METHOD FOR FORMING A DEPOSITED FILM

Abstract: A method for forming a deposited film comprises intro­ ducing a gaseous starting material for formation of a deposi­ ted film and a gaseous halogenic oxidizing agent (X) having the property of oxidation action on said starting material, at least one oxidizing agent (ON) of gaseous oxygen type and nitrogen type oxidizing agents, and preferably also a gaseous material (D) containing a component for valence electron controller as the constituent into a reaction space to effect chemical contact among them to thereby form a plural number of precursors containing precursors under excited states, and forming a deposited film on a substrate existing in the film forming space with the use of at least one precursor of these precursors as the feeding source for the constituent element of the deposited film.

Description: This invention relates to a method for formation of a functional film, particularly a functional deposited film which may be used in semiconductor devices, photosensitive devices for electrophotography, electronic devices such as optical input sensor devices for optical imaging, etc. In the prior art, for amorphous or polycrystalline functional films such as semiconductor films, insulating films, photoconductive films, magnetic films or metal films, individually suitable film forming methods have been employed from the standpoint of desired physical characteristics, uses, etc. For example, for formation of silicon deposited films such as amorphous or polycrystalline, non-single crystalline silicon, which are optionally compensated for lone pair electrons with a compensating agent such as hydrogen atoms (H) or halogen atoms (X), etc., (hereinafter abbreviated as "NON-Si (H, X)", particularly "A-Si (H, X)" when indicating an amorphous silicon and "poly-Si (H, X)" when indicating a polycrystalline silicon) (the so called microcrystalline silicon is included within the category of A-Si (H, X) as a matter of course), there have been attempted vacuum vapour deposition, plasma CVD, thermal CVD, reaction sputtering, ion plating, optical CVD, etc. Generally, plasma CVD has been widely used and industrialized. However, the reaction process in formation of a silicon deposited film according to the plasma CVD method which has been generalized in the prior art is considerably complicated as compared with the more conventional CVD method, and its reaction mechanism involves not a few uncertainties. Also, there are a large number of parameters for formation of a deposited film (for example, substrate temperature, flow rate and flow rate ratio of the introduced gases, pressure during formation, high frequency power, electrode structure, structure of the reaction vessel, speed of evacuation, plasma generating system, etc.). Owing to the combination of such a large number of parameters, the plasma may sometimes become unstable, and marked deleterious influences can be exerted on the deposited film formed. Besides, the parameters characteristic of the apparatus must be selected for each apparatus and therefore it has been difficult to generalize production conditions. On the other hand, for the silicon type deposited film to exhibit sufficiently satisfactory electric and optical characteristics for respective uses, it is now accepted that the plasma CVD method is the best choice of method. However, depending on the intended use of the silicon deposited film, bulk production with reproducibility must be achieved with satisfactory scaling of area, uniformity of film thickness as well as uniformity of film quality, and therefore in formation of a silicon deposited film according to the plasma CVD method, enormous installation investment is required for a bulk production apparatus. Also process control for such bulk production would be both complicated and severe, and process tolerance would be restrictive. These are pointed out as problems that need to be addressed in the future. Also, in the case of the plasma CVD method, since plasma is directly generated by high frequency or microwave, etc., in the film forming space in which a substrate on which a film is formed is arranged, electrons or a number of ion species generated may damage the film during the film forming process and cause a degradation or non-uniformity in film quality. As an improvement, the indirect plasma CVD method has been proposed. In the indirect plasma CVD method the effective chemical species for film formation are used selectively, the plasma is produced using microwave irradiation, at an upstream position remote from the film forming space and this plasma is transported to the film forming space. However, even in the case of such a plasma CVD method, transport of plasma is essentially required and therefore the chemical species effective for film formation must have long life. The gas species which can be employed are thus restricted, and thus the production of various deposited films is precluded from the scope of this method. Also, enormous energy is required for the generation of plasma, and the generation of the chemical species effective for film formation and their amounts cannot be subjected readily to simple control. Thus, various problems remain to be solved. As contrasted to the plasma CVD method, the optical CVD method is advantageous in that no ion species or electrons are generated which otherwise might degrade film quality during film formation. However, there are still problems. The choice of light source is limited since the wavelength required of such light source tends to be at the UV end of the spectrum. A large size light source and a high power source are required in the case of industrialization. The window interposed between the light source and the film forming space, is coated with film during film formation and results in a lowering in dose during film formation. This may lead eventually to complete obscuration of the light from the light source. As described above, in the formation of silicon type deposited films, problems still remain to be solved. A bulk production method of film deposition is needed. Such method should be capable of attaining those film characteristics and uniformity already available in current practice, be capable of implimentation at low cost and economic in the utilisation of energy. The solution to such problems is all the more severe when it is also required to enhance doping rates for formation of p_, n_, or i-type semiconductor film. Similar problems remain to be solved in devising bulk production methods for depositing other species of films such as films of silicon nitride, silicon carbide, or silicon oxide. An object of the present invention is to