Backside alignment device, method thereof, and exposure apparatus

Abstract

The application discloses a back surface alignment device and a method thereof and an exposure equipment, wherein the back surface alignment device comprises a workbench, a reference target point, a back surface alignment module, an image acquisition system and a control module. The workbench is used for carrying a mask plate with an alignment target point and has an alignment target point hole and an imaging hole, and the alignment target point of the mask plate is aligned with the alignment target point hole; the reference target point is arranged in the workbench; the back surface alignment module is installed in the workbench and is used for imaging the alignment target point and the reference target point to the imaging hole in the same focal plane; the image acquisition system is arranged above the imaging hole and is used for acquiring images of the alignment target point and the reference target point; and the control module is connected with the image acquisition system and is used for determining the relative position of the alignment target point and the reference target point according to the images of the alignment target point and the reference target point, so as to perform exposure control according to the position. The application solves the problem that the pixel drift of the CCD camera caused by the temperature influence leads to the error of the target point alignment, and improves the alignment precision.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a back-side alignment apparatus and method thereof, and an exposure device. Background Technology

[0002] Photolithography can print characteristic patterns on a substrate surface to manufacture semiconductor devices, various integrated circuits, flat panel displays, circuit boards, biochips, microelectromechanical chips, optoelectronic circuit chips, and more. Because today's chips are increasingly complex, multiple layers of exposure are often required on a single chip, and the circuits between each layer inevitably have certain connections and mating relationships. Therefore, before exposure, the silicon wafer must be adjusted to the appropriate position so that the current exposure aligns with the previously exposed pattern; this is called alignment. In the fabrication processes of devices such as MST (Microsystem Technology) and MEMS (Microelectromechanical Systems), both sides of the silicon wafer need to be exposed, and there is an overlay requirement between the front and back exposed patterns. Typically, in this case, the alignment marks are on the opposite side of the exposed surface, hence the term back-side alignment.

[0003] Among related technologies, the main method for achieving back-side alignment of silicon wafers is the visible light measurement method. This method involves installing optical path deflection and imaging systems on both sides of the bottom of the silicon wafer stage, using visible light to illuminate and image the markings on the back of the wafer. The calibration of the alignment mark position coordinates is achieved through image acquisition and processing using a CCD (Charge-Coupled Device Camera). However, due to factors such as ambient temperature and prolonged use leading to temperature increases, CCD cameras are prone to pixel drift (temperature drift), resulting in alignment errors and failing to meet the accuracy requirements of the aforementioned application chips. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of this invention is to provide a back-side alignment device. This back-side alignment device solves the problem of target alignment errors caused by temperature drift, thereby improving exposure alignment accuracy.

[0005] The second objective of this invention is to provide an exposure apparatus.

[0006] The third objective of this invention is to provide a back-side alignment method.

[0007] The fourth objective of this invention is to provide an exposure device.

[0008] To achieve the above objectives, a back-side alignment apparatus according to a first aspect of the present invention includes: a worktable for supporting a mask plate with alignment target points, the worktable having alignment target point holes and an imaging hole, wherein the alignment target points of the mask plate are aligned with the alignment target point holes; a reference target point disposed within the worktable; a back-side alignment module installed within the worktable for imaging the alignment target point and the reference target point onto the imaging hole in a cofocal manner; an image acquisition system disposed above the imaging hole for acquiring images of the alignment target point and the reference target point; and a control module connected to the image acquisition system for determining the relative positions of the alignment target point and the reference target point based on the images of the alignment target point and the reference target point, so as to perform exposure control based on the relative positions.

[0009] According to the back alignment device of the present invention, a set pattern is formed by the reference target point and the alignment target point of the mask plate. The back alignment module images the alignment target point and the reference target point on the same focal plane to the imaging hole. The control module controls the image acquisition system to simultaneously acquire the images of the alignment target point and the reference target point at the imaging hole, and performs exposure control according to the relative position of the alignment target point and the reference target point. This solves the problem of target point alignment error caused by temperature drift in the image acquisition system and improves the exposure alignment accuracy.

[0010] In some embodiments, the back alignment module includes: a first light deflection module, a relay lens group, and a second light deflection module arranged sequentially along the light propagation direction; the reference target point is disposed on the side of the first light deflection module away from the relay lens group; the first light deflection module is disposed below the alignment target hole and forms a first angle with the hole surface of the alignment target hole, and is used to transmit reflected light carrying the images of the alignment target point and the reference target point to the relay lens group; the relay lens group is used to image the reflected light carrying the images of the alignment target point and the reference target point on the same focal plane and project it onto the second light deflection module; the second light deflection module is used to project the imaging light onto the imaging hole, avoiding the need to pass through two relay lens groups for imaging, improving the energy utilization rate of reflective back alignment, and improving the imaging quality of the target point.

