JPH09302469A - Sputtering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain metallic coating of good quality and to improve the using efficiency of a metallic target, at the time of forming multilayer coating by a reactive sputtering method, by applying specified pulse-shaped electric power in the case of the formation of metallic coating. SOLUTION: Cathode electrodes mounted with target material are plurally arranged in the conveying direction of a substrate, and coating of >= two layers is laminated on the substrate to be conveyed by a sputtering method. At least one layer of this multilayer coating is composed of metallic oxide coating or metallic nitride coating formed by a reactive sputtering. At the time of forming this metallic coating, periodical pulse-shaped electric power is applied to the metallic target. Namely, the pulse-shaped electric power in which the ratio given by the time for which the sputtering electric power is applied to the cathodes/(the time for which the sputtering electric power is applied + the time for which the sputtering electric power is not applied) is regulated to 0.5 to 0.05. The time for which the sputtering electric power is applied to the cathodes is preferably regulated to >=5μsec in one period.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sputtering method.

[0002]

2. Description of the Related Art A sputtering apparatus (hereinafter referred to as an in-line apparatus) that forms a thin film on a substrate by transporting a plurality of multilayer thin films of two or more layers by arranging a plurality of cathode electrodes mounted with a target material in the substrate transport direction and discharging at the same time. In the (multilayer film sputtering apparatus), the substrate transfer speed is determined according to the thin film with the lowest thin film formation speed, and the power of the cathode that sputters the thin film of the layer with the fastest thin film formation speed is set low and the thin film formation speed is set. There is a method of matching the above with other thin film forming rates.

On the other hand, in one-time transfer of a substrate, discharge is carried out in an oxygen or nitrogen gas atmosphere to carry out reactive sputtering to form a thin film such as an oxide film or a nitride film having a slow film formation rate, while argon or the like is used. The following problems occur when a multilayer film is formed by discharging in an inert gas atmosphere and performing sputtering to form a metal film having a high thin film formation rate.

First, relatively large electric power must be applied to the cathode for reactive sputtering to generate reactive plasma having a high plasma density, and the flow rate of the reactive gas also increases.

Even if an inert gas is introduced in the same vacuum chamber as that of the cathode, in the in-line type multi-layer film sputtering apparatus, the influence of the reactive gas and the reactive plasma having a high density cannot be avoided, and a pure metal film is obtained. Will be difficult to obtain.
Especially when a thin film is required for this metal film, it is difficult to obtain a thin film having the desired properties as a metal film.

It is considered that this is because the surface of the target material is contaminated with reactive plasma or reactive gas, and the sputtered particles are oxidized or nitrided.

For example, in the in-line type multilayer film sputtering apparatus of FIG. 1, titanium is attached to the target material in the sputtering chambers 33a and 33c, oxygen gas is introduced, and TiO ₂ is produced by reactive sputtering, Spatter room 3
In 3b, when silver is attached to the target material, argon gas is introduced, and a thin film of silver can be formed by sputtering, a three-layer multilayer film composed of TiO ₂ , Ag, and TiO ₂ is prepared. The problem of occurs.

First, although the sputter chamber 33b is in an argon atmosphere, a small amount of oxygen gas or oxygen plasma introduced into the adjacent sputter chambers leaks through the conductance 48. If the electric power supplied to the cathode 44b is small, the oxygen gas or the like oxidizes the surface of silver of the target material, and the formed thin film also becomes silver oxide.

In order to solve this problem, the power supply 46b
It turns out that increasing the power of will solve the problem. For this device, it was above 3 kW. However, the formation rate of the thin film of TiO ₂ is
There is a difference of about 1/20 when sputtering with the same power. That is, when the three-layer films to be obtained have the same thickness,
At least 60 kW or more is required for the cathode equipped with titanium.

Therefore, in the conventional technique, as described above, reactive sputtering (in this case, TiO 2) having a slow thin film formation rate is performed.
₂ ) and spatter with high thin film formation rate (in this case, silver)
In order to use at the same time, on the basis of the power of the sputter with a fast thin film formation speed, the slow reactive sputtering side decides the power that can obtain the thin film formation speed corresponding to it, and the cooling method of the target material to input a large power It is necessary to select limited operating conditions and device configurations that require a special device configuration such as a power supply device and a power supply device.

In reality, it is possible to supply a large amount of power by first determining a sputtering condition with a low thin film forming rate from the limit input power of the apparatus and applying a corresponding power to the sputtering side with a high thin film forming speed. It is far more economical and rational without the need for special equipment.

Conventionally, the simplest method for solving the above problems is to provide a narrow space between a target having a high thin film forming speed and a substrate to physically suppress the thin film forming speed and then to obtain a desired property. The method of applying the obtained electric power was general.

