JP2002249874A - High frequency sputtering equipment and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency sputtering method which forms a high performance film having excellent performances with a relatively high speed of film forming. SOLUTION: This high frequency sputtering device using a conductive target is constituted in such a manner that a voltmeter is connected with a part which is conducted with the conductive target via a resistance of high resistance value which can exclude the influence of high frequency current for the voltmeter of the voltmeter is connected with the same via a low-pass filter which intercepts the high frequency current and is of extremely low resistance for direct current. The high frequency sputtering device which connects the voltmeter via a low-pass filter is further made by connecting a variable resistor to the low-pass filter in parallel with the voltmeter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-frequency sputtering apparatus and a high-frequency sputtering method.

[0002]

2. Description of the Related Art In a sputtering method, a rare gas such as argon, which is maintained at a low pressure, is discharged in an electric field to generate plasma, and the generated positive ions collide with a cathode (target), thereby repelling a target material to form an atomic state. This is a method of forming a thin film by depositing scattered particles such as molecules on a target substrate. In this method, as a method of generating plasma, a direct current (DC) discharge method or a high frequency (R)
F) The discharge method is used.

[0003] Among them, in the radio frequency (RF) discharge system,
A 13.56 MHz high frequency power source generally accepted by the Radio Law is used. Since the direction of the electric field changes in a very short cycle, heavy positive ions such as argon ions cannot follow the electric field fluctuation. , The electrons in the plasma move in the RF electric field and attach to the target (electrode),
And then detach. At this time, since the degree of adhesion is stronger than that of desorption, a negative DC bias potential is generated in the target with respect to the wall of the vacuum vessel grounded. As a result, almost no sputtering occurs on the side of the substrate that is grounded together with the apparatus, and positive ions are accelerated by the self-biased DC electric field and constantly collide with a target having a negative bias potential. Therefore, the self-bias potential of the cathode (target) is high frequency (RF)
In the sputtering method, it can be said that this is a very important factor. However, in the conventional high-frequency sputtering apparatus, the self-bias potential of the target is not monitored. Even though the self-bias potential is an important factor in the sputtering method, the film is formed by sputtering without determining the potential. It is currently being done.

In general, in the RF sputtering method, the negative potential due to the self-bias varies depending on the power of a high frequency power supply to be supplied. When the supplied power is increased, the value becomes more than minus one hundred volts. Usually, a self-bias of about minus several tens of volts occurs. The voltage between this potential and the ground is the accelerating voltage of argon ions, but the accelerating voltage in the RF sputtering method is a very small value compared to the fact that the discharge cannot be performed unless the normal DC sputtering method is about 200 volts or more. . This acceleration electric field accelerates argon ions and collides with the target, but when sputtering a target such as an oxide, negative ions such as oxygen are generated, and the negative ions are accelerated toward the substrate by the electric field. . Therefore, in RF sputtering, film formation can be performed with lower energy than DC sputtering, and a high-performance film can be formed in many cases. Further, the high-frequency sputtering method has a feature that discharge can be performed even when an insulating target is used, and that sputtering can be performed by electrons adhering to the surface of the target.

[0005] As described above, the RF sputtering method is a method having advantages over the DC sputtering method.
As compared with the C sputtering method, there is a drawback that the film forming speed is slow for the input power. This is considered to be because, in the DC sputtering method, the discharge is limited to the target and its vicinity, whereas in the RF sputtering method, the discharge region spreads like a radio wave and it is difficult to concentrate only on the vicinity of the target.

In the RF sputtering method, the film formation rate is increased by increasing the input power. Therefore, the input power may be increased to increase the film formation rate. However, when the input power is increased, the input power is increased. The self-bias voltage (potential difference with respect to the ground) increases, and as a result, the film changes from low-energy film formation with a relatively low bias voltage to high-energy film formation with a high bias voltage. In this case, not only does the velocity of the argon colliding with the target increase, but also negative ions (eg, oxygen) repelled from the target are greatly accelerated toward the substrate, which damages the film being formed. Cause. For this reason, in the conventional high-frequency sputtering method, if an attempt is made to increase the input power to increase the film formation rate, there is a problem that high-energy film formation is performed, sputtered particles are accelerated, and the film function is reduced. .

