JP2003347255A - Method of polishing semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of polishing a semiconductor substrate by the use of a protective sheet which is capable of reducing irregularities which are caused by insufficient conformity between the sheet and wax, its own irregularities, or its own dust. <P>SOLUTION: As to its material, the protective sheet 101 is formed of dust-free paper so that conformity between the sheet 101 and wax 3a and 3b is better than that between a synthetic resin and the wax 3a and 3b. The sheet 101 has less irregularities on its surface and makes less dust than parchment paper and possesses both proper conformity and smoothness. As to its form, the sheet 101 is formed with an opening 102 at its center so as to reduce the area of contact between the sheet and the surface 1a of the semiconductor substrate 1 and to lower probability that a wiring pattern is crushed by the irregularities of the protective sheet 101. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of attaching one surface of a semiconductor substrate to a fixture via a protective sheet,
The present invention relates to a method for polishing a semiconductor substrate for polishing the other surface.

[0002]

2. Description of the Related Art An example of a conventional method for polishing a semiconductor substrate is shown in FIGS. FIG. 3 is a perspective view and a sectional view showing a method of attaching a semiconductor substrate to a fixture.
FIG. 5 is a perspective view showing a method of polishing the back surface of the semiconductor substrate attached to the fixture, and FIG. 5 is a cross-sectional view showing a method of removing the semiconductor substrate whose back surface polishing has been completed from the fixture.

First, as shown in FIG. 3A, a method of attaching a semiconductor substrate 1 to a fixture 2 is as follows: a solid wax (hot melt type) 3a, a protective sheet 4, a solid wax ( Hot-melt type) 3b are laminated in this order, and the semiconductor substrate 1 is placed thereon with the front surface 1a (wiring pattern forming surface) facing downward. And
Heating is performed on a hot plate 6 having a built-in heating heater 5 to melt the solid waxes 3a and 3b as adhesives, so that the solid waxes 3a and 3b adapt to the respective bonding surfaces.

The purpose of interposing the protective sheet 4 between the semiconductor substrate 1 and the fixture 2 is that a wiring pattern (not shown) formed on the front surface 1a of the semiconductor substrate 1 is used for this bonding operation and subsequent steps. In addition to using the elasticity of the protective sheet 4 to prevent the semiconductor substrate 1 from being crushed by the pressure of the polishing operation, after the back surface polishing is completed, the semiconductor substrate 1 is slid laterally to separate from the fixture 2. This is for preventing the surface 1a of the semiconductor substrate 1 from being scratched by preventing the surface 1a of the substrate 1 from directly rubbing against the fixture 2. As the protective sheet 4, a sheet made of a synthetic resin such as a fluororesin, which has a smooth surface and a small coefficient of friction, is usually used. In addition, although the coefficient of friction is larger than that of synthetic resin, it has good compatibility with wax. Therefore, sulfuric acid paper having a relatively dense structure (kraft pulp sheet is treated with sulfuric acid having a concentration of 62 to 68% to swell cellulose. Paper).

Next, when the solid waxes 3a and 3b are melted, the fixture 2 is transferred from the hot plate 6 to the press stage 7 of the press as shown in FIG. Before the 3b cools down and hardens, the pressing unit 8 is lowered from above and the back surface 1 of the semiconductor substrate 1 is lowered.
b. The tip of the pressurizing section 8 is made of, for example, silicon rubber so that the back surface 1b of the semiconductor substrate 1 is not damaged or cracked.

Next, when the attachment of the fixture 2 and the semiconductor substrate 1 is completed, as shown in FIG. 4, the fixture 2 to which the semiconductor substrate 1 has been attached is set in a polishing apparatus 9 and the back surface is polished. The polishing apparatus 9 includes a surface plate 10 connected to a rotation drive unit (not shown), a rotatable support shaft 11 for pressing the fixture 2 against the surface plate 10, and a polishing liquid 1.
And a nozzle 13 for supplying the polishing liquid 2 to the surface plate 10 at an arbitrary pressure.
The fixture 2 is rotated by rotating the platen 10 while supplying the substrate 2, and the back surface 1b of the semiconductor substrate 1 is polished to a desired thickness.

Next, when the back surface polishing is completed, the semiconductor substrate 1 is separated from the fixture 2. Fig. 5
As shown in (a), the fixture 2 to which the semiconductor substrate 1 is attached is placed on a hot plate 6 and heated to melt the waxes 3a and 3b, and the tip has a shape following the outer shape of the semiconductor substrate 1. The side surface of the semiconductor substrate 1 is pushed by the exclusive peeling jig 14 and is slid over the fixture 2 to be separated. At this time, since the protective sheet 4 is interposed between the semiconductor substrate 1 and the fixture 2, the surface 1 of the semiconductor substrate 1
a can be prevented from being damaged. After that, as shown in FIG. 5B, the protection sheet 4 is peeled off from the front surface 1a of the semiconductor substrate 1 with tweezers 15. Then, as shown in FIG. 5C, the wax 3b remaining on the semiconductor substrate 1 is dissolved and removed with a solvent such as IPA (isopropyl alcohol) to complete the back surface polishing.