Therefore, a narrow space is provided between the target on which the silver target is mounted and the substrate, and the amount of sputtered silver particles coming in is physically reduced to suppress the thin film formation rate and to reduce the overall thickness. I decided the driving conditions. In this case, TiO
_{Since the} electric power that can be applied to the thin film formation of No. ₂ was limited to 20 kW, a mechanism for limiting the silver thin film formation speed to 1/3 or less was installed and operated, but the following problems occurred.

First, if sputtering is continued for a long time, the thin film formation rate will decrease as the target material is consumed.
Since the minimum value of input power is limited in order to adjust the silver rate in accordance with the decrease in the iO ₂ thin film formation rate,
Since the size of the aperture space had to be changed successively, the operating rate of the device decreased. This fluctuation can be corrected by slowing the substrate transport speed, but the rate of decrease in the sputtering speed of each target is not uniform, so it was not a complete solution.

Further, most of the thin film material from the silver target is wasted on the diaphragm mechanism, so the utilization efficiency of the target is very low and it is uneconomical.

As described above, in this method, most of the sputtered particles are attached to the mechanical parts for forming the above-mentioned narrow space, so that the utilization efficiency of the target is poor and, in particular, it is low. Since it is difficult to form a thin film with electric power, there is a problem because the advantage of the sputtering method that the thickness of the thin film is arbitrarily and accurately controlled by adjusting the electric power is lost.

Therefore, when a multilayer film including a thin film having a low thin film formation rate and a metal film having a high thin film formation rate is formed by reactive sputtering using an in-line type sputtering apparatus, a good quality metal film is obtained, and There has been a demand for a sputtering method with high usage efficiency of a metal target.

[0018]

SUMMARY OF THE INVENTION The present invention provides a metal of good quality when a multilayer film including a thin film having a slow thin film forming rate and a metal film having a fast thin film forming rate is formed by reactive sputtering in an in-line type sputtering apparatus. An object of the present invention is to provide a sputtering method in which a film can be obtained and the usage efficiency of a metal target is high.

[0019]

SUMMARY OF THE INVENTION The present invention is a multilayer thin film in which a plurality of cathode electrodes, each having a target material attached thereto, are arranged in the substrate transport direction, and two or more layers are laminated on the substrate by one substrate transport. In the sputtering method for forming, at least one layer is a metal oxide film or a metal nitride film formed by reactive sputtering, and further at least one layer is a metal film, in forming the metal film,
The ratio of the periodic pulsed power to the metal target, which is given by the time when the sputtering power is applied to the cathode / (the time when the sputtering power is applied + the time when the sputtering power is not applied) is 0, There is provided a sputtering method characterized by applying a pulsed electric power of 0.5 to 0.05.

FIG. 1 schematically shows the in-line type multilayer film sputtering apparatus of the present invention.

The vacuum chamber 31 is composed of a load chamber 32, a sputter chamber 33 and an unload chamber 34, and the sputter chamber 33a, 33b, 33c is an example of an apparatus comprising three chambers. Each chamber is evacuated by vacuum evacuation means 35, 36a, 36b, 36c, 37 including an evacuation valve, and the respective atmospheres can be communicated or partitioned by partition valves 38, 39, 40, 41.
The substrate 42 is a device that can continuously form a thin film by sputtering while the vacuum state of the sputtering chamber is maintained by the substrate transfer means 43.

In each of the sputtering chambers, cathodes 44a, b, c with target materials mounted and anodes 45a, b, c are attached.
And power supplies 46a, b for supplying sputtering power to them,
c, and gas introducing means 47a, b, c including a gas supply source necessary for sputtering and a flow rate control valve, etc., and conductance 48 is provided between the chambers, so that the process gas in each chamber is Even if the type and mixing ratio differ,
Since the atmosphere which is isolated to some extent is maintained, it is possible to create independent process conditions necessary for forming a thin film from each target material.

Therefore, in this apparatus, since 44a, b, and c can be discharged at the same time, a maximum of three layers of thin film can be laminated by one transfer of the substrate 42, and if necessary, the unload chamber 34 and the unload chamber 34 can be stacked. By reciprocating between the load chambers 32, a thin film having a larger number of layers can be obtained by transporting the substrate once, so that it is possible to form a thin film having a more multilayer structure on the substrate. In particular, in the device of the present invention, the power supply 46 is
It is possible to supply pulsed electric power as shown in FIG.

Sputtering power input time T _on /
(The ratio given by the time T _{on when the} sputter power is applied + the time T _{off when the} sputter power is not applied) (hereinafter,
The duty ratio) is 0.5 to 0.05.

