JPH02186630A - Formation of thin film - Google Patents

Abstract

PURPOSE:To form a thin film in excellent stepped part covering ratio and high reliability by a method wherein sputter filming process is performed in the mixed gas atmosphere of inert gas and etching gas. CONSTITUTION:Mixed gas atmosphere of inert gas and etching gas e.g. argon and carbon tetrafluoride is preserved inside a filming chamber 1 at specified pressure. Next, the space between a cathode 2 and an a anode 4 is impressed with high voltage for discharge to crack argon gas into cations 6 and electrons 7 so that the carbon tetrafluoride may be changed to radical etching gas molecules 9. Dry etching process is advanced together with sputter filming process by high speed cations 6 attracted to the cathode 2 while in the sputtering process, sputter atoms 8 turned out of a target 3 are bonded onto the surface of a PSG film 11 and a stepped aluminum film 12 to form a silicon dioxide film 13. On the other hand, in the dryetching process, the surface of the silicon dioxide film 13 is etched but the stepped surface is hardly etched.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a thin film used in manufacturing a semiconductor device.

(Prior Art) In recent years, sputtering, which is excellent in reproducibility, reliability, automation, and throughput, has been widely adopted as a method for forming thin films used in the manufacture of semiconductor devices.

A conventional method for forming this type of thin film will be explained with reference to FIG.

This figure is a configuration diagram showing the principle of sputtering. The sputtering film forming apparatus has a film forming chamber 1 provided with an inert gas supply port 1a and an exhaust port 1b, and a cathode 2 disposed above a target. A semiconductor substrate 5 is attached to the anode 3 and the anode 4 disposed below, respectively, and these are arranged so as to face each other.

In order to form a thin film on the surface of the semiconductor substrate 5 using the sputtering film forming apparatus configured as described above, first, after evacuating the film forming chamber 1, argon gas is supplied from the inert gas supply port 1a. After creating an argon gas atmosphere at a constant pressure, the cathode 2
A high voltage is applied between the anode 4 and the anode 4 to cause discharge. The argon gas is decomposed into positive ions 6 and electrons 7, which are attracted to the target 3 connected to the cathode 2 and the semiconductor substrate 5 connected to the anode 4, respectively. The positive ions 6 having mass are accelerated to a high speed, collide with the target 3, and eject sputtered atoms 8. Spattered atoms 8
adheres to the surface of the semiconductor substrate 5 disposed facing each other to form a thin film.

(Problem to be Solved by the Invention) However, in the above method, since the movement of the sputtered atoms 8 is directional, the thin film formed on the pattern having the steps becomes thinner on the side surfaces of the steps. There were problems in that the step coverage was poor, the yield was low, and the reliability was low.

The present invention solves the above problems and provides a method for forming a highly reliable thin film with good step coverage.

(Means for Solving the Problems) In order to solve the above problems, the present invention performs sputtering film formation in a mixed gas atmosphere of an inert gas and an etching gas.

(Function) As described above, when a high voltage is applied in a mixed gas atmosphere of inert gas and etching gas, anisotropic dry etching is performed at the same time as directional sputtering film formation, and etching occurs on the side surfaces of the step. Therefore, there is no difference in film thickness between the surface and the step surface, and a thin film with good step coverage is formed.

(Example) An example of the present invention will be described with reference to FIGS. 1(a) and 1(b), taking a method of forming a silicon dioxide thin film as an example. FIGS. 1(a) and 1(b) are a block diagram showing the principle of the method for forming a thin film according to the present invention, and an enlarged cross-sectional view of the main parts thereof.

The film forming apparatus according to the present invention shown in FIG. 1(a) is different from the conventional example shown in FIG. This is the point that was made. Since the rest is the same as the conventional example, the same components are given the same reference numerals and their explanations will be omitted.

A method for forming a thin film according to the present invention using a film forming apparatus having such a configuration will be described.

First, in FIG. 1(a), a mixed gas atmosphere of an inert gas and an etching gas, such as argon and carbon tetrafluoride, is created inside the film forming chamber 1, and the pressure is kept constant. Next, a high voltage is applied between the cathode 2 and the anode 4 to cause discharge. This discharge causes the argon gas to become positive ions (6) and electrons (7).
The carbon tetrafluoride becomes radical etching gas molecules 9. High-speed cations 6 attracted to cathode 2
As a result, sputtered atoms 8 ejected from the target 3
adheres to the surface of the semiconductor substrate 5.

On the other hand, the radical etching gas molecules 9 anisotropically etch the thin film formed by the sputtered atoms 8 on the surface of the semiconductor substrate 5, and release atoms 10 to be etched.

FIG. 1(b) is an enlarged sectional view of the main part of the semiconductor substrate 5, in which a pattern of an aluminum film 12 is further formed on the PSG film 11 formed on the surface of the semiconductor substrate 5.

Dry etching progresses simultaneously with sputtering film formation. In sputtering, sputtered atoms 8 ejected from the target 3 adhere to the surfaces of the PSG film 1 and the stepped aluminum film 12 to form a silicon dioxide film 13. At this time, since the thin film formed by sputtering is directional, it becomes thicker on the surface and thinner on the stepped surface.

On the other hand, in dry etching, the action of the etching gas molecules 9 is anisotropic, and the surface of the silicon dioxide film 13 is etched, but the step surface is hardly etched, so that a thin film with good step coverage can be obtained. .

In this embodiment, carbon tetrafluoride was used as the etching gas, but any gas capable of chemically etching silicon dioxide, such as CHF3, may be used.

Moreover, although the formation of a silicon dioxide thin film has been taken as an example, a thin film of a sputterable material such as an aluminum alloy may also be formed. However, in this case, it goes without saying that a gas capable of chemically etching the target material is used as the etching gas.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a block diagram showing the principle of the thin film forming method according to the present invention and an enlarged cross-sectional view of its main parts;
The figure is a block diagram showing the principle of a conventional thin film forming method. 1... Film forming chamber, 1a... Inert gas supply port,
1b...Exhaust port, IC...Etching gas supply port, 2...Cathode, 3...Target, 4...
・Anode, 5... Semiconductor substrate, 6... Cation,
7...Electron, 8...Atom (sputtered atom),
9 ”・Etching gas molecule, 10... Atom to be etched, 11... PSG film, 12... Aluminum film, 1
3...Silicon dioxide film.

Claims (1)

[Claims] A method for forming a thin film, the method comprising performing sputter film formation using a sputter film forming apparatus and creating a mixed gas atmosphere of an inert gas for sputtering and an etching gas for dry etching in a film forming chamber.