Method for uniformly spin-coating photoresist

Abstract

The invention discloses a photoresist uniform spin-coating method, which comprises the following steps that when a wafer rotates, photoresist is gradually dripped from the edge of the wafer to the center of the wafer through a photoresist dripping structure, in the photoresist dripping process, the moving speed of the photoresist dripping structure changes according to a certain rule, and photoresist dripping can be stopped when the photoresist dripping structure moves to the center of the wafer; and then the wafer accelerates to rotate to complete the preparation of the photoresist film. According to the photoresist uniform spin-coating method provided by the invention, when the wafer rotates, the photoresist is gradually dripped from the edge of the wafer to the center of the wafer or gradually dripped from the center of the wafer to the edge of the wafer through the photoresist dripping structure, and in the photoresist dripping process, the moving speed of the photoresist dripping structure changes according to a certain rule; according to the invention, the movement of the glue dripping position is dynamically adjusted through the movement speed of the glue dripping structure, so that the coating uniformity of the photoresist can be effectively improved, the distribution of the photoresist on the wafer is more uniform, and the problems of non-uniform coating and relatively thin edge glue thickness of a traditional snake-shaped coating method are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor packaging, and particularly relates to a method for uniformly spin-coating photoresist. Background Art

[0002] Spin coating is a common process for preparing photoresist films, which has advantages such as low cost and high speed. In the industry, a spin coater is usually used for coating. There is a mechanical swing arm in the spin coater, which drives the glue outlet to move and can freely control the position of the glue outlet. The ideal coating requirement is that the thickness of the photoresist film on the entire wafer is the same. However, it is difficult to achieve uniformity in the current spin coating process. In the traditional spin coating method, the photoresist is dropped at the center of the wafer during coating, resulting in most of the glue accumulating at the center before the rotation speed increases, causing uneven thickness. To solve the above problems, the serpentine glue dropping method came into being. The serpentine glue dropping method moves the glue dropping point through the swing arm, and the glue dropping point gradually moves from the center to the edge of the wafer while the wafer is rotating. Using the serpentine coating method can make the glue amount distribution more uniform and avoid the phenomenon of center accumulation. However, the traditional serpentine coating method also has problems:

[0003] The traditional serpentine coating moves the swing arm uniformly from the center to the edge of the wafer and discharges glue at a constant flow rate, showing an equidistant spiral. As Figure 1 shown, since the linear velocity of the wafer increases gradually with the radius during rotation, the area that a unit volume of photoresist needs to spread out also increases accordingly, resulting in a relatively thinner glue thickness at the edge of the wafer, affecting the coating uniformity. Especially when the wafer diameter is large, this problem is more prominent. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a method for uniformly spin-coating photoresist.

[0005] In order to achieve the above purpose and achieve the above technical effects, the technical solution adopted by the present invention is:

[0006] A method for uniformly spin-coating photoresist includes the following steps:

[0007] When the wafer is rotating, gradually drop the photoresist from the edge of the wafer to the center of the wafer or from the center of the wafer to the edge of the wafer. During the process of dropping the glue, dynamically adjust the movement of the glue dropping position according to the movement speed of the glue dropping structure to improve the uniformity of the distribution of the photoresist on the wafer.

[0008] In some embodiments, a method for uniformly spin-coating photoresist includes the following steps:

[0009] When the wafer is rotating, through the dispensing structure, photoresist is gradually dispensed from the edge of the wafer towards the center of the wafer. During the dispensing process, the moving speed of the dispensing structure changes according to a certain rule, and the movement of the dispensing position is dynamically adjusted according to the moving speed of the dispensing structure. When the dispensing structure moves to the center of the wafer, the dispensing immediately stops, and then the wafer accelerates rotation to complete the preparation of the photoresist film.

[0010] In some other embodiments, a method for uniformly spin-coating photoresist includes the following steps:

[0011] When the wafer is rotating, through the dispensing structure, photoresist is gradually dispensed from the center of the wafer towards the edge of the wafer. During the dispensing process, the moving speed of the dispensing structure changes according to a certain rule, and the movement of the dispensing position is dynamically adjusted according to the moving speed of the dispensing structure. After the dispensing ends, the wafer accelerates rotation to complete the preparation of the photoresist film.

[0012] Further, to ensure uniform coating of the photoresist, with the center of the wafer as the origin, the relationship between the linear velocity ω of the dispensing structure and its distance r from the center of the wafer is expressed as:

[0013]

[0014] In the formula, θ is the rotation angle of the wafer; a and b are constants used to match different wafer rotation speeds and photoresist viscosities.

[0015] Further, during the dispensing process, the moving speed v of the dispensing structure b The relationship with the position is expressed as:

[0016]

[0017] In the formula, v0 is the initial speed of the dispensing structure.

[0018] Further, during the dispensing process, the moving speed v of the dispensing structure b The relationship with time is expressed as:

[0019]

[0020] In the formula, t is the movement time of the dispensing structure.

