Photoresist coating method

Abstract

The invention provides a photoresist coating method, which comprises the following steps of: before spraying photoresist to the central position of a wafer, selecting a target position between the center of the wafer and the edge of the wafer, firstly spraying the photoresist between the center of the wafer and the target position of the wafer, and continuously independently spraying the photoresist to the target position of the wafer; the rotating speed of the wafer is controlled to prevent the photoresist from gathering and prevent the photoresist from being thrown out of the surface of the wafer to cause waste, so that uniform photoresist film thickness is formed on the surface of the wafer with different heights, the photoresist is reduced and even prevented from forming inclined grains along the edge of the high step, and the preparation efficiency of the device is improved; meanwhile, nonuniform exposure pattern line width caused by nonuniform photoresist thickness can be reduced or even avoided, so that the influence on the performance and yield of the device caused by nonuniform exposure pattern line width is reduced or even avoided.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor integrated circuit manufacturing, and in particular to a photoresist coating method. Background Art

[0002] Photolithography is a process that uses the principle of photochemical reaction to transfer the pattern prepared on the mask to the substrate. In the photolithography process, the quality of photoresist coating directly affects the quality of photolithography. Commonly used photoresist coating methods include: spin coating, spray coating, roll coating, immersion and pull-up. The photolithography process spin coating is a spin coating process that sprays photoresist to the center of the wafer and rotates the wafer at high speed to form a film of photoresist on the surface of the wafer.

[0003] In the complete process of integrated circuit manufacturing, multiple layers of photolithography are required, and the patterns and substrates of each layer of photolithography are different. Due to the superposition of multiple layers of substrates and the uneven distribution of patterns, the surface morphology of the substrate of the rear film layer has height differences when the photoresist is applied. Especially when the height difference reaches more than 3μm, the photoresist is easy to form diagonal lines along the edge of the high step, but this phenomenon is not easy to distinguish with the naked eye. Only when the target device is subjected to a checkerboard pattern (CP) electrical test to visualize the electrical properties, it is easier to find the diagonal lines caused by this, which greatly reduces the preparation efficiency of the device and affects the performance and yield of the device. In addition, when the photoresist is applied to the substrate of the wafer, it will be unevenly distributed according to the height difference of the wafer surface morphology, resulting in the phenomenon that the photoresist is thick in the center and thin at the edge. Due to the existence of standing wave effect and bulk effect, the line width of the pattern with the same design line width exposed on photoresists of different thicknesses will be different. Therefore, the uneven surface morphology inside the exposure surface will affect the uniformity of the line width of the exposure pattern on the wafer, affecting the performance and yield of the device. Summary of the invention

[0004] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a photoresist coating method for solving the problem in the prior art that when the surface morphology of the substrate has height differences due to the superposition of multiple layers of substrates and the sparse and dense distribution of patterns, the photoresist is prone to form diagonal lines along the edges of high steps, and the photoresist coating is easily uneven, resulting in uneven exposure pattern line width, reducing the preparation efficiency of the device and affecting the performance and yield of the device.

[0005] To achieve the above-mentioned object and other related objects, the present invention provides a photoresist coating method, the coating method comprising:

[0006] S1, controlling the wafer to rotate at a first speed, and placing the nozzle at a first preset height at the center of the wafer surface to start spraying photoresist, and during the spraying process, the nozzle is kept at the first preset height and moves at a uniform speed along the radial direction of the wafer to stop above a target position on the wafer surface; wherein, during this process, the nozzle sprays the photoresist at a first preset dose, and the target position is located between the center of the wafer and the edge of the wafer;

[0007] S2, controlling the wafer to rotate at a second rotation speed, while keeping the spray head stationary at the target position and continuing to spray the photoresist at a second preset dose;

[0008] S3, closing the nozzle to stop spraying the photoresist, while keeping the wafer rotating at the second speed, during which the nozzle is moved from the target position to the first preset height at the center of the wafer surface;

[0009] S4, controlling the wafer to rotate at a third rotation speed, opening the nozzle and starting to spray the photoresist at a third preset dose; wherein the third preset dose is greater than the first preset dose and the second preset dose, and the third rotation speed is greater than the first rotation speed and the second rotation speed.

[0010] Optionally, the nozzle is set on a glue spraying arm, and the movement of the nozzle is controlled by the glue spraying arm. The movement process of moving the nozzle from the target position to the center position of the wafer surface in step S3 is: lift the glue spraying arm to place the nozzle at a second preset height above the wafer, and then control the glue spraying arm to drive the nozzle to move from the second preset height above the target position to above the center position of the wafer, and then control the glue spraying arm to place the nozzle at the first preset height, wherein the second preset height is greater than the first preset height.

