JPH06145973A - Sputtering device - Google Patents

Abstract

PURPOSE:To form a film having good film quality and to enable film formation at a high speed by decreasing the influence by an arc discharge with the sputtering device. CONSTITUTION:This sputtering device is constituted of a target electrode 5 having a target 4 in a vacuum chamber 1, a substrate 3 to be deposited with the film consisting of the target 4 as one component, a high-frequency electric power section 10 for charging high-frequency electric power to the target electrode 5 and a series circuit of an inductor 21 and capacitor 22 connected in parallel to the target electrode 5. The bias voltage to be impressed to the target 4 is changed from negative to 0 or positive when the arc discharge is generated on the surface of the target 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering apparatus for forming a thin film on a substrate using glow discharge plasma.

[0002]

2. Description of the Related Art Sputtering, vacuum deposition, and ion plating are known as physical methods for forming a thin film of a semiconductor device. Among the thin film forming methods, sputtering is a method of depositing particles emitted from a target on a wafer to form a film. Then, the particles are discharged by causing a glow discharge between both electrodes facing each other with the target being a cathode and the wafer side being an anode, and causing argon ions in the glow discharge to collide with the target.

As a sputtering apparatus for performing this sputtering, there are a DC sputtering apparatus used for forming a metal or alloy thin film, a high frequency sputtering apparatus used for forming an insulating film, and a bias sputtering apparatus used for forming a flattened insulating film or a flattened Al film. Are known. Hereinafter, a conventional high-frequency sputtering device among the sputtering devices will be described.

FIG. 8 is a configuration diagram for explaining a conventional high frequency sputtering apparatus, FIG. 9 is a voltage diagram when a rectangular wave is applied, and FIG. 10 is a voltage diagram when a sine wave is applied. 8, 9 and 10, 2 is a substrate holder, 3 is a substrate, 4 is a target, 5 is a target electrode,
11 is a high frequency power source, C is a capacitor, V _S is a target surface voltage, V _M is a target electrode voltage, and V _b is a bias voltage.

First, consider the case where a DC power supply is used in place of the high frequency power supply 11 in the high frequency sputtering apparatus of FIG. Here, the target 4 is an insulator. When a negative voltage is applied to the target electrode 5, the surface of the target 4 is covered with positive charges brought by the ions flowing from the plasma. Due to this positive charge, the target surface voltage V _S becomes equal to the plasma voltage. Therefore, the discharge is stopped and the sputtering is stopped. Therefore, the substrate 3
Cannot be sputtered on.

Next, consider the case where a rectangular wave is applied to the target electrode 5. This case is shown in FIG. 9, where the target surface voltage V _S is shown by the thick solid line and the target electrode voltage V _M is shown by the broken line. First, when a rectangular-wave target electrode potential V _M is applied to the target electrode 5, electrons are immediately collected on the surface of the target 4 in the positive half wave, and the surface of the target 4 becomes equal to the voltage of plasma. Here, a capacitor is formed and charging is performed between the target surface voltage V _S of the target 4 and the voltage plane of the target electrode voltage V _M.

In the next negative half-wave, the target surface voltage V _S changes to a negative voltage. In this negative half-wave, ions flow into the target 4 and sputtering is performed. However, since the ions have a lower mobility than the electrons, they are slowly collected to the target 4, and the target surface voltage V _S slowly approaches the plasma voltage. At this time, the charged capacitor is slowly discharged in the positive half wave.

Further, in the next positive half wave, the target surface voltage V _S is charged again. By repeating this, the surface of the target 4 becomes the same as the bias voltage of V _b is superposed, and the sputtering of the insulator can be performed. When a sine wave is applied to the target electrode 5, the bias voltage of V _b is similarly superimposed.

That is, by using the high frequency power supply 11, a high frequency current flows through the capacitance between both surfaces of the insulator, and the insulator can be sputtered.
Further, when metal is sputtered, it is possible to similarly sputter by inserting a capacitor C, which replaces the capacitance between both surfaces of the insulator, in the circuit.

Next, the structure of a conventional sputtering apparatus will be described. FIG. 11 is a block diagram of a conventional sputtering apparatus. In FIG. 11, 1 is a vacuum chamber,
Reference numeral 2 is a substrate holder, 3 is a substrate, 4 is a target, 5 is a target electrode, 7 is an insulator, 10 is a high frequency power unit, 11 is a high frequency power source, 12 is a matching circuit, a gas supply unit 30, and a gas exhaust unit 40. .

