JPS6361388B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing electrically conductive layers that are highly transparent to visible light and highly reflective to infrared radiation, and particularly advantageous coatings formed by the method. Such layers are useful as transparent electrodes for solar cells, photoconductor tubes, liquid crystal electro-optic displays, photoelectrochemical cells, and many other types of opto-electronic devices. Such layers are used as transparent electrical resistors for defrosting airplane and automobile windows. Such layers increase the efficiency of windows and fiberglass insulation in solar thermal integrators and buildings, ovens, furnaces and sodium vapor lamps as heat-reflective transparent coatings on glass. Various metal oxides such as stannic oxide SnO ₂ , indium oxide In ₂ O ₃ and cadmium stannate Cd ₂ SnO ₄ have been most widely used as materials for forming transparent conductive coatings and layers. . Current methods of applying these coatings have been based on spraying metal salt (usually chloride) solutions onto heated surfaces such as glass. This method first produced a transparent electrically resistive layer that was satisfactory for dewatering airplane windows. However, this method of atomization produced rather corrosive byproducts, namely hot chlorine and hydrogen chloride gases, which tended to attack the hot glass surface and give it a foggy appearance. US Pat. No. 2,617,745 teaches that such undesirable effects can be alleviated by first applying pure silica on the glass. However, the silica protective layer is not so effective for glasses with high alkali content and high coefficient of thermal expansion, such as common soda-lime glasses. Additionally, these corrosive by-products corrode the metal parts of the device, and metallic impurities such as iron can then precipitate into the coating, adversely affecting both the conductivity and transparency of the coating. vinegar. Another problem is the lack of coating uniformity and reproducibility. In US Patent No. 2,651,585,
It has been taught that better uniformity and reproducibility can be achieved by controlling the humidity within the device. More uniform and reproducible coatings are also obtained by using steam rather than liquid spray, as disclosed for example in German Patent No. 1,521,239. Despite these improvements, recent research has been conducted using vacuum deposition techniques such as vapor and evaporation to obtain brighter and more reproducible coatings. Although such vacuum processing is very costly, reducing corrosive by-products and undesirable impurities produced by atomization methods is considered particularly important in applications involving high-purity semiconductors. ing. In order to obtain high electrical conductivity and high infrared reflectance with this method, it is important to intentionally add certain impurities. Thus, tin impurities are added to indium oxide, while antimony is added to tin oxide (stannic oxide) for this purpose. In each case, the function of such desirable impurities or "doping agents" is to provide "extra" electrons that contribute to conductivity. The solubility of these impurities is high;
And these impurities can be easily added using all of the precipitation methods described above. Fluorine is more advantageous than antimony as a doping agent for tin oxide, in which case the transparency of the fluorine-doped stannic oxide film is greater than that of the antimony-doped one, especially in the visible spectrum. Excellent at the red end. This advantage of fluorine is important for applications in solar cells and solar thermal integrators. Despite these advantages of fluorine, most, perhaps all, industrially available tin oxide coatings use antimony as a doping agent. Perhaps the reason for this is that doping with fluorine has only been experimented with unsatisfactory spray methods, while improved deposition methods (chemical vapor deposition,
Vacuum evaporation. evaporation) has not previously been shown to result in fluorine doping. In addition, The American Institute
The American Institute of Physics Conference Proceedings
Physics Conference Proceedings) No. 25, p.