avoid or at least alleviate the drawbacks of the methods for forming deposited films described above. Another object of the present invention is to provide a method for forming a deposited film capable of saving energy and at the same time obtaining a deposited film having uniform characteristics over a large area with easy control of film quality. Still another object of the present invention is to provide a method for forming a deposited film by which a film excellent in productivity and bulk productivity, having high quality as well as excellent physical characteristics such as electrical, optical, semiconductor characteristics, etc., can be easily obtained. According to one aspect of the present invention, there is provided a method for forming a deposited film which comprises introducing a gaseous starting material for formation of a deposited film, a gaseous halogenic oxidizing agent (X) having the property of oxidation action on said starting material, and at least one gaseous oxidizing agent selected from oxygen containing or nitrogen containing oxidizing agents having this same property, into a reaction space to effect chemical contact among them to thereby form a plural number of precursors containing one or more precursors in an excited state, and forming a deposited film on a substrate existing in the film forming space using at least one amongst these precursors as the feeding source for a constituent element of the deposited film. According to another aspect of the present invention, there is provided a method for forming a deposited film which comprises introducing a gaseous starting material for formation of a deposited film, a gaseous halogenic oxidizing agent (X) having the property of oxidation action on said starting material at least one gaseous oxidizing agent selected from oxygen containing or nitrogen containing oxidizing agents, and a gaseous material containing a component to act as an active dopant constituent in the film, into a reaction space to effect chemical contact among them to thereby form a plural number of precursors containing precursors in excited states, and forming a deposited film on a substrate existing in the film forming space using at least one amongst these precursors as the feeding source for a constituent element of the deposited film. In the accompanying drawing: Fig. 1 is a schematic illustration of a film forming apparatus for performing the method of film deposition in accordance with the present invention. In the method for forming a deposited film described below, the gaseous starting material to be used for the formation of the deposited film is subject to oxidizing action upon chemical contact with gaseous oxidizing agents and can be selected suitably as desired depending on the kind, the characteristic, use, etc., of the desired deposited film. The above gaseous starting material and the gaseous oxidizing agents may be those which can be made gaseous on chemical contact, and they can be either liquid or solid in their ordinary state. In this method, use of a gaseous material (D), containing a component for active doping is optional. It too is subjected to oxidizing action upon chemical contact with the gaseous oxidizing agent and can be selected suitably as desired depending on the kind, the characteristic, use, etc., of the desired deposited film. The above gaseous starting material, the gaseous material (D), and the gaseous oxidizing agent may be those which can be made gaseous on chemical contact, and they can be either liquid or solid in their ordinary state. When the starting material, material (D) or the oxidizing agent is liquid or solid in its ordinary state, it can be introduced in gaseous state into the reaction space by performing bubbling using a carrier gas such Ar, He, N₂, H₂, etc. Heat may be applied while bubbling is performed. During this operation, the partial pressures and mixing ratio of the above gaseous starting material, the material (D), and the gaseous oxidizing agent may be set by controlling the flow rate of the carrier gas or the vapour pressures of the starting material and the gaseous oxidizing agent. As the starting material, if tetrahedral type deposited films such as semiconductive silicon deposited films or germanium deposited films, etc., are desired to be obtained, straight chain and branched chain silane compounds, cyclic silane compounds, chain germanium compounds etc., may be employed as appropriate. Specifically, examples of straight chain silane compounds may include Si n H 2n + 2 ( n = 1, 2, 3, 4, 5, 6, 7, 8), examples of branched chain silane compounds include SiH₃ SiH(SiH₃)SiH₂ SiH₃, and examples of chain germanium compounds include Ge m H 2m + 2 ( m = 1, 2, 3, 4, 5), etc. In addition to these compounds, for example, hydrogenated tin such as SnH₄, etc., may be employed. Of course, these silicon type compounds and germanium type compounds may be used either as a single kind or as a mixture of two or more kinds. The oxidizing agents to be used are gaseous when introduced into the reaction space and at the same time have the property of effectively oxidizing the gaseous starting material introduced into the reaction space upon mere chemical contact therewith. Choice of these include oxygen containing oxidizing agents, nitrogen containing oxidizing agents, halogenic oxidizing agents, specifically oxygens such as air, oxygen, ozone, etc., compounds containing oxygen and nitrogen such as N₂O₄, N₂O₃, N₂O, etc., peroxides such as H₂O₂, etc., halogenic gases such as F₂, Cl₂, Br₂, I₂, etc., and fluorine, chlorine, bromine, etc., in nascent state. These oxidizing agents are introduced into the reaction space in gaseous state together with the gas of the starting material and the above material (D) as described above with a desired flow rate and a feeding pressure, wherein they are mixed with and collided against the above starting material and the above material (D) to be chemically contacted therewith, thereby oxidizing the above starting material and the above material (D) to generate efficiently a plurality of precursors including precursors in excited states. Of the precursors in excited states and other precursors generated, at least one of them functions as the feeding source for a constituent element of the deposited film formed. The precursors generated may undergo decomposition or reaction to be converted into other precursors in excited states or to precursors in other excited states or alternatively in their original forms, if desired, releasing energy on contact with the substrate surface arranged in the film forming space. In this manner a deposited film having a three-dimensional network structure can be