The conventional sputtering apparatus includes a vacuum chamber 1 in which a substrate 3 is housed and a film is formed, and a high frequency power unit 10 for applying high frequency power to the vacuum chamber 1.
And a gas supply unit 30 for supplying gas into the vacuum chamber 1.
And a gas exhaust unit 40 for exhausting air and gas in the vacuum chamber 1. In the above structure, the two electrodes of the substrate holder 2 and the target electrode 5 are arranged in the vacuum chamber 1 so as to face each other with a gap. Of the two electrodes, the target electrode 5 supports the target 4 on the surface facing the substrate holder 2 and receives the high frequency power from the high frequency power unit 10. On the other hand, the substrate holder 2 supports the substrate 3 to be sputtered on the surface facing the target electrode 5 and is grounded.

The target electrode 5 and the vacuum chamber 1
An insulator 7 is provided between the two and is electrically insulated. The high frequency power unit 10 includes a high frequency power source 11 and a matching circuit 12. This matching circuit 12 is a high frequency power source 1
The output impedance of 1 and the impedance of plasma in the vacuum chamber 1 are matched, and high frequency power is efficiently input to the target electrode 5.

Further, the gas supply unit 30 and the gas exhaust unit 40
Is for adjusting the pressure and gas concentration in the vacuum chamber 1. Next, the operation of the conventional sputtering apparatus having the above structure will be described. First, the gas exhaust unit 40 performs an exhaust operation to bring the vacuum chamber 1 into a vacuum state, and then the gas supply unit 30 supplies an inert gas or a gas that reacts with the material of the target 4 into the vacuum chamber 1.

In this state, the high frequency power supply 11 causes the matching circuit 12 to
When a high frequency voltage is applied to the target electrode 5 via
Glow discharge occurs between the target electrode 5 in the vacuum chamber 1 and the ground voltage of the substrate holder 2. At this time, a negative bias voltage is generated in the target electrode 5. The generation of this negative bias voltage is due to the difference in mobility of ions and electrons in plasma as described above.

The ions in the plasma are accelerated toward the target electrode 5 side by the negative bias voltage and sputter the target 4 placed on the target electrode 5. This sputter causes target 4 to emit target atoms. The released target atoms are deposited on the substrate 3 placed on the substrate holder 2 to form a thin film containing the target atoms as a component.

[0016]

However, the above-mentioned conventional sputtering apparatus has problems that the quality of the thin film is deteriorated due to the occurrence of arc discharge and the film forming process is interrupted. Hereinafter, the problem will be described.
Usually, in a sputtering apparatus, it is important to increase the film formation rate in order to increase the productivity of film formation. Then, in general, in order to increase the film forming rate, the input amount of high frequency power is increased.

When the ITO oxide target is sputtered in the conventional sputtering apparatus shown in FIG. 8, an arc discharge is generated on a part of the surface of the target 4 as the input amount of the high frequency power is increased. The occurrence of this arc discharge is considered to be due to the following process. A negative bias voltage is generated in the target electrode 5 when the glow discharge occurs. At this time, when the amount of high frequency power supplied to the target electrode 5 is increased, the negative bias voltage is also increased, the target 4 is impacted by the fast ions, and the secondary electron emission from the target 4 is also increased. Here, if there is a protrusion on the surface of the target 4, it is considered that secondary electron emission occurs intensively at that portion, and glow discharge shifts to arc discharge.

In this arc discharge, the target 4 in the portion where the arc discharge is generated is melted and the melted target piece is discharged. The ejected target pieces are scattered and reach the substrate 3. This target piece causes defects in the thin film formed on the substrate 3 and deteriorates the film quality. When a normal arc discharge occurs, the output of the high frequency power supply 11 is stopped at that point to stop the generation of the arc discharge, the output of the high frequency power supply 11 is restarted, and the sputtering is restarted. When the sputtering is restarted, the impedance of the high frequency power source 11 and the impedance of the plasma are matched by the matching circuit 12.

