JPH0699804B2 - Sputtering equipment - Google Patents

Description

The present invention relates to sputtering film formation, and more particularly to a preferred sputtering method and apparatus for a conductive film for wiring in an integrated circuit having a multilayer wiring structure.

[Conventional technology]

As a conventional device, a device described in JP-A-61-117273 is known.

In recent years, miniaturization of semiconductor integrated circuits has progressed, and wiring of integrated circuits has become multi-layered. In an integrated circuit having a multilayer wiring structure, in order to connect the wiring layers to each other,
A fine hole called a through hole is formed in an insulating film (wiring interlayer film) between each wiring layer, and then the next wiring layer is formed. The sputtering method is widely used for forming the wiring layer because of its industrial convenience. However, for a fine through hole having an interlayer insulating film thickness of 1 μm and a through hole diameter of about 1 μm, it is not possible to obtain a good film formation shape capable of ensuring a good connection by the commonly used sputtering method. The above description is described in detail in Semiconductor World, October 1984, p116-p137, and refer to it.

FIG. 2 schematically shows the throwing power to a through hole by a commonly used sputtering method, with a cross section of the through hole. The first Al wiring layer 201 is formed on the substrate 200, patterned, and then the wiring interlayer insulating film layer.
205 is formed, and the through hole 203 is formed by the photoetching method. Further, a second Al wiring film 202 is formed from thereover. As the wiring film material, Al or Al alloy is the most common, and the following description will be made on Al / Al alloy. The Al wiring layer 201 and the Al wiring layer 202 are connected to each other through the through hole 203. However, the Al wiring layer 202 is not sufficiently distributed in the through hole 203 because the through hole 203 is minute. This is because the overhang 204 is formed at the peripheral edge of the opening end of the through hole 203 and the Al wiring layer 2 inside the through hole 203 is formed.
This is because the 02 film formation is hindered. The overhang 204 grows on the peripheral portion of the opening end because the sputtered particles enter the substrate at various angles.

FIG. 3 shows an apparatus related to the prior art, which is characterized by a sputtering target 301 and a substrate 302 which is a target for film formation.
A double-column filter 303 is placed in the space between and. In this example, the main surfaces of the target 301 and the substrate 302 are parallel to each other, while only the sputtered particles flying from the target 301 to the substrate 302 along the normal line to the target 301 or the substrate 302. A cylindrical filter 303 made of double girders is provided to preferentially pass through. This filter prevents sputtered particles from entering the substrate 302 from various directions, and suppresses the growth of the overhang described above.

FIG. 4 schematically shows the throwing power of the Al film thus formed to a through hole by a through hole cross section. Through hole diameter is through hole 402
Is about 1.7 μm, the through hole 404 is about 1.3 μm, and the depths of the through holes 402 and 404 are 1.3 μm. Since FIG. 4 is a test sample, a substrate simulating only a through hole shape is used. Although the film formation amount on the through hole bottom portion 401 is increased, the film formation amount on the through hole side wall 402 is small for the through hole 404 having a small diameter, and the film surface at the bottom of the through hole and the film surface at the side wall portion are small. There is a notch 403 at the intersection with and.

[Problems to be solved by the invention]

FIG. 5 shows the case where the sputtered A1 film is formed in a state where the substrate temperature at the time of film formation for solving the above-mentioned drawbacks is high, and the substrate temperature is about 400 ° C. However, the through hole 502 having a small diameter cannot be used because there is a space in the through hole. When the film is formed by raising the temperature to 350 ° C, (1) the film surface becomes uneven.

(2) The through hole opening is closed by the film while leaving a space in the through hole.

(3) When the interlayer insulating film is an organic substance, its thermal decomposition starts.

(4) In the case of an Al alloy film, precipitation of alloy components in the film becomes remarkable, and a problem occurs due to patterning by etching.

There are problems such as. Therefore, there is a limit to the application of very fine through holes only by installing the filter.

An object of the present invention is to provide a sputtering method and an apparatus therefor, which can improve the throwing power to a fine through hole and form a uniform film.

[Means for solving problems]

The present invention is a method of forming a wiring in a through hole connected to a lower layer wiring and an upper layer wiring by sputtering in an integrated circuit, by intermittently applying a negative potential to the integrated circuit, and wiring in the through hole. The sputtering method is characterized in that a film is formed by inducing plastic deformation to such an extent that the through hole is filled with the film. The present invention also provides a sputter electrode, a substrate electrode for applying an electric potential to a substrate that is a film formation target, and a third electrode provided in a space in which sputtered particles fly to reach the substrate from the sputter electrode. And a current value of sputter gas ions flowing into the substrate electrode is set to be larger than that when the third electrode is not present.

