JPH0789546B2 - Wafer processing film - Google Patents

Description

The present invention relates to a film for preventing damage to a wafer used when polishing the back surface of a wafer (hereinafter referred to as a wafer) such as a silicon wafer having an integrated circuit formed thereon (hereinafter referred to as a wafer). .

[Conventional technology]

Wafers used for manufacturing semiconductor chips include those such as silicon and gallium arsenide, and among them, silicon is often used. For example, a silicon wafer is manufactured by thinly slicing high-purity single crystal silicon to a thickness of about 500 to 1000 μm, but in recent years, with the downsizing and mass production of chips, the thickness tends to be further reduced. In addition, the size is shifting from the conventional 3 to 4 inches to 5 to 8 inches.

The silicon wafer itself is fragile by nature, and further, the one having an integrated circuit incorporated on its surface has a drawback that it is easily damaged by a slight external force due to the unevenness of the surface. It is a major obstacle.

Conventionally, as a method of preventing damage when processing a back surface of a silicon wafer, a method of using post-processing while filling unevenness on the surface by using paraffin, resist ink, or the like so as to disperse an applied external force has been adopted. However, this method requires a step of drying and solidifying after applying paraffin or the like, and further washing and removing the paraffin or the like under heating with a solvent after polishing, which makes the operation complicated. In addition to this, the conventional method cannot still prevent the damage of the wafer in polishing a large-diameter wafer of 5 inches or more,
It was a big obstacle to productivity improvement. Further, there is a problem of contamination of the wafer surface due to the use of paraffin and the like, and thus there has been a strong demand for the development of a wafer damage prevention method which replaces the coating method of paraffin and the like.

[Problems to be solved by the invention]

In view of the above problems, it is an object of the present invention to prevent damage to the back surface of a wafer, preferably a silicon wafer, while contributing to improvement in productivity, and to prevent contamination of the wafer surface. It is to provide a film for processing.

[Means for solving problems]

As a method for filling irregularities on the wafer surface and dispersing external force, the present inventors prevent a wafer from being damaged by bonding a substrate film having a specific hardness to the wafer surface via a back surface adhesive layer during polishing. I found what I could do. Furthermore, by laminating an auxiliary film having a specific hardness on the surface of the base film opposite to the surface on which the adhesive layer is provided, the workability of attaching the wafer to the processed film can be reduced without lowering the wafer damage prevention effect. The inventors have found that the workability of peeling a film after polishing a wafer is significantly improved, and have completed the present invention.

That is, the present invention is a wafer processing film used for polishing the back surface of a silicon wafer having an integrated circuit formed on the surface and having unevenness, and having a thickness selected from an ethylene-vinyl acetate copolymer film and a polybutadiene film. The Shore D type hardness is 10 to 2000 μm and the Shore D type hardness is 40 or less on one surface of the base film.
An auxiliary film having a thickness of more than 40 and a thickness of 10 to 1000 μm is laminated, and an adhesive layer selected from the group consisting of acrylic, ester, urethane and synthetic rubber is provided on the other surface of the base film. A film for processing a wafer, which is disposed and is used to polish the back surface of the wafer by adhering the adhesive layer to the front surface of the wafer.

[Preferable Embodiments for Carrying Out the Invention]

Wafers for which the processing film of the present invention is used are
Not only silicon wafers but also gallium-arsenic, gallium-
Wafers of phosphorus, germanium and the like are mentioned, and particularly preferably used for large-diameter silicon wafers.

The substrate film used in the present invention can be appropriately selected from those having a Shore D type hardness of 40 or less, preferably 30 or less, selected from ethylene-vinyl acetate copolymer and polybutadiene. The Shore D type hardness is a value measured by using a D type Shore hardness meter according to ASTM D-2240. If the Shore D hardness exceeds 40, the ability to disperse the external force applied to the wafer is poor, and damage during polishing of the wafer cannot be substantially prevented.

The thickness of the base film is appropriately selected depending on the material, shape, surface state, polishing method, and polishing conditions of the wafer to be protected, but a thickness of 10 to 2000 μm is suitable.

On the other hand, the auxiliary film is made of a thermoplastic resin, a thermosetting resin, or a paper laminated with a synthetic resin, a thin wood plate, or the like, and has a Shore D type hardness of more than 40, for example, in Examples described later. Shore D type hardness as shown
A level of 80 or more is sufficient, and various films can be appropriately selected. When the hardness is 40 or less, the purpose of laminating the auxiliary film cannot be achieved, and the workability at the time of bonding and peeling cannot be improved.