However, when the output of the high frequency power supply is stopped and the sputtering is restarted, it takes at least about 1 second until the glow discharge is stabilized, and the film formation is interrupted during this period. Moreover, since the frequency of arc discharge is about once every several tens of seconds, the output of the high-frequency power source is generally stopped several times during one film formation, and each time it takes about 1 second. There is a problem that the film forming process is stopped over time.

Therefore, the film formation is interrupted for a long time, which makes it difficult to form the film at a high speed, and the quality of the film is deteriorated as compared with the case where the film is formed continuously. Therefore,
An object of the present invention is to solve the problems of the above-described conventional sputtering apparatus, and in the sputtering apparatus, reduce the influence of arc discharge to form a film of good quality and enable high-speed film formation. And

[0021]

In order to achieve the above object, the present invention is directed to a target electrode having a target in a vacuum chamber, a substrate on which a film containing the target material as a component is deposited, and a high frequency wave to the target electrode. A sputtering device is composed of a high-frequency power supply unit for supplying electric power and a series circuit of an inductor and a capacitor connected in parallel to the target electrode, and a bias applied to the target when arc discharge occurs on the target surface. The voltage is changed from negative to 0 or positive.

[0022]

According to the present invention, in the sputtering apparatus, the charging / discharging portion including the inductor and the capacitor is connected between the target electrode and the ground voltage. Then, in a normal state at the time of glow discharge occurrence, the negative bias voltage of the target electrode charges the capacitor of the charging / discharging part, and when the arc discharge occurs due to the increase of the high frequency power input to the target electrode, the charging / discharging part This is to discharge the capacitor. Thereby, when the arc discharge occurs, the bias voltage of the target electrode is changed from negative to 0 or positive, and the arc discharge is extinguished.

[0023]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a sputtering apparatus of the present invention. In FIG. 1, 1 is a vacuum chamber, 2 is a substrate holder, 3 is a substrate, 4 is a target, 5 is a target electrode, 7 is an insulator, 10 is a high frequency power unit, 11 is a high frequency power supply, 12 is a matching circuit, and 20 is A charging / discharging unit, 21 is an inductor, 22 is a capacitor, 30 is a gas supply unit, and 40 is a gas exhaust unit.

In the sputtering apparatus of the present invention, the charging / discharging section 20 is connected between the high frequency power section 11 and the target electrode 5 of the conventional sputtering apparatus. This is an impedance in which the impedance of the vacuum chamber 1 side and the impedance of the charging / discharging unit 20 are electrically connected in parallel when viewed from the high frequency power unit 10. Therefore, in FIG. 1, the sputtering apparatus of the present invention comprises a vacuum chamber 1 for accommodating a substrate 3 and performing film formation, a high-frequency power unit 10 for applying high-frequency power to the vacuum chamber 1, and a vacuum chamber 1. The charging / discharging unit 20 performs charging / discharging between the vacuum chamber 1, a gas supply unit 30 that supplies gas into the vacuum chamber 1, and a gas exhaust unit 40 that exhausts air or gas in the vacuum chamber 1.

The above-mentioned components will be described below. In the above-mentioned configuration, like the conventional sputtering device,
A substrate holder 2 and a target electrode 5 are provided in the vacuum chamber 1.
Two electrodes of the above are arranged facing each other with a space. Of the two electrodes, the target electrode 5 supports the target 4 on the surface facing the substrate holder 2 and receives the high frequency power from the high frequency power unit 10. on the other hand,
The substrate holder 2 supports the substrate 3 to be sputtered on the surface facing the target electrode 5, and
It is grounded.

The target electrode 5 and the vacuum chamber 1
An insulator 7 is provided between the two and is electrically insulated. The high frequency power unit 10 includes a high frequency power source 11 and a matching circuit 12. The matching circuit 12 matches the output impedance of the high frequency power source 11 with the impedance of the plasma in the vacuum chamber 1 as described above, and efficiently inputs the high frequency power to the target electrode 5.

Further, the gas supply unit 30 and the gas exhaust unit 40
Is for adjusting the pressure and gas concentration in the vacuum chamber 1. Further, the charging / discharging unit 20 which is a component of the present invention
Is configured by connecting an inductor 21 and a capacitor 22 in series, and constitutes a resonance circuit together with the impedance on the vacuum chamber 1 side.