[0021] Further, the position where the dispensing structure starts to dispense is 0 - 20 mm away from the edge of the wafer.

[0022] Further, before the wafer rotates, the wafer is first placed on a vacuum chuck, and the wafer is driven to rotate by the vacuum chuck. The diameter of the wafer is 100 - 300 mm, and the rotation speed of the wafer is 1500 - 3000 rpm.

[0023] Further, the wafer is driven by a vacuum chuck to rotate at an accelerating speed, and the rotation speed is 2000 - 5000 rpm.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention discloses a method for uniformly spin - coating photoresist. When the wafer rotates, the photoresist is gradually dropped from the edge of the wafer to the center of the wafer or from the center of the wafer to the edge of the wafer through a dispensing structure. During the dispensing process, the moving speed of the dispensing structure changes according to a certain rule, and the dispensing position is dynamically adjusted by the moving speed of the dispensing structure, which can effectively improve the uniformity of photoresist coating, make the distribution of photoresist on the wafer more uniform, and solve the problems of uneven coating and relatively thin edge glue thickness in the traditional serpentine coating method. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the photoresist distribution in the prior art;

[0027] Figure 2 is a schematic diagram of the photoresist distribution of the present invention;

[0028] Figure 3 is a curve graph of the moving speed of the dispensing structure of the present invention versus time. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0030] The following gives a brief overview of one or more aspects to provide a basic understanding of these aspects. This overview is not an exhaustive survey of all contemplated aspects, and is neither intended to identify key or decisive elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that follows.

[0031] As Figure 2-3 shown, the present invention discloses a method for uniformly spin - coating photoresist for improving the uniformity of photoresist spin - coating in the chip manufacturing process, including the following steps:

[0032] When the wafer rotates, the photoresist is gradually dropped from the edge of the wafer to the center of the wafer or from the center of the wafer to the edge of the wafer through a dispensing structure. During the dispensing process, the dispensing position is dynamically adjusted according to the moving speed of the dispensing structure. After the dispensing is completed, the wafer rotates at an accelerating speed to complete the preparation of the photoresist film.

[0033] In some embodiments, a method for uniformly spin-coating a photoresist may include the following steps:

[0034] While the wafer is rotating, the photoresist is gradually dropped from the edge of the wafer towards the center of the wafer through a dispensing structure. During the dispensing process, the moving speed of the dispensing structure changes according to a certain rule, and the movement of the dispensing position is dynamically adjusted according to the moving speed of the dispensing structure. When the dispensing structure moves to the center of the wafer, the dispensing can be stopped. Then, the wafer accelerates rotation to complete the preparation of the photoresist film.

[0035] In some other embodiments, a method for uniformly spin-coating a photoresist may include the following steps:

[0036] While the wafer is rotating, the photoresist is gradually dropped from the center of the wafer towards the edge of the wafer through a dispensing structure. During the dispensing process, the movement of the dispensing position is dynamically adjusted according to the moving speed of the dispensing structure. After the dispensing is completed, the wafer accelerates rotation to complete the preparation of the photoresist film.

[0037] In some more specific embodiments, to ensure uniform coating of the photoresist, taking the center of the wafer as the origin, the relationship between the linear velocity ω of the dispensing structure and its distance r from the center of the wafer is expressed as:

[0038]

[0039] In the formula, θ is the rotation angle of the wafer; a and b are constants used to match different wafer rotation speeds and photoresist viscosities.

[0040] During the dispensing process, the moving speed v of the dispensing structure b The relationship with the position is expressed as:

[0041]

[0042] In the formula, v0 is the initial speed of the dispensing structure.

[0043] During the dispensing process, the moving speed v of the dispensing structure b The relationship with time is expressed as:

[0044]

[0045] In the formula, t is the movement time of the dispensing structure.

[0046] Example 1

[0047] As Figure 2-3 shown, a method for uniformly spin-coating a photoresist, which is used to improve the uniformity of photoresist spin-coating in the chip manufacturing process, includes the following steps:

[0048] To avoid the photoresist at the center flowing to the uncoated position under the influence of centrifugal force during the rotation of the wafer, resulting in deviation of the film thickness, during the rotation of the wafer, the photoresist is gradually dropped from the edge of the wafer towards the center of the wafer through a dispensing structure. During the dispensing process, the moving speed of the dispensing structure changes according to a certain rule, and the dispensing position is dynamically adjusted by the moving speed of the dispensing structure. When the dispensing structure moves to the center of the wafer, the dispensing can be stopped. Then the wafer accelerates to rotate to complete the preparation of the photoresist film, which can effectively improve the uniformity of photoresist coating, make the distribution of the photoresist on the wafer more uniform, and solve the problems of uneven coating and relatively thin edge thickness in the traditional serpentine coating method.