[0008]

However, the conventional method of polishing a semiconductor substrate has the following problems. As described above, as the material of the protective sheet, a synthetic resin having a smooth surface, or sulfuric acid paper is used.
Although the structure is very dense, it is good in protecting the surface of the semiconductor substrate, but on the contrary, the water repellency is too strong and the compatibility with the wax is poor. Due to the surface tension, the smoothness of the wax was deteriorated, and gently unevenness was sometimes generated on the surface. On the other hand, in the case of parchment paper, although the cellulose is swollen in the pulp fiber, many fiber shapes that have not been flattened still remain, and the compatibility with the wax is good, but the fiber shape is inevitably relatively large on the surface. Appears as irregularities. In addition, it was unavoidable that irregularities due to dust (about 5 μm) generated from the pulp fiber were generated.

That is, when a synthetic resin is used as the protective sheet, unevenness occurs due to poor compatibility with wax,
When parchment paper is used, there is no problem in compatibility with the wax, but there is a problem that irregularities due to the fiber shape itself or dust generated from the fiber occur. In particular, when the semiconductor substrate has an aerial wiring (air bridge wiring) structure provided to reduce the parasitic capacitance of the high-frequency circuit wiring, the wiring pattern is easily broken, so that slight unevenness which has not been a major problem in the past. Became a problem that could not be ignored.

An object of the present invention is to provide a method for polishing a semiconductor substrate using a protective sheet having less irregularities caused by insufficient adaptation between the protective sheet and wax, irregularities of the protective sheet itself or irregularities due to dust from the protective sheet. Things.

[0011]

According to a polishing method for a semiconductor substrate of the present invention, one surface of a semiconductor substrate is attached to a fixture via a protective sheet, and the other surface of the semiconductor substrate is polished. The method for polishing a semiconductor substrate is characterized in that the protective sheet is made of dust-free paper.

[0012]

1 and 2 show an example of a method for polishing a semiconductor substrate according to the present invention. FIG. 1 is a perspective view and a cross-sectional view illustrating a method of attaching a semiconductor substrate to a fixture, and FIG. 2 is a cross-sectional view illustrating a method of detaching the semiconductor substrate, whose back surface has been polished, from the fixture. Note that FIG.
5 are denoted by the same reference numerals, and the method of polishing the back surface is the same as that of the prior art, and will be described with reference to FIG.

First, as shown in FIG. 1A, a method of attaching a semiconductor substrate 1 to a fixture 2 is as follows: solid wax (hot melt type) 3a, protective sheet 101, solid wax Hot melt type) 3b
Are stacked in this order, and the semiconductor substrate 1 is placed on the surface 1a.
(Wiring pattern formation surface) is placed face down. Here, the protection sheet 101 is made of dust-free paper (paper generally used in a clean room) in which natural pulp is impregnated with a resin emulsion. The outer shape of the protection sheet 101 is slightly larger than the semiconductor substrate 1 and the semiconductor substrate 1 is located at the center. It has a ring shape provided with an opening 102 which is slightly smaller than that of FIG. When the semiconductor substrate 1 is placed on the protective sheet 101, the semiconductor substrate 1 is placed so that the entire outer peripheral portion of the semiconductor substrate 1 is in contact with the ring-shaped protective sheet 101. Then, it is heated on a hot plate 6 having a built-in heating heater 5 to melt the solid waxes 3a and 3b as adhesives and to make them conform to the respective bonding surfaces. At this time, the melted waxes 3a and 3b enter the openings 102 of the protective sheet 101 and mix with each other. That is, the semiconductor substrate 1 and the fixture 2 are bonded via a ring-shaped protective sheet 101 on the outer peripheral portion of the semiconductor substrate 1, and the wax 3 is provided on the opening 102.
In a, 3b, it is directly bonded.

The purpose of interposing the protective sheet 101 between the semiconductor substrate 1 and the fixture 2 is that a wiring pattern (not shown) formed on the surface 1a of the semiconductor substrate 1
By using the elasticity of the protective sheet 4 to prevent the semiconductor substrate 1 from being crushed by the pressure of the pasting operation and the polishing operation in the subsequent step, and to remove the semiconductor substrate 1 from the fixture 2 after the back surface polishing is completed, the semiconductor device 1 is moved in the horizontal direction. This is to prevent the surface 1a of the semiconductor substrate 1 from being directly rubbed against the fixture 2 when the semiconductor substrate 1 is slid, and to prevent the surface 1a of the semiconductor substrate 1 from being scratched.