The charging / discharging unit 20 will be described below. The charging / discharging unit 20 extinguishes the arc discharge described above. Here, in FIG. 1, the matching circuit 12
2 when the impedance when looking at the side of the vacuum chamber 1 in the direction of arrow A is Z _A and the impedance when looking at the side of the charging / discharging unit 20 in the direction of arrow B from the matching circuit 12 is Z _B It is a circuit diagram of a vacuum chamber and a charging / discharging part as shown. The impedance Z _A is the impedance of the load during discharge in the vacuum chamber 1.

First, the voltage of the target 4 when the discharge in the vacuum chamber 1 of the sputtering apparatus of the present invention is in a normal state will be described. When the discharge in the vacuum chamber 1 is in a normal state, glow discharge has occurred. Figure 3
FIG. 4 is a voltage diagram of a target when glow discharge is generated in the vacuum chamber. At the time of this glow discharge, the high frequency voltage V _PPG is applied to the target electrode 5 from the high frequency power supply 11. The application of the high frequency voltage V _PPG will generate the negative bias voltage V _DcG on the surface of the target 4 as described above. To the capacitor C of FIG. 2, only this negative bias voltage V _DcG is applied and charged in terms of direct current.

Here, as described above, when the input amount of the high frequency power to the target electrode 5 is increased, the negative bias voltage V _DcG is also increased, the target 4 is impacted by the fast ions, and the secondary from the target 4 is generated. Electron emission also increases. At this time, for example, if there are projections or the like on the surface of the target 4, secondary electron emission is intensively generated at that portion, and glow discharge shifts to arc discharge.

Next, the target 4 when the discharge in the vacuum chamber 1 of the sputtering apparatus of the present invention is arc discharge
The voltage will be described. FIG. 4 is a voltage diagram of the target when arc discharge is generated in the vacuum chamber. When the discharge in the vacuum chamber 1 shifts from the glow discharge to the arc discharge as described above, the absolute value of the impedance Z _A of the load during the discharge in the vacuum chamber 1 decreases. This is because the arc discharge impedance is smaller than the glow discharge impedance due to the characteristics of the discharge.

When the impedance Z _A in the vacuum chamber 1 greatly changes from the value during glow discharge, the matching circuit 12
Becomes inconsistent. Therefore, the high frequency voltage V _PPA on the target electrode 5 during arc discharge is smaller than the high frequency voltage V _PPG on the target electrode 5 during glow discharge shown in FIG. Further, as shown in FIGS. 3 and 4, the bias voltage V _DcA during arc discharge also decreases due to the low impedance Z _A during arc discharge.

The decrease in the bias voltage V _DcA during the arc discharge changes the voltage of the capacitor in the charging / discharging section 20. This voltage change will be described with reference to the voltage diagram of the capacitor in the charging / discharging unit of FIG. In FIG. 5, V _DcG is a negative bias voltage during glow discharge, and V _DcA is a negative bias voltage during arc discharge.

Therefore, due to the decrease of the impedance Z _A , the electric charge charged in the capacitor C is discharged to the arc discharge load in the vacuum chamber 1. Next, a process of extinguishing the arc discharge due to the discharge of the capacitor C will be described.

FIG. 6 is an equivalent circuit diagram of the vacuum chamber and the charging / discharging section. In FIG. 6, R _A is the resistance in the vacuum chamber 1 during arc discharge. Here, at the time constant level determined by the inductor L and the capacitor C of the charging / discharging unit shown in FIG. 6, the matching circuit 12 can be ignored, and the impedance Z _A of the arc discharge load is the resistance component R _A.
Only _A.

In FIG. 6, in the initial glow discharge state, the capacitor C is charged with electric charge,
In the arc discharge state, the capacitor C is discharged.
That is, the switch of FIG. 6 is formed by a discharge state, is turned on by the occurrence of arc discharge, and is off in the glow discharge state. Figure 6
The circuit shown in the case of L / C»R _A ^2/4, resulting in free oscillation. The period T is 2π (L · C) ^1/2 .

Here, the resistance R _A of the arc discharge is generally several Ω or less, and now L = 20 μH, C = 5000 pH, R
When _{A = 10Ω, L / C =} 4000 R A 2/4 = 25 , and the said relationship L / C (= 4000) »R A 2/4
(= 25) is satisfied, and the circuit including the vacuum chamber and the charging / discharging portion shown in FIG. 6 causes free vibration. Here, the voltage due to free vibration is V. Then, the cycle T becomes 2 μsec.