[0007]

SUMMARY OF THE INVENTION The main object of the present invention is to:
An object of the present invention is to provide a novel high-frequency sputtering apparatus capable of monitoring a target self-bias potential, which is an important factor in a radio-frequency (RF) sputtering method, during sputtering.

Another object of the present invention is to provide a method capable of forming a high-performance film having good film performance at a relatively high film forming rate in a high frequency sputtering method.

[0009]

The inventor of the present invention has conducted intensive studies in view of the above-mentioned problems of the prior art, and as a result, in a high-frequency sputtering apparatus using a conductive target, a portion which is electrically connected to the conductive target. Connect a voltmeter through a high-resistance resistor that can eliminate the effect of high-frequency current on the voltmeter, or connect a voltmeter through a low-pass filter that blocks high-frequency current and has very low resistance to DC. It has been found out that the connection of allows the monitoring of only the self-bias potential of the conductive target by eliminating the influence of the high-frequency current during sputtering. When a voltmeter is connected via a low-pass filter, a variable resistor is connected in parallel with the voltmeter, and the resistance of the variable resistor is adjusted, so that the conductive target is independent of the input power. The self-bias potential can be set to increase the deposition power by increasing the input power, and to simultaneously form a low-energy, high-performance film by lowering the self-bias potential. The present invention was completed here.

That is, the present invention provides the following high-frequency sputtering apparatus and high-frequency sputtering method. 1. In a high-frequency sputtering device using a conductive target, in a portion that is conductive with the conductive target,
A high-frequency sputtering device in which a voltmeter is connected via a high-resistance resistor that can eliminate the effect of high-frequency current on the voltmeter. 2. 2. The high-frequency sputtering according to item 1, wherein a voltmeter is directly connected between the high-resistance resistor and the ground, or a voltmeter and another resistor are connected in parallel between the high-resistance resistor and the ground. apparatus. 3. In a high-frequency sputtering device using a conductive target, in a portion that is conductive with the conductive target,
A high-frequency sputtering apparatus comprising: an input terminal of a low-pass filter that cuts off a high-frequency current and allows a direct current to pass with a low resistance; and a voltmeter connected between an output terminal of the low-pass filter and ground. 4. Item 4. The high-frequency sputtering device according to item 3, wherein a variable resistor is connected to the low-pass filter in parallel with the voltmeter. 5. A high-frequency sputtering method using the high-frequency sputtering apparatus according to the above item 4, wherein the sputtering is performed by adjusting the resistance value of the variable resistor and setting the self-bias potential of the target to a target potential.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A high-frequency sputtering apparatus according to the present invention is a high-frequency sputtering apparatus using a conductive target.
A device that has a structure in which a voltmeter is connected via a high-resistance resistor that can eliminate the effects of high-frequency current on the voltmeter, or a portion that conducts with the conductive target blocks high-frequency current and is extremely resistant to direct current. Is connected to an input terminal of a low-pass filter having a low resistance value, and a voltmeter is connected between an output terminal of the low-pass filter and ground.

In a normal high-frequency sputtering apparatus, the same negative potential as that of the target is generated in a portion that is electrically connected to the target. However, since a high-frequency current is superimposed on the negative potential, the self-bias potential of the target is not changed. Can not be asked.

In the high-frequency sputtering apparatus of the present invention,
Connect the voltmeter through a high-resistance resistor that can eliminate the effect of high-frequency current on the voltmeter, or connect the voltmeter to DC with a low-resistance low-pass filter for direct current. Accordingly, the voltmeter can display only the self-bias potential of the target while eliminating the influence of the high-frequency current.

The sputtering device that can be used in the present invention may be a magnetron sputtering device using a high-frequency power supply in addition to a normal high-frequency sputtering device.

In an apparatus having a structure in which a voltmeter is connected via a high-resistance resistor capable of eliminating the influence of a high-frequency current on the voltmeter, the high-resistance resistor may include a small high-frequency current entering the voltmeter. It is sufficient that the resistor has such a resistance value that the direct current voltage can be directly displayed on the voltmeter without the influence of the high-frequency current. Usually, a resistor having a resistance value of about 5 MΩ or more may be used.

In such a method of connecting an ammeter via a resistor having a high resistance value, a resistor having a high resistance value is connected to a portion conducting with a conductive target, and a voltmeter is directly connected between the resistor and ground. Alternatively, a voltmeter and another resistor may be connected in parallel between the resistor and the ground.

