A wafer protection liquid coating method and wafer

Abstract

The application relates to a wafer protection liquid coating method and a wafer. The method comprises the following steps: spraying a first preset amount of protection liquid to the center of the wafer and rotating at a first rotating speed; rotating at a second rotating speed greater than the first rotating speed to perform first drying, so that the protection liquid is spread and shaped in the central area; spraying a second preset amount of protection liquid to a concentric circular area outside the coated area and rotating at a third rotating speed greater than the first rotating speed; rotating at a fourth rotating speed greater than the third rotating speed to perform intermediate drying, so that the protection liquid is spread and shaped to the periphery; rotating at a fifth rotating speed greater than the second and fourth rotating speeds to perform final drying, so that the protection liquid uniformly covers the wafer surface; and finally, reducing the rotating speed to perform low-speed flow leveling. Through segmented glue injection, step-by-step speed increase and intermittent drying, the application realizes high uniformity coating of the protection liquid on the wafer surface, the wafer surface presents hydrophilicity after cleaning, organic matter is effectively prevented from adhering in the cutting process, and the product cleanliness and yield are improved.

Description

Technical Field

[0001] This application belongs to the field of semiconductor manufacturing, and specifically relates to a wafer coating method. Background Technology

[0002] Wafer dicing is a crucial back-end process that separates a completed front-end wafer into individual chips (dies) along the dicing ridge. Typically, a temporary protective material (coating) needs to be applied to the front side of the wafer before dicing. The conventional coating method is spin coating, which involves placing the wafer on a vacuum chuck of a spin coater, using an automatic dispenser or spray system to drip / spray the protective liquid onto the center of the wafer, then rotating at high speed to spread the protective liquid evenly under centrifugal force, forming a thin film; finally, heating with a hot plate or oven causes the solvent to evaporate, forming a dense protective film.

[0003] The wettability of the wafer surface has a significant impact on the dicing quality. If the wafer surface is not coated with a temporary protective material or the coating is uneven, the wafer surface will exhibit hydrophobic properties. This will make it very easy for a large amount of organic matter to remain on the wafer surface during the wafer dicing process. On the one hand, this restricts the stability of the dicing process and the cleanliness of the product. On the other hand, these residual organic substances are difficult to completely remove in subsequent cleaning processes, thus affecting product yield and reliability. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide a method for coating a wafer protective liquid that makes it easy to remove in subsequent wafer dicing and cleaning steps.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: by changing the traditional coating method, the hydrophilicity of the wafer surface is improved, so that the organic matter remaining on the wafer surface can better adhere to the cleaning solution (ultrapure water) in the subsequent cleaning steps, and the cleaning solution can be evenly spread, fully contact and penetrate to the interface between the organic matter residue and the wafer surface, thereby enhancing the effect of desorption, dispersion and removal of organic matter from the surface.

[0006] This application provides a method for applying a wafer protective solution, comprising the following steps: S3) Center coating: The wafer to be coated is placed in a spin coater, and a first preset amount V1 of protective liquid is sprayed onto the center of the wafer to be coated, and the wafer is rotated at a first rotation speed n1. S4) First drying: The wafer is rotated at a second speed n2, which is greater than the first speed n1, for a set time, so that the protective liquid of the first injection is initially shaped and evenly spread in the central area of ​​the wafer, thus completing the first drying; S5) Intermediate coating: On the radial outer side of the coated area on the wafer, a second preset amount V2 of protective liquid is sprayed onto a concentric circular area at a first preset radius from the center of the wafer, and rotated at a third speed n3, wherein the third speed n3 is greater than the first speed n1. S6) Intermediate drying: The wafer is rotated at a fourth speed n4, which is greater than the third speed n3, for a set time, so that the protective liquid of the intermediate coating is evenly spread to the outside and initially shaped, thus completing the intermediate drying step; S7) Final drying: The wafer is rotated at a fifth rotation speed n5 for a set time. The fifth rotation speed n5 is greater than the fourth rotation speed n4 and the second rotation speed n2, so that the protective liquid is evenly covered and spread on the surface of the wafer to achieve high-speed centrifugal drying. S8) Low-speed leveling: Reduce the rotation speed of the wafer to stabilize and level the protective liquid film.

[0007] In one specific embodiment, the coating method further includes: prior to step S3), a following is provided: S1) Pre-cleaning step: Rinse the wafer surface with cleaning solution while keeping the wafer rotating at a high speed of a first centrifugal speed n0 to remove initial contaminants from the surface; S2) Centrifugal drying step: The wafer is rotated at a second centrifugal speed n0' for a set time to remove moisture; wherein, the second centrifugal speed n0' > the first centrifugal speed n0, and the first centrifugal speed n0 > the fifth speed n5.

