precise compensation of the undercutting amount by adjusting the design layout dimensions based on the undercutting amount, resulting in highly precise fabricated pattern structures.

[0005] In MEMS etching processes, conventional methods for measuring undercutting typically use optical microscopy or scanning electron microscopy (SEM) to measure the dimensions of the processed pattern. Due to the small size of the processed pattern, errors in determining the pattern boundaries are significant. Measurement errors are even greater if the processed pattern is a blocky, irregular shape composed of arcs, such as circles and ellipses. Undercutting measurement is labor-intensive, costly, and time-consuming, and results vary widely, making accurate measurements difficult.

[0006] Therefore, how to solve the problems of heavy workload, high cost and long time consumption in existing drilling and erosion measurement has become one of the urgent problems to be solved by those skilled in the art.

[0007] It should be noted that the above introduction to the technical background is merely intended to provide a clear and complete description of the technical solutions of this application and facilitate understanding by those skilled in the art. Simply because these solutions are described in the background technology section of this application, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an etching measurement pattern structure and a method for measuring the amount of undercutting, so as to solve the problems of heavy workload, high cost and long time consumption in the prior art of undercutting measurement.

[0009] To achieve the above-mentioned and other related purposes, the present invention provides an etching measurement pattern structure for measuring the etching undercutting amount of a wafer; the etching measurement pattern structure includes measurement patterns arranged in a linear array; the spacing between each of the measurement patterns sequentially constitutes an arithmetic progression.

[0010] Optionally, the mean of the arithmetic progression is d, d=k+Δ, Δ is the estimated value of undercutting, k is the width of the measured pattern, and the value range of k is 2μm to 10μm; the tolerance of the arithmetic progression is σ, and the value range of σ is 0.01μm to 2μm.

[0011] More optionally, k=pf, where p is a preset parameter and f is the characteristic line width; the value range of p is an integer between 2 and 100.

[0012] Optionally, when the processed pattern of the wafer is a regular pattern, the measurement pattern is the same as the processed pattern of the wafer; when the processed pattern of the wafer is an irregular pattern, the measurement pattern is a rectangle, a square, a circle or an ellipse.

[0013] Optionally, the etching measurement pattern structure is a row of measurement patterns arranged in a linear array.

[0014] Optionally, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, wherein the measurement patterns in one row are arranged alternately with the measurement patterns in the other row; the column spacing between the measurement patterns in each row sequentially forms an arithmetic progression, and the tolerance of the arithmetic progression is 4σ.

[0015] More optionally, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, and the two rows of measurement patterns are aligned vertically; the column spacing between the measurement patterns on each row constitutes an arithmetic progression in sequence; and the spacing between two measurement patterns on each column constitutes an arithmetic progression in sequence.

[0016] Optionally, a positioning mark is provided in a vertical direction of the measurement figure, and a width of the positioning mark is smaller than a width of the measurement figure.

[0017] To achieve the above-mentioned and other related purposes, the present invention further provides a method for measuring the amount of undercutting, which is implemented based on the etching measurement pattern structure. The method comprises the following steps:

[0018] S1: placing the etching measurement pattern structure outside the design pattern area of ​​the wafer;

[0019] S2: processing the design pattern and the etching measurement pattern structure onto the wafer by etching, and obtaining the etching pattern of the wafer after processing;

[0020] S3: Obtaining an undercutting amount based on edge displacement between measurement patterns in the etched pattern.

[0021] Optionally, when measuring positive drilling etching, the etching measurement pattern structure is a row of measurement patterns arranged in a linear array; the intervals between the measurement patterns sequentially form an arithmetic progression.

[0022] Optionally, when measuring negative undercut, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, wherein the measurement patterns in one row are arranged alternately with the measurement patterns in the other row; the spacing between the measurement patterns in each row sequentially constitutes an arithmetic progression, and the tolerance of the arithmetic progression is 4σ.

[0023] Optionally, when measuring drilling in different directions, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, and the two rows of measurement patterns are aligned vertically; the column spacing between the measurement patterns on each row constitutes an arithmetic progression in sequence; and the spacing between two measurement patterns on each column constitutes an arithmetic progression in sequence.

