A novel dielectric layer coating method

Abstract

The application discloses a novel dielectric layer coating method and belongs to the field of semiconductor device manufacturing.The method comprises the following steps: step one, preparing a wafer, fixing the wafer on a carrier, and rotating the wafer through the carrier; step two, maintaining the rotating speed of the carrier at a first rotating speed, and spraying photoresist on the surface of the wafer through a photoresist nozzle; step three, increasing the rotating speed of the carrier to a second rotating speed, and then increasing the rotating speed to a third rotating speed, so that the photoresist is uniformly spread; step four, increasing the rotating speed of the carrier to a fourth rotating speed, so that the photoresist is rapidly spun off and completely covers the surface of the wafer; and step five, decreasing the rotating speed of the carrier to a fifth rotating speed, so that the photoresist is formed into a film. The application can improve the problem of high edge film thickness of high-viscosity polyimide in the preparation of low film thickness dielectric layers, effectively improve the film thickness uniformity, and thus improve the quality and yield of product bump packaging, and can be widely applied to various bump packaging fields.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing technology, specifically referring to a novel dielectric layer coating method. Background Technology

[0002] Photosensitive polyimide is a polymer material that combines the excellent physical and chemical properties of polyimide with the characteristics of photosensitive materials. It features good thermal stability, excellent dielectric properties, high mechanical strength, and strong chemical stability. Photosensitive polyimide is widely used in semiconductor wafer-level packaging, primarily as a passivation layer on the chip surface and as a dielectric material for redistribution layers. However, due to the high viscosity of photosensitive polyimide photoresist, it tends to accumulate at the wafer edges when coating low-thickness films, resulting in higher edge film thickness and poor overall film thickness uniformity, leading to quality defects. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, this invention provides a novel dielectric layer coating method, which effectively solves the problem that photosensitive polyimide photoresist on the market is prone to material accumulation at the wafer edge in low film thickness coating processes of semiconductor wafer-level packaging due to its high viscosity, resulting in higher edge film thickness, poor overall film thickness uniformity, and ultimately abnormal product quality.

[0004] The technical solution adopted by the present invention is as follows: The present invention proposes a novel dielectric layer coating method, the first step of which is to prepare a wafer, fix the wafer on a stage, and drive the wafer to rotate through the stage;

[0005] Step 2: Maintain the stage rotation speed at the first speed and spray photoresist onto the wafer surface through the photoresist nozzle;

[0006] Step 3: Increase the stage speed to the second speed, and then increase the speed to the third speed to spread the photoresist evenly;

[0007] Step 4: Increase the stage rotation speed to the fourth speed to allow the photoresist to be quickly spread and completely cover the surface of the wafer;

[0008] Step 5: Reduce the stage rotation speed to the fifth speed to allow the photoresist to form a film;

[0009] Step Six: Reduce the stage rotation speed to the sixth speed, move the liquid nozzle to the edge of the wafer, and thin the photoresist at the edge.

[0010] Step 7: The stage rotation speed is increased to the seventh speed to fill the photoresist area at the edge.

[0011] Preferably, in step five, the fifth rotation speed is the film-forming rotation speed, the fifth rotation speed ranges from 2500 to 4500 RPM, and the duration of the fifth rotation speed ranges from 10 to 100 seconds.

[0012] Preferably, in step six, the sixth rotational speed range is 600-1000 RPM, and the duration of the sixth rotational speed is 5-20 seconds.

[0013] Preferably, in step six, the flow rate of the liquid medicine nozzle is in the range of 20-30 ml / min, the angle between the liquid medicine nozzle and the wafer is in the range of 50-70°, and the distance between the liquid medicine nozzle and the wafer is in the range of 1-1.5 cm.

[0014] Preferably, in step two, the first rotational speed is 50 RPM, and the duration of the first rotational speed is 30 seconds.

[0015] Preferably, in step three, the second rotational speed range is 300-500 RPM, and the duration of the second rotational speed is 5 seconds.

[0016] Preferably, in step three, the third rotational speed is 1500 RPM, and the duration of the third rotational speed is 5 seconds.

[0017] Preferably, in step four, the fourth rotational speed is 2000 RPM, and the duration of the fourth rotational speed is 10 seconds.

[0018] Preferably, in step seven, the seventh rotational speed range is 1000-2000 RPM, and the duration of the seventh rotational speed is 5-20 seconds.

[0019] Preferably, in step one, the rotational speed of the stage is in the range of 100-300 RPM, and the duration of the rotational speed is 5-10 seconds.