[Action]

To improve the conventional technique, positive argon ions in the discharge plasma bombard the substrate to be deposited or the aluminum film which is growing on the substrate. By this impact, aluminum atoms on the growing aluminum film can be moved into the through holes. Such sputter film formation is called a bias sputtering method. For the improvement of the throwing power of aluminum to the through hole by the bias sputtering method, see, for example, Nikkei Micro Devices September 1985, pages 73 to 76, "contact electrode formation (sputtering is limited to 1.0 μm rule)". However directional bias sputtering by the filter, the substrate is promising number mA / cm ₂ as a bias sputtering because it is shielded from the plasma that is generated on a sputter electrode
The above ion current density cannot be obtained on the substrate.

Therefore, the present invention significantly increases the substrate inflow current, and then effectively uses the ion current that can flow into the substrate to improve the throwing power, and the argon ions are evenly distributed on the substrate. The purpose of this is to allow the aluminum atoms to move easily into the through holes by making them incident. That is, first, by electrically exciting the filter, a second discharge is newly generated in the system by using the filter as the third electrode. At this time, in order to suppress the generation of the sputtering of the filter material, the filter has a cylindrical shape so that the discharge is generated at a voltage as low as possible, and the hollow cathode discharge in the filter is used. Secondly, the impact of the aluminum film during film formation by ions is effectively performed so that the movement of aluminum atoms is activated by the substrate inflow current, that is, the argon ion current, which can be increased by the above method. ,
In the sputtering apparatus according to the present invention, it is not always necessary to apply the substrate potential so as to obtain a sufficiently large current density, but it may be applied intermittently, for example. Specifically, a voltage may be applied to the substrate electrode intermittently so as to have a large negative potential. If the temperature of the board is too high, the aluminum flow will not go into the through holes effectively. In order to improve the throwing power to the through hole, it is important to suppress the overhang (which will be described in detail in the related art) that grows by closing the through hole at the periphery of the through hole. If there is any, it suffices to apply a substrate bias momentarily when the overhang grows a little and to flow the aluminum film in the overhang part. Such improvement in throwing power by intermittently applying the substrate voltage is based on the premise that the growth of the overhang is originally slow due to the directivity provided by the filter, and then the present invention can realize a large effect for the first time. it can. As a result, there is no more inflow of argon ions than necessary, and the substrate temperature will not be raised excessively. Thirdly, maintaining a uniform argon ion current density on the substrate can be achieved by moving the plasma generation position relative to the substrate and making the inflow of argon ions uniform over the substrate as a time average. With an electromagnet type magnetron sputtering electrode arranged coaxially with the center of the wafer and capable of changing the diameter of the generated plasma ring, when the diameter of the plasma ring is small, a high ion current density can be obtained in the central portion of the wafer substrate, Conversely, when the diameter of the plasma ring is large, a high ion current density can be obtained at the outer peripheral portion of the wafer substrate. The ratios of these two current densities and the film-forming rates corresponding to the two current densities obtained at the same time do not always match well. That is, if the sputtering power is changed along with the movement of the plasma ring so that the ion current density becomes uniform, the result is that a flat deposition rate distribution cannot be obtained this time. At this time, in the technique according to the present invention, by simultaneously controlling the potentials of the filters, the film formation rate distribution and the ion current density distribution can be made compatible with each other to achieve the above object. To electrically excite the filter, apply a negative direct current, or
