JPS6329504A - Bias sputtering - Google Patents

Abstract

PURPOSE:To obtain a bias sputtering method capable of making the coating property of a film to be formed excellent without causing the decrease of film quality, by forming a bias sputtering film applying a treatment gas having specific gravity larger than argon gas. CONSTITUTION:On the upper part of a chamber 1, a gas supplying port 7 connecting to a treatmint gas source 6 is arranged. For the treatment gas source 6, the following are adopted, krypton gas, xenon gas and radon gas having specific gravity larger than argon gas, or a mixed gas of thease gases and argon gas. The treatment gas is introduced into the chamber 1, whose inside is kept a vacuum of about 1-100 Torr, and electric power is supplied to a lower electrode 3 from a negative power source 5, while an upper electrode 2 is heated by a heater 12. As the result, the surface coating of a silicon wafer W is completed by the effect of plasma generating in the vicinity of the upper electrode 2. As the gas having specified gravity larger than argon gas is used, the acceleration which moves the treatment gas toward the wafer W is decreased. Therefore, the generation of voids can be restrained and the film quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bias sputtering method, and particularly to a bias sputtering method that provides good film quality and good adhesion to patterns with large aspect ratios.

[Conventional technology]

Generally, in the manufacturing process of a semiconductor device, a metal film is deposited on a semiconductor substrate and formed into a desired pattern to form electrodes and wiring. In recent years, with the miniaturization of elements of semiconductor devices, electrodes and wiring have also been miniaturized, and this has increased the need for techniques for depositing metal films on patterns with large aspect ratios. Conventionally, a so-called bias sputtering method in which sputtering is performed while applying a negative voltage to a substrate is known as a technique for successfully depositing a metal film on such a pattern with a large aspect ratio.

That is, in this bias sputtering method, an electrode supporting a substrate on which a metal film is to be deposited is placed opposite a cathode electrode, a negative bias voltage is applied to this substrate-side electrode, and the inside of the chamber is maintained at the required gas pressure. This is a method in which sputtering is performed in a maintained state.

According to this bias sputtering method, an applied bias causes ion collisions, and the sputter etching at this time preferentially etches the sloped parts and redeposit the flat parts, resulting in highly flat film deposition. can be realized.

[Problem that the invention seeks to solve]

In this type of bias sputtering, in order to improve the adhesion of a metal film to a pattern with a large aspect ratio, it is necessary to increase the power supplied to the substrate, for example, to increase the bias voltage of the substrate. is effective, but as the bias voltage increases, argon in the chamber becomes more likely to be taken into the film. In particular, since argon gas has a low specific gravity, the amount of argon gas taken in is large.

For this reason, the introduced argon thermally expands in the subsequent heat treatment step, causing voids in the film and causing hillocks, resulting in a problem that the quality of the deposited film deteriorates.

An object of the present invention is to provide a bias sputtering method that can improve the adhesion of the formed film without causing a deterioration in film quality.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, bias sputtering film formation is performed using a processing gas having a higher specific gravity than argon gas, such as krypton gas, xenon gas, radon gas, or a mixed gas of these gases and argon gas.

[Effect]

According to the above-mentioned apparatus, since the specific gravity of the reaction processing gas is high, it is possible to suppress the gas from entering the sputter-formed film, and prevent blistering during subsequent processing, thereby ensuring good quality and adhesion. Good film formation can be achieved.

〔Example〕

FIG. 1 is a sectional view showing an example of a bias sputtering apparatus for carrying out the present invention.

Inside the chamber 1, which can be kept airtight, there is an upper electrode 2.
and a lower electrode 3 are arranged to face each other, the upper electrode 2 supports a silicon wafer W as a substrate for film formation, and the lower electrode 3 supports an aluminum target T as a film formation material. .

A negative power source 4 is connected to the upper electrode 2 to apply a predetermined bias voltage to the silicon wafer W, and a negative power source 5 is connected to the lower electrode 3 as a cathode electrode. The chamber 1 is grounded, a heater 12 is placed close to the lower electrode 2, and a permanent magnet 13 is placed on the lower electrode 3 to generate a magnetic field in the lower electrode 3.

Furthermore, an ammeter 1 is installed in the circuit of the negative power supply 4 of the upper electrode 2.
0 is inserted, and this ammeter 10 is connected to the controller 11. This controller 11 includes the ammeter 1
The configuration is such that the negative power supply 4 is controlled based on the current value from 0, and the current flowing through the silicon wafer W can be controlled.

On the other hand, in the upper part of the chamber 1, a gas supply lower communicating with the processing gas a6 is provided, and in the lower part, an exhaust port 8 is provided to reduce the pressure inside the chamber 1 to a predetermined pressure, and a pump 9 is provided. .