288 (1975) concluded that the equilibrium solubility of fluorine in tin oxide is inherently lower than that of antimony. Nevertheless, it has been found that the lowest resistance tin oxide film reported in the prior art is that of Gillery, US Pat. No. 3,677,814. Gillery uses a spray method and a compound in which tin and fluorine are directly bonded as starting materials to obtain fluorine-doped tin oxide films with resistances as low as 15 Ω/□. The lowest resistance of industrially available tin oxide coated glass is currently about 40Ω/□. Achieving coverages as low as 10 Ω/□ has so far required the use of significantly more expensive materials such as indium oxide. A first object of the present invention is to provide a method for depositing a fluorine-doped stannic oxide layer, i.e. a stannic oxide coating, which has high visible light transmission, high electrical conductivity and high infrared reflection power. It is to provide. A second object of the present invention is to be able to easily vary the electrical conductivity of a single layer of the above-mentioned layers during deposition, and to have the ability to achieve very low volume resistivities and surface resistivities. That's true. A third object of the present invention is to create a non-corrosive deposition atmosphere, from which a highly pure layer such as the one described above can be easily deposited, and to prevent contamination of the substrate with impurities or the formation of a substrate or equipment. The objective is to provide a deposition atmosphere that does not corrode the materials. A fourth object of the present invention is to provide a gaseous rather than liquid means for making coated products as disclosed herein. A fifth object of the invention is to provide a method for easily forming such a layer that is highly uniform and reproducible over large areas and without the limitations inherent in spraying operations. A sixth object of the present invention is to easily deposit such a layer inside pipes and valves, or on complex-shaped surfaces that cannot be easily sprayed. A seventh object of the invention is to provide improved articles such as solar cells, other semiconductors useful in electrical circuits, heat reflective windows, improved sodium lamps, and the like. An eighth object of the invention is to enable the deposition of such layers by standard manufacturing methods in the semiconductor and glass industries. Other objects and advantages of the invention will become apparent from the following description. A feature of the present invention is that the reactants are selected so that the necessary tin-fluorine bond is not formed until immediately before precipitation. The tin fluoride material can then be maintained well enough in the vapor phase and at temperatures low enough that oxidation of the compound occurs only after rearrangement to form the tin-fluorine bond. The fluorine-doped tin oxide thus formed has an unusually low electrical resistivity and an unusually high reflectivity for infrared wavelength light. The process of the invention is carried out using a gaseous mixture containing a volatile organotin-fluorine-containing compound that does not have any direct tin-fluorine bond. This mixture also contains volatile oxidizable tin compounds and oxidizing gases. This first fluorine compound without a fluorine-tin bond is converted into a second organotin fluoride compound having a fluorine-tin bond. Immediately after such conversion, the second compound is oxidized to form a fluorine doping agent, and the dopant is oxidized with an oxidizable tin compound to deposit a predetermined amount of fluorine on the solid substrate. A stannic oxide film containing impurities is formed. In a first embodiment of the invention, an organotin monofluoride vapor is produced by regenerating a vapor of a more volatile compound containing both tin and a fluoroalkyl group attached to tin in a heated precipitation zone. In a second advantageous embodiment of the invention, by a reaction involving an organotin vapor and certain fluorine-containing gases having fluoroalkyl and/or sulfur fluoride groups at or near the gas-substrate interface. Utilize the formed organotin monofluoride. The resulting layer in either case is a uniform, hard-adhered, transparent film whose electrical conductivity and infrared reflectance vary depending on the concentration of the fluorine-containing doping agent. The method of the invention has two main steps.
The first step is to form a reactive vapor mixture that upon heating produces a compound with tin-fluorine bonds, and the second step is to transfer this vapor mixture to a heated surface and to form a reactive vapor mixture that produces a compound having a tin-fluorine bond. This is a process in which tin oxide doped with fluorine is precipitated. The embodiments described below differ in the chemical source of the fluorine doping agent in the reactive vapor mixture, as well as in the means of making the vapor mixture. The second step (deposition on the heated surface) is almost identical in each example. Tin is provided by volatile oxidizable tin compounds such as tetramethyltin, tetraethyltin, dibutyltin diacetate, dimethyltin dihydride, dimethyltin dichloride, and the like. Tetramethyltin is a preferred compound because it is sufficiently volatile at room temperature, noncorrosive, stable, and easy to purify. The volatile tin compound is placed in a bubbler, shown at 10 in the figure, and an inert carrier gas, such as nitrogen, is bubbled through the tin compound. For highly volatile compounds such as tetramethyltin and dimethyltin dihydride, this bubbler may be used at room temperature, whereas for other less volatile compounds,
The bubbler and its tubing must be heated appropriately, as will be apparent to those skilled in the art. One advantage of the present invention is that there is no need to use high temperature equipment and that a simple cold wall feeder can be used. The vapor mixture must contain an oxidizing gas such as oxygen, nitrous oxide, etc. Oxygen is a preferred gas because it is readily available, works well, and can replace more expensive oxidizing agents. The pressure of the gas is kept constant by a regulator 25, and the flow rate of oxygen from tank 20 and carrier gas from tank 21 is regulated by a metering valve 30 and measured by a flowmeter 40. This gas stream is then transferred through a one-way tick valve 50 to a mixing tube 60 and a furnace-shaped chamber 70. A tin oxide film is deposited on the hottest surface 80. This surface is heated by heater 90 to a temperature typically between about 400°C and 600°C. Methods of the general type described above are commonly known in the art as chemical vapor deposition. Various modifications are also known to those skilled in the art, such as having a vertical and rotating substrate surface or rotating beneath the reaction chamber, and such modifications may affect the geometry of the substrate or the intended use. Particularly suitable for use depending on other conditions. It is better to rotate the substrate in order to move it sufficiently into the convection currents that may occur within the device.