A method of applying a high frequency through a blocking capacitor can be considered, but in any case, a negative DC potential is generated in the filter to induce a hollow cathode discharge. In order to give directivity to the sputter particles, the filter uses, for example, a cylindrical cavity formed along the direction of the substrate from the sputter electrode, or in the shape of a cross beam, and is almost perpendicular to the substrate. The incident sputtered particles are preferentially passed. If the surface of the filter is a metal surface, it forms an equipotential surface. When the cathode electrode surfaces are facing each other, the electrons existing in that space are repulsed by the negative potential of the electrodes and behave like catch balls between the facing electrode surfaces, and are in the same space. It collides with argon gas and generates a discharge at a relatively low voltage. This discharge is called a hollow cathode discharge. Hollow cathode discharge is described in detail, for example, in “Discharge Handbook” p.132-p.133 (The Institute of Electrical Engineers of Japan). By generating a strong discharge in the space inside the filter through which the sputtered particles pass, the filter functions not as an object having a shielding effect on the magnetron discharge of the main sputter electrode, but as a source of the second plasma. When a negative potential is applied to the substrate electrode, it acts so as to obtain a larger substrate inflow current than when the filter is not provided. The impact of argon ions on the substrate surface induces many crystal defects in the growing Al film and facilitates plastic deformation. At the same time, the inelastic collision of argon ions raises the surface temperature of the growing Al film, prolonging the time from the arrival of Al atoms at the substrate to the incorporation into lattice points,
It is considered that the migration (movement) on the surface of Al is effectively increased to improve the throwing power and facilitate the plastic deformation described above. The above two Al films and Al
It is considered that a film having good throwing power for the alloy film can be formed by bias sputtering. If the plastic deformation is too high, Al may not move into the through hole, but the film may be connected at the upper part of the through hole, resulting in a cover on the upper part of the through hole. is there. In order to prevent this, it is greatly advantageous that a large number of Al atoms are formed in advance in the through holes as much as possible. That is, before the Al film covers the upper part of the through hole, if the height of Al below it is sufficient, plastic deformation occurs in a form that also includes Al in the through hole, and the inside of the through hole is affected by Al. Embedded. From the above, by using a filter and electrically exciting the filter so as to perform hollow cathode discharge, good throwing power to the bottom of the through hole and a large substrate current can be obtained. Good throwing power can be obtained only by the effect. If large-scale plastic deformation occurs during film formation, the lid may be closed as described above.Therefore, if film formation is performed with small-scale plastic deformation, the inside of the through-hole may be closed before the lid is closed. Many Al atoms can be moved. In order to generate the above-mentioned small-scale plastic deformation, it is necessary to raise the substrate temperature unnecessarily and it is necessary to generate a sufficient crystal defect density. Specifically, the substrate potential is intermittently set to a large negative potential, and crystal defects sufficient for plastic deformation can be generated at that potential. In this way, a large ion current will not always flow into the substrate, and the substrate temperature does not need to be increased carelessly. In other words, while the conditions for embedding Al are narrow (the effective setting range of the substrate electrode is narrow) only with the filter and hollow cathode discharge,
The duty of the pulse may be set by intermittently applying the negative potential. Therefore, the conditions are widened, and at the same time, the above-mentioned problems caused when the substrate temperature is too high are removed. There is no emission of sputtered particles from the part of the sputtered electrode where no glowing occurs, and in a system where the sputtered electrode and the substrate are simply stationary facing each other due to the directivity of the filter, the film thickness attached to the center of the substrate is It becomes relatively small. In order to solve this, in the present invention, (1) the magnet is moved within the sputter electrode. (2) The diameter of the plasma ring is changed so that the film formation amount on the wafer after passing through the filter becomes uniform.

