Gluing method of high-viscosity photoresist

Abstract

The invention discloses a high-viscosity photoresist coating method, which comprises the following steps of: controlling a photoresist dripping nozzle to gradually move from an initial photoresist dripping position to a termination photoresist dripping position according to a preset stepping distance in the radius direction of a wafer, and controlling the rotating speed of the wafer to be sequentially reduced from a first rotating speed; the photoresist dripping time length of the photoresist dripping nozzle at each photoresist dripping position is sequentially increased from the first time length, so that the photoresist circular rings distributed in a concentric circle manner are formed on the wafer, the photoresist layer with the required thickness is obtained, the required thickness is obtained through one-time photoresist coating, the film thickness uniformity is greatly improved, and the production efficiency is improved. The photoresist does not need to be thrown to the edge of the wafer through high-speed rotation, so that the photoresist dripping dosage only needs to be sprayed according to the actual film thickness, redundant photoresist does not exist, the waste rate of the photoresist is almost zero, and the production cost is greatly reduced; and meanwhile, a large amount of photoresist cannot be accumulated and polluted on the inner wall of the gluing groove, the blocking risk of an exhaust system is also greatly reduced, and the equipment maintenance cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of advanced packaging technologies, and particularly to a method for coating a high-viscosity photoresist. 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, C4 (Controlled Collapse Chip Connection) solder balls in 2.5D packaging, etc., and their height is at least greater than 80 μm. Therefore, a high-viscosity (cp > 2000) photoresist must be used for thick film masking, and the thickness of the photoresist film formed should be greater than 90 μm to meet the requirements of electroplating height.

[0003] Currently, the commonly used coating method in the industry is to spray the photoresist at the center of the wafer and then spin it at high speed, so that the photoresist evenly covers the surface of the wafer and reaches the target thickness through high-speed rotation. However, for high-viscosity photoresists, the existing methods have the following problems:

[0004] First, in order to ensure that the photoresist can completely cover the positive wafer without defects such as missing glue and leaking glue, the general spray volume is far more than the actual amount of glue required for film formation. Taking a 300-mm wafer with a film formation thickness of 50 μm as an example, the volume of the photoresist finally remaining on the wafer surface is about 3.5 ml. However, in actual process settings, the spray volume is at least more than 4 times of it (generally > 15 ml), which means that most of the photoresist will be thrown out of the wafer, resulting in great waste and increased costs;

[0005] Second, the maximum thickness that can be achieved in a single film formation by the center spray coating method is only 50 - 60 μm, which cannot meet the requirements of electroplated copper pillars and C4 > 80 μm; although the double spray coating and spin coating method can increase the film formation thickness to more than 90 μm, the waste of photoresist caused by double spray coating is more serious and the cost is higher;

[0006] Third, due to the high viscosity of the thick film, some models even reach more than 7000, so the center spray coating method increases the difficulty of throwing the photoresist to the edge of the wafer and affects the uniformity of photoresist diffusion. The resulting problem is that the film thickness difference between the center area and the edge is relatively large, generally between 10% - 15%, with large thickness fluctuations, resulting in a large difference in the line width of the photolithography pattern after development, affecting the coplanarity of the metal after electroplating; moreover, the process of controlling the film thickness uniformity of high-viscosity photoresist is difficult and the process stability is poor;

[0007] Fourth, during high-speed spin coating, the photoresist begins to spread as the wafer rotates, and in this process, it is easy to entrap air into the photoresist to form bubbles, affecting the film formation quality and yield, and this phenomenon occurs more frequently in high-viscosity photoresists;

[0008] V. After the excess photoresist is spun off the wafer, a part of it accumulates on the inner wall of the coating tank, and a part is discharged through the bottom exhaust system; however, after the equipment has been in production for a period of time, the residual photoresist on the inner wall will continue to accumulate, increasing the cleaning difficulty, and there is also a risk of blockage in the exhaust pipe.

[0009] Therefore, it is necessary to provide a method for coating a high-viscosity photoresist that can reduce the amount of photoresist used, improve the film thickness uniformity, enhance the process yield, and reduce equipment contamination to solve the above technical problems. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for coating a high-viscosity photoresist that can reduce the amount of photoresist used, improve the film thickness uniformity, enhance the process yield, and reduce equipment contamination.

[0011] To achieve the above object, the technical solution of the present invention is: to provide a method for coating a high-viscosity photoresist, which includes the following steps:

[0012] (1) Move the dispensing nozzle to the starting dispensing position above the wafer, control the wafer to rotate at a first rotation speed, and control the dispensing nozzle to dispense glue on the wafer for a first duration, wherein the starting dispensing position deviates from the center point of the wafer;

[0013] (2) Control the dispensing nozzle to sequentially move a preset step distance along the radius direction of the wafer from the starting dispensing position, then control the rotation speed of the wafer to sequentially decrease from the first rotation speed, and control the dispensing nozzle to dispense glue on the wafer, and the dispensing duration sequentially increases from the first duration;

[0014] (3) Determine whether the dispensing nozzle has moved to a preset termination dispensing position or whether it has moved a preset number of steps; if not, return to step (2), if so, proceed to step (4); wherein the termination dispensing position is the edge position or a position close to the edge of the wafer;

[0015] (4) Control the wafer to rotate at an nth rotation speed, and control the dispensing nozzle to dispense glue on the wafer for an nth duration;

[0016] (5) Control the dispensing nozzle to stop dispensing glue, and control the wafer to stop rotating.

