Gluing method of thick film photoresist for advanced packaging

Abstract

The invention discloses a method for coating a thick film photoresist for advanced packaging, which comprises the following steps of: continuously carrying out first time and second time of photoresist spin coating on a wafer, and enabling the first time length of the first time of photoresist spin coating to be less than the second time length of the second time of photoresist spin coating, therefore, the first adhesive layer and the second adhesive layer which are formed by two times of spin coating can be completely fused to obtain a photoresist layer with the thickness of more than 60 microns, and then the photoresist layer is subjected to one-time soft baking. Therefore, the first adhesive layer and the second adhesive layer can be completely fused, so that the uniformity of the obtained photoresist layer is better; the baking time of the first adhesive layer and the baking time of the second adhesive layer are the same, so that the volatilization degree of an internal solvent is consistent, the uniformity of a columnar opening formed after subsequent exposure and development is better, and the angle of the side wall is more vertical; and moreover, the whole process flow is more simplified, the processing time is greatly reduced, and the production efficiency of the machine is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for coating a thick film photoresist for advanced packaging. Background Art

[0002] In the interconnection technology of advanced packaging, electroplating is mainly used to form specific welding metal structures, such as copper pillars in flip chips and C4 (Controlled Collapse Chip Connection) solder balls in 2.5D packaging. Their height is usually greater than 70 μm. Therefore, a photoresist with a high viscosity (>4000 cp) must be used for thick film masking to form the required metal structure during electroplating.

[0003] However, among several commonly used high-viscosity photoresists in the industry currently, the maximum thickness that can be achieved in one coating is only about 60 μm, which cannot meet the requirements of electroplating height in advanced packaging. In view of the foregoing situation, there are mainly the following solutions currently:

[0004] 1. Adopt one-time photoresist coating, and the final film thickness is 50 - 60 μm, which is lower than the actual electroplating height. During electroplating, tin-silver will be higher than the photoresist film, forming a structure similar to a mushroom head, and then forming solder balls after reflow. The disadvantage of this method is that there are likely to be large differences between individual mushroom head structures, resulting in a low yield of solder balls after reflow. At the same time, the photoresist adheres to the lower part of the mushroom head structure and is difficult to remove, easily generating photoresist residues, which in turn affects the reflow quality.

[0005] 2. Adopt two-time photoresist coating, that is, first perform the first drop coating, spin coating, and soft baking to form the first layer of photoresist film; then perform the second drop coating, spin coating, and soft baking on its surface to finally form a photoresist film with a thickness higher than the electroplating thickness. The disadvantages of this method are: (1) The process flow of two-time spin coating + two-time baking is complex, the process time is long, and the machine productivity is low; (2) After the first layer of glue is relatively cured by soft baking and then the second layer of glue is spin-coated, the uniformity difference of the first layer of glue is accumulated at this time, resulting in poor overall uniformity; (3) The baking time of the first layer of glue is twice that of the second layer of glue, that is, the first layer of glue has undergone two bakings, resulting in different degrees of solvent volatilization in the two layers of glue, making the diameter deviation of the upper and lower parts of the columnar opening formed after subsequent development larger and the sidewall inclination angle increase, affecting the electroplating structure.

[0006] 3. Use a dry film instead of a photoresist, that is, directly attach a dry film with a specific thickness (up to 200 μm at most) to the surface of the wafer, and then complete the exposure and development processes. The disadvantages of this method are: (1) Bubbles are likely to be generated during the film pasting process, the rework frequency is relatively high, and the cost increases; (2) The dry film is difficult to remove completely during degluing, easily generating residues, affecting the product yield.

[0007] Therefore, it is necessary to provide an improved method for coating a thick film photoresist for advanced packaging to solve the above technical problems. SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide a method for coating a thick film photoresist for advanced packaging, so that a photoresist film meeting the thickness requirement can be obtained in a single process in a coating unit, greatly reducing the process time and having better film forming uniformity.

[0009] To achieve the above object, the technical solution of the present invention is: to provide a method for coating a thick film photoresist for advanced packaging, which includes the following steps:

[0010] (1) Provide a wafer, place the wafer on a positioning carrier, rotate the positioning carrier and spray a photoresist solvent on the wafer to perform a surface wetting treatment on the wafer;

[0011] (2) Perform a first spin coating of the photoresist on the surface of the wafer to obtain a first glue layer. Wherein, after the photoresist reaches the edge of the wafer, continue to rotate for a first duration to flatten the photoresist on the surface of the wafer to obtain the first glue layer;

[0012] (3) Perform a second spin coating of the photoresist on the surface of the wafer, and fully fuse the second glue layer with the first glue layer to obtain a photoresist layer with a target thickness; wherein, after the photoresist reaches the edge of the wafer, continue to rotate for a second duration to fuse the photoresist, and the second duration is greater than the first duration;

[0013] (4) Perform soft baking on the photoresist layer to obtain a photoresist film.