prepared. As to each precursor in an excited state, it is preferable that it should be excited to such an energy level that the subsequent transition to a lower energy level or change to another chemical species should produce luminescence. This promotes an increase in process efficiency, and energy conservation. The proportion of the halogenic oxidizing agent to the oxygen containing and/or the nitrogen-containing oxidizing agent introduced into the reaction space may be determined suitably depending on the kind and the desired characteristics of the deposited film to be prepared, but is preferably 1000: 1 to 1: 50, more preferably 500: 1 to 1: 20, optimally 100: 1 to 1: 10. In this method, as the material (D), which contains the component to act as the active dopant constituent in the film, it is preferable to select a compound which is in gaseous state under normal temperature and normal pressure. Alternatively, however, a material that will become a gas or one that can be transported as vapour, under deposition conditions, would be acceptable. For producing doped silicon type or germanium type semiconductor film, p-type active dopant may be introduced by using as material (D) a compound of an element in group 3B of the periodic table, e.g. a compound of: boron (B); aluminium (Al); gallium (Ga); indium (In); tellurium (TI); etc. Similarly n-type active dopant may be introduced by using as material (D) a compound of an element in group 5B of the periodic table, e.g. a compound of: nitrogen (N); phosphorus (P); arsenic (As); antimony (Sb); bismuth (Bi); etc. Specific examples of such compounds are NH₃, HN₃, N₂H₅N₃, N₂H₄, NH₄N₃, PH₃, P₂H₄, AsH₃, SbH₃, BiH₃, B₂H₆, B₄H₁₀, B₅H₉, B₅H₁₁, B₆H₁₀, B₆H 12′ , Al(CH₃)₃, Al(C₂H₅)₃, Ga(CH₃)₃, In(CH₃)₃, etc. For introducing the gas of the above material (D) into the reaction space, it can be mixed with the above starting material prior to introduction. Alternatively the material (D) and the starting material can be introduced from independent gas feeding sources. So that the film deposition process may proceed smoothly to result in a film of high quality with desired physical characteristics, as the film forming factors, the kinds and combination of the starting material for the formation of a deposited film, the material (D), and the oxidizing agent, mixing ratio of these, pressure on mixing, flow rate, the inner pressure in the film forming space, the flow types of the gases, the film forming temperature (substrate temperature and atmosphere temperature) are selected suitably as desired. These film forming factors are inherently related to each other, and they are not determined individually but determined respectively under mutual relationships. In the present invention, the ratio of the gaseous starting material for the formation of a deposited film and the gaseous oxidizing agent introduced into the reaction space may be determined suitably as determined in relationship of the film forming factors related among the film forming factors as mentioned above, but it is preferably 1: 100 to 100: 1, more preferably 1: 50-50: 1 in terms of the flow rate ratio introduced. The proportion of the gaseous material (D) may be set suitably as desired depending on the kind of the above gaseous starting material and the desired semiconductor characteristics of the deposited film to be prepared, but it is preferably 1: 100000 to 1: 10, more preferably 1: 100000 to 1: 20, optimally 1: 100000 to 1: 50 based on the above gaseous starting material. The pressure on mixing when introduced into the reaction space may be preferably higher in order to enhance chemical contact amont the above gaseous starting material, the gaseous material (D), and the above gaseous oxidizing agent in probability, but it is better to determine the optimum value suitably as desired in view of the reactivity. Although the pressure on mixing may be determined as described above, each pressure on introduction may be preferably 1 × 10 _7 atm to 10 atm (10 _2 to 10⁶ Pa), more preferably 1 × 10 _6 atm to 3 atm (10 _1 to 3 × 10⁵ Pa). The pressure within the film forming space, namely the pressure in the space in which the substrate, on which surfaces are subjected to film formation, is arranged, may be set suitably as desired so that the precursors (E) under excited states generated in the reaction space and sometimes the precursors (F) formed as secondary products from the precursors (E) may contribute effectively to the film formation. The inner pressure in the film forming space, when the film forming space is continuously open to the reaction space, can be controlled in relationship with the introduction pressures and flow rates of the gaseous starting material, the gaseous material (D), and the gaseous oxidizing agent in the reaction space, for example, by application of a contrivance such as differential evacuation or use of a large scale evacuating device. Alternatively, when the conductance at the connecting portion between the reaction space and the film forming space is small, the pressure in the film forming space can be controlled by providing an appropriate evacuating device in the film forming space and controlling the evacuation amount of this device. On the other hand, when the reaction space and the film forming space are integral and the reaction position and the film forming position are merely different in space, it is possible to effect differential evacuation or provide a large scale evacuating device having sufficient evacuating capacity as described above. As described above, the pressure in the film forming space may be determined in the relationship with the introduction pressures of the gaseous starting material, the gaseous material (D), and the gaseous oxidizing agent introduced into the reaction space, but it is preferably 0.001 Torr to 100 Torr (0.13 to 1.3 × 10⁴ Pa), more preferably 0.01 Torr to 30 Torr (1.3 to 4 × 10³ Pa), optimally 0.05 Torr to 10 Torr (6.7 to 1.3 × 10³ Pa). As for the flow type of the gases, it is necessary to design the flow type in view of the geometric arrangement of the gas introducing inlet, the substrate, and the gas evacuating outlet so that the starting material, the material (D), and the oxidizing agent may be uniformly and efficiently mixed on introduction into the reaction space. The above precursors (E) may be efficiently generated and the film formation may be adequately done without trouble. A preferred example of the geometric arrangement is shown in Fig. 1. The substrate temperature (Ts) during film formation can be set suitably as desired individually depending on the gas species employed and the kinds and the required characteristics of the deposited