[0024] As described above, the etching measurement pattern structure and the method for measuring the amount of undercutting of the present invention have the following beneficial effects:

[0025] The spacing between the measurement patterns in the etching measurement pattern structure of the present invention sequentially forms an arithmetic progression. After the etching measurement pattern structure is etched on the wafer together with the design pattern of the wafer, the drilling amount can be directly obtained based on the edge displacement between the measurement patterns in the etched pattern. The measurement is simple, efficient, highly accurate and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram showing the principle of a first implementation of the etching measurement pattern structure of the present invention.

[0027] Figure 2 Schematic diagram showing the numerical substitution of the first implementation of the etching measurement pattern structure of the present invention.

[0028] Figure 3 A schematic diagram showing a structure after wafer processing in which the first implementation of the etching measurement pattern structure of the present invention is applied.

[0029] Figure 4 Another schematic diagram showing the first implementation of the etching measurement pattern structure of the present invention applied to a structure after wafer processing.

[0030] Figure 5 It is a schematic diagram showing the principle of a second implementation of the etching measurement pattern structure of the present invention.

[0031] Figure 6 A schematic diagram showing numerical substitution of a second implementation of the etching measurement pattern structure of the present invention is shown.

[0032] Figure 7 A schematic diagram showing a structure after wafer processing in which the second implementation of the etching measurement pattern structure of the present invention is applied.

[0033] Figure 8 Another schematic diagram showing the second implementation of the etching measurement pattern structure of the present invention applied to a structure after wafer processing.

[0034] Figure 9 Another schematic diagram showing the second implementation of the etching measurement pattern structure of the present invention applied to a structure after wafer processing.

[0035] Figure 10 It is a schematic diagram showing the principle of a third implementation of the etching measurement pattern structure of the present invention.

[0036] Figure 11 It is a schematic diagram showing numerical substitution of a third implementation of the etching measurement pattern structure of the present invention.

[0037] Figure 12A schematic diagram showing a structure after wafer processing in which the third implementation of the etching measurement pattern structure of the present invention is applied.

[0038] Figure 13 Another schematic diagram showing the third implementation of the etching measurement pattern structure of the present invention applied to a structure after wafer processing.

[0039] Component number description

[0040] 11 Measurement graphics

[0041] 12 Positioning Marks

[0042] Steps S1 to S3 DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] See also Figures 1 to 13 It should be noted that the diagrams provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0045] Example 1

[0046] The present embodiment provides an etching measurement graphic structure for measuring the etching drilling amount of a wafer, wherein the etching measurement graphic structure includes measurement graphics 11 arranged in a linear array (linear array: an array formed by a straight line arrangement); the spacing between each of the measurement graphics 11 constitutes an arithmetic progression. As an example, when the processed graphic of the wafer is a regular graphic (regular graphic: a graphic that can be named, such as a rectangle, circle, triangle, parallelogram, regular polygon, etc.), the measurement graphic 11 is the same as the processed graphic (device graphic) of the wafer; when the processed graphic of the wafer is an irregular graphic (irregular graphic: a graphic that cannot be defined or named, a graphic that cannot be named), the measurement graphic 11 is a rectangle, square, circle or ellipse. The measurement graphic 11 can also be other regular graphics, which are not limited here.

[0047] Specifically, the mean of the arithmetic progression is d (e.g. Figure 1As shown in the figure, d is the distance between the axial center line of the measurement figure 11 with the serial number 0 located at the center position and the axial center line of the first measurement figure 11), d=k+Δ, Δ is the estimated value of the undercut, k is the width of the measurement figure 11 (the maximum length of the horizontal cross section of the measurement figure 11), and the value range of k is 2μm to 10μm; the tolerance of the arithmetic progression is σ, and the value range of σ is 0.01μm to 2μm. The value of σ is determined according to the measurement accuracy of the undercut amount.

[0048] Specifically, k=pf, p is a preset parameter, and f is the characteristic line width; the value range of p is an integer between 2 and 100 (including 2 and 100). As an example, the value range of p is an integer between 5 and 20. It should be noted that because f (the characteristic line width of photolithography in etching processing) is usually small, it is multiplied by a large coefficient (p) to facilitate processing and measurement. In this embodiment, the different spacings between adjacent measurement figures 11 leave space for etching drilling. After the wafer is processed, the connection between the left and right edges of adjacent measurement figures 11 is observed. Through the set value of the spacing, the size of the drilling can be determined intuitively and quickly.

