Manufacturing method for forming thick photoresist layer on wafer

Abstract

The invention discloses a manufacturing method for forming a thick photoresist layer on a wafer, and the method comprises the steps: 1, providing a first mold with a film forming groove, and enabling one end of the film forming groove to be provided with an opening which is matched with a to-be-glued region on the wafer in shape and size; step 2, spraying a photoresist solvent on the groove bottom and the groove wall of the film forming groove to form a photoresist solvent layer; step 3, closing the opening of the film forming groove through the pattern surface of the wafer to form a closed forming cavity, adding a photoresist with a preset mass into the forming cavity, and forming a thick photoresist layer with a preset thickness in contact with the pattern surface of the wafer in the forming cavity; and step 4, separating the first mold from the wafer so as to enable the thick photoresist layer to be adhered to the wafer. Compared with the prior art, the invention has the advantages of raw material saving, low cost, environmental protection and reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more particularly to a method for forming a thick photoresist layer on a wafer. Background Technology

[0002] Interconnect technologies in advanced packaging primarily employ electroplating to form specific solder metal structures, such as copper pillars in flip chips and C4 (Controlled Collapse Chip Connection) solder balls in 2.5D packages. These structures have a height of at least 80 μm, thus requiring photoresist films with a thickness greater than 90 μm. Therefore, high-viscosity (cp>2000) photoresist must be used for thick photomasks to meet the electroplating height requirements.

[0003] Currently, the commonly used photoresist coating method in the industry involves spraying photoresist at the center of the wafer followed by high-speed spin coating to uniformly cover the wafer surface, and then using high-speed rotation to achieve the target thickness. However, for high-viscosity photoresists, this method has the following problems: To ensure complete coverage of the positive wafer with photoresist and prevent defects such as insufficient or missing photoresist, the amount of photoresist sprayed is typically far greater than the actual amount required for film formation. Based on a 300mm wafer and a film thickness of 50μm, the volume of photoresist remaining on the wafer surface is approximately 3.5ml. However, in actual process setups, the amount of photoresist sprayed is at least four times that (spray thickness > 15ml). This means that most of the photoresist is ejected from the wafer, resulting in significant waste and increased costs. After the excess photoresist is ejected, some accumulates on the inner wall of the deposition tank, while some is removed through the bottom exhaust system. However, after a period of operation, residual photoresist continues to accumulate on the inner wall, increasing cleaning difficulty, and the exhaust ducts are at risk of clogging.

[0004] Therefore, there is an urgent need for a wafer-thick photoresist coating method that can solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for forming a thick photoresist layer on a wafer, which saves raw materials, has low cost, and is environmentally friendly and reliable.

[0006] To achieve the above objectives, the present invention provides a method for forming a thick photoresist layer on a wafer, comprising: Step 1, providing a first mold having a film-forming groove, one end of the film-forming groove having an opening and matching the shape and size of the area to be coated with photoresist on the wafer; Step 2, spraying photoresist solvent onto the bottom and walls of the film-forming groove to form a photoresist solvent layer; Step 3, closing the opening of the film-forming groove through the patterned surface of the wafer to form a closed molding cavity, adding a predetermined mass of photoresist into the molding cavity, and forming a thick photoresist layer of predetermined thickness in contact with the patterned surface of the wafer within the molding cavity; Step 4, detaching the first mold relative to the wafer and adhering the thick photoresist layer to the wafer.

[0007] Preferably, a photoresist injection channel is formed on the inner wall of the film deposition tank. Step 3 specifically includes: first, sealing the opening of the film deposition tank through the patterned surface of the wafer to form a closed molding cavity; then, injecting a predetermined mass of photoresist into the molding cavity through the injection channel; and then allowing the predetermined mass of photoresist to contact the patterned surface of the wafer within the molding cavity to form a thick photoresist layer of predetermined thickness on the patterned surface of the wafer. Compared with the prior art, the present invention directly injects photoresist into the film deposition tank, eliminating the need for high-speed spin coating and pre-wetting. Because there is no high-speed rotation process, photoresist does not accumulate at the wafer edge, and the subsequent edge washing process can be reduced in time, saving solvent usage.

[0008] Preferably, it also includes a second mold with a vacuum chuck, the second mold and the first mold being matched together. In step 3: the vacuum chuck on the second mold is used to adsorb and position the wafer, and the wafer is aligned and pressed together with the film forming groove of the first mold to complete the mold closing of the second mold and the first mold, so that the patterned surface closes the opening of the film forming groove.