[0014] Preferably, in the method for coating a thick film photoresist for advanced packaging, the step (2) specifically includes the following steps:

[0015] (21) The positioning carrier is lowered to a first rotation speed, and a first drop of glue is performed at the center of the wafer, and the glue dropping speed is 0.2 - 0.4 ml / s, and the glue dropping dose is 20 - 30 ml;

[0016] (22) The positioning carrier is raised from the first rotation speed to a second rotation speed, and uniformly rotates for a first diffusion duration at the second rotation speed to diffuse the photoresist to the edge of the wafer;

[0017] (23) The positioning carrier is lowered from the second rotation speed to a third rotation speed and uniformly rotates for the first duration to flatten the photoresist, completing the first spin coating of the photoresist to obtain the first glue layer; wherein, the third rotation speed is lower than the second rotation speed and higher than the first rotation speed.

[0018] Preferably, in the method for coating a thick film photoresist for advanced packaging of the present application, in step (22), when the positioning carrier is increased from the first rotation speed to the second rotation speed, the EBR nozzle is simultaneously moved to a first distance inward from the edge of the wafer, and a photoresist solvent is sprayed onto the surface of the wafer to accelerate the diffusion of the photoresist to the edge of the wafer.

[0019] Preferably, in the method for coating a thick film photoresist for advanced packaging, the first distance is 5 mm to 8 mm inward from the edge of the wafer, and the first diffusion time is 15 to 20 s.

[0020] Preferably, in the method for coating a thick film photoresist for advanced packaging, step (3) specifically includes the following steps:

[0021] (31) The positioning carrier is lowered again to the first rotation speed, and a second drop of photoresist is performed at the center of the wafer, with a dropping speed of 0.2 to 0.4 ml / s and a dropping dose of 20 to 30 ml;

[0022] (32) The positioning carrier is increased from the first rotation speed to the second rotation speed, and rotates at a constant speed for a second diffusion time at the second rotation speed so that the photoresist diffuses to the edge of the wafer to obtain a second photoresist layer;

[0023] (33) The positioning carrier is lowered from the second rotation speed to the third rotation speed and rotates at a constant speed for a second time so that the photoresist reaches the target thickness, thereby obtaining a photoresist layer and completing the second spin coating of the photoresist; wherein, the third rotation speed is lower than the second rotation speed and higher than the first rotation speed;

[0024] (34) The positioning carrier is lowered from the third rotation speed to the fourth rotation speed, and the EBR nozzle is moved to a second distance inward from the edge of the wafer, and a photoresist solvent is sprayed onto the edge of the wafer and rotated continuously for a third time to reduce the thickness of the photoresist accumulation at the edge of the wafer; wherein, the fourth rotation speed is higher than the first rotation speed.

[0025] Preferably, in the method for coating a thick film photoresist for advanced packaging, step (3) further includes the following steps:

[0026] (35) The positioning carrier is increased from the fourth rotation speed to the fifth rotation speed, and rotates continuously for a fourth time to spin off the excess photoresist solvent, and then the speed is reduced to the sixth rotation speed; wherein, the fifth rotation speed is the maximum rotation speed among all rotation speeds, and the sixth rotation speed is the minimum rotation speed among all rotation speeds.

[0027] Preferably, in the method for coating a thick film photoresist for advanced packaging, the second diffusion time is 25 to 30 s, and the second distance is 1 mm to 2 mm inward from the edge of the wafer.

[0028] Preferably, in the method for coating the thick film photoresist for advanced packaging, the first duration is 20 - 30 s, and the second duration is 100 - 150 s.

[0029] Preferably, in the method for coating the thick film photoresist for advanced packaging, the first rotation speed is 100 - 200 rpm, the second rotation speed is reduced to 1000 - 1200 rpm, and the third rotation speed is 600 - 800 rpm.

[0030] Preferably, in the method for coating the thick film photoresist for advanced packaging, the fourth rotation speed is 300 - 400 rpm, the fifth rotation speed is 1300 - 1500 rpm, and the sixth rotation speed is 10 rpm; the third duration is 30 - 50 s, and the fourth duration is 1 s.