[0049] As a first implementation of this embodiment, the etching measurement pattern structure is a row of measurement patterns 11 arranged in a linear array. Figure 1 As shown, as an example, the measurement pattern 11 is a rectangle; the etching measurement pattern structure is a row of measurement patterns 11 arranged in a linear array, and each measurement pattern 11 is arranged along the width. Figure 1 As shown, each of the measurement patterns 11 is centered on one of the measurement patterns 11 ( Figure 1 The measurement figures 11 are arranged in an arithmetic progression along the width of the measurement figures 11 (the spacing between the axial centerlines of the measurement figures 11 forms an arithmetic progression, or the distances between the closest edges of the measurement figures 11 form an arithmetic progression). It should be noted that the actual position of the measurement figure 11 at the center is not limited. That is, the measurement figure 11 with the axial centerline numbered 0 can be any measurement figure 11, as long as the spacing between two adjacent measurement figures 11 forms an arithmetic progression.

[0050] Specifically, as an example, a positioning mark 12 is provided in the vertical direction of the measurement figure 11, and the positioning mark 12 is used to indicate the arrangement relationship between the corresponding measurement figure and the measurement figure at the center position (i.e., labeled 0) (identify the serial number of the corresponding measurement figure), and the serial numbers of adjacent measurement figures 11 differ by 1, such as -2, -1, 0, 1, 2, etc. in the figure. The serial number with a negative sign indicates that the corresponding measurement figure 11 is located to the left of the measurement figure 11 labeled 0, and the serial number with a positive sign indicates that the corresponding measurement figure 11 is located to the right of the measurement figure 11 labeled 0. As an example, the positioning mark 12 includes a positioning serial number and / or a positioning figure; as an example, the width of the positioning figure is smaller than the width of the measurement figure 11, and then when the positioning mark 12 is etched on the wafer together with the measurement figure 11, the etching error will not affect the reading of the positioning mark 12, and the serial number of each measurement figure 11 can be clearly obtained through the positioning mark 12, and the drilling amount can be obtained conveniently and quickly. Figure 1 As shown, a rectangular positioning pattern is provided above each of the measurement patterns 11 , and the shape and size of the positioning pattern can be selected according to actual needs. In this embodiment, each positioning pattern is provided directly above the corresponding measurement pattern 11 .

[0051] As an example, Figure 1 The etching measurement pattern structure is shown. The distance between the axial centerlines of two adjacent measurement patterns 11 is D, where D = d + MΔ, where M is the serial number of the measurement pattern 11. As an example, the etching measurement pattern structure of this embodiment is applicable when Δ + Mσ > 0. When Δ + Mσ > 0, the etching undercut is positive, and the wafer pattern after processing is larger than the designed pattern. In this case, the etching measurement pattern structure is a positive pattern, i.e., the photolithographic etched area (the measurement pattern 11), while the spacing between the measurement patterns is a negative pattern, i.e., the non-exposed area (the portion between two adjacent measurement patterns 11). This leaves space for positive undercutting of the measurement pattern, and the remaining width of the spacing after etching determines the extent of the etching undercut. When Δ + Mσ < 0, the etching undercut is negative, and the processed pattern is smaller than the designed pattern. In this case, negative undercut values ​​can be measured by designing the spacing between adjacent measurement patterns as a bright pattern. However, given the exposure accuracy of photolithography and the inability to determine the surface after etching, this solution is not suitable for measuring negative undercutting.

