JPS5961124A - Method for formation of thin film - Google Patents

Abstract

PURPOSE:To enable to obtain the flat surface on a substrate by a method wherein the substrate is arranged in a mixed gas atmosphere, a thin film growth reaction and an etching reaction are performed simultaneously by irradiating a beam of light, thereby enabling to lessen the unevenness of the substrate surface. CONSTITUTION:As a gas system 8, mixed gas of monosilane, oxygen and carbon tetrafluoride is used, and a substrate 3 is maintained at the temperature of 400 deg.C. Under this condition, when the above-mentioned mixed gas is introduced into a reaction chamber 1, a silicon dioxide film is grown on the substrate 3 by the reaction of SiH4+2O2 SiO2+2H2O. As the silicon dioxide film 11 has a stepping caused by a film 10, it is to be exactly formed along the stepping or in such a manner that it makes the so-called overhang. However, the CF4 contained in the mixed gas is turned to an exited state by irradiating a beam of light 9 while it is being formed, an etching is performed when the CF4 comes in contact with the silicon dioxide film and, at the same time, a silicon dioxide film 12 is formed. As the etching for the silicon dioxide film 12 is performed in the direction vertical to the substrate 3, the degree of reduction in film thickness at the stepped part is lessened, thereby enabling to reduce the stepping considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a thin film forming method that is preferably applied when it is desired to maintain the flatness of a substrate surface even after forming a thin film.

Prior Art and Problems Generally, when manufacturing semiconductor devices, forming thin films is an extremely important technique.

The thin film includes metal, insulating film, semiconductor film, etc.
They have been fabricated using various techniques, such as vacuum evaporation, sputtering, vapor deposition, and the like.

However, in semiconductor integrated circuit devices, as the density of elements increases, the surface of the device becomes more uneven, making it difficult to form a desired precise pattern on it, and causing discontinuities in the thin film. I'm doing it.

To solve this problem, a technique was developed to uniformly apply a silicon-containing liquid to the substrate surface using a spin coating method to flatten it, but when an inorganic material like the above liquid is used, , it is difficult to form a clean thin film. Also,
A thin film grown by the vapor phase growth method is partially removed by etching with a directional etching solution, and by repeating this operation, the unevenness of the surface is reduced and flattened. However, it is complicated to operate and is not practical. Furthermore, it is known that in the process of forming a thin film using the spuck method, it is possible to achieve a certain degree of flatness by utilizing the physical etching effect caused by ion bombardment, but this method requires special conditions for operation. It is difficult to implement it because it requires the following.

OBJECTS OF THE INVENTION The present invention provides a thin film forming method that can reduce unevenness on a substrate surface and obtain a flat surface condition, and is suitable for use in manufacturing semiconductor devices.

Structure of the Invention In the present invention, a scum system that grows a thin film by a gas phase reaction,
The substrate is placed in a mixed gas atmosphere with a gas system capable of etching the thin film being grown, and light is irradiated to cause the film growth reaction and the etching reaction to proceed simultaneously.

Thin film growth progresses with the supply of thermal energy, so it essentially grows along the irregularities of the substrate, but the etching action is directional due to the straightness of the light. Therefore, due to the combination of these factors, the amount of film growth is greater than the amount of etching of the valley bone film at the uneven step portion of the substrate, and as a result, the step is eliminated. A film will remain in this form.

Incidentally, as a directional etching method, there are conventional methods such as reactive, ion, etching, and notching.
(To r r) or less, and it is difficult to grow a thin film under this condition, so it is not practical.

In the present invention, since there is basically no dependence on atmospheric pressure, conditions can be set that allow the thin film to grow at a sufficiently high rate.

Embodiment of the Invention FIG. 1 represents an embodiment of an apparatus for carrying out the invention.

In the figure, 1 is a reaction chamber, 2 is a substrate support, 3 is a substrate,
4 is a heater for heating the substrate 3 to a constant temperature, 5 is a light transmission window, 6 is a gas inlet pipe, 7 is a gas discharge pipe, 8 is a gas system,
9 each represents a light.

Next, the case of growing a silicon dioxide film using this apparatus will be described.

To grow a silicon dioxide film, the gas system 8 must be monosilane (SiH+), oxygen (Q2), carbon tetrafluoride (
A mixed gas of CF4) is used.

It is necessary to maintain the substrate 3 at a temperature of 400 ("C).

In this state, when the mixed gas is introduced into the reaction chamber 1, S i H4+ 202→S i O2+ 2 H20
Due to the reaction, silicon dioxide (Si0
2) The film grows.

This will be explained in detail with reference to FIGS. 2 and 3.

FIG. 2 shows the case where a silicon dioxide film is simply grown as described above, and it is assumed that a film 10 is formed on the substrate 3, and a silicon dioxide film 11 is formed thereon.

In this case, since there is a step caused by the film 10, the silicon dioxide 1ull is formed either faithfully along this step or so-called overhanging the step.

However, as seen in FIG. 1, by irradiating the light 9 during growth, CF4 in the mixed gas becomes excited, and when it comes into contact with the silicon dioxide film, it will be etched. Furthermore, the energy of this light is CF,
It is desirable that the value is sufficient to dissociate the C--F bond. In this example, the wavelength 20
CF4 is excited using light of 00 to 2400 C.

FIG. 3 shows the state in which the silicon dioxide film 12 is grown by irradiating light.

Since the etching and notching of the silicon dioxide film 12 is carried out in a direction perpendicular to the groups Fj, 3, the decrease in film thickness at the step portion is reduced, and the step is considerably relaxed.

Effects of the Invention According to the present invention, a gas system for forming a thin film by a gas phase reaction in a reaction chamber in which a substrate is placed, and etching the thin film in a thin film forming process in manufacturing a semiconductor device are provided. By introducing a mixed gas capable of irradiating the substrate with light and performing both the thin film growth reaction and the etching reaction simultaneously, it is possible to form a thin film with few steps. It is effective in manufacturing highly integrated semiconductor devices because it becomes flat, allows easy formation of precise patterns, and does not cause wiring to be cut.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of the main parts of an embodiment of a device for carrying out the present invention, and FIGS. 2 and 3 are main parts of a semiconductor device at key points in the process for explaining an embodiment of the present invention. FIG. In the figure, 1 is a reaction chamber, 2 is a substrate support, 3 is a substrate,
4 is a heater for heating the substrate 3 to a constant temperature, 5 is a light transmission window, 6 is a gas inlet pipe, 7 is a gas discharge pipe, 8 is a gas system,
9 is light. Patent applicant: Fujitsu Ltd. Representative patent attorney: Tools: Kugobe

Claims (1)

[Claims] A mixed gas of a gas that forms a thin film through a gas phase reaction and a gas that can etch the thin film is introduced into the reaction chamber in which the substrate is placed, and a thin film growth reaction is performed while the substrate is irradiated with light. A method for forming a thin film characterized by performing both an etching reaction and an etching reaction at the same time.