A method for avoiding leakage of electroless plating on one side and a method for manufacturing a semiconductor device

Abstract

The present invention is designed for the single-sided electroless plating of wafers thinned by the Taiko process. The main purpose is to avoid the problem of liquid leakage during the single-sided electroless plating process. It relates to a method for avoiding liquid leakage in single-sided electroless plating and a semiconductor device manufacturing method. The wafer with a Taiko ring formed is loaded on a fixing rack, and the surface where the Taiko ring is located adheres to the loading film in the middle of the fixing rack. The outer circle of the loading film is fixed with a rigid support ring. The fixed wafer is cut, and the Taiko ring on the wafer is removed. Then, the wafer still loaded on the fixing rack after cutting and the fixing rack are put into the plating solution together for single-sided electroless plating. Compared with the existing single-sided electroless plating process method, the present invention omits the processes of film pasting before electroless plating and film peeling after electroless plating, advances the cutting after electroless plating in the original process to before electroless plating, eliminates the influence of liquid leakage caused by the Taiko ring, simplifies the process, and improves the product appearance and application reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and particularly relates to a method for avoiding liquid leakage in single-sided electroless plating and a method for manufacturing semiconductor devices. Background Art

[0002] Clip packaging is a common packaging form for power device IGBTs, which has the advantages of good contact, heat sink, and good temperature rise. Electroless plating is a necessary process in the Clip packaging process, and electroless plating is divided into single-sided plating and double-sided plating. Taking IGBT production as an example, after forming the unit structure of the IGBT device on the substrate, a front metal layer is formed on the front of the substrate, the substrate is thinned, a collector region is formed on the back of the substrate, and before forming the target metal layer on the front by using single-sided electroless plating, it is necessary to coat the back of the wafer with a film, usually a UV film, and use the protective film to prevent the back metal layer from contacting the chemical agent. After the electroless plating is completed, the coated film is removed.

[0003] When manufacturing IGBTs, Taiko thinning process is often used to thin the substrate. This process was publicly developed by DISCO of Japan. The Taiko thinning process does not thin the entire surface of a certain side of the wafer, but only thins the middle part of the wafer, so that a relatively thick support ring is formed at the edge of the wafer. This support ring is usually called Taiko ring. Especially for larger-sized wafers (such as 8 inches), warping problems will occur after thinning, which will affect subsequent processes. Therefore, the remaining Taiko ring is beneficial to reduce the warping of the wafer, greatly reducing the transfer requirements for the subsequent process processing machine and the risk of wafer fragmentation.

[0004] In the existing IGBT manufacturing process, the back thinning process is usually carried out after the front process of the wafer is completed, and then the collector is formed through ion implantation, activation, and back PVD process. Then, the back of the wafer is coated with a film for protection, the protective film is removed after the electroless plating process, and then the wafer is fixed on the frame for the scribing process (i.e., cutting the Taiko ring), and finally the wafer is diced and packaged for shipment. As Figure 1 shown, after the wafer undergoes the Taiko thinning process, it forms Figure 1 the structure in, that is, the middle thinning part 1 and the Taiko ring 2 at the edge. A step is formed at the connection between the Taiko ring 2 and the middle thinning part 1. In the existing single-sided electroless plating process, the Taiko ring 2 has been formed when the protective film is coated on the back of the wafer. Due to the existence of the step difference of the Taiko ring 2, the protective film 3 attached to the back of the wafer cannot fit well with the wafer, and liquid leakage is likely to occur at the step of the Taiko ring 2 in the electroless plating solution ( Figure 1As shown by the circle in the figure, it causes the metal layer on the back of the wafer to come into contact with the chemical agent, which will have a certain impact on the appearance of the product and the reliability of its application. In view of this, the inventor has improved the existing IGBT manufacturing process, especially in improving the prevention of liquid leakage in the single-sided electroless plating process, and this case is thus born. Summary of the Invention

[0005] The present invention first discloses a method for avoiding liquid leakage in single-sided electroless plating, which omits the film pasting step before electroless plating and the film peeling step after electroless plating. It not only simplifies the production process and saves manufacturing costs, but also can effectively avoid the problem of liquid leakage in the single-sided electroless plating process.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for avoiding liquid leakage in single-sided electroless plating, comprising: loading the wafer with a Taiko ring formed thereon onto a fixing rack, making the surface where the Taiko ring is located adhere to the loading film in the middle of the fixing rack, and fixing the outer circle of the loading film with a rigid support ring; performing a circumcision on the fixed wafer to remove the Taiko ring on the wafer, and then putting the wafer still loaded on the fixing rack together with the fixing rack into a plating solution for single-sided electroless plating.

