A method and system for calibrating a semiconductor lithography apparatus

Abstract

The application relates to the technical field of lithography machine control, in particular to a calibration method and a calibration system of a semiconductor lithography machine. The calibration method comprises the following steps: projecting a grating calibration pattern on the back of a flexible substrate, and collecting a back surface image of the substrate; determining the depth values of each pixel point on the back surface image of the substrate through a phase unwrapping algorithm; acquiring a front surface image of the flexible substrate; correcting the front surface image of the substrate according to the three-dimensional coordinates of each pixel point on the front surface image, and obtaining a virtual front surface image; aligning the virtual front surface image with a mask image; and transferring the mask image to the flexible substrate after alignment. The first alignment mark area of the wrinkle deformation is stretched and flattened, so that the alignment algorithm of the lithography machine can align the first alignment mark on the front surface image of the substrate with the second alignment mark on the mask image, and the multi-layer circuit of the flexible substrate is prevented from being dislocated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithography machine control, in particular to a calibration method and system for a semiconductor lithography machine. BACKGROUND

[0002] In the lithography technology, the alignment mark is a key element for realizing the alignment and positioning between the lithography layers. The lithography is a method for transferring a pattern on a photosensitive material, which projects the pattern onto the photosensitive material through the action of a light source and a light mask (mask), and transfers the pattern to the surface of a substrate or chip through chemical or physical processing.

[0003] When performing the lithography transfer of multiple layers of patterns on a flexible substrate, it is necessary to identify the alignment mark and transfer according to the position of the alignment mark.

[0004] In a semiconductor lithography machine, a substrate alignment mark is arranged on a substrate, and a mask alignment mark is arranged on a mask. The semiconductor lithography machine determines the position of mask pattern transfer by aligning the substrate alignment mark and the mask alignment mark.

[0005] Unlike the material of a silicon wafer substrate, the flexible substrate is a polymer material. The flexible substrate will deform after multiple lithography, etching and ion implantation processes, mainly in the form of local wrinkles and local two-dimensional deformation. Local wrinkles refer to the protrusion or depression of the flexible substrate in the height direction perpendicular to the substrate plane, and local two-dimensional deformation refers to the stretching or shrinkage of the flexible substrate in the substrate plane.

[0006] If the local wrinkles or local two-dimensional deformation are located on the alignment mark, the existing alignment algorithm will not be able to align the mask alignment mark and the substrate alignment mark, and thus the next level of mask pattern lithography cannot be performed.

[0007] In order to accurately identify the alignment mark on the flexible substrate, the present application provides a calibration method and system for a semiconductor lithography machine. SUMMARY

[0008] To overcome the problems in the related art, the first aspect of the present application provides a calibration method for a semiconductor lithography machine, comprising the following steps:

[0009] Projecting a grating calibration pattern on the back of the flexible substrate to obtain a substrate back image;

[0010] Determining the depth value of each pixel point on the substrate back image by a phase unwrapping algorithm;

[0011] obtaining a substrate front image of a front side of the flexible substrate, the front side of the substrate being provided with a first alignment mark, the substrate front image comprising a region image of M first alignment marks, M being an integer greater than or equal to 1, the first alignment mark being used for mask image alignment;

[0012] correcting the substrate front image according to three-dimensional coordinates of each pixel point on the substrate front image to obtain a virtual front image;

[0013] aligning the virtual front image and the mask image;

[0014] transferring the mask image to the flexible substrate after alignment.

[0015] In an embodiment, the depth value of each pixel point on the substrate back image is determined by a phase unwrapping algorithm, specifically comprising:

[0016] obtaining light intensity of each pixel point at three different phase shift steps;

[0017] determining the wrapped phase value of each pixel point according to the light intensity of each pixel point at three different phase shift steps;

[0018] unwrapping the wrapped phase value of each pixel point to obtain the absolute phase value of each pixel point;

[0019] determining the depth value of each pixel point according to the absolute phase value of each pixel point.

[0020] In an embodiment, the substrate front image of the front side of the flexible substrate is obtained, specifically comprising:

[0021] photographing the front side of the flexible substrate to obtain the substrate front image;

[0022] obtaining the depth value of each pixel point of the substrate back image;

[0023] encoding the depth value of each pixel point of the substrate back image to the corresponding pixel point of the substrate front image to obtain the three-dimensional coordinates of the pixel point of the substrate front image.