[0011] In some embodiments, the first light deflection module includes a semi-transparent mirror, and the second light deflection module includes a reflective mirror. The first light deflection module serves to reflect and project light, while the second light deflection module serves to reflect light.

[0012] In some embodiments, the back alignment module further includes an illumination system disposed below the first light deflection module for generating illumination light, and the illumination light is projected onto the alignment target and the reference target respectively through the first light deflection module.

[0013] In some embodiments, the lighting system includes: a light source for generating the illumination light; and a collimating lens for collimating the illumination light to form parallel illumination light and projecting it onto the first light deflection module.

[0014] In some embodiments, the worktable forms a receiving cavity; the back alignment module further includes a base plate, which is removably disposed along the bottom of the receiving cavity; the first light deflection module, the relay lens group, the second light deflection module, and the illumination system are all disposed on the base plate. By allowing the back alignment imaging module to be independently removed, offline installation and debugging are facilitated, reducing the overall system installation and debugging workload, and also facilitating subsequent maintenance of the entire system.

[0015] By pushing and pulling the base plate, the lighting can be easily adjusted, thereby reducing the workload during the adjustment process.

[0016] In some embodiments, the image acquisition system includes a CCD camera and an objective lens of an exposure system for imaging and capturing the center coordinates of the target point transferred by the relay lens group.

[0017] In some embodiments, the control module is further configured to acquire an initial image of the reference target point when the worktable is not loaded with the mask, obtain a first reference center coordinate of the reference target point based on the initial image, and obtain the alignment center coordinate of the alignment target point and the second reference center coordinate of the reference target point based on the images of the alignment target point and the reference target point, and obtain the exposure start point coordinates and the graphic expansion / contraction amount based on the first reference center coordinates, the second reference center coordinates and the alignment center coordinates.

[0018] In some embodiments, when the control module obtains the exposure start point coordinates and the graphic scaling amount based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates, it is used to obtain the center coordinate difference based on the second reference center coordinates and the alignment center coordinates, use the sum of the first reference center coordinates and the center coordinate difference as the imaging center coordinates of the target point to eliminate errors, and calculate the exposure start point coordinates and the graphic scaling amount based on the mapping relationship between the imaging center coordinates and the actual target point coordinates.

[0019] In some embodiments, the reference target, the back alignment module, and the image acquisition system are all in two sets.

[0020] To achieve the above objectives, the exposure apparatus of the second aspect of the present invention includes an exposure system and the back alignment device described in the above embodiment.

[0021] According to the embodiment of the present invention, the exposure device, by using the back alignment device described in the above embodiment, achieves imaging of the alignment target point and the reference target point onto the imaging aperture with the same focal plane. The image acquisition system captures the target point image and processes and analyzes the target point image to obtain the coordinates of the exposure start point and the graphic expansion / contraction. The exposure system can perform the exposure operation based on this data information, which solves the problem of alignment error in the calibration of the target point alignment coordinates caused by temperature drift of the CCD camera, improves the alignment accuracy of the target point, and thus improves the exposure accuracy of the exposure device, thereby effectively ensuring the production quality of the product.

[0022] To achieve the above objectives, a back-side alignment method according to a third aspect of the present invention is used in the back-side alignment apparatus described in the above embodiments. The back-side alignment method includes: acquiring images of an alignment target point and a reference target point in the back-side alignment apparatus; determining the relative position of the alignment target point and the reference target point based on the images of the alignment target point and the reference target point, so as to perform exposure control based on the relative position.

[0023] According to the back alignment method of the present invention, by acquiring images of the alignment target and the reference target in the back alignment device, and determining the relative position of the alignment target and the reference target based on the images for exposure, the problem of target alignment error caused by temperature drift of CCD camera in image acquisition system is solved, the accuracy of CCD camera in identifying target alignment is improved, and thus the exposure quality of image is guaranteed.

[0024] In some embodiments, determining the relative position of the alignment target and the reference target based on images of the alignment target and the reference target, and performing exposure control based on the relative position, includes: acquiring an initial image of the reference target when the stage of the back alignment device is not loaded with a mask; obtaining a first reference center coordinate of the reference target based on the initial image; obtaining alignment center coordinates of the alignment target and a second reference center coordinate of the reference target based on images of the alignment target and the reference target; and obtaining exposure start point coordinates and pattern scaling based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates.

[0025] In some embodiments, obtaining the exposure start point coordinates and graphic scaling amount based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates includes: obtaining the center coordinate difference based on the second reference center coordinates and the alignment center coordinates; using the sum of the first reference center coordinates and the center coordinate difference as the imaging center coordinates of the alignment target point to eliminate errors; and calculating the exposure start point coordinates and graphic scaling amount based on the mapping relationship between the imaging center coordinates and the actual target point coordinates.

