Electrostatic-erasing abrasion-proof coating and method for forming the same Number:7,144,629 from the United States Patent and Trademark Office (PTO) owispatent An abrasion-proof and static-erasing coating is formed on the contact surface of a contact image sensor. The coating comprises a first film having a high hardness and a low conductivity, a second film formed on the first film and having a low hardness and a high conductivity, and a third film having a high hardness and a high resistivity providing an abrasion-proof insulating external surface.<H Electrostatic, abrasion, Electrostatic, e, 7144629.html, Patent, pto, 7144629

Title: Electrostatic-erasing abrasion-proof coating and method for forming the same

Abstract: An abrasion-proof and static-erasing coating is formed on the contact surface of a contact image sensor. The coating comprises a first film having a high hardness and a low conductivity, a second film formed on the first film and having a low hardness and a high conductivity, and a third film having a high hardness and a high resistivity providing an abrasion-proof insulating external surface.

Patent Number: 7,144,629 Issued on 12/05/2006 to Itoh

Inventors: Itoh; Kenji (Zama, JP)
Assignee: Semiconductor Energy Laboratory Co., Ltd. (Kanagawa-ken, JP)

Appl. No.: 10/446,695

Filed: May 29, 2003

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
09837335	Apr., 2001	6583481
08847493	Apr., 1997	6224952
08016240	Feb., 1993	6207281
07660949	Feb., 1991	5190824
07318541	Mar., 1989

Foreign Application Priority Data


Mar 07, 1988 [JP]			63-54467

Current U.S. Class: 428/408 ; 428/217; 428/678; 428/704

Current International Class: B32B 9/00 (20060101)

Field of Search: 428/408,217,704,698

References Cited [Referenced By]

U.S. Patent Documents


1566848	December 1925	Fonda
2344906	March 1944	Swanson
2392682	January 1946	Marek
3084394	April 1963	Lewis
3335345	August 1967	Diefendorf
3630677	December 1971	Angus
3944686	March 1976	Froberg
3961103	June 1976	Aisenberg
3969751	July 1976	Drukaroff et al.
4017340	April 1977	Yerman
4040874	August 1977	Yerman
4060660	November 1977	Carlson et al.
4104441	August 1978	Fedoseev et al.
4142008	February 1979	DeBolt
4194027	March 1980	Adams et al.
4198444	April 1980	Yerman
4401054	August 1983	Matsuo et al.
4434188	February 1984	Kamo et al.
4490229	December 1984	Mirtich et al.
4504519	March 1985	Zelez
4524106	June 1985	Flasck
4569738	February 1986	Kieser et al.
4597844	July 1986	Hiraki et al.
4603082	July 1986	Zelez
4634605	January 1987	Wiesmann
4634648	January 1987	Jansen et al.
4645713	February 1987	Shioya et al.
4647494	March 1987	Meyerson et al.
4661409	April 1987	Kieser et al.
4663183	May 1987	Ovshinsky et al.
RE32464	July 1987	Aine
4698256	October 1987	Giglia et al.
4701317	October 1987	Arakawa et al.
4707384	November 1987	Schachner et al.
4717622	January 1988	Kurokawa et al.
4725345	February 1988	Sakamoto et al.
4734339	March 1988	Schachner et al.
4741982	May 1988	Iino et al.
4743522	May 1988	Iino et al.
4755426	July 1988	Kokai et al.
4767608	August 1988	Matsumoto et al.
4770940	September 1988	Ovshinsky et al.
4772513	September 1988	Sakamoto et al.
4777090	October 1988	Ovshinsky et al.
4816286	March 1989	Hirose
4816291	March 1989	Desphandey et al.
4833031	May 1989	Kurokawa et al.
4835070	May 1989	Kurokawa et al.
4839195	June 1989	Kitamura et al.
4849290	July 1989	Fujimori et al.
4868076	September 1989	Iino et al.
4869755	September 1989	Huschka et al.
4869923	September 1989	Yamazaki
4871632	October 1989	Iino et al.
4880687	November 1989	Yokoyama et al.
4892800	January 1990	Sugata et al.
4898798	February 1990	Sugata et al.
4932859	June 1990	Yagi et al.
4935303	June 1990	Ikoma et al.
4939054	July 1990	Hotomi et al.
4972250	November 1990	Omori et al.
4987007	January 1991	Wagal et al.
4996079	February 1991	Itoh
5013579	May 1991	Yamazaki
5087959	February 1992	Omori et al.
5110676	May 1992	Murai et al.
5159508	October 1992	Grill et al.
5190824	March 1993	Itoh
5275850	January 1994	Kitoh et al.
5368937	November 1994	Itoh
6191492	February 2001	Yamazaki et al.
6265070	July 2001	Itoh