〔Example〕

 The present invention will be described below based on the embodiments shown in the drawings.

FIG. 1 shows a first embodiment according to the present invention.

111 is a sputter electrode, 110 is a target, 100 is a filter, 106 is a deposition shield plate, 104 is a substrate electrode, 105 is a wafer, 101 is a DC power supply for substrate bias, 102 is a voltmeter, 103
Is a substrate inflow ammeter.

93 is a blocking capacitor, 92 is a pass-type power meter, 107
Is a pulse power supply, and 91 is a 13.56 MHz high frequency power supply, and the signal of the pulse power supply 107 can be used as a modulation input.

A negative voltage is applied to the substrate electrode 104 by the DC substrate bias power supply 101, and the voltage and current are monitored by ammeters 102 and 103, respectively. DC substrate bias power supply
A pulse power supply 107 is connected to 101, and the respective voltages are superimposed and applied to the substrate electrode 104. Under the experimental conditions described below, the output of the DC substrate bias power supply 101 was always -70V. The output of the pulse power supply 107 has a peak of −100 V, and the combined output of both power supplies has a waveform as shown in FIG. 14, a repetition frequency of 50 KHz, a duty of pulse application (t ₁ / t _{2 in} FIG. 14). ) Was varied from 0% to 100%.

The substrate 105 is fixed on the substrate electrode 104. The substrate 105 is a silicon wafer with a diameter of 100 mm. The substrate 105 is the substrate electrode 10
It is fixed by metal fittings such as whammers from 4 and secures electrical contact with the aluminum film during aluminum film formation.

The distance between the substrate 105 and the end surface of the filter 100 on the substrate side is approximately 30 m.
The distance between the end surface of the filter 100 on the sputter electrode 111 side and the surface of the target was about 30 mm.

The high frequency power supply 91 'for the filter is 13.56 MHz and is applied through a matching box (not shown).

The power applied to the filter was monitored by a pass-type power meter 92.

A negative high voltage was applied to the sputtering power source (not shown), and discharge was performed at a sputtering voltage of about -V and a sputtering current of 10A. The sputter gas pressure (argon gas pressure) at this time is approximately 3.5 m.
torn.

First, an experiment when the potential of the substrate electrode is driven in a pulse will be described. At this time, the high frequency power supply for the filter 9
1'is fixed to 50w output.

The voltage waveform applied to the substrate electrode is shown in FIG. The output of the board DC power supply is always -70V, and the output of the pulse power supply has a peak value of -110V. Therefore, as shown in FIG. 14, the peak value has a pulse train waveform of −180V.

The pulse repetition period is t ₂ seconds as shown in Fig. 14,
The substrate bias voltage becomes −170 V only for t ₁ seconds out of the t ₂ seconds. The ratio of the time when the substrate bias voltage is maximum,
Let t ₁ / t ₂ be called the duty factor. As the duty factor increases from 0% to 100%, the time during which the maximum value of the substrate bias voltage is applied becomes longer.

Figure 15 shows the results of evaluating the throwing power around the through holes using this duty factor as a parameter.

With -180V substrate bias, voids remain in the through holes as shown in Fig. 13 and they cannot be embedded. However, if this voltage is applied intermittently, 0-20% of Fig. 15 will be applied.
As shown in the result of the duty factor of No. 3, no void is generated, and it can be completely embedded at the duty of 30 to 60%. When the duty factor is increased to 70% or more, a void is generated, which is equivalent to the −180V state in FIG.

As described above, it is possible to apply a slight excess of the substrate bias voltage in order to ensure the burying, and set a wide range of suitable conditions by controlling the duty factor.

Next, as a measure of surface roughness, the specular reflectance on the other side of the Al film is 40
It was measured at a wavelength of 5 μm. Fig. 16 shows the result, and the horizontal axis shows the maximum value of the substrate bias voltage. 171 is a duty factor of 100%, 172 is a duty factor of 50
%, 173 is for a duty factor of 10%. When the duty factor is 10%, voids are not generated in the embedded film formation even if the maximum value of the substrate bias voltage is -V. When the duty factor is 50%, the maximum substrate bias voltage is −18 as shown in FIG.
It is embedded at 0V. At this time, the reflectance is 60%, which is much higher than that when the duty is 100%. The reflectance when the substrate bias is −V and the duty factor is 100% is about 48% (not shown), which is a great improvement from this value.

Although not shown here, the through hole diameter is 1 μm and the depth is 1
Although there is a condition that a film can be embedded in a through hole of μm by a sputtering method in which aluminum sputtered particles have no directivity, the reflectance is about 50%. An aluminum film could not be embedded under any condition into a deeper through hole (φ1.0 × d1.3 μm).

As described above, the filter imparts directional characteristics to the sputtered particles, and a large substrate current is generated intermittently, so that the aluminum film can be formed in a fine through hole without causing a large physical defect in the aluminum film. The embedded film can be formed.

* The actual pulse repetition period is 20 μsec or 50 KHz
And

Next, a second embodiment of the present invention will be described with reference to FIG.

Reference numeral 111 is a magnetron type sputter electrode, and 110 is a target made of a sputter material attached to the sputter electrode. Sputtered particles emitted from the target 110 pass through the filter 100 and are fixed on the substrate electrode 104.
Attach to 105.

The DC substrate bias power supply 101 is connected to the substrate electrode 104. The voltage applied to the substrate electrode 104 is observed by the voltmeter 102, and the substrate bias current flowing into the substrate electrode 104 is observed by the ammeter 103.