As the material of the auxiliary film, synthetic resin such as polyethylene, polypropylene, polyester, polyamide, hard vinyl chloride resin, polyether sulfone, polyacryl and phenol resin, or paper impregnated with phenol resin, paper coated with polyethylene, etc. It is exemplified as a typical one.

The thickness of the auxiliary film is appropriately selected depending on the specifications of the machine for sticking the processing film on the wafer and the machine for peeling it, and the thickness of the base film, but it is 10 to 1000 μm.
The ones are suitable.

As a method of laminating the auxiliary film on the base film, there is a method of applying an adhesive to one of the base film and the auxiliary film which are manufactured in advance and laminating them together, and simultaneously using a two-layer T die or a two-layer inflation. Various conventionally known laminating methods such as a method of adhering by extrusion, a method of laminating another resin on one film produced in advance by a T-die method or a calender method, and the like can be adopted.

As the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer provided on the surface of the base film, for example, an ordinary commercially available pressure-sensitive adhesive such as an acrylic-based, ester-based, urethane-based pressure-sensitive adhesive or a synthetic rubber-based pressure-sensitive adhesive is used. . The thickness of the adhesive layer is appropriately determined depending on the material, shape, surface condition, polishing method, etc. of the wafer, but normally it is preferably about 2 to 200 μm.

As a method of laminating the pressure-sensitive adhesive on the surface of the base material film, various conventionally known coating methods, for example, a roll coater method, a gravure roll method, a bar coating method, a dipping method, a brush coating method, a spray method, or the like can be adopted. It can be applied to all or part of the film.

The wafer processing film of the present invention is used for polishing the back surface of a wafer by laminating the wafer to the adhesive layer of the processing film when polishing the back surface of the wafer. By using the processing film in this way, it is possible to prevent the wafer from being damaged when the back surface is processed. Further, after the processing is completed, the surface of the wafer can be prevented from being contaminated by peeling the wafer from the processing film by a normal method and performing a simple cleaning operation.

〔The invention's effect〕

Since the film for wafer processing of the present invention has the property that the base film absorbs and disperses the external force applied to the wafer, if it is attached to the wafer and the back surface of the wafer is polished, Can prevent damage. Further, since the auxiliary film is laminated, the shape retention is excellent, the workability at the time of bonding to the wafer and at the time of peeling after polishing is very good, and a great effect can be exerted in improving productivity.

〔Example〕

Example 1 An ethylene-vinyl acetate copolymer resin film (200 having a Shore D type hardness of 30 measured according to ASTM D-2240)
μm thickness) and a Shore D type polypropylene film with a hardness of 80 (100 μm thickness) are adhesively laminated using an acrylic adhesive “Bonron” (manufactured by Mitsui Toatsu Kagaku Co., Ltd.) and ethylene-vinyl acetate copolymer After the corona discharge treatment is applied to the combined resin film surface, an acrylic adhesive "Aromatex" (manufactured by Mitsui Toatsu Chemicals, Inc.) is applied by a roll coater machine, dried, and an acrylic adhesive layer of about 50 μm is applied. A wafer processing film provided with was prepared.

With this film, an integrated circuit is formed and the unevenness of the surface is about
The surface of a 50 μm silicon wafer (6 inches) was bonded by an automatic bonding machine manufactured by Disco Corporation, and the back surface of the wafer was polished by a polishing machine (manufactured by Disco Corporation). After polishing, the processing film was peeled from the wafer, and the wafer was washed with pure water to produce 100 backside processed wafers. At this time, the number of broken wafers was zero, and the working time was about 30 minutes in total.

Example 2 A two-layer film (butadiene rubber layer having a thickness of 200 μm, obtained by simultaneously forming a butadiene rubber having a Shore D type hardness of 20 and a polypropylene having a Shore D type hardness of 80 by a two-layer T-die method. A film for processing a silicon wafer was prepared by coating an acrylic adhesive having a thickness of about 30 μm on a butadiene rubber surface having a polypropylene layer thickness of 100 μm) in the same manner as in Example 1. With this film, the unevenness of the surface is about 30
The silicon wafer having a thickness of μm was bonded to the surface of the silicon wafer, and 100 polished silicon wafers were manufactured in the same manner as in Example 1. As a result, the number of defective products was 0, and the entire processing work was completed in about 30 minutes.

Comparative Example 1 On the surface of the same silicon wafer as used in Example 1,
After pouring the resist ink of about 50 ℃ and cooling for 2 hours,
100 processed silicon wafers were manufactured by the method of polishing the back surface of the wafer, then washing the resist ink with trichloroethylene heated to 50 ° C., and further washing with pure water. At this time, the number of broken wafers was 20. Further, the time required for the processing work was about 5 hours in total. That is, compared with Example 1, the production speed is about 1/10 and the product yield is 80%.
Met. Further, contamination with resist ink was observed on the surface of the wafer after cleaning.

