JPS60100674A - Formation of nitride film - Google Patents

Abstract

PURPOSE:To enable formation of a P3N5 film at a low temp. and to prevent deterioration of the performance of a semiconductor in the stage of forming the P3N5 film as a protective film by a chemical vapor deposition method on the surface of the semiconductor by using NF3 as a nitrogen source. CONSTITUTION:A compd. semiconductor 3 is installed in a quartz reaction tube 2 and an inert gas such as gaseous Ar is supplied into the tube 2 to expel air therefrom in the stage of forming a P3N5 film as a gate insulating film on InP of the compd. semiconductor by a chemical vapor deposition method. While the diluted PH3 is passed, the tube 2 is put into an electric furnace 1 and when the temp. of the tube 2 attains a stationary state, a gaseous mixture composed of 1% NF3 and 1% PH3 diluted with Ar is supplied by which the protective film of P3N5 is formed on the InP semiconductor 3 at a low temp. of 370-400 deg.C. Since the temp. is low, the InP compd. semiconductor is not damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a nitride film used as a gate insulating film or a protective film on the surface of a soil layer in a field effect transistor.

As an example of forming a nitride film on a conductor, a nitride (P, N,) film was deposited as a gate insulating film on InP, a compound semiconductor, by chemical vapor deposition. “M” formed by position)
In the past, a mixture of ammonia (NH3) and phosphine (PH3) was used. This reaction between ammonia and phosphine becomes usable only at temperatures above 900°C, and this is because the rate of this reaction is determined by the decomposition of ammonia, and ammonia is an extremely stable substance. By using tungsten or the like as a catalyst, the reaction rate can be increased several times at 900°C, but even when a catalyst is used, a high temperature of 900°C or higher is essential.

In this way, nitridation and oxidation, which are produced by reaction in high temperature range,
An insulating film is formed by depositing on indium phosphorus kept at 480° C. or higher. During deposition, if radiation from a high-temperature region hits the semiconductor surface directly, the film quality will deteriorate due to optical damage, and if the semiconductor substrate temperature is lower than 480°C, phosphorus will be trapped in the film and deteriorate the film quality.・It is known that as soon as the film begins to show changes over time, the rake current increases, making it impossible to use it as a gate insulating film. In order to improve the characteristics of field-effect transistors using compound semiconductors, it is desirable to deposit a high-quality gate insulating film at the lowest possible substrate temperature.

In order to solve the problems associated with the high temperature reaction during nitriding with ammonia, the present invention aims to lower the reaction temperature and reduce the deposition temperature by nitriding by chemical vapor deposition using nitrogen trifluoride (NF). The present invention provides a method for forming a nitride film that achieves lower temperatures.

The present invention will be explained in detail below with reference to the drawings.

The figure shows a specific example of an apparatus for carrying out the present invention, in which 1 is a split electric furnace, 2 is a quartz reaction tube, 3 is a semiconductor substrate, and 4.4a
5.5a is a Teflon connector, and 5.5a is a Teflon tube. A mixed gas of nitrogen trifluoride (1%) and phosphine (1%) diluted with argon is supplied to the reaction tube through tube 5. The temperature distribution of the electric furnace is set as 6 or 7.

When depositing phosphorus nitride on InP using this device, first expel the air in the reaction tube 2 with an inert gas such as argon, and then split the reaction tube 2 while flowing diluted phosphine (PH3). Open the electric furnace and put it inside. When the temperature of the reaction tube 2 reaches a steady state, diluted nitrogen trifluoride (NF'3) is allowed to flow, and the deposition of phosphorus nitride begins immediately.

If the temperature of the substrate 3 is below 500°C, a mixed gas of nitrogen trifluoride (NFS) and phosphine (PHs) may be supplied before the reaction tube 2 is placed in the electric furnace 1, or a mixed gas of nitrogen trifluoride (NFS) and phosphine (PHs) may be supplied first. After the reaction tube 2 is placed in the electric furnace 1, phosphine (PH3) may be introduced. However, if the temperature of the substrate 3 is 500° C. or higher, it is necessary to flow phosphine (PH'3) first.

Otherwise, the substrate 3 will be severely attacked by nitrogen trifluoride (NFS).

In this way, when using 1% diluted nitrogen trifluoride and phosphine in the case of temperature distribution 6, deposition up to 400°C is possible, and in the case of temperature distribution 7, the high temperature region can be increased to 450°C.
℃, deposition is possible up to the temperature of the substrate 3 of 370°C.

In the case of temperature distribution 6, if the temperature of the substrate 3 is further lowered, the deposition rate is extremely slow and a film thickness of about 100X cannot be obtained within 91 hours.

In this case, nitrogen trifluoride (NFS) and phosphine (
It is possible to increase the deposition rate by increasing the concentration of PH3), but if the concentration is increased too much, it will explode.

The lower limit of reaction temperature is significantly lowered by using nitrogen trifluoride (NF3), but this is because the bonding force between hydrogen and fluorine is extremely strong. This is because the combination of fluorine produces active nitrogen and phosphorus, which combine to form phosphorus nitride.

Therefore, this reaction produces hydrogen fluoride,
This will attack the quartz reaction tube 2. however,
In reality, a phosphorous nitride film is also attached to the tube wall of the quartz reaction tube 2, and this is not easily corroded by hydrogen fluoride, so that once the tube wall is coated with an insulating film, it can be used repeatedly.

The above is about the case of phosphorus nitride film, but phosphine (
By using an inert gas containing an organic metal such as trimethylaluminum or triethylindium instead of PH3), a film of aluminum nitride or indium nitride can be formed.

Furthermore, a silicon nitride film can be obtained by using silane.

Phosphorus nitride is also phosphorus trifluoride (F'Fa) and ammonia (N
It can also be obtained by the reaction H3). In this case as well, the strong bonds of hydrogen fluoride make it possible to lower the temperature, but phosphorus trifluoride is more reactive than nitrogen trifluoride at room temperature, so nitrogen trifluoride is more difficult to use in piping and depressurization. It has the advantage that there is less problem of valve corrosion and it is easy to handle.

As explained above, by chemical vapor deposition of a nitride film using nitrogen trifluoride as a nitriding agent according to the present invention, the deposition temperature can be lowered, and when applied to gate insulating film formation, a good interface can be achieved. It has the advantage of providing certain characteristics.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing an example of an apparatus in which the present invention is applied to nitride film formation. 1... split electric furnace, 2... quartz reaction tube, 3...
Semiconductor board, 4, 4a...Teflon connector, 5.
5a...Teflon tube. Patent applicant Tsuneo Shiramizu, agent of Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] A method for forming a nitride film, characterized in that nitrogen trifluoride is used as a nitrogen source when forming a nitride film by a chemical vapor deposition method.