[0011] Optionally, the second preset dose is greater than the first preset dose.

[0012] Optionally, before spraying the first preset dose of photoresist on the wafer surface, the method further includes the following steps:

[0013] Determining the total amount of the photoresist sprayed;

[0014] The first preset amount, the second preset amount and the third preset amount are determined according to the total spraying amount and the spraying ratio of the first preset amount, the second preset amount and the third preset amount.

[0015] Optionally, the spraying ratio of the first preset dose, the second preset dose and the third preset dose is (0.8-1.2):(2.5-3.5):(5.5-6.5).

[0016] Optionally, the first rotational speed is greater than the second rotational speed.

[0017] Further, the first rotational speed is 1000 rpm / s to 1300 rpm / s, the second rotational speed is 600 rpm / s to 800 rpm / s, and the third rotational speed is 3500 rpm / s to 4500 rpm / s.

[0018] Optionally, the target position is a circular ring area on the wafer surface where a radius of one third to two thirds of the wafer is located.

[0019] Optionally, when spraying the first preset dose, the second preset dose and the third preset dose of photoresist, the spraying speed of the nozzle is kept unchanged.

[0020] Optionally, in step S3, the time for which the wafer rotates at the second rotation speed is 2s to 3s.

[0021] As described above, before spraying photoresist onto the center position of the wafer, the photoresist coating method of the present invention selects a target position between the center of the wafer and the edge of the wafer, first sprays photoresist between the center of the wafer and the target position of the wafer, and continues to spray photoresist separately on the target position of the wafer, and controls the rotation speed of the wafer to prevent photoresist aggregation, while preventing photoresist from being thrown off the wafer surface and causing waste, so that a uniform photoresist film thickness is formed on the wafer surface with height differences, reducing or even avoiding the formation of twill lines along the edge of the high step of the photoresist, improving the preparation efficiency of the device, and at the same time can reduce or even avoid the uneven exposure pattern line width caused by uneven photoresist thickness, thereby reducing or even avoiding the impact on the performance and yield of the device caused by this. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a schematic flow chart of the photoresist coating method of the present invention.

[0023] Figure 2 and Figure 3 Shown as the present invention Figure 1 Schematic diagram of steps S1 to S2 in FIG.

[0024] Figure 4 A schematic diagram showing the target position of photoresist coating according to the present invention is shown.

[0025] Figure 5 and Figure 6 Shown as the present invention Figure 1 Schematic diagram of step S3 in FIG.

[0026] Figure 7 Shown as the present invention Figure 1 Schematic diagram of step S4 in FIG.

[0027] Figure 8 It is a schematic diagram showing closing the nozzle and stopping spraying photoresist after step S4 of the present invention.

[0028] Component number description

[0029] 1 Wafer

[0030] 11 Target Location

[0031] 2 Glue spraying arm

[0032] 3 Nozzles

[0033] 4 Photoresist

[0034] Steps S1 to S4 DETAILED DESCRIPTION

[0035] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] See also Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0037] like Figure 1 The present embodiment provides a photoresist coating method, the coating method comprising:

[0038] S1, controlling the wafer to rotate at a first speed, and placing the nozzle at a first preset height at the center of the wafer surface to start spraying photoresist, and during the spraying process, the nozzle is kept at the first preset height and moves at a uniform speed along the radial direction of the wafer to stop above a target position on the wafer surface; wherein, during this process, the nozzle sprays the photoresist at a first preset dose, and the target position is located between the center of the wafer and the edge of the wafer;

[0039] S2, controlling the wafer to rotate at a second rotation speed, while keeping the spray head stationary at the target position and continuing to spray the photoresist at a second preset dose;

[0040] S3, closing the nozzle to stop spraying the photoresist, while keeping the wafer rotating at the second speed, during which the nozzle is moved from the target position to the first preset height at the center of the wafer surface;

[0041] S4, controlling the wafer to rotate at a third rotation speed, opening the nozzle and starting to spray the photoresist at a third preset dose; wherein the third preset dose is greater than the first preset dose and the second preset dose, and the third rotation speed is greater than the first rotation speed and the second rotation speed.

