Patterning method

Abstract

The present disclosure provides a patterning method, which belongs to the technical field of semiconductors. The patterning method comprises: disposing a negative photoresist on a surface of a wafer; exposing the photoresist; developing the wafer so that the photoresist forms a photoresist mask; forming a metal film on the surface of the wafer and the surface of the photoresist mask under the cover of the photoresist mask; and removing the metal film on the surface of the photoresist mask and the photoresist mask. The present disclosure can improve the effect of removing the metal film.

Description

Technical Field

[0001] This disclosure belongs to the field of semiconductor technology, and particularly relates to a graphical method. Background Technology

[0002] In the manufacturing process of light-emitting diode (LED) chips, the formation of metal patterns is one of the key steps that determines the photoelectric performance of the device.

[0003] In related technologies, lift-off processes are widely used in the industry to obtain high-reflectivity silver mirrors or reliable metal pads. The standard procedure is as follows: First, a negative photoresist is coated on the substrate. After exposure, baking, and development, the photoresist forms the desired window pattern. Then, a metal thin film (such as silver or gold) is deposited on the entire wafer surface through physical vapor deposition (PVD). Finally, a lift-off step is performed to remove the entire metal thin film covering the photoresist, leaving only the metal thin film within the window.

[0004] However, during the growth of the epitaxial wafer of a light-emitting diode (LED) chip, the edge region exhibits a microscopic peak-valley rough structure caused by the edge effect of epitaxial growth. When photoresist is applied to this rough structure, it forms a discontinuous and uneven film layer at the microscale. During subsequent exposure, areas not exposed to ultraviolet light will appear, resulting in exposed wafers. In the PVD process, metal atoms can penetrate these weak points in the discontinuous and uneven film layer or directly contact the rough structure, forming mechanical "anchor points." During subsequent gold removal, stress cannot be effectively transferred to these "locked" metals, causing them to remain at the edges, forming difficult-to-remove metal wire-like residues. These residues not only cause short circuits and leakage in the chip, severely reducing yield and reliability, but also increase the risk of wafer breakage during subsequent thinning and dicing processes due to uneven stress. Summary of the Invention

[0005] This disclosure provides a graphical method to improve metal removal efficiency. The technical solution is as follows: This disclosure provides a patterning method, which includes: depositing a negative photoresist on the surface of a wafer; exposing the photoresist such that the exposure dose of the edge region of the photoresist is greater than the exposure dose of the center region of the photoresist; developing the wafer to form a photoresist mask; forming a metal thin film on the surface of the wafer and the surface of the photoresist mask under the cover of the photoresist mask; and removing the metal thin film and the photoresist mask from the surface of the photoresist mask.

[0006] In another implementation of this disclosure, the ratio of the exposure dose of the edge region to the exposure dose of the center region is between 2:1 and 2.2:1.

[0007] In another implementation of this disclosure, the exposure dose of the edge region is 300-420 mJ / cm². 2 .

[0008] In another implementation of this disclosure, the exposure dose in the central region is 150-190 mJ / cm². 2 .

[0009] In another implementation of this disclosure, the edge region is an annular region 0.5 mm to 1.0 mm from the outer edge of the wafer.

[0010] In another implementation of this disclosure, the thickness of the photoresist is 3.5 μm-4.5 μm.

[0011] In another implementation of this disclosure, the thickness of the metal thin film is less than the thickness of the photoresist.

[0012] In another implementation of this disclosure, the metal thin film is at least one of Cr, Al, Ti, Pt, Au, Ag, and TiW films.

[0013] In another implementation of this disclosure, the removal of the metal thin film located on the surface of the photoresist mask includes: An adhesive blue film is attached to the surface of the wafer to bond the blue film to the metal film on the photoresist surface; the blue film is then peeled off to detach the metal film on the photoresist mask surface from the photoresist mask.

[0014] In another implementation of this disclosure, the removal of the metal film located on the surface of the photoresist mask and the photoresist mask includes: After removing the metal film from the photoresist surface, acetone or N2 is used. Methylpyrrolidone is used to separate the photoresist mask from the surface of the wafer.

