JPS63176465A - Formation of film by reactive sputtering - Google Patents

Abstract

PURPOSE:To surely attain reproducibility on film thickness and compsn. by isolating a substrate from a sputtering region, forming a film by presputtering with only an inert gas, exposing the substrate to the sputtering region after the rate of film formation is stabilized, and introducing the inert gas and a reactive gas in a required ratio in flow rate. CONSTITUTION:A substrate 10 is isolated from a sputtering region with a shutter 11, an inert gas is introduced from a feed hole 14 and electric discharge is caused to remove an oxide film from the surface of a target 8 by presputtering. After the rate of film formation on a film thickness sensor 12 is stabilized, the shutter 11 is opened to expose the substrate 10 to the sputtering region. The inert gas and a reactive gas are separately introduced from the feed hole 14 and a feed hole 13 in a required ratio in flow rate, and electric discharge is caused to form a film of a compd. consisting of the substance of the target 8 and the reactive gas on the substrate 10. Thus, the film having a required compsn. can be efficiently formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a reactive sputtering film formation process that requires a precise composition, such as an optical protective film.

(Prior Art) A conventional sputtering method will be explained using a reactive sputtering apparatus shown in FIG.

Squeeze contactance valve 1, pulp 2.3 [t,
fii controller (generally called mass flow controller)
4.5, flow reactive gases such as oxygen and nitrogen and inert gases such as argon at set flow rates, and vacuum chamber 6.
The pressure inside is set to about 10-'' torr. The vacuum chamber 6 and the substrate holder 9 are grounded and have a ground potential. The high frequency 1! source 7 is turned ONL, and discharge is started between the target 8 and the substrate holder 90. The discharge current is composed of positive ions and electrons.Due to the difference in mobility between positive ions and electrons, the target 8, which is an electrode, has a negative bias potential. The ions are accelerated by the electric field and collide with the target 8. Atoms or molecules in the target B are ejected (that is, sputtered) and reach the 01 substrate 10.The sputtered atoms or molecules are transferred to the substrate 1G.
Sputtering is continued for a certain period of time with the shutter closed, and a thin film of the reaction product consisting of the target 8 substances and the reactive gas with a set composition is obtained on the substrate. (for about a few minutes). (This is referred to as press-no-kututtering.) Thereafter, the shutter is opened and a film is formed on the substrate. If a considerable amount of film thickness is obtained by the film thickness sensor 12,
Close the shutter, turn off the high frequency power source 7, and end the reactive sputtering 0 (problem to be solved by the invention) Both inert gas and reactive gas are flowed simultaneously to perform pre-sputtering and film formation. In the conventional method, for example, Ar is used as the target 8 as 5lt-1 inert gas.
'c, when forming a film with a required composition of 5tyx using 0□ as a reactive gas, the following problem occurred.

That is, even if Ar and 0□ are set at the same flow rate in the flow rate controller 4.5 in the same reactor and sputtering film formation is performed for a certain period of time at the same operating pressure, the required amount of SiOx on the substrate lO Reproducibility of film thickness and composition X cannot be obtained.

The present invention aims to reliably achieve the reproducibility of these film thicknesses and compositions. Pre-sputtering is performed by introducing an inert gas and discharging the space between the board and the substrate in a state of interruption, and a film thickness sensor detects that the film formation rate of the pre-sputtering has reached a stable state, and the above-mentioned interruption state is established. The method is characterized in that a compound of the target material and the reactive gas is formed on the substrate by introducing an inert gas and a reactive gas at a required flow rate ratio and discharging the discharge gas.

As the film thickness sensor, a normal one such as a crystal vibration type can be used.

The film deposition rate is the amount of increase in film thickness per hour, and is conveniently displayed by connecting a suitable process detector to the film thickness sensor. After starting Presunokututtering,
The film formation rate increases and eventually saturates and reaches a constant value. For example, if the film formation rate does not change for 10 seconds, it is determined that stability has been reached.In reality, instead of directly detecting that the film formation speed of press sputtering has reached stability,
Measure the time from the start of discharge until the film formation rate reaches stability in advance, and then introduce the reactive gas after the above-mentioned time has elapsed after starting the discharge of the press-pack ring. When performing sputtering by introducing a reactive gas, the reactive gas is actually introduced while maintaining the above-mentioned cutoff state, and the initially unstable film formation rate is cut off after it reaches a stable state. It is preferable to release the state and form the compound into a film.

The composition ratio of the compound formed into a film can be changed by changing the flow rate ratio of the inert gas and the reactive gas. The composition ratio can be confirmed by the known fluorescent X edge method.