By doing so, the most uniform deposited layer can be obtained. However, the inventors have discovered that by positioning the heated substrate facing downward, a highly uniform coating can be obtained more easily and without rotating the substrate. The reason for this is that when heated as described above, the gas does not cause troublesome convection. Placing the substrate above the reaction vapors has the additional advantage that dust, the product of uniform nucleation in the gas, does not fall onto the growing film. The present invention is an improved method by which a predetermined amount of fluorine impurity can be introduced into a growing tin oxide film. In the simplest embodiment of the invention, the fluorine doping agent is a vapor containing one tin-fluorine bond in each molecule. The other three valencies of tin are filled by organic groups and/or halogens other than fluorine. A typical example of such a compound is tributyltin fluoride. The fluorine thus bound and available in vapor form to the hot surface does not separate from the tin during oxidation at the hot surface. Unfortunately, all known compounds with such a direct tin-fluorine bond are not sufficiently volatile near room temperature. A particular advantage of the present invention is that by forming the fluorine doping agent from a volatile compound that does not have the necessary tin-fluorine bonds, but which, upon heating, rearranges to form a direct tin-fluorine bond. can be achieved. This rearrangement advantageously occurs at sufficiently high temperatures (e.g. above 100°C), so that the fluorine fluoride thus obtained remains in the vapor phase and also advantageously occurs at sufficiently low temperatures (e.g. below 400°C). So,
Oxidation of this compound occurs only after rearrangement. One example _of such a compound is trimethyltrifluoromethyltin ( _CH3 ) _3SnCF3 . When this compound is heated to a temperature of about 150° C. in a heated region adjacent to the precipitation surface 80, it rearranges to _{form tin-}
A direct bond of fluorine occurs, and this compound (CH ₃ ) ₃ SnF then reacts as a fluorine donor or fluorine doping agent. Other compounds that undergo similar rearrangements at different temperatures, of course, vary from compound to compound, but have the general formula R ₃ SnRF, where R is a hydrocarbon group and RF is The main advantage of these fluorine doping agents is that these compounds are volatile liquids and therefore Sufficient vapor pressure can be easily obtained when evaporating at room temperature. These advantages eliminate the need to heat the region between bubbler 15 and reaction chamber 70 to keep the fluorine dopant in the vapor phase, as shown in FIG. It gets easier. The apparatus may thus be of the type commonly referred to as a "cold wall chemical vapor deposition reactor." This type of equipment is widely used in the semiconductor industry for depositing silicon, silicon dioxide, silicon nitride, etc., for example.
Another important feature of this "cold wall reactor" for semiconductor applications is the ability to minimize low concentrations of unwanted impurities in both the substrate and the deposited film. Similarly, in glass manufacturing, this gas mixture can be added to annealing and cooling furnaces at a stage when the glass is at a suitable temperature, for example about 470° C. for soft glasses. In this way, highly uniform films can be obtained within conventional glass manufacturing equipment. A preferred compound for use in the embodiment of FIG. 1 is (CH ₃ ) ₃ SnCF ₃ because this compound is more volatile than compounds with more carbon atoms. This compound is a stable, colorless, non-corrosive liquid that does not decompose in air at room temperature and
It only reacts extremely slowly with water. A second particularly advantageous embodiment of the invention uses a fluorine-containing gas which, when heated, reacts with the organotin vapor to form a tin fluoride vapor. For example, α-fluoroalkyl hydrides whose alkyl group preferably has 4 or fewer carbon atoms, such as gases such as iodotrifluoromethane CF ₃ l, CF ₃ CF ₂ l, C ₃ H ₇ l, etc. Organic tin vapors such as tetramethyltin vapor (CH ₃ ) ₄ Sn and room temperature, i.e.
