Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-05-19
2001-01-23
McDonald, Rodney (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192130, C204S298080, C427S523000, C427S527000, C427S529000, C427S530000
Reexamination Certificate
active
06176979
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method of controlling a treatment process for an object in a vacuum atmosphere containing electrical chargecarriers and to a vacuum treatment apparatus. More specifically, the invention is directed to such a method or apparatus wherein at least two surfaces of electro-conductive material are exposed to the vacuum atmosphere at least one thereof being at least in part covered with material of lower electro-conductivity than the material of said one surface to form a resultant exposed surface.
The invention may be implemented for all physical vapor deposition treating processes, reactive PVD-processes as well as to all plasma-enhanced CVD-processes. It may also be implemented to other treatment processes if the two surfaces with the covering are exposed in such a process to a vacuum atmosphere with electrical chargecarriers. Such treatment processes are especially reactive or not reactive sputtering by which workpieces are sputter etched or are sputter coated and are thereby biased on predetermined electric potential or are connected to an electric reference potential or are operated on a floating electrical potential.
The present invention is also especially directed to ionplating treatment processes which are reactive or not reactive. It may also be implemented to evaporation processes, e.g. to electron beam evaporation processes, arc evaporation processes, evaporation processes with heated crucibles, all such evaporation processes being possibly part of ionplating processes. Thus, and as repeated, the invention may be implemented to all vacuum treatment processes whereat one of the electro-conductive surfaces is entirely or in part covered with a lower electro-conductive material. This may be caused by the specific treatment process itself or may be due to such a covering at such a surface already provided before the specific treatment process is started as, e.g. if such a covering is a surface oxidation of a metallic part to be exposed to the process.
2. Description of Prior Art, General
It is known that always when electro-conductive surfaces are at least in part covered by a lower electro-conductive material, called an “isolating covering” throughout the following description, and are exposed to the vacuum atmosphere containing electrical chargecarriers, a problem may arise by the fact that the isolating covering will become occupied with electrical chargecarriers. This especially if electro-magnetical force fields are applied to the vacuum atmosphere and/or inhomogeneous distributions of chargecarriers in the atmosphere lead to diffusion-forces in the vacuum atmosphere on such carriers. This may also happen at thermical CVD-treatment processes if chargecarriers are additionally used, e.g. for the activation of a surface to be treated so, e.g. ion or electron bombardment. The occupation by electrical chargecarriers leads to electrostatic charging of the isolating covering like a capacitor up to a degree where such electrostatic fields are established that an uncontrolled discharge occurs, e.g. by break-through or overflash.
Principally this problem was approached up to now in that whenever such surfaces—forming a “oneport” or single port set—were to be fed by electrical energy, as energy generators, AC-generators were applied or a DC-signal generator and additionally, simultaneously and continuously, an AC-signal generator.
In spite of the fact that the problems of uncontrolled discharges, as break-throughs and overflashings only occur stochastically distributed in time and during very short time intervals compared to the treatment process working time, one thus remedied these problems by permanently applying during the entire treatment process working time an AC-generator, be it an impulse-generator, or a RF-generator, etc.
SUMMARY OF THE INVENTION
The present invention departs from the recognition that disturbing phenomena only occur during relatively short time intervals during the overall processing time so that the permanent application of an AC-generator during the overall processing time is in fact not justified if there are options to counteract and avoid the disturbing phenomena by signal control techniques just at the moments and as long as it is necessary to ensure a treatment process to be accomplished, leading to a desired result.
This first object of the present invention is resolved by providing a method of controlling a treatment process for an object in a vacuum atmosphere containing electrical chargecarriers which comprises the steps of:
providing at least two surfaces of electro-conductive material, at least one thereof at least in part covered with material of lower electro-conductivity than the material of said one surface to form a resultant surface;
exposing said surfaces forming an electrical oneport with said resultant surface to said vacuum atmosphere;
connecting an electrical DC-signal to said oneport;
controlling the occupation of said covering by electrical chargecarriers by applying in time intervals a further electrical signal to said oneport, said further electric signal being different from said electrical DC-signal; and
applying said electrical DC-signal during said treatment process considerably longer than said further electric signal.
By this method additionally to the DC-signal generators may be applied to generate the further electric signal in a controlled manner just at moments and just as long as considered necessary i.e. during significantly shorter time intervals, then the DC-signal for the treatment process is applied. This leads to the fact that such additional signal generators may previously be experienced by experiment.
According to the invention, the actual degree of occupation of the isolating covering by chargecarriers may be monitored in real time and dependent on the result of such monitoring, the further electrical signal may selectively be applied.
Thus, and under this first aspect of the present invention it is avoided that a “dangerous” occupation by electrical chargecarriers occurs in spite of electrical DC-feed to the two electro-conductive surfaces.
Departing from the above mentioned recognition the invention has the second important object to counteract the electrostatic effects of an occupation by electrical chargecarriers of the isolating covering in the case that occupation is a desired result of a treatment process as is especially the case for ionplating. Thereby the electrostatic negative effect of such an occupation shall be counteracted and the occupation of the isolating covering with the material of the electrical chargecarriers shall be maintained as the desired result of such a process.
In this way, problems of stochastic discharge shall be resolved independent from whether electrical energy is externally supplied to the two electro-conductive surfaces considered—the oneport—or not.
This is resolved by a method of controlling a treatment process for an object in a vacuum atmosphere containing electrical chargecarriers which comprises the steps of:
providing at least two surfaces of electro-conductive material at least one thereof at least in part covered with material of lower electro-conductivity than the material of said one surface to form a resultant surface;
exposing said surfaces forming an electrical oneport with said resultant surface to said vacuum atmosphere;
repeatedly applying to said oneport in time intervals one of with a predetermined and of with an adjustable repetition rate at least one of a short-circuit and of a source of electrical charge by means of a controlled discharge or charge exchange current path bridging said oneport.
A most typical example in which inherently to the treatment process an occupation by electrical chargecarriers is desired, is ionplating mentioned above. In ionplating processes ions are deposited from the vacuum atmosphere onto a workpiece surface so as to build up a desired coating. Thereby these ions are driven to the said workpiece surface by means of electric f
Haag Walter
K{umlaut over (u)}gler Eduard
Rudigier Helmut
Signer Hans
Wellerdieck Klaus
Balzers Aktiengesellschaft
McDonald Rodney
Notaro & Michalos P.C.
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