[0026] To achieve the above objectives, an exposure apparatus according to a fourth aspect of the present invention includes: a processor; a memory communicatively connected to the processor; the memory storing a computer program executable by the processor, wherein the processor executes the computer program to implement the back-side alignment method described in the above embodiment.

[0027] According to the exposure apparatus of the present invention, the processor implements the back alignment method described in the above embodiment by executing a computer program, which solves the problem of alignment error in the calibration of target alignment coordinates caused by temperature drift of the CCD camera, improves the alignment accuracy of the target, ensures the exposure quality of the image, and thus improves the production quality and production efficiency of the exposure apparatus.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 This is a schematic diagram of a back-side alignment device according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of a reference target according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the bearing surface of a workbench according to an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of a back alignment module according to an embodiment of the present invention;

[0034] Figure 5 This is a structural diagram of a back-side alignment module according to an embodiment of the present invention;

[0035] Figure 6 This is a diagram showing the positional relationship of target points according to an embodiment of the present invention;

[0036] Figure 7 This is a block diagram of an exposure apparatus according to an embodiment of the present invention;

[0037] Figure 8 This is a flowchart of an exposure apparatus according to an embodiment of the present invention;

[0038] Figure 9 This is a flowchart of a back-side alignment method according to an embodiment of the present invention;

[0039] Figure 10 This is a flowchart illustrating the determination of the relative position of a target point according to an embodiment of the present invention;

[0040] Figure 11 This is a flowchart of obtaining the exposure start point coordinates and graphic expansion / contraction amount according to an embodiment of the present invention;

[0041] Figure 12 This is a schematic diagram of an exposure apparatus according to an embodiment of the present invention.

[0042] Figure label:

[0043] Exposure equipment 1;

[0044] Back alignment device 100; exposure system 200; memory 300; processor 400;

[0045] Worktable 10; Reference target point 20; Back alignment module 30; Image acquisition system 40; Control module 50; Alignment target point 60; Imaging target point 70;

[0046] Mask plate 11; Target alignment hole 12; Imaging hole 13; Mounting hole 14; First light deflection module 31; Relay lens group 32; Second light deflection module 33; Illumination system 34; Base plate 35;

[0047] Light source 341; collimating lens 342. Detailed Implementation

[0048] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0049] The following is for reference. Figures 1-6 A back-side alignment device according to an embodiment of the present invention is described.

[0050] Figure 1 This is a schematic diagram of a back-side alignment device according to an embodiment of the present invention, as shown below. Figure 1 As shown, the back alignment device 100 includes: a worktable 10, a reference target 20, an image acquisition system 40, and a control module 50.

[0051] The worktable 10 is used to support the mask 11 with alignment target 60. The mask 11 is a sample or product with alignment target 60 produced by the customer. The material of the mask 11 can be quartz glass, soda glass, film, etc., without specific limitations. The worktable 10 has alignment target hole 12 and imaging hole 13, and the alignment target 60 of the mask 11 is aligned with the alignment target hole 12.

[0052] The photomask 11 mainly serves as a carrier of graphic information. Through the exposure process, it transfers the pattern to the exposed product (e.g., silicon wafer, conductive glass, copper foil, etc.), thereby realizing the pattern transfer. It is mainly used in industries such as IC (Integrated Circuit), IC packaging, MEMS, power devices and discrete devices, FPD (Flat Panel Display), circuit board industry, LED (Light Emitting Diode) and fine optical components.

[0053] Reference target point 20 is a fixed target point in the image acquisition field of view, set within the worktable 10. Its function is to form a line group or nested pattern with the alignment target point 60 in the mask 11. When the image acquisition system 40 acquires images, it serves as a reference to the alignment target point 60 on the mask 11, eliminating target point alignment errors caused by CCD camera temperature drift. Figure 2 As shown, the reference target 20 can be a cross-shaped target, or it can be a circular target or a target of other shapes. No specific restrictions are imposed here.

[0054] The back alignment module 30 is installed inside the worktable 10, such as Figure 3 As shown, the bearing surface of the worktable 10 is provided with mounting holes 14 for the back alignment module 30, which can be installed and fixed through the upper holes, facilitating installation, adjustment and disassembly, thereby solving the problem of difficult back alignment maintenance. The back alignment module 30 can be used to image the alignment target point 60 and the reference target point 20 onto the imaging hole 13 in a cofocal plane to obtain a high-quality target image.