[0008] Further, the rigid support ring is made of a metal ring, and the outside of the metal ring is coated with a corrosion-resistant non-metallic material.

[0009] Further, the outside of the metal ring is coated with polyethylene.

[0010] Further, the rigid support ring is made of a corrosion-resistant non-metallic ring.

[0011] Further, the loading film has adhesiveness and is corrosion-resistant.

[0012] Further, the loading film is a UV film.

[0013] The present invention also discloses a method for manufacturing a semiconductor device, including the above method for avoiding liquid leakage in single-sided electroless plating.

[0014] Further, after completing the single-sided electroless plating, it further includes dicing the wafer.

[0015] Further, when dicing the wafer, directly use the fixing rack for loading the wafer as a fixing carrier to dice the surface of the wafer that is not adhered by the loading film.

[0016] Further, the semiconductor device is an IGBT.

[0017] The present invention is designed for wafers thinned by the Taiko thinning process that need to undergo single-sided electroless plating. The main purpose is to avoid liquid leakage problems during the single-sided electroless plating process. Compared with the existing single-sided electroless plating process methods, the present invention eliminates the film pasting process for the protective surface of the wafer before electroless plating and also eliminates the film peeling process after electroless plating. It advances the circumferential cutting process after electroless plating in the original process to before electroless plating. Since the liquid leakage influence caused by the Taiko ring has been eliminated before electroless plating, the method of the present invention not only simplifies the production process, saves manufacturing costs, but also effectively avoids the occurrence of liquid leakage during electroless plating, improving both the appearance of the product and the reliability of its application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is a schematic diagram of the state of the Taiko ring and the protective film attached to the wafer surface in the prior art;

[0019] Figure 2 FIG. is a schematic diagram of the structure of the thinned wafer loaded on the fixture before circumferential cutting using the method of the present invention;

[0020] Figure 3 For Figure 2 top view;

[0021] Figure 4 FIG. is a schematic diagram of the structure of the wafer carried on the fixture after circumferential cutting using the method of the present invention;

[0022] Figure 5 For Figure 4 top view;

[0023] Figure 6 FIG. is a flowchart of manufacturing an IGBT using the manufacturing method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention.

[0025] This embodiment discloses a method for avoiding liquid leakage during single-sided electroless plating and a semiconductor device manufacturing method. Here, the semiconductor device mentioned is taken as an IGBT as an example, mainly for optimizing the IGBT manufacturing process design, aiming to improve the problem of liquid leakage on the back surface caused by the protective film not fully contacting the back surface of the wafer during the single-sided electroless plating process. The method for avoiding liquid leakage during single-sided electroless plating involved in this embodiment is not only applicable to the IGBT manufacturing process, but also applicable to any wafer thinned by the Taiko thinning process that needs to undergo single-sided electroless plating operations. The following description will be given taking the IGBT manufacturing process as an example.

[0026] Such as Figure 6As shown, in the conventional process of IGBTs, a device structure layer is first formed on the front side of the substrate wafer, and then the back side of the wafer is thinned. In the prior art, the Taiko thinning process is mainly used to achieve this. After thinning, a collector is formed on the back side of the wafer through processes such as ion implantation, activation, and backside PVD. The above processes are all the basic process flows of existing IGBTs and are well-known technologies to those skilled in the art. Therefore, the present invention will not elaborate on this too much. After the collector is formed on the back side of the wafer, a single-sided electroless plating treatment needs to be performed on the front side of the wafer. At this time, since a metal layer has been formed on the back side of the wafer, in order to avoid the plating solution affecting the back side of the wafer during single-sided electroless plating, the back side is usually protected by means of backside film pasting. However, due to the existence of the Taiko ring formed by the Taiko thinning process, the steps of the Taiko ring cannot form good adhesion with the pasted protective film. Once a gap appears here, the plating solution will penetrate from here to the back side of the wafer, thereby affecting the product quality. Therefore, before performing single-sided electroless plating in this embodiment, the Taiko ring needs to be removed first (corresponding to the ring cutting process), and then the single-sided electroless plating operation is carried out.