[0008] In one specific embodiment, the coating method includes repeating intermediate adhesive injection steps and intermediate drying steps multiple times.

[0009] In one specific embodiment, the intermediate glue injection step is repeated at least three times.

[0010] In one specific embodiment, the repeated intermediate coating steps involve coating the wafer segment by segment from the center to the edge, with the rotation speed gradually increasing each time an intermediate coating is applied.

[0011] In one specific embodiment, the annular area between two adjacent intermediate glue injection positions is equal, and the amount of glue injected in each intermediate glue injection is equal.

[0012] In one specific embodiment, when m intermediate injections are performed, the injection radius Pi of the i-th intermediate injection satisfies:

[0013] Where R is the wafer radius, i = 1, 2, ..., m.

[0014] In one specific embodiment, the central injection volume is 30ml-40ml, and the intermediate injection volume is 30ml-40ml.

[0015] In one specific embodiment, the second rotational speed n2 is greater than the fourth rotational speed n4; the second rotational speed n2 is 20 rpm / min-40 rpm / min, the fourth rotational speed n4 is 200 rpm / min-300 rpm / min, and the fifth rotational speed n5 is 550 rpm / min-1500 rpm / min.

[0016] On the other hand, this application also provides a wafer prepared by the above-mentioned wafer protective liquid coating method, wherein the water droplet angle of the wafer is <50°.

[0017] Compared with existing technologies, this application has the following advantages: By performing multiple adhesive injections and precisely controlling the position and speed of the protective liquid coating, followed by drying after each injection, the protective liquid can be evenly spread across the wafer surface in segments. Finally, a final drying step ensures uniform coating of the protective liquid, ultimately achieving a wafer surface film thickness error of <0.2μm and a water droplet angle of 22°-35°. Organic residues can be effectively removed during the cleaning process after wafer dicing. Attached Figure Description

[0018] Figure 1 A schematic diagram of the adhesive application method using existing coating techniques.

[0019] Figure 2 This is a schematic diagram of the coating method in one embodiment of this application.

[0020] Figure 3 A schematic diagram of a coating method in another embodiment provided in this application.

[0021] Figure 4 This is a schematic diagram of the selected water droplet angle test position on the wafer surface in the embodiments and comparative examples of this application.

[0022] Among them: 1. Stage; 2. Wafer; 3. Center resist; 4. Inner annular liquid band; 5. Outer annular liquid band; 7. Center; 8. Resin position. Specific Implementation

[0023] To illustrate the technical content, structural features, achieved objectives, and effects of the invention in detail, the technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. In the following description, for illustrative purposes, numerous specific details are set forth to provide a detailed description of various exemplary embodiments or implementations of the invention. However, various exemplary embodiments may also be implemented independently without these specific details or in one or more equivalent arrangements. Furthermore, the various exemplary embodiments may differ, but are not necessarily exclusive. For example, the specific shape, construction, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0024] Before wafer dicing, a polymer-based protective solution or protective film material is applied to the surface to protect it from mechanical damage, thermal damage, and contamination during the dicing process. During wafer dicing, ultrapure water is used to cool and rinse away cutting debris, while also cleaning and dissolving the water-soluble protective solution. After dicing, the chip is further cleaned and dried to remove any residual organic matter from its surface.

[0025] Figure 1 A schematic diagram of a prior art wafer protective solution coating method is shown, such as... Figure 1 As shown, wafer 2 is fixed on the stage 1 of a spin coater. An automatic dispenser drips or sprays the total amount of protective liquid onto the center of the wafer. High-speed rotation then causes the protective liquid to spread evenly under centrifugal force, forming a thin film. However, in areas with a large amount of adhesive (typically 80ml-120ml), the protective liquid is difficult to spread evenly. The figure shows a non-standard circular center adhesive application. This results in varying amounts of protective liquid on different directions of the wafer surface during high-speed rotation, ultimately leading to uneven coating. This results in some wafer surfaces having no protective liquid coating, while other areas have excessively thick coatings. When there is no protective liquid or the coating is uneven, the wafer surface becomes hydrophobic. Measuring the water droplet angle on the actual wafer surface (≥50°) and performing wafer dicing at this angle results in a large amount of organic matter adhering to the wafer surface, making subsequent dicing and cleaning processes ineffective.

[0026] Based on this, this application provides a method for coating a protective liquid on a wafer to improve the hydrophilicity of the wafer surface and make the protective liquid easier to remove.

