JPS593540B2 - Nitride film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for nitriding the surface of a semiconductor or metal to form a nitride film.

Conventionally, methods for nitriding the surface of a semiconductor or metal to form a nitride film include a method of directly nitriding the surface of the semiconductor or metal, and a method of depositing a nitride film of the semiconductor or metal on the surface of the semiconductor or metal. It was hot. As a method for directly nitriding the surface, ion nitriding methods have been developed for some metals, but they have not yet reached the practical stage. In addition, for direct nitriding of semiconductor surfaces, a method of heat treatment in a nitrogen atmosphere is usually considered;
Even if the heat treatment was performed at a high temperature of 10°C, almost no nitriding reaction occurred, and a regular semiconductor nitride film was not obtained. For semiconductors, a method of depositing a semiconductor nitride film on the surface has been put into practical use.
Several techniques have been developed, including the calVaporDep0-15site method), sputtering method, plasma, and deposition method. However, in the method of depositing a semiconductor nitride film on the surface, since the semiconductor is not directly nitrided, impurities are likely to accumulate at the interface 20 between the semiconductor and the semiconductor nitride film, resulting in unpaired electrons at the interface. The interfacial charge becomes abnormally large. Therefore, although a semiconductor nitride film formed by depositing on a semiconductor surface may be used as a protective film of a semiconductor device, it has not been possible to use it as the active region 25 of a semiconductor device. As mentioned above, most conventional nitride film formation methods involve depositing a nitride film on the surface of a semiconductor or metal, and since it is not possible to directly nitride the surface of a semiconductor or metal, 30% of the impurity It has unavoidable drawbacks such as deposition and increased interfacial charge. An object of the present invention is to provide a method for forming a nitride film on the surface of a semiconductor or metal by directly nitriding the semiconductor or metal.

Hereinafter, the present invention will be explained based on Examples.

FIG. 1 is a schematic diagram of an apparatus for carrying out a first embodiment of the present invention. In FIG. 1, 1 is a laser oscillator, 2 is a laser beam, and 3 is an optical lens system. 4 is a silicon substrate on which a silicon nitride film is formed, 5
1 is a plasma generation chamber, 6 is a nitrogen gas inlet, 7 is a vacuum exhaust port, 8 is a substrate holding stand, 9 is a high frequency electromagnetic field generator, and 10 is a plasma generation coil.

Using the apparatus shown in FIG. 1, a high frequency electromagnetic field is applied to a nitrogen atmosphere to generate nitrogen plasma. When the surface of the silicon substrate 4 in the nitrogen plasma is irradiated with a high-energy, high-output laser beam, for example, a laser beam 2 with an energy of several Joules/CTn2 from a ruby laser, this laser beam 2 will emit light up to about that wavelength. The energy of the laser beam 2 that penetrates into the silicon substrate 4 is absorbed by the silicon substrate 4, and the surface portion of the silicon substrate 4 instantaneously becomes a high temperature of 1200° C. to 1500° C. If the energy of the laser beam is sufficiently large, the surface portion of the silicon substrate 4 may melt instantaneously. The surface of the silicon substrate 4 heated to a high temperature of about 1200° C. to 1500° C. reacts with the nitrogen radicals excited in the plasma, and a silicon nitride film is formed on the surface of the silicon substrate 4. In direct nitriding of the surface by conventional heat treatment, the temperature of the entire silicon substrate 4 becomes high, so it has been impossible to carry out thermal nitridation at a high enough temperature to melt silicon. However, according to the laser beam irradiation of the present invention, the surface portion of the silicon substrate 4 at a depth of about the wavelength of the laser beam 2 only instantaneously becomes high temperature, and is not irradiated with the laser beam 2 of the silicon substrate 4. Other parts are not affected in any way. Furthermore, nitrogen is
Since it is excited by the plasma and becomes nitrogen radicals, the reaction rate with silicon is significantly higher than in the case of a simple nitrogen atmosphere. FIG. 2 shows a graph of the relationship between the thickness of the silicon nitride film formed on the surface of the silicon substrate 4 by irradiation with the laser beam 2 and the intensity of this laser beam.

In FIG. 2, the horizontal axis shows the laser beam intensity, and the vertical axis shows the nitride film thickness.

In curves A, b, and c, the intensity of the high-frequency electromagnetic field that excites the nitrogen plasma increases in this order. A curve c1 indicated by a broken line indicates the case where the silicon substrate is preheated as in the second embodiment described later. From FIG. 2, it can be seen that when the silicon substrate is preheated, the thickness of the silicon nitride film becomes thicker for the same laser beam intensity.

