JPS60201636A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable plural oxide films having different thicknesses to be formed simultaneously, by oxidizing a silicon wafer after previously implanting nitrogen into the surface of a section of the silicon wafer where a thinner oxide film is to be formed. CONSTITUTION:The surface of a silicon substrate is covered with a resist film 13 in a section (a). When nitrogen ions are implanted into the silicon substrate, no nitrogen penetrates into the section (a) while the section (b) is implanted with nitrogen atoms (n). The resist film is removed after completion of the ion implantation. The substrate is then thermal oxidized under certain conditions. A thin oxide film 14 is thereby formed on the surface of the section (b) where the rate of oxidation is controlled by the presence of nitrogen. On the surface of the section (a) where no nitrogen atoms are implanted, however, a thick oxide film 15 is formed according to the conditions in accordance with the temperature and the duration of the thermal oxidation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device, in which a plurality of gate oxide films having different thicknesses are formed on the surface of a single silicon substrate by simultaneous heat treatment. Regarding the method.

Background of the Technology In recent years, it is often necessary to form oxide films of different thicknesses on the surface of the same silicon substrate, such as insulating films for MO3 semiconductors, due to the difference in required breakdown voltage.

(C) Conventional technology and problems Conventionally, in order to form an oxide film in such cases, the first oxide film having a certain thickness is coated over the entire silicon substrate in order to oxidize the film by changing the heat treatment conditions for each film thickness. After the first oxide film is formed by heat treatment or the like, the part to be left as the first oxide film is covered with a resist film, and the part where the second oxide film having a different thickness from the first oxide film is to be formed is covered with the first oxide film. Therefore, after removing the oxide film by etching, heat treatment is performed again under oxidizing conditions to form a second oxide film.

In such a manufacturing process, manufacturing becomes complicated and control of forming the oxide film thickness becomes difficult, and there is a desire to improve this.

An outline of the conventional manufacturing method will be explained with reference to FIG.

Figure 1 (11 shows a field oxide 2 on the surface of a silicon substrate 1, on both sides of which there is a part a where a first oxide film is to be formed and a part b where a second oxide film is to be formed). Assume that there is.

In Figure 1 (2), a silicon substrate is heat-treated to form the first oxide 3 on both parts a and b, and the saponified film is oxidized to a specified thickness. It is formed under the control of a device.

In FIG. 1(3), the surface of the first oxide film in part a is covered with a resist film 4 in order to leave the first oxide film in part a and form a second oxide film in part b. This is then immersed in an etching solution to remove the first oxide film at section b.

] 131T41, after the etching is completed and the resist film 4 is removed, the silicon substrate is thermally oxidized again to form a second oxide film on the b part.
FIG.

There are many drawbacks to this manufacturing process, especially the first
After the second oxide is formed, the portion where the second oxide film is to be formed is etched, resulting in contamination of the surface of the silicon substrate and poor cleanliness during the manufacturing process.

Furthermore, since the silicon substrate is oxidized twice, the first oxide film is oxidized again in the oxidizing atmosphere, which makes it difficult to control the thickness of the first oxide film.

Due to the above drawbacks, quality deterioration in the silicon substrate manufacturing process is unavoidable, and a manufacturing method that improves this is desired.

(d) Purpose of the Invention In view of the above-mentioned conventional drawbacks, an object of the present invention is to provide a method for simultaneously forming a plurality of oxide films having different thicknesses on the surface of a single silicon wafer.

(e) Structure of the Invention This object is to form oxide films of different thicknesses on the surface of a single silicon wafer. This can be achieved by providing a method for manufacturing a semiconductor device characterized by simultaneously forming oxide films of different thicknesses by oxidizing a wafer.

(f) Embodiments of the Invention The present invention utilizes the chemical phenomenon that by implanting nitrogen atoms into the surface of a silicon substrate, the oxidation rate of silicon is significantly suppressed in this area. When forming multiple parts with different thicknesses, a predetermined amount of nitrogen atoms are injected into the thinner parts in advance.
By leaving the thicker parts as they are and simultaneously oxidizing the silicon substrate under the same conditions,
A plurality of oxide films with different thicknesses are formed, which helps to clean the manufacturing process and simplify the heat treatment process, which has great effects in terms of quality improvement and economic efficiency.