[0042] As described in the background technology, the existing spin coating process is to spray photoresist to the center of the wafer, and realize the formation of photoresist on the surface of the wafer through high-speed rotation of the wafer. However, for wafer substrates with high and low surface morphology, the existing spin coating process easily causes the photoresist to form diagonal lines along the edges of high steps, and easily causes uneven coating of the photoresist. The photoresist coating method of this embodiment selects a target position between the center of the wafer and the edge of the wafer before spraying the photoresist to the center of the wafer, first sprays the photoresist between the center of the wafer and the target position of the wafer, and continues to spray the photoresist separately at the target position of the wafer, and controls the rotation speed of the wafer to prevent the photoresist from agglomerating, and at the same time prevents the photoresist from being thrown out of the wafer surface and causing waste, so that a uniform photoresist film thickness is formed on the wafer surface with high and low differences, reducing or even avoiding the formation of diagonal lines along the edges of high steps of the photoresist, improving the preparation efficiency of the device, and at the same time can reduce or even avoid the uneven exposure pattern line width caused by uneven photoresist thickness, thereby reducing or even avoiding the impact on the performance and yield of the device caused by this.

[0043] The photoresist coating method of this embodiment is described in detail below with reference to the specific drawings.

[0044] like Figure 2 and Figure 3 As shown, firstly, step S1 is performed, as Figure 2 As shown, the wafer 1 is controlled to rotate at a first speed, and the nozzle 3 is placed at a first preset height at the center of the surface of the wafer 1 to start spraying the photoresist 4, as shown in FIG. Figure 3 As shown, during the spraying process, the nozzle 3 is kept at the first preset height and moves at a uniform speed along the radial direction of the wafer 1 to stop above the target position 11 on the surface of the wafer 1. During this process, the nozzle 3 sprays the photoresist 4 with a first preset dose. Figure 4 As shown, the target position 11 is located between the center position of the wafer 1 and the edge position of the wafer 1 .

[0045] As an example, before spraying the first preset dose of the photoresist 4 on the surface of the wafer 1, the following steps are also included:

[0046] S11: Determine the total amount of the photoresist 4 sprayed; a person skilled in the art can calculate the total amount of the photoresist 4 sprayed and the third rotational speed based on the desired spraying thickness and the surface area of ​​the wafer 1. The thinner the desired sprayed photoresist 4 thickness is, the faster the third rotational speed is set; the thicker the desired sprayed photoresist 4 thickness is, the slower the third rotational speed is set.

[0047] S12: Determine the first preset amount, the second preset amount, and the third preset amount according to the total spraying amount and the spraying ratio of the first preset amount, the second preset amount, and the third preset amount.

[0048] The wafer 1 described in the present embodiment is a wafer with a high and low surface morphology due to the superposition of multiple layers of substrates and the uneven distribution of pattern density. In order to form the photoresist 4 with uniform film thickness on the surface of the wafer 1 with a high and low surface morphology, in step S1, the position of the nozzle 3 is moved from the center position to the target position 11 and the photoresist 4 is continuously sprayed. The technicians in this field can set the appropriate first rotation speed according to the actual situation to prevent the photoresist 4 from gathering on the surface of the wafer 1, thereby forming a relatively uniform photoresist film thickness on the surface of the wafer 1 with high and low differences. As an example, the first rotation speed is 1000rpm / s~1300rpm / s.

[0049] The target position 11 is located between the center position of the wafer 1 and the edge position of the wafer 1. The target position 11 can be selected according to the actual distribution of the surface height difference of the wafer 1, and the target position 11 is as close to the surface where the height difference of the pattern is dense as possible. Preferably, the target position 11 should not be too close to the center position and edge position of the wafer 1. As an example, Figure 4 As shown, the target position 11 may be located within a circular ring region on the wafer surface where a radius of one third to two thirds of the wafer radial direction is located, and may be located at any position within the circular ring region.

[0050] In this embodiment, the photoresist 4 is formed to be thicker in the center and thinner at the edge due to the height difference of the surface of the wafer 1. Figure 3 As shown, step S2 is then performed to control the wafer 1 to rotate at a second rotation speed, while keeping the spray head 3 stationary at the target position 11 and continuing to spray the photoresist 4 at a second preset dose.

[0051] A person skilled in the art may set a lower second rotation speed according to actual conditions to prevent the photoresist 4 from gathering on the surface of the wafer 1, and to form a thicker film thickness of the photoresist 4 in the area between the target position 11 and the edge position of the wafer 1, so that the photoresist 4 is not thrown out of the surface of the wafer 1 and caused waste. As an example, the second rotation speed may be set lower than the first rotation speed. In the present embodiment, the second rotation speed is preferably set to 600rpm / s to 800rpm / s.

