JP2000269210A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of manufacturing a semiconductor device, where an oxynitride film which is high in nitrogen concentration and small in thickness is formed on a wafer by thermally decomposing N2O gas. SOLUTION: N2O gas is thermally decomposed to form an oxynitride film on a wafer in the manufacture of a semiconductor device, where a gas such as CH4, C2H5, or NH3 which reacts with O2 gas to produce reaction products, which are hardly conductive to the oxidation of the surface of a wafer is supplied together with NO2. By this setup, an oxynitride film which is high in nitrogen concentration and small in thickness can be formed on the surface of a wafer by thermally decomposing N2O.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen-containing gate oxynitride film applied to logic devices and others.

[0002]

2. Description of the Related Art In the field of semiconductor devices, silicon wafers are generally used, but trace metal impurities contained therein cause defects in semiconductor devices.
To prevent the influence of these impurities, impurity gettering has been considered. For example, it is known that it is effective to add boron to a wafer for Fe gettering.

On the other hand, a gate oxide film is sometimes provided on the surface of the wafer. When an oxide film is provided on the surface of the boron-added wafer, boron diffuses into the oxide film in a heating step in a device manufacturing process. There was a problem of doing it.

In order to solve such a problem, it has been proposed to introduce nitrogen into an oxide film. That is, the diffusion of boron is prevented by providing an oxynitride film instead of the oxide film.

In order to form such an oxynitride film on the wafer surface, N ₂ O has been conventionally used. Specifically, a wafer on which an oxynitride film is to be formed is placed in a chamber, N ₂ O gas is introduced into the chamber, and further, at a specific temperature and pressure, for example, 900 ° C.
At 00 Torr, an oxynitride film is formed on the wafer surface. In the process of forming the oxynitride film, O ₂ gas generated by thermal decomposition of N ₂ O is used as an oxidizing agent to generate O ₂
The NO gas generated by the reaction between the gas and the N ₂ O gas acts as a nitriding agent.

However, if only N ₂ O is used, it is difficult to increase the nitrogen concentration in the oxynitride film.
This is because a nitride material generated by decomposition of N ₂ O, that is, N ₂
This is because the partial pressure of O is low. For example, 900 ° C 400
About 98% of the N ₂ O gas flowing into the reaction chamber in the Torr atmosphere is decomposed, and the gas composition at that time is N ₂ O
/ O ₂ / NO / NO ₂ = 1.86% / 90.79% / 0.
54% / 6.81%. That is, 90% of the gas in the chamber is O ₂ gas, and NO gas is only about 0.5%. That is, the O ₂ gas exists in the chamber at a concentration 170 times that of the NO gas which is a nitride material,
Since the oxidation reaction is superior to the nitridation reaction, it is difficult to form a nitrogen oxide film having a high nitrogen concentration.

In order to improve such a point, attempts have been made to increase the nitrogen concentration by optimizing conditions in the chamber, but it is difficult to obtain a sufficient nitrogen concentration, and it is possible to obtain a sufficient nitrogen concentration. There is a problem that the oxynitride film becomes thick.

[0008]

SUMMARY OF THE INVENTION In a method of forming an oxynitride film on the surface of a wafer by thermal decomposition of N ₂ O gas, a method of increasing the nitrogen concentration has been desired.

[0009]

Preparation of a semiconductor device of the present invention SUMMARY OF] is an a N ₂ O gas by thermal decomposition method for producing a semiconductor device for forming an oxynitride film on the wafer, and O ₂ gas A gas that reacts to produce a product that does not contribute to the oxidation reaction of the wafer is supplied together with N ₂ O.

According to the method of the present invention, in the manufacture of a semiconductor device in which an N ₂ O gas is thermally decomposed to form an oxynitride film on a wafer, an oxynitride film having a high nitrogen concentration and a small thickness is formed. Can be done.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Any wafer that can be used in the method of the present invention can be used as long as it can form an oxide film on the surface by an oxidation reaction. Selected. Specific examples of such a wafer include silicon and others. Among these, it is preferable to use a silicon wafer to which a dopant, particularly B, is added. This is because the benefit of forming an oxynitride film having a high nitrogen concentration is great.

In the method of the present invention, the above-mentioned wafer is placed in a reaction chamber, and N ₂ O gas and a gas which reacts with O ₂ to generate a product which does not contribute to the oxidation reaction of the wafer (hereinafter referred to as a scavenger). Gas) and oxynitriding the wafer surface at a predetermined temperature and pressure.

The scavenger gas is a gas that reacts with O ₂ gas to produce a product that does not contribute to the oxidation reaction of the wafer. That is, the scavenger gas consumes the O ₂ gas in the reaction atmosphere and acts to lower the partial pressure of the O ₂ gas. Thus, the scavenger gas can be a reducing gas, or a combustible gas. Where N ₂ O
Although the gas itself reacts with the O ₂ gas, the gas itself generates the O ₂ gas by thermal decomposition and does not lower the partial pressure of the O ₂ gas. The N ₂ O gas itself is used as a scavenger gas. Needless to say, it does not work and is not included in the scavenger gas. The scavenger gas preferably does not react with components other than O ₂ , particularly NO, of N ₂ O or decomposition products generated by thermal decomposition thereof. Such scavenger gases specifically include hydrocarbons, amines, alcohols, ethers, and others. Among them, CH ₄ and C are preferred in terms of ease of handling and cost.
₂ H ₆ and NH ₃ are particularly preferred.