[0027] Specifically, a method for applying a wafer protective solution includes the following steps: S1) Pre-cleaning step: Rinse the wafer surface with cleaning solution while keeping the wafer rotating at a high speed of a first centrifugal speed n0 to remove initial contaminants from the surface; Under normal circumstances, deionized water or ultrapure water is used as the cleaning solution. wait In an optional embodiment, the pre-washing time is 5-15 seconds, and the first centrifugal speed n0 is 1800-2500 rpm / min.

[0028] S2) Centrifugal drying step: The wafer is rotated at a second centrifugal speed n0' for a set time to remove moisture; wherein, the second centrifugal speed n0' > the first centrifugal speed n0, and the first centrifugal speed n0 > the fifth speed n5.

[0029] In one optional embodiment, the second centrifugal speed n0' is 2500-4000 rpm / min, and the centrifugal drying time is 10-30 s.

[0030] S3) Center coating: The wafer to be coated is placed in a spin coater, and a first preset amount V1 of protective liquid is sprayed onto the center of the wafer, while rotating at a low first speed n1. Since the amount of protective liquid sprayed at the center is only a fraction of that used in a single coating process, it is easier to concentrate the coating at the center 7 of the wafer, resulting in a smaller coverage area and making it easier to obtain a uniform protective liquid film layer in all directions.

[0031] In one optional embodiment, a first preset amount V1 of protective liquid is sprayed onto the center of the wafer to be coated, and the wafer is rotated at a low first rotation speed n1, where the first rotation speed n1 is 10-20 rpm / min.

[0032] S4) First drying: The wafer is rotated at a second speed n2, which is greater than the first speed n1, for a set time, so that the protective liquid of the first injection is initially shaped and evenly spread in the central area of ​​the wafer, thus completing the first drying.

[0033] In an optional embodiment, the second rotation speed n2 is 500-700 rpm / min and the duration is 1-2 seconds, and the first drying allows the center injection adhesive 3 to be quickly spread out.

[0034] S5) Intermediate coating: On the radial outer side of the coated area on the wafer, a second preset amount V2 of protective liquid is sprayed onto a concentric circle area at a first preset radius from the center of the wafer, and rotated at a third speed n3, where the third speed n3 is 30-60 rpm / min, for a duration of 8-12s.

[0035] S6) Intermediate drying: Rotate the wafer at the fourth rotation speed n4 for 5-15 seconds to allow the protective liquid of the intermediate coating to spread evenly to the outside and achieve preliminary shaping, thus completing the intermediate drying step. The fourth rotation speed n4 is 200-400 rpm / min. N Specifically, the coating method may include repeating intermediate adhesive application steps and intermediate drying steps multiple times. In an optional embodiment, the number of intermediate adhesive applications is greater than or equal to 2 and less than or equal to 8, typically 2-4. The more applications, the smaller the amount of adhesive applied each time, and the better the fine control of film uniformity, but at the cost of some coating efficiency.

[0036] The repeated intermediate gluing in this application involves gluing the material segment by segment from the inside out, with the rotation speed gradually increasing during each intermediate gluing to allow the protective liquid to diffuse outwards. After multiple intermediate gluings and drying, once the protective liquid film roughly covers the required gluing area, the rotation speed needs to be further increased to ensure the protective liquid film is evenly distributed in a 360° direction and to dry quickly.

[0037] S7) Final drying: The wafer is rotated at a fifth rotation speed n5 for 8-20 seconds. The fifth rotation speed n5 is 600-1500 rpm / min. The protective liquid is evenly covered and spread on the surface of the wafer. High-speed centrifugal drying is achieved under normal temperature conditions.

[0038] S8) Low-speed leveling: Reduce the rotation speed of the wafer to 10-20 rpm / min and continue for 10-20 seconds to stabilize and level the protective liquid film.

[0039] In a preferred embodiment, the annular area between two adjacent intermediate glue injection positions is approximately equal, and the amount of glue injected in each intermediate glue injection is equal.

[0040] When m intermediate injections are performed, the injection radius Pi of the i-th intermediate injection satisfies formula (1):

[0041] Where R is the wafer radius, i = 1, 2, ..., m.

[0042] The amount of adhesive injected each time = the total amount of adhesive injected / (m + 1).

[0043] In the embodiments of this application, the protective liquid comprises a water-soluble resin, polyethylene glycol, fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and pure water. The viscosity of the protective liquid is 0 mPa·s-5 mPa·s, preferably 2.2 mPa·s, 2.5 mPa·s, 2.8 mPa·s, and 3.5 mPa·s.