Here, as the processing gas source 6, Lipton gas, xenon gas, radon gas, or a mixed gas of these gases and argon gas, which has a higher specific gravity than argon gas, is used.

In the method of the present invention using this bias sputtering apparatus, first, the inside of the chamber 1 is heated at 10-'T by the exhaust port 8 and the pump 9.
After performing high vacuum evacuation to about 100 mA orr, the processing gas is introduced into the chamber 1 from the gas supply lower and the inside is heated to 1 to 100 Ton.
Set the degree of vacuum to about rr.

Next, while heating the upper mold i2 with the heater 12, power is applied to the lower electrode 3 from the negative power source 5. At the same time, upper electrode 2
Also, power is applied from the power purchase a4 to set the required bias. As a result, plasma is generated between both electrodes 2.3, and aluminum atoms are scattered from the aluminum target T on the lower electrode 3 due to the action of this plasma. These aluminum atoms are scattered toward the silicon wafer W on the upper electrode 2, and are then deposited on the surface of the silicon wafer W by the action of plasma generated near the upper electrode 2.

At this time, the current in the upper electrode 2 is measured by an ammeter lO, and the controller 11 feedback-controls the power purchase #4 based on this current value so that the current in the silicon wafer W is approximately equal to or higher than a predetermined value. Control. Thereby, the amount of ions in the gas flowing into the silicon wafer W under the plasma can be increased while the bias at the upper electrode 2 is kept constant, and the substrate current can be maintained at a predetermined value or higher. This makes it possible to form a film with good film quality and good adhesion.

In addition, since a gas having a higher specific gravity than argon gas is used as the processing gas at this time, the acceleration at which the processing gas is moved toward the silicon wafer W together with the plasma is reduced. The probability of being taken in is also reduced when argon gas is used as the processing gas. Therefore, even when the silicon wafer W is heat-treated in a post-process, voids generated due to thermal expansion of the captured gas components can be suppressed, and film quality can be improved.

According to the embodiment described above, the following effects can be obtained.

(1) Since a gas with a higher specific gravity than argon gas is used as the processing gas, the rate of gas components being incorporated into the silicon wafer during the bias sputtering reaction is reduced.
Heat treatment in the post-process can also suppress blistering caused by gas components and improve film quality.

(2) Since the current flowing through the silicon wafer is controlled, uniform film formation can be performed, and the adhesion of the metal film to a pattern with a large aspect ratio can be improved.

(3) Since the substrate current is directly measured and the negative power source is controlled based on this measured value, the substrate current can be maintained at a predetermined value and a film can be formed with stable film quality and adhesion.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, the present invention can be applied in exactly the same manner to the case where metals other than aluminum are formed by sputtering. Further, as the processing gas, gases other than those described above may be used as long as they have a higher specific gravity than argon gas.

In the above explanation, the invention made by the present inventor was mainly applied to the field of application in which it was applied, which is the formation of a thin film in a semiconductor device, but the invention is not limited to this. The present invention can be similarly applied to forming a thin film on a substrate.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In other words, when forming a film by bias sputtering, a processing gas with a higher specific gravity than argon gas, such as krypton gas, xenon gas, radon gas, or a mixed gas of these gases and argon gas, is used, so that there is no possibility of infiltration into the substrate. By suppressing the incorporation of gas components and by heat treatment in the post-process, it is possible to improve film quality by preventing the generation of voids due to expansion of gas components, and improve the adhesion of the film to patterns with large aspect ratios. .

[Brief explanation of drawings]

The figure is a sectional view showing an example of an apparatus for carrying out the method of the present invention. 1... Chamber, 2... Upper electrode (substrate side electrode),
3... Lower electrode (cathode electrode), 4... Negative power supply,
5... Negative power supply, 6... Processing gas source, 7...-Gas supply port, 8... Exhaust port, 9... Pump, lO... Ammeter, 11... Controller, 12 ...Heater, 1
3...Magnet, W...Silicon wafer (substrate), T...
··target.

Claims (1)

[Claims] 1. A method for sputtering film formation by applying a bias voltage to a substrate in a required processing gas atmosphere, characterized in that a gas having a higher specific gravity than argon gas is used as the processing gas. bias sputtering method. 2. The bias sputtering method according to claim 1, wherein the processing gas is krypton gas, xenon gas, radon gas, or a mixed gas of these gases and argon gas. 3. The bias sputtering method according to claim 1, wherein the bias sputtering is performed by detecting the substrate current and controlling the power supply connected to the substrate to control the substrate current to a predetermined value.