JP2000256846A - Dc magnetron sputtering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the incident of the high-velocity electrons generated at the end of electric discharge on a substrate and to prevent the electrification of the substrate by connecting a third electrode in addition to an anode and cathode via a resistance element to a DC power source holding a positive potential from the anode. SOLUTION: A lead wire 27 is mounted at a mask 22 forming the anode and is electrically connected to the atmosphere side through a current introducing terminal 24 and is connected to a DC power source 26. At this time, the resistance element 25 is mounted as well. The DC power source 26 is maintained at the positive potential to a grounding shield 16 and an anti-deposition plate and forms an electric field for absorbing the high-velocity electrons into the mask 22 between a target 14 and the mask 22. The resistance element 25 prevents the inflow of a large quantity of the electrons generated by magnetron into the DC power source 26. The resistance element 25 maintains the potential of the mask 22 nearly similarly to the case the potential of the mask 22 is made floating at the time of magnetron discharge and, on the other hand, plays the role of absorbing the high-velocity electrons by maintaining the potential of the mask 22 at the positive potential when the discharge current diminishes at the end of the discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron sputtering apparatus for forming a thin film on a large-area substrate by a magnetron sputtering method, and more particularly to a method for preventing an insulating substrate from being charged.

[0002]

2. Description of the Related Art A magnetron sputtering apparatus is one of thin film forming apparatuses used in the field of manufacturing electronic components such as semiconductors, liquid crystal display elements, magnetic heads and magnetic disks. In the field of liquid crystal display devices, TFT-LCDs (Thin Film Tran
In the manufacture of sistor-liquid crystal displays (liquid crystal display elements using thin film transistors), they are used for forming signal electrodes and pixel electrodes.

[0003] Two types of magnetron sputtering apparatuses are mainly used depending on the type of substrate transport. One is an inline type in which a film is formed while continuously transporting several substrates. This is a single-wafer type in which the film is transferred to a processing chamber and a film is formed while the substrate is fixed. TFT-LCD
In the TFT array manufacturing process in the manufacturing, the latter single-wafer sputtering apparatus is often used.

[0004] The flow of a film forming process in a single-wafer sputtering apparatus will be described. First, a substrate is carried into a film formation chamber, and the substrate is placed on a heater. After a discharge gas such as argon is introduced and the heater is moved to move the substrate to a predetermined position, a negative voltage is applied to the vacuum container to the sputter target to start magnetron discharge. The magnetron discharge is a high-density plasma region formed in a racetrack shape in a tunnel-shaped magnetic field formed on the target surface by a magnet installed on the back surface of the target.

[0005] A large amount of positively charged argon ions are present in high-density plasma, and are accelerated toward a target having a negative voltage. When the argon ions collide with the target, the material that makes up the target is repelled by the impact and deposits on the substrate. Thus, a thin film is formed on the substrate.

In order to form a film over the entire surface of the substrate,
It is necessary to move the high-density plasma area in the shape of a race track, and therefore the magnet is moved. The high-density plasma region moves following the position of the magnet. When a predetermined film thickness is formed on the entire surface of the substrate, the discharge is stopped, the gas introduction is stopped, and the substrate is taken out.

As described above, it is necessary to start and stop the discharge in the film forming process. The problem here is the high-speed electrons generated when the discharge is stopped. The reason why high-speed electrons are generated when the discharge is stopped is as follows. As the discharge current is reduced, insulation is rapidly restored, and a current cutting phenomenon in which the discharge current suddenly becomes zero occurs. This is more remarkable as the discharge gas pressure is lower, that is, the higher the vacuum. Further, since the power cable has an inductance component, a surge voltage is generated in the target when current cutting occurs. The electrons are accelerated at high speed by the surge voltage.

In a vacuum vessel, there is a glass substrate on which a film is to be formed. Since this is an insulator, the glass substrate is charged when electrons are incident. When the glass substrate is charged, an electric suction force acts between the glass substrate and the heater, making it difficult to separate the substrate from the heater. Further, even if the charge amount is small and the substrate can be separated from the heater, the substrate remains slightly charged when the substrate is taken out of the vacuum into the atmosphere. When returning the substrate from vacuum to atmosphere,
In some pressure regions, the insulating property is low, so that a certain amount of charge is neutralized but remains without being completely neutralized. Transporting a charged glass substrate in the air results in attracting particles. Particles adhering to the substrate cause a reduction in yield, and handling of a charged substrate causes a reduction in product yield.

A DC magnetron sputtering apparatus usually uses a target as a cathode and a substrate as an anode. However, when an insulator such as a glass substrate is formed, a direct current does not flow through the substrate, so that an anode needs to be provided around the substrate. If there is an anode around the substrate, high-speed electrons are incident on the anode, so that the charge amount of the substrate is small. However, as a method for improving the uniformity of the film thickness distribution and the film quality distribution, for example, JP-A-7-3
As shown in the embodiment described in Japanese Patent Publication No. 10181, there is a method of electrically floating members around a substrate. In the embodiment described in JP-A-7-310181, there is almost no charging because the anode is located just outside the electrically floating member, but when the anode is separated, the floating member and the substrate are May be charged.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent high-speed electrons generated at the end of discharge from being incident on a substrate in order to prevent the substrate from being charged.

[0011]

The above object is attained by extracting high-speed electrons at the end of discharge from the third electrode. Specifically, there are a method of connecting a power supply for applying a positive voltage to the third electrode via a resistor, and a method of simply connecting the third electrode to a place at the same potential as the anode via a resistor.