film to be formed, but, in the case of obtaining an amorphous film, it is preferably in the range from room temperature to 450°C, more preferably from 50 to 400°C. Particularly, in the case of forming a silicon type deposited film having better semiconductor characteristics and photoconductive characteristics, etc., the substrate temperature (Ts) is desirably 70 to 350°C. On the other hand, for obtaining a polycrystalline film, it is preferably in the range 200 to 650°C, more preferably 300 to 600°C. As the ambient temperature (Tat) in the film forming space, it may be determined suitably as desired in relationship with the substrate temperature so that the above precursors (E) generated and the above precursors (F) are not changed to unsuitable chemical species for film formation, and also the above precursors (E) may be efficiently generated. The substrate to be used in the present invention may be either electroconductive or electrically insulating, provided that it is selected as desired depending on the use of the deposited film to be formed. As the electroconductive substrate, there may be mentioned metals such as NiCr, stainless steel, Al, Cr, Mo, Au, Ir, Nb, Ta, V, Ti, Pt, Pd etc. or alloys thereof. As insulating substrates, there may be used films or sheets of synthetic resins, including polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, etc., glasses, ceramics, papers and so on. At least one side surface of these substrates is preferably subjected to a treatment for imparting electroconductivcity, and it is desirable to provide other layers on the side at which said electroconductive treatment has been applied. For example, electroconductive treatment of a glass can be effected by providing a thin film of NiCr, Al, Cr, Mo, Au, Ir, Nb, Ta, V, Ti, Pt, Pd, In₂O₃, SnO₂, ITO (In₂O₃ + SnO₂) thereon. Alternatively, a synthetic resin film such as polyester film can be subjected to electroconductive treatment on its surface by vacuum vapour deposition, electron-beam deposition or sputtering of a metal such as NiCr, Al, Ag, Pb, Zn, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, Ti, Pt, etc., or by a laminating treatment with such a metal, thereby imparting electroconductivity to the surface. The substrate may be shaped in any form such as cylinders, belts, plates or the like, and its form may be determined as desired. The substrate is preferably selected from among those set forth above taking into account adhesion and reactivity between the substrate and the film. Furthermore, if the difference in thermal expansion between both is great, a large amount of strain may be created within the film and may lead to poor yield. It is preferable therefore to choose a substrate such that the difference in thermal expansion between substrate and film is small. Also, the surface state of the substrate is directly related to the structure (orientation) of the film. Therefore it is desirable to treat the surface of the substrate so that desired characteristics of film structure and film texture may be obtained. Fig. 1 shows an example of a preferred apparatus for practicing the method for forming deposited film according to the present invention. The deposited film forming apparatus shown in Fig. 1 is broadly classified into a main apparatus, an evacuation system, and a gas feeding system. In the main apparatus, a reaction space and a film forming space are provided. 101-108 are respectively bombs filled with the gases to be used on the film formation, 101a-108a are respectively gas feeding pipes, 101b-108b are respectively mass flow controllers for controlling the flow rates of the gases from the respective bombs, 101c-108c are respectively gas pressure gauges, 101d-108d and 101e-108e are respectively valves, and 101f-108f are respectively pressure gauges indicating the pressures in the corresponding gas bombs. 120 is a vacuum chamber fitted at its upper extremity with a pipeline for gas introduction, having a structure for formation of the reaction space downstream of the pipeline, and also having a structure for formation of a film forming space in which a substrate holder 112 is provided so that a substrate 118 may be located facing the gas discharge outlet of the pipeline. The pipeline for the gas introduction has a triple concentric structure, having from the innerside a first gas introducing pipe 109 for introducing the gases from the gas bombs 101 and 102, a second gas introducing pipe 110 for introducing the gases from the gas bombs 103-105, and a third gas introducing pipe 111 for introducing the gases from the gas bombs 106-108. As for the gas outlet to the reaction space of each gas introducing pipe, its position is designed so as to be arranged at a position further from the surface position of the substrate as the pipe is nearer to the inner side. In other words, the gas introducing pipes are arranged so that the pipe on the outer side may enclose the pipe existing within the innerside thereof. The gases from the respective bombs are fed into the respective introducing pipes through the gas feeding pipelines 123-125, respectively. The respective gas introducing pipes, the respective gas feeding pipe lines, and the vacuum chamber 120 are evacuated to vacuum through the main vacuum valve 119 by means of a vacuum evacuating device not shown in the figure. The substrate 118 is set at a suitable distance from the positions of the respective gas introducing pipes by moving the substrate holder 112 in a vertical direction. The distance between the substrate and the gas discharging outlet of each gas introducing pipe may be determined appropriately in view of the kinds and the desired characteristics of the deposited film to be formed, the gas flow rates, the inner pressure in the vacuum chamber, etc., but it is preferably from several mm to 20 cm, more preferably from about 5 mm to about 15 cm. 113 is a heater which is provided for heating the substrate to an appropriate temperature for film formation, preheating the substrate 118 prior to film formation, and annealing the film after film formation, as requisite. The heater 113 is supplied with power through a conductive wire 114 from a power source 115. 