[0055] The image acquisition system 40 is positioned above the imaging aperture 13 and is used to acquire images of the alignment target 60 and the reference target 20. The control module 50 is connected to the image acquisition system 40 and is used to determine the relative position of the alignment target 60 and the reference target 20 based on the images of the alignment target 60 and the reference target 20, so as to perform exposure control based on the relative position.

[0056] Specifically, during back alignment, the illumination light passes through the back alignment module 30 and illuminates the alignment target 60 area of ​​the mask 11 and the reference target 20 area in the worktable 10, respectively. The reflected light from the alignment target 60 of the mask 11 and the reference target 20 in the worktable 10 passes through the back alignment module 30 again, so that the alignment target 60 and the reference target 20 are imaged on the same focal plane at the imaging hole 13. The image acquisition system 40 acquires the images of the alignment target 60 and the reference target 20 and transmits the images to the control module 50. The control module 50 performs data analysis based on the images to determine the relative position of the alignment target 60 and the reference target 20. The control module 50 adjusts the exposure pattern according to the relative position so that the pattern beam is accurately projected onto the surface of the product to be processed.

[0057] According to the back alignment device 100 of the present invention, a reference target point 20 and the alignment target point 60 of the mask plate 11 are used to form a set pattern. The back alignment module 30 images the alignment target point 60 and the reference target point 20 onto the imaging hole 13 in a cofocal plane. The control module 50 controls the image acquisition system 40 to simultaneously acquire the images of the alignment target point 60 and the reference target point 20 at the imaging hole 13, and determines the relative position of the alignment target point 60 and the reference target point 20 based on the images for exposure control. This solves the problem of target alignment error caused by temperature drift in the CCD camera in the image acquisition system 40, improves the accuracy of the CCD camera in identifying target alignment, and thus ensures the exposure quality of the image.

[0058] Figure 4 This is a schematic diagram of a back-side alignment module according to an embodiment of the present invention. Figure 4 As shown, the back alignment module 30 includes: a first light deflection module 31, a relay lens group 32, a second light deflection module 33, and an illumination system 34.

[0059] The first light deflection module 31, the relay lens group 32, and the second light deflection module 33 are arranged sequentially along the light propagation direction. The reference target point 20 is located on the side of the first light deflection module 31 away from the relay lens group 32. The first light deflection module 31 is located below the alignment target hole 12 and forms a first angle with the hole surface of the alignment target hole 12. It is used to transmit the reflected light carrying the image of the alignment target point 60 and the reference target point 20 to the relay lens group 32.

[0060] In some embodiments, the relay lens group 32 features high resolution, dual telecentricity, and a symmetrical structure. The symmetrical structure effectively reduces imaging aberrations in the relay lens group 32 and improves the imaging quality of the system. The relay lens group 32 has a minimum resolution of 2µm, an object-image telecentricity of less than 0.1%, and distortion close to 0. The relay lens group 32 images the alignment target point 60 in the mask plate 11 onto an area outside the mask plate 11. It can image the reflected light carrying the images of the alignment target point 60 and the reference target point 20 onto the same focal plane and project it onto the second light deflection module 33. The second light deflection module 33 projects the imaging light into the imaging aperture 13, which is on the same horizontal plane as the worktable 10.

[0061] In some embodiments, the first light deflection module 31 includes a semi-transparent and semi-reflective mirror, and the second light deflection module 33 includes a reflective mirror. One side of the semi-transparent and semi-reflective mirror is a mirror surface, which reflects light, while the other side is an anti-reflective surface, allowing light to pass through. Therefore, the first light deflection module 31 serves to reflect and transmit light, while the second light deflection module 33 serves to reflect light.

[0062] The illumination system 34 is located below the first light deflection module 31 and is aligned with the alignment target point 60 and the alignment target hole 12 of the mask plate 11. The illumination system 34 is used to generate illumination light, and the illumination light is projected onto the alignment target point 60 and the reference target point 20 respectively through the first light deflection module 31.

[0063] The lighting system 34 includes a light source 341 and a collimating lens 342. In some embodiments of the present invention, the light source 341 can be an LED or laser with a small divergence angle to generate illumination light. The collimating lens 342 is used to collimate the illumination light to form parallel illumination light and project it onto the first light deflection module 31. Here, collimation means transforming the divergent light from the light source 341 into parallel light through Fourier transform, ultimately forming a Köhler lighting system 34 with better uniformity.

[0064] The following is for reference. Figure 4 The light transmission path in the back alignment device 100 is described in detail.