[0015] The beneficial effects of the technical solutions provided in this disclosure are: When patterning the surface of a wafer using the patterning method provided in this disclosure, a layer of negative photoresist can be first deposited on the wafer surface. Then, the negative photoresist is exposed, with the exposure dose at the edge region being greater than that at the center region. This allows the negative photoresist at the wafer edge to become thoroughly and deeply cross-linked and cured, making the photoresist layer in that region denser, harder, and more resistant to physical bombardment. Subsequently, when a metal thin film is formed on the wafer surface and the photoresist mask under the cover of the photoresist mask, the formed metal thin film is difficult to penetrate the surface at the wafer edge because the dense photoresist layer can more effectively prevent metal atoms from penetrating from weak points, greatly improving the resistance to metal intrusion.

[0016] Because the edges of the wafer are completely covered by the cured adhesive layer, gold removal is cleaner. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a graphical method provided in an embodiment of this disclosure; Figure 2 This is a flowchart of another graphical method provided in this embodiment of the disclosure; Figure 3 This is a schematic diagram of edge exposure; Figure 4 A schematic diagram of step-through exposure for a wafer.

[0019] The symbols in the diagram represent the following meanings: 100, wafer; 101, edge region; 200, lens. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0021] This disclosure provides a graphical method, such as... Figure 1 As shown, the graphical methods include: S101: A negative photoresist is applied to the surface of the wafer.

[0022] S102: Expose the photoresist.

[0023] The exposure dose at the edge of the photoresist is greater than that at the center.

[0024] S103: Develop the wafer to form a photoresist mask.

[0025] S104: A metal thin film is formed on the surface of the wafer and the surface of the photoresist mask under the cover of the photoresist mask.

[0026] S105: Remove the metal film and photoresist mask located on the surface of the photoresist mask.

[0027] When patterning the surface of a wafer using the patterning method provided in this embodiment, a layer of negative photoresist can be first deposited on the wafer surface. Then, the negative photoresist is exposed, with the exposure dose at the edge region being greater than that at the center region. This allows the negative photoresist at the wafer edge to become thoroughly and deeply cross-linked and cured, making the photoresist layer in that area denser, harder, and more resistant to physical bombardment. Subsequently, when a metal thin film is formed on the wafer surface and the photoresist mask under the cover of the photoresist mask, the formed metal thin film is less likely to invade the surface at the wafer edge because the dense photoresist layer can more effectively prevent metal atoms from penetrating from weak points, greatly improving the resistance to metal intrusion.

[0028] Because the edges of the wafer are completely covered by the cured adhesive layer, gold removal is cleaner.

[0029] This disclosure also provides another graphical method, such as... Figure 2 As shown, the graphical methods include: S201: Spin-coating negative photoresist onto the surface of the wafer.

[0030] To spin-coat negative photoresist onto a wafer surface, the wafer must first undergo pretreatment.

[0031] The wafer is cleaned and dehydrated and baked to remove moisture. If necessary, an adhesion promoter is applied to enhance adhesion. During spin coating, the wafer is first fixed on a vacuum chuck. After dispensing the photoresist, it is rotated at low speed to spread the photoresist evenly on the wafer. Then, it is rotated at high speed (usually 2000-5000 rpm) to throw off the excess photoresist. The uniform, thin, negative photoresist layer is formed by relying on the balance between centrifugal force and surface tension.

[0032] After spin coating, the negative photoresist must be soft-baked immediately (baked on a hot plate at 90-120℃ for 1-2 minutes) to evaporate the solvent in the negative photoresist and change the negative photoresist film from liquid to solid.

[0033] Negative photoresists can include photocrosslinking type and photopolymerization type.

[0034] Common photocrosslinking negative photoresists include cyclized rubber systems (such as polyisoprene and diazid compound systems) and polycinnamate systems. These photoresists undergo a crosslinking reaction after exposure to form an insoluble network structure.

[0035] Photopolymerizable negative photoresist can be SU-8, which is an epoxy resin-based negative photoresist that can be processed into high aspect ratio structures with a thickness of hundreds of micrometers and a width of tens of micrometers under near-ultraviolet light, and has excellent mechanical and chemical stability.

[0036] In this embodiment, the negative photoresist is a photocrosslinked negative photoresist. The thickness of the photoresist is 3.5 μm-4.5 μm.

[0037] This thickness ensures that during physical vapor deposition (PVD), the thickness of the deposited metal film (usually silver, gold, etc., with a thickness of about 0.5-2 μm) is significantly less than the thickness of the negative photoresist, thereby preventing the metal from completely filling or laterally connecting the mask window of the negative photoresist and providing a channel for stripping the negative photoresist.

[0038] S202: Edge exposure of the photoresist.

[0039] Edge exposure is performed after the negative photoresist is soft-baked.

