JP2006117995A - Sputtering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering apparatus which does not cause the dielectric breakdown of a substrate due to the generation of abnormal arc discharge in reverse sputtering, without using an expensive high-frequency facility. <P>SOLUTION: This sputtering apparatus comprises: an electric power source that employs a pulsed direct current; a substrate holder that is composed of a metal such as Ti and Al, which is hardly sputtered and is hardly oxidized, and that makes the metal at least in a part which faces a plasma-generating space, exposed to the space; and a changeover switch for switching a load of pulsed voltage between a side of a substrate to be treated and a target side, to easily perform reverse sputtering and regular sputtering in the same apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sputtering apparatus, and more particularly to a sputtering apparatus having a reverse sputtering function.

Sputtering technology for depositing thin films such as dielectric films, optical films, and protective films on substrates has become indispensable for the modern high-tech industry, and is widely known as a dry process with a wide range of applications. Yes. When the sputtering technique used in this sputtering technique is classified according to the type of voltage applied to the target electrode, a direct current (DC) sputtering technique and a radio frequency (RF) sputtering technique are frequently used.
Although DC sputtering using a direct current power source has a high film forming speed, there is a problem in that abnormal arc discharge occurs because charges accumulate on the target surface and an insulator or a high resistance film adheres with the lapse of time of sputtering.
In addition, although RF sputtering using a high frequency power source can form a film without abnormal discharge for a long time, there is a problem that the film forming speed is slow. However, RF sputtering technology is indispensable for sputtering an insulator.

By the way, when an electronic circuit is formed using a thin film, it is often necessary to overlay an upper conductive film on the surface of the exposed lower conductive film, but a natural oxide film or contamination inevitably generated on the surface of the lower conductive film occurs. A cleaning process to remove things is indispensable.
When an electronic device such as a transistor is formed on the surface of a silicon substrate or a liquid crystal display element is formed, a process of forming a transparent conductive film on the surface of a metal film is frequently used.
At that time, a strong oxide film is formed on the surface of the metal having a large affinity for oxygen, and when the oxide film is sputtered on the surface of the metal film on which the oxide film exists, the abnormal discharge described above occurs. The phenomenon occurs. For example, when an oxide film such as indium tin oxide (ITO) is sputter-deposited on the electrode surface made of chromium (Cr), if the chromium oxide film exists on the electrode surface, the electrical properties of the Cr film and the ITO film The contact resistance becomes high and good device characteristics cannot be obtained. Therefore, a cleaning process for removing the chemical film present on the surface of the metal film is required.

As a cleaning method, a wet etching process using an etching solution is also used, but a dry etching process using a reverse sputtering phenomenon is frequently used.
The reverse sputtering phenomenon is a phenomenon in which ions existing in the plasma space are attracted to and collide with the substrate to be processed charged to a negative potential, and eject constituent materials on the surface of the substrate to be processed. By utilizing this reverse sputtering phenomenon, a natural oxide film, contaminants, etc. on the surface of the substrate to be processed can be removed (for example, see Patent Document 1).

Incidentally, as shown in FIG. 6, the high-frequency sputtering apparatus has a complicated structure around the electrodes in order to efficiently apply power, and requires a matching box (matching circuit) for impedance matching (see, for example, Patent Document 2). ).
In the sputtering apparatus 50 shown in FIG. 6, a sputtering target 3 supported by a target susceptor 5 and a substrate 2 to be processed supported by a substrate holder 54 are arranged in a vacuum chamber 1 connected to a vacuum exhaust port. Has been. Further, a high frequency power source 56 is provided outside the vacuum chamber 1, and changeover switches SW 1 and SW 2 are connected to the high frequency power source 56, and the fixed contact a is connected to the substrate holder 54 in the vacuum chamber 1 via the matching box 58. The target susceptor 5 side is grounded, the fixed contact b is connected to the target susceptor 5 in the vacuum chamber 1 via the matching box 57, and the substrate holder 54 side is connected to ground. is there. When sputtering film formation is performed using the high-frequency sputtering apparatus 50, high-frequency power is applied to the target 3, and when reverse sputtering is performed, high-frequency power is applied to the substrate 2 to be processed.
The matching boxes 57 and 58 are for adjusting the impedance of the circuit in order to efficiently apply, for example, a high frequency power of 13.56 MHz. The matching boxes 57 and 58 calculate the impedance of each equipment and further for each circuit. Designed.
JP 2000-164666 A JP-A-11-323544

  In a high-frequency sputtering apparatus, it is essential to match the impedance of a circuit in order to efficiently apply high-frequency power. For this purpose, a matching box including an expensive matching circuit is required, and it is necessary to individually design the stray capacitance around the electrodes by calculating the stray capacitance, which makes the apparatus itself very expensive. In addition, the high frequency power supply itself is more expensive than the DC power supply. As described above, the matching box is designed for each facility by calculating the impedance for each facility and each circuit. Particularly, in a sputtering apparatus having a reverse sputtering function, two matching boxes are required as shown in FIG.

