JPS6136937A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a thermal nitride film in a short time at a low temperature by introducing activated nitriding-gas ions by a plasma generator and thermally nitriding the surface of a semiconductor substrate. CONSTITUTION:Ammonia gas from an ammonia-gas supply source 1 such as a liquid ammonia bomb is introduced to a plasma generator 2 installed outside reaction pipe. Ammonia gas is activated by plasma at that time, and ammonia ions are generated, and introduced into the reaction pipe 3. Ammonia ions do not disapperar on their midways, and reach to the surfaces of semiconductor substrates 6 heated by an electric furnace 7, and a thermal nitriding reaction, a reaction thereof is fast, is generated. Accordingly, thermal nitride films are formed in a short time at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing semiconductor devices, and involves introducing ammonia ions activated by a plasma generator into a reaction tube, changing the temperature to a large amount in a short time. The present invention relates to a method of manufacturing a semiconductor device by thermally nitriding a semiconductor substrate.

Conventional Structure and Problems Conventionally, the surface of a semiconductor is nitrided by heat treatment. So-called,
As a thermal nitriding method, a method in which a semiconductor substrate is heated to a high temperature in a nitriding atmosphere such as ammonia gas is often used. Thermal nitriding reaction has the disadvantage that the reaction progresses much more slowly than thermal oxidation reaction.

1100°C to 1200°C to accelerate the reaction
Requires high temperature heating.

Introducing the high temperatures required to manufacture recent highly integrated semiconductors has many disadvantages in terms of structural design of semiconductor devices.
Recently, thermal nitriding methods in plasma have been proposed. In this method, a nitriding gas such as ammonia gas is introduced under reduced pressure into a reaction tube containing a semiconductor substrate, and a high-frequency induction heating device is used to heat the cliff conductor substrate while simultaneously generating plasma of the reaction gas. This method uses ions to promote the v-nitriding reaction, making it possible to form a thermal nitride film at a lower temperature of 950° C. to 11,000° C. than in the normal thermal nitriding method. A drawback of such a plasma thermal nitriding method is that, since a high-frequency induction heating method is used, the number of semiconductor substrates that can be thermally nitrided at one time on a susceptor is extremely small compared to a normal thermal nitriding method. In order to further increase mass productivity, a large susceptor 2 reaction tube and a high-power high-frequency heating device are required, which is disadvantageous in terms of cost.

OBJECTS OF THE INVENTION The present invention proposes a method for manufacturing a semiconductor device in which a thermal nitride film is formed at a relatively low temperature in a short time with good mass productivity.

Structure of the Invention The present invention introduces nitriding gas ions such as ammonia ions activated by a plasma generator connected to the inlet of the reaction tube into a semiconductor substrate heated in a reaction tube under reduced pressure, thereby heating the surface of the semiconductor substrate. It nitrides, and it is possible to form a thermal nitride film at a lower temperature and in a shorter time than a normal thermal nitriding method that introduces ammonia gas or the like.

DESCRIPTION OF EMBODIMENTS The present invention will now be explained in detail by way of embodiments with reference to the drawings.

The drawing schematically shows a reaction apparatus used for thermal nitridation according to an embodiment of the present invention. In the illustrated device 1
2 is an ammonia generation source (cylinder), and 2 is a plasma generator. The reaction tube 3 is formed of a thin cylindrical quartz tube or the like, and one end of the reaction tube 3 is used as an inlet/outlet for the semiconductor wafer through a cap 4 or the like, and at the same time, the other end is used as an inlet for the reaction gas. Used as a gas outlet. In addition.

5 is a quartz port, 6 is a semiconductor wafer, and 17 is an electric furnace.
8 is a vacuum pump. Further, the reaction tube 3 is pipe-connected to a plasma generator 2 using high-frequency power, and this plasma generator 2 supplies diluted ammonia gas through an opening/closing valve 9.

It is connected to the ammonia pump 1 by piping. It also has an on-off valve 10 and a branch pipe 11 for introducing nitrogen gas into the plasma generator 2 and the reaction tube 3. Reaction tube 3
A large number of semiconductor substrates 6 are loaded into the quartz port 6 installed inside the quartz port 6 in order to form a thermal nitride film, and the reaction tube 3 is loaded inside an electric furnace 7 for thermal nitriding at high temperature. has been done. The other end of the reaction tube 3 is connected to a vacuum pump 8.

