JPS61113771A - Manufacture of aluminum nitride - Google Patents

Abstract

PURPOSE:To manufacture aluminum nitride enlarged with an optical energy band width by executing the photochemical reaction of an organic aluminum and a gaseous nitride. CONSTITUTION:A substrate 2 is placed on a holder 22 in a vacuum vessel 1, so that it is heated by a halogen heater 3 from the lower side. On the upper side of the substrate 2, 10 pieces of generating lamps 4 of <=300nm wavelength, which are connected to an electric power source 5 are provided so as to be opposed to the substrate 2. The vacuum vessel 1 is brought to exhaust through an exhaust port 8 by operating a pump 14. Subsequently, methyl aluminum or ethyl aluminum, and a mixed gas with ammonia, hydrazine, or nitrogen fluoride are led into the vacuum vessel 1 through a flow meter 26 from a bubbler 20, and through a valve 7 and a quantity regulating meter 6, respectively. Thereafter, when an optical energy is applied from a light emitting lamp 4, aluminum nitride is manufactured on the substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing aluminum nitride, for example, a passivation film or a gate insulating film for semiconductor electronics, by a vapor phase reaction method using thermal and photochemical reactions (hereinafter referred to as CVD method). Regarding the method.

This invention uses conventionally known SiH4 and N by carrying out a photochemical reaction between organic aluminum and nitride gas.
The optical energy band width is larger than that of silicon nitride made by US (silicon nitride is about 5.0 eV), about 7 eV.
The present invention relates to a method for producing aluminum nitride containing V.

This invention relates to organic compounds of aluminum such as trimethylaluminum ((CH:l) 3A1) or triethylaluminum ((C2)1s)3Al).
By adding ammonia (NH:l), hydrazine (NJ4), and fluorine nitride (NF 100～
It relates to a method of forming at 500°C, for example 300°C.

Conventionally, in order to produce an aluminum nitride film, aluminum chloride (AICh) and ammonia (NH3) were reacted by a plasma vapor phase reaction method using a glow discharge method, and the substrate temperature was raised to 200 to 400°C. The coating was prepared using

However, in such an aluminum nitride film, dangling bonds of metal aluminum and clusters of silicon remain in the film, resulting in variations in electrical insulation and a decrease in breakdown voltage. Furthermore, residual chlorine causes corrosion when used as a final coating for MOS, IC, etc.

In addition, because of the clusters of metallic aluminum, the transparency of ultraviolet light was insufficient. Therefore, there has been a demand for an AIN that has an Eg of about 7 eV and has excellent ultraviolet light transmittance. For this purpose, conventionally known silicon nitride has an Eg of only about 5 eV L, which is not sufficient due to residual silicon clusters. Due to these reasons, the final coating in the semiconductor manufacturing process was insufficient as a material.

1. For this reason, there has been a need for a method for producing an aluminum nitride film using an aluminide gas in which aluminum clusters are difficult to form in practice.

For this purpose, the present invention specifically uses organic aluminum (CH3) 3 (referred to as TMA).
and ammonia (NH3), especially 30
The purpose is to produce aluminum nitride by using a photovapor phase reaction method in which ultraviolet light with a wavelength of 0 nm or less is irradiated.

The main reaction formula is ^1 (CI!+) 3 + NHI→ AIN +
It is 4CH4.゛This TMA was manufactured by Toyo Stoffer Co., Ltd. Its basic physical properties are as follows.

Molecular weight 72.09 Purity 99.9998χ (as At) Density
0.752g/ml (20℃) Melting point 15.
3℃ Vapor pressure Temperature ("C) Vapor pressure (mmHg) 20
9, 2 127 760' The present invention will be described below according to the drawings.

Figure 1 shows the optical CVO or thermal CVO used in the present invention.
An overview of the device is shown.

In the drawing, the reaction vessel or vacuum vessel (1) is made of quartz. The substrate (2) is placed on a holder (22) that is heated from below with a halogen heater (3), and is kept at a temperature between room temperature and
It is heated to 900°C, preferably 200 to 500°C, for example 350°C. The doping system is a flowmeter (6), (
26) and a valve (7), and ammonia and nitrogen are supplied from (9) and (10), respectively. Furthermore, since this nitride gas remains a gas even after a decomposition reaction, it is blown into the inside of the reaction chamber window from a nozzle, and the gas, which has been photoexcited by ultraviolet light irradiation, is applied to the lower substrate surface (16
). In addition, it also had the effect of preventing TMA or its reactants, which become solid when a decomposition reaction occurs, from reaching the surface of the quartz window.

Also, TMA(Al(CH:+)+(MP 15.3℃)
) is a liquid at room temperature, so it is filled in the bubbler (20). Nitrogen was bubbled into this TMA from (11). The bubbler (20) heated the reaction chamber (1), including the flow meter (26), to 100°C to prevent adsorption of TMA to the inner wall of the pipe. Furthermore, this rule^ was sprayed from the nozzle onto the substrate side as shown in (17). In this manner, TMA and ammonia were mixed for the first time in the reaction chamber and were photoexcited to cause a reaction. In addition, reactive gases were prevented from adhering to the quartz window.

