JP2003105537A - Sputtering apparatus and sputtering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering apparatus and a sputtering method in which arc discharge is suppressed, and plasma excellent in ionization can be fed. SOLUTION: In the sputtering apparatus having a power supply device to supply the power to a sputtering vaporization source in a pulse manner, the power supply device supplies the pulse-like discharge current in a sinusoidal half waveform, and controls the power supply so that the peak value Ip of the discharging current in the pulse and the pulse discharge time in an effective discharge generation area S on the surface of the sputtering vaporization source satisfy inequalities of T<10 μsec, and Ip/S>1A/cm<2> .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sputtering apparatus and method for forming a film on a substrate by a physical vapor deposition method.

[0002]

2. Description of the Related Art A sputtering method is a type of physical vapor deposition (PVD) method, in which an electrode provided with a coating material (target) is used as a cathode while introducing an inert gas such as Ar in a vacuum container. A glow discharge is generated, and the ions generated during the discharge are made to collide with the cathode (target) at an energy of several hundred eV corresponding to the discharge voltage, and the particles emitted by the reaction at that time are deposited on the substrate. This is a method of forming a film. This film forming process can generate stronger glow discharge by the magnetron sputtering method in which a magnetic field is applied to the target surface, and is used as a practical film forming process.

A problem often pointed out in such a sputtering method is that the formed film is not sufficiently dense because the energy of particles deposited on the substrate is small. Various methods have been proposed as a method for solving this problem. As one of the methods, discharge for film formation is performed at a very high power density in a pulsed (intermittent) manner. The technique to generate is proposed. U.S. Pat. No. 5,015,493 (hereinafter referred to as "Prior Art 1") discloses sputtering for the purpose of suppressing a temperature rise of a vacuum container and a substrate caused by sputtering glow discharge when performing sputtering film formation. A method and apparatus for intermittently performing glow discharge is described.

According to the prior art 1, a square wave DC pulse has a frequency of 0.1 to 100 kHz and a ratio of ON width and OFF width of the pulse; 1: 1 to 1: 1.00
0 voltage of each pulse; 100 V or more, preferably 200 to 8
It is said that the intended purpose can be achieved by applying the pulse width of 00V for each pulse; 10 to 10,000 μsec. Further, it is said that the square-wave DC pulse preferably has a current density of 0.1 mA / cm ^{2 to} 1 A / cm ² power density of 1 to 900 W / cm ² .

Further, WO98 / 40532 (hereinafter referred to as "prior art 2") discloses a magnetron sputtering method in which a peak power density reaches 2.8 kW. In the conventional technique 2, in magnetron sputtering, the rising edge of a pulse for applying a negative voltage to the target is made extremely steep, so that the gas in front of the target is brought into a completely ionized state very rapidly, and the It has been proposed to form a uniform plasma in the plasma and to apply a pulse that allows the gas to quickly pass through the first glow discharge state and the arc discharge state. 0.1 kW to 1 MW pulse width; 50 μs to 1 ms, more preferably 50 to 2
00 μs, preferably 100 μs pulse interval; 10 ms to 1,000 S, preferably 10
.About.50 ms pulse voltage; 0.5 to 5 kV are disclosed as preferable conditions.

Furthermore, "Suface and Coating Technology (Suface and Coating Technology
) ”, 1999 No. 122, pages 290 to 293 (hereinafter referred to as“ prior art 3 ”), peak power of 100 to
500 kW (target power density) 0.6 kW to 2.8
(corresponding to kW / cm ² ), Ar gas pressure 0.06 to 5 Pa
, A result of a film forming experiment conducted at a pulse width of 50 to 100 μs and a repetition frequency of 50 Hz is reported. In this conventional technique 3, the result that a high ion current amount of 1 A / cm ² and about 70% of the evaporated target vapor is ionized on the substrate to be film-formed is obtained.

According to this prior art 3, since the vapor used for film formation is ionized at a high rate, a high adhesion between the film and the substrate can be obtained, and a dense film can be formed. You can expect that.