[0031] Preferably, in the method for coating the thick film photoresist for advanced packaging, in step (1), the positioning carrier rotates uniformly at a rotation speed of 800 - 1000 rpm, and the RRC nozzle is moved to the center of the wafer and the photoresist solvent is sprayed, so that the entire surface of the wafer is coated with the photoresist solvent.

[0032] Compared with the prior art, in the method for coating the thick film photoresist for advanced packaging of the present invention, the first photoresist spin coating and the second photoresist spin coating are continuously performed on the wafer, and the first duration of the first photoresist spin coating is less than the second duration of the second photoresist spin coating, so that the first glue layer and the second glue layer formed by the two spin coatings can be completely fused to obtain a photoresist layer of more than 60 μm, and then the photoresist layer is subjected to a soft bake. First, it solves the problem that the thickness of the photoresist layer in the one - time coating method is too low to meet the requirements, and makes it easy to control the target thickness of the required photoresist layer; second, because the two spin coatings are continuously performed, the first glue layer and the second glue layer can be completely fused, so that the uniformity of the overall obtained photoresist layer is better; third, after the photoresist layer is obtained by two consecutive spin coatings, a soft bake is performed, so that the baking time of the first glue layer and the second glue layer is the same, that is, the baking time of all the photoresist inside the photoresist layer is the same, and the degree of internal solvent volatilization is consistent, making the uniformity of the columnar openings formed after subsequent exposure and development better, and the sidewall angle more vertical, solving the problems such as different sizes of the columnar openings and inclined angles after development caused by uneven baking in the existing two - spin - coating method; finally, because one baking process is omitted compared with the prior art, the entire process flow is more simplified, the process time is greatly reduced, and the production efficiency of the machine is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the state of spraying the photoresist solvent on the wafer in the coating method of the present invention.

[0034] Figure 2 is the schematic diagram of the state of the first drop of glue on the wafer in Figure 1 .

[0035] Figure 3 is the schematic diagram of the state of spin coating the glue and spraying the photoresist solvent on the wafer in Figure 2 .

[0036] Figure 4 is Figure 3 the schematic diagram of the state of forming the first glue layer on the wafer in

[0037] Figure 5 is the schematic diagram of the state of the second drop of glue on the wafer in Figure 3 .

[0038] Figure 6 is Figure 5 the schematic diagram of the state of forming the second glue layer on the wafer in

[0039] Figure 7 is the schematic diagram of the state of obtaining the photoresist layer with the target thickness after thinning the edge of the second glue layer on the wafer in Figure 6 . Detailed implementation manners

[0040] Now, embodiments of the present invention will be described with reference to the accompanying drawings, and like reference numerals in the drawings represent like elements. It should be noted that the orientation descriptions involved in the present invention, such as up, down, left, right, front, back, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the technical solutions of the present application or / and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. The first, second, etc. described are only used to distinguish technical features, and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0041] Combined with Figures 1-7 shown, the glue coating method of the thick film photoresist for advanced packaging provided by the present invention is particularly suitable for spin coating the photoresist with high viscosity (>4000 cp) on a 12-inch wafer 200 to obtain a thick photoresist film with a height between 60 μm and 120 μm, so as to meet the masking requirements of 60 μm electroplated copper pillars and C4 (Controlled Collapse Chip Connection) bumps.

[0042] In addition, the method for coating a thick film photoresist for advanced packaging of the present invention performs two spin coatings at one time within a coating unit 100. Among them, the coating unit 100 includes a positioning carrier 110, a spin coating nozzle 120 disposed above the positioning carrier 110, an RRC (Reduced Resist Consumption) nozzle 130, and an EBR (Edge Bead Removal) nozzle 140. Each part structure of the coating unit 100 is a conventional structure in the art.

[0043] More specifically, the positioning carrier 110 is preferably a vacuum chuck, and the following will take the vacuum chuck as an example for description. Of course, the positioning carrier 110 is not limited thereto, and it may also be other carriers, jigs, etc. that can position the smooth wafer 200.

[0044] It is understandable that the coating method of the present application is not limited to being used on a 12-inch wafer 200. It is also feasible to use this coating method on wafers of other sizes to achieve spin coating of a high-viscosity photoresist.