As the filter 100, a cross beam-shaped filter as shown in the schematic view of FIG. 7 was used. The size of the cross girder has a square opening of about 9 mm × about 9 mm, and the length in the traveling direction of sputter particles is about 10 mm.
And The diameter of the entire filter is φ160 mm.

The substrate 105 is a silicon wafer having a diameter of 100 mm, and in order to investigate the throwing power of the film forming method according to the present invention, a sample having a test shape simulating a connection hole between wiring layers (hereinafter referred to as a through hole) in a multilayer wiring structure. A wafer was used. Board 105
Is fixed on the substrate electrode 104 by a metal fitting (not shown) such as a metal claw, and the Al film on the substrate 105 keeps electrical contact with the substrate electrode 104 during Al film formation.

The distance between the substrate 105 and the end surface of the filter 100 on the substrate side and the distance between the target 110 and the end surface of the filter 100 on the sputter electrode side were both about 30 mm.

A negative DC voltage was applied to the filter 100 by a DC power supply 109. The voltage applied to the filter 100 can be observed by the voltmeter 107, and the current flowing into the filter 100 can be observed by the ammeter 108. The target 110 has a diameter of 8 inches (about φ2
(00 mm) Al-1.5% Si was used.

Vacuum chamber (not shown) to operate as a sputtering device
A high vacuum (10 ^-7 to 10 ^-8 Torr by a suitable vacuum pump)
Exhaust to the table. After that, introduce argon gas and
The pressure was 3.5 mTorr.

FIG. 8 shows the substrate voltage-current characteristics obtained in the embodiment of FIG. 801 is a characteristic when the filter 100 is not used. 802, 803, and 804 are characteristics when the filter 100 is used, and the filter voltage is 0 volt for 802, −50 V for 803, and −100 V for 804. In either case, the sputter current is 10A and the sputter voltage is about 500V. All other conditions are common.

By electrically exciting the filter 100 as seen in FIG. 8, a larger substrate inflow current can be obtained than without the filter 100.

FIG. 9 is a graph for examining the throwing power of the Al film to the through hole when the potential of the filter 100 is 0 V and the potential of the substrate electrode 104 is −160V. The size of the through hole is about 1.3 μm in diameter and about 1.3 μm in depth. The temperature at the start of film formation
The film formation rate was 300 ℃ and 5000Å / min. The bias current at this time was about 180 mA. As for the throwing power, since there is film formation using a filter, there is a film formation amount on the bottom of the through hole, but a notch remains at the boundary between the bottom and the wall surface of the through hole.

FIG. 10 is a schematic diagram showing throwing power when -50 V is applied to the filter 100 and a substrate inflow current of about 1.4 A is caused to flow at the same substrate voltage (-160 V) as in FIG. The dimensions of the through holes are the same as in FIG. Unlike FIG. 9, the notch disappears and the through hole is completely filled.

FIG. 11 shows an embodiment in which the filter 100 is excited by a high frequency power supply of 13.56 MHz. The 13.56MHz power supply 91 is filtered through a matching circuit (not shown) and a blocking capacitor 93.
Connected to 100, filter 1 by pass-through wattmeter 92
The power applied to 00 can be monitored. First
The substrate voltage-current characteristics in the embodiment shown in FIG. 11 are shown in FIG. 121 is the substrate inflow current characteristic when the filter applied power is 20 W and 122 is 50 W. Sputtering voltage is 500V
The sputtering current was 10A. As in the case of the DC voltage described above, by electrically exciting the filter, a larger substrate current can be obtained as compared with the case without the filter.

9 and 10 also when the filter 100 is excited at a high frequency.
As shown in the figure, the Al film was able to be embedded in the through hole by allowing a large substrate current to flow.

As described above, in order to electrically excite the filter 100, a method in which a negative direct current is applied or a high frequency is applied through the blocking capacitor 93 can be considered. It occurs at 100 and induces a hollow cathode discharge. In the filter 100, for example, a cylindrical cavity is formed from the sputter electrode 111 along the direction of the substrate 105 in order to give directivity to the sputtered particles.