[0008]

However, according to the experiments conducted by the inventors of the present application, for example, when an aluminum material is selected as the target material, the discharge is performed under the operating parameters as described in the prior art 2. When it was carried out, it was found that arc discharge frequently occurred on the target surface, and there was a problem that a large number of droplets, which are considered to be caused by arc discharge on the target, existed on the formed film formation surface. . Therefore, it is an object of the present invention to provide a sputtering apparatus and method capable of supplying plasma excellent in ionization by suppressing arc discharge in a sputtering method of intermittently supplying electric power to a sputtering evaporation source. .

[0009]

In order to achieve the above object, the present invention takes the following means. That is, a feature of the present invention is that in a sputtering apparatus provided with a power supply device for supplying electric power in a pulsed manner to a sputtering evaporation source, the power supply device provides a pulsed discharge current with a sinusoidal half-wave waveform. At the same time, the peak value Ip of the discharge current during the pulse in the effective discharge generation area (Scm ² ) on the surface of the sputter evaporation source and the pulse discharge time T are T <10 μs.
ec, Ip / S> 1 A / cm ^{2 The} point is to control the supply power.

In order to solve the above-mentioned problems, the inventors of the present application conducted an experiment under various parameter conditions in a magnetron sputtering apparatus for generating a glow discharge in a pulse shape. As a result, the discharge current peak value Ip
It has been found that when the above and the intermittent discharge time T satisfy the above conditions, it is possible to supply a plasma that is stable with less arc discharge and excellent in ionization. Another power supply device of the present invention is (Ip / S) × T <0.1 mC /
The power supply is controlled so that cm ² and Ip / S> 1 A / cm ² .

A feature of the sputtering method of the present invention is that a pulse-shaped discharge current is given in a sinusoidal half-wave waveform, and the peak of the discharge current during a pulse in the effective discharge generation area S on the surface of the sputter evaporation source. The value Ip and the pulse discharge time T are T <10 μsec, Ip / S> 1 A / c
The point is to control the supply power so that m ² becomes. Alternatively, (Ip / S) × T <0.1 mC / cm ² , Ip / S
The power supply is controlled to be> 1 A / cm ² .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a magnetron type sputtering apparatus. This sputtering apparatus has a vacuum chamber 1 and a power supply device 2 that supplies electric power to the chamber 1. A sputter evaporation source 3 and a substrate 4 are provided in the vacuum chamber 1.
The cathode of the power supply device 2 is connected to the sputter evaporation source 3, and the anode of the power supply device 2 is connected to the vacuum chamber 1.

That is, the sputter evaporation source 3 is a cathode and the vacuum chamber 1 is an anode. The cathode 3 is a magnetron type sputtering cathode having a magnet (not shown) provided on the back surface thereof. The detailed structure related to the magnetron cathode is
It is like the well-known magnetron sputter cathode,
Details are omitted in the drawing. The vacuum chamber 1 is connected to a decompression device and a gas supply device for maintaining the inside of the chamber 1 at a predetermined gas pressure, but they are not shown because they are well-known configurations. When operating the sputtering cathode 3, a discharge gas such as argon gas is supplied to the vacuum chamber 1 at a predetermined pressure (usually 0.01 to 1).
It is introduced at about Pa).

The power supply device 2 has a circuit composed of a sputtering power source 5 for generating a DC voltage, a switch element 6 (transistor), a capacitor 7, a reactor 8 and a thyristor switch 9 for generating a pulse discharge. Have. The operation of the circuit is as follows. First, a constant voltage V0 is constantly supplied from the sputtering power source 5, and then the switch element 6 is turned on for a predetermined time to charge the capacitor 7. The switch element 6 is turned off at the timing when the capacitor 7 is charged, and then the thyristor switch 9 is turned on.

When the thyristor 9 is turned on, the electric charge charged in the capacitor 7 is applied to the magnetron cathode 3 via the reactor 8 and glow discharge is generated by the discharge gas in the vacuum chamber 1. FIG. 2 shows a typical waveform of the voltage / current of glow discharge at this time. That is, after the output voltage of the sputtering power source 5 is applied for a certain period, glow discharge occurs, and a current flows in a half-wave sine wave according to the LC resonance circuit of the circuit, and at the same time, the voltage once sharply decreases and then gradually. The voltage in the range of 150 to 1,000 V is applied while decreasing.