Since the protective sheet 101 is made of dust-free paper in terms of its material, it does not have as good a compatibility with the waxes 3a and 3b as synthetic resin, and has less unevenness and dust on the surface than parchment paper. It has both moderate familiarity and smoothness. In addition, in terms of its shape, an opening 102 is provided at the center, and the surface 1a of the semiconductor substrate 1 is formed.
The area of contact with the protective sheet 101 is reduced, and the probability that the wiring pattern is crushed by unevenness of the protective sheet 101 is reduced. In addition, the protection sheet 1
01 is in contact with the entire outer periphery of the semiconductor substrate 1, and can sufficiently serve as a spacer for preventing the front surface 1 a of the semiconductor substrate 1 from directly rubbing against the fixture 2. In this case, since the two waxes 3a and 3b are mixed with each other, the adhesive strength between the semiconductor substrate 1 and the fixture 2 can be sufficiently secured.

Next, when the solid waxes 3a and 3b are melted, the fixture 2 is transferred from the hot plate 6 to the press stage 7 of the press machine as shown in FIG. Before the 3b cools down and hardens, the pressing unit 8 is lowered from above and the back surface 1 of the semiconductor substrate 1 is lowered.
b. The tip portion of the pressing portion 8 is made of, for example, silicon rubber or the like so that the back surface 1b of the semiconductor substrate 1 is not damaged or cracked.

Next, when the attachment of the fixture 2 and the semiconductor substrate 1 is completed, as shown in FIG. 4, the fixture 2 to which the semiconductor substrate 1 has been attached is set in a polishing device 9 and the back surface is polished. The polishing apparatus 9 includes a surface plate 10 connected to a rotation drive unit (not shown), a rotatable support shaft 11 for pressing the fixture 2 against the surface plate 10, and a polishing liquid 1.
And a nozzle 13 for supplying the polishing liquid 2 to the surface plate 10 at an arbitrary pressure.
The fixture 2 is rotated by rotating the platen 10 while supplying the substrate 2, and the back surface 1b of the semiconductor substrate 1 is polished to a desired thickness.

Next, when the back surface polishing is completed, the semiconductor substrate 1 is separated from the fixture 2. Fig. 2
As shown in (a), the fixture 2 to which the semiconductor substrate 1 is attached is placed on a hot plate 6 and heated to melt the waxes 3a and 3b, and the tip has a shape following the outer shape of the semiconductor substrate 1. The side surface of the semiconductor substrate 1 is pushed by the exclusive peeling jig 14 and is slid over the fixture 2 to be separated. At this time, it is possible to prevent the surface 1a of the semiconductor substrate 1 from being damaged due to the interposition of the protective sheet 101 between the semiconductor substrate 1 and the fixture 2. Then, FIG.
(B) As shown in FIG.
1 is peeled off from the surface 1 a of the semiconductor substrate 1. And FIG.
As shown in (c), the waxes 3a and 3b remaining on the semiconductor substrate 1 are dissolved and removed with a solvent such as IPA (isopropyl alcohol), and the backside polishing is completed.

In the above example, the shape of the protective sheet is a ring shape having one opening at the center, but the shape and number of the openings are not particularly limited. May be provided. The outer shape of the protective sheet may be smaller than that of the semiconductor substrate, but if it is slightly larger than the semiconductor substrate, the protective sheet is visible when the semiconductor substrate is placed on the protective sheet, and the alignment is easy. However, when the protective sheet is peeled from the semiconductor substrate with tweezers, the protective sheet is easily sandwiched, which is suitable.

[0020]

According to the method for polishing a semiconductor substrate of the present invention, since the material of the protective sheet is made of dust-free paper having both smoothness and compatibility with wax, lack of familiarity between the protective sheet and wax. Unevenness caused by the protective sheet itself, or unevenness due to dust from the protective sheet. Also, if an opening is provided in the protective sheet,
The area in direct contact with the semiconductor substrate can be reduced, and polishing with less risk of crushing the wiring pattern formed on the semiconductor substrate can be performed. In particular, it is suitable for polishing a semiconductor substrate having an aerial wiring (air bridge wiring) structure.

[Brief description of the drawings]

FIG. 1 is a perspective view and a sectional view showing an example of a method for polishing a semiconductor substrate of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a method for polishing a semiconductor substrate according to the present invention.

FIG. 3 is a perspective view and a sectional view showing an example of a conventional method for polishing a semiconductor substrate.

FIG. 4 is a perspective view showing an example of a method for polishing a semiconductor substrate.

FIG. 5 is a sectional view showing an example of a conventional semiconductor substrate polishing method.

[Explanation of symbols]

1 semiconductor substrate 1a Surface of semiconductor substrate 1b Backside of semiconductor substrate 2 Fixture 101 Protective sheet

Claims (4)

[Claims] 1. A polishing method for affixing one surface of a semiconductor substrate to a fixture via a protective sheet and polishing the other surface of the semiconductor substrate, wherein the protective sheet is made of dust-free paper. A method for polishing a semiconductor substrate. 2. The method for polishing a semiconductor substrate according to claim 1, wherein the dust-free paper is a dust-free paper obtained by impregnating a natural pulp with a resin emulsion. 3. The method according to claim 1, wherein the protective sheet has an opening. 4. The method according to claim 1, wherein the semiconductor substrate has an aerial wiring (air bridge wiring) structure.