[0024] In an embodiment, the substrate front image is corrected according to the three-dimensional coordinates of each pixel point on the substrate front image to obtain a virtual front image, specifically comprising:

[0025] identifying the deformed first alignment mark on the substrate front image by an edge contour detection algorithm;

[0026] performing image segmentation on the region where the deformed first alignment mark is located to obtain a deformed region image;

[0027] Obtaining the three-dimensional coordinates of each pixel point of the corresponding area of ​​the deformed area image on the substrate front image;

[0028] Taking the center of the deformed region image as the origin, stretching the image in all directions to obtain a virtual region image;

[0029] The virtual area image is spliced ​​onto the substrate front image to obtain a virtual front image.

[0030] In one embodiment, the grating calibration pattern is a structured light with N-step phase-shifted stripes, where N is an integer greater than or equal to 1.

[0031] In one embodiment, the phase shift fringe formula is

[0032]

[0033] in, is the background light intensity; To modulate the light intensity; is the initial phase value; For the The phase shift value of the step, , is the number of phase shift steps; is the pixel index number; Pixel The depth value of .

[0034] In one embodiment, determining the wrapped phase value of each pixel point based on the light intensity of each pixel point at three different phase shift steps specifically includes:

[0035] The wrapped phase value of each pixel is solved by the light intensity and phase solution formula of each pixel at three different phases; the phase solution formula is:

[0036]

[0037] in, Pixel The wrapped phase value of is the light intensity of the first phase, is the light intensity of the second phase, is the light intensity of the third phase.

[0038] A second aspect of the present application provides a calibration system for semiconductor lithography equipment, comprising a structured light unit, an image acquisition unit, and a calculation unit;

[0039] The structured light unit is used to project a grating calibration pattern toward the back surface of the flexible substrate;

[0040] The image acquisition unit acquires a back surface image of the substrate with a grating calibration pattern and a front surface image of the substrate with a first alignment mark;

[0041] The calculation unit is configured to execute the calibration method of the semiconductor lithography device according to the first aspect of the present application.

[0042] The technical solution provided by the present application can include the following beneficial effects:

[0043] In the present application, the depth value of each pixel point scale of the flexible substrate is acquired through the grating calibration pattern, and the depth value of the wrinkle deformation is greater than 0. The three-dimensional coordinates of each pixel point of the front surface image of the substrate are determined through the depth value of each pixel point of the back surface image of the substrate. The first alignment mark region of the wrinkle deformation is stretched and flattened, so that the alignment algorithm of the lithography device can align the first alignment mark on the front surface image of the substrate and the second alignment mark on the mask image, and ensure that the multi-layer circuit of the flexible substrate does not dislocate.

[0044] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0045] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which the exemplary embodiments of the present application are shown.

[0046] Figure 1 is a flowchart of the calibration method of the semiconductor lithography device according to the embodiment of the present application. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present application will be described herein below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0048] The terms used in the present application are merely for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein means and includes any or all possible combinations of one or more associated listed items.

[0049] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0050] Example 1

[0051] In a semiconductor lithography device, a substrate alignment mark is provided on the substrate, and a mask alignment mark is provided on the mask. The semiconductor lithography device determines the position of mask pattern transfer by aligning the substrate alignment mark and the mask alignment mark.

[0052] Unlike silicon wafer substrates, flexible substrates are made of polymer. They can deform during the multiple photolithography, etching, and ion implantation processes, primarily manifesting as localized wrinkling and two-dimensional deformation. Localized wrinkling refers to protrusions or depressions in the flexible substrate perpendicular to the substrate plane, while localized two-dimensional deformation refers to stretching or shrinking of the flexible substrate in the plane of the substrate.

[0053] If a local wrinkle or a local two-dimensional deformation happens to be located on the alignment mark, the existing alignment algorithm will be unable to align the mask alignment mark and the substrate alignment mark, and the next level of mask pattern lithography will not be possible.

[0054] In order to accurately identify a deformed substrate alignment mark, an embodiment of the present application provides a calibration method for a semiconductor lithography device, which can accurately extract edge feature points of the substrate alignment mark.

[0055] The calibration method of the semiconductor lithography equipment of the embodiment of the present application is implemented based on a calibration system, which is provided with a structured light unit, an image acquisition unit and a calculation unit. The structured light unit is capable of projecting a grating calibration pattern onto the back of the flexible substrate. The image acquisition unit acquires an image of the back of the substrate with the grating calibration pattern and an image of the front of the substrate with the first alignment mark. The calculation unit is used to perform the following steps: Figure 1 A calibration method for a semiconductor lithography apparatus is shown.

[0056] Figure 1 It is a flow chart of a calibration method for semiconductor lithography equipment shown in an embodiment of the present application.

