JPH0715895B2 - Substrate surface cleaning method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for cleaning a surface of a semiconductor substrate, for example, a method for cleaning a surface of a silicon wafer in a manufacturing process of a semiconductor integrated circuit (IC).

(2) Background of the technology In order to prevent impurities from entering the silicon substrate during the IC manufacturing process, the silicon wafer is frequently cleaned.
In a general process, a wafer is first cleaned, an oxide film is formed on the surface of the wafer by thermal oxidation, a resist is applied using a mask to perform various treatments, cleaning is performed after the resist is removed, and then heat treatment is performed. Cleaning is done at very many stages of the process, such as performing and then cleaning. If the heat treatment is performed while the resist remains or other organic impurities adhere to the surface of the substrate, the impurities will soak into the substrate and adversely affect the characteristics of the manufactured IC. is there.

Although various chemicals are used to clean wafers, sulfuric acid (H ₂
The temperature of a mixed solution of SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) is raised to about 100 ° C., and the wafer is first cleaned including resist removal by using it, and then washed again with pure water. There are typically a dipping method shown in FIG. 1 (a) and a spraying method shown in FIG. 1 (b), in which 1 is a silicon wafer, 2 is a quartz heating tank, and 3 is a mixed liquid. Supply pipes 4 indicate heaters.

In the dip method, the wafer 1 is immersed in the bath 2 filled with the mixed liquid 5 of H ₂ SO ₄ + H ₂ O ₂ , and the mixed liquid is heated to about 100 ° C. by the heater 4 below the bath.

In the spray method, the mixed liquid heated to 100 ° C. is ejected in a mist form from the supply pipe 3 to clean the wafer 1.

(3) Prior art and problems The conventional dip method requires a heating tank provided with a heater, and the spray method requires injection of a pre-heated mixed liquid.
There were safety issues in its processing and operation. The mixed liquid heated to 100 ° C invades the heating tank and the mixed liquid supply pipe itself, and the device and piping materials may be mixed in the mixed liquid used for cleaning. In that case, complete cleaning cannot be performed. It is extremely difficult to manufacture and operate, while using a heater or heating the mixed liquid up to 100 ° C has a problem of power consumption.

(4) Object of the Invention In view of the above-mentioned conventional problems, the present invention provides a method for cleaning a substrate surface, which does not require a heater or mixed liquid heating, has a degree of freedom in designing devices, piping materials and the like and has improved safety. The purpose is to

(5) Structure of the invention According to the present invention, the rotatable and substrate to be cleaned is placed on the chuck, and the chemical liquid is dropped onto the substrate while rotating the substrate. In a substrate surface cleaning method for cleaning a substrate, a step of supplying water to the surface of the substrate, and then, while rotating the substrate, olium (mixture of sulfuric acid and sulfuric anhydride), the water, and hydrogen peroxide, Mixing at a position adjacent to the substrate surface to be cleaned and dripping on the substrate surface.

(6) Embodiments of the Invention Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The present invention takes advantage of the fact that when water is added to olium, anhydrous sulfuric acid (SO ₃ ) in olium reacts with water to generate sulfuric acid, and hot concentrated sulfuric acid heated by large reaction heat is obtained.

SO ₃ + H ₂ O → H ₂ SO ₄ + 21Kcal / mg And experiment on the concentration of anhydrous sulfuric acid in orium, the amount of water added and the calorific value at that time, and the concentration of sulfuric acid (the degree of washing is directly proportional to the sulfuric acid concentration) I made it.

In this experiment, the apparatus shown in the sectional view in FIG. 2 was used.
In the figure, 11 is a four-necked flask (capacity 500 ml), 12
Is a tank filled with the heat insulating material 13, 14 is a depressurizing port, 15 is a container for mixing an olium and sulfuric acid solution, 16 is a stirring motor of 64 rpm, 17 is a thermometer, and 18 is water (H ₂ O). The following data were obtained by experiments using such a device.

In the above data, an olium concentration of 0 indicates that only sulfuric acid was used, and 5%, 7% ... indicates that sulfuric acid was mixed with 5%, 7%. From this data, the concentration of olium is 5%
From 25 to 25%, the sulfuric acid temperature was 60 ℃ to 145 ℃, and the sulfuric acid concentration was 97.4% to 98.0%.