Foreign Patent Documents


2065431	Oct., 1973	DE
0 175 980	Apr., 1986	EP
0 257 439	Mar., 1988	EP
55-8485	Jan., 1980	JP
58-48428	Feb., 1983	JP
58-48428	Mar., 1983	JP
58-110494	Jul., 1983	JP
59-63732	Apr., 1984	JP
62-171993	Jul., 1984	JP
59-170262	Sep., 1984	JP
60-36663	Feb., 1985	JP
60-103098	Jun., 1985	JP
60-137898	Jul., 1985	JP
60-184681	Sep., 1985	JP
60-191097	Sep., 1985	JP
60-195094	Oct., 1985	JP
61-36200	Feb., 1986	JP
61-73882	Apr., 1986	JP
61-106478	May., 1986	JP
61-109628	May., 1986	JP
61-208056	Sep., 1986	JP
61-257466	Nov., 1986	JP
62-280364	Dec., 1987	JP
63-40800	Feb., 1988	JP
63-153275	Jun., 1988	JP
63-183620	Jul., 1988	JP
63-286576	Nov., 1988	JP
64-062468	Mar., 1989	JP
01-267401	Oct., 1989	JP

Other References

IBM Technical Disclosure Bulletin, vol. 25, No. 7A, Dec. 1982, pp. 3173, "Sliders For Magnetic Heads of Surface-Hardened Silicon With Integrated Electronic Components," G. Kaus et al. cited by other .
Raman spectra of diamondlike amorphous carbon films, J. Appl. Phys. 64(11), Dec. 1, 1988, pp. 6464-6468, by M. Yoshikawa, G. Katagiri, H. Ishida, A. Ishitania, and T. Akamatsu. cited by other .
Deposition of Diamond-Like Carbon Films by Pulsed-Laser Evaporation, Japanese Journal of Applied Physics, vol. 26, No. 9. Sep. 9, 1987, pp. L-1487-1488, by Tetsuya Sato, Shigeo Furuno, Satoshi Uguchi and Mitsugu Hanabusa. cited by other .
Resonant Raman scattering of diamondlike amorphous carbon films, Appl. Phys. Lett. 52(10), May 9, 1988, pp. 1639-1641, by M. Yoshikawa, G. Katagiri, H. Ishida, and A. Ishitani. cited by other .
Physical properties of diamondlike carbon film deposited in mixed atmospheres of C.sub.2H.sub.4-Ar, C.sub.2H.sub.4 -H.sub.2and C.sub.2H.sub.4-N.sub.2, J. Vac. Sci. Technol. A 14(4), Jul./Aug. 1996, pp. 2418-2426, by Masatoshi Makayama, Yashuhiro Matsuba, Junichi Shimamura, Yasuyuki Yamamoto, Hiroshi Chihara, and Hideo Kato. cited by other .
IEEE Transactions on Magnetics, vol. Mag-22, No. 5, Sep. 1986, "Dual-Carbon, A New Surface Protective Film For Thin Film Hard Disks," M. Ishikawa, N. Tani, T. Yamada, Y. Ota, K. Nakamura and A. Itoh, pp. 999-1001. cited by other .
Kieser et al., "Large Scale Microwave Plasma Polymerization: A Study on Hydrogenated Carbon Films," J. Vac. Sci. Technol. A 4(2), Mar./Apr. 1986, pp. 222-225. cited by other .
Chemical Abstracts, vol. 92, 1980, pp. 262. cited by other .
Kawarada et al., "Large Area Chemical Vapour Deposition of Diamond Particles and Films Using Magneto-Microwave Plasma," J.J.A.P., vol. 26, No. 6, Jun. 1987, pp. L1032-L1034. cited by other .
Moravec et al., "Electron Spectroscopy of Ion Beam and Hydrocarbon Plasma Generated Diamond Like Carbon Films," J. Vac. Sci. Technol., 18(2), Mar. 1981, pp. 226-228. cited by other .
U.S. Appl. No. 09/698,055, including specification, drawing, filing receipt and pending claims, "Electronic Device and Its Manufacturing Method," Shunpei Yamazaki, et al, Oct. 30, 2000. cited by other.