[0020] The beneficial effects of the present invention using the above structure are as follows: This solution proposes a novel dielectric layer coating method. By moving the liquid nozzle to the edge of the wafer to thin the photoresist, and controlling the stage rotation speed and rotation time to allow the photoresist to flow and fill again, it achieves precise correction and surface re-filling of the high photoresist thickness area at the edge. This method can improve the problem of high photoresist thickness at the edge when preparing low-thickness dielectric layers with high-viscosity polyimide, effectively improve the uniformity of photoresist thickness, and thus improve the quality and yield of bump packaging products. It can be widely used in various back-end bump packaging fields. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of step one of the novel dielectric layer coating method proposed in this invention;

[0022] Figure 2 This is a schematic diagram of step one of the novel dielectric layer coating methods proposed in this invention;

[0023] Figure 3 This is a schematic diagram of step two of a novel dielectric layer coating method proposed in this invention;

[0024] Figure 4 This is a schematic diagram of step two of the novel dielectric layer coating method proposed in this invention;

[0025] Figure 5 This is a schematic diagram of step three of a novel dielectric layer coating method proposed in this invention;

[0026] Figure 6 This is a schematic diagram of step three of a novel dielectric layer coating method proposed in this invention;

[0027] Figure 7 This is a schematic diagram of step four of a novel dielectric layer coating method proposed in this invention;

[0028] Figure 8 This is a schematic diagram of step four of a novel dielectric layer coating method proposed in this invention.

[0029] Figure 9 This is a schematic diagram of step five of the novel dielectric layer coating method proposed in this invention;

[0030] Figure 10 This is a schematic diagram of step five of the novel dielectric layer coating method proposed in this invention;

[0031] Figure 11 This is a schematic diagram of step six of a novel dielectric layer coating method proposed in this invention;

[0032] Figure 12 This is a schematic diagram of step six of a novel dielectric layer coating method proposed in this invention;

[0033] Figure 13 This is a schematic diagram of step seven of a novel dielectric layer coating method proposed in this invention;

[0034] Figure 14 This is a schematic diagram of step seven of a novel dielectric layer coating method proposed in this invention.

[0035] Among them, 1. wafer; 2. stage; 3. photoresist; 4. photoresist nozzle; 5. chemical nozzle.

[0036] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] like Figures 1-14 As shown, this invention proposes a novel dielectric layer coating method, such as... Figures 1-2 As shown, the process includes step one: preparing wafer 1, placing wafer 1 on stage 2 and fixing it, stage 2 rotating wafer 1 at a speed of 100-300 RPM, with the rotation direction of stage 2 being clockwise, for a duration of 5-10 seconds. This allows wafer 1 to adapt to the rotation state and be evenly stressed, while also initially removing tiny dust and impurities adhering to the surface of wafer 1, reducing the impact of impurities on subsequent photoresist coating. At the same time, the pre-rotation ensures that the surface of wafer 1 is evenly stressed, avoiding local stress concentration that could damage wafer 1. This provides a stable and flat working reference for subsequent speed adjustments and photoresist spraying, ensuring the consistency of the coating process.

[0040] like Figures 3-4 As shown, in step two: the stage 2 maintains a rotation speed of 50 RPM while photoresist 3 is sprayed onto the surface of wafer 1 through the photoresist nozzle 4. In some preferred embodiments, the first rotation speed is 50 RPM, the duration of the first rotation speed is 30 seconds, the photoresist nozzle 4 is located above the center of wafer 1, and the photoresist 3 is sprayed vertically downwards. The distance between the exit of the photoresist nozzle 4 and the surface of wafer 1 is maintained at 1-1.5 cm. This avoids the photoresist being quickly scattered immediately after being sprayed due to excessively high rotation speed, ensuring that the photoresist can be deposited stably and uniformly in the central area of ​​wafer 1, forming an initial photoresist accumulation layer, laying a sufficient material basis for subsequent diffusion to the edges.

[0041] like Figures 5-6As shown, step three involves increasing the rotation speed of stage 2 to the second speed and maintaining it for a period of time, then increasing the speed to the third speed and maintaining it for a period of time. The speed is gradually increased from low to high, using a stepped speed control setting. This allows the photoresist 3 to spread evenly from the center to the edge under the action of centrifugal force, avoiding uneven diffusion, streaks, or gaps caused by a sudden increase in speed. In some preferred embodiments, the second speed range is 300-500 RPM, and the duration of the second speed is 5 seconds. This allows for a smooth initial diffusion of the photoresist 3 from the center to the edge, breaking the initial accumulation state and ensuring that the photoresist 3 evenly covers the lower part of the wafer 1, avoiding premature accumulation at the edges caused by direct high-speed rotation. The third speed is increased to 1500 RPM, and the duration of the third speed is 5 seconds. This further increases the centrifugal force, pushing the photoresist 3 to spread rapidly towards the edge of the wafer 1, filling the gaps in the edge area of ​​the wafer. At the same time, the photoresist 3 is initially smoothed under the action of centrifugal force, reducing surface unevenness and preparing for subsequent complete coverage and film formation.

