JPH04193949A - Sputtering electrode and its cleaning method - Google Patents

Abstract

PURPOSE:To attain the cleaning of whole the face of a target by executing sputtering cleaning without generating a magnetic field on the target in a planner magnetron sputtering electrode provided an electromagnet. CONSTITUTION:To the back of a target 1, a circular cylindrical yoke 2 is provided on a central part and an annular yoke 3 is arranged st a peripheral part, and the respective yokes 2, 3 are coupled with a discoid yoke 4. Between the yokes 2, 3, a coil 5 is wound while centering around the yoke 2 to constitute an electromagnet 6. A sputtering electrode 7 is attached to a vacuum vessel 9 via insulator 8. By this constitution, after vacuum vessel 9 is evacuated to a reduced pressure, treating gas for film formation is introduced so as to reach a prescribed pressure, and a high-frequency power is supplied to the target 1 by a switch 11 and the sputtering cleaning of the target 1 is executed. In this case, the coil 5 is not energized and by generating plasma to whole the face of the target 1, the cleaning of whole the space of the target is attained and the redeposition of film forming particles, etc., to the target 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a target cleaning mechanism and method in a sputter electrode.

[Conventional technology]

Conventional sputtering electrodes generate a tunnel-shaped static magnetic field on the target surface, confining the plasma in a donut shape. For this reason, the target was constructed so that sputtering was performed and eroded only in the portion where the plasma was confined in a donut shape. Parts of the target other than this eroded region are not only not eroded, but also the film forming particles (material constituting the target) that have been sputtered and released into the gas phase are reattached. The thin film made of the redeposited film-forming particles is not the original target material itself, but contains many impurities.

For example, a target newly attached to a sputtering electrode generally has an oxidized surface or adsorbs many impurities including water. Therefore, after a new target is installed, it is a normal routine work to sputter clean the surface to remove surface impurities. However, the impurities removed in this manner re-deposit on target portions that are not sputter cleaned. Therefore, the area on the target surface where the particles have been reattached in this way is in a different state from other target parts. For example, such areas have high resistance and are prone to chassuring and swelling. As the film formation process progresses,
A local discharge occurs between the charged-up part and the anode or other target surface around the target,
This releases foreign matter onto the coated substrate. Particularly, the generation of foreign matter due to this local discharge is one of the major causes of a decrease in yield in LSI manufacturing.

[Problem to be solved by the invention]

In the above conventional technology, plasma is generated under the same magnetic field conditions both during sputter film formation and sputter cleaning, so the structure is such that the entire surface of the target cannot be cleaned, resulting in the generation of foreign particles and a reduction in the yield of LSI etc. There was a problem that lowered the

The present invention aims to clean the entire surface of a target, and further aims to provide a sputtering electrode that generates less foreign matter.

Another object of the present invention is to improve the LSI manufacturing yield in forming a wiring film by sputtering for LSI.

[Means to solve the problem]

In order to achieve the above object, 8. The magnet placed on the back surface of the target is configured with an electromagnet, and when performing sputter cleaning of the target, the electromagnet is not energized and sputter cleaning is performed without a magnetic field.

Further, in order to achieve the above object, the magnet placed on the back surface of the target is constituted by an electromagnet so as to form a magnetic field approximately perpendicular to the target surface when performing sputter cleaning of the target.

In addition, in order to achieve the above object, the magnet placed on the back surface of the target is made up of a permanent magnet, and has a mechanism that can change the distance between the permanent magnet and the target. The magnetic field on the target surface is lowered to below several tens of Gauss, which does not cause magnetron discharge.

[Effect]

If an electromagnet is placed on the back side of the target and discharge is performed without energizing the electromagnet during sputter cleaning of the target, the plasma will not be confined by the magnet and field, so plasma will be generated on the entire surface of the target and it will look like a cloud. Since the target can be sputter-cleaned immediately, there is no redeposition of film-forming particles, and local discharges on the target surface are reduced during film-forming. In particular, if sputter cleaning is performed at appropriate intervals, local discharges on the target surface can be almost completely eliminated. Thereby, it is possible to reduce foreign particles in the LSI sputtering film forming process and improve the yield of LSI.

Also, if an electromagnet is placed on the back surface of the target and a nearly perpendicular magnetic field is formed around the target during sputter cleaning of the target, plasma can be generated over the entire surface of the target in the same way as described above. exerts an equivalent effect.

In addition, in a method in which a permanent magnet is placed on the back surface of the target and the permanent magnet is moved away from the target until the magnetic flux density on the target surface drops to several tens of Gauss or less during sputter cleaning of the target, the entire surface of the target can be Plasma can be generated and has an equivalent effect.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. On the back surface of a target 1 made of a film-forming material, a cylindrical yoke 2 is arranged in the center, and an annular yoke 3 is arranged on the outer periphery, and both yokes are connected by a disk-shaped yoke 4. . A coil 5 is wound around the yoke 2 between the yokes 2 and 3 to form an electromagnet. Sputter electrode-7
- is attached to the vacuum container 9 via an insulating glass 8.

The vacuum container 9 is kept under low pressure (10
-'~10-'Pa), then the predetermined pressure (
1 to 1 O-2 Pa) is introduced.

Argon is usually used as the processing gas.

A processing gas introduction system is also not particularly illustrated. These evacuation system and processing gas introduction system may be those commonly used in conventional sputtering equipment. An anode 10 is provided around the target 1. In the figure, it is electrically connected to the inner wall of the vacuum container and has a ground potential, but it may be electrically insulated and set to a predetermined potential.

