Gluing method for leveling surface of photoresist by utilizing airflow and liquid medicine steam

Abstract

The invention relates to a gluing method for leveling the surface of photoresist by utilizing airflow and liquid medicine steam, which comprises the following steps of: temporarily storing liquid medicine in a collecting cup and forming a constant humidity state to a certain extent in a cavity by arranging a liquid level guide port with an opening height higher than the bottom surface of the collecting cup; moisture formed by the liquid medicine in the cavity is brought to the surface of the wafer through airflow generated by rotation of the wafer, and the upper surface of the photoresist of the wafer is slightly dissolved through liquid medicine steam, so that the surface is leveled, the upper surface of the photoresist is smoother, the requirements of the subsequent process can be met, and the production efficiency is improved. In addition, according to the method disclosed by the invention, parameters such as back washing rotating speed, back washing time, leveling rotating speed, leveling time, back washing liquid spray washing position and the like can be controlled, so that the surface roughness of the wafer photoresist can be improved, and meanwhile, the thickness of the photoresist can also meet normal process requirements.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically a coating method that uses airflow and chemical vapor to level the surface of photoresist. Background Technology

[0002] While existing technologies can control the airflow intensity during wafer movement to make the photoresist surface relatively smooth after coating, this cannot completely eliminate the influence of airflow on the photoresist surface. Software flow field simulations have shown that as long as the wafer moves, airflow of a certain intensity will form on its surface. This airflow will erode the photoresist surface during the coating process, resulting in an uneven surface that will affect subsequent processes.

[0003] The patent with authorization announcement number CN112748639B discloses an FFU rectifier plate with airflow partition control and a coating process for adjusting the adhesive shape. It changes the airflow environment of the coating cavity by designing a FFU rectifier plate with a specific structure, thereby realizing partition control of airflow for controlling the coating thickness at the center and edge of the wafer. However, this process is mainly used to improve the problem of coating consistency in multiple cavities. As mentioned above, since airflow will be formed on the surface of the wafer as long as it moves, the photoresist surface will still form tiny unevenness.

[0004] In addition, the collection cup of the waste liquid collection unit in the prior art cannot temporarily store the medicine. For example, the patent with authorization announcement number CN107608180B discloses a waste discharge system of multiple spinning units, in which the waste liquid in the collection cup is directly discharged into the collection box through the drain port on the lower side of the collection cup. Summary of the Invention

[0005] The purpose of this invention is to provide a coating method that uses airflow and chemical vapor to level the surface of photoresist. By setting a liquid level guide port with an opening height higher than the bottom of the collection cup, the chemical liquid is temporarily stored in the collection cup, and a certain degree of constant humidity is formed in the cavity. Then, the airflow generated by the wafer rotation carries the moisture formed by the chemical liquid in the cavity to the wafer surface, and the chemical vapor is used to slightly dissolve the upper surface of the photoresist on the wafer, so that the surface of the photoresist is leveled, thereby making the upper surface of the photoresist smoother and able to meet the requirements of subsequent processes.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for coating photoresist using airflow and chemical vapor to level the surface of photoresist includes a wafer carrier stage, and a collection cup is provided on the outer side of the wafer carrier stage. The collection cup has a liquid level guide port with an opening height higher than the bottom surface of the collection cup. The coating method includes the following steps:

[0008] Step 1: Place the wafer on the wafer carrier stage;

[0009] Step 2: The glue-applying swing arm moves above the wafer and applies glue to the wafer, while the wafer is rotated at a set speed by the wafer carrier stage.

[0010] Step 3: The wafer carrier stage drives the wafer to rotate at the back wash speed and spreads the photoresist on the surface. At the same time, the back spray device on the underside of the wafer is turned on to spray the back wash solution onto the back of the wafer.

[0011] Step 4: The wafer carrier stage drives the wafer to rotate at a leveling speed, and the liquid in the collection cup is used to form liquid vapor, which is carried to the photoresist surface by the airflow generated by the wafer rotation to achieve photoresist etching and leveling.

[0012] In step three, the back wash solution is sprayed onto the outermost position of the back wash solution pre-marked on the back of the wafer.

[0013] In step three, the backwashing speed is V1 and the backwashing time is T1. In step four, the leveling speed is V2 and V2 = V1, the leveling time is T2 and T2 is greater than T1.

[0014] The liquid level guide port has an adjustable height.

[0015] The collection cup is provided with a drain pipe on its lower side, and the lower end of the liquid level guide port is threaded into the drain pipe.

