JPH0817777A - Method for washing silicon wafer - Google Patents

Abstract

PURPOSE:To prevent adhesive constituents from being transferred to the mirror surface of a wafer and to prevent particles from being adhered again by specifying the surface roughness of a silicon wafer dipped into HF solution after mirror polishing. CONSTITUTION:The surface roughness of silicon wafer where the silicon wafer after mirror polishing is dipped into HF solution is set to 2mum or less in terms of Rmax value. Therefore, after the mirror polishing, a specific etching treatment is performed, thus controlling the surface roughness of the silicon wafer. Hence, since the surface roughness of the wafer in the HF solution is highly flat, an adhesive constituent which is in the HF solution or melted into it cannot be adhered to the wafer surface even if the constituent tends to be bonded or adhered to the wafer surface. Namely, treatment for improving glossiness (flatness) on etching, for example, treatments to increase in etching temperature, increase in etching machining allowance, and change in etching liquid composition are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cleaning a silicon wafer, more specifically, to reduce particles caused by residual polishing agent when cleaning a mirror wafer with HF, and to prevent reattachment of particles in an HF solution. For improvements. More specifically, the present invention relates to a method for suppressing adhesion of particles in an HF solution due to residual polishing adhesive and the like by performing predetermined etching on a mirror wafer to control its surface roughness.

[0002]

2. Description of the Related Art Generally, a mirror wafer is manufactured through a lapping process, a mirror polishing process, an etching process and the like. In this wafer mirror polishing step, for example, alumina powder was used as a polishing agent, and wax or the like was used as a polishing adhesive. As a result, a small amount of wax, which is a polishing adhesive component, remains on the front and back surfaces of the wafer after polishing.

The removal of the adhesive component has been performed by a chemical treatment such as a redox treatment with an SC-1 cleaning solution (alkali solution + hydrogen peroxide solution). Or this SC-1
After washing, it was subjected to physical treatment using ultrasonic waves. However, the wax attached to the front and back surfaces of the wafer has not been sufficiently removed only by the former chemical treatment. In addition, the latter physical treatment has a disadvantage that the equipment and the number of steps are increased. Therefore, conventionally, after the completion of the wafer processing step, in order to remove the adhesive component, the immersion treatment in the HF solution and the cleaning treatment are performed again.

[0004]

However, in such a conventional HF cleaning process, a wafer cassette carrying a plurality of wafers is dipped in an HF solution. Therefore, between the plurality of wafers in the wafer cassette, the adhesive component in the HF and the particles captured in the oxide film are present on the mirror surface (front surface) of the other wafer facing the back surface of the one wafer. There was the inconvenience of being transferred. That is, the HF cleaning deteriorates the particle cleanliness of the wafer surface.

Further, there is a problem that the mass production line is adversely affected by the carry-in of the reattached particle component after the adhesive removing process.

Therefore, as a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have set a condition under which the adhesive can be relatively efficiently removed by controlling the surface roughness of the polished wafer. I found it. That is, by making the surface roughness of the wafer 2 μm or less in Rmax value, it became possible to make the chemical treatment or the physical treatment which is the polishing agent removal treatment more effective. This is Rmax
This is because the decrease in the value gradually reduces the unevenness represented by the surface roughness and reduces the contact area between the adhesive and the wafer surface. It is also considered that this is due to the effect of suppressing the electrostatic coupling force between the front and back surfaces of the wafer and the adhesive to a small extent and the easy penetration of the cleaning liquid due to the decrease in the apparent contact angle.

According to the present invention, it is possible to prevent the transfer of the adhesive component to the mirror surface of the wafer and the re-adhesion of particles by the dipping in the HF solution and to keep the particle cleanliness of the wafer surface in a good condition. Has an aim.

[0008]

According to a first aspect of the present invention, in a method of cleaning a silicon wafer in which a mirror-polished silicon wafer is immersed in an HF solution, the surface roughness of the immersed silicon wafer is represented by Rmax value. 2 μm
The following is the method of cleaning a silicon wafer.

The invention described in claim 2 is the method for cleaning a silicon wafer according to claim 1, wherein the surface roughness of the silicon wafer is controlled by performing a predetermined etching treatment after mirror polishing.