[0040] Wafer Edge Exposure (WEE) is a process that exposes the annular area at the outer edge of a wafer.

[0041] No photomask is needed during exposure. The wafer rotates at a constant speed, and the ultraviolet light beam located above the wafer irradiates the photoresist near the outer edge of the wafer during one rotation, thus achieving exposure.

[0042] The wafer rotation speed can range from 300 to 2000 revolutions per minute (rpm), depending on the type of light source and process requirements. Given a fixed intensity of ultraviolet light, the wafer rotation speed directly determines the exposure time. The slower the rotation speed, the longer a point on the edge is irradiated, resulting in a higher cumulative exposure dose. Therefore, the exposure dose can be controlled by adjusting the rotation speed.

[0043] Figure 3 As shown, during edge exposure, the wafer is transported to a dedicated edge exposure module or integrated lithography machine, where a robotic arm holds it in place on a rotating chuck. Ultraviolet light is focused through lens 200 into a fixed small spot (or a very fine slit), which is aligned with the edge region of the wafer, i.e., the edge region of the photoresist. The wafer is then held in place on the rotating chuck and rotated at high speed, with each edge region sequentially passing through the irradiation area of ​​this small spot, thus achieving exposure.

[0044] The exposure dose during edge exposure needs to be set according to process requirements. The exposure dose equals the light intensity multiplied by the exposure time. The exposure dose is the total energy received per unit area of ​​the photoresist. Too low a dose will lead to incomplete chemical reaction (pattern defects), while too high a dose will lead to over-reaction (pattern distortion).

[0045] After exposure, the negative photoresist around the edge undergoes cross-linking and solidification, forming a dense protective ring that will not dissolve in the subsequent developer.

[0046] In this embodiment, the edge region is an annular region 101 located 0.5mm-1.0mm from the physical edge of the wafer 100.

[0047] In other words, edge exposure selectively exposes a ring-shaped area 0.5mm-1.0mm from the physical edge of the wafer.

[0048] This allows for the quantization of the wafer's edge region. During operation, the equipment generates a ring-shaped ultraviolet light band corresponding to this width through an optical system, selectively exposing this specific ring at the outermost edge of the wafer without affecting the effective chip area inside.

[0049] S203: After edge exposure, expose the central area of ​​the photoresist.

[0050] In this embodiment, the exposure dose in the central region is less than that in the edge region.

[0051] Conventional edge regions require only a lower exposure dose (e.g., less than the exposure dose in step-through exposure) to achieve basic curing and prevent contamination. In this embodiment, however, the exposure dose in the central region is lower than that in the edge regions. For edge regions with rough edges or where metal intrusion needs to be prevented, the exposure dose is increased. After exposure, the negative photoresist around the edge undergoes cross-linking and curing, forming a dense protective ring that will not dissolve in the subsequent developer. This protects the wafer edge and prevents metal atoms from intruding into the edge regions of the wafer during PVD metal deposition.

[0052] In this embodiment, the exposure dose in the edge region is set to 300-420 mJ / cm. 2 .

[0053] This dose range is significantly higher than the protective dose for exposure in the conventional edge region (typically ≤200 mJ / cm²). 2 The technical purpose is to overcome the scattering effect of the rough surface on the exposure, and to ensure that the photoresist obtains a full, uniform and thorough cross-linking reaction on the entire rough surface, including all the micro-valves, so as to form a dense overall structure.

[0054] Optionally, the ratio of the exposure dose in the edge region to the exposure dose in the center region is between 2:1 and 2.2:1.

[0055] In the above implementation, the ratio of the edge exposure dose in step S202 to the main pattern exposure dose in step S203 is controlled between 2:1 and 2.2:1. This ratio ensures that the photoresist crosslinking density and mechanical strength in the edge region are systematically and significantly higher than those in the center region. Thus, during the gold peeling process, the edge "reinforced sealing ring" can resist tearing as a whole, allowing the metal film covering it to be completely peeled off.

[0056] Optionally, when exposing the central area of ​​the photoresist, a step-through exposure method may be used.

[0057] Stepper exposure uses a stepper machine to expose the main pattern in order to form the pattern of the chip's functional areas.

[0058] Stepper exposure is a process used to transfer fine circuit patterns from a photomask onto a wafer. It works by using ultraviolet light to expose the pattern from the photomask onto a specific area of ​​the wafer surface via a micro-projection lens system. After one "lens" of exposure is completed, the wafer moves to the next position with the stage for another exposure, and this cycle continues until the entire central area of ​​the wafer (the effective area) has been exposed.

