Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1997-06-13
2002-06-25
Mills, Gregory (Department: 1763)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S535000, C427S569000, C438S710000, C438S729000, C118S7230ER
Reexamination Certificate
active
06410102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma process method including a plasma CVD (Chemical Vapor Deposition) process capable of well forming crystalline or non-monocrystalline, functional deposit films useful to photosensitive devices for electrophotography, line sensors for capture of image, image pickup devices, photovoltaic devices, etc. as semiconductor devices, a sputtering process capable of suitably forming deposit films of insulating films, metal wires, etc. as semiconductor devices or optic elements, or etching of a body to be processed, or the like and also to an apparatus that can carry out the mentioned plasma process. More particularly, the invention concerns the plasma process method and the plasma process apparatus for processing a substrate, particularly using a plasma as an excitation source and, especially, the invention concerns the plasma process method and the plasma process apparatus that can suitably use high frequencies of 450 MHz and less.
2. Related Background Art
Proposed in the technology of element members used for electrophotographic, photosensitive member are a variety of materials including selenium, cadmium sulfide, zinc oxide, phthalocyanine, amorphous silicon (hereinafter referred to as a-Si), and so on.
Among others, non-monocrystalline deposit films containing silicon as a main ingredient typified by a-Si, for example, amorphous deposit films of a-Si or the like compensated by hydrogen and/or halogen (for example, fluorine, chlorine, or the like), are proposed as high-performance, high-durability, and nonpolluting photosensitive members, some of which are used practically.
U.S. Pat. No. 4,265,991 discloses the technology of the electrophotographic, photosensitive member a photoconductive layer of which is made mainly of a-Si.
The a-Si photosensitive members have high surface hardness, demonstrate high sensitivity also to long-wavelength light such as semiconductor lasers (770 nm to 800 nm), and exhibit little deterioration after repetitive use, and they are widely used, particularly, as photosensitive members for electrophotography in high-speed copiers, LBPs (laser beam printers), and the like.
As methods for forming such deposit films there are many conventional methods known, including the sputtering process, the method for decomposing raw-material gas by heat (the thermal CVD process), the method for decomposing the raw-material gas by light (the photo-CVD process), the method for decomposing the raw-material gas by plasma (the plasma CVD process), and so on.
Among them, the plasma CVD process, which is a method for decomposing the raw-material gas by glow discharge or the like induced by direct current or high-frequency (RF (Radio Frequency) or VHF (Very High Frequency)) microwave and forming a deposit film of thin film on a substrate of glass, quartz, heat-resistive, synthetic resin film, stainless steel, aluminum, or the like, is used for formation of the a-Si deposit films or the like used not only for electrophotography but also for many semiconductor devices and is under very quick development into practical use. A variety of proposals were also made on apparatus for the process.
Further, demands are becoming stronger for improvements in quality of film and in throughput and many ideas are under research.
Especially, the plasma process using high-frequency power is used because of its various advantages including high stability of discharge, applicability to formation of insulating material such as an oxide film or a nitride film, and so on.
Meanwhile, the copiers of nowadays are required to have high performance and high functionality.
One of such pursuit of high performance is an increase in copy speed. The higher the speed, the shorter the time that can be used for electrification, resulting in the tendency to lower the charge potential. Since the time for exposure must be also decreased similarly, higher sensitivity is also required at the same quantity of light.
One of pursuit of high functionality is multicolor copy. In this case, the distance tends to increase between a charging device and a developing device because of a need for mounting of plural developing devices, so that the surface potential is attenuated during that period, thus tending to lower the charge potential at the position of developing device.
As described above, further improvements in the total characteristics including electrifiability are desired for the electrophotographic, photosensitive member using the a-Si film.
Conventionally, deposition rates for obtaining the a-Si film satisfying the performance of photosensitive member for electrophotography were, for example, those of approximately 0.5 to 6 &mgr;m per hour, and higher deposition rates than those might result in failing to achieve sufficient characteristics for the photosensitive member.
In general, in the case of the a-Si film being utilized as a photosensitive member for electrophotography, at least the film thickness of 20 to 30 &mgr;m is necessary for achieving sufficient electrifiability because of the magnitude of its dielectric constant. This was a cause to raise the fabrication cost, because a long time was necessary for fabrication of photosensitive member for electrophotography. Therefore, there were strong demands for the technology to reduce the fabrication time without degrading the characteristics of the photosensitive member.
One method to meet the recent demand for an improvement in electrifiability and the recent demand for a reduction in deposition time is a report of the plasma CVD process using a high-frequency power supply of 50 MHz or more with a diode parallel plate plasma enhanced CVD system (Plasma Chemistry and Plasma Processing, Vol. 7, No. 3 (1987) pp. 267-273), which indicates the possibility of increasing the deposition rate without degrading the performance of deposit film by using the higher discharge frequency than 13.56 MHz used conventionally and which is drawing attention.
Further, JP-A-3-64466 presents a report on application thereof to the electrophotographic, photosensitive member and research thereof is widely conducted in recent years.
The present inventors investigated the plasma CVD process using the high-frequency power at the high frequency in the so-called VHF band of 50 MHz or more and results thereof demonstrated that an increase in the deposition rate was achieved actually and that an improvement was also observed in the performance of deposit film.
This method, however, has the possibility of raising the following problems at the same time.
Specifically, the normal plasma CVD apparatus is provided with a matching circuit for impedance matching between the high-frequency power supply and the load, but, because impedances are distributed in the discharge electrode in the VHF band, the plasma becomes nonuniform in some cases.
Therefore, the most deposition systems are arranged so that not only the matching circuit but also the discharge electrode itself are optimized so as to keep the plasma discharge uniform and so as to suppress the film thickness distribution of deposit film. Especially in the VHF band, in order to prevent the distribution of impedance in the electrode to which the high-frequency power is applied, the area of the electrode is decreased in many cases.
With the thus optimized apparatus satisfactory results were obtained in film formation of device.
In any device deposition systems by vapor deposition, as well as by the plasma CVD process, unless after fabrication of device a deposit film on a deposition chamber etc. other than the substrate is removed by any method, it will generate particles due to exfoliation or the like in next fabrication, which lowers the non-defective rate of products.
Especially, in the case of devices requiring a thick deposit film like the electrophotographic, photosensitive member, an amount of deposits depositing on the other portions than the substrate, per process is large and cleaning is necessitated every time or at very short cycles unless the
Aoki Makoto
Hashizume Junichiro
Ueda Shigenori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mills Gregory
Zervigon Rudy
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