[0052] like Figure 5 and Figure 6 As shown, then proceed to step S3, as shown in Figure 5 As shown, the nozzle 3 is closed to stop the spraying of the photoresist 4, while the wafer 1 is kept rotating at the second speed, as shown in FIG. Figure 6 As shown, during this process, the nozzle 3 is moved from the target position 11 to the first preset height at the center position of the surface of the wafer 1 .

[0053] A preset time can be set for the time that the wafer 1 rotates at the second speed in step S3. As an example, the preset time is set to 2s to 3s, so that a thicker photoresist 4 film is formed in the area between the target position 11 and the edge position of the wafer 1, and the second preset dose of the photoresist 4 is evenly coated to fill the height difference of the surface of the wafer 1, thereby forming the photoresist 4 with uniform center and edge thickness on the surface of the wafer 1 after step S4.

[0054] Those skilled in the art may also set the second rotation speed to be lower according to actual conditions so that the photoresist 4 is not thrown out of the surface of the wafer 1 to cause waste, and further the second preset dose of the photoresist 4 is evenly coated.

[0055] As an example, the second preset dose is set to be greater than the first preset dose, so that a thicker photoresist 4 film thickness is further formed in the area between the target position 11 and the edge position of the wafer 1 to further fill the height difference of the surface of the wafer 1, and then after step S4, the photoresist 4 with uniform thickness in the center and edge is formed on the surface of the wafer 1.

[0056] As an example, Figure 5 and Figure 6As shown, the nozzle 3 is arranged on the glue spraying arm 2, and the movement of the nozzle head 3 is controlled by the glue spraying arm 2. The movement process of moving the nozzle head 3 from the target position 11 to the center position of the surface of the wafer 1 in step S3 is: lifting the glue spraying arm 2 to place the nozzle head 3 at a second preset height above the wafer 1, and then controlling the glue spraying arm 2 to drive the nozzle head 3 to move from the second preset height above the target position 11 to above the center position of the wafer 1, and then controlling the glue spraying arm 2 to place the nozzle head 3 at the first preset height, wherein the second preset height is greater than the first preset height.

[0057] like Figure 7 As shown, step S4 is then performed to control the wafer 1 to rotate at a third speed, open the nozzle 3 and start spraying the photoresist 4 with a third preset dose; wherein the third preset dose is greater than the first preset dose and the second preset dose, and the third speed is greater than the first speed and the second speed.

[0058] In this embodiment, the first preset dose of the photoresist 4 is first sprayed between the center position of the wafer 1 and the target position 11 of the wafer 1, and the wafer 1 is controlled to rotate at the first speed to prevent the photoresist 4 from agglomerating; then the second preset dose of the photoresist 4 is sprayed separately on the target position 11 of the wafer 1, and the wafer 1 is controlled to rotate at the second speed to prevent the photoresist 4 from being thrown out of the surface of the wafer 1 and causing waste, so that a thicker film thickness of the photoresist 4 is formed in the area between the target position 11 and the edge position of the wafer 1, and the second preset dose of the photoresist 4 is evenly coated to fill the height difference on the surface of the wafer 1; finally, the third preset dose of the photoresist 4 is sprayed to the center position of the wafer 1, and the wafer 1 is controlled to rotate at the third speed to realize the photoresist film formation on the wafer surface to form the desired sprayed photoresist 4 thickness.

[0059] It can be seen that the third rotation speed and the third preset dose are the core parameters for forming the target photoresist film thickness, that is, the main spraying, which directly affects the thickness of the formed photoresist 4. The appropriate third rotation speed and the third preset dose can be selected according to the actual target film thickness. Therefore, in this embodiment, it is necessary to set the third preset dose greater than the first preset dose and the second preset dose, that is, the third preset dose is greater than the first preset dose, and the third preset dose is greater than the second preset dose; at the same time, it is necessary to set the third rotation speed greater than the first rotation speed and the second rotation speed, that is, the third rotation speed is greater than the first rotation speed, and the third rotation speed is greater than the second rotation speed. In this embodiment, the third rotation speed is preferably set to 3500rpm / s~4500rpm / s.

[0060] As an example, the spraying ratio of the first preset dose, the second preset dose and the third preset dose is (0.8-1.2):(2.5-3.5):(5.5-6.5). Preferably, in this embodiment, the spraying ratio of the first preset dose, the second preset dose and the third preset dose is 1:3:6. Then, when the total spraying amount is 6ml, the first preset dose is 0.6ml, the second preset dose is 1.8ml, and the third preset dose is 3.6ml. When spraying the first preset dose, the second preset dose and the third preset dose of photoresist, the spraying speed of the nozzle is kept unchanged to make the photoresist coating more uniform.