[0065] During back-side alignment, the light source 341 in the illumination system 34 emits illumination light. This illumination light is collimated by the collimating lens 342 to form parallel illumination light and projected onto the first light deflection module 31. A portion of this light directly illuminates the alignment target 60 area on the mask 11, while the other portion is reflected to the reference target 20, illuminating it as well. Based on the principle of reflection, the reflected light from the alignment target 60 on the mask 11 is deflected by the first light deflection module... Block 31 reflects the light into the relay lens group 32. The reflected light from the reference target 20 is projected into the relay lens group 32 through the first light deflection module 31. The relay lens group 32 images the reflected light carrying the images of the aligned target 60 and the reference target 20 onto the same focal plane and projects it to the second light deflection module 33. Through the second light deflection module 33, the imaging light of the aligned target 60 and the reference target 20 onto the same focal plane is reflected into the imaging aperture 13, and the image acquisition system 40 acquires and captures the imaging target 70 in the imaging aperture 13.

[0066] Therefore, by placing the illumination system 34 below the first light deflection module 31 and placing the reference target 20 to the side of the illumination system 34 and the first light deflection module 31, and following the light transmission path described above—that is, through the collimating lens, the semi-transparent and semi-reflective lens, the relay lens group 32, and the reflecting lens—the imaging light that is aligned with the focal plane of the target 60 and the reference target 20 can be projected onto the imaging aperture 13. This effectively reduces the path of light propagation, reduces light loss during transmission, and improves the utilization rate of light energy.

[0067] Figure 5 This is a structural diagram of a back-side alignment device according to an embodiment of the present invention. Figure 5 As shown, the stage 10 in the back alignment device 100 forms a receiving cavity. The back alignment module 30 also includes a base plate 35, which is removable and placeable along the bottom of the receiving cavity. That is, it can be removed or placed into the receiving cavity along the bottom of the cavity. It can be completely removed and detached from the base plate, or it can be set to a push-pull type for removal and placement, or other applicable removal and placement methods can be used, without specific limitations. The first light deflection module 31, the relay lens group 32, the second light deflection module 33, and the illumination system 34 are all mounted on the base plate 35, constituting the imaging module. The imaging module can be easily removed and placed through the base plate 35, that is, the back-aligned imaging module can be independently removed through the base plate 35, thereby facilitating its offline installation and debugging work, reducing the installation and debugging workload of the entire system, and also facilitating subsequent maintenance of the entire system.

[0068] In some embodiments, the image acquisition system 40 includes a CCD camera and the objective lens of the exposure system 200. The CCD camera's function is to image and capture the center coordinates of the target point transferred by the relay lens group 32. These center coordinates are the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates. The objective lens of the exposure system 200, as an important component of the exposure system 200, primarily functions to adjust the focal length and lateral magnification to ensure the accuracy and precision of the exposure.

[0069] The first reference center coordinates are obtained by the control module 50 controlling the image acquisition system 40 to acquire an initial image of the reference target point 20 when the worktable 10 is not loaded with the mask 11, and obtaining the center coordinates of the reference target point 20 based on the initial image. The second reference center coordinates are obtained by the control module 50 controlling the image acquisition system 40 to acquire an image of the reference target point 20 after the worktable 10 is loaded with the mask 11, and obtaining the center coordinates of the reference target point 20 based on the image. The alignment center coordinates are obtained by the control module 50 controlling the image acquisition system 40 to acquire an image of the alignment target after the worktable 10 is loaded with the mask 11, and obtaining the center coordinates of the alignment target point 60 based on the image. The exposure start point coordinates and the graphic scaling amount are obtained based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates.

[0070] When the control module 50 obtains the exposure start point coordinates and pattern scaling amount based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates, it obtains the center coordinate difference based on the second reference center coordinates and the alignment center coordinates, uses the sum of the first reference center coordinates and the center coordinate difference as the imaging center coordinates of the alignment target 60 to eliminate errors, and calculates the exposure start point coordinates and pattern scaling amount based on the mapping relationship between the imaging center coordinates and the actual target point coordinates.

[0071] In some embodiments of the present invention, the reference target 20, the back alignment module 30, and the image acquisition system 40 of the back alignment device 100 are all in two sets. Therefore, as Figure 6 As shown, Figure 6 The system displays the reference center coordinates of two sets of reference target points 20, the alignment center coordinates of two sets of alignment target points 60, and the positional relationship of the two sets of image center coordinates. Based on the positional relationship of these coordinates, the exposure start point coordinates and image scaling are obtained to eliminate alignment errors caused by CCD temperature drift, thereby improving alignment accuracy.

[0072] Specifically, the back alignment module 30 is integrated into the worktable 10 for fixation and connected to the electronic control system. First, without placing a mask plate in the worktable 10, the image acquisition system 40 acquires the first reference center coordinates of the imaging reference target point 20 (Ref-mark) in the imaging aperture 13, denoted as (XRef-mark1, YRef-mark1). The image acquisition system 40 acquires the second reference center coordinates of the imaging reference target point 20 (Ref-mark) in the imaging aperture 12, denoted as (XRef-mark2, YRef-mark2). The image acquisition system 40 measures the size of the reference target point Ref-mark1, denoted as l'. The magnification of the imaging module is calculated using βL = l' / l (where l is the actual size of the reference target point and βL is the magnification of the left imaging module). The magnification βR of the right imaging module is calculated in the same way.

