METHOD AND APPARATUS FOR PRODUCING SINGLE CRYSTAL CARBON FILMS

Abstract: The invention relates to the methods of developing carbon films used in processing, the jewelry industry, optics, including X-ray, and in electronics. The method of single-crystal films development in a vacuum chamber includes carbon plasma development by means of spraying cathode-target of solid carbon, the acceleration of carbon ions and their precipitation on single-crystal substrate. In accordance with the method suggested, the developed carbon plasma is kept up by carbon atoms, sprayed from the cathode-target surface in smouldering discharge at DC in a magnetron system. To increase the carbon films growth rate, an additional longitudinal magnetic field is applied to the electric field, and to bring down resilient tension in them, the substrate is heated in the process of carbon film growth. The suggested method makes it possible to get dopped single-crystal carbon films by means of spraying dopping materials simultaneously with the spraying of cathode-target made of solid carbon.

Description: METHOD AND APPARATUS FOR PRODUCING SINGLE CRYSTAL CARBON FILMS This invention pertains to a method of developing films, which consists of carbon atoms used in various industres, optics (including X-ray) and electronics. BACKGROUND ART The known way to get diamond films includes an electronic radiation spray of solid carbon in a vacuum chamber, with the follow-up separation of carbon steam and carbon ions precipitation on substrates, situated on electrodes- waffers. The given method is used in equipment which contains an electronic-radiation source, the latter heating the solid carbon block by a beam of electrons with the subsequent spray and separation (USA Patent No. 4981568 C 23 C 14/00, 1991). Sprayed carbon, consisting of positive, negative ions and neutral carbons atoms goes through the aperture of a restricting screen and is separated by a DC field which is perpendicular to the beam. The DC field, with the tension of 100 v/sm, is created by electrode waffers located behind the screen in such a way that the carbon steam column coming out of the screen aperture goes between the waflFers. Simultaneously these waffers are the holders of silicon single-crystal substrates. Using the above method produces only polycrystal diamond films, which is its main drawback. Besides, large quantities of power are needed to spray solid carbon by the beam of electrons. The closest to the claimed invention, is a method to develop diamond films in a vacuum chamber, and the arrangement to carry this method out is described in the paper of A.V.Averin, G.V.Akulova, V.S.Korsakov, V.I.Mishachyov, L.A. Semenikhina, N.F.Trutnyev "X-ray templates on the basis of diamond films". Magazine "Electronnaya Promyshlennost" (Electronic Industry), No.3, 1992, pp.33-35. The idea of this method is that carbon plasma is created in a vacuum chamber at the residual pressure of 10 Pa in an electric arc impluse plasma accelerator (EAIFA) by way of spraying solid carbon cathode. Then carbon ions are accelerated due to accelera¬ ting tension of 300-500 V applied to the substrate holder. Carbon ions precipitation on silicon substrate is done at discharge distance of 400 mcs. To achieve this method, the equipment used is a vacuum chamber containing EAIFA . At the EAIFA output there is a graphite cathode, below which there is an annular graphite anode. In the lower part of the vacuum chamber under the annular graphite anode there is a rotating substrate holder, to which accelerating tension is applied. Silicon substrate is located on the substrate holder. Using this method and the above described arrangement, it is possible to develop diamond like films, which are amorphous in their structure. The gool of this invention is to work out a method and the necessary equipment with which it is possible to get, in conditions of low pressure, single-crystal carbon films on single-crystal substrates. The invention suggested also gives the possibility to obtain dopped single-crystal carbon films having the properties of semiconductors. DISCLOSURE OF INVENTION The objectives put are achieved through a new organization of the process of developing carbon films at low pressure and creating new arrangements for this process fulfilment. Carbon plasma is obtained by spraying a cathode - the target of solid carbon. The resulting plasma is sustained by carbon atoms, sprayed from the surface of cathode- target in a smouldering discharge with DC in a magnetron system. Then carbon ions are accelerated and precipitated on a single-crystal substrate. Initially carbon atoms and electrons are knocked out by the positive ions of residual gas. After that, the electrons move from the cathode-target to anode ionize carbon atoms. Carbon ions in their turn knock out new carbon atoms and electrons from the surface of the cathode- target. Thus there appears the possibility to sustain carbon plasma in conditions of smouldering discharge by carbon atoms themselves. This makes is possible to get a uniform composition of carbon plasma, which is one of the main conditions of getting single-crystal carbon films. The invention suggested also makes it possible to increase single-crystal films growth rate by means of additional application of lontitudinal magnetic field to the electric field. In this case, the length of the electron run increases with the result that the number of ionized carbon atoms grows as does the density of carbon plasma. Substrate heating in the process of carbon films growth makes it possible to bring down resilient tensions in a single-crystal film. Co-spraying of solid carbon together with the dopped material makes it possible to get single-crystal films, having the properties of semi-conductors and in this way widen the sphere of single-crystal and carbon films use. The claimed method of developing single-crystal films is performed with the help of new models of