JPS62160732A - Forming method for silicon oxynitride films - Google Patents

Abstract

PURPOSE:To make it possible to form silicon oxynitride films having good quality without ion damages at a low temperature, by projecting ultraviolet rays having a wavelength of 300nm or less in a reaction gas, and forming a film, whose thermal expansion coefficient is close to that of a silicon films, on a substrate. CONSTITUTION:On a wafer susceptor 2, a P-type (100) silicon substrate 3 is provided. The inside of a sample chamber 1 is evacuated to the vacuum state. Thereafter, SiH4 gas, N2O gas and NH3 gas are introduced. By using mercury lamp 6, ultraviolet rays (e.g., wavelength of 254nm) is projected. Silicon oxynitride films are formed on the silicon substrate 3. Then, a gas introducing port 7 is closed and the gases are exhausted. Thereafter N2 gas is introduced, and an atmospheric pressure is restored. The silicon oxide and nitride (SiOxNy) films, which are formed on the silicon substrate 3 in these processes, have the film compositions of X 1.1 and Y 0.6. The thermal expansion coefficient of the films is close to that of a silicon film.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement in the method of forming a silicon oxynitride film, which is a high dielectric insulating film, and in particular has a coefficient of thermal expansion close to that of a silicon film at low temperatures. The present invention relates to a method for forming a silicon oxynitride film having a film composition.

<Prior art> In recent years, in the formation of stacked SOI, it has become possible to reduce strain by using an interlayer insulating film whose coefficient of thermal expansion is close to that of a silicon film, and to form a defect-free recrystallized silicon film. Attention has been paid.

Silicon oxynitride film can have a coefficient of thermal expansion close to that of silicon film due to its film composition, and has excellent insulation properties.
It is seen as promising as an interlayer insulating film for a laminated structure Sol.

This silicon oxynitride film has conventionally been formed by a sputtering method or a plasma CVD method.

<Problems to be Solved by the Invention> However, the conventional method of forming a silicon oxynitride film causes charged particles such as ions and electrons during film formation to damage the base substrate and the formed film! ! r (There is a clearing point where damage resistance occurs.

The present invention was devised in view of the above points, and an object of the present invention is to provide a method for forming a silicon oxynitride film in which a high quality silicon oxynitride film is formed at a low temperature by a photochemical reaction.

<Means for Solving the Problems> The method of forming a silicon oxynitride film of the present invention involves irradiating ultraviolet light with a wavelength of 300 nm or less in a reaction gas, and forming a silicon film on a substrate with a thermal expansion coefficient of 300 nm or less through a photochemical reaction. The structure is such that a silicon oxynitride film having a film composition having a value close to the coefficient of thermal expansion is formed.

In the present invention, the reaction gas used is silane (SIH
4), nitrous oxide (N20), ammonia (NH3)
It is appropriate to use NH3/(N 20 +
The gas flow rate ratio of N Hs ) is suitably about 0.5 or less.

Further, it is appropriate that the irradiation with ultraviolet light having a wavelength of 300 nm or less be performed using a low-pressure mercury lamp.

In the present invention, as mentioned above, in particular NH3/(NH3
It is appropriate to set the gas flow ratio of +N20) to about 0.5 or less, but this is because the reaction rate of the silicon nitride film is high under conditions where the partial pressure of NH3 gas is high, and the coefficient of thermal expansion is higher than that of the silicon film. Since it is difficult to obtain a silicon oxynitride film with a film composition that is close to the value, the partial pressure of N20 is set to a high condition, that is, N
A silicon oxynitride film is formed by setting the gas flow rate ratio of H3/(NH3+N20) to 0.5 or less.

<Function> With the above configuration, a film composition having a thermal expansion coefficient close to that of a silicon film (S i OxN, : X': 1.1
°Y'::0.6), a high quality silicon oxynitride film without ion damage etc. can be formed at low temperature.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a thin film forming apparatus used to carry out the method of forming a silicon oxynitride film of the present invention. In FIG. 1, 1 is a reaction chamber (sample chamber), 2 is a wafer Susceptor, 3 is silicon wafer, 4 is IR lamp, 5
is synthetic quartz, 6 is a low-pressure mercury lamp (Hg rung), 7 is a gas inlet, 8 is gate pulp, 9 is a mechanical booster pump, and 10 is an oil rotary pump.

A fP type (100) silicon (Si
) A substrate (15 to 25 Ω/cIm) 3 is installed, and then the rotary pump 10 is activated to roughly reduce the pressure in the sample chamber 1.Then, the mechanical booster pump 9 is used to pump the inside of the sample chamber 1 to 1 f3[ Torr]. During this evacuation operation, the temperature of the substrate 3 is kept at 20°C using an IR clamp.
It was raised and held at 0 ['C]t. After evacuation to 10 [Torr] or less using the pump 9, the Si
H< gas, N20 gas, NH3 gas, for example, 15 each (SCCM).

10100 (SCC, 10100 (SCC) is introduced to maintain the pressure inside the sample chamber 1 at 2.5 (Torr), and using a mercury lamp (Hg lamp) 6, ultraviolet light (for example, wavelength 25
4 nm) to form a silicon oxynitride film with a thickness of 85 nm on the silicon substrate 3.

Next, the gas introduction lower is closed and the mechanical booster pump 9 is used to exhaust the air to below 10 (Torr), then N2 gas is introduced into the sample chamber 1 to return it to atmospheric pressure, the sample chamber 1 is opened, and the sample 3 I took it out.

Through the above process, the silicon oxynitride (S i OX Ny ) film formed on the silicon substrate 3 has a film composition of X:1.1°Y20.6, and the thermal expansion coefficient is similar to that of the silicon film. A silicon oxynitride film with a film composition having similar values was formed.

Furthermore, Figure 2 shows the refractive index and film formation rate of NHJ/(NH3+N
20) This shows the dependence on gas flow ratio.

Note that the present invention is not limited to the above embodiments,
Various modifications can be made without departing from the spirit of the invention; for example, the ultraviolet light source is not limited to a low-pressure mercury lamp, but may also be an excimer laser, and the reaction gas is not limited to SiH4 gas. For example, S
It goes without saying that 1□H6 Ganu may be used.

<Effects of the Invention> As described above, according to the present invention, a high-quality silicon oxynitride film without ion damage can be formed at a low temperature, and it can be applied to an interlayer insulating film of a stacked structure SOI. It is very effective.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of a thin film forming apparatus used to carry out the method of forming a silicon oxynitride film of the present invention;
Figure 2 shows the refractive index of the silicon oxynitride film, N H3/(N
FIG. 3 is a diagram showing dependence on gas flow rate ratio (H3+N 20 ). 1... Sample chamber, 2... Wafer susceptor, 3.
・・・Silicon wafer, 4...Low pressure mercury lamp, 7...
・Ganu inlet. Applicant Todoroki Director General of the Agency of Industrial Science and Technology Figure 1

Claims (1)

[Claims] 1. A film composition that is irradiated with ultraviolet light with a wavelength of 300 nm or less in a reactive gas and whose thermal expansion coefficient becomes close to that of a silicon film is formed on a substrate through a photochemical reaction. 1. A method for forming a silicon oxynitride film, the method comprising forming a silicon oxynitride film having the following properties. 2. The ultraviolet light is ultraviolet light from a low-pressure mercury lamp, and the reaction gas is silane (SiH_4), nitrous oxide (N_2
O), ammonia (NH_3), and the gas flow ratio of NH_3/(N_2O+NH_3) is 0.
．． 5 or less, the method for forming a silicon oxynitride film according to claim 1.