32.2°C (90〓), and more preferably 65.6°C
Can be mixed without reaction at temperatures up to (150〓). Furthermore, fluoroalkyl bromides such as CF ₃ Br and C ₂ F ₅ Br are also useful as fluorine-containing gases. These gases are less reactive and require about 10 to 20 times more in the reactant gas, but on the other hand they are very cheap. This is particularly surprising since it is common knowledge that such compounds are inert. Fluoroalkyl chlorides are not preferred because their reactivity is substantially lower than even bromides. When a vapor mixture as described above approaches a heated surface, a reaction takes place in the gas phase, eventually producing the desired tin-
A fluorine bond occurs. Although the reaction sequence is complex, it starts with a reaction such as CF ₃ l + R ₄ Sn → R ₃ SnCF ₃ + Rl, producing organotin fluoroalkyl R ₃ SnCF ₃ vapor in the region near the interface of the hot surface.
It is therefore believed that these compounds serve as fluorine doping agents for the growing tin oxide film just as in the first embodiment. Certain other fluorine-containing gases also work in the second embodiment of the invention. For example, sulfur pentafluoride monochloride SF ₅ Cl is an effective fluorine donor gas, as is sulfur pentafluoride monobromide. Similarly, trifluoromethyl sulfur pentafluoride acts to form tin-fluorine bonds through gas phase reactions. An advantage of this second embodiment is that the fluorine donor is a gas, and the process is further illustrated in FIG. Preferred gases are CF ₃ l and CF ₃ Br,
These gases are non-corrosive, non-flammable, have no appreciable toxicity and are readily available commercially. SF ₅ Cl and SF ₅ Br are highly toxic and therefore less desirable to use.
CF ₃ SF ₃ is non-toxic but somewhat less reactive than CF ₃ l. The deposition process can be further simplified if the gas mixture is premixed and stored in a compressed gas cylinder 19, as shown in FIG. Store safely;
And in order to use the above oxidizable compound,
Of course, the concentration must be kept at such a level that it does not result in an explosive mixture. For example, the lower explosive limit for tetramethyltin in air is approximately 1.9%. The concentration used for chemical vapor deposition is less than half of the above concentration.
Furthermore, if CF ₃ I or CF ₃ Br are used as fluorine doping agents, they also act concomitantly as anti-inflammatory agents. It has been found that the film prepared according to the present invention has an infrared reflectance of 90% or more. This reflectivity is measured at room temperature with a typical 10 micron wavelength of light characterized by thermal infrared radiation, as is known in the art. This 90% reflectivity is superior to the 80% reflectivity previously achieved using tin oxide coatings. In normal practice, these infrared reflective layers have a thickness of 0.2 to 1 micron, with a thickness of 0.3 to 0.5 micron being typical. In addition, the fluorine:oxygen ratio in the film
It is preferable to use a value between 0.007 and 0.03. In order to more quantitatively identify the degree of fluorine doping in the film, its infrared reflectance was measured over a wavelength range of 2.5 microns to 40 microns. "Optical Effects of Free Carriers in SnO ₂ Layers _"
Zeitsschrift fur
Naturforschung), Vol. 179. pp. 789-793 (1962)
In R. Groth, E. Kauer and PC Huang. Den. By fitting these data to the theoretical curve detailed by vanden Linden, a value for the free electron concentration in the film was determined. The values obtained were in the range 10 ²⁰ cm ⁻³ to 10 ²¹ cm ⁻³ and increased regularly with increasing concentration of fluorine dopant. Theoretically, one free electron should be released for each fluorine atom that replaces oxygen in the lattice. This hypothesis is
This was demonstrated by electronic spectrometry of the total fluorine concentration in Auger's film. This measurement yielded free electron concentrations and fluorine concentrations that agreed within experimental error. This agreement indicates that most of the fluorine included is electroactive. It has been found that the infrared reflectance and volume conductivity at 10 microns of this film are maximum at doping levels that substitute about 1.5-2% fluorine for oxygen. This maximum value is very broad, and almost maximum conductivity and reflectivity are exhibited by films containing 1% to 2.5% fluorine. These films also exhibit weak and broad absorption over visible wavelengths. Therefore, a fluorine concentration in the film of about 1% (ie, a fluorine:oxygen ratio in the film of 0.01) is most desirable to produce a film with high conductivity and high visible light transparency. However, this optimality varies somewhat depending on the spectral distribution desired in a given application. By varying the fluorine dopant concentration, the optimum percentage for any given application can be easily achieved by routine experimentation. Fluorine doping levels of 3% or more can be easily achieved in films using the method of the present invention. The results of the prior art did not exceed 1%.
