Photoetching process gluing method

Abstract

The invention discloses a photoresist coating method for a photolithographic process, which comprises the following steps of: 1, performing spin-coating to coat a layer of photoresist on the surface of a wafer, uniformly distributing the photoresist on the surface of the wafer under the action of centrifugal force generated by rotation, and forming a convex structure on the edge of the wafer; and 2, blowing gas is sprayed from the first nozzle to blow the wafer edge in an inclined and outward manner, so that the thickness of the convex structure is reduced, and the solvent in the photoresist of the convex structure is accelerated to volatilize. And step 3, carrying out edge washing to remove the photoresist on the wafer edge. According to the invention, the uniformity of the photoresist film thickness of the wafer edge can be improved, and the edge washing effect can be improved.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and particularly to a method for coating photoresist in a lithography process. Background Art

[0002] During the process of coating photoresist on a wafer, due to the centrifugal force generated by rotation, the photoresist on the wafer gradually spreads towards the edge of the wafer. Photoresist residues will form protrusions at the wafer edge, resulting in uneven photoresist coating and process contamination.

[0003] In order to remove the photoresist residues accumulated at the wafer edge, an Edge Bean Removal (EBR) process is usually added after the photoresist coating process to remove the photoresist residues at the wafer edge. As the lithography technology node continues to advance, the required thickness of the photoresist is getting thinner and the requirement for the uniformity of the photoresist film thickness is also getting higher. The current EBR process can only remove the relatively thick photoresist at the outermost edge of the wafer. In addition, for some photoresists with a relatively thick spin-coated film thickness, after the EBR process, due to incomplete volatilization of the solvent, the photoresist will still spread towards the wafer edge under the action of centrifugal force, resulting in incomplete EBR, thus affecting the yield and stability of the devices in the wafer edge area.

[0004] As Figures 1A to 1B shown, it is a process schematic diagram of each step of the existing method for coating photoresist in a lithography process; the existing method for coating photoresist in a lithography process includes the following steps:

[0005] Step 1: As Figure 1A shown, perform spin coating to coat a layer of photoresist 104 on the surface of the wafer 102. Under the action of the centrifugal force generated by rotation, the photoresist 104 is evenly distributed on the surface of the wafer 102 and forms a raised structure 104a at the wafer edge. The wafer edge is the edge area of the wafer 102.

[0006] The wafer 102 is placed on a rotatable wafer carrier 101, and the photoresist 104 is ejected from the nozzle 103. Figure 1A In

[0007] Step 2: As Figure 1B shown, perform edge cleaning to remove the photoresist 104 at the wafer edge, aiming to remove the raised structure 104a, that is, the photoresist protrusion residue.

[0008] The edge cleaning is achieved by keeping the wafer 102 rotating and spraying an edge cleaning liquid 106 onto the wafer edge through the nozzle 105.

[0009] In the existing edge cleaning process, the cleaning effect is often poor. This is mainly because the thickness of the convex structure 104a is relatively thick. After the photoresist 104 in the edge cleaning area is removed, the relatively thick photoresist in the edge cleaning area will diffuse into the edge cleaning area under the action of centrifugal force due to incomplete volatilization of the solvent, resulting in photoresist residue in the edge cleaning area, that is, the edge cleaning is not clean, which will affect the yield and stability of the devices in the crystal edge area.

[0010] As Figure 2 shown, it is a photo of the crystal edge after the existing photolithography process coating method is completed; it can be seen that due to the relatively thick photoresist at the crystal edge, it is not easy to dry thoroughly, and burrs as shown by the mark 107 are likely to appear during edge cleaning. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a photolithography process coating method that can improve the uniformity of the photoresist film thickness at the crystal edge and improve the edge cleaning effect.

[0012] To solve the above technical problems, the photolithography process coating method provided by the present invention includes the following steps:

[0013] Step 1: Perform spin coating to coat a layer of photoresist on the surface of the wafer. Under the action of the centrifugal force generated by rotation, the photoresist is evenly distributed on the surface of the wafer and a convex structure is formed at the crystal edge, where the crystal edge is the edge area of the wafer.

[0014] Step 2: Spray purge gas from the first nozzle to purge the crystal edge obliquely outwards, so as to reduce the thickness of the convex structure and accelerate the volatilization of the solvent in the photoresist of the convex structure.

[0015] Step 3: Perform edge cleaning to remove the photoresist at the crystal edge.

[0016] A further improvement is that in Step 1, the wafer is placed on a rotatable wafer carrier stage, and the photoresist is ejected from the second nozzle.

[0017] A further improvement is that the second nozzle is vertically aligned with the center of the wafer.

[0018] A further improvement is that in Step 2, the wafer keeps rotating.

[0019] A further improvement is that the purge gas includes nitrogen.