[0042] like Figures 7-8 As shown, step four involves increasing the rotation speed of stage 2 to the fourth rotation speed and maintaining it for a period of time. This allows the photoresist 3 to be rapidly spread and completely cover the entire surface of wafer 1 under strong centrifugal force. In some preferred embodiments, the rotation speed of stage 2 is increased to the fourth rotation speed of 2000 RPM, and the duration of the fourth rotation speed is 10 seconds. This generates sufficient centrifugal force to push the photoresist 3 rapidly towards the outermost edge of wafer 1, thoroughly filling the edge areas not covered in the first three steps. This ensures that the photoresist 3 completely covers the entire surface of wafer 1 without any exposed areas, preventing defects in uncovered areas during subsequent processes. Simultaneously, the high-speed centrifugal force further smooths out the minute textures on the photoresist surface, reducing surface flatness errors and allowing the photoresist to initially form a continuous and flat film. This lays the foundation for film thickness control in subsequent film deposition stages and avoids exposure and development failures due to incomplete coverage.

[0043] like Figures 9-10As shown, step five: The rotation speed of stage 2 is reduced to the fifth rotation speed and maintained for a period of time, allowing the photoresist 3 to solidify into a film under the synergistic effect of centrifugal force and solvent evaporation. In some preferred embodiments, the fifth rotation speed is the film-forming speed, ranging from 2500-4500 RPM, and the duration of the fifth rotation speed ranges from 10-100 seconds. The specific rotation speed and time can be precisely controlled according to the target film thickness. The higher the rotation speed and the longer the time, the thinner the film thickness, achieving precise control of the film thickness and meeting the requirements of different processes for photoresist film thickness. The synergistic effect of centrifugal force and solvent evaporation allows the solvent in the photoresist 3 to evaporate evenly, while the centrifugal force continuously smooths the film, allowing the film to form a film with uniform thickness and a smooth surface, improving the density of the film and avoiding defects such as bubbles and pinholes. The phenomenon that the film thickness at the edge is slightly higher than that at the center is a normal phenomenon in centrifugal coating. Subsequent steps can make targeted corrections, which not only ensures the film thickness accuracy in the central area but also leaves a reasonable margin for edge correction, avoiding problems such as the film being too thin or damaged at the edges due to excessive thickness control.

[0044] like Figures 11-12 As shown, step six: reduce the rotation speed of stage 2 to the sixth rotation speed and maintain it for a period of time, move the chemical nozzle 5 to the edge of wafer 1, and thin the photoresist 3 at the edge of wafer 1. In some preferred embodiments, the sixth rotation speed ranges from 600 to 1000 RPM, and the duration of the sixth rotation speed is 5 to 20 seconds. The chemical flow rate of the chemical nozzle 5 ranges from 20 to 30 ml / min, the angle between the chemical nozzle 5 and wafer 1 ranges from 50 to 70°, and the distance between the outlet of the chemical nozzle 5 and the surface of wafer 1 ranges from 1 to 1.5 cm.

[0045] It should be noted that film thickness distribution data of the edge region of wafer 1 is obtained through film thickness measurement equipment to determine the specific location and width range of the area with excessive film thickness. Subsequently, the rotation speed of stage 2 is reduced to the range of 600-1000 RPM. This rotation speed ensures stable rotation of the edge region of wafer 1, which facilitates the precise application of the edge cleaning solution to the area with excessive film thickness, while avoiding excessive rotation speed which would cause the edge cleaning solution to splash and affect the film in the central area, or excessive rotation speed which would cause the edge cleaning solution to not spread evenly and result in poor correction effect. Next, the chemical nozzle 5 is moved above the area with excessive film thickness. The chemical nozzle 5 precisely controls the amount of edge cleaning solution used at a flow rate of 20-30 ml / min, avoiding excessive use which would cause the edge film to be too thin and damaged, or insufficient use which would not achieve the desired thinning effect. The cleaning nozzle 5 can maintain an angle of 50-70° and a height of 1-1.5cm with the surface of wafer 1. The 50-70° angle ensures that the edge cleaning solution is accurately sprayed on the area where the film thickness is too high at the edge and can evenly cover the area, so as to achieve precise thinning of the film with excessive thickness at the edge and correct the difference in film thickness between the edge and the center. At the same time, maintaining a distance of 1-1.5cm from the surface of wafer 1 can prevent the edge cleaning solution from splashing into the center area of ​​the wafer, thus protecting the integrity and thickness accuracy of the film in the center area.