[0044] The wafer coated by the protective liquid coating method proposed in this application has a water droplet angle of <50°, and the water droplet angle of multi-point testing is generally between 22° and 35°. Therefore, the wafer as a whole exhibits better hydrophilicity. Example

[0045] This embodiment provides a method for applying a wafer protective liquid to uniformly coat the surface of a 12-inch (304 mm in diameter) silicon wafer to prevent organic matter from adhering during subsequent wafer dicing. The protective liquid is selected with a viscosity of 3.5 mPa·s and contains water-soluble resin, polyethylene glycol, fatty alcohol polyoxyethylene ether, and fatty alcohol polyoxyethylene ether.

[0046] (I) Preprocessing stage See Figure 2 The 12-inch silicon wafer to be coated is placed in the spin coating device, and the wafer 2 is fixed by the vacuum stage 1.

[0047] S1) Pre-cleaning step: Control the wafer 1 to rotate at a first centrifugal speed n0 = 2000 rpm / min, while simultaneously spraying deionized water as a cleaning solution onto the surface of the wafer 2 through a nozzle for 10 seconds to remove initial particulate contaminants from the wafer surface.

[0048] S2) Centrifugal drying step: Stop spraying the cleaning solution and increase the wafer rotation speed to the second centrifugal speed n0' = 3000 rpm, and continue rotating for 20 seconds to dry the residual moisture on the wafer surface, preparing it for subsequent coating. At this point, the wafer surface is in a clean, hydrophilic state.

[0049] (II) Coating Stage This embodiment employs a three-stage adhesive application method, with each application containing an equal volume of 40 ml, for a total protective solution volume of 120 ml. The application rate is 3.0 ml / s. The application locations are determined using the equal area distribution method.

[0050] Calculation of glue injection location: The wafer radius R = 152 mm, the total number of encapsulation injections is 3, the intermediate encapsulation injections m = 2, the encapsulation radius position of each injection is calculated according to formula (1), and the position of each encapsulation injection is shown in Table 1:

[0051] S3) Center injection: Control the wafer to rotate at a first speed n1=10rpm, move the nozzle to directly above the center of the wafer, and spray a first preset amount V1=40ml of protective liquid onto the center of the wafer to form the center injection 3.

[0052] S4) First drying: Increase the wafer rotation speed to a second speed n2=600rpm / min and continue rotating for 1 second. This allows the protective liquid for the center coating to spread evenly in the central area of ​​the wafer (within a radius of approximately 0-60mm) under centrifugal force, thus achieving initial shaping.

[0053] S5) First intermediate injection: Adjust the wafer rotation speed to the third speed n3=40rpm / min, move the nozzle to a position 87.8mm away from the center of the wafer, and spray the second preset amount V2=40ml of protective liquid along the concentric circle trajectory. The dispensing time is 10s. Since the wafer is in a low-speed rotation state, the protective liquid forms an inner annular liquid band 4 at the dispensing point.

[0054] S6) First intermediate drying: Increase the wafer rotation speed to the fourth speed n4=300rpm / min and continue rotating for 10 seconds to allow the protective liquid from the first intermediate coating to spread evenly to the periphery (covering an area with a radius of about 88-124mm) and achieve initial shaping.

[0055] Repeat the intermediate injection and intermediate drying steps: Second intermediate encapsulation: The wafer rotation speed is 55 rpm / min, the nozzle is moved to a position 124.1 mm away from the center of the wafer, the encapsulation volume is 40 ml, the encapsulation time is 10 s, forming an outer ring liquid band 5.

[0056] Second intermediate drying: wafer rotation speed is 300 rpm / min, duration is 10 seconds.

[0057] S7) Final drying: The wafer rotation speed is increased to the fifth speed n5 = 900 rpm / min and rotated continuously for 10 seconds. Under the action of high-speed centrifugal force, the protective liquids from each injection merge and uniformly cover the entire wafer surface (radius 0-304 mm), causing the solvent in the protective liquid to evaporate and forming a protective film of uniform thickness.

[0058] S8) Low-speed leveling: The wafer rotation speed was reduced to 20 rpm / min and rotated continuously for 10 seconds to eliminate airflow disturbances caused by high-speed rotation, making the surface of the protective liquid film layer smoother and reducing defects.

[0059] The parameters for the entire glue injection process are shown in Table 2:

[0060] (III) Coating effect test The 12-inch wafer coated using the above method is then tested in the following ways: Film thickness uniformity test: Take 5 points on the wafer surface (see...) Figure 4The film thickness was measured at points A1, A2, A3, A4, and A5. The measurement results are shown in Table 3. The film thickness error at each measurement point was calculated to be <0.2 μm.

[0061]

[0062] Water droplet angle test: After coating and standard cleaning process, the water droplet angle on the wafer surface is 22°-35°, which shows hydrophilicity.