Next, the operation will be explained. When the target 1 is replaced with a new one, the oxide film, foreign matter, etc. attached to the surface are removed by sputter cleaning. At this time, the coil 5 is not energized and no magnetic field is generated so that plasma can be generated over the entire surface of the target.

Furthermore, in order to effectively remove the oxide film etc., the switch 11
to supply high frequency power to the target. With DC power, if the oxide film on the target surface is thick, it will charge up, cause abnormal discharge, and require time to stably generate plasma.

On the other hand, high frequency power does not cause abnormal discharge unlike DC power and can easily generate stable plasma. 5
(By performing sputter cleaning for 30 to 60 minutes with a power of about IOW, the entire surface of the target can be cleaned.

Next, during film formation, the coil 5 is energized by the power source 14, and plasma is confined in a donut shape on the target surface by a tunnel-like magnetic field that exits from the center of the target and enters the target again. At this time, if the target is a conductor,
The DC power supply 13 is selected by the switch 11 and DC power is applied. If the target is a nonconductor, the high frequency power source 12 is selected.

As film formation continues, the number of film forming particles flying out from the target is small because the plasma density is low in areas other than the area where the donut-shaped plasma is generated, and the number of film forming particles flying out from the vicinity of the area where the donut-shaped plasma is generated gradually increases. Some of the
Attach to the target again. The portion that re-attaches to the target continues to occlude impurities in the film due to constant film formation. Therefore, the film quality in this part is different from the material of the target itself, and abnormal discharge is likely to occur in this part. Therefore, if the sputter cleaning of the target is performed periodically, sputter film formation without abnormal discharge can be performed over a long period of time. When abnormal discharge occurs, foreign matter is generated, and in LSI manufacturing,
This foreign material causes a significant decrease in yield. Therefore, according to the present invention, it is possible to prevent a decrease in yield in the sputtering film forming process.

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

In this embodiment, two parts are arranged concentrically around the central yoke 2.
Two coils 5', 5'' are wound, and the outer yoke 3
An inner circumferential yoke 3' is further arranged between the outer coil 5' and the central yoke 2. In this embodiment, during sputter cleaning of the target, only the outer coil 5' is energized, and the inner circumferential yoke 3' is approximately perpendicular to the target surface. This magnetic field allows plasma to be generated over the entire surface of the target at low pressure (10-'' to 10-''Pa).In Example 1, since there is no magnetic field, the plasma can be easily diffused. , it may not be possible to generate plasma under low pressure.If sputter cleaning can be performed at low pressure, the load on the exhaust pump will be reduced, and for example, in the case of a storage pump such as a cryopump, the time until regeneration is required will be shortened. This has the advantage of extending the actual operating time.

During film formation, the inner coil 5' is energized to generate a magnetic field represented by lines of magnetic force that exit from the target and enter the target again on the target surface, thereby confining plasma and plasma in a donut shape.

As described above, the DC power source 13 is used when the target is a conductor, and the high frequency power source 12 is used when the target is a non-conductor.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a permanent magnet 15 is arranged on the back surface of the target 1, and the permanent magnet is configured so that the distance from the target 1 can be varied by a ball screw 16 and a gear 17.

During sputtering film formation, the permanent magnet 15 is brought close to the target, and a tunnel-like magnetic field of about 100 to 300 Gauss is generated on the target surface to cause magnetron discharge. When sputter cleaning a target, the permanent magnet 15 is moved away from the target to lower the magnetic flux density on the target surface to below several tens of Gauss, and discharge is performed. During sputter cleaning, since the target is covered with oxides and the like, it is easier to perform stable discharge by applying high frequency power.

Therefore, as in the first embodiment, it is desirable to use a switch to use high frequency power during sputter cleaning.

〔Effect of the invention〕

According to the present invention, during sputter cleaning of the target, the entire surface of the target can be sputter cleaned, thereby preventing deposition particles etc. from re-adhering to the target and providing a clean target surface suitable for film deposition. Furthermore, by periodically performing this sputter cleaning after film formation, it is possible to prevent abnormal discharge on the target surface and keep the generation of foreign matter to a low level, thereby suppressing the decrease in yield caused by the LSI sputter film formation process. can.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a sputter electrode according to an embodiment of the present invention;
FIG. 2 is a vertical cross-sectional view of a sputter electrode according to another embodiment of the present invention, and FIG. 3 is a vertical cross-sectional view of a sputter electrode according to a third embodiment of the present invention. 1...Target 2...Center yoke 3...Outer yoke 3', 3"...
・Yoke 4...Disc yoke 5.5',
5”... Coil... Electromagnet work...
...Sputter electrode 8 ...Glass
9...Vacuum vessel 10...Anode
11...Switch 15...Permanent magnet 16...Ball screw 17...
Gear 18... Rotating handle Fig. 1 Fig. 2

Claims (4)

[Claims] 1. 1. A cleaning method for sputter cleaning a target in a planar magnetron sputter electrode having at least one electromagnet, without generating a magnetic field on the target. 2. A cleaning method comprising sputter cleaning a target by generating a magnetic field substantially perpendicular to the target surface on the target surface in a planar magnetron sputtering electrode equipped with at least one electromagnet. 3. The planar magnetron sputtering electrode has a mechanism that can vary the distance between the permanent magnet target placed on the back surface of the target and the magnet, and the magnetic flux density on the target surface can be controlled in the range of 0 to 400 Gauss. Characteristic sputter electrode. 4. 4. The cleaning method according to claim 3, wherein the sputter cleaning of the target is performed by setting the magnetic flux density on the target surface to be 50 Gauss or less.