[0009] Preferably, in step 4, before the first mold is detached from the wafer, the patterned surface of the wafer is facing upwards, and the first mold is kept covering the wafer; the first mold is vertically raised so that it detaches from the wafer, and the thick photoresist layer remains on the patterned surface of the wafer under the action of gravity and adhesive force.

[0010] Preferably, the first mold has a through-hole at the bottom of the film forming tank; in step 4, while the first mold is being separated from the wafer, air is blown into the film forming tank through the through-hole to accelerate the separation of the first mold and the wafer by air pressure-assisted external force, ensuring successful demolding.

[0011] Specifically, the contact angle between the wall of the demolding hole and the photoresist material is greater than 150 degrees.

[0012] Preferably, the diameter of the film-forming trench is smaller than the diameter of the wafer, and the thick photoresist layer covers the middle region of the patterned surface of the wafer but does not cover the edge of the patterned surface; or, the diameter of the film-forming trench is equal to the diameter of the wafer, and the thick photoresist layer completely covers the patterned surface of the wafer.

[0013] Preferably, in step 4, before detaching the first mold from the wafer, the outer wall of the first mold is heated to soften the thick photoresist layer inside the first mold.

[0014] Preferably, the first mold is further provided with a lifting plate in the film-forming groove, and the top surface of the lifting plate forms the bottom of the film-forming groove. The lifting plate is installed in the film-forming groove in an adjustable position along the depth direction of the film-forming groove to adjust the depth of the film-forming groove.

[0015] Preferably, in step 2, forming a thick photoresist layer of a predetermined thickness on the photoresist solvent layer of the film-forming tank specifically includes: pouring a predetermined mass of photoresist into the film-forming tank and waiting until the photoresist is uniformly distributed on the bottom of the film-forming tank and has a predetermined thickness, so as to form the thick photoresist layer.

[0016] Preferably, the depth of the film-forming groove is a preset thickness. In step 3, when the patterned surface of the wafer is aligned with the groove opening of the film-forming groove, the patterned surface of the wafer and the upper edge of the groove opening of the film-forming groove are located on the same plane. This prevents the edge of the thick photoresist layer from becoming irregular after the wafer enters the film-forming groove, or from being damaged during subsequent demolding.

[0017] Preferably, the method for forming a thick photoresist layer on the wafer further includes step 5, baking the wafer to evaporate the photoresist solvent layer.

[0018] Compared with the prior art, the present invention sets up a first mold with a film forming tank, and then directly adds a preset mass of photoresist into the film forming tank. The preset mass corresponds to the film thickness formed by the photoresist, so that the thick photoresist layer after film formation not only reaches the preset thickness, but also does not generate excess material. This not only saves costs, but also eliminates the need to eject the photoresist from the wafer, making it environmentally friendly and reliable. It will not pollute the equipment or clog the exhaust pipe, and will reduce subsequent equipment maintenance costs. Attached Figure Description

[0019] Figure 1 This is a top view of the first mold of the present invention.

[0020] Figure 2 This is a side cross-sectional view of the first mold of the present invention.

[0021] Figure 3 This is a flowchart of the method for forming a thick photoresist layer on a wafer in Embodiment 1 of the present invention.

[0022] Figure 4 This is a flowchart of the method for forming a thick photoresist layer on a wafer in Embodiment 2 of the present invention.

[0023] Figure 5 This is a flowchart of the method for forming a thick photoresist layer on a wafer in Embodiment 3 of the present invention. Detailed Implementation

[0024] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0025] refer to Figure 3 The present invention discloses a method for forming a thick photoresist layer on a wafer, comprising steps S1 to S4.

[0026] Step S1, a first mold 10 with a film-forming groove 11 is provided.

[0027] refer to Figure 1 and Figure 2 The film-forming groove 11 has an opening at one end and includes a groove bottom and a groove wall that matches the shape and size of the wafer to be coated with adhesive.

[0028] Step S2: Photoresist solvent is sprayed onto the bottom and walls of the film forming tank 11 to form a photoresist solvent layer 20, which is used to prevent the formed thick photoresist layer 21 from adhering to the inner wall of the film forming tank 11.

[0029] Step S3: The opening of the film deposition groove 11 is closed by the patterned surface of the wafer 30 to form a closed molding cavity, and a preset mass of photoresist is added into the molding cavity, and a preset thickness of photoresist layer 21 is formed in the molding cavity, which is in contact with the patterned surface of the wafer 30.

[0030] Photoresist is generally selected from thermosetting photoresist materials such as phenolic resin or polyimide.