[0017] In the method for coating a high-viscosity photoresist of the present invention, the dispensing rate of the dispensing nozzle is the same at each dispensing position. By precisely controlling the dispensing rate and keeping the dispensing rate constant, the stability and accuracy of dispensing are ensured, thereby ensuring the uniformity of the film thickness, and the film thickness can be adjusted by adjusting the dispensing rate.

[0018] In the method for coating a high-viscosity photoresist of the present invention, along the moving direction of the dispensing nozzle, the rotation speed of the wafer gradually decreases from the first rotation speed to the nth rotation speed, and the dispensing duration of the dispensing nozzle at each dispensing position gradually increases from the first duration to the nth duration.

[0019] In the method for coating a high-viscosity photoresist of the present invention, along the moving direction of the dispensing nozzle, the angular velocity corresponding to each dispensing position on the wafer gradually decreases, and the linear velocity corresponding to each dispensing position on the wafer remains the same.

[0020] Preferably, in the method for coating a high-viscosity photoresist of the present invention, before the step (1), it further includes:

[0021] Presetting the starting dispensing position, the ending dispensing position, the step distance, and the first rotation speed;

[0022] Or presetting the starting dispensing position, the step distance, the first rotation speed, and the number of steps.

[0023] Preferably, the step distance is 0.8d < s < 1.2d, where s is the step distance and d is the inner diameter of the dispensing nozzle.

[0024] Preferably, the horizontal distance of the starting dispensing position deviating from the center point of the wafer is r1, r1 = d / 2, where d is the inner diameter of the dispensing nozzle; the ending dispensing position is a position 0 to 2 mm away from the edge of the wafer.

[0025] Preferably, the horizontal distance of the starting dispensing position deviating from the center point of the wafer is r1; at the starting dispensing position, the first dispensing duration of the dispensing nozzle is T1, the first rotation speed of the wafer is N1, and 50 rpm < N1 < 10 rpm; the angular velocity of the wafer rotation is W1 and the linear velocity is V1; where,

[0026] T1 = 60 s / N1,

[0027] W1 = 2π / T1,

[0028] V1 = W1 * r1.

[0029] In the method for coating a high-viscosity photoresist of the present invention, at the starting dispensing position, the residence duration of the dispensing nozzle is T1', T1' = T1 + T o , where T0 is the duration from the start of dispensing until the photoresist reaches the wafer surface from the dispensing nozzle.

[0030] In the method for coating a high-viscosity photoresist of the present invention, calculate the ending dispensing position or the number of steps according to the following formula;

[0031] r n = r1 + (n - 1)s

[0032] where r n is the horizontal distance from the center point of the wafer to the dispensing position where the dispensing nozzle is located after moving each step distance, r1 is the horizontal distance by which the starting dispensing position deviates from the center point of the wafer, s is the step distance, and n is the number of steps and is a natural number greater than or equal to 2.

[0033] In the method for coating a high-viscosity photoresist of the present invention, when the dispensing nozzle is at a dispensing position after moving each step distance, the rotational speed N of the wafer is calculated according to the following formula n , the angular velocity W of the rotation of the wafer n , the nth duration T of the dispensing of the dispensing nozzle n ;

[0034] N n = 60s / T n ,

[0035] T n = 2π / W n ,

[0036] W n = V n / r n ;

[0037] where r n is the horizontal distance from the center point of the wafer to the dispensing position where the dispensing nozzle is located, V n is the linear velocity of the rotation of the wafer at the dispensing position, and V n is the same as the linear velocity V1 of the rotation of the wafer at the starting dispensing position, and n is a natural number greater than or equal to 2.

[0038] In the method for coating a high-viscosity photoresist of the present invention, the dispensing nozzle forms a photoresist ring on the surface of the wafer at the starting dispensing position, the terminating dispensing position, and each intermediate dispensing position, and the photoresist rings formed at each dispensing position are concentrically distributed.

[0039] In the method for coating a high-viscosity photoresist of the present invention, before the step (1), it further includes:

[0040] Providing the wafer and placing the wafer on a positioning carrier.

[0041] Preferably, the dispensing nozzle is moved to a position 5 mm to 10 mm above the wafer.

[0042] In the method for coating a high-viscosity photoresist of the present invention, the following steps are further included:

[0043] (6) Curing the wafer to obtain a photoresist layer, and performing edge trimming and cleaning after curing.

[0044] Compared with the prior art, due to the method for coating a high-viscosity photoresist of the present invention, controlling the dispensing nozzle to gradually move along the radial direction of the wafer from the starting dispensing position to the ending dispensing position according to a preset step distance, and controlling the rotational speed of the wafer to gradually decrease in sequence from the first rotational speed according to the order of the sequential movement of the dispensing nozzle, and controlling the dispensing duration of the dispensing nozzle at each dispensing position to gradually increase in sequence from the first duration, so that the dispensing nozzle forms concentric circular photoresist rings on the wafer. Therefore, the following technical effects are achieved:

[0045] First, the wafer rotates at a low speed throughout the entire process of coating the photoresist, and the rotational speed becomes lower and lower. Thus, a photoresist layer with the required thickness is obtained, and it is not necessary to spin the photoresist to the edge of the wafer by high-speed rotation. Therefore, the dispensing dose only needs to be sprayed according to the actual film thickness required, and there is no need to spray excess photoresist, making the waste rate of the photoresist close to zero and greatly reducing the production cost;