116 is a thermocouple for measuring the temperature of the substrate (Ts) and is electrically connected to a temperature display device 117. Examples will now be described and details given: Example 1 By the use of the film forming device shown in Fig. 1, a deposited film was prepared according to the process described below. The SiH₄ gas filled in the bomb 101 was introduced at a flow rate of 20 sccm through the gas introducing pipe 109, the F₂ gas filled in the bomb 103 at a flow rate of 2 sccm through the gas introducing pipe 110, and the O₂ gas filled in the bomb 106 at a flow rate of 2 sccm and the He gas filled in the bomb 108 at a flow rate of 40 sccm through the gas introducing pipe 111 into the vacuum chamber 120. During this operation, the pressure in the vacuum chamber 120 was made 100 mTorr (13.3 Pa) by controlling the opening of the vacuum valve 119. A quartz glass (15 cm × 15 cm) was used for the substrate, and the distance between the gas introducing inlet 111 and the substrate was set at 3 cm. Blueish white luminescence was strongly observed in the mixing region of SiH₄ gas, O₂ gas, and F₂ gas. The substrate temperature (Ts) was set between room temperature and 400°C for respective samples as indicated in Table 1. When gases were permitted to flow under such conditions for 3 hours, Si: O: H: F films having film thicknesses as shown in Table A-1 were deposited on the substrate. Next, when the substrate temperature was fixed at 300°C, and the flow rate of SiH₄ was varied, the respective samples prepared were found to have the film thicknesses shown in Table A-2. The gases were flowed for 3 hours for each sample, and the O₂ gas flow rate was made 2 sccm, the F₂ gas flow rate 2 sccm, and the He gas flow rate 40 sccm, and the inner pressure 100 mTorr (13.3 Pa) for each sample. Next, the substrate temperature was set at 300°C, SiH₄ gas flow rate at 20 sccm, O₂ gas flow rate at 2 sccm, F₂ gas flow rate at 2 sccm, and the inner pressure at 100 mTorr (13.3 Pa), and the He gas flow rate was varied variously. The respective samples obtained after flowing the respective gases for 3 hours were found to have the film thicknesses as shown in Table A-3. Next, the substrate temperature was set at 300°C, SiH₄ gas flow rate at 20 sccm, O₂ gas flow rate at 2 sccm, F₂ gas flow rate at 2 sccm, and He gas flow rate at 10 ccm, and the inner pressure was varied variously. The respective samples obtained were found to have the film thicknesses as shown in Table A-4. The distribution irregularity of the film thickness of the respective samples shown in Table A-1 to Table A-4 was found to be dependent on the distance between the gas introducing pipe 111 and the substrate, the gas flow rates flowed through the gas introducing pipes 109, 110, and 111, and the inner pressure. In each film formation, the distribution irregularity of film thickness could be controlled within ±5% in the substrate of 15 cm × 15 cm by controlling the distance between the gas introducing pipe and the substrate. This position was found to correspond to the position of the maximum luminescence intensity in most cases. Also, the Si: O: H: F film formed in every sample was confirmed to be amorphous by electron beam diffraction. Also, a sample for measurement of electroconductivity was prepared by vapor deposition of an aluminum comb-shaped electrode (gap length: 200 µm) on the amorphous Si: O: H: F film of each sample. Each sample was placed in a vacuum cryostat, a current of 100 V was applied and the dark electroconductivity (σd) was attempted to be determined by measuring the current by a minute amperemeter (YHP4140B). However, it was found to be lower than the measurable limit and the dark electroconductivity at room temperature was estimated to be 10 _14 s/cm or less. Example 2 The film formation was conducted by introducing N₂O₄ gas from the 107 bomb in place of the introduction of O₂ gas in Example 1 (Sample 2A). The film forming conditions in this case are as follows: Similarly as in Example 1, strong blue luminescence was observed in the region where SiH₄ gas and N₂ O₄ gas were merged into one stream. After gas blowing for 3 hours, an A-Si: N: O: H: F film of about 650 nm thickness was deposited on the quartz glass substrate. This film was found to be amorphous as confirmed by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: N: O: H: F film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 3 In Example 1, the film formation was conducted by introducing Si₂ H₆ gas from the 102 bomb in place of introducing SiH₄ gas (Sample 3A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: O: H: F film of about 1.5 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: O: H: F film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 4 In Example 1, the film formation was conducted by introducing GeH₄ gas from the 102 bomb in place of introducing SiH₄ gas (Sample 4A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Ge: O: H: F film of about 550 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Ge: O: H: F film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 5 In Example 1, the film formation was conducted by introducing GeH₄ gas from the 102 bomb simultaneously with the introduction of SiH₄ gas (Sample 5A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-SiGe: O: H: F film of about 780 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-SiGe: O: H: F film, the sample 5A was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 6 In Example 5, the film formation was conducted by introducing C₂H₄ gas from the 102 bomb in place of the introduction of GeH₄ gas (Sample 6A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-SiC: O: H: F film of about 600 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-SiC: O: H: F film, the sample 6A was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 7 In Example 1, the film formation was conducted by introducing Si₂H₆ gas from the 102 bomb simultaneously with the introduction of SiH₄ gas (Sample 7A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: O: H: F film of about 1.0 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: O: H: F film, the sample 7A was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 8 In Example 7, the film formation was conducted by introducing N₂O₄ gas from the 107 bomb in place of the introduction of O₂ gas (Sample 8A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: N: O: H: F film of about 1.0 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: N: O: H: F film, the sample 8A was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured, but it was lower than the measurable limit similarly as in Example 1. Example 9 In Example 1, the film formation was conducted by introducing SnH₄ gas from the 102 bomb in place of the introduction of SiH₄ gas (Sample 9A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an Sn: O: H: F film of about 300 nm thickness was deposited on the quartz glass substrate. This film was found to be polycrystalline, since a diffraction peak was observed as confirmed by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said poly-Sn: O: H: F film, the sample was placed in a vacuum cryostat similarly as in Example 1, and the dark electroconductivity (σd) was measured. The obtained value was as follows: σd = 8 × 10 _4 s/cm Example 10 In Example 1, the film formation was conducted by setting the substrate temperature at 600°C (Sample 10A). