Patent Application
20130213798
The present invention relates to a magnetron sputtering device, a method for controlling the magnetron sputtering device, and a film forming method.
The sputtering method is widely known as a dry process technique indispensable in film forming techniques. The sputtering method is a method for forming films in which a noble gas such as Ar gas is introduced into a vacuum container, and direct current (DC) power or radio frequency (RF) power is supplied to a cathode that includes a target, thus generating a glow discharge. The former is referred to as DC sputtering, and the latter is referred to as RF sputtering.
The sputtering method includes the magnetron sputtering method in which a magnet is disposed on the rear of a target in an electrically grounded chamber, which increases the concentration of plasma in the vicinity of the target surface, thereby allowing film forming to be conducted quickly. The magnetron sputtering method includes the RF magnetron sputtering method that uses RF power and the DC magnetron sputtering method that uses DC power, and both are used as high volume production methods for film forming.
In recent years, technical development for improving thin film characteristics is sought in film forming techniques involving magnetron sputtering. Factors that inhibit thin film characteristics when forming a film using the sputtering method include damage to the thin film due to high energy particles impacting a substrate. The energy of the high energy particles mainly results from a difference in potential that occurs on the front surface of the target, and thus, in order to attain a high quality thin film, the difference in potential needs to be made small.
An RF-DC coupled magnetron sputtering method in which sputtering is conducted by simultaneously supplying RF power and DC power to the cathode is also known. The RF-DC coupled magnetron sputtering method can control the VT (the average potential over time of the cathode surface, which is the target surface) by the voltage of the DC power source that supplies DC power. Therefore, in the RF-DC coupled magnetron sputtering method, by increasing the VT, it is possible to decrease the difference in potential on the front surface of the target, which allows a high quality thin film to be formed.
However, in the magnetron sputtering method, there is a problem that a special type of abnormal discharge (tracking arc) occurs, in which the arc rotates on parts of the target where there are zero components of the magnetic field perpendicular to the target surface (in other words, parts of the target that are etched the most). As the tracking arc occurs, the discharge impedance changes and power is not supplied efficiently to the target, which results in an undesirable situation in which the film forming speed decreases, or the film is not formed at all.
In order to deal with this, Patent Document 1 discloses a thin film forming method using the RF-DC coupled magnetron sputtering method in which an attempt is made to prevent the occurrence of tracking arcs by stopping the supply of RF power and DC power to the target simultaneously and periodically, and by shortening the amount of time in which power is supplied to less than the amount of time required for tracking arcs to occur.
Patent Document 2 discloses a technique of moving the magnet along a perpendicular direction to the target surface depending on fluctuations in magnetron discharge voltage in the magnetron sputtering method in which the magnet is moved, thus maintaining a substantially uniform discharge voltage.
The inventor of the present invention, upon conducting diligent studies of a magnetron sputtering device, has discovered that when an oscillating magnet approaches a side wall of an electrically grounded chamber, as shown in the graphs in
The method disclosed in Patent Document 1 relates to a countermeasure against arcs, and does not disclose or teach any techniques for abnormal discharge voltage due to magnet oscillation or resulting changes in film quality or uniformity in film quality. The sputtering device disclosed in Patent Document 2 has a problem that the mechanism for oscillating the magnet is very complex.
The present invention takes into consideration such issues, and an object thereof is to mitigate the occurrence of abnormal discharge voltage due to oscillations of a magnet part in a magnetron sputtering device in which the magnet part oscillates along a surface of a target part, thereby improving the quality of a thin film formed on a substrate.
In order to achieve the above-mentioned object, a magnetron sputtering device according to the present invention includes: a substrate holding part that holds a substrate; a target part disposed so as to face the substrate held by the substrate holding part; a power source that supplies power to the target part; a magnet part that is disposed on a rear side of the target part, the rear side being a side of the target part opposite to the substrate, the magnet part moving back and forth along the rear side of the target part; and a chamber with electrically grounded side walls that stores the substrate holding part, the target part, the power source, and the magnet part therein.
The magnetron sputtering device also includes a power source control part that controls the power source such that when the magnet part is away from approach points, the approach points being points respectively closest to the side walls of the chamber, a prescribed voltage is applied from the power source to the target part, and when the magnet part reaches one of the approach points, the prescribed voltage is decreased.
According to the present invention, a prescribed voltage is applied to the target part from the power source while the magnet part is away from the approach points, which are points respectively closest to the side walls of the chamber, and the prescribed voltage is decreased when the magnet part reaches one of the approach points, and thus, even when the magnet part reaches an approach point, it is possible to mitigate abnormal discharge voltage in the chamber. As a result, it is possible to greatly improve the quality of the thin film formed on the substrate.
Embodiments of the present invention will be described in detail below with reference to drawings. The present invention is not limited to the embodiments below.