[0057] like Figure 1 As shown, the technical solution of the present application provides a calibration method for semiconductor lithography equipment, comprising the following steps:

[0058] S1, projecting a grating calibration pattern on the back of the flexible substrate, and collecting a back image of the substrate;

[0059] Since the front of the flexible substrate is coated with photoresist, in order to prevent the grating calibration pattern from being irradiated to the photoresist and causing photoresist exposure, the grating calibration pattern is projected onto the back of the flexible substrate in the embodiment of the application, and the depth information of the front of the flexible substrate is obtained by backstepping the depth information of each pixel point on the back.

[0060] In the embodiment of the application, the grating calibration pattern is structured light of step phase shift fringe. For example, the phase shift fringe formula is

[0061]

[0062] wherein, is the background light intensity; is the modulation light intensity; is the initial phase value; is the phase shift value of the first step, is the phase shift value of the second step, is the phase shift value of the third step, is the number of phase shifts; is the pixel point index number; is the depth value of the pixel point. The three-step phase shift method is used to calculate the light intensity of each phase shift step

[0063] . When ,

[0064]

[0065] When ,

[0066]

[0067] When ,

[0068]

[0069]

[0070] Substitute the pixel point index number to obtain the light intensity of each pixel point under three different phase shift steps .

[0071] S2, determining the depth value of each pixel point on the back image of the substrate by a phase unwrapping algorithm;

[0072] Specifically, step S2 includes the following steps: ​​

[0073] S201, obtaining light intensity of each pixel point at three different phase shift steps;

[0074] S202, determining a wrapped phase value of each pixel point according to the light intensity of each pixel point at the three different phase shift steps;

[0075] After the substrate back image is obtained, the light intensity of each pixel point of the substrate back image at three phases is read respectively .

[0076] The light intensity of the three phases is substituted into a phase solving formula to obtain the phase of the pixel point. Exemplarily, the phase solving formula of the three-phase step shift method is as follows:

[0077]

[0078] wherein, is a wrapped phase value of the pixel point, is the light intensity of the first phase, is the light intensity of the second phase, is the light intensity of the third phase.

[0079] After the wrapped phase of each pixel point is obtained, the absolute phase value of each pixel point is determined through the phase unwrapping algorithm of step S2.

[0080] S203, unwrapping the wrapped phase value of each pixel point to obtain the absolute phase value of each pixel point;

[0081] S204, determining the depth value of each pixel point according to the absolute phase value of each pixel point.

[0082] In the embodiment of the present application, after the depth value of each pixel point of the substrate back image is determined, the same specification image acquisition and pretreatment are performed on the front surface of the flexible substrate. The same specification image acquisition makes the pixel point number and resolution of the substrate front surface image and the substrate back surface consistent. The pretreatment step is to adjust the spatial position of the substrate front surface image and the substrate back surface image, so that the substrate front surface image and the substrate back surface image can be correspondingly overlapped.

[0083] S3, obtaining a substrate front surface image of the front surface of the flexible substrate;

[0084] It can be understood that the pixel width, pixel length and resolution of the substrate back image and the substrate front image are consistent.

[0085] ​Specifically, a first alignment mark is arranged on the front surface of the substrate, and the front surface image of the substrate includes an area image of M first alignment marks, where M is an integer greater than or equal to 1. It can be understood that the first alignment mark is used for mask pattern alignment.

[0086] Further, S3 specifically includes the following steps:

[0087] S301, capturing the front surface of the flexible substrate to obtain the front surface image of the substrate;

[0088] S302, obtaining the depth value of each pixel point of the back surface image of the substrate;

[0089] S303, encoding the depth value of each pixel point of the back surface image of the substrate to the corresponding pixel point of the front surface image of the substrate to obtain the three-dimensional coordinates of the pixel point of the front surface image of the substrate as .

[0090] In the embodiments of the present application, since the pixel points of the front surface image of the substrate and the back surface image of the substrate are one-to-one corresponding, when the depth value of each pixel point of the back surface image of the substrate is known, the height of each pixel point of the front surface image of the substrate can be obtained.

[0091] In step S303, the calculation formula of the height of each pixel point of the front surface image of the substrate is:

[0092]

[0093] wherein, is the height of each pixel point of the front surface image of the substrate, is the depth value of each pixel point of the back surface image of the substrate, represents a function of converting the depth value of the pixel point into the height value in the same coordinate system. Exemplarily, wherein, is the distance from the pixel point to the reference plane.

[0094] In step S4, for the deformed first alignment mark, the three-dimensional coordinates of the pixel points in the area where the first alignment mark is located are used for area image stretching.