The view cited earlier was that the cause of this was the solubility limit of fluorine. Although such high doping levels are not necessary for optimal infrared reflectivity or conductivity, gray films made at doping levels of 2% or higher can be used to reduce solar heat capture during air conditioning buildings. It is useful as architectural glass. In such applications, it is advantageous to reduce the doping level at the film surface to about 2% to have maximum infrared reflectance. Using the measured electron concentration and conductivity, the electron flow mobility can be obtained. Using this method, values of 50-70 cm ² /volt-sec. were calculated for various films. The mobility of the conventionally obtained tin oxide film is 5
~35 cm ² /volt-sec. It is believed that the film according to the invention is the first to have a mobility exceeding 40 cm ² /volt-sec. In other words, such values are indicative of the excellent quality of the method of the present invention and the films prepared thereby. The method of the invention is also highly desirable for the manufacture of new devices in semiconductor manufacturing, such as those having electrically conductive layers (eg, integrating circuits, etc.), and for the manufacture of heat-reflective transparent articles such as windows. The most advantageous embodiment of the invention is that the organotin fluoride compound having a tin-fluorine bond is decomposed on the substrate immediately after its formation. This decomposition is preferably carried out in a small reaction zone which is sufficiently heated to the decomposition temperature by heat from the substrate itself. In order to more fully point out the features of the invention, the following examples are given to illustrate embodiments of the invention and the products obtained thereby. Unless otherwise indicated, the specific examples disclosed below were carried out in accordance with the following general procedure. Example 1 Using the apparatus of Figure 1, 1% tetramethyltin ( _CH3 ) _4Sn , 0.02% trimethyltrifluoromethyltin ( _CH3 ) _{3SnCF3 ,} 10% nitrogen carrier gas and the balance The invention is illustrated by an experiment in which a gas stream containing . The resulting gas stream is passed over a 15 cm diameter Pyrex glass plate maintained at 500° C. for a precipitation period of about 5 minutes. The flow rate of this gas stream is approximately 400 c.c./min. This flow rate is such that the gas circulation rate in the furnace 70 is once every two minutes. A transparent film about 1 micron thick was deposited. It exhibits an electrical resistance of 2 ohms/□, which corresponds to a volume resistivity of 0.0002 ohm-cm. The film was measured to have a fluorine:oxygen ratio of 0.017 and a flow mobility of 50 cm ² /volt-pec. Example 2 When the method of Example 1 was repeated using a sodium-free silicon substrate, the resistance value was reduced to about 1 ohm/□, or about half the resistivity obtained for the sodium-containing substrate. . Embodiment 3 A more advantageous method using the apparatus shown in FIG. 2 will be described. The resulting gas mixture consisted of 1% tetramethyltin (CH ₃ ) ₄ Sn, 0.2% iodotrifluoromethane CF ₃ I, 20% nitrogen carrier gas, and the remaining amount oxygen. Films grown on Pyrex glass substrates exhibited the same electrical properties as in Example 1. Example 4 Using the simplified apparatus shown in FIG. 3, the mixture described in Example 3 was prepared in a compressed gas cylinder 19. The results are the same as those of Example 3.
After one month of storage in a gas cylinder, the experiment was repeated with identical results. This indicates the stability and shelf life of this mixture. Example 5 Example 3 was repeated except that the deposition was stopped when the stannic oxide film was 0.5 microns thick. The obtained stannic oxide film is about 90%
It had an infrared reflectance of . Examples 6-13 Each of the following gases was used in the procedure of Example 3.
Instead of CF ₃ I, substitution was made at the equimolar ratio (however,
The concentration of fluorine doping agent was increased by a factor of 15 in Examples 6, 7, 8 and 13. ). Excellent electrical conductivity and infrared reflection ability were obtained.

[Table] Conventional silicon photovoltaic cells (solar cells) have traditionally had a surface resistance of typically 50-100 ohms/□. In order to have an acceptably low total cell resistance, metal grids with a spacing of 1 or 2 mm are deposited on the silicon surface. By depositing a fluorine-doped tin oxide layer with a sheet resistance of about 0.5 ohm/□ (about 2 microns thick) on the cell surface, the metal grid spacing can be increased to about 10 mm, which increases the grid spacing. Costs can be lowered. On the other hand, the grid size can be kept small and the cell can function effectively even if the sunlight is concentrated by a factor of about 100, provided the cell is kept properly cooled. A schematic cross section 100 of the above cell is shown in FIG. This figure shows a 2 micron N.SnO ₂ layer 10
2 (using the fluorine-doped material of the present invention), 0.4Z micron n-silicon layer 10
4 (conventionally known silicon doped with phosphorus),
A 0.1 mm p-silicon layer 106 (conventionally known fluorine silicon) is connected to an aluminum layer 108 which serves as an electrode. metal grid 11
0 has an interval of about 10 mm. Nevertheless, outstanding implementation effects can be achieved. The deposited layers can be used in the production of other semiconductor articles, such as conductors and resistors.