[0045] Continue to combine Figures 1-7 As shown, in an embodiment of the present invention, the method for coating a thick film photoresist for advanced packaging includes the following steps:

[0046] S01. Provide a wafer, place the wafer on the positioning carrier, rotate the positioning carrier and spray a photoresist solvent on the wafer to perform a surface wetting treatment on the wafer.

[0047] Specifically refer to Figure 1 As shown, in this embodiment, the positioning carrier is a vacuum chuck 110. Therefore, first place the wafer 200 on the stationary vacuum chuck 110, then rotate the vacuum chuck 110 at a uniform speed of 800-1000 rpm, then move the RRC (Reduced Resist Consumption) nozzle 130 above the center of the wafer 200, spray the photoresist solvent 300 at the center of the wafer 200, and rotate the vacuum chuck 110 at a uniform speed for 15-20 s to make the photoresist solvent 300 cover the entire surface of the wafer 200, and perform a surface wetting treatment on the wafer 200. The purpose is to facilitate better coverage of the high-viscosity photoresist on the entire surface of the wafer 200 during subsequent spin coating.

[0048] S02. Perform a first spin coating on the surface of the wafer to obtain a first glue layer. Among them, after the photoresist reaches the edge of the wafer, continue to rotate for a first period of time to flatten the photoresist on the surface of the wafer to obtain the first glue layer.

[0049] Combine Figures 2-4As shown, in this embodiment, the first photoresist spin coating is completed by dispensing glue, rotary diffusion, and spin coating to obtain the first glue layer 410. Among them, the duration of the spin coating is the first duration, and this first duration is relatively short because the surface of the uncoated wafer 200 is relatively smooth. If the first duration is too long, the photoresist on the surface of the wafer 200 will be thrown out of the wafer 200, causing waste, and at the same time reducing the effect of the first spin coating. Therefore, a shorter first duration is set during the first photoresist spin coating to flatten the photoresist on the surface of the wafer 200 to obtain the first glue layer 410, while reducing the waste of the photoresist.

[0050] S03. Perform a second photoresist spin coating on the surface of the wafer to obtain a second glue layer, and make the second glue layer fully fuse with the first glue layer to obtain a photoresist layer with a target thickness; among them, after the second glue layer reaches the edge of the wafer, continue to rotate for a second duration to make the second glue layer fully fuse with the first glue layer, and the second duration is greater than the first duration;

[0051] Combined with Figures 5-7 As shown, in this embodiment, the second photoresist spin coating is also completed by dispensing glue, rotary diffusion, and spin coating to obtain the second glue layer 420, and the methods and conditions of dispensing glue and rotary diffusion are the same as those in the above first photoresist spin coating. However, the second duration of the spin coating is much longer than the first duration because the diffusion rate of the second glue layer 420 on the first glue layer 410 is slow, and a longer spin coating duration is required to flatten the second glue layer 420 and make the second glue layer 420 and the first glue layer 410 fully fuse, while facilitating the control of the thickness of the second glue layer 420 to reach the target thickness; in addition, since the diffusion rate of the second glue layer 420 is slow, the amount of photoresist thrown out of the wafer 200 is small and it is not easy to cause waste.

[0052] S04. Perform soft baking on the photoresist layer to obtain a photoresist film.

[0053] In this embodiment, the baking temperature and time are determined according to the specific type of photoresist used and are not specifically limited in this application. After baking, edge bead removal (EBR) treatment is completed, that is, all processes are ended. Since soft baking is performed after two consecutive spin coatings, the baking times of the first glue layer 410 and the second glue layer 420 are the same, that is, the baking time of the photoresist layer 400 obtained after two spin coatings is the same, and the degree of solvent evaporation inside is the same, making the uniformity of the columnar openings formed after subsequent exposure and development better and the sidewall angle more vertical.

[0054] The following combined with Figures 2-4 As shown, in a specific embodiment of the present invention, the above step S02 specifically includes the following steps:

[0055] S21. The positioning carrier is lowered to the first rotation speed, and the first drop of glue is performed at the center of the wafer. The glue dropping speed is 0.2 - 0.4 ml / s, and the glue dropping dose is 20 - 30 ml.

[0056] See Figure 2 As shown, the rotation speed of the vacuum chuck 110 is lowered from 800 - 1000 rpm during the spraying of the photoresist solvent to the first rotation speed, and the first rotation speed is preferably 100 - 200 rpm. Then, the spin coating nozzle 120 is moved above the center of the wafer 200, and the first drop of glue is performed at the center of the wafer 200. Combining Figure 7 As shown, the glue dropping dose needs to be determined according to the actual required thickness of the photoresist film 400. In a specific embodiment, when the thickness of the photoresist film 400 is less than 70 um, the glue dropping dose is about 20 ml; when the thickness of the photoresist film 400 is greater than 90 um, the glue dropping dose is about 30 ml. Of course, the glue dropping dose can be adjusted according to the actual production situation.