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an Si: O: H: F film of about 50 nm thickness was deposited on the quartz glass substrate. This film was found to be polycrystalline, since a diffraction peak of SiO₂ was observed when measured by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said poly-Si: O: H: F film, the sample 10A was placed in a vacuum cryostat similarly as in Example 1, and the dark electroconductivity (σd) was measured, but it was found to be lower than the measurable limit similarly as in Example 1. Example 11 In Example 1, the film formation was conducted by introducing Cl₂ gas from the 104 bomb simultaneously with the introduction of F₂ gas (Sample 11A). The film forming conditions in this case are as follows: Similarly as in Example 1, strong blue luminescence was observed in the region where SiH₄ gas, F₂ gas, Cl₂ gas, and O₂ gas were merged into one stream. After gas blowing for 3 hours, an A-Si: O: H: F: Cl of about 800 nm thickness was deposited on the quartz substrate. This film was confirmed to be amorphous by the electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said A-Si: O: H: F: Cl film, the sample was placed in a vacuum cryostat similarly as in Example 1, and dark electroconductivity (σd) was measured, but it was found to be lower than the measurable limit similarly as in Example 1. Example 12 In Example 1, the film formation was conducted by introducing Cl₂ gas from the 104 bomb in place of the introduction of F₂ gas (Sample 12A). The film forming conditions in this case are as follows: Similarly as in Example 1, in the region where SiH₄ gas, Cl₂ gas, and O₂ gas were merged into one stream, strong blue luminescence was observed. After gas blowing for 3 hours, an A-Si: O: H: F: Cl film of about 300 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said A-Si: O: H: F: Cl film, the sample 12A was placed in a vacuum cryostat similarly as in Example 1, and the dark electroconductivity (σd) was measured, but it was found to be lower than the measurable limit similarly as in Example 1. Example 13 By the use of the film forming device shown in Fig. 1, a deposited film was prepared as described below. The SiH₄ gas filled in the bomb 103 was introduced at a flow rate of 20 sccm and the B₂H₆ gas (diluted to 1% with H₂) filled in the bomb 104 at a flow rate of 2 sccm through the gas introducing pipe 110, the F₂ gas filled in the bomb 101 at a flow rate of 2 sccm through the gas introducing pipe 109, and the O₂ gas filled in the bomb 106 at a flow rate of 2 sccm and the He gas filled in the bomb 108 at a flow rate of 40 sccm through the gas introducing pipe 111 into the vacuum chamber 120. During this operation, the pressure in the vacuum chamber 120 was made 100 mTorr (13.3 Pa) by controlling the opening of the vacuum valve 119. A quartz glass (15 cm × 15 cm) was used for the substrate, and the distance between the gas introducing inlet 111 and the substrate was set at 3 cm. Blueish white luminescence was strongly observed in the mixing region of SiH₄ gas, O₂ gas, and F₂ gas. The substrate temperature (Ts) was set between room temperature and 400°C for respective samples as indicated in Table B-1. When gases were permitted to flow under such conditions for 3 hours, Si: O: H: F: B films having film thicknesses as shown in Table B-1 were deposited on the substrate. Next, when the substrate temperature was fixed at 300°C, and the flow rate of SiH₄ was varied, the respective samples prepared were found to have the film thicknesses shown in Table B-2. The gases were flowed for 3 hours for each sample, and the O₂ gas flow rate was made 2 sccm, the F₂ gas flow rate 2 sccm, and the He gas flow rate 40 sccm, and the inner pressure 100 mTorr for each sample. Next, the substrate temperature was set at 300°C, SiH₄ gas flow rate at 20 sccm, O₂ gas flow rate at 2 sccm, F₂ gas flow rate at 2 sccm, and the inner pressure at 100 mTorr (13.3 Pa), and the He gas flow rate was varied variously. The respective samples obtained after flowing the respective gases for 3 hours were found to have the film thicknesses as shown in Table B-3. Next, the substrate temperature was set at 300°C, SiH₄ gas flow rate at 20 sccm, O₂ gas flow rate at 2 sccm, F₂ gas flow rate at 2 sccm, and He gas flow rate at 10 sccm, and the inner pressure was varied variously. The respective samples obtained were found to have the film thicknesses as shown in Table B-4. The distribution irregularity of the film thickness of the respective samples shown in Table B-1 to Table B-4 was found to be dependent on the distance between the gas introducing pipe 111 and the substrate, the gas flow rates flowed through the gas introducing pipes 109, 110, and 111, and the inner pressure. In each film formation, the distribution irregularity of film thickness could be controlled within ±5% in the substrate of 15 cm × 15 cm by controlling the distance between the gas introducing pipe and the substrate. This position was found to correspond to the position of the maximum luminescence intensity in most cases. Also, the Si: O: H: F: B film formed in every sample was confirmed to be amorphous by electron beam diffraction. Also, a sample for measurement of electroconductivity was prepared by vapor deposition of an aluminum comb-shaped electrode (gap length: 200 µm) on the amorphous Si: O: H: F: B film of each sample. Each sample was placed in a vacuum cryostat, a current of 100 V was applied and the dark electroconductivity (σd) was attempted to be determined by measuring the current by a minute amperemeter (YHP4140B). The results are shown in Table B-1 to Table B-4. Every sample exhibited P type by the measurement of thermal electromotive force. Example 14 The film formation was conducted by introducing N₂O₄ gas from the 107 bomb in place of the introduction of O₂ gas in Example 13 (Sample 2B). The film forming conditions in this case are as follows: Similarly as in Example 13, strong blue luminescence was observed in the region where SiH₄ gas and N₂O₄ gas were merged into one stream. After gas blowing for 3 hours, an A-Si: N: O: H: F: B film of about 700 nm thickness was deposited on the quartz glass substrate. This film was found to be amorphous as confirmed by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: N: O: H: F: B film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured similarly as in Example 13 to obtain a value of 3 × 10 _8 s/cm. The film was found to be P type by the measurement of thermal electromotive