[0073] Then, the mask 11 with the alignment target 60 (real mark) is placed on the worktable 10, and the alignment target on the mask 11 is aligned with the alignment target hole 12 on the worktable. The image acquisition system 40 simultaneously acquires the first reference center coordinates (XRef-mark1, YRef-mark1) of the reference target 20 in the imaging hole 13 and the coordinates (XIm-mark1, YIm-mark1) of the imaging target 70 after the alignment target 60 is imaged by the back alignment module 30, and calculates the center coordinate difference (ΔX, ΔY). According to the object-image relationship in the imaging principle, in a symmetrical imaging system, the object and image are centrally rotationally symmetrical. According to the position transformation processing technology formula:

[0074]

[0075] Therefore, it can be deduced that:

[0076]

[0077] In the same way, the alignment target point on the right side of the mask plate 11 can be calculated, and the alignment exposure can be performed by using the center coordinates of the two target points.

[0078] The following describes an exposure apparatus according to a second aspect of the present invention.

[0079] Figure 7 This is a block diagram of an exposure apparatus according to an embodiment of the present invention. Figure 7 As shown, the exposure apparatus 1 includes an exposure system 200 and a back alignment device 100. The back alignment device 100 is used for alignment operations, and the exposure system 200 is used for exposure operations.

[0080] Figure 8This is a flowchart of an exposure apparatus according to an embodiment of the present invention, such as... Figure 8 As shown, the working process of the exposure device 11 in this embodiment of the invention includes at least the following steps S1-S4.

[0081] S1, add target points on the back of the mask.

[0082] The photomask 11 is an important material used in the fabrication of semiconductor devices, integrated circuits, and microelectronic components. During the fabrication of the photomask 11, target points need to be attached to its back side for alignment and positioning. These target points can be tiny dot-like structures made of metal or translucent materials, typically tens of micrometers in diameter. During the fabrication of the photomask 11, these target points need to be precisely positioned at specific locations on the back side of the photomask 11 and fixed to its surface.

[0083] S2, the alignment point of the mask plate is transferred according to the back alignment device.

[0084] After the target point is attached to the back of the mask 11, the alignment target point 60 and reference target point 20 of the mask 11 need to be transferred to the exposure system 200 by the back alignment device 100 for subsequent exposure operations. In this embodiment of the invention, the back alignment device 100 is composed of a series of optical elements, such as collimating lenses, semi-transparent and semi-reflective lenses, relay lens group 32, and reflecting lenses, which can transfer the image of the target point to the image acquisition system 40.

[0085] S3: Based on the image of the target point captured by the image acquisition system, obtain the coordinates of the exposure start point and the graphic expansion / contraction amount.

[0086] The image acquisition system 40 captures the target image, processes and analyzes the target image, calculates the center coordinates, shape, rotation angle and other information of the target, thereby obtaining the exposure start point coordinates and graphic expansion and contraction, and transmits this information to the exposure system 200 through the control module 50.

[0087] S4, the exposure system performs the exposure operation.

[0088] After the precise location of the target point is determined, the exposure system 200 can begin the exposure operation. The exposure system 200 typically consists of a series of optical elements and a light source 341, which generates high-energy light to expose the mask 11. The exposure process usually requires control of parameters such as exposure time, energy, and wavelength to ensure the exposure quality and stability of the mask 11. After exposure, the mask 11 can be removed for subsequent processing and manufacturing.

[0089] According to the embodiment of the present invention, the exposure device 1, by using the back alignment device 100 described in the above embodiment, achieves the imaging of the alignment target 60 and the reference target 20 onto the imaging aperture 13 with the same focal plane. The image acquisition system 40 captures the target image and processes and analyzes the target image to obtain the coordinates of the exposure start point and the graphic expansion and contraction. The exposure system 200 can perform the exposure operation based on these data information, which solves the problem of alignment error in the calibration of the target alignment coordinates caused by temperature drift of the CCD camera, improves the alignment accuracy of the target, and thus improves the exposure accuracy of the exposure device 1, thereby effectively ensuring the production quality of the product.

[0090] The following describes a back-side alignment method according to a third aspect of the present invention.

[0091] The back-side alignment method is used in the back-side alignment device described in the above embodiments. Figure 9 This is a flowchart of a back-side alignment method according to an embodiment of the present invention, as follows: Figure 9 As shown, the back-side alignment method includes at least the following steps S10-S20.