[0031] Specifically, refer to Figure 3 A photoresist injection channel 15 is formed on the inner wall of the film deposition tank 11. In step S3, the wafer 30 is aligned with the first mold 11 so that the patterned surface of the wafer 30 is opposite to the position of the film deposition tank 11. First, the opening of the film deposition tank 11 is closed by the patterned surface of the wafer 30 to form a closed molding cavity. Then, a preset mass of photoresist is injected into the molding cavity through the injection channel 15 to form a preset thickness of photoresist layer 21 on the patterned surface of the wafer 30.

[0032] Specifically, step S3 includes: S31, with the groove opening of the film deposition tank 11 facing downwards and the patterned surface of the wafer 30 facing upwards, the wafer 30 is positioned opposite the film deposition tank 11, such that the patterned surface of the wafer 30 and the bottom of the film deposition tank 11 have a preset distance corresponding to the preset thickness, and a molding cavity is formed between the patterned surface of the wafer 30 and the film deposition tank 11; S32, photoresist is injected into the molding cavity through the injection channel 15 to form a thick photoresist layer 21 that fully contacts the patterned surface of the wafer 30 between the bottom of the film deposition tank 11 and the patterned surface of the wafer 30. Preferably, the injection channel 15 is located at the bottom of the film deposition tank 11. The diameter of the injection channel 15 is much larger than that of the demolding hole 12.

[0033] When using a dispensing device to dispense adhesive, the dispensing action is controlled according to the dispensing pressure.

[0034] The preset thickness is 50μm to 120μm.

[0035] Preferably, in order to adjust the thickness of the thick photoresist layer 21, the first mold 10 is further provided with a lifting plate 13 in the film deposition tank 11. The top surface of the lifting plate 13 forms the bottom of the film deposition tank 11. The lifting plate 13 is adjustablely installed in the film deposition tank 11 along the depth direction to adjust the depth of the film deposition tank 11, and ultimately adjust the thickness of the thick photoresist layer 21. Of course, it is not limited to this. In another embodiment, the bottom and wall of the film deposition tank 11 are an integral structure, and there is no need to adjust the depth of the film deposition tank.

[0036] The depth of the film-forming trench 11 corresponds to the thickness of the thick photoresist layer 21. That is, the trench depth of the film-forming trench 11 is a preset thickness. In step 3, when the patterned surface of the wafer 30 is aligned with the opening of the film-forming trench 11, the patterned surface of the wafer 30 and the upper edge of the opening of the film-forming trench 11 are located on the same plane. In this embodiment, the edge of the patterned surface of the wafer 30 directly abuts against the top of the trench wall of the film-forming trench 11.

[0037] Of course, the depth of the film-forming groove 11 can also be greater than the thickness of the thick photoresist layer 21. In this case, the wafer 30 needs to enter the film-forming groove 11 during film formation.

[0038] Preferably, the mold also includes a second mold with a vacuum chuck 14, which matches the first mold 10. In step 3, the vacuum chuck 14 on the second mold is used to adsorb and position the wafer 30, and the wafer 30 is aligned and pressed together with the film forming groove 11 of the first mold to complete the mold closing of the second mold and the first mold, so that the patterned surface closes the opening of the film forming groove 11.

[0039] In this embodiment, since there are no pre-fabricated chip units at the edge of wafer 30, circuit structures such as solder balls, copper pillars, and bumps do not need to be fabricated at the edge. Therefore, the edge of wafer 30 does not need to be coated with photoresist. To further reduce photoresist waste, the size of wafer 30 is larger than the size of the film deposition trench 11. Furthermore, the difference between the diameter of wafer 30 and the diameter of the film deposition trench 11 is greater than 0 and less than a preset value. The film deposition trench 11 does not cover the edge of the patterned surface of wafer 30, so that the edge of the wafer after film deposition is not coated with photoresist. That is, the thick photoresist layer covers the middle area of ​​the patterned surface of the wafer but does not cover the edge of the patterned surface.

[0040] Step S4: The first mold 10 is detached from the wafer 30 so that the thick photoresist layer 21 adheres to the image surface of the wafer.