Primary Examiner: Turner; Archene
Attorney, Agent or Firm: Robinson; Eric J. Robinson Intellectual Property Law Office, P.C.

Claims

What is claimed is:

1. A coating formed on a ceramic surface comprising: an external surface region having an amorphous structure; and a second region between the external surface region and the ceramic surface, said second region having a lower hardness than said external surface region, wherein said external surface region comprises carbon, and hydrogen.

2. The coating of claim 1 wherein the Vickers hardness of said external surface region is not lower than 2000 kg/mm.sup.2.

3. The coating of claim 1 wherein a resistivity of said surface region is 10.sup.7 to 10.sup.13 ohm centimeters.

4. The coating of claim 1 wherein a resistivity of said inner region is 10.sup.2 to 10.sup.6 ohm centimeters.

5. The coating of claim 1 further comprising a blocking region underlying said second region, the hardness of said blocking region being higher than that of said second region.

6. The coating of claim 1 wherein the hardness is gradually changed from said external surface region to said second region.

7. The coating of claim 1 wherein the second region comprises carbon.

8. A coating formed on a ceramic surface comprising: an external surface region having an amorphous structure; and a second region between the external surface region and the ceramic surface, said second region having a lower resistivity than said external surface region, wherein said external surface region comprises carbon, and hydrogen.

9. The coating of claim 8 wherein the Vickers hardness of said external surface region is not lower than 2000 kg/mm.sup.2.

10. The coating of claim 8 wherein a resistivity of said surface region is 10.sup.7 to 10.sup.13 ohm centimeters.

11. The coating of claim 8 wherein a resistivity of said inner region is 10.sup.2 to 10.sup.6 ohm centimeters.

12. The coating of claim 8 further comprising a blocking region underlying said second region, the hardness of said blocking region being higher than that of said second region.

13. The coating of claim 8 wherein the hardness is gradually changed from said external surface region to said second region.

14. The coating of claim 8 wherein the second region comprises carbon.

15. An article comprising: a substrate having a ceramic surface; and a coating formed on a ceramic surface, said coating including an external surface region having an amorphous structure and a second region between the external surface region and the ceramic surface, said second region having a lower hardness than said external surface region, wherein said external surface region comprises carbon and hydrogen.

16. The article of claim 15 wherein the Vickers hardness of said external surface region is not lower than 2000 kg/mm.sup.2.

17. The article of claim 15 wherein a resistivity of said surface region is 10.sup.7 to 10.sup.13 ohm centimeters.

18. The article of claim 15 wherein a resistivity of said inner region is 10.sup.2 to 10.sup.6 ohm centimeters.

19. The article of claim 15 further comprising a blocking region underlying said second region, the hardness of said blocking region being higher than that of said second region.

20. The article of claim 15 wherein the hardness is gradually changed from said external surface region to said second region.

21. The article of claim 15 wherein the second region comprises carbon.

22. An article comprising: a substrate having a ceramic surface; and a coating formed on a ceramic surface said coating including an external surface region having an amorphous structure and a second region between the external surface region and the ceramic surface, said second region having a lower resistivity than said external surface region, wherein said external surface region comprises carbon and hydrogen.

23. The article of claim 22 wherein the Vickers hardness of said external surface region is not lower than 2000 kg/mm.sup.2.

24. The article of claim 22 wherein a resistivity of said surface region is 10.sup.7 to 10.sup.13 ohm centimeters.

25. The article of claim 22 wherein a resistivity of said inner region is 10.sup.2 to 10.sup.6 ohm centimeters.

26. The article of claim 22 further comprising a blocking region underlying said second region, the hardness of said blocking region being higher than that of said second region.

27. The article of claim 22 wherein the hardness is gradually changed from said external surface region to said second region.

28. The article of claim 22 wherein the second region comprises carbon.

Description

BACKGROUND OF THE INVENTION

This invention relates to an electrostatic erasing abrasion-proof coating and method for forming the same.

Abrasion-proof coatings are formed over surfaces which has a tendency to take scratches due to external rubbing actions. The surface of glass plates which may be used for transmitting light therethrough is a typical example of such a surface. Contact image sensor, which have been recently developed, are suitable for use in compact facsimile machines, copying machines or the like. The image sensor makes direct contact with an original and scans the surface of the original by moving relative to this.

