JPH0734239A - Sputtering device - Google Patents

Abstract

PURPOSE:To prevent the generation of an arc discharge with the sputtering device by supporting a substrate with a resistor having the resistance value equal to or higher than plasma impedance. CONSTITUTION:About 1 to 10<-1>Pa is generated by gaseous Ar in a sputtering chamber 51 and DC electric power is impressed via a cathode 54 to a target 52 to generate plasma near the surface of the target 52. A magnetic field is generated on the surface of the target 52 by a magnet 53 to increase the density of the plasma and to drive out sputtered particles, by which the thin film is formed on the substrate 56 incorporated with a bias potential by a DC fixed voltage power source 58. The substrate 56 is supported via the resistor 1 having the resistance value equal to or higher than the plasma impedance at this time. As a result, the input impedance of a bias line consisting of the substrate 56, the resistor 1 and the power source 58 is increased and the generation of an arc discharge is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering apparatus used for forming a thin film in a thin film application device such as a semiconductor or a thin film magnetic head.

[0002]

2. Description of the Related Art A sputtering apparatus for applying a bias to a substrate changes the state of plasma by applying a bias potential to the substrate to control the incident angle and incident energy of sputtered particles and argon ions reaching the substrate. However, the film is formed. By applying a bias, the incident angle and energy of sputtered particles or argon ions can be controlled, and as a result, physical properties such as stress and hardness of a formed film can be controlled. It is often used for thin film formation in thin film applied devices.

A conventional sputtering apparatus will be described below with reference to FIG. FIG. 5 shows a conventional sputtering device. In the figure, 51 is a chamber, 52 is a target, 53 is a magnet, 54 is a cathode, 55 is a direct current or high frequency power supply, 56 is a substrate, 57 is a substrate holder,
Reference numeral 58 is a DC constant voltage power supply for bias application.

The operation of the sputtering apparatus constructed as above will be described below. The sputtering chamber 51 is filled with argon gas having a pressure of about ¹ to 10 ⁻¹ Pa. Plasma is generated in the vicinity of the surface of the target 52 by applying high frequency or DC power to the target through the cathode 54. At this time, the magnetic field generated on the surface of the target 52 by the magnet 53 causes cyclotron motion of the electrons, so that the number of collisions between the electrons and the argon gas increases and the density of the plasma increases. Argon ions, which are cations in the densified plasma, collide with the target 52 having a negative potential to knock out the atoms forming the target 52. The knocked out atoms are called sputtered particles. The sputtered particles are the target 52
A film is formed by depositing it on a substrate 56 placed opposite to. When a film is formed, by applying a negative bias potential from the DC constant voltage power source 58 to the substrate 56, the energy and incident angle of sputtered particles and argon ions incident on the substrate, and the plasma state can be controlled. As a result, physical properties such as stress and hardness of the film can be controlled.

[0005]

However, in the above conventional structure, when a film is formed while applying a bias on a substrate having high electrical conductivity or a substrate having a highly electrically conductive film on the substrate surface, There is a problem that arc discharge occurs and the substrate surface is damaged. FIG. 6 shows the time change of the current flowing through the bias line at that time. An arc current that is 5 to 10 times that of a normal current value level is generated in the order of hundreds of microseconds.

The present invention solves the above conventional problems, and an object of the present invention is to provide a sputtering apparatus in which arc discharge does not occur even when a film is formed while applying a bias to a substrate.

[0007]

To achieve this object, in the first aspect of the present invention, a bias can be applied to the substrate through a resistor.

In a second aspect of the present invention, a DC constant voltage power source for applying a bias to a substrate has a frequency characteristic of 10 k.
It is characterized by using a DC constant voltage power source of Hz or higher.

In a third aspect of the present invention, the DC power supply for applying a bias to the substrate is a DC power supply capable of switching between constant current control and constant voltage control, and has a control circuit for enabling the switching. It is a feature.

[0010]

According to the first aspect of the present invention, by providing the resistor between the substrate and the substrate holder, the input impedance of the line for applying the bias to the substrate can be increased. As a result, it is possible to prevent the occurrence of arc discharge which is caused by easy current flow, that is, low input impedance.

According to the second aspect of the present invention, an arc discharge which causes damage to the surface of the substrate by applying a current limiter to the arc discharge generated on the order of several hundred micro-disease using a DC power supply having a frequency characteristic of 10 kHz or more. It is possible to prevent an electric current from being generated.