[0057] S22. The positioning carrier is raised from the first rotation speed to the second rotation speed, and rotates uniformly at the second rotation speed for the first diffusion duration so that the photoresist diffuses to the edge of the wafer.

[0058] See Figure 3 As shown, in this embodiment, the second rotation speed is preferably 1000 - 1200 rpm, and the first diffusion duration is preferably 15 - 20 s. Since the surface of the wafer 200 is smooth, after increasing the rotation speed of the vacuum chuck 110, the photoresist can quickly diffuse to the edge of the wafer 200 within a short diffusion duration.

[0059] More preferably, when the vacuum chuck 110 is raised from the first rotation speed to the second rotation speed, the EBR (Edge Bead Removal) nozzle 140 is simultaneously moved to a first distance inward from the edge of the wafer 200, and the photoresist solvent is sprayed onto the surface of the wafer 200, as Figure 3 shown. Since the RRC solvent in the above step S01 is thrown out of the wafer 200 or has dried in this step, the EBR solvent is supplemented to help the photoresist continue to diffuse outward at the edge position of the wafer 200, so as to further accelerate the speed of the photoresist diffusing to the edge of the wafer 200, enabling the photoresist to reach the edge of the wafer 200 more quickly. The state of the photoresist diffusing to the edge of the wafer 200 is as Figure 4 shown.

[0060] In this embodiment, the first distance is preferably 5 mm - 8 mm inward from the edge of the wafer 200, asFigure 3 As shown. Of course, the first distance is not limited thereto, and can be flexibly set according to the specific size of the wafer 200 and the viscosity of the photoresist.

[0061] S23. The positioning carrier is reduced from the second rotational speed to the third rotational speed and rotates at a constant speed for the first duration to flatten the photoresist, and the first photoresist spin coating is completed to obtain the first glue layer; wherein, the third rotational speed is lower than the second rotational speed and higher than the first rotational speed.

[0062] See Figure 4 As shown, in this embodiment, the third rotational speed is preferably 600 - 800 rpm, and the first duration is preferably 20 - 30 s. Specifically, when the photoresist reaches the edge of the wafer 200, the rotational speed of the vacuum chuck 110 is reduced to achieve the purpose of leveling the glue, so that the spin-coated photoresist is flattened to obtain the first glue layer 410. Among them, since the surface of the wafer 200 is relatively smooth, the first duration of rotational leveling in this step is short, which can avoid wasting the photoresist on the surface of the wafer 200 being thrown out of the wafer 200 and improve the spin coating effect of the first glue layer 410 at the same time.

[0063] It can be understood that the first duration is not limited to that in this embodiment, and can be flexibly set according to the specific size of the wafer 200 and the viscosity of the photoresist.

[0064] Next, in conjunction with Figures 5-7 As shown, in a specific embodiment of the present invention, the above step S03 specifically includes the following steps:

[0065] S31. The positioning carrier is reduced to the first rotational speed again, and the second glue dropping is performed at the center of the wafer, and the glue dropping speed is 0.2 - 0.4 ml / s, and the glue dropping dose is 20 - 30 ml;

[0066] See Figure 5 As shown, in this embodiment, the rotational speed of the vacuum chuck 110 is reduced from the third rotational speed in the above step S23 to the first rotational speed again, that is, from 600 - 800 rpm to 100 - 200 rpm, and then the spin coating nozzle 120 is moved above the center of the wafer 200 again, and the second glue dropping is performed at the center of the wafer 200. The speed and dose of the second glue dropping are preferably the same as those of the first glue dropping. Specifically, when the thickness of the photoresist film 400 is less than 70 um, the glue dropping dose is about 20 ml; when the thickness of the photoresist film 400 is greater than 90 um, the glue dropping dose is about 30 ml. Of course, the glue dropping dose can be adjusted according to the actual production situation.