arrangements. The suggested arrangement has a vacuum chamber, cathode - target and an annular anode, all made of solid carbon and a single-crystal substrate. It is marked by the fact that it has an additional cathode with an aperture for carbon ions flow and a magnate. It should be noted that the cathode with an aperture is between the anode the substrate. Such position of the additional cathode makes it possible to extract from plasma consisting of electrons, carbon ions and carbon atoms, positive carbon ions with the follow up acceleration. The magnate, located behind the cathode-target, is made of solid carbon from the side, opposite to the annular anode. This makes it possible to increase the number of ionized carbon atoms by means of the run length of the electrons. In order to increase the single-crystal films growth rate, the suggested arrangement is equipped with an additional magnate, located above the substrate from the side opposite to the additional cathode. This extra magnate is oriented towards the main one with the possibility to form a longitudinal magnetic field. It is also suggested to equip the arrangement with the dopping unit, consisting of anode, magnate and cathode made of dopping material and located between anode and magnate. It should be noted that the dopping unit is arranged in such a way that there is the possibility to mix the flows of dopping material ions and carbon. The presence of the dopping unit and its location make it possible to get dopped single-crystal carbon films having the properties of semi-conductors. BRIEF DESCRIPTION OF DRAWINGS The invention is explained by the following drawings. Fig.1 shows the arrangement from the point 6 of the invention formula for the development of single-crystal carbon films in conditions of low pressure on a single-crystal substrate, which implements the suggested method according to point 1 of the invention formula. Fig. 2 shows the arrangement according to point 7 of the invention formula, implement- ting the method according to point 2 of the formula. Fig. 3 shows the arrangement for the creation of single-crystal carbon films with substrate heating, which implements the method according to point 3 of the formula. Fig. 4 shows the arrangement according to point 8 of the formula which is used to implement the method of developing dopped single-crystal carbon films according to point 4 and 5 of the formula. MODES FOR CARRYING OUT THE INVENTION The suggested arrangement (Fig.1) has a vacuum chamber 1 with annular anode 4 of solid carbon, and cathode-target 2 made of solid carbon, under which there is magnate 3. It is additionally equipped with cathode 5 made of solid carbon, over which there is substrate 6 of single-crystal material. Cathodes 2 and 5 are connected with each other and have nega¬ tive potential with respect to anode 4, located between them. The vacuum chamber is equipped with the pumping out system 7. Electrical tension between the anode and the cathode is supplied from a DC source. The arrangement, shown in Fig.3, is additionally equipped with the heating element 10, located over substrate 6 from the side opposite to extra cathode 5. Heating filament 10 in this case is connected with the power source 11. The arrangement, shown in Fig.4, is additionally equipped with the dopping unit, consis- ting of anode 12, cathode 13 made of dopping material and magnate 14. The dopping unit is connected with power source 15. Cathode 13 is located between anode 12 and magnate 14. In this case the dopping unit is arranged in such a way that there is a possibility to mix the ions of dopping substance and carbon in the vicinity of substance 6. The arrangement suggested functions in the following way. With the help of the pumping out system 7, certain residual pressure is achieved, the volume of which depends on the kind of carbon film ( graphite, diamond and etc.). Then applying electrical tension from the source 8 to anode 4 there is a possibility to get smouldering discharge between cathode 2 and anode 4. By the choice of the distance between cathode and anode, it is possible to get stable, structurally uniform carbon plasma which is sustained by means of carbon atoms and elect - rons, knocked out from the surface of cathode-target 2. In this case electrons, moving from cathode 2 towards anode 4, ionize carbon atoms. By means of the magnetic field influence of magnate 3 the run length of the electrons increases, and consequently so does the number of ionized carbon atoms. Positive carbon ions, which reach the annular space of anode 4 due to their kinetic energy, are speeded up towards cathode 5 by the electric field, existing between anode 4 and cathode 5. Having passed through the annular space of cathode 5, they get to the single-crystal substrate 6 where they precipitate and form single-crystal carbon film. To increase the growth rate of single-crystal films, the arrangement is equipped with extra magnate 9, which together with magnate 3 form a magnetic field. As a result of this, electron run length increases still more which results in the increase of the number of positive carbon ions which are formed during the time unit per area unit. On carbon ions precipitation on the cold substance, in the resulting single-crystal films, restilient tensions appear which shorten the life of the film obtained. To eliminate this drawback, the suggested arrangement is equipped with heating element 10, which is, in fact, the tungsten filament(see Fig.3). It heats substrate 6 to a certain temperature. The tension on the heating element is supplied from power source 11. In order to get dopped single-crystal films the arrangement (Fig. 4) is used, where the spraying of cathode 13, made of dopped material, is done simultaneously with the spraying of cathode 2 made of solid carbon Cathode 13 dopping is performed in a way similar to cathode 2 dopping in the regime of smouldering discharge. This smouldering discharge is obtained