[0020] A further improvement is that in Step 3, the edge cleaning is achieved by keeping the wafer rotating and spraying edge cleaning liquid onto the crystal edge through the third nozzle.

[0021] A further improvement is that the rotation speed of the wafer during the edge cleaning process and the rotation speed of the wafer during the purge process are independent of each other.

[0022] A further improvement is that during the edge cleaning process, the spraying direction of the third nozzle is inclined outward with respect to the edge of the wafer.

[0023] The included angle between the spraying direction of the third nozzle and the top surface of the wafer is independently set from the included angle between the spraying direction of the first nozzle and the top surface of the wafer.

[0024] Before edge cleaning and after spin coating, the present invention adds a step of purging the edge of the wafer. Purging can flatten the raised structure formed by the photoresist on the edge of the wafer, thereby improving the uniformity of the photoresist film thickness on the edge of the wafer. After the photoresist film thickness on the edge of the wafer is reduced, it is beneficial to the edge cleaning process and improves the edge cleaning effect.

[0025] Meanwhile, purging can also accelerate the volatilization of the solvent in the photoresist at the edge of the wafer. After the solvent in the photoresist at the edge of the wafer has completely volatilized, after edge cleaning is completed, it can prevent the photoresist in the inner region of the edge cleaning ring from spreading towards the edge region of the wafer under the action of centrifugal force, thereby preventing the defect of incomplete edge cleaning and further improving the edge cleaning effect.

[0026] Therefore, the present invention can improve the uniformity of the photoresist film thickness on the edge of the wafer and the edge cleaning effect, thereby improving the yield and stability of the devices in the edge region of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0028] Figures 1A - 1B is a process schematic diagram of each step of the existing photolithography process spin coating method;

[0029] Figure 2 is a photo of the edge of the wafer after the existing photolithography process spin coating method is completed;

[0030] Figure 3 is a flowchart of the photolithography process spin coating method of the embodiment of the present invention;

[0031] Figures 4A - 4C is a process schematic diagram of each step of the photolithography process spin coating method of the embodiment of the present invention;

[0032] Figure 5 is a photo of the edge of the wafer after the photolithography process spin coating method of the embodiment of the present invention is completed. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] As Figure 3 shown, it is a flowchart of the photolithography process spin coating method of the embodiment of the present invention; as Figures 4A to 4C shown, it is a process schematic diagram of each step of the photolithography process spin coating method of the embodiment of the present invention; the photolithography process spin coating method of the embodiment of the present invention includes the following steps:

[0034] Step 1: As shown in Figure 4A , spin coating is performed to coat a layer of photoresist 204 on the surface of the wafer 202. Under the action of the centrifugal force generated by rotation, the photoresist 204 is evenly distributed on the surface of the wafer 202 and a raised structure 204a is formed at the wafer edge. The wafer edge is the edge area of the wafer 202.

[0035] In the embodiment of the present invention, the wafer 202 is placed on a rotatable wafer carrier 201, and the photoresist 204 is ejected from the second nozzle 203. In some preferred embodiments, the second nozzle 203 is vertically aligned with the center of the wafer 202. Figure 4A In , the rotation arrow line indicates that the wafer carrier 201 rotates, and the wafer 202 fixed on the wafer carrier 201 will rotate together.

[0036] Step 2: As shown in Figure 4B , purge gas 206 is ejected from the first nozzle 205 to purge the wafer edge obliquely outward, so as to reduce the thickness of the raised structure 204a and accelerate the volatilization of the solvent in the photoresist 204 of the raised structure 204a.

[0037] In the embodiment of the present invention, the wafer 202 remains rotating.

[0038] The purge gas 206 includes nitrogen. In other embodiments, the purge gas 206 can use other suitable gases, such as inert gases, as long as it can provide a purge force and will not chemically react with the photoresist 204.

[0039] In some specific embodiments, the flow rate and purge time of the purge gas 206 can be set according to actual needs, and it is required to reduce the thickness of the raised structure 204a below the process requirement value to ensure good edge cleaning can be achieved subsequently. Comparing Figure 4B and Figure 4A as shown, it can be seen that Figure 4B the thickness of the raised structure 204a in is reduced; at the same time, Figure 4B in , the solvent content of the raised structure 204a will also be reduced.

[0040] Step 3: As shown in Figure 4C , edge cleaning is performed to remove the photoresist 204 at the wafer edge.

[0041] In the embodiment of the present invention, the edge cleaning is achieved by keeping the wafer 202 rotating and ejecting an edge cleaning liquid 208 from a third nozzle 207 to the wafer edge.

[0042] The rotation speed of the wafer 202 during the edge cleaning process and the rotation speed of the wafer 202 during the purging process are independent of each other. That is, the two can be equal or unequal, and can be set according to specific needs.