That is, when a positive power supply is connected to the third electrode via a resistor, high-speed electrons are absorbed by the third electrode at the same time as the end of discharge. In addition, even when the third electrode is connected to the same potential as the anode via a resistor, the effect is small but somewhat.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1)
The first example will be described. FIG. 1 is a diagram showing a cross section of an example in which a single-wafer sputtering apparatus is applied to a magnetron cathode. The substrate 12 is set on a heater 13 in a vacuum vessel 11. The target 14 is located at a position facing the substrate 12 and is bonded to the backing plate 15. The backing plate 15 plays a role of cooling the target 14 and a role of a partition for keeping the target 14 in a vacuum. A magnet 18 is arranged on the back surface of the backing plate 15, that is, on the atmosphere side. Vacuum container 11
Argon gas is introduced into the vessel and maintained at about 0.7 Pa,
When the target is set to a negative potential with respect to the vacuum vessel 11 by the DC power supply 19, the magnet 18 on the surface of the target 14
High density plasma is generated in the vicinity.

The magnet 18 forms a tunnel-like magnetic field on the vacuum side of the target 14, and electrons are trapped by the magnetic field, so that high-density plasma is generated. The high-density plasma contains a large amount of positively charged argon ions, which collide with the target 14 and sputter the target 14. This method is generally called a magnetron sputtering method. Magnet 18
Is designed to be able to move in the atmosphere.
When 8 is moved, the high-density plasma region also moves. That is, by moving the magnet 18, even when the substrate 12 has a large area, a film can be formed over the entire surface of the substrate 12. The deposition-preventing plate 22 and the mask 22 are for attaching sputtered particles flying to other than the substrate 12, and are members to be replaced immediately before the deposited film becomes thick and peels off.

The target 14 is a cathode, and emits secondary electrons at the same time as being sputtered by argon ions.
The secondary electrons need to be incident on the anode after ionizing the argon gas. That is, a DC discharge is formed by flowing an electron current from the cathode to the anode. Since the substrate 12 is an insulator and cannot pass a DC current, the ground shield 16,
It is necessary to use the deposition-preventing plate 17, the mask 22, and the like as anodes.
Since the mask 22 faces the target 14, it is considered that the mask 22 is easy to be used as an anode.
It was found that the film thickness distribution and film quality distribution were not good.

This is because, when the mask 22 is used as an anode, electrons flow into the mask 22 at a location near the substrate to increase the current density and locally increase the plasma density. Therefore, the mask 22 is not used as an anode but is electrically set at a floating potential via the insulator 23. As a result, the potential of the mask 22 was made close to that of the substrate 12, and the film thickness distribution and film quality distribution on the substrate 12 could be improved. The anode was only the earth shield 16 and the deposition preventing plate 17. Since the mask 22 has a floating potential, it is charged when high-speed electrons are incident.
The same applies to the substrate 12.

Therefore, the inventors attached a lead wire 27 to the mask 22, electrically connected to the atmosphere side via the current introduction terminal 24, and connected to the DC power supply 26. that time,
The resistance element 25 was also attached. The DC power supply 26 was set at a positive potential with respect to the earth shield 16 and the shield plate 17. The reason why the mask 22 is set to the positive potential is that an electric field for absorbing high-speed electrons into the mask 22 is formed between the target 14 and the mask 22.

The resistance element 25 is for preventing a large amount of electrons generated by the magnetron discharge from flowing into the DC power supply 26. The role of the resistive element 25 is important. At the time of magnetron discharge, the potential of the mask 22 is made almost the same as when floating, while when the discharge current becomes small at the end of discharge, the potential of the mask 22 becomes positive and the high-speed electrons are absorbed. Play a role.

(Embodiment 2) FIG. 2 shows a second embodiment of the present invention.
Shown in This embodiment is of a type in which the DC power supply 26 in FIG. 1 of the first embodiment is short-circuited.

[0020]

The effect of the present invention will be described with reference to FIG. To stop the discharge when the film formation is completed,
The current 30 decreases over time. At this time, the mask voltage was 31 when the conventional technique was not implemented. That is, when the current approaches zero, the voltage becomes higher than that of the high-speed electron incidence. This voltage peak is an amount determined by the amount of high-speed electrons and the capacitance of the mask. After the peak voltage, the voltage 31 drops according to the time constant of the capacitance and the insulation resistance of the mask.

When the first embodiment of the present invention is applied, the voltage is 32 and the mask 22 does not become a negative voltage. Further, when the second embodiment of the present invention is applied, the voltage 33 is obtained, and the peak of the negative voltage is greatly reduced. As a result, the amount of charge on the substrate is reduced as compared with the related art, and the adsorption on the mask and the adhesion of particles can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a DC magnetron sputtering apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a DC magnetron sputtering apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between time and current / voltage showing the effect of the present invention.

FIG. 4 is a sectional view showing an example of a conventional DC magnetron sputtering apparatus.

[Explanation of symbols]

11: vacuum container, 12: substrate, 13: heater, 14: target, 15: backing plate.

Claims (2)

[Claims] 1. A vacuum vessel having a substrate disposed therein, a target made of a base material to be formed into a thin film, a magnet section for forming a desired magnetron magnetic field on the surface of the target, and a DC voltage applied to the target. In the magnetron sputtering apparatus having a third electrode, in addition to a DC power supply for generating a discharge on the surface of the target and applying a discharge current for maintaining a discharge in the vacuum vessel, a third electrode. A DC magnetron sputtering apparatus, wherein the three electrodes are connected to a DC power source that holds a positive potential from an anode via a resistance element. 2. The DC magnetron sputtering apparatus according to claim 1, wherein the third electrode is connected to the same potential as the anode via a resistance element.