force. Example 15 In Example 13, the film formation was conducted by introducing Si₂H₆ gas from the 105 bomb in place of introducing SiH₄ gas (Sample 3B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: O: H: F: B film of about 1.56 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: O: H: F: B film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured to obtain σd = 8 × 10 _9 s/cm. The film was also confirmed to be P type by the measurement of thermal electromotive force. Example 16 In Example 13, the film formation was conducted by introducing GeH₄ gas from the 105 bomb in place of introducing SiH₄ gas (Sample 4B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Ge: O: H: F: B film of about 600 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Ge: O: H: F: B film, the sample was placed in a vacuum cryostat to obtain a dark electroconductivity (σd) of 4 × 10 _9 s/cm. The film was confirmed to be P type by the measurement of thermal electromotive force. Example 17 In Example 13, the film formation was conducted by introducing GeH₄ gas from the 105 bomb simultaneously with the introduction of SiH₄ gas (Sample 5B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-SiGe: O: H: F: B film of about 770 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-SiGe: O: H:F: B film, the sample 5B was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured to obtain a value of 3 × 10 _8 s/cm. The film was confirmed to be P type by the measurement of thermal electromotive force. Example 18 In Example 17, the film formation was conducted by introducing C₂H₄ gas from the 102 bomb in place of the introduction of GeH₄ gas (Sample 6B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-SiC: O: H: F: B film of about 650 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-SiC: O: H: F: B film, the sample 6B was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured to obtain a value of 3 × 10 _10 s/cm. The film was also confirmed to by P type by the measurement of thermal electromotive force. Example 19 In Example 13, the film formation was conducted by introducing Si₂H₆ gas from the 105 bomb simultaneously with the introduction of SiH₄ gas (Sample 7B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: O: H: F: B film of about 1.2 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: O: H: F: B film, the sample 7B was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured to obtain a value of 2 × 10 _8 s/cm. The film was confirmed to be P type by the measurement of thermal electromotive force. Example 20 In example 19, the film formation was conducted by introducing N₂O₄ gas from the 107 bomb in place of the introduction of O₂ gas (Sample 8B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an A-Si: N: O: H: F: B film of about 1.1 µm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on the A-Si: N: O: H: F: B film, the sample 8B was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured to be 3 × 10 _10 s/cm. The film was confirmed to be P type by the measurement of thermal electromotive force. Example 21 In Example 13, the film formation was conducted by setting the substrate temperature at 600°C (Sample 9B). The film forming conditions in this case are as follows: After gas blowing for 3 hours, an Si: O: H: F: B film of about 600 nm thickness was deposited on the quartz glass substrate. This film was found to be polycrystalline, since a diffraction peak of SiO₂ was observed when measured by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said poly-Si: O: H: F: B film, the sample 10B was placed in a vacuum cryostat similarly as in Example 1, and the dark electroconductivity (σd) was measured to be 3 × 10 _9 s/cm. Also, the film was confirmed to be P type by the measurement of thermal electromotive force. Example 22 In Example 13, the film formation was conducted by introducing Cl₂ gas from the 102 bomb simultaneously with the introduction of F₂ gas (Sample 10B). The film forming conditions in this case are as follows: Similarly as in Example 13, strong blue luminescence was observed in the region where SiH₄ gas, F₂ gas, Cl₂ gas, and O₂ gas were merged into one stream. After gas blowing for 3 hours, an A-Si: O: H: F: Cl: B of about 850 nm thickness was deposited on the quartz substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said A-Si: O: H: F: Cl: B film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured similarly as in Example 13 to obtain a value of 3 × 10 _9 s/cm. The film was confirmed to be P type by measurement of thermal electromotive force Example 23 In Example 13, the film formation was conducted by introducing PH₃ gas from the 104 bomb in place of the introduction of B₂H₆ gas (Sample 11B). The film forming conditions in this case are as follows: Similarly as in Example 13, in the region where SiH₄ gas, F₂ gas, and O₂ gas were merged into one stream, strong blue luminescence was observed. After gas blowing for 3 hours, an A-Si: O: H: F: P film of about 600 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction. After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said A-Si: O: H: F: P film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured similarly as in Example 13, to obtain a value of 3 × 10 _8 . The film was confirmed to be N type by the measurement of thermal electromotive force. Example 24 In Example 23, the film formation was conducted by introducing Cl₂ gas from the 102 bomb in place of the introduction of F₂ gas (Sample 12B). The film forming conditions in this case are as follows: Similarly as in Example 13, in the region where SiH₄ gas, Cl₂ gas, and O₂ gas were merged into one stream, strong blue luminescence was observed. After gas blowing for 3 hours, an A-Si: O: H: Cl: P film of about 280 nm thickness was deposited on the quartz glass substrate. This film was confirmed to be amorphous by electron beam diffraction After an aluminum comb-shaped electrode (gap length 200 µm) was vapor deposited in vacuo on said A-Si: O: H: Cl: P film, the sample was placed in a vacuum cryostat, and the dark electroconductivity (σd) was measured similarly as in Example 13 to obtain a value of 4 × 10 _8 s/cm. Also, the film was confirmed to be N type by the measurement of thermal electromotive force. As can be seen from the detailed description and the respective examples as set forth above, deposited films having uniform physical properties over a large area can be obtained with easy control of film quality at the same time as achievement of energy saving. Also, it is possible to obtain easily films excellent in productivity, bulk productivity, having high quality with excellent physical properties such as electrical, optical and semiconductor properties, etc.