Tin oxide coatings have traditionally been used in integration circuits in this manner. Improving the electrical conductivity will make this material more versatile in the future. Not only has this sheet resistance range been extended to much lower values than previously possible (e.g., about 5 ohms/□ or less), but the deposition of that layer can also be used to grow epitaxial silicon, for example. This can be done in the same equipment as the This eliminates costly and complicated unloading, cleaning and mounting steps during deposition. Resistivity values obtained for fluorine-doped tin oxide on a silicon substrate are approximately ^10-4-4 ohm-cm, which is comparable to that of evaporated tantalum metal. This tantalum metal is sometimes used for connections in integrating circuits. Since the thermal expansion coefficients of both tin oxide and silicon are in good agreement,
Deposition of thick layers is possible without significant distortion. FIG. 6 shows the electrical conductivity of a fluorine-doped stannic oxide film as a function of the fluorine:oxygen ratio measured in the film for deposition temperatures of 80°C and 500°C. FIG. 7 shows the infrared reflectance of a fluorine-doped film as a function of the fluorine:oxygen ratio measured in the film for deposition temperatures of 480°C and 500°C. Figures 6 and 7 show (1) conventionally known and ``Philips Technical Review''.
(2) doped indium oxide materials, such as those described by Van Boort and Groth in "Technical Review" Vol. 29, p. 17 (1968); and (2) doped indium oxide materials. The best known prior art values for the conductivity and reflectivity of ditin coatings are also shown. While several embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications and changes may be made to the invention without departing from the spirit of the invention or the scope of the following claims. It's quite obvious.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of an apparatus suitable for carrying out a process in which the fluorine doping agent is an organotin fluoroalkyl vapor and is evaporated from its liquid state. FIG. 2 shows a similar schematic for a second embodiment in which a fluorine doping agent is formed by reacting with certain fluoroalkyl and/or sulfur fluoride gases supplied from a compressed gas cylinder. FIG. 3 shows a simplified variant of the device for carrying out either the first or second embodiment of the invention. FIG. 4 is a schematic cross-sectional view of a solar cell, and one embodiment of the present invention in semiconductor applications.
Describe a usage example. FIG. 5 shows layer 1 according to the invention.
A window 120 coated with 18 is shown. FIGS. 6 and 7 are graphs showing conductivity and reflectivity that vary with the concentration of fluorine doping agent. 10, 15... Bubbler, 20, 21, 22...
... Tank, 25 ... Regulator, 30 ... Metering valve, 40 ... Flow meter, 50 ... Check valve, 60 ... Mixing pipe, 70 ... Chamber, 80 ... Surface, 90 ... Heater, 102 ... n- _SnO2 ,
104...n-silicon, 106...p-silicon, 108...Al, 110...metal grid.