[0016] The advantages and positive effects of this invention are as follows:

[0017] 1. This invention achieves temporary storage of the medicine in the collection cup by setting a liquid level guide port with an opening height higher than the bottom surface of the collection cup, and creates a certain degree of constant humidity in the cavity. Then, the airflow generated by the wafer rotation carries the moisture formed by the medicine in the cavity to the wafer surface, and uses the medicine vapor to slightly dissolve the upper surface of the wafer photoresist, so that the surface achieves a leveling effect, thereby making the upper surface of the photoresist smoother and able to meet the requirements of subsequent processes.

[0018] 2. The method of the present invention can improve the surface roughness of the wafer photoresist by controlling parameters such as back washing speed, back washing time, leveling speed, leveling time, and back washing liquid spraying position, while ensuring that the photoresist thickness meets the normal process requirements.

[0019] 3. The present invention controls the amount of medicine in the collection cup by designing the height of the liquid level guide port, thereby controlling the concentration of medicine in the chamber. Furthermore, the liquid level guide port can be designed with an adjustable height structure, thereby flexibly adjusting the amount of medicine in the collection cup. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process of the method of the present invention.

[0021] Figure 2 This is a schematic diagram of the wafer rotation flow field simulation generated by the software.

[0022] Figure 3 This is a schematic diagram of a collection cup structure in the prior art.

[0023] Figure 4 This is a schematic diagram of the collection cup structure of the method of the present invention.

[0024] Figure 5 for Figure 4 A cross-sectional view of the cup structure in the middle.

[0025] Figure 6 This is a schematic diagram of the outermost position when the backwash solution is sprayed back in the method of the present invention.

[0026] In this diagram, 1 represents the wafer, 2 represents the wafer carrier stage, 3 represents the collection cup, 4 represents the drain pipe, 5 represents the liquid level guide port, and 6 represents the outermost position of the back wash solution. Detailed Implementation

[0027] The invention will now be described in further detail with reference to the accompanying drawings.

[0028] like Figures 1-6 As shown, the device of the present invention includes a rotatable wafer carrier stage 2, and a wafer 1 is disposed on the wafer carrier stage 2. A back spray device is provided on the lower side of the wafer 1. A collection cup 3 is provided on the outer circumference of the wafer carrier stage 2, and a drain pipe 4 is provided on the lower side of the collection cup 3. The above structures are all known technologies in the art. For example, see the structure in patent CN107608180B. Additionally, as... Figure 3 As shown, in the prior art, the drain pipe 4 is completely located below the collecting cup 3. This means the liquid medicine in the collecting cup 3 will be directly drained away through the drain pipe 4 and cannot be temporarily stored in the collecting cup 3. However, as... Figure 4 As shown, the present invention raises the height of the upper end of the drain pipe 4 to a position higher than the bottom surface of the collection cup 3, thereby forming a liquid level guide port 5 with an opening height higher than the bottom surface of the collection cup 3. In this way, after the medicine enters the collection cup 3, it will not immediately flow into the drain pipe 4 through the liquid level guide port 5, but will be temporarily stored in the collection cup 3 until the liquid level is higher than the height of the liquid level guide port 5 before flowing into the drain pipe 4 and being discharged. This ensures that a certain amount of medicine is always present in the collection cup 3.

[0029] The purpose of the above design in this invention is as follows: Figure 2As shown in the software flow field simulation, as long as the wafer moves, a certain intensity of airflow will form on its surface to erode the upper surface of the photoresist. However, if a certain amount of liquid is temporarily stored in the collection cup 3, the stored liquid will evaporate to form moisture, so that a certain degree of constant humidity is formed in the cavity. Furthermore, the liquid vapor can flow to the photoresist surface on the wafer 1 with the rising airflow formed by the wafer rotation. Then, the liquid vapor will slowly erode the upper surface of the photoresist, thereby making the upper surface of the photoresist level and obtaining better flatness.

[0030] like Figure 1 As shown, the method of the present invention includes the following steps:

[0031] Step 1: Place wafer 1 on wafer carrier stage 2 of the spin coating unit;

[0032] Step 2: The glue-applying swing arm moves to directly above the center of wafer 1 and applies glue to wafer 1. At the same time, wafer 1 is driven by wafer carrier stage 2 to rotate at a set speed.

[0033] Step 3: The wafer carrier stage 2 drives the wafer 1 to rotate at the back wash speed and spreads the photoresist on the surface. At the same time, the back spray device is turned on to spray the back wash liquid onto the back of the wafer 1.

[0034] In this step, the location and timing of the backwashing liquid sprayed by the back spray device are both required, such as... Figure 6 As shown, the backwash solution needs to be sprayed onto the outermost position 6 of the backwash solution pre-marked on the back of wafer 1; otherwise, the backwash solution will cause temperature differences in the photoresist, resulting in uneven thickness. In addition, the backwash time should not be too long, otherwise the photoresist on the wafer surface will become thinner. In this embodiment, the backwash rotation speed is 500 r / min, and the backwash time is 5 seconds.