[0067] S32. The positioning carrier is increased from the first rotational speed to the second rotational speed, and rotates at a constant speed for a second diffusion duration at the second rotational speed so that the photoresist diffuses to the edge of the wafer to obtain a second glue layer, and the second diffusion duration is greater than the first diffusion duration;

[0068] See Figure 6 As shown, in this embodiment, the rotational speed of the vacuum chuck 110 is increased from the first rotational speed to the second rotational speed again, that is, increased from 100 - 200 rpm to 1000 - 1200 rpm again, and the second diffusion duration is preferably 25 - 30 s. Since the diffusion is carried out on the first glue layer 410 after the second drop of glue, the speed is slower, and a longer diffusion time is required to make the photoresist diffuse to the edge of the wafer 200. Therefore, the second diffusion duration is greater than the first diffusion duration. Thus, a second glue layer 420 is obtained, and the second glue layer 420 covers the upper part of the first glue layer 410.

[0069] S33. The positioning carrier is decreased from the second rotational speed to the third rotational speed and rotates at a constant speed for a second duration so that the photoresist reaches the target thickness, thereby obtaining a photoresist layer and completing the second photoresist spin coating; wherein, the third rotational speed is lower than the second rotational speed and higher than the first rotational speed;

[0070] Continue to see Figure 6 As shown, in this embodiment, when the photoresist diffuses to the edge of the wafer 200, the rotational speed of the vacuum chuck 110 is decreased from the second rotational speed to the third rotational speed again, that is, decreased from 1000 - 1200 rpm to 600 - 800 rpm again; then the vacuum chuck 110 is rotated at a constant speed for 100 - 150 s, that is, the second duration for rotating and leveling the second glue layer 420 is 100 - 150 s, which is much longer than the above-mentioned first duration (20 - 30 s). The purpose is to make the second glue layer 420 with high viscosity and not baked fully fuse with the first glue layer 410 through long-term low-speed rotation, eliminate the uniformity difference on the joint surface of the second glue layer 420 and the first glue layer 410, so that the uniformity of the finally obtained photoresist layer 400 is better, and the second glue layer 420 is flattened and its thickness is easy to control through long-term low-speed rotation, so that the thickness of the finally obtained photoresist layer 400 is easy to control. In addition, due to the surface tension effect at the edge of the wafer 200, after the second glue layer 420 and the first glue layer 410 with high viscosity and not baked are fully fused, they will gradually accumulate at the edge of the wafer 200 (see Figure 6 ), forming an upward convex part. During this process, the amount of photoresist thrown out of the wafer 200 is less and it is not easy to cause waste.

[0071] More preferably, in this step, after the photoresist layer 400 reaches the target thickness, the backside cleaning of the wafer 200 is further turned on to prevent the backside of the wafer 200 from being soiled.

[0072] S34. The positioning carrier is reduced from the third rotation speed to the fourth rotation speed, and the EBR nozzle is moved to a second distance inward from the edge of the wafer, and the photoresist solvent is sprayed onto the edge of the wafer and rotated for a third period of time to reduce the thickness of the photoresist accumulation at the edge of the wafer; wherein, the fourth rotation speed is higher than the first rotation speed.

[0073] Continue to refer to Figure 6 As shown, in this embodiment, since the photoresist accumulates at the edge position of the wafer 200 after rotation in the above step S33, forming an upward convex portion, the thickness of the edge position of the photoresist layer 400 reaching the target thickness is greater. Therefore, in this step, the edge position of the photoresist layer 400 is thinned. Specifically, first, the rotation speed of the vacuum chuck 110 is reduced from 600 - 800 rpm to 300 - 400 rpm, and then the EBR (Edge Bead Removal) nozzle 140 is moved again to a second distance inward from the edge of the wafer 200, as Figure 7 shown. Then the photoresist solvent is sprayed onto the edge of the wafer 200 and rotated for a third period of time to reduce the thickness of the photoresist accumulation at the edge position of the wafer 200, make the thickness of the photoresist layer 400 more uniform, and at the same time remove the overflowing photoresist on the sidewall of the wafer 200. The state of the photoresist layer 400 after the thinning process is as Figure 7 shown.

[0074] In this embodiment, the second distance is preferably 1 mm - 2 mm inward from the edge of the wafer 200, and the third period of time is preferably 30 - 50 s.

[0075] It can be understood that the fourth rotation speed, the third period of time, and the second distance are not limited to the above numerical ranges, and can be flexibly set according to the specific size of the wafer 200, the thickness, width of the photoresist accumulated at the edge of the wafer 200, and the viscosity of the photoresist, etc.

[0076] S35. The positioning carrier is increased from the fourth rotation speed to the fifth rotation speed and rotated for a fourth period of time to spin off the excess photoresist solvent, and then the speed is reduced to the sixth rotation speed; wherein, the fifth rotation speed is the maximum and the sixth rotation speed is the minimum.

