JP2008124354A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device capable of preventing contact scratches or hitting marks from being formed on a silicon wafer and reducing the warp of the silicon wafer as well in the case of sucking and fixing the silicon wafer to a suction stage. <P>SOLUTION: By coating an ultraviolet-curable resin film 31 on the device forming surface (surface structure 4) of the silicon wafer 1, the contact scratches or the hitting marks are prevented from being formed on the surface structure 4 sucked to the suction stage 32 in the case of grinding the back surface 1a of the silicon wafer 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device using a thin wafer.

In power semiconductor devices (for example, vertical IGBTs (insulation effect bipolar transistors)), silicon wafers have been thinned in recent years in order to improve performance. As shown in FIG. 3, after forming the surface structure 4 of the device on the surface of the silicon wafer 1 as shown in FIG. 3, this thin power semiconductor device is opposite to the device formation surface (surface structure 4) as shown in FIG. After the back surface 1a of the silicon wafer 1 is ground and thinned, a back electrode (not shown) is formed and manufactured.
3A is a cross-sectional view of the main part of the silicon wafer before grinding, and FIG. 3B is a detailed view of part B of FIG. 3A, showing the surface structure 4 of one cell of the IGBT. . The surface structure 4 is composed of a diffusion portion 2 and an upper structure 3. The diffusion portion 2 includes a well region 11 formed in the surface layer of the silicon wafer 1 and an emitter region formed in the surface layer of the well region 11. The upper structure 3 includes a gate insulating film 13, a gate electrode 14, an interlayer insulating film 15, an emitter electrode 16, and a polyimide film 17 serving as a surface protective film.

FIG. 4 shows a case where a resist film is thinned by a conventional method of thinning a silicon wafer, and FIGS. 4A to 4C are cross-sectional views of essential parts shown in the order of processes.
First, in order to grind the back surface 1a of the silicon wafer 1 shown in FIG. 4, a resist film 35 for grinding protection is applied in advance on the surface structure 4 and thermally cured. The resist film 35 is a thermosetting resin film generally used in a semiconductor process ((a) in the figure).
Next, the silicon wafer 1 is sucked and fixed to the suction stage 32 by setting the suction stage 32 of the grinding apparatus on the surface of the resist film 35 and vacuum sucking, and the back surface 1a of the silicon wafer 1 is ground and processed. Is thinned ((b) in the figure).
Next, the silicon wafer 1 is separated from the suction stage 32. Subsequent steps are omitted here.

Patent Document 1 discloses a pressure-sensitive adhesive sheet used for processing a product such as a semiconductor wafer, and a method for manufacturing the pressure-sensitive adhesive sheet that does not damage the semiconductor wafer when the pressure-sensitive adhesive sheet is peeled after processing. ing. This pressure-sensitive adhesive sheet also contains an ultraviolet curable resin.
JP 2004-106515 A

The resist film 35 applied in FIG. 4A is a thin film having a thickness of about 3 μm. When the resist film 32 comes into contact with the adsorption stage 32, the resist film 35 penetrates the resist film 35 as shown in FIG. The surface structure 4 may have a contact scratch 41, a dent 42, or the like. Contact scratches 41 and dents 42 cause a large number of semiconductor elements (IGBT in this case) formed on the silicon wafer 1 to be destroyed and cause a reduction in the yield rate.
There is a method of increasing the thickness of the resist film in order to prevent the contact scratch 41 and the dent 42.
FIG. 6 is a process diagram in the case where the thickness of the resist film is increased, and FIGS. 6A to 6C are main process cross-sectional views shown in the order of processes.
The process is the same as that shown in FIG. 4 except that the resist film 35 is thicker than 10 μm in order to prevent contact scratches 41 and dents 42. By doing so, contact scratches 41, dents 42, and the like can be reduced. However, when the silicon wafer 1 is separated from the suction stage 32, the silicon wafer 1 is greatly warped as shown in FIG. The reason why the amount of warpage increases will be described below.

Since the resist films 35 and 36 conventionally used for grinding protection are thermosetting resins, the organic solvent is volatilized and stress is generated when heat curing is performed. The warp of the silicon wafer 1 caused by this stress increases to several mm or more, particularly when the thickness of the resist film 36 is 10 μm or more.
When the amount of warpage of the silicon wafer 1 increases in this way, there arises a problem that the silicon wafer 1 cannot be transferred by the transfer mechanism of various semiconductor process apparatuses.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to provide a method for manufacturing a semiconductor device in which when a silicon wafer is sucked and fixed to a suction stage, the silicon wafer is free from contact scratches and dents and warpage of the silicon wafer can be reduced. Is to provide.