FIG. 2 is a detailed explanation of the present invention, and the explanation will be given by taking as an example a case where silicon oxide films having different thicknesses are formed on the left and right sides of a field oxide, in accordance with the conventional example shown in FIG.

In FIG. 2(1), a thick oxide film is formed on the left surface a of the field oxide 12 on the silicon substrate 11, and a thin oxide film is formed on the right surface. shall be formed.

In Fig. 2 (2), in order to suppress oxidation of the part b on the right side, nitrogen ions are implanted into this part.
In order to prevent nitrogen ion implantation into the surface of the part a of the silicon substrate, the surface of the part a of the silicon substrate is coated with a resist film 13.
Cover with

Figure 2 (3) is a diagram showing nitrogen ions being implanted into a silicon substrate, but no nitrogen has penetrated into part a, which is covered with a resist film, and nitrogen atoms are shown by dotted lines in part b. After n is implanted and the ion implantation is completed, the resist film is removed.

FIG. 2 (4) is a diagram showing an oxide film after thermally oxidizing a silicon substrate under predetermined conditions, and the surface of part b where nitrogen atoms are implanted has a rate of oxidation suppressed by nitrogen. A thin oxide film 14 is formed, and on the other hand, a thick oxide film 15 is formed in a portion a where nitrogen atoms are not ion-implanted under conditions corresponding to the temperature and time of thermal oxidation.

Usually, the voltage for ion implantation of nitrogen atoms is 50 KeV to 1
At about 50 KeV, the ion-implanted atoms can be strictly controlled, and the oxidation rate can be easily adjusted by adjusting the implantation amount.

In this way, by implanting nitrogen ions into the surface of the silicon substrate,
Multiple surfaces with different oxidation rates can be provided, the manufacturing process is simplified, and by controlling the amount of nitrogen implanted, oxide films with different thicknesses can be simultaneously formed at desired positions on the silicon substrate surface. This makes it possible to create a clean manufacturing process that does not require a wet process for processing silicon substrates, and the desired film thickness can be obtained by adjusting the amount of nitrogen implanted, which contributes to improving the quality of semiconductor devices and increasing the efficiency of the manufacturing process. Great effect.

(gl Effects of the Invention As explained in detail above, by adopting the manufacturing method of the present invention, there is a great effect in that it can improve the quality of semiconductor devices and improve the efficiency of the manufacturing process, resulting in economic efficiency. .

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining a conventional manufacturing method. FIG. 2 is a diagram explaining the manufacturing method of the present invention. In the figure, 11 is a silicon substrate, 12 is a field oxide, 13 is a resist film, 14 is a thin oxide film, and 15 is a thick oxide film. Engraving of the drawings (no change in content) Figure 1 Figure 2 Procedural amendment (Horiki July 6, 1982, 2, Relationship to the title of invention case Patent applicant address Kamiodanaka, Nakahara-ku, Yozaki City, Kanagawa Prefecture) Address 1015 (5
22) Name: Fujitsu Co., Ltd. 4, Agent Address: 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Co., Ltd. Uchisatsu 5, Date of Amendment Order: June 6, 1980 (1) Page 7 of the Specification In lines 16 and 17, “Figure 1 is...
...A diagram explaining the manufacturing method. ' shall be amended as follows. "Figure 1 (11 to Figure 1 (4)) are cross-sectional views for sequentially explaining the conventional manufacturing process. Figure 2 (11 to Figure 2 (4)
) are sectional views for sequentially explaining the manufacturing process of the present invention. (2) Correct the drawing as shown in the attached amended drawing. 9. One or more copies of the catalog correction drawings for attached documents

Claims (1)

[Claims] In order to simultaneously form oxide films with different thicknesses on the surface of a single silicon substrate, nitrogen ions are implanted into the silicon substrate surface, which is previously formed to a thin film thickness, and then the silicon substrate is oxidized to simultaneously form oxide films. A method for manufacturing a semiconductor device, comprising forming oxide films having different thicknesses.