According to the third aspect of the present invention, when the resistance value of the film to be formed is high, first, a bias is applied to the substrate by constant current control to prevent the generation of an arc current and prevent the generation of an initial layer of several tens of liters. A film is formed. Since the resistance of the formed film is high,
Similarly to the invention described above, since the input impedance of the bias line becomes high, arc discharge does not occur even if a bias is applied by constant voltage control after which the film quality stabilizes.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sputtering apparatus showing a first embodiment of the present invention. In the figure, the same parts as those in FIG. In this embodiment, as shown in the figure, since the substrate 56 is held via the resistor 1, the substrate 56, the resistor 1,
The input impedance of the bias line composed of the bias applying DC power supply 58 becomes high. As a result, it becomes difficult for arc discharge to occur where the impedance is low. The higher the impedance, in the case of this example, the higher the resistance value of the resistor, the less likely arc discharge will occur, but when applying a bias potential to the substrate, the resistance value of the resistor is increased. Since the voltage drop across the resistor also increases proportionally, extra power is required for the voltage drop. The resistance value that can most effectively apply the bias to the substrate while preventing arc discharge is a resistance value similar to the plasma impedance between the target 52 and the substrate 56. For example, as the resistor 1, a conductive rubber sheet whose resistance value can be changed by the amount of silver contained therein is used. This rubber sheet has good thermal conductivity and can be used when the temperature control of the substrate is required.

FIG. 2 is a sputtering apparatus showing a second embodiment of the present invention. This sputtering apparatus has almost the same structure as the conventional one shown in FIG. However, the DC constant voltage power supply 2 for applying a bias potential to the substrate has a frequency characteristic of 10 unlike the conventional one.
It is assumed that the frequency is kHz or more, that is, the reaction speed of the power source is 100 microseconds or more. With this configuration, the arc current generated in the order of hundreds of microseconds can be prevented by the current limiter of the constant current power supply. FIG. 3 shows the time change of the current value flowing through the bias line at that time. The arc current tries to flow in the order of hundreds of microseconds, but the current limiter works at a higher speed to prevent the arc current, so that arc discharge does not occur.

FIG. 4 is a sputtering apparatus showing a third embodiment of the present invention. In the figure, the same parts as those in FIG. In the figure, 3 is a direct current power source capable of switching between constant current control and constant voltage control,
4 is a film thickness monitor. When the resistance value of the film to be formed is high, first, a bias potential is applied to the substrate 4 by using the power source 3 as a constant current power source so that arc discharge can be prevented in the first several tens of layers. At that time, the film thickness is simultaneously monitored while monitoring the film thickness with a film thickness monitor, and when the film thickness reaches several tens of liters, a control circuit is provided to switch the power supply 3 from a constant current to a constant voltage power supply. Since the resistance value of the film to be formed is high, the impedance of the bias line becomes high as in the first aspect of the invention, so that arc discharge can be prevented even after switching to the constant voltage power supply.

If the initial film thickness is too thin, the film becomes an island-shaped film instead of a continuous film, so that a portion with a low impedance locally occurs, and arc discharge cannot be prevented. Further, when a constant current power supply is used, the voltage applied to the substrate becomes unstable due to unstable plasma impedance, so that the film quality becomes unstable if the initial film thickness is too thick. Therefore, in order to prevent arc discharge and obtain stable film quality, it is necessary to optimize the film thickness of the initial layer to which a bias is applied by a constant current power supply. The film thickness at which arc discharge does not occur depends on the resistance value of the film, but is 50 Å or more, and the film thickness at which stable film quality is obtained is 10% or less of the total film thickness.

[0017]

As described above, according to the first aspect of the present invention, the input impedance of the bias line is increased by holding the substrate through the resistor having a resistance value similar to the plasma impedance. As a result, it is possible to prevent the occurrence of arc discharge.

A second aspect of the present invention has a frequency characteristic of 10
By applying a bias to the substrate with a constant current power source of kHz or higher, arc discharge that occurs on the order of hundreds of microseconds can be prevented by the current limiter.

According to a third aspect of the present invention, when the resistance value of the film to be formed is high, a bias is applied to the substrate by constant current control so that arc discharge can be prevented from forming the first tens of layers. I do. As a result, the impedance of the bias line becomes high as in the case of the first aspect of the present invention, and the occurrence of arc discharge can be prevented even after switching to constant voltage control that stabilizes the film quality.

[Brief description of drawings]

FIG. 1 is a sectional view of a sputtering apparatus showing an embodiment of the first invention of the present invention.

FIG. 2 is a sectional view of a sputtering apparatus showing an embodiment of the second invention of the present invention.

FIG. 3 is a diagram showing a change over time of a bias current according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a sputtering apparatus showing an embodiment of the third invention of the present invention.

FIG. 5 is a sectional view of a conventional sputtering device.

FIG. 6 is a diagram showing the change over time of the bias current of a conventional sputtering apparatus.

[Explanation of symbols]

 1 resistor 56 substrate

Claims (3)

[Claims] 1. A sputtering apparatus, wherein a substrate is supported via a resistor having a resistance value substantially equal to or higher than plasma impedance. 2. The sputtering apparatus according to claim 1, wherein the constant current power supply for applying a bias potential to the substrate is a constant current power supply having a frequency characteristic of 10 kHz or more. 3. A DC power supply for applying a bias potential to a substrate is a DC power supply capable of switching between constant current control and constant voltage control, and switching between constant current control and constant voltage control depending on film thickness or film formation time. The sputtering apparatus according to claim 1, further comprising a control unit capable of performing the above.