Although the ratio of the scavenger gas to the N ₂ O gas is arbitrary, it is generally 0.25 times or less in molar ratio.
Preferably, it is added in a ratio of 0.125 times or less. If the ratio is smaller than this, the nitrogen concentration of the oxynitride film will not be sufficiently high, and if it is too large, the formation rate of the oxynitride film may be insufficient, so care must be taken.

The conditions for forming the oxynitride film are selected so as to efficiently form the oxynitride film, but the preferable conditions are 800 to 1000 ° C./100 to 700 Torr.

The nitrogen concentration of the formed oxynitride film is measured by a secondary ion mass analyzer (Secondary Ion Mass Spectroscop).
y: hereinafter referred to as SIMS). The oxynitride film formed by only the N ₂ O gas as in the prior art had a nitrogen peak concentration of less than 3% as measured by SIMS, whereas the oxynitride film formed by the method of the present invention. In this case, the nitrogen peak concentration becomes 3 to 5%, which is a preferable concentration for suppressing the diffusion of B in the heating step in the wafer to which B is added.

As described above, in the present invention, in forming an oxynitride film, N ₂ O gas and scavenger gas are supplied to oxynitride the surface of the wafer. The methods for forming the oxynitride film can be arbitrarily combined.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in the formation of a gate oxynitride film using N ₂ O gas, the concentration of O ₂ gas which is present at a high concentration with respect to NO gas as a nitride material is reduced, and the nitridation reaction with respect to the oxidation reaction of the wafer surface is performed. Is improved to form an oxide film having a high nitrogen concentration of 5 nm or less.

When N ₂ O gas is introduced into a reaction chamber in an atmosphere of 900 ° C. and 400 Torr, it is thermally decomposed by the following reaction.

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At this time, the oxidizing material is O ₂ gas, and the nitriding material is N ₂ gas.
O gas. O ₂ gas has a gaseous concentration of 9 by the above reaction.
0.8%, NO gas is 0.54%, and the oxidizing material exists at a partial pressure 170 times that of the nitriding material, and the oxynitriding reaction proceeds in a situation where the oxidation reaction is superior to the nitriding reaction. Therefore, when forming an oxynitride film having a high nitrogen concentration, even if the partial pressure of NO gas is increased by increasing the pressure or the like, O
_The oxidation reaction by the _two gases is also accelerated, and it is difficult to increase the nitrogen concentration of the oxynitride film.

[0021] In the method of the present invention, by introducing a large amount of O ₂ gas generated by thermal decomposition of N ₂ O gas simultaneously scavenger gas into the chamber and N ₂ O gas, O
_{The two} gases react with the scavenger gas to reduce the O ₂ concentration by consuming the O ₂ gas, which is an oxidizing agent. Let it form. At this time, as an effect of the present invention, the thickness of the oxynitride film can be reduced to 5 nm or less.

The scavenging gas is NH ₃ / CH ₄ /
A gas, such as C ₂ H ₆ , which reacts with O ₂ gas to generate a product that does not contribute to the oxidation reaction on the wafer surface is added. The reaction between the scavenge gas and the O ₂ gas is, for example, as follows.

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O ₂ gas in the gas phase is consumed by the above reaction and is converted into NO _x gas or CO ₂ gas which does not contribute to the oxidation reaction on the wafer surface, and the O ₂ gas concentration is reduced. This makes it possible to relatively accelerate the nitridation reaction with respect to the oxidation reaction on the wafer surface, and to form a thin film oxynitride film of 5 nm or less having a nitrogen concentration peak of 3% or more.

[0024]

According to the method of the present invention, an oxynitride film having a high nitrogen concentration and a small film thickness is manufactured in the manufacture of a semiconductor device in which an N ₂ O gas is thermally decomposed to form an oxynitride film on a wafer. Can be formed.

Claims (5)

[Claims] We claim: 1. The N ₂ O gas is thermally decomposed to a method of manufacturing a semiconductor device for forming an oxynitride film on the wafer, O ₂
A method for manufacturing a semiconductor device, comprising supplying a gas which reacts with a gas to produce a product which does not contribute to an oxidation reaction on a wafer surface together with N ₂ O. _{2. The} gas which reacts with the O ₂ gas to produce a product which does not contribute to the oxidation reaction of the wafer is NH ₃ , CH ₄ ,
_{2. The} method for manufacturing a semiconductor device according to claim 1, wherein the method is selected from the group consisting of C ₂ and C ₂ H ₆ . 3. The formation of the oxynitride film is performed at 800 to 1000
The method is performed under the condition of C / 100 to 700 Torr.
Or a method for manufacturing a semiconductor device according to item 2. 4. The oxynitride film has a thickness of 5 nm or less.
The method for manufacturing a semiconductor according to claim 1. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the wafer is a Si wafer to which B is added.