An example of the contact image sensor is illustrated in FIG. 1. The sensor comprises a glass substrate 1, a photosensitive semiconductor device 2, a transparent protective layer 3, an adhesive layer 4, an ITO film 5 and a glass pane 6. An original bearing an image to be sensed is placed in contact with the external surface of the glass pane 6. The ITO film, which is a transparent conductive film, is grounded for the purpose of canceling out electrostatic charges collected on the contact surface of the pane 6 due to rubbing action between the original 9 and the glass pane 6. In case of treatment of usual papers, the size of scratches may be of the order of 1 micron meter or less so that the performance of the sensor is not substantially deteriorated by the scratches. However, if a staple is held to a paper to be telefaxed, the paper may give scratches of substantial size which degrade the quality of the transmission. Furthermore, the use of the ITO film for canceling out static electricity increases the size and the production cost of the device.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an excellent abrasion-proof coatings and methods for forming the same which produce no static electricity on the coating even when rubbing action takes place thereon.

In order to accomplish the above and other objects, it is proposed to coat a surface with carbon films in different deposition conditions in order that the external surface of the coating has a higher degree of hardness for providing an abrasion-proof surface and that the carbon coating includes an inner layer whose resistivity is comparatively low (conducting) to extinguish the influence of static electricity. This structure can be realized by inverting the polarity of the pair of electrodes, between which direct or high frequency electric energy is supplied, an object to be coated being mounted on one of the electrodes. When the electrode supporting the object is supplied with high frequency energy (that is to say, the electrode functions as the cathode), the hardness of carbon material becomes high. On the other hand, when the electrode supporting the object is grounded (i.e., the electrode functions as an anode), the hardness becomes low but the conductivity thereof becomes high. By letting the surface be a cathode, carbon material being deposited is eliminated due to bombardment of positive ions such as hydrogen ions, where the elimination rate of soft carbon material is higher than that of hard carbon material.

According to a preferred embodiment of the present invention, the energy band gap of carbon product for forming the external abrasion-proof surface of the coating is not lower than 1.0 eV, preferably 1.5 to 5.5 eV: the Vickers hardness is not lower than 500 Kg/mm.sup.2 preferably not lower than 2000 Kg/mm.sup.2, ideally not lower than 6500 Kg/mm.sup.2, at the external surface of carbon coatings: the resistivity ranges from 10.sup.10 to 10.sup.15 ohm centimeter: and the thermal conductivity of the product is not lower than 2.5 W/cm deg, preferably 4.0 to 6.0 W/cm deg. When used for thermal heads or contact image sensor which are frequently subjected to rubbing action, the smooth, hard and static erasing surface of the carbon coating is very suitable. The carbon coating includes an inner layer region having a low resistivity. The Vickers hardness and the resistivity of the inner layer region are not higher than 1000 Kg/mm.sup.2 preferably 500 to 700 Kg/mm.sup.2, and not higher than 10.sup.12 ohm centimeter, preferably 1.times.10.sup.2 to 1.times.10.sup.6 ohm centimeter. The inner layer region has lower Vickers hardness and higher conductivity than the external surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a prior art contact image sensor.

FIG. 2 is a schematic diagram showing a CVD apparatus for depositing carbon material in accordance with the present invention.

FIG. 3 is a graphical diagram showing the Vickers hardness and the resistivity of carbon films which have been deposited on an electrode functioning as a cathode.

FIG. 4 is a graphical diagram showing the Vickers hardness and the resistivity of carbon films which have been deposited on an electrode functioning as an anode.

FIG. 5 is a schematic diagram of a carbon coating in accordance with the present invention.

FIGS. 6(A), 6(B), 7(A), 7(B), 8(A), and 8(B) are graphical diagrams showing the variations of the hardness and the resistivity of carbon films through the depth thereof in accordance with the present invention.

FIG. 9 is a cross sectional view showing an image sensor given a carbon coating in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 2, there is shown a plasma CVD apparatus for depositing carbon material on a surface in accordance with the teaching of the present invention. The surface to be coated may, for example, be made of semiconductor, glass, metal, ceramics, organic resins, magnetic substance, and so forth.