The voltage waveform at this time may have a substantially constant waveform as shown in FIG. 2 (a), or may have a large voltage fluctuation as shown in FIG. 2 (b). The pulsed current flowing at this time is the average value of the voltage during discharge is Vs.
Then, since a current flows in the LC resonance circuit, the peak current value Ip and the pulse width T of the half-wave sine wave are
It becomes as follows. Ip = (V0-Vs) * (C / L) ^1/2 T = [pi] * (L * C) ^1/2 Now C = 10 [mu] F, L = 10 [mu] H, V0 = 1,500
If V and Vs = 500V, Ip = 1,000A, T =
It becomes 31 μsec.

Actually, since the waveform of the discharge voltage may vary as shown in FIG. 2, it is not completely the same as the calculated value, but in the circuit of FIG. 1, the charging voltage V0 and L,
Ip and T can be made variable by changing C. In the present experiment, the discharge current is a sine half-wave current due to the influence of L and C of the circuit, but the discharge current is the maximum value of the current during the pulse length during the period in which the sine half-wave current flows. (See FIG. 2). First, the conditions for forming plasma with accelerated ionization at the cathode 3 were examined.

The knowledge obtained in this experiment is that the emission color of plasma changes at a specific current value as the current supplied to the cathode 3 is increased.
Discharge gas is argon, target material (diameter 150 mm)
When is aluminum, the light emitting state changes from a pink state to a state accompanied by blue light emission. The plasma is generated substantially when the outer diameter is 120 mm and the inner diameter is 40 mm.
The area was a donut-shaped 100 cm ² area of about mm.
That is, the discharge generation area S was 100 cm ² . When the spectral analysis of the emission spectrum at this time is performed, the emission before the change in emission color is mainly the emission of neutral argon, whereas after the change, the emission from the argon ion is the main. It turned out that

Therefore, when an experiment was carried out while changing the pulse width and the pulse current, as shown in FIG.
It was found that when the discharge current of 0 A was used as a boundary, the discharge color was mainly emitted from ions. Further, when a discharge experiment was conducted with a magnet cathode 3 having a target diameter of 4 inches with a plasma generation area of about half (φ80 to φ30, S = 43 cm ² ), the same change occurred at a discharge current of 50 A or more. . From the above experiment, the glow discharge current per area where plasma is substantially generated is a necessary condition for generating highly ionized plasma, and it is 1 A during a pulse regardless of the pulse width of the power applied by the pulse.
It was determined that a power of at least / cm ² was required.

By the way, the discharge voltage at this time is 200 to 8 on average in the period during which the pulse discharge is substantially generated.
It was 00V. In the above experiment, the problem was
When the current during the pulse is increased in order to generate the highly ionized plasma, the arc discharge is transferred in the middle of the pulsed glow discharge. When an arc discharge occurs,
Arc spots are generated on the surface of the target 3, and particles that cause defects in the coating film are generated from the arc spots.

For example, when a discharge having V0 of 1,000 V is generated in a circuit with C = 10 μF and L = 50 μH, Vs is about 180 V, and the measured current waveform is T = 80 μs (calculation). Value 70 μs) Ip = 330 A (calculated value 366 A). A representative waveform at this time is shown in FIG. In this case, what was observed as a problem was that the waveform as shown in FIG. 4B had a high frequency (50 to 70 of all discharge pulses).
%). Further observation shows that
When the waveform corresponding to (b) is observed, a spot-like bright spot is observed on the surface of the target 3 and the cathode 3
The upper discharge was considered to have transitioned from glow discharge to arc discharge.