[0095] S4, correcting the front surface image of the substrate according to the three-dimensional coordinates of each pixel point on the front surface image of the substrate to obtain a virtual front surface image;

[0096] Further, step S4 specifically includes the following steps:

[0097] S401, identifying the deformed first alignment mark on the front surface image of the substrate by an edge contour detection algorithm;

[0098] S402, image segmentation is performed on the region where the deformed first alignment mark is located, to obtain a deformed region image;

[0099] S403, three-dimensional coordinates of each pixel point of a corresponding region of the deformed region image on the front surface image of the substrate are obtained;

[0100] S404, a virtual region image is obtained by image stretching from the center of the deformed region image to the periphery.

[0101] The coordinate change of the first pixel point is:

[0102]

[0103]

[0104] The horizontal coordinate of the first pixel point is x1, the vertical coordinate of the first pixel point is y1, and the height of the first pixel point is h1. The horizontal coordinate of the center point of the deformed region image is x0, and the vertical coordinate of the center point of the deformed region image is y0.

[0105] In the embodiments of the present application, the center pixel point of the deformed region image is the axisymmetric center of the first alignment mark.

[0106] When image stretching is performed, the center pixel point is fixed. In the first stretching direction, there are n1 pixel points between the center pixel point and the image edge, and the position of the first pixel point in this direction is:

[0107]

[0108] The total number of pixel points in the first stretching direction is n0, the height of the first pixel point is h0, the horizontal coordinate of the center point of the deformed region image is x0, and the vertical coordinate of the center point of the deformed region image is y0.

[0109] After stretching each deformed region image, a plurality of virtual region images are obtained.

[0110] ​​​​​​​​​​​​​​​​In the embodiment of the present application, the size of the deformed area image after stretching is larger, and the blank area around the deformed area image is cut off to make the image sizes of the virtual area image and the deformed area image consistent.

[0111] Specifically, the deformed first alignment mark and the surrounding blank area are rectangularly cut, and the image size of the deformed area image is larger than the size of the first alignment mark. If there are j deformed first alignment marks on the deformed area image, j deformed area images are obtained by cutting. The image pixel sizes of the substrate front surface image and the substrate back surface image are the same, so that the two-dimensional coordinates of the pixel points of the first alignment mark and the pixel points of the same area of the substrate back surface image are the same.

[0112] The image size of the virtual area image after stretching is larger. Since the first alignment mark is surrounded by a blank area after the previous rectangular cutting, the area exceeding the image size of the deformed area image is cut off to ensure that the virtual area image after stretching can be spliced into the substrate front surface image.

[0113] S405, splicing the virtual area image into the substrate front surface image to obtain a virtual front surface image.

[0114] S5, aligning by the virtual front surface image and a mask image;

[0115] S6, transferring the mask image to the flexible substrate after alignment.

[0116] In the embodiment of the present application, the depth value of each pixel point scale of the flexible substrate is collected by the grating calibration pattern, and the depth value of the wrinkle deformation is greater than 0. The three-dimensional coordinates of each pixel point of the substrate front surface image are determined by the depth value of each pixel point of the substrate back surface image. The first alignment mark area of the wrinkle deformation is stretched and flattened, so that the alignment algorithm of the photolithography equipment can align the first alignment mark on the substrate front surface image and the second alignment mark on the mask image, and ensure that the multi-layer circuit of the flexible substrate does not dislocate.

[0117] Embodiment two

[0118] A calibration system of a semiconductor photolithography equipment includes a structured light unit, an image collection unit and a calculation unit.

[0119] The structured light unit is used to project a grating calibration pattern to the back surface of a flexible substrate, the image collection unit collects a substrate back surface image with the grating calibration pattern and a substrate front surface image with a first alignment mark, and the calculation unit is used to execute the calibration method of the semiconductor photolithography equipment as shown in embodiment one.

[0120] The solutions of the present application have been described in detail above with reference to the accompanying drawings. In the above examples, the description of each example is focused on a certain aspect, and the parts not described in detail in a certain example can be referred to the relevant description of other examples. It should also be appreciated by those skilled in the art that the actions and modules involved in the specification are not necessarily required by the present application. In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined and reduced in sequence according to actual needs, and the modules in the device embodiments of the present application can be combined, divided and reduced according to actual needs.

[0121] In addition, the method according to the present application can also be implemented as a computer program or computer program product, which includes computer program code instructions for executing part or all of the steps in the above method of the present application.

[0122] Alternatively, the present application can also be implemented as a non-transitory machine readable storage medium (or computer readable storage medium, or machine readable storage medium) having stored executable code (or computer program, or computer instruction code) which, when executed by a processor of an electronic device (or electronic device, server, etc.), causes the processor to perform part or all of the steps of the above method according to the present application.