[Effects of the Invention] As described above, according to the present invention, in an integrated circuit having a multi-layered wiring structure, through holes connecting wiring layers can be finely processed without special processing such as taper or step. Since the Al film can be deposited on the through hole as it is with good revolving property, the integrated circuit can be downsized. It is possible to simplify the process.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the sputtering apparatus of the present invention,
FIG. 2 is a diagram schematically showing the throwing power to a through hole by a commonly used sputtering method by a cross section of the through hole, and FIG. 3 is a diagram showing a conventional sputtering device,
FIG. 4 is a diagram schematically showing the throwing power of an Al film formed by the apparatus shown in FIG. 3 to a through hole, and FIG. 5 is an Al film when the substrate temperature is raised. FIG. 6 is a diagram schematically showing the throwing power of the through hole to a through hole, FIG. 6 is a view showing another embodiment of the sputtering apparatus of the present invention, and FIG. 7 is a sputtering apparatus of the present invention. FIG. 8 is a diagram schematically showing a cross-shaped filter as an example of the filter used in FIG. 8, FIG. 8 is a diagram showing substrate voltage-current characteristics obtained in the embodiment shown in FIG. 6, and FIG. 9 is In the embodiment of the present invention, when the electric potential of the filter is 0 volt and the electric potential of the substrate electrode is -160 V, a schematic diagram showing the throwing power of the Al film to the through hole, FIG. 10 is a filter in the embodiment of the present invention. -50V is applied to the same substrate voltage (-160V), A schematic diagram showing throwing power when a substrate inflow current of about 1.4 A is flown, FIG. 11 is a diagram showing one embodiment of the sputtering apparatus of the present invention, and FIG. 12 is an embodiment shown in FIG. FIG. 13 is a diagram showing the substrate voltage-current characteristics of FIG. 13, FIG. 13 is a schematic diagram showing the state of film formation in the through hole of the Al film when a −180 V direct current is applied as a substrate bias in the embodiment of the present invention, FIG. FIG. 15 is a diagram showing a combined output waveform of a DC substrate bias power supply and a pulse power supply in the sputtering apparatus of the present invention, and FIG. 15 shows the throwing power to the through hole using the duty factor of the pulse power supply as a parameter in the sputtering apparatus of the present invention. Schematic diagram showing the evaluation results,
FIG. 16 is a diagram showing the relationship between the substrate bias voltage and the reflectance on the opposite side of the Al film in the sputtering apparatus of the present invention. 91 ... High-frequency power supply, 92 ... Passive power meter 93 ... Blocking capacitor 100 ... Filter 101 ... DC power supply for substrate bias 102 ... Power meter, 103 ... Substrate inflow ammeter 104 ... Substrate electrode, 105 ... Wafer 106 ... Adhesion shield plate , 107… Pulse power supply 110… Target, 111… Sputter power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kawahito Michizen, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., within the Hitachi, Ltd. Institute of Industrial Science (72) Inventor Masahiro Fujita Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 Incorporated company Hitachi, Ltd., Production Engineering Laboratory (72) Inventor Yuji Yoneoka Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture 292 Incorporated Hitachi, Ltd. Production Engineering Laboratory (72) Inventor, Kamei Tsuneaki Totsuka-ku, Yokohama, Kanagawa 292, Yoshida-cho, Ltd., Production Engineering Laboratory, Hitachi, Ltd. (56) References JP-A 61-156804 (JP, A) JP-A 61-264174 (JP, A) JP-A 58-194334 (JP, A) ) JP-A-62-99461 (JP, A)

Claims (6)

[Claims] 1. A sputtering electrode, a substrate electrode for applying a potential to a substrate which is a film formation target, and a third electrode provided in a space in which sputtered particles fly to reach the substrate from the sputtering electrode. By providing a negative potential to the third electrode constantly or intermittently, the current value of the sputter gas ions flowing into the substrate electrode can be made larger than that when the third electrode is not present. A sputtering apparatus characterized by setting so that 2. The third electrode is applied with a negative DC potential or a potential obtained by superimposing an alternating potential and a DC potential having a negative average value within a certain period of time. The sputtering apparatus according to item 1. 3. The third electrode is provided with a plurality of cylinders so that sputtered particles can pass in a direction substantially parallel to a normal line to the sputtering electrode. The sputtering apparatus according to item 1. 4. The potential applied to the substrate electrode is such that a negative DC potential or an average value within a fixed time is negative.
The sputtering apparatus according to claim 1, wherein the DC potential and the alternating potential are superposed. 5. The sputtering apparatus according to claim 4, wherein a repetition frequency of the alternating potential applied to the substrate electrode is 1 MHz or less. 6. The sputtering apparatus according to any one of claims 1 to 5, wherein the sputtering electrode is capable of moving a plasma generation place on the electrode.