[0092] S10, acquire images of the alignment target and reference target in the back alignment device.

[0093] By employing the back alignment module described in the above embodiment, the alignment target and the reference target are imaged onto the imaging aperture in a cofocal manner, and the image acquisition system can acquire the target image at the imaging aperture.

[0094] S20: Determine the relative positions of the target point and the reference target point based on the images of the target point and the reference target point, so as to perform exposure control based on the relative positions.

[0095] Specifically, Figure 10 This is a flowchart illustrating the determination of the relative position of a target point according to an embodiment of the present invention. Figure 10 As shown, determining the relative position of the target point includes at least the following steps S100-S103.

[0096] S100: Acquire an initial image of the reference target point when the stage of the back alignment device is not loaded with a mask.

[0097] S101, Obtain the first reference center coordinates of the reference target point based on the initial image.

[0098] S102, obtain the alignment center coordinates of the alignment point and the second reference center coordinates of the reference target based on the images of the alignment point and the reference target.

[0099] Among them, obtaining the center coordinates of the target point from the image allows for image processing and analysis using computer vision technology, including the following steps.

[0100] First, the acquired images are preprocessed, such as by grayscale conversion, smoothing filtering, denoising, and binarization, to enhance the contrast and edge information of the target points, facilitating subsequent processing and analysis.

[0101] Second, edge detection algorithms, such as the Canny algorithm or the Sobel algorithm, are used to extract the edge information of the target point. This step can obtain the approximate location and shape of the target point.

[0102] Third, based on the edge information, a contour detection algorithm, such as the findContours function in the OpenCV library, is used to detect the contour of the target point. This step can obtain the precise location and shape of the target point.

[0103] Fourth, based on the target's contour, calculate the target's center coordinates using the contour moments method. In the OpenCV library, the `moments` function can be used to calculate the geometric moments and central moments of the target's contour, thereby obtaining the target's center coordinates.

[0104] S103, obtain the exposure start point coordinates and graphic expansion / contraction amount based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates.

[0105] Specifically, Figure 11 This is a flowchart illustrating the process of obtaining the coordinates of the exposure start point and the graphic scaling amount according to an embodiment of the present invention. Figure 11 As shown, obtaining the exposure start point coordinates and graphic expansion / contraction includes at least the following steps S200-S202.

[0106] S200, obtain the center coordinate difference based on the second reference center coordinates and the alignment center coordinates.

[0107] S201, the sum of the first reference center coordinates and the center coordinate difference is used as the imaging center coordinates of the target point to eliminate errors.

[0108] S202, calculate the exposure start point coordinates and graphic expansion / contraction based on the mapping relationship between the imaging center coordinates and the alignment center coordinates.

[0109] Pattern shrinkage refers to the difference between the actual physical size of a pattern and its expected size, usually expressed as a scaling factor. Pattern shrinkage is mainly affected by factors such as material properties, processing technology, and equipment precision. For example, during photolithography, factors such as the refractive index and diffraction of ultraviolet light can affect pattern shrinkage. In fields such as micro-nano fabrication and semiconductor technology, the magnitude of pattern shrinkage has a significant impact on product quality and performance, thus requiring precise measurement and control.

[0110] According to the back alignment method of the present invention, by using the back alignment device described in the above embodiment, the first reference center coordinates of the reference target point when the worktable is not loaded with a mask, and the second reference center coordinates of the reference target point and the alignment center coordinates of the alignment target point after the mask is loaded, can be obtained. The coordinates of the exposure start point and the graphic expansion / contraction amount can be obtained by calculating the coordinates. The exposure system can perform the exposure operation according to the data, which solves the problem of target point alignment error caused by temperature drift of the CCD camera in the image acquisition system, improves the accuracy of the CCD camera in identifying target point alignment, and thus ensures the exposure quality of the image.

[0111] Figure 12 This is a schematic diagram of an exposure apparatus according to an embodiment of the present invention. Figure 12 As shown, the exposure device 1 includes a processor 400 and a memory 300 communicatively connected to the processor 400.

[0112] The memory 300 stores a computer program that can be executed by the processor 400. When the processor 400 executes the computer program, it implements the back-side alignment method described in the above embodiment.

[0113] According to the embodiment of the present invention, the processor 400 implements the back alignment method described in the above embodiment by executing a computer program in the exposure device 1. This solves the problem of alignment error in the calibration of the target alignment coordinates caused by temperature drift of the CCD camera, improves the alignment accuracy of the target, and ensures the exposure quality of the image, thereby improving the production quality and production efficiency of the exposure device 1.

[0114] The memory 300 in this embodiment of the invention may include, but is not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical or magnetic storage media, which will not be described in detail here.