When a voltmeter is directly connected between the high-resistance resistor and the ground, the input impedance of the voltmeter becomes X
If the resistance value of the MΩ high-resistance resistor is YMΩ, the self-bias potential is displayed on the voltmeter as a voltage multiplied by X / (X + Y). When a voltmeter and another resistor are connected in parallel between the high-resistance resistor and the ground, the resistance of the other resistor connected in parallel with the voltmeter is considerably larger than the input impedance of the voltmeter. If the resistance value is small, the resistance value of the high resistance value is YMΩ, and if the resistance values of the other resistors connected in parallel with the voltmeter are ZMΩ, the self-bias potential is approximately Z / (Y + Z) times. Is displayed on the voltmeter.

In an apparatus having a structure in which a high frequency current is cut off and a voltmeter is connected to a direct current via a low-resistance low-pass filter, the low-pass filter may be, for example, a choke coil as shown in FIG. The current is cut off, the high-frequency current passing therethrough is released to the ground by a capacitor, and a DC circuit having a low resistance value of about several ohms or less can be used.

The low-pass filter may be connected to a portion that conducts with the conductive target in the high-frequency sputtering device. For example, an electron current flows into a blocking capacitor connected to the target and is charged. Since this occurs, a low-pass filter may be connected to this part. Connect the low-pass filter so that the high-frequency current does not attenuate.
For example, it is preferable to use a coaxial cable or the like for a high-frequency current.

If a voltmeter is connected to the low-pass filter connected in this way and the other end of the voltmeter is grounded, the influence of the high-frequency current is eliminated, and the self-bias potential of the target is applied to the voltmeter. Can be displayed.

As described above, a voltmeter is connected through a resistor having a high resistance value capable of eliminating the influence of a high-frequency current on the voltmeter, or a low-resistance low-pass filter for DC is provided by cutting off the high-frequency current. By connecting a voltmeter via the helium, it becomes possible to monitor the self-bias potential of the target, which is an important factor in the high frequency sputtering method, during sputtering.

In the high-frequency sputtering apparatus according to the present invention, in the apparatus having a structure in which a voltmeter is connected via the above-mentioned low-pass filter, a variable resistor is further connected to the low-pass filter so as to be in parallel with the voltmeter. In this case, by adjusting the resistance value of the variable resistor, the self-bias potential of the target generated during the high-frequency sputtering can be set to an arbitrary potential according to the purpose of film formation within a range from the potential to the vicinity of the ground potential. It becomes possible to adjust to. This variable resistor is cut off from the high-frequency power supply by being connected via a low-pass filter, so that the matching does not change by adjusting the resistance value, and the self-bias potential of the target is not affected without affecting the discharge state. Can only be changed.

A switch may be connected between the variable resistor and the low-pass filter, and the variable resistor may be connected to the low-pass filter only when necessary.

By using the high-frequency sputtering apparatus having such a structure, the self-bias potential of the target can be set low even when the deposition rate is increased by increasing the input voltage of the high-frequency power supply. Acceleration of sputtered particles ejected from the target is reduced, and a film can be formed at a low particle velocity.

In the sputtering method using such a sputtering apparatus, a high-functional film can be formed even at a low temperature by forming a film at a low particle speed without greatly lowering the film forming rate. This is presumed to be due to the following reasons.

That is, in the above method, by adjusting the self-bias potential to be low, it is possible to form a film at a low speed with sputtered particles. On the other hand, since the adjustment of the self-bias potential does not affect the high-frequency current used for the discharge, if the input power of the high-frequency power supply is set to be large, the number of active particles generated by the discharge increases. As a result, even if the sputtered particles are low in speed, the film formation rate does not significantly decrease, and the plasma density is high, and low-energy film formation can be performed. .

For example, when the high-frequency power is 80 W and the self-bias voltage is 60 V, if the input power is increased to 100 W, the self-bias voltage becomes 60 V or more, and the sputtered particles are greatly accelerated and remain at high speed. When the self-bias voltage is reduced to 60 V using a variable resistor while the input power is kept at 100 W, the speed of the sputtered particles is reduced to the same speed as when the power is 80 W. It is possible to form a high-performance film with low-speed particles. In this case, 1
Since the discharge is performed at 00 W, the number of active particles is increased as compared with the case where the discharge is performed at 80 W, and the deposition rate is increased more than when the power is 80 W and the self-bias voltage is 60 V.