In order to achieve the above object, in the step of bringing the device forming surface of the silicon wafer into contact and fixing to the desorption support jig, the device forming surface is coated with an ultraviolet curable resin film as a protective film, and the ultraviolet curable resin is coated. After the resin film is irradiated with ultraviolet rays and cured, the ultraviolet curable resin film is brought into contact with the resin film and fixed to a desorption support jig.
Also, in the process of thinning the silicon wafer, a device forming surface opposite to the ground surface is coated with an ultraviolet curable resin film as a protective film, and the ultraviolet curable resin film is irradiated with ultraviolet rays and cured. Thereafter, the ultraviolet curable resin film is fixed in contact with a desorption support jig, and then the ground surface is ground to make the thickness of the silicon wafer 100 μm or less.
Further, in the step of transporting the silicon wafer, the device forming surface of the silicon wafer is coated with an ultraviolet curable resin film as a protective film, and the ultraviolet curable resin film is irradiated with ultraviolet rays and cured, It is set as the manufacturing method which fixes and conveys by making it contact with a removal | desorption support jig | tool.

The desorption support jig may be a suction stage that can desorb the silicon wafer.
The wavelength of the ultraviolet light is preferably 200 to 400 nm.

According to the present invention, when the back surface opposite to the device formation surface of the silicon wafer is ground by coating the device formation surface of the silicon wafer with the ultraviolet curable resin film, the device formation surface is attracted to the suction stage. Contact scratches and dents can be prevented.
This can improve the problem of destroying a large number of semiconductor elements formed on the wafer surface.
Further, by coating the silicon wafer with the ultraviolet curable resin film, the warpage amount of the silicon wafer can be suppressed to be small, and other processes other than the silicon wafer conveyance process and the grinding process can be favorably performed.

  When a silicon wafer is thinned, in the prior art, contact scratches or dents are generated by the suction stage of a grinding apparatus, or the silicon wafer is warped by a protective film coated on the silicon wafer. To prevent this, use an ultraviolet (UV) curable resin film that is made of a low-stress material and has an excellent ability to protect the silicon wafer surface, instead of the resist film that has been used as a protective film. The above problem was solved. This will be specifically described in the following examples.

FIGS. 1A to 1E are process diagrams showing a method of manufacturing a semiconductor device according to a first embodiment of the present invention. FIGS. 1A to 1E are cross-sectional views showing a main part manufacturing process shown in the order of steps. In this process diagram, the grinding process of the silicon wafer 1 is taken as an example. In addition, the same code | symbol was attached | subjected to the same site | part as FIG. Moreover, although IGBT was mentioned as an example as a semiconductor device, it is not restricted to this.
First, an ultraviolet curable resin whose state before curing is liquid is spin-coated (spin coated) on the device forming surface (surface structure 4) of the silicon wafer 1 using a spin coater. The spin coater is formed so as to have a thickness of 30 μm by controlling the rotation speed and the rotation time. Immediately after spin coating, ultraviolet rays (365 nm) are irradiated and cured to form an ultraviolet curable resin film 31 (FIG. )). The wavelength of ultraviolet light is preferably in the range of 200 nm to 400 nm. If it is out of this range, the curability by ultraviolet rays decreases.

Next, a suction stage 32 (a stage that sucks in vacuum) of a grinding apparatus is set on the ultraviolet curable resin film 31 and vacuum suction is performed to fix the silicon wafer 1 to the suction stage 32 by vacuum suction. The back surface 1a is ground to grind the back surface so that the thickness of the silicon wafer becomes 90 μm ((b) in the figure).
Specifically, the ultraviolet curable resin film 31 formed on the device formation surface (surface structure 4) is adhered and fixed to the suction stage 32 of the grinding apparatus, and the opposite grinding surface (back surface 1a) is fixed. It is pressed against a rotating grinding table (not shown) and ground to a thickness of 100 μm or less. The in-plane distribution of the thickness of the silicon wafer 1 after this grinding step was in the range of 87 to 93 μm, and good results were obtained.
Next, the silicon wafer 1 is removed from the suction stage 32 ((c) in the figure).

Next, an adhesive tape (not shown) is attached to the ultraviolet curable resin film 31, and the adhesive tape is pulled upward to peel off the ultraviolet curable resin film 32 fixed to the adhesive tape from the silicon wafer 1, and then the back surface structure on the back surface 1b side. 18 is formed, and then the silicon wafer 1 is cut along a dicing line (cut line 33) (FIG. 4D).
After cutting, the silicon wafer 1 becomes a semiconductor chip (in this case, an IGBT chip) ((e) in the figure).
FIG. 2 is a detailed view of part A of FIG. 1 (e), and is a cross-sectional view of the main part of one cell of the IGBT. Since the surface structure 4 has been described with reference to FIG. 3, the description thereof is omitted here. The back surface structure 18 includes a collector region 19 formed on the back surface 1 b of the silicon wafer 1 and a collector electrode 20 formed on the collector region 19.