A first embodiment of the present invention is shown in a sectional view in FIG. 3, in which 21 is a bath, 22 is a wafer, 23 is a vacuum rotary chuck,
24 is an oleum supply pipe, 25 is a water supply pipe, 26 is a hydrogen peroxide solution supply pipe, and the supply pipes 24 and 25 are connected to the first supply pipe 27, and the first supply pipe 27 and the hydrogen peroxide water supply pipe A second supply pipe 28 is formed by combining with 26.

The operation sequence follows the diagram of FIG. 4, and in this diagram, the lapse of time progresses in the direction of the arrow t, and each line of ~ represents the supply state of water, hydrogen peroxide solution, and orium, and is high in each line. The level is on (supply) and the low level is off (supply stopped).

First, as shown by the line, the water supply pipe 25 is turned on to supply H ₂ O to pre-clean the wafer 22.

Then, as shown by the line, hydrogen peroxide solution is supplied from the pipe 26, and water and hydrogen peroxide solution are dropped on the wafer.

Next, as shown by the line, olium is supplied from the tube 24, and the mixed liquid of the three is dropped on the wafer.

On the other hand, since the chuck 23 is rotating at the same time as the water supply (Rot.) As shown by the line in the figure, the cleaning of the wafer is performed during the ON state. After the end of cleaning is offset, the supply of hydrogen peroxide solution is stopped, and then the post-cleaning is performed only with water, and then the rotation of the chuck (Rot.) Is stopped. Then, the above operation is repeated for each wafer.

In the apparatus shown in FIG. 3, a conventional tube may be used as the olium supply tube because the mixed solution has not yet generated heat. Since the first supply pipe 27 generates heat at about 100 ° C. as described above, the first supply pipe is made of a heat resistant material such as quartz or ceramic, and the heat generated in the first supply pipe 24, 2
Insulation 29 is used to shield tubes 24 and 25 from tube 27 so that they do not transfer to 5. The second supply pipe 28 is also made of a heat resistant material like the pipe 27.

In the examples, when the heat generation of 100 ° C. is not obtained, the preliminary heater (not shown) is used for heating. The heater is not limited to resistance heating, but lamp heating or the like can be considered. The scope of application of the present invention is not limited to the above wafer cleaning.

(7) Effects of the Invention As described in detail above, according to the present invention, the heating heater can be omitted, and the heating energy can be saved even when the preliminary heating heater is required (the conventional method is the total heating. In addition, since the heating is performed after the pipe outlet, the degree of freedom in designing the piping material and the safety are increased, and it is effective in improving the yield in the semiconductor device manufacturing.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a conventional apparatus for cleaning a silicon wafer, FIG. 2 is a sectional view of an apparatus used in an experiment for the present invention, and FIG. 3 is used for a first embodiment of the present invention. FIG. 4 is a sectional view of the apparatus, and FIG. 4 is a diagram showing an operation sequence of the apparatus of FIG. 21 ... Tank, 22 ... Silicon wafer, 23 ... Vacuum chuck, 24 ... Orium supply pipe, 25 ... Pure water supply pipe, 26 ...
Hydrogen peroxide water supply pipe, 27 …… first supply pipe, 28 …… second supply pipe, 29 …… insulation material

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kunihiko Wada 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Riki Ogawa, 1015, Uedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited ( 72) Inventor Koichi Takami 2-5-2 Marunouchi, Chiyoda-ku, Tokyo Sanryoseikagyo Co., Ltd. (72) Inventor Haruo Ushida 1447, Fujita, Hachimansai-ku, Kitakyushu, Fukuoka Mitsubishi Kasei Kurosaki Plant (56) Reference JP-A-53-101975 (JP, A)

Claims (3)

[Claims] 1. A substrate surface cleaning method for cleaning a substrate that is rotatable and is mounted on a chuck, and a chemical solution is dropped onto the substrate while rotating the substrate. A step of supplying water to the surface of the substrate, and then, while rotating the substrate, olium, the water,
And a step of mixing hydrogen peroxide at a position adjacent to the surface of the substrate to be cleaned and dropping the mixture onto the surface of the substrate. 2. In the step of mixing the olium, water, and hydrogen peroxide, the olium is mixed with the water at a position adjacent to the surface of the substrate to be cleaned, and the mixed solution thus obtained and the peroxide are mixed. The substrate surface cleaning method according to claim 1, wherein hydrogen is mixed and dropped on the substrate surface. 3. The method for cleaning a substrate surface according to claim 1, wherein the mixing ratio of anhydrous sulfuric acid in sulfuric acid in the olium is in the range of 5% to 25%.