[0046] Second, a photoresist layer with the required thickness is obtained by the method of coating concentric rings. Since the photoresist has its own fluidity, the adjacent photoresist rings will automatically flow and flatten, thereby obtaining a photoresist layer with uniform thickness, which can greatly improve the film thickness uniformity. Moreover, by adjusting the spacing or overlapping state between adjacent photoresist rings, the thickness of the photoresist layer can be conveniently adjusted, facilitating the control of the film thickness uniformity;

[0047] Third, the wafer rotates at a low speed throughout the entire coating process, and the self-fluidity of the photoresist is utilized to achieve the purpose of flattening. In this process, common coating defects such as arrow shadow, back splash, air bubbles, and missing or leaking glue are effectively reduced, thereby improving the process yield and reducing the rework rate;

[0048] Fourth, since there is almost no photoresist thrown out of the wafer, there will be no large accumulation of photoresist on the inner wall of the coating tank, and the risk of blockage of the exhaust system is also greatly reduced, reducing the equipment maintenance cost;

[0049] Fifth, in the coating method of the present invention, there is no need to perform the pre-wetting step anymore, nor is there a need for a high-speed rotation process. Therefore, the photoresist at the edge of the wafer will not accumulate, and the time for the edge trimming step can be correspondingly reduced, which not only saves the amount of solvent used but also shortens the production time and improves the production efficiency. Description of the Drawings

[0050] Figure 1It is a flowchart of the method for coating a high-viscosity photoresist of the present invention.

[0051] Figure 2 It is a cross-sectional view of the dispensing nozzle in the starting dispensing position in the present invention.

[0052] Figure 3 Is Figure 2 A top view of the wafer in

[0053] Figure 4 Is Figure 2 A cross-sectional view of the dispensing nozzle in the starting dispensing position completing one circle of dispensing in

[0054] Figure 5 Is Figure 4 A top view of the wafer in

[0055] Figure 6 It is a cross-sectional view of the dispensing nozzle in the second dispensing position completing one circle of dispensing in the present invention.

[0056] Figure 7 Is Figure 6 A top view of the wafer in

[0057] Figure 8 It is a cross-sectional view of the dispensing nozzle in an intermediate dispensing position in the present invention.

[0058] Figure 9 Is Figure 8 A top view of the wafer in

[0059] Figure 10 It is a cross-sectional view of the dispensing nozzle in the terminating dispensing position completing one circle of dispensing in the present invention.

[0060] Figure 11 Is Figure 10 A top view of the wafer in Detailed implementation manners

[0061] Now, embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals 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 facilitating the description of 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 cannot be construed as a limitation to the present application. The first, second, etc. described are only used to distinguish technical features and cannot 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.

[0062] In combination with Figures 1-11As shown, the method for coating a high-viscosity photoresist provided by the present invention is particularly suitable for spin-coating a high-viscosity (e.g., viscosity > 2000 cp) photoresist on a 12-inch wafer 200 to obtain a thick-film photoresist layer 210 with a thickness between 50 μm and 120 μm. The thick-film photoresist layer 210 is used as a mask for electroplating metal to meet the mask requirements for electroplated copper pillars and C4 (Controlled Collapse Chip Connection) bumps with a height of 50 μm or more.

[0063] It is understandable that the coating method of the present application is not limited to being used on a 12-inch wafer 200, nor is it limited to obtaining a thick-film photoresist layer 210 with a thickness of 50 μm to 120 μm. According to needs, it is also feasible to use this coating method to spin-coat a high-viscosity photoresist on wafers of other sizes to obtain thick-film photoresist films with other thicknesses.

[0064] Continue to combine Figures 1-11 As shown, in the method for coating a high-viscosity photoresist of the present invention, the coating device 100 used includes a positioning carrier 110, a dispensing nozzle 120 disposed above the positioning carrier 110, and a controller. The controller is electrically connected to the positioning carrier 110 and the dispensing nozzle 120 respectively, and is used to control the positioning carrier 110 and the dispensing nozzle 120 to operate in a preset manner to achieve photoresist coating. Other structural parts of the coating device are all conventional structures in the art.

[0065] More specifically, the positioning carrier 110 is preferably a vacuum chuck 110. Of course, the positioning carrier 110 is not limited thereto, and it can also be other carriers, jigs, etc. that can position a smooth wafer 200.

[0066] Continue to combine Figures 1-11 As shown, in an embodiment of the present invention, the method for coating a high-viscosity photoresist includes the following steps:

[0067] S01. Provide a wafer and place the wafer on the positioning carrier;

[0068] Refer to Figures 2-3 As shown, in this embodiment, the positioning carrier 110 is preferably a vacuum chuck. The following will be described by taking the vacuum chuck as an example. Of course, the positioning carrier 110 is not limited thereto, and it can also be other carriers, jigs, etc. that can position a smooth wafer 200. Place the wafer 200 on the stationary vacuum chuck 110, and the vacuum chuck 110 adsorbs the wafer 200 for positioning.

