JP2560038B2 - Method for manufacturing semiconductor device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device by a novel insulator-semiconductor interface forming method, and more particularly to operating characteristics, particularly effective carrier mobility. High MIS (metal
-Insulator-semiconductor) type field effect transistor manufacturing method.

[Prior Art] Conventionally, in the formation of an insulator layer-semiconductor structure, since a MOS (metal-oxide-semiconductor) type semiconductor element having excellent operating characteristics can be obtained, a silicon substrate is directly thermally oxidized. Although the method of forming an insulating film is widely used,
In recent years, VLSI (very large scale integrated circuit)
Along with this, there is a demand for thinning of the insulator layer of this MOS type semiconductor element. However, as the insulating layer is made thinner, the breakdown rate of the device is deteriorated and the yield of the device is reduced. For this reason, in order to achieve this purpose with a relatively thick insulator, a MIS (metal-in) using a silicon nitride film having a higher dielectric constant than a silicon oxide film as an insulator layer is used.
A semiconductor-semiconductor type semiconductor device has been attracting attention.

As a method of forming the silicon nitride film, there is a method of heating the silicon substrate to about 1,000 ° C. and directly nitriding it with plasma of ammonia gas. However, in this case, the silicon substrate is directly thermally oxidized. Although the same good interface characteristics as in the case of the above can be obtained, it is necessary to process the silicon substrate at a high temperature for a long time in order to obtain the film thickness required as the insulator layer, and therefore, in order to promote VLSI conversion. It is an obstacle.

Other methods for forming a silicon nitride film include plasma using silane and ammonia or nitrogen as source gases,
CVD (chemical vapor depositio) using light, heat, etc.
Although there is a method n), it is possible to form a film at a low temperature in a short time by using this method, but the presence of impurities at the interface between the silicon substrate and the silicon nitride film, and the silicon caused by charged particles in the plasma. The problem is that it is difficult to obtain an insulating film having good characteristics because the interface characteristics are deteriorated due to damage on the substrate surface.

[Problems to be solved by the invention]

The present invention has been made against the background of the above-mentioned problems of the prior art, and an object of the present invention is to provide an MIS type semiconductor device having high effective mobility.

[Means for solving problems]

According to the present invention, when forming an insulator layer of a MIS type semiconductor element in which the insulator layer is a silicon nitride film,
The present invention provides a method for manufacturing a semiconductor device, which comprises treating a semiconductor surface with a plasma of ammonia gas in a state of being heated to 200 to 600 ° C., and then forming a silicon nitride film on the surface.

As a semiconductor in the method for manufacturing a semiconductor device of the present invention, a single crystal silicon semiconductor crystal-grown by various known methods such as CZ method (Czochralski method) method, FZ method (floating zone method), and epitaxial method; CVD
Amorphous silicon semiconductors and polycrystalline silicon semiconductors grown on an insulating substrate such as a glass substrate by various known methods such as a sputtering method, a plasma CVD method, a thermal CVD method, and a sputtering method.

In the formation of the silicon nitride film in the present invention, as a first step, the semiconductor surface is treated with plasma of ammonia gas.

This specific treatment is carried out by first subjecting the above-mentioned semiconductor substrate to a conventional surface cleaning treatment, setting it in a plasma generator, then evacuating the reaction chamber, and heating the semiconductor substrate to a predetermined temperature. After the degree of vacuum and the substrate temperature are reached, ammonia gas is introduced into the reaction tank, and the ammonia gas in the reaction tank is plasmatized while maintaining a predetermined reaction tank pressure and substrate temperature.

As a method for converting ammonia gas into plasma, a method of applying an alternating electric field to the ammonia gas is used.
0.01 to 10 Torr, preferably 1 to 5 Torr, processing temperature (semiconductor substrate temperature) 200 to 600 ° C., processing time 1 to 30 minutes, preferably 2 to 10 minutes, RF (radio frequency) plasma output 0.01 to 1 W / cm ² , preferably 0.1 to 0.5 W / cm ² .

In the present invention, the semiconductor surface is treated with this ammonia gas that has been turned into plasma, and preferably the semiconductor surface is treated by 2 to 3 Å
Nitrogen in the above range, then in the second step, for example, a raw material gas consisting of a silane compound and a nitrogen compound is introduced into the reaction tank, and a predetermined gas flow rate, gas pressure in the reaction tank, and substrate temperature are maintained, and ammonia gas A silicon nitride film is formed on the surface treated with plasma by the CVD method.

As a method for forming this silicon nitride film, optical CVD is used.
Method, plasma CVD method, thermal CVD method, sputtering method, etc., and as the source gas of the silicon nitride film, silane compounds such as silane, disilane, and fluorinated silane can be cited as the source gas of the silicon source material. As a source gas of nitrogen, nitrogen compounds such as nitrogen and ammonia can be cited.