That is, in the state where the voltage waveform of FIG. 4 (b) changes in the vicinity of 200 V, it is in the glow discharge state, and it is considered that the arc discharge occurred from the time when the voltage drastically dropped. In fact, the coating film formed on the substrate 4 in such a discharge state contained a large number of droplets, which are considered to be caused by arc discharge. Such a transition to arc discharge is a probabilistic phenomenon, but when the phenomenon in which arc discharge occurs was examined, it was found that glow discharge had occurred for a certain period of time and then transitioned to arc discharge. It was found that the arc discharge could be suppressed by ending the glow discharge before the transition.

Then, the pulse width and the current are changed again, and the result of examining the frequency of arc discharge is shown in FIG. As can be seen from FIG. 5, when the pulse current is increased,
The sustain time of glow discharge without arc discharge is shortened in a substantially inversely proportional manner, and the threshold value is 0.1 mC / cm ² pulses in the product of discharge time T and discharge current density Ip / S.
It was found to be less than e. Also, the pulse width is 10 μs
In the following, it was also found that almost no arc discharge occurred.

From these results, in order to control the discharge time of glow discharge to be short, C is set to 1 in the circuit of FIG.
An experiment was conducted under the same conditions after setting μF and L to 10 μH. At this time, V0 and Vs are 1,000 V and 18
It is 0V. The calculated Ip and T at this time are 260 A and 10 μs, respectively, and the measured values are 250
A was 11 μs. As a result of conducting a discharge experiment in this state, no arc discharge-like waveform was observed during discharge, and by visual observation, only a very faint spot was observed even in the arc discharge state. However, it was found that the energy of arc discharge was weak.
Also, when the coating film was observed with an optical microscope, no conspicuous mixture of droplets was observed, and the characteristics were significantly improved.

The present invention is not limited to the one shown in the above embodiment.

[0026]

According to the present invention, arc discharge on the target surface can be prevented, glow discharge can be generated, and plasma excellent in ionization can be supplied.

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between pulsed discharge voltage and discharge current.

FIG. 3 is a graph showing changes in discharge color when the pulse width and the discharge current are changed.

FIG. 4 is a graph showing the relationship between pulsed discharge voltage and discharge current in an experiment.

FIG. 5 is a graph showing the frequency of arc discharge when the pulse width and the discharge current are changed.

[Explanation of symbols]

2 Power supply device 3 Sputter evaporation source (cathode, target)

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Claims (4)

[Claims] 1. A sputtering apparatus comprising a power supply device for supplying electric power to a sputter evaporation source in a pulsed form, wherein the power supply device supplies a pulsed discharge current with a half-sine waveform and a surface of the sputter evaporation source. Peak value Ip of the discharge current during the pulse in the effective discharge generation area S of
And the pulse discharge time T is such that the supplied power is controlled so that T <10 μsec Ip / S> 1 A / cm ² . 2. A sputtering apparatus comprising a power supply device for supplying electric power to a sputter evaporation source in a pulsed form, wherein the power supply device supplies a pulsed discharge current with a half-sine waveform and a surface of the sputter evaporation source. Peak value Ip of the discharge current during the pulse in the effective discharge generation area S of
And the pulse discharge time T is (Ip / S) × T <0.1 mC / cm ² Ip / S> 1 A / cm ^{2 The} power supply is controlled so as to control the sputtering apparatus. 3. A sputtering method for supplying electric power to a sputter evaporation source in a pulsed form, wherein a pulsed discharge current is given in a sinusoidal half-wave form, and
The power supply is controlled so that the peak value Ip of the discharge current during the pulse and the pulse discharge time T in the effective discharge generation area S on the surface of the sputter evaporation source are T <10 μsec Ip / S> 1 A / cm ^2. A sputtering method comprising: 4. A sputtering method for supplying electric power to a sputter evaporation source in a pulsed form, wherein a pulsed discharge current is given in a sinusoidal half-wave form, and
The peak value Ip of the discharge current during the pulse in the effective discharge generation area S on the surface of the sputter evaporation source and the pulse discharge time T are (Ip / S) × T <0.1 mC / cm ² Ip / S> 1A A sputtering method, characterized in that the power supply is controlled so that it becomes / cm ² .