The apparatus comprises a reaction chamber 18 defining a reaction space 30 therein, first and second electrodes 21 and 22, a high frequency electric power source 23 for supplying electric power between the electrodes 21 and 22 through a matching transformer 24, a DC bias source 15 connected in series between the electrodes 21 and 22, a gas feeding system 11 consisting of four passages 12 to 15 each of which is provided with a flow meter 17 and a valve 16, a microwave energy supply 11, a nozzle 19 through which gas excited by the microwave energy supply 20 is introduced into the reaction space 30, and an exhaust system 26 including a pressure control valve 27, a turbomolecular pump 28 and a rotary pump 29. The electrodes are designed such that (the area of the first electrode 21)/(the area of the second electrode 22)<1. A pair of switching means 31 and 32 is provided for inverting the polarities of the electrodes 21 and 22. In a first position of the switching means, the electrode is grounded while the other electrode 21 is supplied with high frequency electric energy from the power source 23. In the other second position, the electrode 21 is grounded while the electrode 22 is supplied with high frequency electric energy from the power source 23. An object having the surface to be coated is mounted on the electrode 21.

In operation of this apparatus, a carrier gas of hydrogen is introduced to the reaction space 30 from the gas feeding passage 12 as well as a reactive gas of a hydrocarbon such as methane or ethylene from the gas feeding passage 13. The gas introduction rates of hydrogen and the hydrocarbon are 3:1 to 1:3, preferably 1:1. In addition to this, a V-Group dopant gas such as NH.sub.3 or PH.sub.3, or a III-Group dopant gas may be inputted to the reaction space 30 through the gas feeding passage 14 or 15 in order to form impurity semiconductors. Pre-excitation may be effected by the microwave energy supply 10. The pressure in the reaction space is maintained within the range between 0.001 to 10 Torr, preferably 0.01 to 0.5 Torr. High frequency electric energy at a frequency not lower than 1 GHz, e.g. 2.45 GHz, is applied to the reactive gas at 0.1 to 5 kilo Watt for breaking C--H bonds. When the frequency is selected to be 0.1 to 50 MHz, C.dbd.C bonds can be broken and transformed to --C--C-- bonds. By virtue of this reaction, carbon atoms are deposited atoms in the form of a structure in which the diamond structure occurs at least locally.

A bias voltage of, for example, -200 to 600 V is set at the DC bias source 15. The effective bias voltage level is substantially -400 to +400 V when a self bias level in this case of -200 V is spontaneously applied between the electrodes 21 and 22 with the bias voltage level of the source 15 being zero.

Generally, the high frequency input power is chosen between 10 Watt and 5 kilo Watt, preferably between 50 Watt and 1 kilo Watt. This input power corresponds to 0.03 to 3 Watt/cm.sup.2 in terms of plasma energy. The substrate temperature is maintained in a range of +250 to -100.degree. C. by means of a temperature control means (not shown). When diamond deposition is desired, the substrate temperature has to be elevated further.

FIG. 3 shows the resistivity and the Vickers hardness of films deposited on a surface, to which high frequency electric energy was applied through the electrode 21 at various power levels. As can be seen from the figure, a harder film was deposited by inputting higher power energy. FIG. 4 shows the resistivity and the Vickers hardness of films deposited on a surface which was grounded. Comparing FIG. 4 with FIG. 3, it will be apparent that the resistivity of carbon films formed at the anode side (on the grounded electrode) becomes lower than that in the cathode side (supplied with high frequency energy).

In accordance with the teaching of the present invention, a surface is coated with a carbon coating while the deposition condition is changed in order that the hardness of the carbon initially or intermediately deposited on the substrate is relatively low, but the deposition condition is changed such that hardness of the carbon finally deposited becomes very high in order to provide a hard external abrasion-proof surface. This procedure can be carried out in two ways. As seen from FIG. 6(A), the hardness may be changed in steps by stepwise change of the deposition condition in accordance with the above description. Alternatively, as seen from FIG. 6(B), the hardness may be changed continuously from the inner surface to the external surface of the carbon coating.

The hardness or resistivity of the carbon coating can be changed, rather than monotonically, in order that an intermediate region of the coating is conductive and sandwiched by hard carbon regions. FIG. 5 illustrates such a case including three carbon film regions. The lower and top films 41 and 43 are deposited to have a high degree of hardness while the intermediate film 42 is deposited to have low resistivity. This example can be realized in two ways as illustrated in FIG. 7 (stepwise change) and FIG. 8 (continuous change). The lower hard film 41 is semi-insulating so that it protects the surface to be coated electrically and mechanically. Further the lower hard film has a function as a blocking layer to prevent impurity from entering into the intermediate film 42 and also a function of improving adhesivity to the substrate and the electrical property. The intermediate region 42 has conductivity and functions as a Buffer layer to alleviate distortion generated by mechanical stress.

