JPS6199677A - Manufacture of silicon nitride - Google Patents

Abstract

PURPOSE:To form a film of Si3N4 on the surface of a material to be treated by placing said material in a vacuum vessel, introducing gaseous Si2F6 and N2 or NH3, etc. therein while heating the material to be treated and applying further electric energy thereto. CONSTITUTION:The material 2 to be treated such as a single crystal silicon substrate is placed on the lower electrode 4' of upper and lower electrodes 4, 4' in the vacuum vessel 1. The substrate is heated to 200-400 deg.C by halogen heaters 3, 3' disposed to the upper and lower parts of the vessel 1 and the gaseous N2 or NH3 is introduced therein through an inlet 10. The gaseous Si3F6 is introduced into the vessel through an inlet 11 and, in the case of using hydrazine (N2H4) 20, the hydrazine is introduced into the vessel 1 after dehumidifying and refining with a molecular sieve 21. High-frequency electric power is at the same time supplied from an electric energy supply device 5 to the electrodes 4, 4' to convert the above-mentioned reactive gases in the vacuum vessel to plasma, thus forming the film of Si3N4 on the surface of the single crystal Si substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to silicon nitride doped with fluorine by a vapor phase reaction method using heat and plasma chemical reactions (hereinafter referred to as CVD method), for example, coatings for optical fibers and semiconductor electronics. The present invention relates to a method for producing a Badgebasilan coating.

The present invention relates to a method for producing silicon nitride which is doped with a low amount of fluorine and has 5i-F bonds, and which reduces sputtering on the surface to be formed by carrying out a plasma chemical reaction with low discharge energy.

The present invention relates to a method of reacting 5ixth with ammonia or hydrazine to form a silicon nitride film at a temperature below 500°C, preferably from 100 to 400°C, for example 300'C.

Conventionally, in order to produce a silicon nitride film, silane (SiH2
) and ammonia (NH3) to react with 200-4
The film was produced at a substrate temperature of 00°C.

However, since such a silicon nitride film contains dangling bonds of silicon and silane in a gaseous state, this separation causes adjacent silicon to bond with each other, resulting in silicon clusters remaining. This results in a residual charge. Furthermore, it induces a decrease in pressure resistance. For this purpose, M.O.
It could not be used as a final coating for ultraviolet light transmission of S, IC, etc.

Furthermore, in this method, clusters and OH remain in the produced silicon oxide. For this reason, in practice, 254n is difficult to contain in the reactive gas state.
There has been a need for a method for producing a silicon nitride film that transmits ultraviolet light having a wavelength of m.

The present invention aims to produce silicon nitride for such purpose, that is, by using 5inFzn-z (n≧2) containing 5izF, which is a fluoride of silicon.

The present invention will be described below according to the drawings.

FIG. 1 shows an outline of the CVD apparatus used in the present invention.

In the drawing, a reaction vessel (vacuum vessel) (1) has an inner wall made of quartz. The substrate (2) is placed on one of the parallel plate electrodes and heated to room temperature to 60°C by halogen heaters (3) and (3') placed at the top and bottom of the reactor.
It is heated to 0°C, preferably 200 to 400°C, for example 300°C. The doping system consists of a flow meter (6) and a valve (7), and ammonia or nitrogen is supplied from (10). Hydrazine (Nil (MPl, 4°C,
BP (113.5° C.) is a liquid at room temperature, so it is filled in a bubbler (20). This hydrazine was anhydrous and further dehumidified and purified to ultra-high purity using a molecular sieve (21). Further, silicon fluoride (11) is supplied together with Si and F from a cylinder.

These reactive gases are introduced into the reaction vessel, and are further passed through the exhaust port through the pressure adjustment valve (12) and stomp valve (13).
) and was evacuated using a vacuum pump (14).

An electric energy supply device (5) for causing a plasma chemical reaction is provided, and this low frequency energy supply coil (
4), a resistance heater (3) is provided surrounding it.

Examples are shown below.

Example 1 In this example, a silicon nitride film was formed on a single crystal silicon substrate by a plasma vapor phase reaction between 5i2F& and ammonia.

The substrate temperature is 100 to 500°C, for example 350°C, and the pressure is 0.
The reactive gas was turned into plasma (plasma density: 0.1 mW/ad) by supplying air energy (50 KHz) of 0.7 torrs to the pair of electrodes (4) and (4'). By using this 5izF6, the electric energy density required for plasma could be reduced to 172 to 1/3 compared to the case of using SiF4.

Therefore, it has the characteristic that it is possible to reduce the number of flaws (Flit scratches) on the surface to be formed. The frequency of this electrical energy was a low frequency of 10 to 200 Hz.

The coating formed was extremely important to provide greater stability with thermal energy.

That is, at frequencies above 10 MHz, the formed film (50
00 Å or more thick) at a temperature of 350°C for a long time (100 Å or more).
A crank occurred when I stored it for more than 0 hours).

A counter electrode was formed on this silicon nitride to form a diode structure, and the CV characteristics were measured. As a result, the interface state density was 3XIO"cm-" or less, and when a DC electric field was applied to the silicon oxide film, hysteresis characteristics were observed for the first time at IX106V/cm, and the nitride film formed on the silicon substrate It was found that there are fewer charge trapping centers due to the presence of silicon clusters in silicon.

When this product was examined by IR (infrared absorption spectrum) with a thickness of 0.5 μm, a large absorption was observed at 100100 O', and it was found that it was a silicon nitride film. Furthermore, what is important in the method of the present invention is that when the oxygen concentration in this film was investigated by SIMS (secondary ion spectrometry), it was found that in the conventional plasma gas phase reaction between SiH and NH3, the oxygen concentration was 2 cm-3~5X1020C
Although it contained a large amount of oxygen at a concentration of II+-3, in the present invention, it is 1 to 5 XIO"am-', which is less than 1/30 of the conventional value.

Possible reasons for this are as follows. That is, SiF4 and N2
IIF is generated as a residual gas after reaction with H4.

This HP re-reacts with SiO and 5iOH present as impurities, and SiF4, which is more stable than IP (with hydrogen), is generated by 5iOz + 4HF- + 5iFn + HzO.

As a result, since water cannot react with SiF4 in such a state, it is presumed that as a result, the film is formed and at the same time has a high purification effect.

That is, in the method of the present invention, 5itFb and nitrogen/hydrogen mixed gas or nitride gas (NH3, N2114.NF
It has been found that the reaction method with 3) is extremely effective as a passivation film for ultraviolet-erasable EF ROM semiconductor devices because the film does not contain oxygen clusters and can transmit ultraviolet light.

In the present invention, in addition to plasma CVD method, 300 nm
It goes without saying that the following light energy irradiations may be carried out simultaneously.

[Brief explanation of the drawing]

FIG. 1 shows an outline of a CVD apparatus for carrying out the method of the present invention.

Claims (1)

[Claims] 1. A method for producing silicon nitride, which comprises producing silicon nitride on a surface to be formed by applying thermal energy and electrical energy to a mixed reactive gas of silicon fluoride containing Si_2F_6 and nitride gas.