[0123] Those skilled in the art will also appreciate that the various example logical blocks, modules, circuits, and algorithm steps described in connection with the present application herein can be implemented as electronic hardware, computer software, or combinations of both.

[0124] The flowcharts and block diagrams in the accompanying drawings show the architectural, functional and operational aspects of possible implementations of systems and methods according to embodiments of the present application. In this regard, each block in the flowcharts or block diagrams can represent a module, a program segment or a portion of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different orders than that shown in the figures. For example, two consecutive blocks can actually be executed substantially in parallel, and they can also be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and the combination of blocks in the block diagrams and / or flowcharts, can be implemented by a dedicated hardware-based system that performs the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0125] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. It is intended that the scope of the application be defined by the scope of the patent and by the claims as allowed by the patent office, which can include adaptations based on the description, equivalents, and / or substitutions of elements individually or collectively to the entire disclosure.

Claims

1. A calibration method for semiconductor lithography equipment, characterized in that: The following steps are involved: Projecting a grating calibration pattern on the back side of the flexible substrate to acquire an image of the back side of the substrate; Determine the depth value of each pixel on the back surface image of the substrate by using a phase unwrapping algorithm; acquiring a substrate front surface image of the front surface of the flexible substrate; A first alignment mark is provided on the front surface of the substrate, the substrate front surface image includes a regional image of M first alignment marks, M is an integer greater than or equal to 1, and the first alignment mark is used for mask image alignment; Correcting the substrate front image according to the three-dimensional coordinates of each pixel point on the substrate front image to obtain a virtual front image; Aligning the virtual front image and the mask image; transferring the mask image onto a flexible substrate after alignment; The obtaining of the substrate front surface image of the front surface of the flexible substrate specifically includes: photographing the front surface of the flexible substrate to obtain an image of the front surface of the substrate; Obtaining a depth value of each pixel of the substrate back image; Encoding the depth value of each pixel point of the substrate back image to the corresponding pixel point of the substrate front image to obtain the three-dimensional coordinates of the pixel point of the substrate front image; Correcting the substrate front image according to the three-dimensional coordinates of each pixel point on the substrate front image to obtain a virtual front image specifically includes: identifying the deformed first alignment mark on the substrate front surface image by an edge contour detection algorithm; Performing image segmentation on the area where the deformed first alignment mark is located to obtain an image of the deformed area; Obtaining the three-dimensional coordinates of each pixel point of the corresponding area of ​​the deformed area image on the substrate front image; Taking the center of the deformed region image as the origin, stretching the image in all directions to obtain a virtual region image; The virtual area image is spliced ​​onto the substrate front image to obtain the virtual front image.

2. The calibration method of semiconductor lithography equipment according to claim 1, characterized in that: Determining the depth value of each pixel on the substrate back surface image by using a phase unwrapping algorithm specifically includes: Obtain the light intensity of each pixel at three different phase shift steps; Determine the wrapped phase value of each pixel based on the light intensity of each pixel at three different phase shift steps; Unwrap the wrapped phase value of each pixel to obtain the absolute phase value of each pixel; The depth value of each pixel is determined according to the absolute phase value of each pixel.

3. The calibration method of semiconductor lithography equipment according to claim 2, characterized in that: The grating calibration pattern is Structured light with phase-shifted stripes, is an integer greater than or equal to 1.

4. The method for calibrating semiconductor lithography equipment according to claim 3, wherein: The formula for phase shift fringe is: ； in, is the background light intensity; To modulate the light intensity; is the initial phase value; For the The phase shift value of the step, , is the number of phase shift steps; is the pixel index number; Pixel The depth value of .

5. The method for calibrating semiconductor lithography equipment according to claim 4, wherein: The wrapped phase value of each pixel is determined based on the light intensity of each pixel at three different phase shift steps, specifically including: The wrapped phase value of each pixel is solved by the light intensity and phase solution formula of each pixel at three different phases; the phase solution formula is: ； in, Pixel The wrapped phase value of is the light intensity of the first phase, is the light intensity of the second phase, is the light intensity of the third phase.

6. A calibration system for semiconductor lithography equipment, characterized in that: It includes a structured light unit, an image acquisition unit and a calculation unit; The structured light unit is used to project a grating calibration pattern toward the back surface of the flexible substrate; The image acquisition unit acquires an image of the back side of the substrate with the grating calibration pattern and an image of the front side of the substrate with the first alignment mark; The calculation unit is configured to execute the calibration method for semiconductor lithography equipment according to any one of claims 1 to 5.

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