Claims: 1. A method for forming a deposited film, which comprises introducing a gaseous starting material for formation of a deposited film, a gaseous halogenic oxidizing agent (X) having the property of oxidation action on said starting material, and at least one gaseous oxidizing agent selected from oxygen containing or nitrogen containing oxidizing agents having this same property, into a reaction space to effect chemical contact among them to thereby form a plural number of precursors containing one or more precursors in an excited state, and forming a deposited film on a substrate existing in the film forming space using at least one amongst these precursors as the feeding source for a constitutent element of the deposited film. 2. A method for forming a deposited film, which comprises introducing a gaseous starting material for formation of a deposited film, a gaseous halogenic oxidizing agent (X) having the property of oxidation action on said starting material, at least one gaseous oxidizing agent selected from oxygen containing or nitrogen containing oxidizing agents, and a gaseous material (D) containing a component to act as an active dopant constitutent in the film, into a reaction space to effect chemical contact among them to thereby form a plural number of precursors containing one or more precursors in an excited state, and forming a deposited film on a substrate existing in the film forming space using at least one amongst these precursors as the feeding source for a constituent element of the deposited film. 3. A method according to either of the preceding claims wherein said gaseous halogenic oxidizing agent (X) comprises a halogen gas. 4. A method according to claim 3, wherein said gaseous halogenic oxidizing agent (X) comprises fluorine gas. 5. A method according to either of claims 3 or 4, wherein said gaseous halogenic oxidizing agent (X) comprises chlorine gas. 6. A method according to any preceding claim wherein said gaseous halogenic oxidizing agent (X) contains fluorine atoms as a constituent. 7. A method according to any preceding claim, wherein said gaseous halogenic oxidizing agent (X) contains a halogen in nascent state. 8. A method according to any preceding claim, wherein formation of the deposition film is accompanied by luminescence. 9. A method according to any preceding claim, wherein said gaseous starting material comprises a chain silane compound. 10. A method according to claim 9, wherein said chain silane compound is a straight chain silane compound. 11. A method according to claim 10, wherein said straight chain silane compound is represented by the formula Si n H 2n + 2 wherein n is an integer of 1 to 8. 12. A method according to claim 9, wherein said chain silane compound is a branched chain silane compound. 13. A method according to any of claims 1 to 8, wherein said gaseous starting material comprises a silane compound having a cyclic silicon structure. 14. A method according to any of claims 1 to 8, wherein said gaseous starting material comprises a chain germanium compound. 15. A method according to claim 14, wherein said chain germanium compound is represented by the formula Ge m H 2m + 2 wherein m is an integer of 1 to 5. 16. A method according to any of claims 1 to 8, wherein said gaseous starting material comprises a hydrogenated tin compound. 17. A method according to any of claims 1 to 8, wherein said gaseous starting material comprises a tetrahedral type compound. 18. A method according to any preceding claim, wherein said gaseous oxidizing agent (ON) comprises an oxygen compound. 19. A method according to any preceding claim, wherein said gaseous oxidizing agent comprises an oxygen gas. 20. A method according to any of claims 1 to 17, wherein said gaseous oxidizing agent comprises a nitrogen compound. 21. A method according to any preceding claim, wherein said substrate is arranged facing towards the direction in which said gaseous starting material and said gaseous oxidizing agent are introduced into said reaction space. 22. A method according to claim 21, when dependent on claim 2, wherein the gaseous oxidizing agent (X) and gaseous material (D) are also introduced into the reaction space and directed towards the substrate. 23. A method according to any preceding claim, wherein said gaseous starting material and said gaseous oxidizing agent are introduced into said reaction space through a transporting pipe of multi-tubular structure. 24. A method as claimed in claim 23 when dependent on claim 2, wherein the gaseous oxidizing agent (X) and gaseous material (D) are also introduced into the reaction space through the transporting pipe.

Inventors: HANNA, JUNICHI, ISHIHARA, SHUNICHI, SHIMIZU, ISAMU
Applicants: CANON KABUSHIKI KAISHA
Application year: 1986
Main classification: C23C16
IPC codes: H01L21, C23C16