[0059] In practice, step-through exposure can expose the entire surface of the wafer during the entire exposure process, meaning the exposure area includes both the edge and central regions mentioned earlier. The central region is the area that will eventually be fabricated into a chip. Therefore, the actual exposure dose for the edge region is the sum of the exposure dose from the step-through exposure and the exposure dose from the edge exposure.

[0060] like Figure 4 As shown, in step-through exposure, the entire surface of the wafer can be pre-divided into multiple non-overlapping exposure areas, for example... Figure 4 The wafer is divided into eight regions, numbered 1 to 8. Then, the wafer is moved to expose each of the eight regions sequentially.

[0061] Unlike edge exposure (WEE), which focuses on the wafer edge, step-through exposure focuses on the pattern quality and resolution of the chip area. Its exposure dosage is usually precisely optimized to ensure that the photoresist forms an ideal profile, thereby ensuring that subsequent PVD metallization and gold stripping processes can proceed smoothly.

[0062] In this embodiment, because step exposure will expose the edge area again, the exposure dose of edge exposure (WEE) in step S202 is not set according to the exposure dose of the edge area, but is less than the exposure dose of the edge area.

[0063] In practice, the exposure dose for edge exposure (WEE) is 150-230 mJ / cm². 2 The exposure dose for step exposure is 150-190 mJ / cm². 2 Correspondingly, the exposure dose in the edge region is 300-420 mJ / cm². 2 The exposure dose in the central area is 150-190 mJ / cm². 2 The ratio of exposure dose for edge exposure to step exposure is between 1:1 and 1.2:1.

[0064] In another example, steps S202 and S203 can be interchanged, with the exposure of the central region performed first, followed by the exposure of the edge regions. This is as long as the two exposures meet the set exposure dose ratio. Alternatively, when exposing the central region of the photoresist, exposure can be performed only on areas other than the edge regions; in this case, the exposure dose during edge exposure is the final exposure dose for the edge regions.

[0065] S204: Baking the wafer.

[0066] After exposure, the negative photoresist is baked. Baking provides energy through heating, allowing these active materials to fully diffuse and catalyze cross-linking, transforming the photoresist in the exposed area from a linear polymer into a three-dimensional network of dense structure, which eventually becomes insoluble in the developer, forming a stable pattern.

[0067] S205: Develop the wafer to form a photoresist mask.

[0068] Next, the negative photoresist is developed to form a photoresist mask with a fine functional pattern at the center and a high-strength reinforcing ring at the periphery.

[0069] S206: A metal thin film is formed on the surface of the wafer and the surface of the photoresist mask under the cover of the photoresist mask.

[0070] Metal thin films can be formed by physical vapor deposition (PVD) coating.

[0071] The PVD coating process is usually carried out in a high vacuum chamber. The basic principle is to vaporize the metal target (such as silver, gold, aluminum, etc.) into atoms or molecules through physical means, and then deposit them onto the wafer surface in a linear motion.

[0072] Commonly used PVD methods include electron beam evaporation and magnetron sputtering. Electron beam evaporation uses a high-energy electron beam to bombard a metal target, causing it to melt and evaporate. It is suitable for metal thin films with high purity requirements. Magnetron sputtering, on the other hand, uses ions generated by glow discharge to bombard a target, causing the target atoms to be sputtered and deposited on the wafer, resulting in better step coverage uniformity.

[0073] During the deposition process, since metal atoms travel in essentially straight lines and the wafer is typically rotated within the cavity to ensure uniformity, metal is deposited simultaneously in the exposed area of ​​the wafer (i.e., within the photoresist window) and on the top surface of the photoresist mask. Therefore, by controlling parameters such as deposition rate and cavity pressure, it is crucial to ensure that the metal film thickness (typically 0.5-2 μm) is significantly less than the photoresist thickness (3.5-4.5 μm). This allows for natural fracture of the metal film within the photoresist mask, preventing the metal from completely covering or connecting the sidewalls of the photoresist mask window, thus creating the necessary conditions for subsequent gold peeling processes.

[0074] The metal thin film is at least one of Cr, Al, Ti, Pt, Au, Ag, and TiW films. In other words, commonly used metals in PVD coating include Cr, Al, Ti, Pt, Au, Ag, and TiW.

[0075] S207: Remove the metal film located on the surface of the photoresist mask.