[0027] When performing the ring cutting process, the wafer needs to be fixed. In this embodiment, a fixture is used to load and fix the wafer. The fixture is as Figure 2 shown, and includes a loading film in the middle and a rigid support ring 7 for fixing the outer circle of the loading film. The loading film needs to have acid and alkali corrosion resistance and also single-sided adhesiveness, and is mainly used to fix the wafer. The loading film can be selected as a UV film. The rigid support ring 7 tightens and fixes the outer edge of the loading film to form a film stretching frame structure. When loading the wafer, the surface where the Taiko ring on the back side of the wafer is located is adhered to the loading film. As Figure 2 and Figure 3 shown, after the wafer is fixed, the loading film can be regarded as three parts. Among them, the part closely attached to the wafer thinning part 1 is the attachment part 4, the part in contact with the Taiko ring is the Taiko ring embedding part 5, and the part connected to the rigid support ring 7 is the edge connection part 6. Since the fixture after loading the wafer needs to be put into the plating solution together with the wafer after the ring cutting process, usually the rigid support ring 7 is made of a metal ring, such as a stainless steel ring. In order to avoid the metal ring reacting with the plating solution and contaminating the plating solution, if a metal ring is used, the outer surface of the metal ring needs to be treated, that is, coated with a corrosion-resistant non-metallic material, such as polyethylene. Of course, the rigid support ring 7 can also be directly made of a corrosion-resistant non-metallic ring.

[0028] After loading the wafer on the fixture according to the above method, the ring cutting process is performed to remove the Taiko ring 2, that is, to separate the Taiko ring 2 from the thinning part 1, and then the cut Taiko ring 2 is removed from the loading film. The structure after ring cutting is as Figure 4 and Figure 5As shown, at this time, without the existence of the Taiko ring 2, the thinning portion 1 and the bonding portion 4 of the loading film are closely adhered together. The wafer still loaded on the fixture after circumcision and the fixture are put into the plating solution together for single-sided electroless plating. In the original process, a back film is applied before electroless plating, and the film needs to be removed after electroless plating. After the film is removed, the circumcision process is carried out, and the wafer also needs to be fixed first during circumcision. In this embodiment, however, the wafer has been fixed by the fixture with the loading film before electroless plating. Therefore, after the electroless plating is completed, the fixture and the wafer are taken out of the plating solution, and then the wafer dicing process is carried out on the front side of the wafer (i.e., the side not adhered by the loading film). When dicing the wafer, usually one side of the wafer is adhered to the film for fixation first, and then the other side of the wafer (i.e., the non-film-coated side) is cut. In this embodiment, since the wafer after electroless plating is still loaded on the fixture, and the loading film on the fixture has played a role in fixing the wafer, there is no need to re-apply the film for fixation for wafer cutting. Many processes can be saved in the process steps, which improves the production efficiency and also saves the consumption of the film.

[0029] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for avoiding leakage of single-sided electroless plating, characterized in that Comprising: Loading the wafer forming the Taiko ring onto a fixture, making the surface where the Taiko ring is located adhere to the loading film in the middle of the fixture, and fixing the outer ring of the loading film with a rigid support ring; performing a scribing on the fixed wafer to remove the Taiko ring on the wafer, and then putting the wafer still loaded on the fixture together with the fixture into a plating solution for single-sided electroless plating.

2. A method for avoiding liquid leakage in single-sided electroless plating according to claim 1, characterized in that: The rigid support ring is made of a metal ring, and the outside of the metal ring is coated with a corrosion-resistant non-metallic material.

3. A method for avoiding leakage of single-sided electroless plating according to claim 2, characterized in that: The outside of the metal ring is coated with polyethylene.

4. A method for avoiding liquid leakage in single-sided electroless plating according to claim 1, characterized in that: The rigid support ring is made of a corrosion-resistant non-metallic ring.

5. A method for avoiding leakage of single-sided electroless plating according to claim 1, characterized in that: The loading film has adhesiveness and is corrosion-resistant.

6. A method for avoiding liquid leakage in single-sided electroless plating according to claim 5, characterized in that: The loading film is a UV film.

7. A method for manufacturing a semiconductor device, characterized in that: Including the method for avoiding liquid leakage in single-sided electroless plating according to any one of claims 1 to 6.

8. A method for manufacturing a semiconductor device according to claim 7, wherein: After completing the single-sided electroless plating, it further includes dicing the wafer.

9. A method for manufacturing a semiconductor device according to claim 8, characterized in that: When dicing the wafer, directly using the fixture loading the wafer as a fixed carrier to dice the surface of the wafer not adhered by the loading film.

10. A method for manufacturing a semiconductor device according to claim 7, wherein: The semiconductor device is an IGBT.

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