Claims (1)

[Scope of Claims] 1. (a) A first organotin fluorine-containing compound in which tin and fluorine are not directly bonded, (b) an oxidizable tin compound, and (c) an oxidizing gas from the beginning. A method for preparing a transparent film of stannic oxide on a heated substrate using a gaseous mixture, comprising: (a) direct bonding of tin and fluorine to a first organotin fluorine-containing component of the gaseous mixture; (b) direct oxidation of the second fluoride in close proximity to the substrate to obtain a fluorine doping agent in the gaseous mixture; and (c) forming a fluorine-doped stannic oxide film by simultaneously depositing the oxidizable tin compound and the fluorine doping agent on the heated substrate. The above method characterized by: 2 The first organotin fluorine-containing gaseous compound is (a)
CF ₃ I, CF ₃ Br, and alkyl alpha fluorinated homologues of these CF ₃ I, CF ₃ Br, and
formed by heating a gas mixture containing a gas selected from the group consisting of CF ₃ SF ₅ , SF ₅ Br, and SF ₅ Cl, or a mixture thereof, and (b) an oxidizable tin compound; 2. The method of claim 1, wherein (a) and (b) are substantially inert to each other at temperatures below 65.6°C (150°C). 3. The first volatile organotin-fluorine-containing compound in which tin and fluorine are not directly bonded is converted into an organotin fluoride gaseous compound in which tin and fluorine are directly bonded by heating the substrate. A method according to claim 1 for changing. 4. The method according to claim 1, wherein the gaseous mixture is directed upward from below the substrate to be coated to form a coating on the bottom surface of the substrate. 5. Tetramethyltin vapor at concentrations up to 1% is the volatile oxidizable tin compound, oxygen gas at partial pressures up to 1 atm is the oxidizing gas, and the surface heated to 500°C is A method according to claim 1 for depositing tin. 6. The method according to claim 1, wherein the first fluorine-containing compound is a volatile tin compound that decomposes upon heating to produce organotin monofluoride vapor. 7. The method according to claim 6, wherein the volatile tin compound is trimethyltrifluoromethyltin. 8. The method of claim 6, wherein the volatile tin compound is trimethylpentafluoroethyltin. 9. Although the mixture of (a) and (b) is stable at 32.2°C (90°C), the reaction between (a) and (b) is thermally initiated to form the organotin monofluoride; 3. The method of claim 2, wherein the fluorine impurity is a raw material for controlled addition of fluorine impurities to a stannic oxide film. 10. The method of claim 9, wherein the fluorine doping agent is formed by reacting trifluoroiodomethane with an organotin compound containing at least one tin-carbon bond per molecule. 11. The method according to claim 10, wherein the fluorine doping agent is formed by reacting trifluoroiodomethane gas and tetramethyltin. 12. The method according to claim 10, wherein bromine is substituted in place of iodine. 13. The method according to claim 11, wherein bromine is substituted in place of iodine. 14. The method according to claim 9, wherein the fluorine doping agent is formed by reacting sulfur monochloride pentafluoride gas with an organotin compound containing at least one tin-carbon bond per molecule. . 15. The method according to claim 14, wherein the fluorine doping agent is formed by reacting sulfur monochloride pentafluoride gas with tetramethyltin. 16 Trifluoromethyl sulfur pentafluoride gas and 1
10. The method of claim 9, wherein the fluorine doping agent is reacted with an organotin compound containing at least one tin-carbon bond per molecule. 17. The method of claim 16, wherein sulfur trifluoromethyl pentafluoride gas and tetramethyltin are reacted to form a fluorine doping agent. 18 The free electron concentration of the film is 10 ²⁰ cm ^-3 ~ 10 ²¹
2. The method of claim 1, wherein the ratio of fluorine doping agent to oxidizable tin compound is selected to be within the range of cm ^-3 . 19. The method of claim 1, wherein the amount of fluorine doping agent in the stannic oxide film is 1% to 3% fluorine substituted for oxygen. 20 In a method for depositing a transparent tin oxide film doped with fluorine on a heated substrate, (a) tin and fluorine can be converted into an organotin fluoride in which tin and fluorine are directly bonded in close proximity to the heated substrate; (b) depositing said organotin fluoride compound together with the oxidizable tin component of said chemical gas on the surface of said substrate; forming a fluorine-doped tin oxide coating on the surface. 21 A method for depositing a film of fluorine-doped stannic oxide on a heated substrate, comprising: (a) a gaseous fluorine-containing component; and (b) a gaseous oxidizable tin-containing component; (c) a gaseous oxygen-containing component, and optionally (d) an inert carrier gas, selecting those components such that they remain in the gas phase at the temperature at which they are mixed; Only when the gas mixture is heated to about the temperature of the heated substrate mentioned above will components (a) and (b) react to form a compound having a tin-fluorine bond, and then a tin-fluorine bond. The above compound having an elementary bond is reacted with the above oxygen-containing component to precipitate a film made of fluorine-doped stannic oxide on the above heated substrate, in which case component (a) The above method wherein contains a reactive fluoroalkyl group. 22 Claim 2 in which component (a) contains a fluoroalkyl halide or a mixture thereof
The method described in Section 1. 23. The method according to claim 22, wherein component (a) contains a gas selected from the group consisting of CF ₃ Br, CF ₃ I and their homologs or substituted fluorinated compounds, or a mixture thereof. Method. 24. The method of claim 21, wherein component (b) contains tetramethyltin. 25. The method of claim 21, wherein component (b) contains dimethyltin dichloride. 26. The method of claim 21, wherein component (a) comprises a reactive fluorosulfur group.