[0035] In addition, even if some of the backwash solution is atomized into the air in this step, it will be carried to the surface of wafer 1 by the airflow generated by the rotation of wafer 1, or enter the collection cup 3. The atomized backwash solution will make the homogenizing cavity have a certain humidity to ensure the constant humidity state in the cavity.

[0036] Step 4: The wafer carrier stage 2 drives the wafer 1 to rotate at a leveling speed. At this time, a small amount of liquid in the collection cup 3 will form liquid vapor and be carried to the photoresist surface by the airflow generated by the rotation of the wafer 1 to achieve etching and leveling.

[0037] like Figure 4 As shown, this invention controls the amount of medicine stored in the collection cup 3 by designing the height of the liquid level guide port 5, thereby controlling the concentration of the medicine in the chamber. Figure 5 As shown, the liquid level guide port 5 can be designed with an adjustable height to flexibly adjust the height as needed. For example, in this embodiment, the lower end of the liquid level guide port 5 is threaded into the drain pipe 4, and its height can be changed by screwing on the liquid level guide port 5.

[0038] In this embodiment, the leveling speed is 500 r / min and the leveling time is 30 seconds.

[0039] The present invention can determine the optimal flow rate by adjusting the backwash speed and the leveling speed. The verification process of this embodiment is shown in Table 1 below:

[0040]

[0041] Table 1

[0042] As shown in Table 1 above, if the backwashing speed is too fast (No. 3), the roughness of the photoresist on the wafer surface will be improved, but the thickness will be too thin. If the backwashing speed is too slow (No. 1), the photoresist thickness will be normal, but the surface roughness will be only slightly improved. If the leveling speed is too fast (No. 7), the surface roughness of the photoresist will be improved, but the thickness will be too thin. If the leveling speed is too slow (No. 4), the photoresist thickness will be normal, but the surface roughness will be only slightly improved. In addition, if the backwashing time is too short (No. 5), the photoresist thickness will be normal, but the surface roughness will be only slightly improved. If the backwashing time is too long (No. 6), the surface roughness of the photoresist will be improved, but the thickness will be too thin. Increasing the leveling time (No. 8) will not affect the final result, while decreasing the leveling time (No. 9) will affect the final result. Therefore, according to Table 1 above, the parameter settings of No. 2 or No. 8 can be used in this embodiment.

[0043] Additionally, numbers 10 and 11 in Table 1 above are comparative examples when there is no medicine in the collection cup. The parameters of the comparative example in number 10 are the same as those in the example in number 2, but the final result is a rough photoresist surface. The comparative example in number 11 increases the backwash time. Although this can slightly improve the surface roughness, it will also result in a thinner photoresist thickness.

Claims

1. A method for coating photoresist by using airflow and chemical vapor to level the surface of photoresist, characterized in that: The device includes a wafer carrier stage (2), and a collection cup (3) is provided on the outside of the wafer carrier stage (2). The collection cup (3) has a liquid level guide port (5) with an opening height higher than the bottom surface of the collection cup (3). The adhesive application method includes the following steps: Step 1: Place the wafer (1) on the wafer carrier stage (2); Step 2: The glue-applying swing arm moves above the wafer (1) and applies glue to the wafer (1). At the same time, the wafer (1) is driven to rotate at a set speed by the wafer carrier stage (2). Step 3: The wafer carrier stage (2) drives the wafer (1) to rotate at the back wash speed and spreads the photoresist on the surface. At the same time, the back spray device on the lower side of the wafer (1) is turned on to spray the back wash liquid onto the back of the wafer (1). Step 4: The wafer carrier stage (2) drives the wafer (1) to rotate at a leveling speed, and the liquid in the collection cup (3) forms liquid vapor, which is carried to the photoresist surface by the airflow formed by the rotation of the wafer (1) to achieve photoresist erosion and leveling.

2. The coating method for leveling the photoresist surface using airflow and chemical vapor as described in claim 1, characterized in that: In step three, the back wash solution is sprayed onto the outermost position (6) of the back wash solution pre-drawn on the back of the wafer (1).

3. The coating method for leveling the photoresist surface using airflow and chemical vapor as described in claim 1, characterized in that: In step three, the backwashing speed is V1 and the backwashing time is T1. In step four, the leveling speed is V2 and V2 = V1, the leveling time is T2 and T2 is greater than T1.

4. The coating method for leveling the photoresist surface using airflow and chemical vapor as described in claim 1, characterized in that: The liquid level guide port (5) has an adjustable height.

5. The coating method for leveling the photoresist surface using airflow and chemical vapor according to claim 4, characterized in that: The collection cup (3) is provided with a drain pipe (4) on its lower side, and the lower end of the liquid level guide port (5) is threaded into the drain pipe (4).

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