[0077] In this embodiment, the fifth speed is preferably 1300-1500 rpm, and the sixth speed is preferably 10 rpm. Therefore, the fifth speed is the largest of all speeds, and the sixth speed is the smallest of all speeds. In addition, the fourth time duration is preferably 1 s. That is to say, by increasing the speed of the vacuum suction cup 110 to the maximum speed and rotating it for a very short time to quickly shake off excess solvent. Then immediately reduce it to the lowest speed, that is, reduce it to 10 rpm, to complete the entire process of the second coating.

[0078] Combined with the above description, the coating method of the thick film photoresist for advanced packaging of the present invention can obtain a photoresist film of 60 to 120 um after two consecutive spin coatings in a coating unit 100 and a soft bake, and the total process time of the method is about 900 to 1100 seconds, and the specific time varies according to the type of photoresist and the target thickness. Through experimental comparison, it was found that the total process time of the prior art after two coatings and two soft bakes was about 1300 to 1500 seconds. Therefore, the total time of the coating method of the present application saves 30% to 40% compared with the prior art, greatly reducing the process time and improving the production efficiency of the machine.

[0079] In addition, the first glue layer 410 and the second glue layer 420 are continuously spin-coated and fully fused to obtain the photoresist layer 400, and the photoresist layer 400 is baked once, and the baking time of all the photoresists inside it is consistent, and the degree of volatilization of the internal solvent is consistent, so that the CD (Critical Dimension) uniformity of the photoresist film after development is <5%. In the prior art, after the first spin coating and baking, the second spin coating and baking are performed, and the uniformity of the photoresist film is between 10% and 15%. Obviously, the uniformity of the photoresist film obtained in the present application is better. Moreover, the present application also solves the problems of uneven opening sizes and tilted angles after development caused by uneven baking twice in the prior art.

[0080] In summary, in the method for coating a thick film photoresist for advanced packaging of the present invention, the first photoresist spin coating and the second photoresist spin coating are continuously performed on the wafer 200, and the first duration of the first photoresist spin coating is less than the second duration of the second photoresist spin coating, so that the first glue layer and the second glue layer formed by the two spin coatings can be completely fused to obtain a photoresist layer 400 with a thickness of more than 60 μm. First, it solves the problem that the thickness of the photoresist layer 400 in the single coating method is too low to meet the requirements, and makes it convenient to control the target thickness of the required photoresist layer 400. Secondly, since the two spin coatings are continuously performed, the first glue layer and the second glue layer can be completely fused, so that the uniformity of the overall obtained photoresist layer 400 is better. Moreover, after the photoresist layer 400 is obtained by two consecutive spin coatings, a soft bake is performed once to make the baking time of the first glue layer and the second glue layer the same, that is, to make the baking time of all the photoresists inside the photoresist layer 400 the same, and the degree of internal solvent volatilization is consistent, so that the uniformity of the columnar openings formed after subsequent exposure and development is better, and the sidewall angle is more vertical, solving the problems such as different sizes and inclined angles of the columnar openings after development caused by uneven baking in the prior art of the two spin coating methods. In addition, since one baking process is omitted compared with the prior art, the entire process flow is simplified, the process time is greatly reduced, and the production efficiency of the machine is improved.

[0081] The parameters such as rotation speed and time involved in the present invention are reference values, and corresponding adjustments should be made according to the photoresist used during specific process debugging.

[0082] The above-disclosed are only the preferred embodiments of the present invention, and of course, the scope of rights of the present invention cannot be limited thereby. Therefore, equivalent changes made according to the scope of the patent application of the present invention still fall within the scope covered by the present invention.

Claims

1. A method for coating a thick film photoresist for advanced packaging, characterized in that, The method includes the following steps: (1) Provide a wafer, place the wafer on a positioning carrier, rotate the positioning carrier and spray a photoresist solvent on the wafer to perform a surface wetting treatment on the wafer; (2) Perform a first photoresist spin coating on the surface of the wafer to obtain a first photoresist layer. After the photoresist reaches the edge of the wafer, continue to rotate for a first period of time to flatten the photoresist on the surface of the wafer to obtain the first photoresist layer; (3) Perform a second photoresist spin coating on the surface of the wafer, and fully fuse the second photoresist layer with the first photoresist layer to obtain a photoresist layer with a target thickness. After the photoresist reaches the edge of the wafer, continue to rotate for a second period of time to fuse the photoresist. The second period of time is longer than the first period of time; (4) Perform soft baking on the photoresist layer to obtain a photoresist film.