As shown in
The chamber 50 is a vacuum chamber in which the side walls 51 thereof are electrically grounded. A vacuum pump not shown in the drawing is connected to the chamber 50, and the inside the chamber 50 is depressurized by the vacuum pump. The chamber 50 is also provided with a gas supply part (not shown in drawing). The gas supply part is configured to introduce Ar gas and, if necessary, O2 gas into the chamber 50, when the chamber 50 is in a vacuum state.
The substrate 10 is a glass substrate or the like of a liquid crystal display panel (not shown in drawing), for example. The substrate 10 has a vertical length of 730 mm and a horizontal length of 920 mm, for example. The substrate holding part 11 holds the substrate 10 on the lower surface thereof, and has a heater (not shown in drawing) that heats the substrate 10 when conducting film forming. Substrate masks 24 that cover outer edges of the lower surface of the substrate 10 are provided in the chamber 50.
As shown in
The targets 21 are made of a material that includes IGZO (In—Ga—ZnO4; amorphous oxide semiconductor), for example. The target part 20 is supported by target support parts 22. The target support parts 22 are made of a conductive material such as a metal, for example. The target support parts 22 are disposed on an insulating member 23. The target support parts 22 are connected to two power sources 30.
The power sources 30 are AC power sources, and as shown in
The magnet part 40 is configured to travel back and forth along the rear side of the target part 20 by a drive mechanism not shown in the drawing. As shown in
As shown in
The magnetron sputtering device 1 has a power source control part 60 that controls the output from the power sources 30. The power source control part 60 controls the power sources 30 so as to apply a prescribed voltage to the target part 20 while the magnet part 40 is away from approach points, which are points respectively closest to the side walls 51 of the chamber 50, and so as to lower the prescribed voltage when the magnet part 40 reaches an approach point.
In other words, when the magnet part 40 has not reached the position facing the left or right edge of the target part 20 and is therefore away from an approach point, then as shown in
When the magnet part 40 reaches an approach point to each side wall 51 by moving to a position facing either the left or right edge of the target part 20, then as shown in
The power source control part 60 may also stop applying voltage to the target part 20 from the power sources 30 when the magnet part 40 reaches an approach point.
—Control Method and Film Forming Method—
Next, a control method and a film forming method of the magnetron sputtering device 1 will be described.
When film forming is conducted on the substrate 10 by the magnetron sputtering device 1, first, the substrate 10, which is a glass substrate, is brought into the chamber 50 and held by the substrate holding part 11. Next, the inside of the chamber 50 is depressurized by a vacuum pump (not shown in drawing), and the substrate 10 is heated by a heater (not shown in drawing) in the substrate holding part 11. The target 21 is made of a material that includes IGZO (In—Ga—ZnO4; amorphous oxide semiconductor), for example.
Next, while maintaining a high vacuum state, a gas supply part (not shown in drawings) introduces Ar gas and, as necessary, O2 gas into the chamber 50. Then, power is supplied to the target part 20 by applying a prescribed alternating current voltage from the power sources 30, and the magnet part 40 is oscillated, thus starting film forming. The oscillation speed of the magnet part 40 is approximately 10 mm/s to 30 mm/s, for example.
The voltage applied to the target part 20 is controlled by the power source control part 60. In other words, as shown in
By generating a glow discharge between the target part 20 and a wall of the chamber 50, plasma is generated on the substrate 10 side of the target part 20. Ar that has become positively ionized due to the plasma is drawn to the target part 20. The Ar ions collide with each target 21 causing particles that constitute the target 21 to fly off and bond to the substrate 10. With this process, a film is formed on a surface of the substrate 10.
Here, when the voltage of the power sources 30 is maintained at a constant prescribed input power density as stated above, then as shown in
The abnormal discharge voltage occurs when the magnet part 40 reaches an approach point to each side wall 51 of the chamber 50. As shown in
In order to deal with this, in the present embodiment, the voltage of the power sources 30 is controlled by the power source control part 60 such that the voltage of the power sources 30 when the magnet part 40 reaches an approach point is less than the voltage when the magnet part 40 is away from an approach point. In other words, as shown in
Therefore, according to Embodiment 1, when the magnet part 40 is away from approach points, which are points respectively closest to the side walls 51 of the chamber 50, a prescribed voltage is applied to the target part 20 from the power sources 30, but when the magnet part 40 has reached an approach point, the prescribed voltage is lowered, and thus, even when the magnet part 40 has reached an approach point, it is possible to mitigate abnormal discharge voltage in the chamber 50 by appropriately decreasing the discharge voltage. As a result, it is possible to increase the uniformity of the thin film formed on the substrate 10, and to greatly improve the film quality thereof.
In Embodiment 1, the target part 20 has a plurality of targets 21 and the power sources 30 are AC power sources, whereas Embodiment 2 has a target part 20 constituted of one target, and a power source 30 is a DC power source or an RF power source.
In other words, as shown in
In the present embodiment, the target part 20 supported by the target support part 22 is constituted of one target. The magnet part 40 is disposed on the rear side of the target part 20 and has a plurality of magnets 41 that move parallel to the rear side of the target part 20. The substrate 10 has a vertical length of 404 mm and a horizontal length of 595 mm, for example.