Next, specific examples will be described.

To 5-7 In the illustrated apparatus, ammonia gas from an ammonia gas supply source 1 such as a liquid ammonia cylinder is introduced into a plasma generator 2 provided outside the reaction tube, where it is activated by plasma to generate ammonia ions. 5 and introduced into reaction tube 3. This is because the atmosphere inside the plasma generator 2 and the reaction tube 3 is evacuated and depressurized by the vacuum pump 8 and is in a vacuum state.

The ammonia ions activated by the plasma do not disappear on the way to the reaction tube 3, but reach the surface of the semiconductor wafer 6 heated by the electric furnace and undergo a nitriding reaction using normal ammonia gas. Produces a fast thermal nitriding reaction.

Furthermore, an example in which the present invention is applied to the formation of a gate insulating film in manufacturing an MO3 field effect transistor using a silicon wafer will be explained. A silicon wafer 〇 on which a thermal nitride film is to be formed is placed on the quartz port 6 in the reaction tube 3. At this time, a branch pipe 11 is connected to the inside of the reaction tube 3.
An inert gas such as nitrogen gas is introduced and the inside of the reaction tube 5 is filled with the inert gas. - Also, the inside of the reaction tube is set at a suitable nitriding temperature by the electric furnace 7, for example, 1000'C to 1000'C.
The temperature is set to 00℃. Next, the on-off valve 1° is closed to stop the nitrogen gas, and the system consisting of the plasma generator 2 and the reaction tube 3 is evacuated using the vacuum pump 8. Vacuum degree is 10m
When the temperature reaches approximately Torr (milli-Torr/I/), the on-off valve 9 is opened and ammonia gas is introduced into the plasma generator 2 to generate plasma. The plasma generator is
An output capacity comparable to that used in ordinary plasma etching is sufficient. The gas flow rate is determined by the evacuation capacity of the vacuum pump, and is usually several thousand to several degrees QCC per minute. When thermal nitriding is performed by introducing ammonia ions under reduced pressure, if the temperature is the same as for normal thermal nitriding, a large amount of generated ammonia ions can be used, which accelerates the nitriding reaction and reduces the time required to form a nitride film. can be reduced to about half or less compared to conventional thermal nitriding methods. Furthermore, by using the method of the present invention, it is possible to perform nitriding at a lower temperature than conventional methods, and by adjusting the flow rate of ammonia ions, the degree of vacuum in the output 2 reaction tube of the plasma generator, etc. 1100°
A thermal nitride film with good uniformity can be obtained with good mass productivity using C.

Effects of the Invention According to the present invention, when thermal nitriding is carried out by introducing ammonia ions under reduced pressure (1) If it is carried out at the same temperature as in a normal thermal nitriding method, a large amount of generated ammonia ions can be used, so that the nitriding reaction is accelerated, and the time required to form a nitride film can be reduced to about half the time of conventional thermal nitride film formation methods. Furthermore, according to the method of the present invention, it is also possible to perform nitriding at a lower temperature than in conventional methods.

The present invention has been explained above using as an example the thermal nitridation of a silicon substrate using ammonia ions, but it is also possible to form a thermal nitride film using a substrate made of other materials at the same time, and the effect of promoting the thermal nitridation reaction can be obtained. Needless to say, it will happen.

[Brief explanation of the drawing]

The drawings are schematic diagrams for realizing the method of manufacturing a semiconductor device of the present invention. 1... Ammonia gas generation source (ponbe), 2...
...Plasma generator, 3...Reaction tube, 4.
... Cap, 5 ... Boat, 6 ...
...Semiconductor substrate, 7...Electric furnace, 8...
・Vacuum pump, 9.10...Opening/closing valve, 11
・・・・・・Branch piping.

Claims (1)

[Claims] While placing the semiconductor substrate in a reduced pressure reaction tube,
A method for manufacturing a semiconductor device, comprising introducing ammonia ions activated by a plasma generator into the reaction tube and heat-treating the semiconductor substrate to form a nitride film on the semiconductor substrate.