2. The coating method of the thick film photoresist for advanced packaging according to claim 1, characterized in that, Step (2) includes the following steps: (21) Lower the positioning carrier to a first rotation speed, perform a first drop of photoresist at the center of the wafer, with a dropping speed of 0.2 - 0.4 ml / s and a dropping dose of 20 - 30 ml; (22) Raise the positioning carrier from the first rotation speed to a second rotation speed, and rotate at a constant speed for a first diffusion period of time at the second rotation speed to allow the photoresist to diffuse to the edge of the wafer; (23) Lower the positioning carrier from the second rotation speed to a third rotation speed and rotate at a constant speed for the first period of time to flatten the photoresist, completing the first photoresist spin coating to obtain the first photoresist layer. The third rotation speed is lower than the second rotation speed and higher than the first rotation speed.

3. The coating method of the thick film photoresist for advanced packaging according to claim 2, wherein, In step (22), when the positioning carrier is raised from the first rotation speed to the second rotation speed, simultaneously move the EBR nozzle to a first distance inward from the edge of the wafer, and spray the photoresist solvent onto the surface of the wafer to accelerate the diffusion of the photoresist to the edge of the wafer.

4. The coating method of the thick film photoresist for advanced packaging according to claim 3, wherein, The first distance is 5 - 8 mm inward from the edge of the wafer, and the first diffusion period of time is 15 - 20 s.

5. The coating method of the thick film photoresist for advanced packaging according to claim 1, wherein Step (3) includes the following steps: (31) Lower the positioning carrier again to the first rotation speed, perform a second drop of photoresist at the center of the wafer, with a dropping speed of 0.2 - 0.4 ml / s and a dropping dose of 20 - 30 ml; (32) Raise the positioning carrier from the first rotation speed to the second rotation speed, and rotate at a constant speed for a second diffusion period of time at the second rotation speed to allow the photoresist to diffuse to the edge of the wafer to obtain a second photoresist layer; (33) Lower the positioning carrier from the second rotation speed to the third rotation speed and rotate at a constant speed for a second period of time to make the photoresist reach the target thickness, thereby obtaining the photoresist layer and completing the second photoresist spin coating. The third rotation speed is lower than the second rotation speed and higher than the first rotation speed; (34) Lower the positioning carrier from the third rotation speed to the fourth rotation speed, and move the EBR nozzle to a second distance inward from the edge of the wafer, spray the photoresist solvent onto the edge of the wafer and continue to rotate for a third period of time to reduce the photoresist accumulation thickness at the edge of the wafer. The fourth rotation speed is higher than the first rotation speed.

6. The coating method of the thick film photoresist for advanced packaging according to claim 5, characterized in that, Step (3) further includes the following steps: (35) The positioning carrier increases from the fourth rotation speed to the fifth rotation speed, and continues to rotate for a fourth time period to shake off excess photoresist solvent, and then decreases to a sixth rotation speed; wherein the fifth rotation speed is the maximum rotation speed of all rotation speeds, and the sixth rotation speed is the minimum rotation speed of all rotation speeds.

7. The coating method of the thick film photoresist for advanced packaging according to claim 5, characterized in that, The second diffusion time is 25 to 30 seconds, and the second distance is 1 mm to 2 mm inward from the edge of the wafer.

8. The coating method of the thick film photoresist for advanced packaging according to any one of claims 1-7, characterized in that, The first duration is 20 to 30 seconds, and the second duration is 100 to 150 seconds.

9. The method for coating thick film photoresist for advanced packaging according to claim 2 or 5, wherein the first rotation speed is 100-200 rpm, the second rotation speed is reduced to 1000-1200 rpm, and the third rotation speed is 600-800 rpm.

10. The method for coating a thick film photoresist for advanced packaging according to claim 6, wherein, The fourth rotation speed is 300-400 rpm, the fifth rotation speed is 1300-1500 rpm, and the sixth rotation speed is 10 rpm; the third time length is 30-50 s, and the fourth time length is 1 s.

11. The coating method of the thick film photoresist for advanced packaging according to claim 1, characterized in that, In the step (1), the positioning carrier rotates at a constant speed of 800 to 1000 rpm, moves the RRC nozzle to the center of the wafer and sprays the photoresist solvent so that the photoresist solvent covers the entire surface of the wafer.

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