At this time, the conditions for forming the silicon nitride film by the CVD method are, for example, a nitrogen compound / silane compound (molar ratio) of 20.
1/1 to 1/1, preferably 15/1 to 5/1, the gas pressure in the reaction vessel is 0.
05 to 20 Torr, preferably 0.1 to 10 Torr, processing temperature (semiconductor substrate temperature) 0 to 500 ℃, preferably 200 to 450 ℃, RF
(Radio frequency) Plasma output is 0.01 ~ 1W / c
m ² , preferably 0.02 to 0.1 W / cm ² .

By appropriately selecting these conditions, it is possible to form a silicon nitride film having an appropriate film thickness, for example, 50 to 1,000 Å.

By using the insulator-semiconductor interface thus formed, it is possible to obtain a field effect transistor having high effective mobility.

In this case, the source and drain regions are formed by doping the silicon semiconductor with phosphorus, boron, or the like by a usual diffusion method or ion implantation method.

In addition, the source electrode, the drain electrode, the gate electrode,
A metal such as aluminum or polycrystalline silicon is used.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 An n-type silicon substrate having a specific resistance of about 1 Ωcm was used for hydrogen gas flow rate.
1.5 / min, oxygen gas flow rate 2 / min, ambient temperature 1,100 ℃
Steam oxidation for 1 hour to form an oxide film of about 5,000Å.

Then, the silicon oxide film on the P ⁺ layer to be the source electrode and the drain electrode is removed by a lithography process, and BN
Boron atoms were diffused into the silicon substrate by the diffusion method to form a P ⁺ layer.

The conditions of BN diffusion are: predeposition conditions: nitrogen gas flow rate 0.5 / min, atmospheric temperature: 1,100 ° C., treatment time: 1 hour, drive-in conditions: oxygen flow rate 2 / including steam.
Min, atmosphere temperature 1100 ° C., treatment time 40 minutes, oxygen gas flow rate 2 / min, atmosphere temperature 1100 ° C., treatment time 30 minutes.

After BN diffusion, after removing the oxide film of the channel part of the field effect transistor by the lithography process, the silicon substrate was set in the plasma generator, the reaction tank was evacuated, and then ammonia gas was introduced into the reaction tank, With the flow rate of ammonia gas to 25 cc / min, the gas pressure in the reaction tank set to 0.5 Torr, and the silicon substrate temperature heated to 300 ° C., a high-frequency electric field of 13.56 MHz was applied to the ammonia gas to generate plasma ammonia gas. 3 on the surface of the silicon substrate
Processed for a minute.

Next, the flow rate of ammonia gas is 25cc / min, and the flow rate of silane gas is 5cc / min.
A silicon nitride film having a thickness of 1,000 Å was formed as a gate insulating film by a CVD method with RF plasma while maintaining the substrate temperature at 0.5 Torr and 300 ° C.

In addition, again by the lithography process, the source,
After forming the contact hole of the drain part, aluminum was vacuum-deposited and a source electrode, a gate electrode, and a drain electrode were formed by a lithography process. Finally, in order to ensure ohmic contact between the aluminum electrode and the silicon substrate, the nitrogen gas flow rate is 2 / min, the ambient temperature is 400 ° C., the processing time is 30 minutes, and the nitrogen annealing is performed.
An IS type field effect transistor was obtained.

When the static characteristics of the transistor were measured, an effective mobility of 130 cm ² / V · S was obtained with a gate electric field of 1 MV / cm.

FIG. 1 shows a sectional structural view of the MIS type field effect transistor thus obtained.

Comparative Example 1 A MIS type field effect transistor in which the surface of a silicon semiconductor is not treated with plasma of ammonia gas before forming a silicon nitride film which is a gate insulating film is manufactured, and the transistor characteristics are measured. The gate electric field is 1 MV / cm. An effective mobility of 40 cm ² / V · S was obtained.

〔The invention's effect〕

According to the method of manufacturing a semiconductor device of the present invention, it is possible to obtain a MIS type semiconductor device having high effective mobility.

[Brief description of drawings]

FIG. 1 is a sectional structural view of an MIS type field effect transistor of an embodiment of the present invention. 1; n-type silicon substrate 2; p ⁺ layer 3; silicon oxide film 4; silicon nitride film 5; aluminum electrode

Continuation of front page (56) References JP-A-61-36937 (JP, A) JP-A-62-172732 (JP, A)

Claims (1)

(57) [Claims] 1. A semiconductor substrate for forming an insulator layer of a MIS type semiconductor device, wherein the insulator layer is a silicon nitride film.
A method of manufacturing a semiconductor device, comprising: treating a semiconductor surface with a plasma of ammonia gas while being heated to 200 to 600 ° C., and then forming a silicon nitride film on the surface.