If the power source 30 is a DC power source, when the magnet part 40 has not reached a position facing a left or right edge of the target part 20 and is away from an approach point to a side wall 51 of the chamber 50, then as shown in
On the other hand, if the magnet part 40 has reached an approach point to a side wall 51 by moving to a position facing either the left or right edge of the target part 20, then as shown in
If the power source 30 is an RF power source, when the magnet part 40 is away from an approach point, then as shown in
On the other hand, if the magnet part 40 has reached an approach point, then as shown in
—Control Method and Film Forming Method—
Next, a control method and a film forming method of the magnetron sputtering device 1 will be described.
When conducting film forming on the substrate 10 using the magnetron sputtering device 1, the substrate 10 brought into the chamber 50 is held by the substrate holding part 11, the inside of the chamber 50 is depressurized, and the substrate 10 is heated by a heater (not shown in the drawing), similar to Embodiment 1.
Next, while maintaining a high vacuum, Ar gas and, as necessary, O2 gas are introduced into the chamber 50, and the target part 20 is supplied with power by applying a prescribed direct current voltage from the power source 30, and the magnet part 40 is oscillated, thus starting film forming.
First, if the power source 30 is a DC power source, the oscillation speed of the magnet part 40 is approximately 4 mm/s to 10 mm/s, for example. The voltage applied to the target part 20 is controlled by the power source control part 60. In other words, as shown in
In this way, Ar ions are caused to collide with the target 21 by the plasma formed on the substrate 10 side of the target part 20, thus forming a film on the surface of the substrate 10.
Here, when the voltage of the power source 30 is maintained at a constant prescribed input power density as shown in
In order to deal with this, in the present embodiment, the voltage of the power source 30 is controlled by the power source control part 60 such that the voltage of the power source 30 when the magnet part 40 reaches an approach point is less than the voltage when the magnet part 40 is away from an approach point. In other words, as shown in
On the other hand, if the power source 30 is an RF power source, the oscillation speed of the magnet part 40 is set to approximately 4 mm/s to 30 mm/s, for example. The voltage applied to the target part 20 is controlled by the power source control part 60. In other words, as shown in
In this way, Ar ions are caused to collide with the target 21 by the plasma formed on the substrate 10 side of the target part 20, thus forming a film on the surface of the substrate 10.
Here, if the voltage of the power source 30 is maintained at a constant prescribed input power density as shown in
In order to deal with this, in the present embodiment, the voltage of the power source 30 is controlled by the power source control part 60 such that the voltage of the power source 30 when the magnet part 40 reaches an approach point is less than the voltage when the magnet part 40 is away from an approach point. In other words, as shown in
By controlling the voltage of the power source 30 periodically based on the position of the magnet part 40 in this way, when the magnet part 40 reaches an approach point, the discharge voltage is appropriately decreased, and the discharge voltage can be maintained at a substantially constant level.
Therefore, in Embodiment 2, as in Embodiment 1, while a prescribed voltage is applied by the power source 30 to the target part 20 when the magnet part 40 is away from an approach point, the prescribed voltage is lowered when the magnet part 40 reaches an approach point, and thus, even when the magnet part 40 reaches an approach point, it is possible to mitigate abnormal discharge voltage in the chamber 50 by appropriately lowering the discharge voltage. As a result, it is possible to increase the uniformity of the thin film formed on the substrate 10, and to greatly improve the film quality thereof.
Embodiment 3 is similar to Embodiment 2, except the magnet part 40 is constituted of one magnet 41.
In other words, as shown in
The magnet part 40 has one magnet 41, which moves back and forth between one edge and the other edge of the target part 20. The substrate 10 has a vertical length of 320 mm and a horizontal length of 400 mm, for example. The power source 30 is a DC power source or an RF power source, as in Embodiment 2.
The power source control part 60 causes a relatively large voltage to be applied to the target part 20 when the magnet part 40 is away from an approach point, as in Embodiment 2. When the magnet part 40 has reached an approach point, then the voltage is lowered as in Embodiment 2.
Here, when power source control by the power source control part 60 is not conducted, then as shown in
In order to deal with this, in Embodiment 3, when the magnet part 40 is away from an approach point, a prescribed voltage is applied from the power source 30 to the target part 20, and when the magnet part 40 reaches an approach point, the prescribed voltage is lowered, and thus, even when the magnet part 40 reaches an approach point, it is possible to appropriately decrease the discharge voltage and mitigate abnormal discharge voltage in the chamber 50, as in Embodiments 1 and 2. As a result, it is possible to increase the uniformity of the thin film formed on the substrate 10, and to greatly improve the film quality thereof.
The present invention is not limited to Embodiments 1 to 3, and includes configurations in which Embodiments 1 to 3 are appropriately combined.
As described above, the present invention is applicable to a magnetron sputtering device, a method for controlling the magnetron sputtering device, and a film forming method.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-237359 | Oct 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/005786 | 10/17/2011 | WO | 00 | 4/10/2013 |