Comparative Example 2 A silicon wafer processing film was prepared by coating an ethylene-vinyl acetate copolymer resin film having a Shore D hardness of 30 (100 μm thick) with an acrylic adhesive in the same manner as in Example 1.

This film was attached to the same silicon wafer surface as that used in Example 1, and the back surfaces of 100 wafers were polished.
As a result, the number of breakages of the wafer was 0, but it took a long time to attach and peel the processing film to the wafer, and the working time took about 1 hour as a whole, and the production rate was about 1 as compared with Example 1. /
Was 2.

Comparative Example 3 A low-density polyethylene film having a Shore D-type hardness of 50 (thickness 200 μm) and a polypropylene film having a Shore D-type hardness of 80 (thickness 100 μm) were laminated in the same manner as in Example 1 and then applied to the surface of the low-density polyethylene film. In the same manner as in Example 1, a silicon wafer processing film coated with an acrylic adhesive having a thickness of about 30 μm was prepared.

Using this film, 100 silicon wafers were back-polished in the same manner as in Example 1. As a result, 76 defective products were generated due to damage.

Comparative Examples 4 and 5 The same raw material as that of the base film of Example 1 was used as the resin for the base film, and the same raw material as that of the auxiliary film of Example 1 was used as the resin for the auxiliary film, and the two-layer coextrusion inflation method was used. A laminated film having the structure shown in Table 1 was obtained.
An acrylic pressure-sensitive adhesive layer was provided on this laminated film in the same manner as in Example 1 to prepare a film for wafer processing. Table 1 shows the number of wafer breakages and workability when the same operation as in Example 1 was performed using this wafer processing film.

The workability of Comparative Example 4 was good because the thickness of the auxiliary film was within the range of the present invention, but the number of breakages of the wafer was large because the base film layer to be the cushion was thin. The workability of Comparative Example 5 was such that the auxiliary film was too thin and wrinkles were likely to occur, but the number of breakages of the wafer was 0 because the base film layer was within the range of the present invention.

Comparative Examples 6 and 7 Wafer processing films were prepared in the same manner as in Example 1 except for the thicknesses of the base film and auxiliary film shown in Table 1. Table 1 shows the number of wafer breakages and workability when the same operation as in Example 1 was performed using this wafer processing film.

As for workability in Comparative Example 6, since the auxiliary film was too thick, the cutability at the time of laminating the films was poor and it took time. On the other hand, the number of broken wafers was the same as in Comparative Example 5.

The cuttability depends on the following general work procedure used when a film is attached to a wafer.

1. Stick tape on the wafer surface.

2. Cut the excess film protruding from the wafer along the wafer. (Shows the ease of cutting at this time) 3. Move to the backside grinding process.

The workability of Comparative Example 7 exceeded 1 hour due to an increase in the total thickness of the base film and the auxiliary film.

Example 3 Tables 2 and 3 show that the same ethylene D-vinyl acetate copolymer film (EVA) having a Shore D type hardness of 30 as used in Example 1 was used as a base film and a polypropylene film having a Shore hardness of 80 ( PP) as an auxiliary film to produce a wafer processing film in the same manner as in Example 1, and back surface polishing of a semiconductor silicon wafer is performed using the obtained wafer processing film to obtain the thickness of the base film and the auxiliary film. It shows the relationship between the workability of the polishing process and the damage rate of the wafer during polishing.

The results in Table 2 show that the damage rate of the wafer was 20 when the resist ink of Comparative Example 1 was used, and Comparative Example 3
In contrast to the damage rate of 76 sheets when the Shore D type hardness was 50, the damage rate was 8 even if each of the base film and the auxiliary film was 10 μm. The effect of the present invention is shown. The results in Table 3 show that the workability is slightly affected by the structure of the wafer processing film.

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Claims (1)

[Claims] 1. A wafer processing film used for polishing the back surface of a silicon wafer having an integrated circuit formed on the surface and having irregularities, the thickness being selected from an ethylene-vinyl acetate copolymer film and a polybutadiene film. Ten
To 2000 μm and a Shore D type hardness of 40 or less, an auxiliary film having a Shore D type hardness of more than 40 and a thickness of 10 to 1000 μm is laminated on one surface of the substrate film. An adhesive layer selected from the group consisting of acrylic, ester, urethane and synthetic rubbers is disposed on the other surface of the film, and the adhesive layer is adhered to the wafer surface for polishing the back surface of the wafer. Wafer processing film used.