by applying tension from the source of DC 15. The flow of carbon plasma and that of a dopping substance get mixed in the vicinity of substrate 6 and precipitate on it, forming dopped single-crystal carbon film. Example No. 1. The process of developing single-crystal carbon film was carried out in vacuum chamber 1 under the pressure of lOTPa. For that purpose, the arrangement, consis¬ ting of graphite cathode 2, annular graphite anode 4, substrate 6, made of single-crystal silicon waffer with orientation (100), located behind the annular graphite cathode 5 and magnate 3, which is behind cathode 2 was used. Cathode 2 and cathode 4 are con¬ nected with each other electrically. Smouldering discharge was obtained from source 2 by way of applying tension of 5 kV between anode 4 and cathodes 2 and 5. Choosing the distance between cathodes 2 and 5 and anode 4, stable uniform carbon plasma of smouldering discharge was developed. The process of graphite cathode 2 dopping in smouldering discharge and carbon ion precipitation on carbon substrate 6 resulted in single-crystal carbon film. Investigations of the films by X-ray structural analyses showed, that the films obtained are single-crystalled and have the structure of a diamond with orientation (111). Specific 10 weight of the resulting single-crystal carbon films was p=10 ohm.sm. The films micro- solidity (according to Moss) is 1, which corresponds to diamond microsolidity. When bringing residual pressure up to 10 jPa and correspondingly bringing down tension to 500 V, single-crystal graphite film was obtained on the substrate. In example 2 the arrangement similar to the one described in example 1 was used. The difference was that the arrangement was equipped with additional magnate 9 to create the longitudinal magnetic field in the arrangement. This longitudinal magnetic field contributed to the density increase of the plasma, which made it possible to bring down tension, sustaining 5 kV up and 3 kV at constant distances between cathode and anode. Investigation results of the samples showed, that the presence of addi¬ tional magnate 9 did not have any obvious influence on the films single-crystality. However, in the process of dusting, the film growth rate. Thus, in example 1, the growth rate was 100 A per hour while in example 2, growth rate increased up to 1000 A per hour with the rest of the parameters remaining constant. Example 3. In the arrangement similar to that described in example 1, the heating of single-crystal silicon substrate was carried out. The heating was done with the help of heating element 10, made of tungstem. The substrate heating was carried out at a temperature of 50θ"C. Due to this, it became possible to bring down resiUent tension in the films. Example 4. Single-crystal dopped films are developed in the arrangement similar to the one described in example 2 with the extra dopping unit. The dopping unit cathode was made of boron oxide. When the tension of 1,5 kV was applied to anode 12, it was possible to achieve stable plasma consisting of dopping material (boron). On mixing the latter with the flow of carbon plasma and on precipitation of the mixed flow on silicon substrate, carbon films dopped by boron, having the property of semi-conductors of R-type, were obtained. Specific resistance of these semi-conductors was up p=10 ohm.sm. From the example given above, it is obvious that the invention suggested ensures the possibility of getting single-crystal carbon films on single-crystal carbon substrates. The films gotten in this way may be used in electronics, and in the jewelry industry, inclu¬ ding roentgen- structural investigations monochromates.

Claims: CLAIMS 1. The method of developing single-crystal carbon film in a vacuum chamber at residual pressure, including carbon plasma development by way of dopping cathode-target of solid carbon, carbon ions acceleration and their precipitation on single-crystal substrate, differs in, that developed carbon plasma is kept up by the carbon atoms, dopped from the surface of cathode-target in smouldering discharge, in DC magnetron system. 2. This method, from the point 1, differs in that the electron field is additionally applied to longitudinal magnetic field. 3. This method, from the point 1 or 2, differs in that the heating of substrate is done in. 4 . This method, from the point 1 or 2 or 3, differs in, that spraying of cathode- target of solid carbon is done in the presence of dopping mixture. 5. This method, from rhe point 4, differs in that the spraying of the cathode- target of solid carbon is done simultaneously with the dopping mixture spraying. 6. The arrangement for the development of single-crystal carbon film, contains a vacuum chamber, cathode-target and annular anode, made of solid carbon and single-crystal substrate. This arrangement differs in that it contains additional cathode of solid carbon with an aperture located between the anode and the substrate and the magnet, which is located behind the cathode-target from the side opposite to annular anode. 7. This arrangement, from the point 6, is different in that it is equipped with an additional magnate located over the substrate from the side opposite to the additional cathode with the possibility to form longitudinal magnetic field. 8. This arrangement, from the point 6 or 7, differs in that it is additionally equipped by a dopping unit consisting of a magnate anode and cathode made of dopping material and located between anode and magnate. In this case, the dopping unit is placed in such a manner that there is the possibility to mix ion flows of dopping material and carbon.

Inventors: KAPPAROV KAIRAT KAPPAROVICH, OMAROV MARAT AKHMETOVICH, KAPPAROV, KAIRAT KAPPAROVICH, OMAROV, MARAT AKHMETOVICH
Applicants: KAPPAROV KAIRAT KAPPAROVICH, OMAROV MARAT AKHMETOVICH, KAPPAROV, KAIRAT KAPPAROVICH, OMAROV, MARAT AKHMETOVICH
Application year: 1996
Main classification: C30B23
IPC codes: C23C14, C30B23, H01J37