[0046] like Figures 13-14 As shown, step seven: The rotation speed of stage 2 is increased to the seventh rotation speed and maintained for a period of time, allowing the photoresist 3 area at the edge to flow again and fill the gap. In some preferred embodiments, the seventh rotation speed ranges from 1000 to 2000 RPM, and the duration of the seventh rotation speed is 5 to 20 seconds. After the edge thinning is completed in step six, there may be microscopic bumps, flow marks, or residual edge washing solution on the surface of the photoresist 3 in the edge area. The centrifugal force generated by increasing the rotation speed can push the photoresist in the edge thinning area to flow again and fill the gap, eliminating the microscopic bumps and lines that may appear in the edge area after edge washing. At the same time, it further smooths the photoresist film on the entire wafer surface, making the film thickness at the edge and center more consistent, and finally forming a uniform, smooth, dense, and defect-free photoresist film layer. This step can completely correct the problem of excessive edge film thickness that occurred in step five, ensuring the consistency of photoresist film thickness across the entire wafer surface. At the same time, by reflowing the photoresist, it fills any possible micro-pinholes and voids, improving the quality of the film and providing a high-quality film substrate for subsequent exposure, development, and other processes. This effectively reduces the defect rate in subsequent processes and improves the overall process stability.

[0047] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0049] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A novel dielectric layer coating method, characterized in that: The novel dielectric layer coating method includes the following steps: Step 1: Prepare the wafer (1), fix the wafer (1) on the stage (2), and rotate the wafer (1) by the stage (2); Step 2: Maintain the stage (2) at the first rotation speed and spray photoresist (3) onto the surface of the wafer (1) through the photoresist nozzle (4). Step 3: Increase the rotation speed of the stage (2) to the second rotation speed, and then increase the rotation speed to the third rotation speed to spread the photoresist (3) evenly. Step 4: Increase the rotation speed of the stage (2) to the fourth rotation speed so that the photoresist (3) can be quickly thrown off and completely cover the surface of the wafer (1); Step 5: Reduce the rotation speed of the stage (2) to the fifth rotation speed to allow the photoresist (3) to form a film; Step 6: Reduce the rotation speed of the stage (2) to the sixth rotation speed, move the liquid nozzle (5) to the edge of the wafer (1), and thin the photoresist (3) at the edge. Step 7: The rotation speed of the stage (2) is increased to the seventh rotation speed so that the photoresist (3) area at the edge position is filled.

2. The novel dielectric layer coating method according to claim 1, characterized in that: In step five, the fifth rotation speed is the film-forming rotation speed, the fifth rotation speed ranges from 2500 to 4500 RPM, and the duration of the fifth rotation speed ranges from 10 to 100 seconds.

3. The novel dielectric layer coating method according to claim 1, characterized in that: In step six, the sixth rotational speed range is 600-1000 RPM, and the duration of the sixth rotational speed is 5-20 seconds.

4. The novel dielectric layer coating method according to claim 1, characterized in that: In step six, the liquid flow rate of the liquid nozzle (5) is 20-30 ml / min, the angle between the liquid nozzle (5) and the wafer (1) is 50-70°, and the distance between the liquid nozzle (5) and the wafer (1) is 1-1.5 cm.

5. The novel dielectric layer coating method according to claim 1, characterized in that: In step two, the first rotational speed is 50 RPM, and the duration of the first rotational speed is 30 seconds.

6. The novel dielectric layer coating method according to claim 1, characterized in that: In step three, the second rotational speed range is 300-500 RPM, and the duration of the second rotational speed is 5 seconds.

7. The novel dielectric layer coating method according to claim 1, characterized in that: In step three, the third rotational speed is 1500 RPM, and the duration of the third rotational speed is 5 seconds.

8. The novel dielectric layer coating method according to claim 1, characterized in that: In step four, the fourth rotational speed is 2000 RPM, and the duration of the fourth rotational speed is 10 seconds.

9. The novel dielectric layer coating method according to claim 1, characterized in that: In step seven, the seventh rotational speed range is 1000-2000 RPM, and the duration of the seventh rotational speed is 5-20 seconds.

10. A novel dielectric layer coating method according to claim 1, characterized in that: In step one, the rotational speed of the stage (2) is in the range of 100-300 RPM, and the duration of the rotational speed is 5-10 seconds.

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