Generally, the average power P _ave of the pulse-like waveform is
And the duty ratio ρ are represented by the following equation. P _max
Is the maximum electric power at the moment when the sputtering is actually performed.

[0026]

## EQU1 ## ρ = T _on / (T _on + T _off )

[0027]

(2) P _ave = ρP _max

Therefore, the maximum electric power P _{max at the} moment of sputtering is 2 to 20 times the average electric power P _ave .

Further, T _on per cycle is preferably 5 μs or more. This is less than 5 microseconds, or 100k
At frequencies above Hz, the influence of the electrode structure and the impedance components of the wiring cables cannot be avoided, and it becomes necessary to provide an impedance matching circuit, etc. in the power circuit, making the device configuration complicated and economical. Because it is disadvantageous.

The time T _on + T _off is preferably in the range of 10 microseconds to 16 milliseconds or less.

In the apparatus of FIG. 1, the effect of the present invention does not change even if the anode has a vacuum chamber and a conductive potential (ground potential), and the anode is not limited. Although the waveform of FIG. 2 is a rectangular wave, it may be a half-wave shape of a sine wave, a triangular wave shape, a sawtooth shape, or a distorted waveform thereof.

The power supply 46 of the present invention is preferably capable of outputting both normal DC power and pulse power.

[0033]

【Example】

(Example 1) In the in-line type multilayer film sputtering apparatus of FIG. 1, titanium was attached to a target material in the sputtering chambers 33a and 33c, oxygen gas was introduced, and TiO ₂ was generated by reactive sputtering. In the sputtering chamber 33b, silver was attached to the target material, argon gas was introduced, and a thin silver film was formed by sputtering.
A three-layer multilayer film composed of TiO ₂ , Ag and TiO ₂ was prepared.

Although the sputter chamber 33b has an argon atmosphere, oxygen gas or oxygen plasma introduced into the sputter chambers on both sides of the sputter chamber 33b leaks through the conductance 48 in a small amount. If the electric power supplied to the cathode 44b is small, the oxygen gas or the like will oxidize the surface of silver of the target material, and the thin film formed will also become silver oxide. Therefore, it is necessary to apply 3 kW or more. there were. TiO
Rate of formation of the _second thin film is different from the silver thin film forming speed, since there is a difference of about 1/20 when sputtered at the same power, the thickness of each of three-layer film is the same, the titanium target Requires the application of 60 kW or more.

Using the same apparatus, T _on was set to 100 microseconds, T _off was set to 200 microseconds, the sputtering power at the time of T _on was set to 3 kW, and the pulse power to obtain the average power of 1 kW was used. A high-quality thin film that is equivalent to a high-quality thin film obtained at a direct current of 3 kW with electric power and that is not oxidized can be formed without a diaphragm mechanism, etc., and the use efficiency of the target material has been remarkably improved.

Even if the thin film forming speed is reduced due to long-term use, the electric power may be increased with the duty ratio as it is.

In this embodiment, a multilayer film structure of an oxide film and a metal film is shown as an example, but the same applies to the case of a metal film and a nitride film, for example.

[0038]

According to the present invention, in in-line type multi-layer film sputtering, even when a thin film formed by reactive sputtering and having a low thin film forming speed and a metal film having a high thin film forming speed are formed. Since a high-quality metal film that is not affected by the reactive atmosphere can be obtained and a special diaphragm mechanism for suppressing the thin film formation speed is not required,
The target can be used efficiently.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an apparatus used in the present invention.

FIG. 2 is a waveform of pulse power used in the present invention.

[Explanation of symbols]

 31: Vacuum chamber 32: Load chamber 33a, 33b, 33c: Sputtering chamber 34: Unload chamber 35, 36a, 36b, 36c, 37: Vacuum evacuation means 38, 39, 40, 41: Partition valve 42: Substrate 43: Substrate 43 Conveying means 44a, 44b, 44c: Cathode 45a, 45b, 45c: Anode 46: Power source 47a, 47b, 47c: Gas introducing means 48: Conductance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiro Yamada 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. A sputtering method for arranging a plurality of cathode electrodes, each having a target material mounted thereon, in a substrate transport direction to form a multilayer thin film in which two or more layers are stacked on a substrate by one substrate transport. One layer is a metal oxide film or a metal nitride film formed by reactive sputtering, and at least one layer is a metal film. In forming the metal film, a periodic pulsed electric power is applied to the metal target. And the pulsed electric power having a ratio of 0.5 to 0.05 given by the time when the sputtering power is applied to the cathode / (the time when the sputtering power is applied + the time when the sputtering power is not applied) is 0.5 to 0.05. A sputtering method, characterized in that 2. The sputtering method according to claim 1, wherein the time during which the sputtering power is applied to the cathode is 5 μsec or more in one cycle.