[0076] In this embodiment, blue tape lift-off is employed. Blue tape lift-off is a process that uses an adhesive blue tape to physically remove unwanted metal films from a wafer. The core operation involves tightly adhering the blue tape to the PVD-coated wafer surface, then mechanically peeling it off. Utilizing the principle that the adhesion between the blue tape and the metal film is greater than the adhesion between the negative photoresist and the metal film, the metal film above the photoresist is peeled off along with the blue tape, leaving only the metal film within the photoresist mask window.

[0077] Blue film stripping for gold has high tolerance for photoresist cross-sections. Compared to methods that rely solely on chemical stripping solutions, blue film stripping for gold does not require the photoresist to have a perfect structure. As long as the metal film can be effectively adhered to by the blue film, physical stripping can be achieved, resulting in a wider process window. Secondly, it is efficient and low-cost. Blue film stripping for gold is fast and suitable for mass production. Moreover, the blue film itself has a low cost and does not require complex chemical stripping solution formulations and equipment.

[0078] Optionally, step S207 can be implemented in the following manner: 2071: A sticky blue film is attached to the surface of the wafer, so that the blue film adheres to the metal film on the surface of the photoresist.

[0079] At the start of the operation, a special blue film is first applied to the coated wafer surface, with the adhesive side of the blue film in direct contact with the metal film on the wafer. Then, the equipment uses pressure rollers to repeatedly roll and press the non-adhesive side of the blue film. This step ensures a tight, bubble-free bond between the blue film and the metal film, and applies uniform pressure. The quality of this bonding directly affects the subsequent gold removal process; uneven pressure may result in incomplete removal of some areas or damage to the pattern.

[0080] 2072: Peel off the blue film, causing the metal film on the surface of the photoresist mask to detach from the photoresist mask.

[0081] After bonding is complete, a corner of the blue film is lifted using a mechanical device, and the excess metal film is "adheded" and separated from the wafer by the high adhesion of the blue film itself. This process removes the metal film on top of the photoresist mask along with the blue film, leaving only the metal film firmly bonded to the wafer within the photoresist mask window.

[0082] In this embodiment, because the edge area of ​​the photoresist mask has extremely high mechanical strength and integrity, the PVD metal cannot penetrate or embed itself. The stress is uniform during the gold peeling process, and the metal in the entire edge area is completely and cleanly peeled off in one go without any residue.

[0083] S208: Remove the photoresist mask.

[0084] After removing the metal film from the photoresist surface, acetone or N2O is used. Methylpyrrolidone allows the photoresist mask to be separated from the surface of the wafer.

[0085] During the process, the wafer with the blue film removed and gold removed is first immersed in acetone or a special stripping solution (such as hydroxylamine-based EKC265) to swell, soften, and even dissolve the residual photoresist. To enhance the effect, ultrasonic or megasonic stirring is often used in the solution. The cavitation effect of ultrasound can generate microscopic impact forces, physically peeling the stubborn photoresist layer from the wafer surface. For nanoscale fine structures or severely cross-linked photoresist layers, a multi-step immersion strategy (such as a gradient treatment of room temperature → heated acetone) can also be used to completely remove residual photoresist.

[0086] After chemical soaking, a rigorous post-cleaning and drying process is required. The wafer is thoroughly rinsed sequentially with isopropanol (IPA) and deionized water (DIW) to remove residual chemical reagents and metal ion contaminants. Finally, it is dried at high speed or with nitrogen to ensure that no water stains remain on the wafer surface. This process completely removes the photoresist, exposing a clean wafer surface where the previously covered areas are exposed. The deposited metal pattern remains intact within the photoresist mask window, ultimately forming a fully patterned chip.

[0087] To fully illustrate the non-obviousness and unexpected technical effects of this disclosure, the following comparative examples are provided. All examples were carried out under the same conditions on 4-inch LED epitaxial wafers coated with 4.0 μm negative adhesive.

[0088] Comparative Example 1 (Conventional Process): No edge exposure is performed; only step exposure is applied to the epitaxial wafer. The resist thickness is 4.0 μm, and the width of the edge region is 0.8 mm. In this case, the exposure dose ratio of the edge region to the center region is 1.

[0089] Results: Numerous filamentous residues were observed at the chip edges, resulting in a yield loss of approximately 5%. This indicates that conventional edge exposure cannot form an effective seal at the rough edges of the epitaxial wafer.