When sputtering is performed using the sputtering apparatus of the present invention, the self-bias potential is monitored by a voltmeter during sputtering, and the resistance of the variable resistor is adjusted according to the purpose of film formation. Is set, the shutter of the sputtering apparatus is opened, and a film is formed on the substrate. At this time, if the bias potential changes when the shutter is opened, the resistance value may be adjusted and reset to the necessary self-bias potential. The bias potential can be lowered to a value close to the ground potential by setting the resistance value of the variable resistor to a low value. Since the speed becomes slow, an appropriate self-bias potential may be appropriately determined according to the purpose from such a viewpoint.

[0029]

According to the high frequency sputtering apparatus of the present invention having a structure in which a voltmeter is connected to a conductive portion with a target through a resistor having a high resistance value or a voltmeter is connected through a low-pass filter. The self-bias potential of the target, which is an important factor in the high frequency sputtering method, can be monitored during sputtering.

In a device having a structure in which a voltmeter is connected via a low-pass filter, the self-bias potential of the target can be freely set to a potential according to the purpose by connecting a variable resistance value in parallel with the voltmeter. be able to.
As a result, high power can be applied to increase the density of the plasma, and at the same time, the bias potential can be lowered to form a low energy film, so that a highly functional film can be formed at a relatively high film forming speed. .

[0031]

Embodiment 1 Hereinafter, a sputtering apparatus according to the present invention will be described with reference to FIG. 2, which is a schematic view showing a cross-sectional structure of the sputtering apparatus.

The apparatus shown in FIG. 2 is a planar type magnetron sputtering apparatus. The inside of the dotted line is a chamber portion, and the entire inside of the dotted line is placed in high-purity argon gas.

The target is a disk-shaped high-density ITO target. High frequency power (13.56
MHz), the target is connected to a blocking capacitor outside (in the atmosphere) outside the chamber (atmosphere), and the blocking capacitor further includes a matching circuit necessary for discharging argon by a high-frequency current. Connected to a radio frequency (RF) power supply.

A low-pass filter is connected to the target side of the blocking condenser using a coaxial cable for RF so that RF is not attenuated. A voltmeter (volt meter) is connected to the low-pass filter,
The other end of the voltmeter is grounded. During sputtering, the voltmeter indicates the self-bias potential of the target.

A variable resistor is connected to a low-pass filter via a switch so as to be in parallel with the voltmeter, and the other end of the variable resistor is grounded.

In the sputtering apparatus having such a structure,
By adjusting the resistance value of the variable resistor during sputtering, the self-bias potential of the target can be adjusted, and the self-bias potential can be confirmed by a voltmeter.

Example 2 Using a high-purity argon gas containing 0.03% high-purity oxygen as a discharge gas, a low-resistance IT was prepared in the following manner.
An O film was produced.

Using the apparatus shown in FIG. 2 as a sputtering apparatus, oxygen gas and argon gas were flowed until the pressure reached 1.9 Pa while watching the vacuum gauge while evacuating the chamber with a molecular pump.

As a target, a commercially available disk-shaped high density I
Using a TO target (diameter 100 mm x thickness 5 mm), target-substrate (non-alkali glass 76 x 26)
mm ² , 3 mm thick) and 85 mm between
At a substrate temperature of 0 ° C., discharge was performed at RF 120 W to form an ITO film on the substrate. The self-bias potential generated at this time was −83 V, the film formation rate was 95 ° / min, and the specific resistance of the film was 4.5 × 10 ⁻⁴ Ωcm.

Under the same film forming conditions, when the resistance value of the variable resistor is adjusted and only the self-bias is set to -65 V, the specific resistance of the film becomes 2.7 × 10 ⁻⁴ Ωcm, and the low resistance value becomes low. Was formed. The deposition rate dropped slightly to 77 ° / min, but this was the same as the self-bias -65.
The film formation speed was remarkably faster than the film formation rate of 36 ° / min in the case of RF 70 W generating V.

Incidentally, RF 70 W, self-bias potential -65
The specific resistance of the film formed at V is 2.5 × 10 ⁻⁴ Ωcm, and at RF 120 W, only the self-bias potential is −65 V
It was confirmed that an ITO film having a low resistance value of the same level can be formed even when the film thickness is adjusted to.