To obtain the desired composition, in advance, according to the method of the present invention, a reactive gas is flowed at several flow rates at a constant sputtering power and inert gas pressure, and the composition of the film formed on the substrate IO is determined. Measure and obtain a correlation curve between reactive gas flow rate and composition,
Then, a reactive gas flow rate corresponding to the target composition is determined, and reactive sputtering film formation is performed at that reactive gas flow rate.

(Function) Next, the function of the present invention will be explained with reference to FIG. When pre-sputtering is performed using only an inert gas, the oxide film on the surface of the target 8 is sputtered and removed. As the oxide film is removed, the film formation rate on the film thickness sensor 12 increases, and when the oxide film is completely removed, the film formation rate matches the film formation rate of the target material, and then remains at a constant value. Stabilize. This state is point a. In other words, it is detected that the oxide film on the surface of the target 8 has been completely removed and the pure target material has been exposed. Then the reactive gas 0
By introducing □ by the set value (corresponding to point C), the state of 0 point can be obtained according to the operating line. Then, the shutter 11 is opened to release the cut-off state, and the 0 point is 0. After adjusting the flow rate, a film of a reaction compound having the following composition is formed on the substrate 1O.

According to the method of the present invention, since the method always passes through point a,
Reactive sputtering is performed using the b-c-d-e-f operating line, which solves the problem of non-reproducibility due to the target 8 surface condition in the conventional method, and ensures reactive sputtering at zero point. Film formation can be carried out, and a stable composition and film formation rate corresponding to that state can be obtained.

In addition, on the a-b-c-d operating line, the composition X of 510X on the substrate IO can be obtained in the range of 0 to 2.0.

On the other hand, on the operating line of fm@#C'~t, Sl 0. Example 0.1 - A case will be described in which reactive sputtering of Si is performed using Ark as a reactive gas and an inert gas. Pulp 213, flow rate regulators 4 and 5, and supply port 13.1 are supplied from outside supply sources for 01 and ArFi, respectively.
Supply port 1 for zero-reactive gas introduced into the vacuum chamber 6 via 4
3 is preferably directed toward the substrate IO, and the inert gas supply port 14 is preferably directed toward the target 8. Target 8 is S
t and uses a magnetron system. The inside of the vacuum chamber 6 is sufficiently evacuated, and preferably the pressure is reduced to I x 10-
@torr or less, the conductance pulp 1 at the exhaust port 15 is squeezed, and the inert gas pulp 3 is opened to flow Ar into the vacuum chamber 6.

The pressure control is performed by a flow rate regulator 5.

Pre-sputtering is performed by applying a high frequency to the high frequency power source 7 and the target 8. At this time, the power supply power was set in the range of 1 to 2 drops when the target 8 was Si.

In the above process, the film thickness sensor 12 detects the film forming rate t-
The detected value gradually increases and eventually stabilizes at a constant value. The time it took to reach a certain value was approximately 1 to 5 minutes. After the film formation rate of the film thickness sensor 12 stabilizes at a constant value, the reactive gas pulp 2
, and from the gas supply port 13 0. flows into the vacuum chamber 6. Adjust the flow rate regulator 4 to reach the set value C point in Figure 2.
fK'! : It will increase.

0. After the flow rate stabilizes, open the shutter 11 and remove the substrate lO.
A reaction product thin film is formed on top.

Although it varies depending on the device, for example, the sputtering pressure is 5 x 1
If the flow rate of 02 is 7 cr for 7 minutes at O-3 torr,
A thin film having a composition of 810□, 4 was obtained with good reproducibility.

(Effects of the Invention) As described above, the present invention can reliably, stably and efficiently form a target material having a desired composition onto a substrate.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the general configuration of a conventional reactive sputtering device, and Figure 2 explains the effects of the present invention.Next, it shows the relationship between the flow rate of reactive gas and the film formation rate of the film thickness sensor Graph showing Ol... conductance pulp, 2
... Pulp, 3... Pulp, 4... Flow rate regulator,
5...Flow rate regulator, 6...Vacuum chamber, 7...High frequency power supply, 8...Target, 9...Substrate holder, lO
... Substrate, 11... Shutter, 12... Film thickness sensor, 13... Supply port, 14... Supply port, 15...
exhaust port

Claims (1)

[Claims] Pre-sputtering is performed by introducing an inert gas and discharging the space between the sputtering area where the target material is set and evacuated and the substrate in a state of isolation, and the film-forming speed of pre-sputtering is stabilized by a film thickness sensor. It is characterized by detecting that the target substance and reactive gas have been reached, canceling the cut-off state, introducing inert gas and reactive gas at a required flow rate ratio, and discharging to form a film of a compound of the target material and reactive gas on the substrate. Reactive sputtering film formation method