[0069] S02. Move the dispensing nozzle above the wafer to the starting dispensing position, control the wafer to rotate at a first rotation speed, and control the dispensing nozzle to dispense glue on the wafer for a first duration, where the starting dispensing position deviates from the center point of the wafer;

[0070] Continue to combine Figures 2-3 As shown, in this embodiment, the starting dispensing position P1 is close to the center point P0 of the wafer 200, and at the same time, the starting dispensing position P1 deviates from the center point P0 of the wafer 200 by a certain distance. Specifically, the horizontal distance between the starting dispensing position P1 and the center point P0 of the wafer 200 is a first distance r1, and the first distance r1 is preferably half of the inner diameter d of the dispensing nozzle 120. As shown in the following formula:

[0071] r1 = d / 2, where d is the inner diameter of the dispensing nozzle 120.

[0072] It can be understood that the starting dispensing position P1 is not limited to that in this embodiment and can be flexibly adjusted according to the specific required thickness and coating requirements of the thick film photoresist layer 210.

[0073] Continue to combine Figures 2-3 As shown, in this embodiment, moving the dispensing nozzle 120 to the starting dispensing position P1 specifically means that the center of the dispensing nozzle 120 is located at the starting dispensing position P1 (see Figures 2-3 ), and the height of the dispensing nozzle 120 from the wafer 200 is 5 mm to 10 mm. Of course, the height of the dispensing nozzle 120 can be flexibly adjusted as needed.

[0074] Combine Figures 4-5 As shown, control the vacuum chuck 110 to rotate at a first rotation speed N1 at a constant speed, and drive the wafer 200 to rotate at a first rotation speed N1 at a constant speed by the vacuum chuck 110. At the same time, control the dispensing nozzle 120 to dispense glue on the surface of the wafer 200 for a first duration T1, and the first duration T1 is the duration for the dispensing nozzle 120 to form a photoresist ring 210ˋ on the surface of the wafer 200. At this time, the dispensing nozzle 120 completes the dispensing at the starting dispensing position P1, and the state of the photoresist ring 210ˋ formed on the surface of the wafer 200 is as Figure 5 shown. In this embodiment, since the photoresist has its own fluidity and r1 = d / 2, the photoresist ring 210ˋ formed at the starting dispensing position P1 actually forms a glue drop after the photoresist flows. Of course, for the case where r1 is larger, a photoresist ring 210ˋ is still formed.

[0075] In this embodiment, the first rotation speed N1 is set to a low rotation speed, specifically such that the photoresist ring 210ˋ formed on the surface of the wafer 200 does not significantly expand outward. Therefore, the first rotation speed N1 can be flexibly set according to the different viscosities of the photoresist. In a specific embodiment, the first rotation speed N1 is set such that 50 rpm < N1 < 10 rpm.

[0076] S03. Control the dispensing nozzle to sequentially move a preset step distance along the radial direction of the wafer from the starting dispensing position, then control the rotation speed of the wafer to gradually decrease from the first rotation speed, and control the dispensing nozzle to perform dispensing on the wafer. The dispensing duration is gradually increased from the first duration;

[0077] Combined with Figures 6-7 As shown, in this embodiment, the step distance s can be set according to the ultimately required film thickness. For different film thickness requirements, it can be adjusted by making the photoresist rings 210ˋ formed by dispensing overlap, be adjacent, or have a small gap. Therefore, the step distance s is correspondingly set according to the state between the photoresist rings 210ˋ to be formed.

[0078] In a specific embodiment, the step distance is preferably 0.8d < s < 1.2d, where s is the step distance and d is the inner diameter of the dispensing nozzle 120. In this way, when the dispensing nozzle 120 moves a step distance s along the radial direction of the wafer 200 from the starting dispensing position P1, the distance between the dispensing nozzle 120 and the center point P0 of the wafer 200 is the second distance r2. That is to say, at this time, the horizontal distance between the second dispensing position P2 where the dispensing nozzle 120 is located and the center point P0 of the wafer 200 is r2, and the second distance r2 is calculated by the following formula: r2 = r1 + s.

[0079] When the dispensing nozzle 120 continues to move a step distance s along the radial direction of the wafer 200 from the second dispensing position P2, at this time, the horizontal distance between the third dispensing position P3 where the dispensing nozzle 120 is located and the center point P0 of the wafer 200 is r3, that is, at this time, the horizontal distance between the third dispensing position P3 where the dispensing nozzle 120 is located and the center point P0 of the wafer 200 is r3. Therefore, r3 = r2 + s = r1 + 2s.

[0080] By analogy, when the dispensing nozzle 120 moves n step distances s along the radial direction of the wafer 200, the dispensing position where the dispensing nozzle 120 is located can be calculated according to the following formula.

[0081] r n = r1 + (n - 1)s

[0082] wherein, r n is the horizontal distance from the center point P0 of the wafer 200 to the dispensing position where the dispensing nozzle 120 moves one step distance s, r1 is the horizontal distance by which the starting dispensing position deviates from the center point P0 of the wafer, s is the step distance, and n is the number of steps and is a natural number greater than or equal to 2.