[0090] Comparative Example 2 (High Dose for Edge Exposure): Attempting to significantly increase the exposure dose for edge exposure (exposure dose of 300 mJ / cm² for edge exposure). 2 Stepped exposure dose 180mJ / cm 2 (Dosage ratio ≈ 1.67). Adhesive thickness 4.0 μm, edge region width 0.8 mm.

[0091] Results: After gold removal, the edge residue of the epitaxial wafer was reduced, but the yield loss was still 3%. Analysis: Overexposure to the edge region led to excessively high cross-linking density of the edge adhesive layer, increasing brittleness and internal stress. During PVD coating or gold removal, microcracks formed in the adhesive layer itself, becoming new defect sources. Furthermore, the over-cross-linked adhesive layer was difficult to remove. This further proves that higher exposure doses in the edge region are not always better; rather, there exists an optimal window.

[0092] Comparative Example 3 (Insufficient Exposure Dose at the Edge): A slightly higher but still insufficient WEE dose (120 mJ / cm² for edge exposure) was used. 2 Stepped exposure dose 180mJ / cm 2 The exposure dose ratio of edge exposure to step exposure is approximately 0.67, and the exposure dose ratio of the edge region to the center region is approximately 1.67. The adhesive thickness is 4.0 μm, and the width of the edge region is 0.8 mm.

[0093] Results: A small amount of metallic filament residue was still observed at the chip edge, resulting in a yield loss of approximately 2%. This indicates that insufficient dosage leads to inadequate reinforcement and fails to completely seal all rough grooves.

[0094] Comparative Example 4: Using the process parameter window protected by the embodiments of this disclosure (resin thickness 4.0 μm, edge width 0.8 mm, edge exposure dose 200 mJ / cm²). 2 Stepped exposure dose 180mJ / cm 2The dose ratio is approximately 1.11, at which point the ratio of exposure dose in the edge region to that in the center region is approximately 2.11.

[0095] Results: Edge metal residue was completely eliminated, and yield loss was reduced to less than 1% (mainly due to non-edge factors). Microscopic observation showed that the edge metal was completely removed, and the interface was clean.

[0096] The above comparison demonstrates that, only within the specific parameter window defined in the embodiments of this disclosure, particularly the exposure dose at the edge exposure (150-230 mJ / cm²), 2 ) and the exposure dose of step exposure (150-190mJ / cm) 2 The ratio of the exposure dose of the edge region to the exposure dose of the center region must be between 1.1:1 and -1.2:1 to achieve the "enhanced sealing" effect while avoiding the adhesive layer from becoming too brittle.

[0097] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” etc., are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0098] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A graphical method, characterized in that, The graphical method includes: A negative photoresist is applied to the surface of the wafer; The photoresist is exposed, and the exposure dose of the edge region of the photoresist is greater than the exposure dose of the center region of the photoresist. The wafer is developed so that the photoresist forms a photoresist mask; Under the cover of the photoresist mask, a metal thin film is formed on the surface of the wafer and the surface of the photoresist mask; Remove the metal film and the photoresist mask located on the surface of the photoresist mask.

2. The graphical method according to claim 1, characterized in that, The ratio of the exposure dose of the edge region to the exposure dose of the center region is between 2:1 and 2.2:

1.

3. The graphical method according to claim 1, characterized in that, The exposure dose in the edge region is 300-420 mJ / cm². 2 .

4. The graphical method according to claim 1, characterized in that, The exposure dose in the central region is 150-190 mJ / cm². 2 .

5. The graphical method according to claim 1, characterized in that, The edge region is a ring-shaped area 0.5mm-1.0mm from the outer edge of the wafer.

6. The graphical method according to claim 1, characterized in that, The thickness of the photoresist is 3.5μm-4.5μm.

7. The graphical method according to claim 1, characterized in that, The thickness of the metal film is less than the thickness of the photoresist.

8. The graphical method according to claim 1, characterized in that, The metal thin film is at least one of Cr, Al, Ti, Pt, Au, Ag, and TiW films.

9. The graphical method according to claim 1, characterized in that, The removal of the metal film located on the surface of the photoresist mask includes: An adhesive blue film is attached to the surface of the wafer to bond the blue film to the metal film on the surface of the photoresist. Peel off the blue film to detach the metal film on the surface of the photoresist mask from the photoresist mask.

10. The graphical method according to claim 1, characterized in that, The removal of the metal film located on the surface of the photoresist mask and the photoresist mask includes: After removing the metal film from the photoresist surface, acetone or N2 is used. Methylpyrrolidone is used to separate the photoresist mask from the surface of the wafer.

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