In addition, in DC sputtering equipment, when the sputtering power is increased, abnormal discharge occurs on the surface of the target material, the surface of the target susceptor, or between these and the ground shield, the surface of the substrate to be processed, or the surface of the substrate holder. End up. Such an abnormal discharge can be observed everywhere in the vacuum chamber, and when the abnormal discharge occurs, it causes a film quality defect or a product defect such as a dielectric breakdown of the substrate to be processed.
The present invention has been made in view of the above circumstances, and provides a sputtering apparatus that does not cause dielectric breakdown of a substrate due to occurrence of abnormal arc discharge during reverse sputtering without using expensive high-frequency equipment. Objective.

In order to solve the above problems, a sputtering apparatus according to the present invention holds a substrate at a predetermined position in a chamber provided with an exhaust system facility, a target placed with the surface to be sputtered exposed in the chamber. A sputtering apparatus having a sputtering power source for generating plasma between the substrate and the target, the substrate holder being made of metal and facing at least the target The metal surface is exposed to the space where the plasma is generated, and the sputtering power source is a DC pulse power source, and reverse sputtering is possible by applying a DC pulse voltage to the substrate holder. A sputtering apparatus configured as described above was obtained.
By configuring the sputtering apparatus as described above, it is possible to provide a sputtering apparatus that can perform reverse sputtering without causing arc discharge without using an expensive high-frequency power source.

The sputtering apparatus of the present invention has a changeover switch that can switch whether the DC pulse voltage is applied to the target or the substrate holder, and uses the same DC pulse power source for normal sputtering and reverse sputtering. It can be configured so that it can be done.
By configuring the sputtering apparatus as described above, sputtering film formation and reverse sputtering can be performed simply by switching the switch using the same apparatus without using an expensive high-frequency power source.

In the sputtering apparatus of the present invention, the substrate holder is preferably a substrate holder in which a surface other than the surface facing the target of the substrate holder is covered with an insulator. The insulator may be aluminum oxide. The substrate holder is preferably made of titanium.
By configuring the sputtering apparatus as described above, arc discharge does not occur during reverse sputtering, and power can be applied efficiently.

In the sputtering apparatus of the present invention, it is preferable that the substrate holder is disposed above the target.
This is to prevent the dust from falling on the substrate surface even if dust is generated during reverse sputtering.
Furthermore, the on / off cycle of the DC pulse voltage is preferably 50 to 250 kHz.
This is because the reverse sputtering is efficiently performed by effectively using the applied power.

  According to the present invention, the element surface can be reverse-sputtered without destroying the element on the substrate by using a DC pulse power supply without using an expensive matching box, and sputter deposition is performed with the same equipment. Therefore, it is possible to manufacture a high-performance element with a high yield and to manufacture at a low equipment cost.

(First embodiment)
FIG. 1 shows a schematic structure of the sputtering apparatus of the present invention. In a sputtering apparatus 10 of the present invention, a sputtering target 3 supported by a target susceptor 5 and a substrate 2 to be processed supported by a substrate holder 4 are disposed in a vacuum chamber 1 connected to a vacuum system. . Further, a DC pulse power source 6 is provided outside the vacuum chamber 1, and changeover switches SW 1 and SW 2 are connected to the DC pulse power source 6, and the fixed contact a sends the DC pulse voltage to the substrate holder 5 in the vacuum chamber 1. It is applied so that the target susceptor 5 side is grounded. The fixed contact b is connected so that a DC pulse voltage is connected to the target susceptor 5 in the vacuum chamber 1 and the substrate holder 4 side is grounded. A shutter 9 is disposed between the target substrate 2 and the target 3 to prevent particles generated during reverse sputtering from depositing on the target 3.