[0083] More specifically, when the step distance s is less than the inner diameter d of the dispensing nozzle 120, the adjacent photoresist rings 210ˋ formed on the surface of the wafer 200 overlap; when the step distance s is equal to the inner diameter d of the dispensing nozzle 120, the adjacent photoresist rings 210ˋ formed on the surface of the wafer 200 are in contact; when the step distance s is greater than the inner diameter d of the dispensing nozzle 120, there is a small gap between the adjacent photoresist rings 210ˋ formed on the surface of the wafer 200. Since the step distance s is greater than the inner diameter d of the dispensing nozzle 120 but still less than 1.2d, that is to say, the step distance s is only greater than the inner diameter d of the dispensing nozzle 120 by a small value. Due to the fluidity of the photoresist itself, the depressions formed between the adjacent photoresist rings 210ˋ due to overlap, contact or having a small gap will be leveled by automatic flow.

[0084] It can be understood that the step distance s is not limited to that in this embodiment, and can be increased or decreased accordingly according to the inner diameter d of the specific nozzle pipeline 120, the height of the nozzle pipeline 120 from the wafer 200, the film thickness uniformity of the thick film photoresist layer 210 to be obtained, and the surface topography of the film formation.

[0085] Continue to combine Figures 6-7As shown, when the dispensing nozzle 120 moves to the second dispensing position P2, the vacuum chuck 110 is controlled to rotate at a uniform speed at a second rotation speed N2, and the second rotation speed N2 is less than the first rotation speed N1. In a specific embodiment, the second rotation speed N2 is less than 50 rpm < N1 < 10 rpm. At the same time, the dispensing nozzle 120 is controlled to dispense glue on the surface of the wafer 200 at the second dispensing position P2, and the dispensing duration is the second duration T2. The second duration T2 is the duration for the dispensing nozzle 120 to form a photoresist ring 210ˋ on the surface of the wafer 200. Since the rotation speed of the wafer 200 is reduced at the second dispensing position P2, the second duration T2 for forming the photoresist ring 210ˋ is greater than the aforementioned first duration T1. And, the photoresist ring formed at this time overlaps, abuts or has a small gap with the photoresist ring (actually a glue drop) formed in the previous circle. Since the photoresist has its own fluidity, the photoresist rings 210ˋ between adjacent two circles will automatically flow and flatten, and finally a thick film photoresist layer 210 with uniform thickness is obtained, and the uniformity of the film thickness is greatly improved.

[0086] Combined with Figures 8-9 As shown, when the dispensing nozzle 120 continues to move a step distance s from the second dispensing position P2 to reach the third dispensing position P3, the rotation speed of the vacuum chuck 110 is controlled to decrease from the second rotation speed N2 to the third rotation speed N3 and rotate at a uniform speed. And, the dispensing duration at the third dispensing position P3 is the third duration T3, and the third duration T3 is greater than the second duration T2. By analogy, along the moving direction of the dispensing nozzle 120, the rotation speed of the wafer 200 is controlled to decrease sequentially from the first rotation speed N1, and the dispensing duration of the dispensing nozzle 120 at each dispensing position is controlled to increase sequentially from the first duration T1.

[0087] S04. Determine whether the dispensing nozzle moves to a preset termination dispensing position or whether it moves a preset number of steps; if not, return to step S03, if so, proceed to step S05; wherein, the termination dispensing position is the edge position of the wafer or a position close to the edge;

[0088] First combined with Figures 10-11 As shown, in this embodiment, the termination dispensing position P n is the edge position of the wafer 200 or a position close to the edge. The edge width is specifically determined according to actual process requirements and the step distance s, and thus the termination dispensing position P n is determined. In a specific embodiment, the termination dispensing position P n is a position 0 to 2 mm away from the edge of the wafer 200.

[0089] Next combined with Figures 8-11As shown, in this embodiment, the dispensing nozzle 120 is controlled to move along the radial direction of the wafer 200 from the starting dispensing position P1 to the ending dispensing position P n step by step according to a preset step distance s. Each time the dispensing nozzle 120 moves a step distance s, it is at an intermediate dispensing position. At the starting dispensing position P1, the ending dispensing position P n and each intermediate dispensing position, the dispensing nozzle 120 is controlled to form a photoresist ring 210ˋ on the wafer. Moreover, according to the moving direction of the dispensing nozzle 120, the rotation speed of the wafer 200 is controlled to gradually decrease from the first rotation speed N1, and at the same time, the dispensing duration for the dispensing nozzle 120 to form the photoresist ring 210ˋ on the surface of the wafer 200 is gradually increased from the first duration T1.

[0090] S05. Control the wafer to rotate at the nth rotation speed, and control the dispensing nozzle to perform dispensing on the wafer, and the dispensing duration is the nth duration;

[0091] Combined with Figures 10-11 As shown, in this embodiment, when the dispensing nozzle 120 moves to the ending dispensing position P n or after the dispensing nozzle 120 has moved a preset n step distances s, continue to control the dispensing nozzle 120 to perform dispensing on the surface of the wafer 200. During this process, control the vacuum chuck 110 to rotate at the nth rotation speed, that is, make the wafer 200 rotate at the nth rotation speed. The nth rotation speed is the minimum rotation speed among all rotation speeds. At the same time, at the ending dispensing position P n the continuous duration for forming the photoresist ring 210ˋ by rotational dispensing is the nth duration, and the nth duration is the maximum duration among all durations.