[0052] As an example, the estimated value of undercutting Δ is 0.5 μm, the width k of the measurement pattern 11 is set to 5 μm, and the undercutting measurement accuracy σ is set to 0.2 μm, then d = k + Δ = 5 μm + 0.5 μm = 5.5 μm. Figure 2The etching measurement pattern structure of this embodiment is shown. The closest distances between adjacent measurement patterns 11 (the distances where the edges just touch) form an arithmetic progression in sequence. The tolerance is σ, the mean term is Δ, and the general term is Δ+Mσ. As an example, when measuring the etching undercut of a wafer, first Figure 2 The etching measurement pattern structure is placed outside the design pattern area of ​​the processed wafer, and then a series of photolithography etching processes are performed on the wafer, and finally the following is obtained: Figure 3 The etched measurement pattern structure after processing is shown. Figure 3 It can be intuitively calculated that the size of the undercut is 0.7 μm, that is, the edge of the measurement pattern 11 with serial number 2 is exactly connected to the edge of the measurement pattern 11 with serial number 1 (the displacement deviation of the two measurement patterns 11 with serial number 2 and serial number 1 is 0.7 μm). Figures 1 to 13 These are all schematic diagrams. In an actual etching measurement pattern structure, the spacing between the measurement patterns 11 is arranged according to an arithmetic progression. Figure 3 In the figure, at a spacing of 0.5 μm, the boundary between two adjacent measurement patterns 11 cannot be distinguished; at a spacing of 0.9 μm, the edges of adjacent measurement patterns 11 are clearly separated, so it is determined that the etching depth in the x direction is 0.7 μm. Figure 4 As shown in FIG. 1 , the connection state cannot be clearly found, and the undercut size in the x direction is between 0.5 μm and 0.7 μm. To obtain a more accurate undercut value, the value of σ can be appropriately reduced and the number of measurement patterns 11 can be increased.

[0053] As a second implementation of this embodiment, the difference from the first implementation is that the etching measurement pattern structure is composed of two rows of measurement patterns 11 arranged in a linear array, wherein the measurement patterns 11 in one row are arranged alternately with the measurement patterns 11 in the other row; the column spacing between the measurement patterns 11 in each row sequentially forms an arithmetic progression, and the tolerance of the arithmetic progression is 4σ. As an example, Figure 5 As shown, the spacing between the axial center lines of the adjacent measurement patterns 11 in the first row is 2d+(4M+1)σ; in this embodiment, d is the spacing between the axial center lines of the measurement pattern 11 with the serial number 0 in the first row and the second row of the etching measurement pattern structure, d=k+Δ; 2d is the mean of the arithmetic progression, and M is the serial number of the left side of the adjacent measurement pattern 11 in the same row (for example Figure 5 The spacing between the axial center lines of the measurement figures numbered 1 and 2 in the first row is 2d+(4M+1)σ=2d+(4*1+1)σ=2d+5σ, where M is 1 because the measurement figure on the left of the measurement figures numbered 1 and 2 is numbered 1); k is the measurement figure width; Δ is the estimated value of the drilling size. Figure 5In the example, the spacing between the axial center lines of adjacent measurement patterns 11 in the second row is 2d+(4M-1)σ; d=k+Δ; M is the serial number of the first row of measurement patterns corresponding to the spacing segment between adjacent measurement patterns 11 in the second row (e.g. Figure 5 The spacing between the axial center lines of the measurement figures numbered 0 and 1 in the second row is 2d+(4M-1)σ=2d+(4*1-1)σ=2d+3σ, where M is 1 because the measurement figure above the measurement figures numbered 0 and 1 in the second row is numbered 1); k is the measurement figure width; Δ is the estimated value of the drilling size.

[0054] As an example of the second implementation of this embodiment, Figure 6 As shown in the figure, the drilling estimation value Δ is set to 0.5μm, the drilling measurement accuracy σ is set to 0.1μm, M is set to 5, and the width k of the measurement pattern is set to 2μm. After the wafer undergoes a series of photolithography and etching, the etching measurement pattern structure is as follows Figure 7 As shown in the figure (or through the microscope, use the straight line function in the microscope field of view) to find the serial numbers where the edges of the measurement figures meet. Figure 7 In the figure, the edge of the measurement pattern 11 with the serial number -1 in the first row is exactly connected to the edge of the measurement pattern with the serial number -1 in the second row, so the size of the drilling is 0.3μm; at a spacing of 0.2μm, the edges of the measurement patterns are staggered, and at a spacing of 0.4μm, the edges of the measurement patterns are clearly separated, so it is determined that the drilling amount in the x direction (horizontal direction) is 0.3μm. If the measured structure after processing is as follows Figure 8 As shown in the figure, it is not possible to clearly find the state where the edges are connected or on a straight line. The undercut amount in the x direction is between 0.3um and 0.4um. If you want to get a more accurate undercut value, you can appropriately reduce the value of σ and increase the number of measurement patterns. If the measured structure after processing is as follows Figure 9 In the state shown, the undercut is negative, with a magnitude of 0.2μm. In the x-direction, at an edge spacing of -0.2μm, the edges of the patterns are exactly connected and on the same straight line. At a spacing of -0.3μm, the edges of the measured patterns are staggered. At a spacing of -0.1μm, the edges of adjacent patterns are separated. Therefore, it can be determined that the etching undercut in the x-direction is -0.2μm. It should be noted that the etching measurement pattern structure in the second implementation of this embodiment is arranged one above the other, which does not interfere with each other during etching. This can be used to measure the undercut of patterns with smaller undercuts, and can simultaneously measure positive and negative etching undercut values ​​without distinguishing between positive and negative plates. After etching, the undercut size is determined by observing the edge positions of the adjacent measurement patterns above, below, left, and right.