[0041] refer to Figure 3 Step S4 specifically includes: Positioning the patterned surface of the wafer 30 upwards, with the first mold 10 still covering the wafer 30, and vertically raising the first mold 10 to detach it from the wafer 30. The thick photoresist layer 21 adheres to the wafer 30 under gravity and adhesion. This solution uses gravity and adhesion to detach the thick photoresist layer 21 from the wafer and the first mold 10. Due to the presence of the photoresist solvent layer 20, the adhesion between the thick photoresist layer 21 and the patterned surface of the wafer 30 is much greater than the adhesion between the thick photoresist layer 21 and the film deposition tank 11. When the first mold 10 and the wafer 30 detach, the thick photoresist layer 21 remains intact on the wafer 30 and detaches from the inner wall of the film deposition tank 11.

[0042] In this process, the patterned surface of the wafer 30 is facing upwards, and the first mold 10 is held on the surface of the wafer 30. Then, the first mold 10 is raised vertically, so that the first mold 10 and the wafer 30 are separated, and the thick photoresist layer 21 is retained entirely on the patterned surface of the wafer 30.

[0043] Preferably, to further facilitate demolding, the first mold 10 has a through demolding hole 12 at the bottom of the film forming tank 11. In step S4, while the first mold 10 and the wafer 30 are being separated, air is blown into the film forming tank 11 through the demolding hole 12 to accelerate the separation of the first mold 10 and the wafer 30 under pressure-assisted external force. To prevent photoresist from clogging the demolding hole 12, the contact angle between the hole wall and the photoresist material is greater than 150 degrees. Several demolding holes 12 are evenly distributed at the bottom of the film forming tank 11.

[0044] The diameter of the release hole 12 is 50um~500um. Because the diameter of the release hole 12 is small, gas can pass through, but liquid photoresist cannot. Therefore, during the potting process, the photoresist cannot flow out from the bottom of the film deposition tank 11. When demolding is required, gas can enter the film deposition tank 11 through the release hole 12 to assist the thick photoresist layer 21 in separating from the bottom and walls of the film deposition tank 11.

[0045] To facilitate demolding, in step S4, before the first mold 10 is detached from the wafer 30, the outer wall of the first mold 10 is heated to soften the thick photoresist layer 21 inside the first mold 10.

[0046] In a preferred embodiment, step S5 is also included, which involves baking the wafer 30 to evaporate the photoresist solvent layer 20 and smooth the surface of the thick photoresist layer 21. Finally, edge cleaning is performed to complete the coating of the thick photoresist layer 21 with a preset thickness on the wafer surface.

[0047] Example 2: refer to Figure 4 Unlike Embodiment 1, in Embodiment 2, the diameter of the film-forming groove 11 is equal to the diameter of the wafer 30, and the thick photoresist layer 21 completely covers the patterned surface of the wafer 30.

[0048] Example 3: refer to Figure 5 Unlike Embodiment 1, in Embodiment 3, in step S31, the opening of the film deposition tank 11 is facing upwards, and the patterned surface of the wafer 30 is facing downwards, so that the wafer 30 is aligned with the film deposition tank 11. Specifically, a vacuum chuck is used to hold the wafer 30 with its patterned surface facing downwards, and the first mold 10 is placed below the wafer 30 with its centers aligned. In this case, step S4 specifically includes: S41, rotating the wafer 30 180 degrees so that the wafer 30 and the first mold 10 are inverted, with the patterned surface of the wafer 30 facing upwards, and the first mold 10 remaining on top of the wafer 30; S42, vertically raising the first mold 10 so that it detaches from the wafer 30, and the thick photoresist layer 21 adheres to the wafer 30 under gravity and adhesion. This solution uses gravity and adhesion to detach the thick photoresist layer 21 and the wafer from the first mold 10.

[0049] Due to the presence of the photoresist solvent layer 20, the adhesion between the thick photoresist layer 21 and the patterned surface of the wafer 30 is much greater than the adhesion between the thick photoresist layer 21 and the film deposition tank 11. When the first mold 10 and the wafer 30 are separated, the thick photoresist layer 21 remains intact on the wafer 30 and separates from the inner wall of the film deposition tank 11.

[0050] On the one hand, existing technologies, particularly traditional coating methods, not only generate excessive excess resist, but also fail to achieve the required thickness for thick photoresist layers in a single center-spray coating process, especially for electroplated copper pillars / C4 > 80μm. Therefore, a two-stage spin coating process is necessary to achieve the target film thickness, resulting in higher costs. On the other hand, center-spray coating is difficult to control for the uniformity of high-viscosity photoresist film thickness. Furthermore, the higher viscosity of thicker resist increases the difficulty of spraying the resist to the wafer edge, further affecting the uniformity of resist diffusion. This leads to significant differences in film thickness between the center and the edges, making process adjustments more difficult and resulting in poor process stability. The large differences in linewidth after development affect the coplanarity of the metal after electroplating. Moreover, because center-spray coating uses high-speed spin coating, the resist diffuses as the wafer rotates, easily trapping air and forming bubbles, which affects film quality and yield. This phenomenon is even more frequent with high-viscosity photoresists.