[0063] Organic residue test after dicing: After cleaning with ultrapure water, no organic residue was observed on the surface of the wafer coated by this method, indicating that it was clean. Comparative Example

[0064] Using the existing one-time center-filling method, only one center-filling (80ml) is performed, spread at 500rpm for 5 seconds, and then dried at 2000rpm for 15 seconds.

[0065] Measure separately Figure 4 The film thickness at points A1-A5 is uniform with a thickness of 7.5% (the thickness at the edge of the film is less than the thickness at the center).

[0066] After drying, the water droplet angles at points A1-A5 were measured. All angles were greater than 61°, indicating hydrophobicity. Furthermore, uneven coating resulted in some areas not being fully covered by the protective solution. After rinsing with ultrapure water, significant contamination and organic residue were visible on the surface, making cleaning difficult.

[0067] The water droplet angles at points A1-A5 in Example 1 and the comparative example are shown in Table 4.

[0068]

[0069] As can be seen from the table above, the coating method of this application can effectively improve the hydrophilicity of the wafer and reduce the water droplet angle, providing a favorable basis for the smooth removal of organic contaminants in subsequent cutting and cleaning processes.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. The scope of protection of the present invention is defined by the appended claims, specification, and their equivalents.

Claims

1. A method for applying a wafer protective solution, characterized in that, Includes the following steps: S3) Center coating: The wafer to be coated is placed in a spin coater, and a first preset amount V1 of protective liquid is sprayed onto the center of the wafer to be coated, and the wafer is rotated at a first rotation speed n1. S4) First drying: The wafer is rotated at a second speed n2, which is greater than the first speed n1, for a set time, so that the protective liquid of the first injection is initially shaped and evenly spread in the central area of ​​the wafer, thus completing the first drying; S5) Intermediate coating: On the radial outer side of the coated area on the wafer, a second preset amount V2 of protective liquid is sprayed onto a concentric circular area at a first preset radius from the center of the wafer, and rotated at a third speed n3, wherein the third speed n3 is greater than the first speed n1. S6) Intermediate drying: The wafer is rotated at a fourth speed n4, which is greater than the third speed n3, for a set time, so that the protective liquid of the intermediate coating is evenly spread to the outside and initially shaped, thus completing the intermediate drying step; S7) Final drying: The wafer is rotated at a fifth rotation speed n5 for a set time. The fifth rotation speed n5 is greater than the fourth rotation speed n4 and the second rotation speed n2, so that the protective liquid is evenly covered and spread on the surface of the wafer to achieve high-speed centrifugal drying. S8) Low-speed leveling: Reduce the rotation speed of the wafer to stabilize and level the protective liquid film.

2. The coating method according to claim 1, characterized in that, Before step S3), there is also: S1) Pre-cleaning step: Rinse the wafer surface with cleaning solution while keeping the wafer rotating at a high speed of a first centrifugal speed n0 to remove initial contaminants from the surface; S2) Centrifugal drying step: The wafer is rotated at a second centrifugal speed n0' for a set time to remove moisture; wherein, the second centrifugal speed n0' > the first centrifugal speed n0, and the first centrifugal speed n0 > the fifth speed n5.

3. The coating method according to claim 1, characterized in that, The coating method includes repeating intermediate adhesive injection steps and intermediate drying steps multiple times.

4. The coating method according to claim 3, characterized in that, The intermediate glue injection step is repeated at least three times.

5. The coating method according to claim 3, characterized in that, The repeated intermediate coating process involves coating the wafer segment by segment from the center to the edge, with the rotation speed gradually increasing during each intermediate coating process.

6. The coating method according to claim 3, characterized in that, The annular area between two adjacent intermediate glue injection positions is equal, and the amount of glue injected in each intermediate glue injection is equal.

7. The coating method according to claim 3 or 6, characterized in that, When m intermediate injections are performed, the injection radius Pi of the i-th intermediate injection satisfies: Where R is the wafer radius, i = 1, 2, ..., m.

8. The coating method according to claim 1 or 3, characterized in that, The central injection volume is 30ml-40ml, and the intermediate injection volume is 30ml-40ml.

9. The coating method according to claim 1, characterized in that, The second rotational speed n2 is greater than the fourth rotational speed n4; the second rotational speed n2 is 20 rpm / min-40 rpm / min, the fourth rotational speed n4 is 200 rpm / min-300 rpm / min, and the fifth rotational speed n5 is 550 rpm / min-1500 rpm / min.

10. A wafer, characterized in that: The wafer is prepared by any one of the methods of claims 1-9, and the water droplet angle of the wafer is <50°.

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