[0055] As the third implementation of this embodiment, the difference from the first implementation is that: the etching measurement graphic structure is composed of two rows of measurement graphics 11 arranged in a linear array, and the two rows of measurement graphics 11 are aligned vertically; the column spacing between the measurement graphics 11 on each row constitutes an arithmetic progression in sequence; the spacing between the two measurement graphics 11 on each column constitutes an arithmetic progression in sequence. As an example, the measurement graphics 11 in this embodiment are square. The etching measurement graphic structure of the third implementation method of this embodiment adjusts the arrangement of the measurement graphics to simultaneously measure the etching drilling in the x and y directions in the smallest space. As an example, Figure 10 As shown, σ is the tolerance of the arithmetic progression, with a value range of 0.01 μm to 2 μm, determined based on the required undercut measurement accuracy. d is the spacing of the measurement pattern 11 from the center position, set as the mean of the arithmetic progression, and is equal to the width k + Δ of the etched measurement pattern structure. Δ is the estimated undercut value, ranging from 1 μm to 10 μm, and is determined based on the undercut measurement range. In this embodiment, the arrangement rule of the measurement patterns 11 is as follows: there are two rows of measurement patterns 11 in the x-direction. Each row of linear measurement patterns is arranged horizontally. The edge spacing between two adjacent measurement patterns 11 in each row is set as an arithmetic progression with Δ as the mean and σ as the tolerance. The edge spacing between two adjacent measurement patterns 11 reserves space for undercut in the x-direction. After processing, the extent of undercut in the x-direction can be determined by the edge alignment and connection of the measurement patterns 11. In the Y direction (on each column), every two measurement patterns 11 are aligned, and the edge spacing (the spacing between the upper and lower measurement patterns 11 on each column) is set to an arithmetic progression with Δ as the mean and σ as the difference (e.g. Figure 10 The distance between the two upper and lower measurement patterns 11 with serial numbers of -2, -1, 0, and 1 forms an arithmetic progression in sequence); the edge distance between two adjacent measurement patterns is the reserved space for drilling in the y direction. After processing, the size of the drilling in the y direction can be determined by measuring the edge alignment and connection of the measurement patterns. As an example, Figure 10 and Figure 11 As shown, only the data of the arithmetic progression formed by the column spacing is marked in the figure, and the spacing between the two measurement patterns 11 on each column is not marked.

[0056] As an example of the third implementation of this embodiment, Figure 11 As shown in the figure, the estimated value of the erosion Δ is set to 0.5μm, the erosion measurement accuracy σ is set to 0.1μm, the width k of the measurement pattern is set to 2μm, the length h is set to 5μm, m is set to 5, and d is 2.5μm. The wafer is an etched measurement pattern structure after a series of photolithography and etching processes, as shown in the figure. Figure 12As shown, it can be observed that the edge of the measurement figure with serial number -1 is connected to the edge of the measurement figure with serial number -2, and the size of the undercut in the x-direction is 0.3 μm; the upper and lower edges of the measurement figure with serial number 4 are connected, and the size of the undercut in the y-direction is 0.9 μm. Figure 12 In the figure, at a spacing of 0.2μm, the measurement pattern is etched into a piece; at a spacing of 0.4μm, the edges of adjacent measurement patterns are clearly separated, so it can be determined that the etching depth in the x-direction is 0.3μm. Similarly, in the y-direction, the edges of the measurement pattern numbered 3 are etched together into a piece, and the edges of the measurement pattern numbered 5 are clearly separated, so it can be determined that the etching depth in the y-direction is 0.9μm. If the structure of the etched measurement pattern after processing is as follows Figure 13 As shown, the connection state cannot be clearly found. The undercut size in the x-direction is between 0.3μm and 0.4μm, and the undercut size in the y-direction is between 0.9μm and 1μm. To obtain a more accurate undercut value, the value of σ can be appropriately reduced and the number of measurement patterns can be increased.