Experiment 1:

A carbon coating was deposited on a transparent polyimide film 35 as shown in FIG. 9. An amorphous silicon photosensitive semiconductor device 34 was formed on a glass substrate 33 in a conventional manner as well as the polyimide film 35. A first carbon film 36 of 0.6 micron meter thickness was formed on the polyimide film 35 under deposition conditions that the structure was placed on the electrode (cathode) supplied with high frequency energy of 260 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen (e.g. methane:hydrogen=1:1) was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 60 minutes. The hardness and the resistivity were measured to be 1000 Kg/mm.sup.2 and 1.times.10.sup.12 ohm centimeter. A second carbon film 37 of 0.5 micron meter thickness was formed on the first film 36 under deposition conditions that the electrode supporting the structure was grounded (as an anode), the input high frequency energy was 300 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen (e.g. methane:hydrogen=1:1) was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 40 minutes. The hardness and the resistivity were measured to be 600 Kg/mm.sup.2 and 1.times.10.sup.10 ohm centimeter. Finally, a third carbon film 38 was deposited in the same deposition conditions as the first film 36. The first film may be dispensed with.

Experiment 2:

This was carried out in accordance with the diagram shown in FIGS. 8(A) and 8(B) rather than FIGS. 7(A) and 7(B). That is, the resistivity and the hardness were continuously decreased and increased along with the decrease and the increase of input energy. Carbon deposition was started under the deposition conditions that the structure was placed on the electrode (cathode) supplied with high frequency energy of 300 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen (e.g. methane:hydrogen=1:1) was 100 SCCM, and the pressure of the reactive gas was 0.03 Torr. The input high frequency energy was gradually decreased from 300 W to 200 W at 0.5 to 2.5 W/min. The hardness and the resistivity were decreased, along with the decrease of the input energy, from 1000 Kg/mm.sup.2 to 500 Kg/mm.sup.2 and from 1.times.10.sup.12 ohm centimeter to not lower than 1.times.10.sup.8 ohm centimeter respectively. The total thickness of this carbon coating was 0.2 micron meter. After the positions of the switch 31 and 32 were reversed (i.e. the electrode 21 was grounded as an anode), carbon deposition was resumed while the input power was decreased from 300 W to 200 W and subsequently increased from 200 W to 300 W at 0.5 to 2.5 W/min. The hardness and the resistivity were changed along with the change of the input energy, that is, the hardness was decreased from 500 Kg/mm.sup.2 to 300 Kg/mm.sup.2 and subsequently increased from 300 Kg/mm.sup.2 to 500 Kg/mm.sup.2 and the resistivity was decreased and then increased within the range between 1.times.10.sup.12 ohm centimeter and 1.times.10.sup.8 ohm centimeter. However, the resistivity of this intermediate layer should be lower than that of the underlying hard carbon coating as illustrated in FIGS. 8(A) and 8(B). The total thickness of this carbon coating was 0.4 to 1 micron meter. After the positions of the switch 31 and 32 were reversed again in the initial positions (i.e. the electrode 21 was supplied with high frequency energy as a cathode), carbon deposition was resumed while the input power was increased from 200 W to 300 W at 0.5 to 2.5 W/min. The hardness and the resistivity were increased, along with the input energy, from 500 Kg/mm.sup.2 to 2000 Kg/mm.sup.2 and from not lower than 1.times.10.sup.8 ohm centimeter to 1.times.10.sup.12 ohm centimeter. However, the resistivity of this upper carbon film should be higher than that of the intermediate layer. The total thickness of this carbon coating was 0.3 to 0.7 micron meter.