The second embodiment of the present invention is based on this knowledge. FIG. 3 is a schematic diagram of an apparatus for carrying out a second embodiment of the invention. In FIG. 3, 1 is a substrate holding stand 8.
This is a heater that heats the silicon substrate 4 from below. In this embodiment, the silicon substrate 4 is preheated in advance to a temperature of about several hundred degrees Celsius by the heating heater 11, and then the laser beam 2 is irradiated. According to this embodiment, as can be seen from FIG. 2, the silicon nitride film formation reaction is promoted by the irradiation of the laser beam 2, and the critical intensity of the laser beam 2 at which the nitride film formation reaction occurs can be reduced. FIG. 4 is a sectional view showing a silicon substrate and a light shielding mask placed thereon when implementing the third embodiment of the present invention.

In FIG. 4, reference numeral 12 denotes a light-shielding mask made of a material that shields the laser beam 2, such as metal, and formed in a predetermined pattern on the silicon substrate 4. As shown in FIG. In the embodiment shown in FIG. 4, the light-shielding mask 12 is placed on the silicon substrate 4 and the laser beam 2 is irradiated.
The portion of the surface covered by the light-shielding mask 12 is not affected by the laser beam and nitrogen plasma, and no silicon nitride film is formed thereon. Therefore, a silicon nitride film having a desired pattern can be formed only in the portions not covered by the light-shielding mask 12. FIG. 5 is a schematic diagram showing only the optical system of an apparatus for carrying out the fourth embodiment of the present invention.

In FIG. 5, reference numeral 3a denotes an optical system that causes the laser beam 2 to travel on the silicon substrate 4. As shown in FIG. In this embodiment, the optical system 3a directs the laser beam 2 to the silicon substrate 4.
A silicon nitride film having a desired pattern can be formed by scanning the surface of the silicon substrate 4 so as to draw a desired pattern and nitriding only the portion of the surface of the silicon substrate 4 scanned by the laser beam 2. In each of the above embodiments, a case has been described in which a silicon nitride film is formed on the surface of a silicon substrate, but the present invention also provides a method for forming a nitride film of a constituent material of the base on the surface of a base made of another semiconductor or other metal. It can be used to form.

As detailed above, in the nitride film forming method according to the present invention, a high-energy, high-output laser beam is irradiated on the surface of a substrate made of semiconductor or metal in nitrogen plasma, and the irradiation causes a high temperature. Since a nitride film is formed directly on the surface of the substrate by reacting the oxidized substrate surface with excited nitrogen in the plasma, impurities are not deposited on the interface between the substrate and the nitride film 1, The interfacial electric field does not become abnormally large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for a first embodiment of the present invention;
FIG. 2 is a graph showing the relationship between the thickness of the silicon nitride film produced and the intensity of the laser beam, and FIG.
FIG. 4 is a schematic diagram of the apparatus for the embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a situation in which a light shielding mask is placed on a silicon substrate in the fourth embodiment of the present invention, and FIG. 5 is a schematic diagram showing only the optical system of the apparatus for the fourth embodiment of the present invention. In the figure, 1 is a laser oscillator, 2 is a laser beam,
3 is an optical lens system, 4 is a silicon substrate, 5 is a plasma generation chamber, 6 is a gas inlet, 7 is a vacuum exhaust port, 8 is a substrate holding stand, 9 is a high frequency electromagnetic field generator, 10 is a plasma generation coil, 11 is a heater for heating the substrate, and 12 is a light shielding mask.

Claims (1)

[Claims] 1. Irradiating the surface of a semiconductor or metal substrate with a high-energy, high-output laser beam in nitrogen plasma formed by applying a high-frequency electromagnetic field to a nitrogen atmosphere,
A nitride film forming method comprising forming a nitride film of the semiconductor or the metal on the surface portion of the base by reacting the surface of the base with nitrogen in plasma. 2. The method for forming a nitride film according to claim 1, wherein the substrate is preheated and irradiated with a laser beam. 3. The method for forming a nitride film according to claim 1 or 2, wherein the nitride film is formed in a desired pattern by irradiating the substrate with a laser beam through a light-shielding mask. 4. The nitride film forming method according to claim 1 or 2, characterized in that the nitride film in the desired pattern is formed by scanning the surface of the substrate with a laser beam so as to draw a desired pattern.