Process and system for operating magnetron discharges

Details Process and system for operating magnetron discharges Process and system for operating magnetron discharges

1999-07-22

2002-01-22

Nguyen, Nam (Department: 1753)

Chemistry: electrical and wave energy

Processes and products

Coating, forming or etching by sputtering

C204S289000, C204S298260, C204S298080

Reexamination Certificate

active

06340416

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process and an associated system for operating magnetron discharges. Magnetron discharges are used widely in vacuum coating technology. The most important field of application is magnetron atomization, also called sputtering, for depositing thin layers of metals, alloys, or reactively deposited chemical compounds, such as oxides or nitrides. Furthermore, magnetron discharges are used to generate the plasma in plasma-activated reactive vaporization. Another field of application is the generation of magnetron enhanced plasmas for the pretreatment of substrates before the vacuum coating. Important fields of application are the manufacture of optically effective layers in the glass industry, the manufacture of decorative, wear-reducing and hard layers in the tool industry and the machine construction industry, the manufacture of barrier layers in the packaging industry, and the manufacture of insulating layers for electronics and for data storage mediums.
2. Discussion of Background Information
The use of magnetron discharges in sputter processes for depositing conductive layers with good electrical conductivity is reliably controlled on a technical scale. Electrically insulating layers can be deposited by using high frequency sputtering. Because of numerous disadvantages, however, this process has only been used on a limited technical scale. With the reactive deposition of electrically insulating layers using direct current sputtering of metallic targets in a gas mixture which, in addition to inert gas, also contains amounts of reactive gasses such as oxygen or nitrogen, two fundamental difficulties arise. One difficulty is the lack of long-term stability of the discharge. By depositing insulating layers in the entire processing chamber, the electrode surfaces functioning as anodes also become coated so that the impedance of the magnetron discharge increases constantly with increasing processing time. This leads to a lack of constancy in the process parameters so that the discharge finally can no longer be ignited or so that the technical parameter limits of the power supply device no longer suffice. The second difficulty is the occurrence of arc discharges, which are called “Arcing” and which sometimes also occur when operating nonreactive magnetron discharges. This phenomenon is caused by electrical charging of insulating layers on the targets that are connected as cathodes. As a result of these charges, electrical short circuits in the form of above-mentioned arc discharges occur, which cause defects in the layers and on the target surface and inhibit a sufficient process stability. This is particularly true for reactive magnetron discharges.
It is to known, e.g., from German Patent Application No. 42 23 505, to significantly delay the coating of the anode by using a suitable geometric embodiment. As a result, the long-term stability of the magnetron discharges is improved and the usable processing time is extended, but the problem remains fundamentally unsolved.
In order to prevent the effects of “arcing”, a number of passive and active wirings of magnetron discharge devices are known. It is furthermore known, e.g., from German Patent Application Nos. 37 00 633 and 42 23 505, to supply electrical glow discharges or magnetron discharges with pulsed direct current. As a result, the energy content of arc discharges that occur is limited and the production of arc discharges is prevented. Various circuits have been proposed, see, e.g., German Patent Application Nos. 41 27 317; 41 27 504; 42 39 218; 42 30 779; and International Application No. PCT/US93/12604, which was published as International Publication No. WO/94/16458, and which, in addition to the pulsed supply of direct current, also generate a slight countervoltage. Processes and devices of this kind have proven useful preferably for nonreactive sputtering of electrically conductive materials in inert gas or for low-reactive sputtering. The occurrence of high-energy arc discharges can therefore be effectively prevented. However, highly insulating layers cannot be deposited in a stable fashion in this manner and the problem of the coating of the electrode surfaces acting as anodes also remains unsolved.
It is furthermore known, e.g., from German Patent Application Nos. 252 205 and 38 02 852, to use devices with two magnetron sources for the reactive deposition of thin layers, which devices are operated with a potential-free alternating current and with which the targets function alternatingly as cathodes and anodes of the magnetron discharge. As a result, the long-term stability of the magnetron discharge is achieved, even in gas mixtures that contain amounts of reactive gasses in addition to inert gas. The range from approximately 10 kHz to approximately 150 kHz has turned out to be the most suitable frequency of alternating current. Sinusoidal or rectangular voltages are used.
Through particular wirings of magnetron discharges, e.g., LC combinations, the danger of producing arc discharges can be further -reduced, e.g., as disclosed in U.S. Pat. No. 5,303,139, and German Patent Application Nos. 41 38 793 and 42 04 999. The optimal dimensioning of such wirings, however, turns out to be extremely difficult in practice since the dimensioning of the components depends on the frequency and the impedance of the magnetron discharge. Each parameter change of the discharges, e.g., changes in the target material, the pressure, the gas composition, etc., requires a change or adaptation of the wiring. Even when all of the parameters remain constant, the impedance of the discharge in each pulse changes from the ignition phase to the burning phase so that the possibility for optimization of the wiring is fundamentally limited. As a result of this, only quantitative improvements are achieved by the proposed solution strategies. The energy of arcs that occur comes into play as energy loss in the components of the wiring.
In order to optimally adapt the power supply device to various impedances of the two magnetron discharges, it is known, e.g., from German Patent Application Nos. 43 24 683, to interrupt the energy supply in a time-controlled manner. With this kind of process, it is disadvantageous that the effectiveness of the energy supply decreases.
In order to improve the known bipolar energy supply in magnetron devices with two or more electrodes, a process and a circuit are known, e.g., from German Patent Application Nos. 44 38 463, which produce alternating current pulses with the character of a power source, i.e., in each pulse, after a very short current increase time, a constant current is supplied to the magnetron discharge. The disadvantage of this process lies in the fact that it is connected with a very high loading of the semiconductor switching elements used so that currently, the execution of the process can be technically utilized only up to a particular output of the magnetron discharge, which lies well below 20 kW. For this reason, magnetron discharges of, e.g., 100 kW, of the kind that are required for coating architectural glass, have up to this point been powered only with sinusoidal generators. The above-mentioned difficulties with regard to limiting the energy content of arc discharges possibly still occurring and thus limiting damaging effects on the layers cannot be sufficiently eliminated.
SUMMARY OF THE INVENTION
The present invention provides a process and a system for operating magnetron discharges, which improve the energy supply in magnetron discharges with at least two magnetron electrodes.
In particular, the supply of high discharge outputs should also be possible and a high efficiency of the supplied output should be achieved. The production of arc discharges should be inhibited and the production of conditions for producing such arcs should be preventatively counteracted. The process and the associated device should also be suited for adjusting a predetermined ratio of the discharge outputs at the magnetron electrodes, pref

Affiliated with

Also associated with

Rating

Process and system for operating magnetron discharges does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process and system for operating magnetron discharges, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and system for operating magnetron discharges will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2845962