After the grinding step of FIG. 1B, the UV curable resin film 31 is removed from the silicon wafer and the appearance of the device formation surface (surface structure 4) is inspected. No dent 42 or the like was generated. This is because the thickness of the ultraviolet curable resin film 31 is about 30 μm, which is about three times the film thickness of the conventional resist film 36. If the thickness of the ultraviolet curable resin film 31 is about 10 μm or more, it will be effective in preventing contact scratches and dents.
The ultraviolet curable resin film 31 can be thickened in this way because it is cured at room temperature by irradiating with ultraviolet rays (wavelength 200 to 400 nm), and therefore has less volatile components and less stress generation than a thermosetting resist film. Because.
As described above, since the ultraviolet curable resin film 31 has few volatile components and generates less stress, the warpage amount of the silicon wafer 1 is extremely small. Even when the film thickness is 30 μm, the warpage amount of the silicon wafer 1 is 1 μm or less. . In other words, there is almost no warping.

In addition, the silicon wafer 1 coated with the ultraviolet curable resin film 31 is warped as compared with the thermosetting resist film even when subjected to heating or cooling during the process in the course of sequentially processing the semiconductor process steps. There are few things. After the thermal history, when the amount of warpage of the silicon wafer 1 was measured, it was about 1 mm as described above. The silicon wafer has a diameter of about 6 inches to 8 inches and a thickness of about 90 μm.
In addition, since the heat curing treatment essential for the resist films 35 and 36 is not necessary for the ultraviolet curable resin film 31, the process time can be shortened and the manufacturing cost can be reduced.
In this case, the ultraviolet curable resin film 31 is formed on the surface of the silicon wafer 1 by the spin coat method, but there is a printing method as another method. The main component of the ultraviolet curable resin film 31 is an acrylic resin or an epoxy resin.

  Further, when the ultraviolet curable resin film 31 is coated on the silicon wafer 1, the warpage of the silicon wafer 1 is extremely small, so that the present invention can be applied not only to the grinding process but also to other processes such as a transport process. In the case of a transfer process, the same effect can be obtained by applying the present invention to the case where the silicon wafer 1 is fixed to a stage with claws instead of the suction stage 32.

BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows the manufacturing method of the semiconductor device of 1st Example of this invention, (a)-(e) is principal part manufacturing process sectional drawing shown in order of the process It is the A section detail drawing of Drawing 1 (e), and the principal part sectional view of 1 cell of IGBT It is a silicon wafer before grinding, (a) is a cross-sectional view of the main part, (b) is a detailed view of B part of (a), a diagram of the surface structure part of one cell of IGBT It is process drawing at the time of making a resist film thin with the conventional method of thinning a silicon wafer, (a)-(c) is a principal part process sectional view shown in process order Cross-sectional view of the main part with scratches and dents on the suction stage It is process drawing at the time of making a resist film thick, (a)-(c) is a principal part process sectional view shown in process order Diagram showing the amount of warpage of silicon wafer increased

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon wafer 1a, 1b Back surface 2 Diffusion part 3 Upper structure 4 Surface structure 10 Silicon substrate 11 Well region 12 Emitter region 13 Gate insulating film 14 Gate electrode 15 Interlayer insulating film 16 Emitter electrode 17 Polyimide film 18 Back surface structure 19 Collector region 20 Collector Electrode 31 UV curable resin film 32 Adsorption stage 33 Cutting line 35 Resist film (thin)
36 Resist film (thick)
41 Contact scratch 42 Scar

Claims (4)

In the process of contacting the device forming surface of the silicon wafer and fixing it to the desorption support jig, the device forming surface is coated with an ultraviolet curable resin film as a protective film, and the ultraviolet curable resin film is cured by irradiating with ultraviolet rays. Then, the ultraviolet curable resin film is brought into contact with and fixed to a desorption support jig. In the process of thinning a silicon wafer, after coating the device forming surface opposite to the ground surface with an ultraviolet curable resin film as a protective film, the ultraviolet curable resin film is irradiated with ultraviolet rays and cured. The method of manufacturing a semiconductor device, wherein the ultraviolet curable resin film is fixed in contact with a desorption support jig and then the ground surface is ground to make the thickness of the silicon wafer 100 μm or less. In the process of transporting the silicon wafer, the device forming surface of the silicon wafer is coated with an ultraviolet curable resin film as a protective film, and the ultraviolet curable resin film is irradiated with ultraviolet rays and cured, and then the silicon wafer is attached and detached. A method of manufacturing a semiconductor device, wherein the semiconductor device is fixed and transported in contact with a jig. The method for manufacturing a semiconductor device according to claim 1, wherein the desorption support jig is a suction stage that can desorb the silicon wafer.

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