Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1999-11-10
2002-04-09
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C156S345420, C118S7230ER, C118S7230VE, C204S298030
Reexamination Certificate
active
06368477
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the field of thin film processing through the use of a plasma. Specifically, the invention relates to the occurrence of arcs and the reaction to these arcs such as exist in the initial conditioning of a target material for such processing. It discloses designs which are particularly suited to direct current (DC) operations especially those which involve the application of a switch-mode power supply.
The field of thin film plasma processing is well known. In this field, a power supply creates an AC or DC electric potential which causes the existence of a plasma. The plasma then acts upon some material so as to cause processing of an item or substrate. This processing may be deposition, etching, or some other type of processing. Depending on the particular application being pursued, the materials, substrates and even the nature of the processing can vary greatly.
One of the challenges that exists for precise processing is the need to establish a target material in a relatively homogeneous state. This is important because when anomalies exist, areas of low impedance can be created and the plasma may begin to discharge or are into such areas. Unlike situations in which a cathodic arc is desirable, in plasma processing applications, the existence of arcs can be undesirable. The arcs can negatively impact the desired processing; they can create areas where precise control is not possible. For these and other reasons it has become customary—and often preferred—to use power supplies having very rapid process control capabilities and having very precise energy control. In DC applications this is often achieved through the utilization of switch-mode power supplies. These power supplies act to create DC power which is derived from a high frequency source. This not only affords the opportunity for rapid reaction to plasma conditions but it also allows for very low energy storage so as to minimize the effects caused by arc occurrences within the plasma.
An important aspect in many plasma processing applications is that of conditioning the target or material so that it may be used to achieve precise processing. Not only are targets periodically replaced as they wear down but also they can be removed to allow different processing to occur. In each of these instances, the replaced target can tend to exhibit a tendency to arc as surface anomalies are eliminated. These anomalies may consist of unclean areas (such as fingerprints and the like) or topographic anomalies (such as scratches and the like). Regardless of their source it is not uncommon that target materials need to be conditioned before production line processing can occur.
In applications where not particularly precise processing is required, this conditioning is merely a nuisance. For instance, in the manufacture of products utilizing high energy storage power supplies, it is not atypical to merely throw away the first few products until a new target is properly conditioned. This can take a few seconds and may not be that expensive. Unfortunately in applications where precise plasma processing is desired such as through the utilization of low energy storage power supplies, this conditioning can take thousands of times longer and can result in the disposal of thousands of times more products due to imperfect processing. For instance in the coating of compact disks, rather than merely disposing of a few disks taking a few seconds, when low energy supplies are used, it can be necessary to dispose of many disks over the course of half an hour's run just to condition the target material. Obviously this is undesirable. Other applications can be more extreme as even a single semiconductor wafer may cost almost one hundred thousand dollars. Conditioning in these applications can also take a full day.
Unfortunately, until the present invention no system existed which both achieved quick and efficient conditioning of a target while also achieving the enhanced processing accuracies possible with a low energy storage power supply. Perhaps surprising in this regard is the fact that although there has been a recognized need to achieve both these criteria, this need has remained unsatisfied until the present invention even though the implementing arcs and elements had long been available.
This is perhaps due to the fact that those skilled in the art of thin film plasma processing did not fully appreciate the nature of the problem and so were not able to achieve the solutions of the present invention. This also may have been due to the fact that those skilled in the art actually accepted directions which were away from the teaching of the present invention. One of these accepted directions was fueled by the perception that particularly delicate target handling and/or the a need to dispose of a large number of initial product runs was merely a requirement for accurate processing. Although discussed earlier in reference to low energy storage power supplies, even this realization was not fully appreciated. Perhaps also showing the degree to which those skilled in the art accepted and were directed toward handling solutions is also evidenced by the fact that until the present invention it appears that no efforts were made to achieve proper conditioning through a variation of the application of power to the plasma. Thus, until the present invention it simply was not possible to achieve both practical conditioning of a target as well as precise processing through the utilization of a low energy storage power supply such as a switch-mode power supply.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a thin film plasma processing system in which the power supply of the system acts to apply different power environments. These environments can act to condition new or replaced targets. The power supply can then switch to a different power environment during the processing event to allow as accurate production processing as possible. In one embodiment, a thin film processing power supply according to this invention can switch either automatically or manually from a conditioning environment to a processing environment. As discussed later, this switching can act to effectively adjust an energy quantum for the thin film plasma processing system through a number of ways.
Thus, it is an object of the invention to achieve the elimination of imperfections in a target material through operation of the supply of power. In keeping with this object is a goal to rapidly eliminate low impedance areas so that precise processing may be instituted at the earliest possible time. It is also a goal to reduce the number of arc occurrences and the interruptions which the processing system experiences. Further, a goal is to provide efficient conditioning of a target in practically implementable systems.
Yet another object of the invention is to provide a system which is capable of simultaneously achieving efficient target conditioning and extremely precise processing without compromising either. In keeping with this object it is also a goal to provide designs which are easily implemented for existing systems and to provide systems which may either manually or automatically switched between environments as desired.
A further object of the invention is to provide a thin film processing system in which the energy quantum can not only be established but also adjusted during operation of the system. In keeping with this object it is a goal to provide a variety of ways to achieve these effects without impacting the ability for precise processing.
Naturally further objects of the invention are disclosed throughout other areas of the specification and claims.
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Advanced Energy Industries Inc.
McDonald Rodney G.
Santangelo Law Offices P.C.
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