[0061] As an example, Figure 8 As shown, after performing step S4, it usually also includes closing the nozzle 3 to stop spraying the photoresist 4, controlling the wafer 1 to rotate at a third speed so that the third preset dose of the photoresist 4 is evenly coated, and at the same time lifting the spray arm 2 to place the nozzle 3 at the second preset height.

[0062] In summary, the present invention provides a method for coating photoresist, which selects a target position between the center of the wafer and the edge of the wafer before spraying the photoresist to the center of the wafer, sprays the photoresist between the center of the wafer and the target position of the wafer, and continues to spray the photoresist separately to the target position of the wafer, and controls the rotation speed of the wafer to prevent the photoresist from agglomerating, and prevents the photoresist from being thrown out of the wafer surface to cause waste, so that a uniform photoresist film thickness is formed on the wafer surface with high and low differences, reduces or even avoids the formation of diagonal lines along the edge of the high step of the photoresist, improves the preparation efficiency of the device, and can reduce or even avoid the uneven exposure pattern line width caused by the uneven thickness of the photoresist, thereby reducing or even avoiding the impact on the performance and yield of the device caused by the uneven thickness of the photoresist. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A photoresist coating method, characterized in that: The coating method comprises: S1, controlling the wafer to rotate at a first speed, and placing the nozzle at a first preset height at the center of the wafer surface to start spraying photoresist, and during the spraying process, the nozzle is kept at the first preset height and moves at a uniform speed along the radial direction of the wafer to stop above a target position on the wafer surface; wherein, during this process, the nozzle sprays the photoresist at a first preset dose, and the target position is located between the center of the wafer and the edge of the wafer; S2, controlling the wafer to rotate at a second rotation speed, while keeping the spray head stationary at the target position and continuing to spray the photoresist at a second preset dose; S3, closing the nozzle to stop spraying the photoresist, while keeping the wafer rotating at the second speed, during which the nozzle is moved from the target position to the first preset height at the center of the wafer surface; S4, controlling the wafer to rotate at a third rotation speed, opening the nozzle and starting to spray the photoresist at a third preset dose; wherein the third preset dose is greater than the first preset dose and the second preset dose, and the third rotation speed is greater than the first rotation speed and the second rotation speed.

2. The photoresist coating method according to claim 1, characterized in that: The nozzle is arranged on a glue spraying arm, and the movement of the nozzle is controlled by the glue spraying arm. The movement process of moving the nozzle from the target position to the center position of the wafer surface in step S3 is: lifting the glue spraying arm to place the nozzle at a second preset height above the wafer, and then controlling the glue spraying arm to drive the nozzle to move from the second preset height above the target position to above the center position of the wafer, and then controlling the glue spraying arm to place the nozzle at the first preset height, wherein the second preset height is greater than the first preset height.

3. The photoresist coating method according to claim 1, characterized in that: The second preset dose is greater than the first preset dose.

4. The photoresist coating method according to claim 1, characterized in that: Before spraying the first preset dose of photoresist on the wafer surface, the method further includes the following steps: Determining the total amount of the photoresist sprayed; The first preset amount, the second preset amount and the third preset amount are determined according to the total spraying amount and the spraying ratio of the first preset amount, the second preset amount and the third preset amount.

5. The photoresist coating method according to claim 1, characterized in that: The spraying ratio of the first preset dose, the second preset dose and the third preset dose is (0.8-1.2):(2.5-3.5):(5.5-6.5).

6. The photoresist coating method according to claim 1, characterized in that: The first rotation speed is greater than the second rotation speed.

7. The photoresist coating method according to any one of claims 1 to 6, characterized in that: The first rotation speed is 1000 rpm / s to 1300 rpm / s, the second rotation speed is 600 rpm / s to 800 rpm / s, and the third rotation speed is 3500 rpm / s to 4500 rpm / s.

8. The photoresist coating method according to claim 1, characterized in that: The target position is located in a circular ring area on the wafer surface where the radius is one-third to two-thirds of the radial direction of the wafer.

9. The photoresist coating method according to claim 1, characterized in that: When spraying the first preset dose, the second preset dose and the third preset dose of photoresist, the spraying speed of the nozzle is kept unchanged.

10. The photoresist coating method according to claim 1, characterized in that: In step S3, the wafer rotates at the second speed for 2s to 3s.

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