Experiment 3:

A first carbon film of 0.6 micron meter thickness was formed on the polyimide film under deposition conditions that the structure was placed on the electrode (cathode) supplied with high frequency energy of 260 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen (e.g. methane:hydrogen=1:1) was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 60 minutes. The hardness and the resistivity were measured to be 1000 Kg/mm.sup.2 and 1.times.10.sup.12 ohm centimeter. A second carbon film of 0.5 micron meter thickness was formed on the first film under deposition conditions that the electrode supporting the structure was grounded (as an anode), the input high frequency energy was 300 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 40 minutes. The hardness and the resistivity were measured to be 600 Kg/mm.sup.2 and 1.times.10.sup.10 ohm centimeter. On the second film, a third external film was deposited at an input energy of 80 W for 50 min., at 150 W for 50 min. and at 300 W for 40 min. sequentially. Then the third film was formed, having its resistivities of 5.times.10.sup.10, 2.times.10.sup.12, and 1.times.10.sup.14 ohm centimeter across its thickness of 1.7 micron meters.

Experiment 4:

A first carbon film of 0.6 micron meter thickness was formed on the polyimide film under deposition conditions that the structure was placed on the electrode (cathode) supplied with high frequency energy of 260 W, the introduction rate of carbide gas such as methane, ethylene, or ethane diluted by hydrogen (e.g. methane:hydrogen=1:1) was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 60 minutes. The hardness and the resistivity were measured to be 1000 Kg/mm.sup.2 and 1.times.10.sup.12 ohm centimeter. After the positions of the switch 31 and 32 were reversed (i.e. the electrode 21 was grounded as an anode), a second carbon film was formed while the input power was decreased from 300 W to 200 W and subsequently increased from 200 W to 300 W at 0.5 to 2.5 W/min. The hardness and the resistivity were changed along with the change of the input energy, that is, the hardness was decreased from 500 Kg/mm.sup.2 to 300 Kg/mm.sup.2 and subsequently increased from 300 Kg/mm.sup.2 to 500 Kg/mm.sup.2 and the resistivity was decreased and then increased within the range between 1.times.10.sup.12 ohm centimeter and 1.times.10.sup.8 ohm centimeter. However, the resistivity of this second carbon film should be lower than that of the first carbon film. The total thickness of this carbon coating was 0.4 to 1 micron meter. On the second film, a third external film was deposited at an input energy of 80 W for 50 min., at 150 W for 50 min. and at 300 W for 40 min. sequentially. Then the third film was formed, having its resistivities of 5.times.10.sup.10, 2.times.10.sup.12, and 1.times.10.sup.14 ohm centimeter across its thickness of 1.7 micron meters.

Experiment 5:

First and third carbon films were deposited in diamond structure. The deposition conditions required to deposited carbon crystals (diamond) were 700 to 900.degree. C. (substrate temperature), 1.0 to 5 KW (input high frequency energy), 12 hours (deposition time) and CH.sub.4/H.sub.2=0.1 to 4 (reactive gas), 3 to 80 Torr (pressure). The thickness of the first and third films were 0.6 micron meter respectively. The Vickers hardness was measured to be 10,000 Kg/mm.sup.2. The resistivity was 1.times.10.sup.15 ohm centimeter. After the first film deposition, a second carbon film (i.e. intermediate film) of 0.5 micron meter thickness was formed on the first film under deposition conditions that the electrode supporting the structure was grounded (as an anode), the input high frequency energy was 300 W, the introduction rate of methane diluted by hydrogen was 100 SCCM, the pressure of the reactive gas was 0.03 Torr, and the deposition time was 40 minutes. The hardness and the resistivity were measured to be 600 Kg/mm.sup.2 and 1.times.10.sup.10 ohm centimeter. Subsequently, the third film was formed under the above deposition conditions.

While a description has been made for several embodiments, the present invention should be limited only by the appended claims and should not be limited by the particular examples, and there may be caused to artisan some modifications and variation according to the invention. For example, it has been proved effective to add hydrogen, a halogen, boron, nitrogen, phosphorus or the like into the carbon coating. Preferably, the proportion of hydrogen or a halogen is not higher than 25 atomic % and the proportion of the other additives are not higher than 5% Also, though the experiments were carried out for depositing carbon coatings on semiconductor substrates, the carbon coatings can be deposited on a substrate made of an organic resin such as PET (polyethylenetelephtalene), PES, PMMA, teflon, epoxy and polyimides, metallic meshes, papers, glass, metals, ceramics, parts for magnetic heads, magnetic discs, and others.

The types of carbon coatings deposited in accordance with the present invention includes amorphous, polycrystals (comprising diamond powders), and diamond films. In the case of a dual film, lower and upper films may be, respectively, amorphous and amorphous (having different hardnesses), amorphous and polycrystals, polycrystals and polycrystals, or polycrystals and a diamond film.

*