[0092] So far, in this application, the photoresist film 210 with a thickness of 50 μm to 120 μm is obtained by spin-coating the photoresist ring 210ˋ. It can not only solve the problem of low film thickness caused by single-time dispensing and spin-coating in the prior art, but also greatly improve the film thickness uniformity. Moreover, during the whole process of coating the photoresist, the wafer 200 always maintains a low rotation speed, and the rotation speed is getting lower and lower. There is no need to spin the photoresist to the edge of the wafer 200 by high-speed rotation. Therefore, the dispensing dose only needs to be sprayed according to the actual film thickness required, and there is almost no excess photoresist, so that the waste rate of the photoresist is almost 0, greatly reducing the production cost. Also because there is no high-speed rotation process, the photoresist at the edge of the wafer 200 will not accumulate, and at the same time, there will be no large amount of photoresist accumulated and polluted on the inner wall of the coating tank, and the risk of blockage of the exhaust system is also greatly reduced.

[0093] S06. Control the dispensing nozzle to stop dispensing, and control the wafer to stop rotating, and then cure the wafer to obtain a photoresist layer, and perform edge removal and cleaning after curing.

[0094] Specifically, after the thick film photoresist layer 210 is obtained by spin coating on the wafer 200, due to the fluidity of the photoresist itself, the adjacent photoresist rings 210ˋ will automatically flow and flatten, so as to obtain a thick film photoresist layer 210 with uniform thickness. At the same time, it can effectively reduce common coating defects such as arrow shadow, back splash, bubbles, and photoresist leakage, improve the process yield, and reduce the rework rate.

[0095] Then, the wafer 200 and the thick film photoresist layer 210 thereon are baked and cured. After baking, as the internal solvent evaporates, the uneven structure on the surface of the photoresist will become flat, and a photoresist film meeting the thickness requirement is obtained. Finally, edge cleaning is carried out to end the process.

[0096] Combining the above steps S01 - S06, it can be seen that in the coating method of the present invention, there is no need to perform the pre - wetting step, nor is a high - speed rotation process required. Therefore, the photoresist at the edge of the wafer 200 will not accumulate, and the time for the edge cleaning step can be correspondingly reduced. This not only saves the amount of solvent used, but also shortens the production time and improves production efficiency.

[0097] Combined again with Figures 2-11 As shown, in the coating method of the high - viscosity photoresist of the present invention, when the dispensing nozzle 120 dispenses glue at the starting dispensing position P1, the ending dispensing position P n and each intermediate dispensing position, the photoresist rings 210ˋ formed on the surface of the wafer 200 are concentrically distributed. And, the dispensing rate of the dispensing nozzle 120 at the starting dispensing position P1, the ending dispensing position P n and each intermediate dispensing position is the same. That is to say, the dispensing nozzle 120 maintains the same dispensing rate when forming each circle of photoresist rings 210ˋ. By precisely controlling the dispensing rate and keeping the dispensing rate constant, the stability and accuracy of dispensing are ensured, thereby ensuring the uniformity of the film thickness. And, the film thickness can be adjusted by adjusting the dispensing rate. Of course, the size of the dispensing rate is determined according to the finally required film thickness and the linear velocity of the rotation of the wafer 200.

[0098] Combined again with Figures 1-11 As shown, in an embodiment of the present invention, before the step S01, the following steps are further included:

[0099] S00. Preset the starting dispensing position, the ending dispensing position, the step distance, and the first rotation speed;

[0100] Or preset the starting dispensing position, the step distance, the number of steps, and the first rotation speed.

[0101] In a specific embodiment, according to the specific size of the wafer 200, the required trimming width, and the inner diameter d of the dispensing nozzle 120, the starting dispensing position P1, the ending dispensing position P n , and the step distance s are preset. Specifically, it is to preset the horizontal distances r1 and r n of the dispensing nozzle 120 from the center point P0 of the wafer 200 at the starting dispensing position P1 and the ending dispensing position P n . Then, according to the above formula r n = r1+(n - 1)s, the step number n can be calculated. The dispensing nozzle 120 is controlled to move step by step along the radial direction of the wafer 200 to complete the coating.

[0102] In a more preferred embodiment, according to the specific size of the wafer 200, the required trimming width, and the inner diameter of the dispensing nozzle 120, the starting dispensing position P1, the step distance s, and the step number n are preset. Among them, presetting the starting dispensing position P1 means presetting the horizontal distance r1 of the dispensing nozzle 120 from the center point P0 of the wafer 200 at the starting dispensing position P1. Then, the dispensing nozzle 120 can be directly controlled to move step by step along the radial direction of the wafer 200 according to the step distance s and the step number n until the preset step number n is completed, that is, the coating on the wafer 200 is completed. In this embodiment, the calculation steps are omitted, which can simplify the control method.

[0103] Combined again with Figures 2-11 shown, in the coating method of the present invention, along the moving direction of the dispensing nozzle 120, the rotation speeds corresponding to the respective dispensing positions on the wafer 200 decrease in sequence, that is, the rotation speed of the wafer 200 decreases from the first rotation speed N1 in sequence. At the same time, the angular velocities corresponding to the respective dispensing positions on the wafer 200 decrease in sequence. However, the linear velocities corresponding to the respective dispensing positions on the wafer 200 remain the same. That is to say, for the positions corresponding to the starting dispensing position P1, the ending dispensing position P n and each intermediate dispensing position on the wafer 200, the linear velocity of the rotation of the wafer 200 remains the same.