[0043] During the edge cleaning process, the spraying direction of the third nozzle 207 is inclined outward from the edge of the wafer. The angle between the spraying direction of the third nozzle 207 and the top surface of the wafer 202 and the angle between the spraying direction of the first nozzle 205 and the top surface of the wafer 202 are independently set. That is, the two can be equal or unequal, and can be set according to specific needs.

[0044] In some specific embodiments, the flow rate and the cleaning time of the edge cleaning liquid 208 can be set according to actual needs to ensure that the photoresist 204 on the edge of the wafer is completely removed.

[0045] In the embodiment of the present invention, before edge cleaning and after coating, a purging step for the edge of the wafer is added. Purging can flatten the convex structure 204a formed by the photoresist 204 on the edge of the wafer, thereby improving the uniformity of the film thickness of the photoresist 204 on the edge of the wafer. After the film thickness of the photoresist 204 on the edge of the wafer is reduced, it is beneficial to the edge cleaning process and improves the edge cleaning effect.

[0046] At the same time, purging can also accelerate the volatilization of the solvent in the photoresist 204 at the edge of the wafer. After the solvent in the photoresist 204 at the edge of the wafer is completely volatilized, after edge cleaning is completed, it can prevent the photoresist 204 in the inner region of the edge cleaning ring from spreading to the edge region of the wafer under the action of centrifugal force, thereby preventing the defect of incomplete edge cleaning and further improving the edge cleaning effect.

[0047] Therefore, the embodiment of the present invention can improve the uniformity of the film thickness of the photoresist 204 on the edge of the wafer and the edge cleaning effect, thereby improving the yield and stability of the devices in the edge region of the wafer.

[0048] As Figure 5 shown, it is a photo of the edge of the wafer after the coating method of the photolithography process in the embodiment of the present invention is completed. It can be seen that there are no burrs formed by the unremoved photoresist in the edge region of the wafer 202.

[0049] The embodiment of the present invention can improve the uniformity of the film thickness at the edge of the coating in the photolithography process and the edge cleaning effect by adding N2 purging.

[0050] In the embodiments of the present invention, the N2 purging force causes the photoresist piled up at the edge to be coated towards the edge, reducing the film thickness of the photoresist at the crystal edge, thereby improving the film thickness uniformity at the edge of the photoresist. At the same time, blowing N2 during the photoresist edge cleaning helps the rapid volatilization of the photoresist solvent, enabling the rapid film formation of the photoresist at the wafer edge, enhancing the edge cleaning effect, saving the edge cleaning time, thereby improving the edge cleaning roughness and film thickness uniformity of the photoresist at the wafer edge, and contributing to more uniform and sufficient exposure in the crystal edge region.

[0051] The present invention has been described in detail through specific embodiments above, but these do not constitute limitations to the present invention. Without departing from the principle of the present invention, those skilled in the art can also make many deformations and improvements, which should also be regarded as the protection scope of the present invention.

Claims

1. A photolithography process glue coating method, characterized in that: The steps include: Step 1: Spin coating to coat a layer of photoresist on the surface of the wafer. Under the action of the centrifugal force generated by the rotation, the photoresist is evenly distributed on the surface of the wafer and forms a convex structure at the edge of the wafer. The edge of the wafer is the edge area of ​​the wafer. Step 2, spraying a purge gas from a first nozzle to purge the crystal edge obliquely outward, so as to reduce the thickness of the protruding structure and accelerate the volatilization of the solvent in the photoresist of the protruding structure; Step three: performing edge washing to remove the photoresist on the crystal edge.

2. The photolithography process glue coating method according to claim 1, characterized in that: In step one, the wafer is placed on a rotatable wafer carrier, and photoresist is sprayed from a second nozzle.

3. The photolithography process glue coating method according to claim 2, characterized in that: The second nozzle is vertically aligned with the center of the wafer.

4. The photolithography process glue coating method according to claim 2, characterized in that: In step 2, the wafer keeps rotating.

5. The photolithography process glue coating method according to claim 4, characterized in that: The purge gas includes nitrogen.

6. The photolithography process glue coating method according to claim 4, characterized in that: In step three, the edge cleaning is achieved by keeping the wafer rotating and spraying edge cleaning liquid toward the wafer edge through a third nozzle.

7. The photolithography process glue coating method according to claim 6, characterized in that: The rotation speed of the wafer during the edge cleaning process and the rotation speed of the wafer during the purge process are independent of each other.

8. The photolithography process glue coating method according to claim 6, characterized in that: During the edge washing process, the spray direction of the third nozzle is such that the crystal edge is inclined outward; The angle between the spraying direction of the third nozzle and the top surface of the wafer and the angle between the spraying direction of the first nozzle and the top surface of the wafer are set independently of each other.

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