[0051] Compared with existing technologies, on the one hand, the present invention sets up a first mold 10 with a film-forming groove 11, and then directly adds a preset mass of photoresist into the film-forming groove 11. This preset mass corresponds to the film thickness formed by the photoresist, so that the thick photoresist layer 21 after film formation not only reaches the preset thickness, but also does not generate excess material. This not only saves costs, but also eliminates the need to throw the photoresist outside the wafer 30, making it environmentally friendly and reliable, and preventing equipment pollution and ventilation duct blockage. On the other hand, the present invention forms a molding cavity between the film-forming groove 11 and the patterned surface of the wafer 30. The photoresist is directly poured into the film-forming groove 11 by a pouring method, which not only simplifies the process and reduces costs, but also ensures uniform photoresist thickness, good product coplanarity, and high yield.

[0052] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the scope of the present invention are still within the scope of the present invention.

Claims

1. A method for forming a thick photoresist layer on a wafer, characterized in that: include: Step 1: Provide a first mold with a film-forming groove, one end of which has an opening and matches the shape and size of the area to be coated on the wafer; Step 2: Spray photoresist solvent onto the bottom and walls of the film-forming tank to form a photoresist solvent layer; Step 3: The opening of the film deposition trench is closed by the patterned surface of the wafer to form a closed molding cavity. A preset mass of photoresist is added to the molding cavity, and a thick photoresist layer of preset thickness is formed in the molding cavity, which is in contact with the patterned surface of the wafer. Step 4: Decouple the first mold from the wafer and allow the thick photoresist layer to adhere to the wafer.

2. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The inner wall of the film deposition tank is formed with a photoresist injection channel. Step 3 specifically includes: first, sealing the opening of the film deposition tank through the patterned surface of the wafer to form a closed molding cavity; then, injecting a preset mass of photoresist into the molding cavity through the injection channel; and then making the preset mass of photoresist contact the patterned surface of the wafer in the molding cavity to form a thick photoresist layer of a preset thickness on the patterned surface of the wafer.

3. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: It also includes a second mold with a vacuum suction cup, which matches the first mold. In step 3, the vacuum suction cup on the second mold is used to adsorb and position the wafer, and the wafer is aligned and pressed together with the film forming groove of the first mold to complete the mold closing of the second mold and the first mold, so that the patterned surface closes the opening of the film forming groove.

4. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: In step 4, before the first mold is detached from the wafer, the patterned surface of the wafer is facing upwards, and the first mold is kept covering the wafer; the first mold is vertically raised so that it detaches from the wafer, and the thick photoresist layer remains on the patterned surface of the wafer under the action of gravity and adhesive force.

5. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The first mold has a through-hole at the bottom of the film forming tank; in step 4, while the first mold is being separated from the wafer, air is blown into the film forming tank through the through-hole to accelerate the separation of the first mold and the wafer by air pressure-assisted external force.

6. The method for forming a thick photoresist layer on a wafer as described in claim 5, characterized in that: The contact angle between the wall of the demolding hole and the photoresist material is greater than 150 degrees.

7. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The diameter of the film-forming trench is smaller than the diameter of the wafer, and the thick photoresist layer covers the middle region of the patterned surface of the wafer but does not cover the edges of the patterned surface; or, The diameter of the film-forming groove is equal to the diameter of the wafer, and the thick photoresist layer completely covers the patterned surface of the wafer.

8. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: In step 4, before the first mold is detached from the wafer, the outer wall of the first mold is heated to soften the thick photoresist layer inside the first mold.

9. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The first mold is further provided with a lifting plate in the film forming groove, and the top surface of the lifting plate forms the bottom of the film forming groove. The lifting plate is installed in the film forming groove in an adjustable position along the depth direction of the film forming groove to adjust the depth of the film forming groove.

10. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The depth of the film-forming groove is a preset thickness. In step 3, when the patterned surface of the wafer is aligned with the groove opening of the film-forming groove, the patterned surface of the wafer and the upper edge of the groove opening of the film-forming groove are located on the same plane.

11. The method for forming a thick photoresist layer on a wafer as described in claim 1, characterized in that: The process also includes step 5, baking the wafer to evaporate the photoresist solvent layer.

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