[0104] Combined again with Figures 2-5As shown in the figure, in the above step S02, when the dispensing nozzle 120 dispenses glue at the starting dispensing position P1, the horizontal distance between the center of the dispensing nozzle 120 and the center point P0 of the wafer 200 is r1. The vacuum chuck 110 drives the wafer 200 to rotate uniformly at the first rotation speed N1, and the first rotation speed N1 is a preset rotation speed, preferably preset to 50 rpm < N1 < 10 rpm. At this time, the angular velocity of the wafer 200 is W1 and the linear velocity is V1. As described above, the dispensing duration for forming the photoresist ring 210ˋ on the wafer 200 is the first duration T1. Therefore, the first duration T1, the angular velocity W1, and the linear velocity V1 can be calculated according to the following formulae.

[0105] T1 = 60s / N1,

[0106] W1 = 2π / T1,

[0107] V1 = W1 * r1.

[0108] As shown below in combination with Figures 6-11 the figure, in the above steps S03 and S04, when the dispensing nozzle 120 moves one step distance s each time, the horizontal distance between the center of the dispensing nozzle 120 and the center point P0 of the wafer 200 is r n , and can be calculated according to the formula r n = r1 + (n - 1)s above. Then, the rotation speed N of the wafer 200 at this time, the angular velocity W of the rotation of the wafer 200 n , and the dispensing duration T of the dispensing nozzle 120 are calculated according to the following formulae n ; n ;

[0109] N n = 60s / T n ,

[0110] T n = 2π / W n ,

[0111] W n = V n / r n ;

[0112] Among them, r n is the horizontal distance from the center point P0 of the wafer 200 to the intermediate dispensing position or the end dispensing position P where the dispensing nozzle 120 is located, V n is the linear velocity of the wafer 200 rotating at this intermediate dispensing position or the end dispensing position P n , and V n n ​is the same as the linear velocity V1 of the wafer 200 rotating at the starting dispensing position P1 (V1 is calculated by the formula V1 = W1 * r1), and n is a natural number greater than or equal to 2.

[0113] In addition, it should be noted that the dispensing duration mentioned in this application is the duration for the dispensing nozzle 120 to form a photoresist ring 210ˋ on the surface of the wafer 200. Specifically, since the dispensing nozzle 120 needs to wait for a certain time for the photoresist to reach the surface of the wafer 200 during the first dispensing, therefore, the residence duration of the dispensing nozzle 120 at the starting dispensing position P1 is greater than the first duration T1 for forming a photoresist ring 210ˋ on the surface of the wafer 200. If the residence duration of the dispensing nozzle 120 at the starting dispensing position P1 is T1', then T1' = T1 + T o , where T0 is the duration for the photoresist to reach the surface of the wafer 200 from the dispensing nozzle 120 after the start of dispensing. And at the intermediate dispensing position and the ending dispensing position P n , since the dispensing nozzle 120 has already dispensed and is in a continuous state, there is no need to wait. Therefore, the residence duration above the wafer 200 is the same as the dispensing duration.

[0114] In summary, in the method for coating a high-viscosity photoresist of the present invention, the dispensing nozzle 120 is controlled to move step by step along the radius direction of the wafer 200 from the starting dispensing position P1 to the ending dispensing position P n at a preset step distance s, and in the order of the sequential movement of the dispensing nozzle 120, the rotation speed of the wafer 200 is controlled to decrease sequentially from the first rotation speed N1, and the dispensing duration of the dispensing nozzle 120 at each dispensing position is controlled to increase sequentially from the first duration T1, so that the dispensing nozzle 120 forms concentric photoresist rings 210ˋ on the wafer 200, and finally a photoresist layer 210 with the required thickness is obtained. Therefore, the following technical effects are achieved:

[0115] First, the wafer 200 rotates at a low speed throughout the process of coating the photoresist, and the rotation speed becomes lower and lower. Thus, a photoresist layer with the required thickness is obtained. There is no need to spin the photoresist to the edge of the wafer 200 by high-speed rotation. Therefore, the dispensing dose only needs to be sprayed according to the actual film thickness required, and there is no need to spray excess photoresist, making the waste rate of the photoresist close to zero and greatly reducing the production cost;

[0116] Second, a photoresist layer 210 with a desired thickness is obtained by coating concentric rings. Since the photoresist has its own fluidity, the adjacent photoresist rings 210ˋ will automatically flow and flatten, thus obtaining a photoresist layer with uniform thickness, which can greatly improve the film thickness uniformity. Moreover, by adjusting the spacing or overlapping state between adjacent photoresist rings 210ˋ, the thickness of the photoresist layer can be easily adjusted, facilitating the control of film thickness uniformity;

[0117] Third, the wafer 200 maintains a low-speed rotation throughout the coating process, and the self-fluidity of the photoresist is utilized to achieve the purpose of flattening. In this process, common coating defects such as arrow shadow, back splash, bubbles, and photoresist leakage are effectively reduced, thereby improving the process yield and reducing the rework rate;

[0118] Fourth, since there is almost no photoresist thrown out of the wafer 200, there will be no large accumulation of photoresist on the inner wall of the coating tank, and the risk of blockage of the exhaust system is also greatly reduced, reducing the equipment maintenance cost;

[0119] Fifth, in the coating method of the present invention, there is no need to perform a pre-wetting step or a high-speed rotation process. Therefore, the photoresist at the edge of the wafer 200 will not accumulate, and the time for the edge cleaning step can be correspondingly reduced, which not only saves the amount of solvent used but also shortens the production time and improves production efficiency.