[0057] Specifically, the substrate material of the wafer includes semiconductor material, glass, ceramic or metal. The substrate material of the wafer can be any common material in MEMS manufacturing and is not limited here; the wafer size of the wafer is not limited and is selected according to actual needs.

[0058] The spacing between the measurement patterns in the etching measurement pattern structure of the present invention sequentially forms an arithmetic progression. After the etching measurement pattern structure is etched on the wafer together with the design pattern of the wafer, the undercut amount can be directly obtained based on the edge displacement between the measurement patterns in the etched pattern, and the measurement is simple and efficient.

[0059] Example 2

[0060] This embodiment provides a method for measuring undercutting, which is implemented based on the etching measurement pattern structure described in the first embodiment. The method is characterized in that the method includes the following steps:

[0061] S1: placing the etching measurement pattern structure outside the design pattern area of ​​the wafer.

[0062] Specifically, the etching measurement pattern structure is added to the design pattern of the wafer, and the etching measurement pattern structure has no overlap with the design pattern of the wafer, so that the measurement pattern after etching can be clearly seen.

[0063] S2: processing the design pattern and the etching measurement pattern structure onto the wafer by etching, and obtaining the etching pattern of the wafer after processing.

[0064] Specifically, the design pattern containing the etching measurement pattern structure is etched onto the wafer by a photolithography machine, and then the etching pattern of the wafer after processing is obtained. As an example, when measuring positive drilling, the etching measurement pattern structure is a row of measurement patterns 11 arranged in a linear array; the spacing between the measurement patterns 11 constitutes an arithmetic progression in sequence. It should be noted that when the etching measurement pattern structure in the present invention is a row of linear arrays, negative drilling or drilling in different directions can also be measured, which can be selected according to the measurement accuracy requirements. As an example, when measuring negative drilling, the etching measurement pattern structure is composed of two rows of measurement patterns 11 arranged in a linear array, wherein the measurement patterns 11 in one row are staggered with the measurement patterns 11 in the other row; the spacing between the measurement patterns 11 in each row constitutes an arithmetic progression in sequence, and the tolerance of the arithmetic progression is 4σ. As an example, when measuring undercutting in different directions, the etching measurement pattern structure comprises two rows of linear arrayed measurement patterns 11, aligned vertically. The spacing between the measurement patterns 11 in each row forms an arithmetic progression, and the spacing between two measurement patterns 11 in each column forms an arithmetic progression. It should be noted that the etching measurement pattern structure of the present invention, when arranged as a two-row linear array, can also measure positive undercutting, negative undercutting, or undercutting in different directions, and the method can be selected based on the required measurement accuracy.

[0065] S3: Obtaining an undercutting amount based on edge displacement between measurement patterns in the etched pattern.

[0066] Specifically, the undercutting amount is determined by observing the serial numbers of two measurement patterns where the edges of the measurement patterns meet in the etched pattern. For example, the serial numbers of the edges of the measurement patterns 11 where the edges meet can be found through microscopic observation or by using a line function within the microscope's field of view. The magnitude of the movement between the two measurement patterns 11, i.e., the undercutting amount, can be determined from the serial numbers.

[0067] The etching measurement pattern structure used in the method for measuring the undercutting amount of the present invention has the advantages of being simple and intuitive, convenient and fast, highly accurate and low-cost when measuring the undercutting amount, and the measurement patterns are arranged in an arithmetic progression.