In the sputtering apparatus 10 as shown in FIG. 1, after connecting the vacuum system and evacuating the vacuum chamber 1 under a predetermined reduced pressure, an atmospheric gas such as argon gas is introduced to a predetermined pressure.
Thereafter, the shutter 9 between the substrate 2 to be processed and the target 3 is closed to prevent particles generated during reverse sputtering from depositing on the target 3. Next, the changeover switches SW1 and SW2 are connected to the fixed contact a side, a DC voltage from the DC pulse power supply 6 is applied to the substrate holder 4 in the vacuum chamber 1, and the target susceptor 5 side is grounded. Atmospheric gas such as argon gas is turned into plasma by the direct-current pulse voltage, and radicals of electrons, ions and atmospheric gas are generated to form a plasma region P. Then, the ions in the vacuum chamber 1 are attracted to the substrate 2 to which the negative DC voltage is applied, collide with the substrate 2 by the kinetic energy, and are formed on the surface of the substrate 2. The atoms or molecules constituting the oxide film 22 are ejected. The metal oxide film can be removed by this reverse sputtering action to clean the surface. At this time, since negative and positive potentials are periodically applied to the substrate 2 to be processed, charges are not accumulated, and abnormal arc discharge does not occur. Therefore, electrons formed on the surface of the substrate 2 to be processed The circuit 21 does not break down.

After the surface of the electronic circuit 21 is cleaned, the shutter 9 between the substrate 2 to be processed and the target 3 is opened, the changeover switches SW1 and SW2 are connected to the fixed contact b side, and the DC pulse voltage from the DC pulse power supply 6 is connected. Is applied to the target 3 and the substrate holder 4 side is grounded. Atmospheric gas such as argon gas is turned into plasma by the direct-current pulse voltage, and radicals of electrons, ions and atmospheric gas are generated to form a plasma region P. The ions in the vacuum chamber 1 are attracted to the target 3 side by a negative DC pulse voltage, collide with the target 3 with the kinetic energy, and eject atoms or molecules constituting the target. This jumps and adheres to the substrate 2 to be processed facing the target 3, and a film (not shown) made of the material of the target 3 is formed on the surface of the substrate 2 by sputtering.
If the sputtering apparatus of the present invention is used, reverse sputtering and normal sputtering (sputter deposition) can be performed using the same apparatus by simply switching the application direction of the potential with the changeover switches SW1 and SW2.

  For example, when the electronic circuit 21 made of a metal having a high affinity for oxygen such as chromium is present on the surface of the substrate 2 to be processed, a high-resistance metal oxide film 22 is formed on the surface of the electronic circuit 21. When an ITO film or the like is formed, the electrical contact resistance between the metal oxide film and the ITO film increases, and good device characteristics cannot be obtained. In such a case, if the harmful metal oxide film 22 is removed by reverse sputtering to which a DC pulse voltage is applied, a sound transparent conductive film such as ITO can be formed on the surface of the electronic circuit 21 by sputtering.

FIG. 2 shows a partial cross section of the substrate holder of the sputtering apparatus of the present invention. In the sputtering apparatus of the present invention, it is preferable that the substrate 2 to be processed is disposed above the target, and the substrate 2 to be processed and the target are opposed to each other. This is to prevent particles generated in the vacuum chamber from being deposited on the substrate surface. Accordingly, the substrate holder 4 of the sputtering apparatus of the present invention is configured to receive and place the substrate 2 to be processed in an L-shaped cross section.
The substrate holder 4 of the sputtering apparatus of the present invention is preferably made of a metal having a low sputtering rate such as titanium or aluminum. In particular, titanium is preferable because it is difficult to be sputtered and oxidized.
The surface 4a of the substrate holder 4 that is in contact with the plasma generation region P and the surface 4f that faces the substrate 2 are exposed. This is because plasma discharge is caused between the facing target when a DC voltage is applied.
In order to prevent useless plasma discharge, the other surfaces 4 b and 4 c are preferably covered with an insulator 14. As the insulator 14, for example, it is sufficient to cover it with alumina (Al ₂ O ₃ ) having a thickness of about 1 mm.
The substrate 2 to be processed need only be placed on the surface 4 e of the substrate holder 4. In the sputtering apparatus of the present invention, a potential is applied to the substrate 2 to be processed through a plasma potential, and therefore it is not so important to bring the substrate and the substrate holder into close contact as in a high-frequency sputtering apparatus that places importance on impedance.

  FIG. 3 shows the potential applied to the substrate to be processed by the sputtering apparatus of the present invention. The substrate potential in the present invention is normally-(minus) E, but periodically becomes + (plus) e. This periodic positive potential removes the electric charge staying on the substrate surface. The on-off period F of the pulse potential is 50 to 400 kHz, the time f for applying the + (plus) potential is 30 to 40% of the on-off period F, the − (minus) potential E is −200 to −400 V, + (plus) The potential e is suitably about +30 to + 40V.