FIG. 7 is a target voltage diagram in the sputtering apparatus of the present invention. The target voltage is the voltage V due to free vibration and the target voltage V _PPA during arc discharge.
Represented by the sum of. The frequency of free vibration is lower than the frequency of the high frequency power supply 11, which is the frequency of the target voltage V _PPA during arc discharge, for example, 13.56 MHz.

Therefore, a current flows in the opposite direction about half a cycle after the free vibration (1 μsec in the above example) after the arc discharge occurs and the switch of FIG. 6 is turned on. Therefore, a voltage opposite to that when the switch is turned on is applied to the resistance _RA of the arc discharge. Since the arc discharge is caused by the negative bias voltage generated in the target electrode 5, the arc discharge can be extinguished by changing the bias voltage of the target electrode from negative to 0 or positive when the arc discharge occurs.

That is, when arc discharge occurs, several μs
Since a positive bias voltage is applied to the target voltage V at about c, the arc discharge is extinguished. Since the time until the arc discharge is extinguished is about a few μsec, which is a very short time, the matching circuit 12 remains at the matching point at the time of glow discharge and the glow discharge is immediately turned on. It should be noted that the effect of inserting the charging / discharging unit 20 on the input of high-frequency power to the vacuum chamber 1 can be ignored.

[0041] That is, in FIG. 1, a high frequency power to the discharge load of the vacuum chamber 1 efficiently to supply, between the impedance Z _A of the discharge load impedance Z _B of the charging and discharging unit 20 | There must be a relationship of Z _A | << | Z _B |.

Generally, the frequency of the supplied high frequency power source is 13.56 MHz, but in this case, the impedance Z _{A of the} discharge load is about several tens Ω. here,
As an example, inductor L is 20 μH and capacitor C is 5
At 000 pF, the impedance Z _B of the charging / discharging unit 20 is | Z _B | = | 2πfL−½πfC | and | Z _B | = 1700Ω. Therefore, the above |
Since the relationship of Z _A | << | Z _B | is satisfied, most of the high frequency power is supplied to the discharge load in the vacuum chamber 1, and the influence on the circuit of the charging / discharging unit 20 can be ignored.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0044]

As described above, according to the present invention,
Since the arc discharge can be extinguished in about several μsec, high-speed film formation can be performed without deteriorating the film quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sputtering apparatus of the present invention.

FIG. 2 is a circuit diagram of a vacuum chamber and a charging / discharging unit of the present invention.

FIG. 3 is a voltage diagram of a target when glow discharge is generated in the vacuum chamber.

FIG. 4 is a voltage diagram of a target when arc discharge is generated in the vacuum chamber.

FIG. 5 is a voltage diagram of a capacitor in the charging / discharging unit of the present invention.

FIG. 6 is an equivalent circuit diagram of the vacuum chamber and the charging / discharging unit of the present invention.

FIG. 7 is a target voltage diagram in the sputtering apparatus of the present invention.

FIG. 8 is a configuration diagram illustrating a conventional high frequency sputtering apparatus.

FIG. 9 is a voltage diagram when a rectangular wave is applied.

FIG. 10 is a voltage diagram when a sine wave is applied.

FIG. 11 is a configuration diagram of a conventional sputtering apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Substrate holder, 3 ... Substrate, 4 ... Target, 5 ... Target electrode, 7 ... Insulator, 10 ... High frequency power part, 11 ... High frequency power supply, 12 ... Matching circuit, 20
... Charge / discharge part, 21 ... Inductor, 22 ... Capacitor, 3
0 ... Gas supply unit, 40 ... Gas exhaust unit

Claims (1)

[Claims] 1. A target electrode having a target in a vacuum chamber, (b) a substrate on which a film containing the target as a component is deposited, and (c) a high frequency power for applying a high frequency power to the target electrode. It comprises a power supply section, and (d) a series circuit of an inductor and a capacitor connected in parallel to the target electrode, and (e) changes the bias voltage applied to the target due to the occurrence of arc discharge on the surface of the target. A sputtering apparatus characterized by the above.