Furthermore, the pressure adjustment valve (12) and the stop valve (13) were passed through the exhaust port (8), and the mixture was evacuated using the vacuum pump (14). In order to cause a photochemical reaction, a generating lamp with a wavelength of 300 nm or less (low-pressure mercury lamp, manufactured by Ushio Inc.,
Ten ULI-45EL2-N-1) (4) and the associated power supply system (5) were used. Furthermore, this lamp chamber (28) was connected to an exhaust system and evacuated. In order to prevent the reactive gas from flowing back into the lamp chamber, a small amount of nitrogen gas was introduced from (24), and the lamp was heated to 600° C. with a heater (25) to decompose it. Furthermore, the lamp chamber (28) is the reaction chamber (1).
The pressure was adjusted using the valve (27) so as not to damage the quartz glass (26) of the window. In addition, in this way it was possible to prevent absorption loss of short wavelength light of 184 nm due to water vapor in the atmosphere before it reached the reaction chamber from the source. Furthermore, a halogen heater (3) for heating the substrate (2) and holder (22) is provided below the reaction space (1).

Examples are shown below.

Example 1 In this example, AIN was prepared in a quartz tube by a photochemical reaction between TMA and ammonia.

In FIG. 1, a silicon substrate (2) for final coating on which a semiconductor IC for forming an AIN film is formed by heating the substrate to 500°C or less with a heater (3) is placed in a holder (22) above the heater. It is placed above. Furthermore, the valve (7) was opened to introduce ammonia. Furthermore, TMA was introduced as TMA/NH3=115. The internal pressure of the reaction volume r was set in a range of 0.1 to 100 torr, for example, 10 torr. Then, there is 1 AIN in the reaction tube.
Photo CV by irradiation with 184 nm and 254 nm ultraviolet light.

By using mercury sensitization in the method, it was possible to obtain a growth rate of 2.1 people/second. This film growth rate is 3t
orr, it decreased to 1.4 people/second.

This reaction product is assumed to have a thickness of 0.2 μm. (infrared absorption spectrum), it was found to be 900 cm −
A broad and large absorption was observed in ', which revealed that it was an AIN film. Furthermore, what is important in the method of the present invention is that both TMA and ammonia are
Since it is excited by light of 00 nm or less, there is no need to use mercury. Furthermore, since the thermal conductivity of AIN is about five times better than that of silicon nitride, it is possible to prevent local heating within the IC chip. Furthermore, since its optical energy hand width is i7eV (177 nm), it can transmit ultraviolet light (184 nm and 254 nm). Therefore, even if AIN adheres to the window, it does not become a so-called barrier that prevents ultraviolet light from reaching the reactive gas.

In addition, since AIN is a nitride, it can also be expected to have a barrier effect against alkali ions such as sodium.
It was ideal as a final coating material for semiconductor devices such as.

Example 2 In this example, an aluminum nitride film was formed on a single crystal silicon substrate by a thermal reaction between TMA and ammonia. The same apparatus as in Example 1 was used. Substrate temperature is 600-90
0℃ e.g. 800℃, pressure 'l torr, TM^/N
lh #1/8.

A counter electrode was formed on this AIN (thickness: 1000 mm), and the C-■ characteristics were measured as a diode structure. As a result, an interface state density of 4×10"cm-" was obtained. In addition, the breakdown voltage when a DC electric field is applied to the AIN film is
It had more than 3 x 10"V/cm.

That is, an AIN film formed at a temperature of 500° C. or lower is effective as a pad haze film for semiconductors.

For this purpose, it is effective to utilize the physical property of the organic aluminum used in the method of the present invention, which is sensitive to ultraviolet light. In addition, since it is formed at a high temperature of 500 to 900°C and forms a dense film, AIN or AI can be used as a gate and gate electrode insulator.
It is effective to use it as a two-layer film of N 2 and SiO□. Furthermore, insulating film (dielectric film) for RAM capacitors
It is also effective as

In the present invention, when using organic aluminum,
There is a concern that carbon may be mixed into the film due to the presence of methyl groups. However, in SIMS (secondary ion mass spectrometry), it is only 1χ (and it is thought that there is no deterioration of physical properties due to this.Also, alumina may be formed at the same time due to the mixing of oxygen.However, in AIN whose amount is less than 10% by weight, the heat The conductivity obtained was as high as that of AIN with a purity of 99% or more.

In the present invention, TE^ and NH,, TMA are prepared by thermal CVD method.
It is effective to use the reaction between and NzHa. Also, 3
It goes without saying that an excimer laser (wavelength: 500 to 100 nm) may be used as the optical CVD method using irradiation with light energy of 00 nm or less.

In the present invention, it is also possible to simultaneously mix mercury for excitation of a photochemical reaction and use a mercury excitation method.

However, methods using mercury bubblers tend to leave mercury in the exhaust gas, which tends to cause pollution problems.

As the nitride gas in the present invention, non-oxygenated nitrogen fluoride (NF3.NzFa) or other non-oxidized hydrazine salts may be used.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. By applying thermal energy or thermal energy and light energy with a wavelength of 300 nm or less to a reactive gas mixture of a reactive gas containing organic aluminum and a nitride gas, the surface to be formed is formed. A method for producing aluminum nitride, characterized by producing aluminum nitride. 2. In claim 1, the gas mixture of methylaluminum or ethylaluminum and ammonia, hydrazine or nitrogen fluoride is heated by adding thermal energy or thermal energy and light energy with a wavelength of 300 nm or less. A method for producing silicon nitride, characterized by producing aluminum nitride on a forming surface.