[0068] In summary, the present invention provides an etching measurement pattern structure and a method for measuring undercutting. The etching measurement pattern structure is used to measure wafer etching amounts. The etching measurement pattern structure includes measurement patterns arranged in a linear array; the spacing between the measurement patterns sequentially forms an arithmetic progression. In the undercutting measurement method of the present invention, by configuring the etching measurement pattern structure, the measurement patterns form an arithmetic progression. Undercutting values ​​are obtained based on the edge connectivity of the measurement patterns without affecting the overall wafer processing, resulting in high measurement accuracy. Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial application value.

[0069] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for measuring undercutting, characterized in that: The measuring method comprises the following steps: S1: Placing an etching measurement pattern structure outside the design pattern area of ​​the wafer; the etching measurement pattern structure includes measurement patterns arranged in a linear array; the spacing between each of the measurement patterns sequentially forms an arithmetic progression; S2: processing the design pattern and the etching measurement pattern structure onto the wafer by etching, and obtaining the etching pattern of the wafer after processing; S3: Based on the edge displacement between the measurement patterns in the etched pattern, the undercut amount is obtained; by observing the serial numbers of two measurement patterns whose edges are connected in the etched pattern, the undercut amount is obtained according to the serial numbers of the two measurement patterns, and the undercut amount is the size of the displacement between the two measurement patterns.

2. The method for measuring undercutting according to claim 1, wherein: When measuring positive drilling, the etching measurement pattern structure is a row of measurement patterns arranged in a linear array; the intervals between the measurement patterns sequentially form an arithmetic progression.

3. The method for measuring undercutting according to claim 1, wherein: When measuring negative undercut, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, wherein the measurement patterns in one row are arranged alternately with the measurement patterns in the other row; the spacing between the measurement patterns in each row sequentially forms an arithmetic progression, and the tolerance of the arithmetic progression is 4σ.

4. The method for measuring undercutting according to claim 1, wherein: When measuring drilling in different directions, the etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, and the two rows of measurement patterns are aligned vertically; the column spacing between the measurement patterns on each row sequentially forms an arithmetic progression; and the spacing between two measurement patterns on each column sequentially forms an arithmetic progression.

5. An etching measurement pattern structure, implemented based on the undercutting amount measurement method according to any one of claims 1 to 4, characterized in that: The etching measurement pattern structure is used to measure the wafer etching undercutting amount.

6. The etching measurement pattern structure according to claim 5, characterized in that: The mean of the arithmetic progression is d, d=k+Δ, Δ is the estimated value of undercutting, k is the width of the measured pattern, and the value range of k is 2μm to 10μm; the tolerance of the arithmetic progression is σ, and the value range of σ is 0.01μm to 2μm.

7. The etching measurement pattern structure according to claim 6, characterized in that: k=pf, p is a preset parameter, f is the characteristic line width; the value range of p is an integer between 2 and 100.

8. The etching measurement pattern structure according to claim 5, characterized in that: When the processed pattern of the wafer is a regular pattern, the measurement pattern is the same as the processed pattern of the wafer; when the processed pattern of the wafer is an irregular pattern, the measurement pattern is a rectangle, a square, a circle or an ellipse.

9. The etching measurement pattern structure according to any one of claims 5 to 8, characterized in that: The etching measurement pattern structure is a measurement pattern arranged in a row of linear arrays.

10. The etching measurement pattern structure according to any one of claims 5 to 8, characterized in that: The etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, wherein the measurement patterns in one row are arranged alternately with the measurement patterns in the other row; the column spacing between the measurement patterns in each row sequentially forms an arithmetic progression, and the tolerance of the arithmetic progression is 4σ.

11. The etching measurement pattern structure according to any one of claims 5 to 8, characterized in that: The etching measurement pattern structure is composed of two rows of measurement patterns arranged in a linear array, and the two rows of measurement patterns are aligned vertically; the column spacing between the measurement patterns on each row sequentially forms an arithmetic progression; and the spacing between two measurement patterns on each column sequentially forms an arithmetic progression.

12. The etching measurement pattern structure according to any one of claims 5 to 8, characterized in that: A positioning mark is provided in a vertical direction of the measurement pattern, and a width of the positioning mark is smaller than a width of the measurement pattern.

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