(Second Embodiment)
FIG. 4 shows a schematic structure of a sputtering apparatus according to the second embodiment of the present invention.
The sputtering apparatus of the present embodiment is different from the sputtering apparatus of the first embodiment in that the surface of the substrate holder 2 other than the surface that faces the plasma generation region P is covered with an insulating material, and the plasma of the substrate 2 to be processed. This is that the entire surface opposite to the generation region P is covered with an insulating material and shielded. FIG. 5 shows an enlarged view of the vicinity of the substrate holder. An insulating plate 15 made of alumina having a thickness of 1 mm opposite to the plasma generation region P of the substrate 2 to be processed was disposed to shield the back surface of the substrate 2 to be processed.
By configuring the sputtering apparatus in this way, it is possible to prevent generation of excessive plasma and to have an advantage that input power energy can be used effectively.

Example 1
Using the sputtering apparatus shown in FIG. 1 using the substrate holder shown in FIG. 2, an ITO transparent conductive film was formed on the surface of the TFT element formed using chromium on the glass substrate. First, the glass substrate was reverse sputtered to remove the chromium oxide film on the chromium circuit surface, and then an ITO film was formed by sputtering. The reverse sputtering conditions were as follows.
Chamber pressure: 1.5 pa,
Sputtering gas: Argon 700 sccm,
Substrate dimensions: 6 inch square,
Pulse duty ratio: 40%
Pulse period: 100 kHz,
Maximum pulse potential: + 35V,
Pulse minimum potential: -300V
Input power: 200W
Reverse sputtering time: 5 minutes Normal sputtering film formation time: 3 minutes When reverse sputtering is performed under the above conditions, abnormal arc discharge does not occur during each operation, and an ITO film with good adhesion and good conductivity can be formed. did it.

(Example 2)
The sputtering apparatus shown in FIG. 4 using the insulating plate made of alumina shown in FIG. 5 is used to generate 200% DC pulse power to generate argon sputtering, and the aluminum element circuit formed on the glass substrate. After the surface aluminum oxide was cleaned by reverse sputtering, a metal titanium thin film was formed by sputtering, and it was confirmed that a good ohmic junction was formed.

It is a figure which shows an example of the sputtering device of this invention. It is a figure which shows the partial cross section of a substrate holder. It shows the potential applied to the substrate. It is a figure which shows the other example of the sputtering device of this invention. It is a figure which shows the partial cross section of the substrate holder of the sputtering device shown in FIG. It is a figure which shows an example of the conventional high frequency sputtering device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Substrate to be processed, 3 ... Target, 4, 54 ... Substrate holder, 5 ... Target susceptor, 6 ... ... DC pulse power supply, 9 ... Shutter, 10, 20, 50 ... Sputtering device, 21 ... Electronic circuit, 22 ... Metal oxide film, 14. .... Insulator, 15 ... Insulating plate, 56 ... High frequency power supply, 57, 58 ... Matching box

Claims (7)

  A chamber provided with an exhaust system facility; a target installed with a surface to be sputtered exposed in the chamber; and a substrate holder holding a substrate at a predetermined position in the chamber facing the target, the substrate A sputtering apparatus having a sputtering power source for generating plasma between the target and the substrate, wherein the substrate holder is made of metal, and at least a surface facing the target has a metal surface with respect to a space where the plasma is generated A sputtering apparatus, wherein the sputtering power source is a DC pulse power source, and reverse sputtering is possible by applying a DC pulse voltage to the substrate holder.   It has a changeover switch that can switch whether the DC pulse voltage is applied to the target or the substrate holder, and is configured to perform forward sputtering and reverse sputtering using the same DC pulse power supply. The sputtering apparatus according to claim 1, wherein   The sputtering apparatus according to claim 1, wherein a surface of the substrate holder other than a surface facing the target is covered with an insulator.   The sputtering apparatus according to any one of claims 1 to 3, wherein the insulator is aluminum oxide.   The sputtering apparatus according to any one of claims 1 to 4, wherein the substrate holder is made of titanium.   The sputtering apparatus according to claim 1, wherein the substrate holder is disposed above the target. The sputtering apparatus according to claim 1, wherein an on-off period of the DC pulse voltage is 50 to 250 kHz.

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