Example 3 Using the same sputtering apparatus as in Example 2, the entire heating plate of the substrate was lifted up with an insulator, and the distance between the target and the substrate was 92%.
mm, and the heating plate was grounded. The pressure of argon containing 0.03% of oxygen was set to 1.3 Pa, and the other film-forming conditions were the same as in Example 2, and a high-frequency power of 120 W was applied to discharge and an ITO film was formed by sputtering. . In this case, the self-bias was -88 V, and an ITO film having a film formation rate of 97 ° / min and a specific resistance of 2.2 × 10 ⁻⁴ Ωcm was formed.

Next, when the film was formed under the same film forming conditions by adjusting only the self-bias to -65 V, the specific resistance of the film was 1.9 × 10 ⁻⁴ Ωcm, and the resistance could be reduced. The film forming rate was slightly reduced to 68 ° / min, which was much higher than the film forming rate of 36 ° / min of RF70W generating the same self-bias of -65V.

Embodiment 4 The same as in Embodiment 3 above, using a sputtering apparatus, changing the pressure of argon containing 0.03% of oxygen to 0.95 Pa, applying a high frequency power of 120 W to discharge, and performing sputtering. An ITO film was formed. At this time, the self-bias potential is -84 V, and the film forming speed is 92 ° /
The specific resistance was 3.0 × 10 ⁻⁴ Ωcm.

Next, when the film was formed under the same film forming conditions while adjusting only the self-bias to -65 V, the specific resistance of the film became 2.6 × 10 ⁻⁴ Ωcm, and the resistance could be reduced. The film forming rate was slightly reduced to 66 ° / min, which was much higher than the RF 70 W film generating rate of 36 ° / min which generates the same self-bias of -65V. As is clear from the above results, in Examples 2 to 4, the RF
When a self-bias voltage of 80 V or more generated during discharge at 120 W is reduced to 65 V and a film is formed on a glass substrate at 200 ° C., the specific resistance of the formed ITO film can be reduced, and the film forming speed can be reduced. The drop was very small.
In these examples, the results are shown for an ITO film having a thickness of about 1000 ° formed when the film formation time is set to 15 minutes.
It is considered that the specific resistance is further reduced when the thickness of the film is increased. Example 5 In an apparatus having the same structure as the sputtering apparatus shown in FIG. 2, instead of connecting a voltmeter via a low-pass filter to a portion connected to the target, a 10 MΩ resistor was connected to a portion connected to the target. Further, a 200 kΩ resistor and a normal digital DC voltmeter (input impedance 6 MΩ) were connected in parallel between the resistor and the ground.

The pressure of argon containing 0.03% of oxygen was set to 1.0 Pa, a high frequency power of 150 W was applied to discharge, and an ITO film was formed by sputtering.

At this time, the voltage indicated by the voltmeter was -2 V. In the above-described apparatus, the voltmeter shows that the self-bias potential is about 1/51 times (that is, 200 kΩ / (200 kΩ + 1).
0MΩ) = 1/51), which proved that the self-bias potential was actually -102 V during sputtering.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a low-pass filter circuit.

FIG. 2 is a schematic view of a cross section of a high-frequency sputtering device.

Claims (5)

[Claims] In a high-frequency sputtering apparatus using a conductive target, a voltmeter is connected to a portion electrically connected to the conductive target via a high-resistance resistor capable of eliminating the influence of a high-frequency current on the voltmeter. RF sputtering equipment. 2. A voltmeter is directly connected between the high-resistance resistor and ground, or a voltmeter and another resistor are connected in parallel between the high-resistance resistor and ground. The high-frequency sputtering device according to 1. 3. A high-frequency sputtering apparatus using a conductive target, wherein an input terminal of a low-pass filter that cuts off a high-frequency current and allows a direct current to pass with a low resistance is connected to a portion that conducts with the conductive target. A high-frequency sputtering device with a voltmeter connected between the output terminal of the filter and ground. 4. The high-frequency sputtering apparatus according to claim 3, wherein a variable resistor is connected to the low-pass filter in parallel with the voltmeter. 5. A sputtering method according to claim 4, wherein the sputtering is performed by adjusting the resistance value of the variable resistor and setting the self-bias potential of the target to a target potential. High frequency sputtering method.