[0120] 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.

[0121] The structures of other parts of the coating device involved in the present invention are all conventional structures well-known to those of ordinary skill in the art, and will not be described in detail here.

[0122] 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 high-viscosity photoresist, characterized in that, The steps include the following: (1) Move the dispensing nozzle to the starting dispensing position above the wafer, control the wafer to rotate at a first rotational speed, and control the dispensing nozzle to dispense glue on the wafer for a first duration. The starting dispensing position is offset from the center point of the wafer; (2) Control the dispensing nozzle to sequentially move a preset step distance along the radial direction of the wafer from the starting dispensing position, then control the rotational speed of the wafer to sequentially decrease from the first rotational speed, and control the dispensing nozzle to dispense glue on the wafer, with the dispensing duration increasing sequentially from the first duration; (3) Determine whether the dispensing nozzle has moved to a preset termination dispensing position or whether a preset number of step movements has been made; if not, return to step (2), if so, proceed to step (4); where the termination dispensing position is the edge position or a position close to the edge of the wafer; (4) Control the wafer to rotate at an nth rotational speed, and control the dispensing nozzle to dispense glue on the wafer for an nth duration; (5) Control the dispensing nozzle to stop dispensing glue, and control the wafer to stop rotating.

2. The method for coating a high-viscosity photoresist according to claim 1, characterized in that, The dispensing rate of the dispensing nozzle is the same at each dispensing position.

3. The method for coating a high-viscosity photoresist according to claim 1, characterized in that, In the moving direction of the dispensing nozzle, the rotational speed of the wafer decreases sequentially from the first rotational speed to the nth rotational speed, and the dispensing duration of the dispensing nozzle at each dispensing position increases sequentially from the first duration to the nth duration.

4. The method for coating a high-viscosity photoresist according to claim 1, characterized in that, In the moving direction of the dispensing nozzle, the angular velocity corresponding to each dispensing position on the wafer decreases sequentially, and the linear velocity corresponding to each dispensing position on the wafer remains the same.

5. The method for coating a high-viscosity photoresist according to any one of claims 1-4, characterized in that, Before step (1), it further includes: Presetting the starting dispensing position, the termination dispensing position, the step distance, and the first rotational speed; Or presetting the starting dispensing position, the step distance, the first rotational speed, and the number of step movements.

6. The method for coating a high-viscosity photoresist according to claim 5, characterized in that, The step distance satisfies 0.8d < s < 1.2d, where s is the step distance and d is the inner diameter of the dispensing nozzle.

7. The method for coating a high-viscosity photoresist according to claim 5, characterized in that, The horizontal distance by which the starting dispensing position is offset from the center point of the wafer is r1, r1 = d / 2, where d is the inner diameter of the dispensing nozzle; the termination dispensing position is a position 0 - 2 mm away from the edge of the wafer.

8. The method for coating a high-viscosity photoresist according to claim 5, wherein The horizontal distance by which the starting dispensing position is offset from the center point of the wafer is r1; At the starting dispensing position, the first duration for the dispensing nozzle to dispense glue is T1; the first rotational speed of the wafer is N1, and 50 rpm < N1 < 10 rpm; the angular velocity of the wafer rotation is W1 and the linear velocity is V1; where T1 = 60 s / N1, W1 = 2π / T1, V1 = W1 * r1.

9. The method for coating a high-viscosity photoresist according to claim 8, wherein At the starting glue-dropping position, the residence time of the glue-dropping nozzle is T1', and T1' = T1 + T o , where T0 is the time for the photoresist to reach the wafer surface from the glue-dropping nozzle after the glue-dropping starts.

10. The method for coating a high-viscosity photoresist according to claim 5, characterized in that, Calculate the termination dispensing position or the number of step movements according to the following formula; r n = r1 + (n - 1)s where r n is the horizontal distance from the dispensing position where the dispensing nozzle moves one step distance to the center point of the wafer, r1 is the horizontal distance by which the starting dispensing position deviates from the center point of the wafer, s is the step distance, and n is the number of steps and is a natural number greater than or equal to 2.

11. The method for coating a high-viscosity photoresist according to claim 5, characterized in that, When the dispensing nozzle is at a dispensing position after moving one step distance, the rotation speed N of the wafer is calculated according to the following formula n , the angular velocity W of the rotation of the wafer n , the nth duration T of the dispensing nozzle for dispensing n ; N n = 60s / T n , T n = 2π / W n , W n = V n / r n ; where r n is the horizontal distance from the center point of the wafer to the dispensing position where the dispensing nozzle is located, and V n is the linear velocity at which the wafer rotates at the dispensing position, and V n is the same as the linear velocity V1 at which the wafer rotates at the starting dispensing position, and n is a natural number greater than or equal to 2.

12. The method for coating a high-viscosity photoresist according to any one of claims 1-4, characterized in that, The dispensing nozzle forms a photoresist ring on the surface of the wafer at the starting dispensing position, the termination dispensing position, and each intermediate dispensing position, and the photoresist rings formed at each dispensing position are concentrically distributed.

13. The method for coating a high-viscosity photoresist according to any one of claims 1 to 4, wherein: Before step (1), it further includes: Provide the wafer and place the wafer on a positioning carrier.

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