[0010]

According to the method for cleaning a silicon wafer according to the present invention, the surface roughness of the wafer in the HF solution is highly flat, and as a result, the adhesive component in the HF solution or dissolved in the HF solution is deposited on the wafer surface. Even if they try to bond or attach, they do not attach. More specifically, a treatment for increasing the glossiness (flatness) during etching, for example, raising the etching temperature, increasing the stock removal of etching, changing the composition of the etching solution, etc. is performed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. It is known that a silicon wafer after etching treatment, which is a polished material, has a constant surface roughness due to a chemical reaction as shown in FIG. 1 when etching by a mixed acid treatment is adopted. ing. The glossiness shown in FIG. 1 is a numerical value in which the roughness of the surface is evaluated by irradiating a target surface with a constant amount of light and measuring the amount of light reflected at this time. Therefore, it can be seen that the surface roughness Rmax value has a certain correlation with the glossiness. For this measurement, for example, a gloss measuring instrument manufactured by Nippon Denshoku Co., Ltd. is used.

Polishing materials (silicon wafers) having various glossinesses, that is, various surface roughnesses produced during the mixed acid etching treatment were coated with a predetermined adhesive and then polished. H
For F cleaning, a 5% volume concentration HF solution was used. In this HF solution, 25 5-inch wafers were held in a cassette to confirm the effect of removing the polishing adhesive.

FIG. 2 shows H for each glossiness (surface roughness).
The average value of the transfer particles from the F solution is shown. FIG. 2 shows the ease of removing particles during cleaning. It can be confirmed that the amount of transfer particles exponentially decreases as the glossiness increases (roughness decreases and flattens). For the average glossiness, a sample wafer manufactured by changing the etching removal allowance to 30 to 40 μm is used. The HF transfer evaluation method is to measure particles on the surface after dipping in a 5% HF solution for 10 minutes with a particle counter (Surfscan: manufactured by Tencor Co., Ltd.).

FIG. 3 shows the relationship between the glossiness of the material and the amount of adhered particles when 5% of the clean HF solution is forcibly contaminated with latex particles. this is,
Only the ease of redeposition of particles from the HF solution is shown. In advance, the concentration of latex particles 0.3 μm was adjusted to 13000 particles / 10 ml in a 5% HF solution. The sample wafer manufactured by the method shown in FIG. 2 was dipped in this for 1 minute and 10 minutes, and then the number of particles was similarly counted. As a result, it can be seen that the amount of redeposited particles is also suppressed by the improvement (flattening) of the material roughness.

Finally, the result of suppressing the transfer particles in HF as shown in FIG. 4 by the above two effects was obtained. At this time, the surface roughness is 1.5 μm or more and 2.
It is 0 μm or less. 1.5 μm ≦ Rmax ≦ 2.0 μm
Is.

[0016]

According to the present invention, transfer of particles to the wafer surface in the HF solution can be suppressed.

[Brief description of drawings]

FIG. 1 is a graph showing a correlation between glossiness and surface roughness after etching treatment in a silicon wafer cleaning method according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between glossiness after etching treatment and transfer particles in the silicon wafer cleaning method according to the embodiment of the present invention.

FIG. 3 is a graph showing a relationship between glossiness after etching treatment and particles due to redeposition with an HF solution in a method for cleaning a silicon wafer according to an embodiment of the present invention.

FIG. 4 is a graph showing the effect of reducing particles in the method for cleaning a silicon wafer according to an embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunari Takaishi 3-8-16 Iwamotocho, Chiyoda-ku, Tokyo Sanryo Material Silicon Co., Ltd. (72) Inventor Kenji Hori 3-chome Iwamoto-cho, Chiyoda-ku, Tokyo No. 16 Sanritsu Material Silicon Co., Ltd.

Claims (2)

[Claims] 1. A silicon wafer after mirror polishing is subjected to HF.
A method for cleaning a silicon wafer immersed in a solution, wherein the surface roughness of this immersed silicon wafer is 2 μm or less in Rmax value. 2. The method for cleaning a silicon wafer according to claim 1, wherein the surface roughness of the silicon wafer is controlled by performing a predetermined etching treatment after mirror polishing.