[0049] In this embodiment, to ensure uniform photoresist coating, taking the center of the wafer as the origin, the relationship between the linear velocity ω of the dispensing structure and its distance r from the center of the wafer is expressed as:

[0050]

[0051] In the formula, θ is the rotation angle of the wafer; a and b are constants used to match different wafer rotation speeds and photoresist viscosities.

[0052] In this embodiment, during the dispensing process, the moving speed v of the dispensing structure b The relationship with the position is expressed as:

[0053]

[0054] In the formula, v0 is the initial speed of the dispensing structure.

[0055] In this embodiment, during the dispensing process, the moving speed v of the dispensing structure b The relationship with time is expressed as:

[0056]

[0057] In the formula, t is the movement time of the dispensing structure.

[0058] A method for uniformly spin-coating photoresist disclosed in this embodiment includes more specific steps:

[0059] Step 1: Place the wafer on the vacuum chuck, and drive the wafer to rotate by the vacuum chuck. Among them, the diameter of the wafer is 300 mm, and the rotation speed of the wafer is 1500 rpm - 3000 rpm;

[0060] Step 2: Move the dispensing structure to the edge of the wafer and start dropping the photoresist. The starting position for dropping the photoresist is set to be 10 mm away from the edge of the wafer;

[0061] Step 3: The dispensing structure starts to move towards the center of the wafer at a specified initial speed (1 cm / s);

[0062] Step 4: During the movement, the moving speed of the dispensing structure changes according to Formula 2 and Formula 3;

[0063] Step 5: Immediately stop dispensing when the dispensing structure moves to the center of the wafer;

[0064] Step 6: Drive the wafer to accelerate rotation by a vacuum chuck to complete the preparation of the photoresist film, and the rotation speed is 2000 rpm - 5000 rpm.

[0065] The dispensing structure described in the present invention mainly refers to the swing arm for dispensing, and existing products can be used.

[0066] For the parts or structures not specifically described in the present invention, existing technologies or existing products can be used, and no further elaboration will be made here.

[0067] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for uniformly spin-coating a photoresist, characterized in that, The method includes the following steps: When the wafer is rotating, the photoresist is gradually dropped from the edge of the wafer towards the center of the wafer or from the center of the wafer towards the edge of the wafer. During the dropping process, the dropping position movement is dynamically adjusted according to the moving speed of the dropping structure, so as to improve the uniformity of the photoresist distribution on the wafer.

2. A method for uniformly spin-coating a photoresist according to claim 1, characterized in that, The method includes the following steps: When the wafer is rotating, the photoresist is gradually dropped from the edge of the wafer towards the center of the wafer through the dropping structure. During the dropping process, the moving speed of the dropping structure changes according to a certain rule. The dropping position movement is dynamically adjusted according to the moving speed of the dropping structure. When the dropping structure moves to the center of the wafer, the dropping of the photoresist is immediately stopped, and then the wafer accelerates rotation to complete the preparation of the photoresist film.

3. A method for uniformly spin - coating a photoresist according to claim 1, characterized in that, The method includes the following steps: When the wafer is rotating, the photoresist is gradually dropped from the center of the wafer towards the edge of the wafer through the dropping structure. During the dropping process, the moving speed of the dropping structure changes according to a certain rule. The dropping position movement is dynamically adjusted according to the moving speed of the dropping structure. After the dropping is completed, the wafer accelerates rotation to complete the preparation of the photoresist film.

4. A method for uniformly spin-coating a photoresist according to claim 2 or 3, characterized in that, To ensure uniform coating of the photoresist, taking the center of the wafer as the origin, the relationship between the linear velocity ω of the dropping structure and its distance r from the center of the wafer is expressed as: In the formula, θ is the rotation angle of the wafer; a and b are constants used to match different wafer rotation speeds and photoresist viscosities.

5. A method for uniformly spin - coating a photoresist according to claim 2 or 3, characterized in that, During the dispensing process, the moving speed v of the dispensing structure b The relationship with the position is expressed as: In the formula, v0 is the initial velocity of the dropping structure.

6. A method for uniformly spin - coating a photoresist according to claim 2 or 3, characterized in that, During the epoxy resin dripping process, the moving speed v of the epoxy resin dripping structure b The relationship with time is expressed as: In the formula, t is the movement time of the dropping structure.

7. A method for uniformly spin-coating a photoresist according to claim 2, characterized in that, The position where the dropping structure starts to drop the photoresist is 0 - 20 mm away from the edge of the wafer.

8. A method for uniformly spin-coating a photoresist according to claim 1, characterized in that, Before the wafer rotates, the wafer is first placed on a vacuum chuck, and the wafer is driven to rotate by the vacuum chuck. The diameter of the wafer is 100 - 300 mm, and the rotation speed of the wafer is 1500 - 3000 rpm.

9. A method for uniformly spin - coating a photoresist according to claim 1, characterized in that, The wafer is driven to accelerate rotation by the vacuum chuck, and the rotation speed is 2000 - 5000 rpm.

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