[0115] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0116] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A back-side alignment device, characterized in that, include: A worktable for supporting a mask plate with alignment target points, the worktable having alignment target point holes and imaging holes, wherein the alignment target points of the mask plate are aligned with the alignment target point holes; A reference target point is provided within the worktable; A back alignment module is installed inside the worktable and is used to image the alignment target point and the reference target point onto the imaging aperture in a cofocal manner. An image acquisition system, wherein the image acquisition system is disposed above the imaging aperture, is used to acquire images of the alignment target point and the reference target point; A control module, connected to the image acquisition system, is used to acquire an initial image of the reference target point when the worktable is not loaded with the mask plate, obtain the first reference center coordinates of the reference target point based on the initial image, and obtain the alignment center coordinates and the second reference center coordinates of the reference target point based on the images of the alignment target point and the reference target point, obtain the center coordinate difference based on the second reference center coordinates and the alignment center coordinates, use the sum of the first reference center coordinates and the center coordinate difference as the imaging center coordinates of the alignment target point to eliminate errors, and calculate the exposure start point coordinates and the image scaling amount based on the mapping relationship between the imaging center coordinates and the actual target point coordinates.

2. The back-side alignment device according to claim 1, characterized in that, The back alignment module includes: A first light deflection module, a relay lens group, and a second light deflection module are sequentially arranged along the direction of light propagation. The reference target point is set on the side of the first light deflection module away from the relay lens group; The first light deflection module is disposed below the alignment target hole and forms a first angle with the hole surface of the alignment target hole, and is used to transmit the reflected light carrying the image of the alignment target and the reference target to the relay lens group. The relay lens group is used to image the reflected light carrying the images of the alignment target and the reference target on the same focal plane and project it onto the second light deflection module. The second light deflection module is used to project the imaging light onto the imaging aperture.

3. The back-side alignment device according to claim 2, characterized in that, The first light deflection module includes a semi-transparent and semi-reflective mirror, and the second light deflection module includes a reflective mirror.

4. The back-side alignment device according to claim 2, characterized in that, The back alignment module also includes: An illumination system is disposed below the first light deflection module to generate illumination light, which is then projected onto the alignment target and the reference target respectively through the first light deflection module.

5. The back-side alignment device according to claim 4, characterized in that, The lighting system includes: A light source, used to generate the illumination light; A collimating lens is used to collimate the illumination light to form parallel illumination light and project it onto the first light deflection module.

6. The back-side alignment device according to claim 4, characterized in that, The worktable has a receiving cavity; The back alignment module also includes a base plate, which is removably and placeable along the bottom of the receiving cavity; The first light deflection module, the relay lens group, the second light deflection module, and the lighting system are all mounted on the base plate.

7. The back-side alignment device according to claim 1, characterized in that, The image acquisition system includes a CCD camera and an objective lens for the exposure system.

8. The back-side alignment device according to any one of claims 1-7, characterized in that, The reference target, the back alignment module, and the image acquisition system are all in two sets.

9. An exposure apparatus, characterized in that, Includes an exposure system and a back-side alignment device as described in any one of claims 1-8.

10. A back-side alignment method, characterized in that, The back-side alignment apparatus according to any one of claims 1-8, the back-side alignment method comprising: Acquire images of the alignment target point and the reference target point in the back alignment device; The relative positions of the alignment target and the reference target are determined based on the images of the alignment target and the reference target, so as to perform exposure control based on the relative positions.

11. The back-side alignment method according to claim 10, characterized in that, Determining the relative position of the alignment target and the reference target based on the images of the alignment target and the reference target, and performing exposure control based on the relative position, includes: Acquire an initial image of the reference target point when the worktable of the back alignment device is not loaded with a mask; The first reference center coordinates of the reference target point are obtained based on the initial image; The alignment center coordinates of the alignment target and the second reference center coordinates of the reference target are obtained based on the images of the alignment target and the reference target. The exposure start point coordinates and graphic expansion / contraction are obtained based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates.

12. The back-side alignment method according to claim 11, characterized in that, Obtaining the exposure start point coordinates and graphic scaling based on the first reference center coordinates, the second reference center coordinates, and the alignment center coordinates includes: The center coordinate difference is obtained based on the second reference center coordinates and the alignment center coordinates; The sum of the differences between the first reference center coordinates and the center coordinates is used as the imaging center coordinates of the target point to eliminate errors; The exposure start point coordinates and graphic expansion / contraction are calculated based on the mapping relationship between the imaging center coordinates and the actual target point coordinates.

13. An exposure apparatus, characterized in that, include: processor; The memory is communicatively connected to the processor; The memory stores a computer program that can be executed by the processor, and when the processor executes the computer program, it implements the back-side alignment method according to any one of claims 10-12.

Images