Method for preparing vaporized reactants for chemical vapor deposition

The present invention relates to the process for preparing reagent vapors and, more particularly, to the process for preparing reagent vapors mixtures, for example a coating precursor and a chemical vapor deposition gas mixture.

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General Framework of the Invention

Coated glassware is typically made by continuously coating a glass substrate while it is being made by a process known in the art as Float Glass Process. This process involves pouring the glass into! a molten tin bath which is suitably closed, then transferring the glass, after sufficient cooling, to lifting and unloading rollers which are aligned with the bath, and finally cooling the glass as it advances through the rollers. initially through a guiding device and subsequently exposing it to the ambient atmosphere. In the float section a non-oxidizing atmosphere is maintained while the glass is in contact with the molten tin bath to prevent oxidation from occurring.

An air atmosphere is maintained in the guiding device.

Chemical vapor deposition of various coatings may conveniently be carried out in the bath or the guide chamber or even in the transition zone therebetween.

The physical form of the reagents used in the glass coating process is generally a gas, a liquid or a vaporized solid or liquid, or a liquid or solid dispersed in a gaseous carrier mixture or a vaporized liquid or solid dispersed in a gaseous carrier stream. The chemical vapor deposition process generally employs a vaporized liquid or solid, which is typically dispersed in a carrier gas mixture.

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Chemical vapor deposition processes are well known in the art of glass substrate coating. U.S. Patent 4,100,330 describes a process for coating a glass substrate with a first silicon layer and a second layer of a metal oxide deposited by vapor pyrolysis decomposition of a surface coating metal compound. hot substrate under an oxidizing atmosphere.

U.S. Patent No. 4,747,557 relates to a process for coating glass substrates with a first silicon-containing layer, overlaying a layer comprising titanium nitride, a second layer which contains silicon coating the titanium nitride-containing layer, and optionally, on the second layer comprising silicon, an abrasion resistant layer, for example comprising tin oxide.

U.S. Patent 4,692,180 discloses a process for spraying a powdery metal compound directly onto the surface of a float glass film, in which the powder decomposes by pyrolysis. to prepare the metal oxide coating. U.S. Patent No. 3,852,098 discloses the vaporization of dispersed powdery metal compounds by a hot gaseous carrier which is then directed to the surface of the hot glass substrate to deposit an oxide coating. metallic. A Patent disclosing a similar process using solid metal compounds is U.S. Patent No. 2,780,553, in which a fixed bed of one of a metal coating compound is vaporized upon contact with a hot gaseous carrier.

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Finally, U.S. Patent No. 4,351,861 discloses a process for fluidizing a particulate reagent into a gaseous carrier, which is then heated to vaporize the suspended particles, and is directed onto the surface of the hot glass substrate for formation. of the coating. These processes using solid precursor coating particles produce reactant streams that are subject to concentration variations due to fluctuations in particle size, changes in particle surface area over time, difficulties in transporting solid materials to a stable rate, etc.

The prior art also includes processes in which organometallic salts are solubilized in an acid or hydrocarbon, and are subsequently vaporized in a hot gaseous carrier.

U.S. Patent No. 4,571,350 discloses a process for spraying an atomized mixture of a metal salt solution into a vaporization chamber. The solution is vaporized and subsequently directed onto the surface of a hot glass substrate. U.S. Patent No. 3,970,037 relates to the dissolution of a coating reagent in a solvent, which is then sprayed onto a hot gaseous carrier where it is sprayed, and is then directed onto a surface of a hot glass substrate. In both cases, the reagents decompose by pyrolysis to produce an oxide coating, but solubilizing agents interfere with molecular transport on the glass surface. consequently causing variations in deposition.

Another process for the production of thermally decomposing metallic vapor streams for chemical vapor deposition processes is to bubble a hot gaseous carrier into a liquid metal salt as it is. disclosed in U.S. Patent Nos. 4,212,683 and 4,261,722. U.S. Patent 3,808,035 discloses the passage of an inert gas which is introduced through a gas bubbler producing a gas stream having a low precursor concentration, and subsequently directing the gas stream into contact with the gas. substrate at a temperature in the range 100 ° C to 300 ° C. Although the blistering process provides a process for spraying liquid coating precursors directly onto a gaseous carrier, this process has several disadvantages that diminish their utility in preparing reagent vapors for chemical vapor deposition. First, the coating liquid precursor bath should be kept at a temperature close to its boiling temperature in order to ensure a high concentration of the vaporized reagent in the gaseous carrier. This high bath temperature, maintained over a long period of time, can accelerate the decomposition of coating precursors, some of which are very heat sensitive. In addition, the specific vaporization heat required to vaporize the liquid causes the bath temperature to decrease as the gaseous carrier substance bubbles through the compound. Lowering the bath temperature, which is difficult to remedy evenly using external heating sources, causes the vapor pressure of the liquid to decrease, thereby causing a constant decrease in the vaporized precursor concentration in the gaseous carrier stream. Finally, in a bubble formation process wherein the liquid bath contains two or more coating precursors, each having a different

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vapor pressure of the pure component, thus preferably vaporizes the most volatile component, thereby changing the partial vapor pressure of the liquid components and consequently changing the concentrations of the vaporized reactants in the gaseous carrier stream while bathing. liquid runs out.

It should be noted that the prior art referred to herein has been assembled and examined in light of the present invention for guidance only. It should be understood that such techniques would otherwise be brought together without the motivation promoted by the present invention.

It would be desirable to be able to vaporize the coating precursors or mixtures thereof in order to produce a stable and uniform stream of a concentrated coating precursor vapor which would allow the formation of thicker deposited layers. than those obtained by prior art processes while providing superior control for coating deposition.

IMVEMTION DESCRIPTION

The present invention relates to a process for the preparation of reagent vapors, useful for example for the deposition of chemical vapors on hot substrates. According to the present invention, it has been surprisingly found that reagent vapors can be produced from coating precursors by performing a

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novel process which allows vaporization of higher and more consistent concentrations of reactants in a gas stream, such process comprising a coating precursor at a temperature above its melting point but substantially below its standard vaporization temperature (under normal conditions) , the liquid precursor is consequently found, and this process is characterized by the fact that:

A) The following phases are to be carried out simultaneously and continuously:

i - injecting the liquid coating precursor into a vaporization chamber, defined in part by at least one peripheral wall, in which the liquid coating precursor produces a vapor;

ii - feeding the vaporization chamber with a gaseous mixture in an amount sufficient to increase the mass transport of the coating precursor vapor and thereby cause accelerated vaporization of the liquid coating precursor;

iii - mixing the coating precursor liquid with the coating precursor vapor and the gas mixture, including distributing the liquid precursor as a thin film along the wall of said chamber:

such that the liquid coating precursor is completely vaporized at a temperature which is below its vaporization temperature under normal conditions in order to prepare a vaporized precursor reagent gas stream having a high uniform concentration of the coating precursor; and

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B) transporting the coating precursor and reactant gas mixture out of the vaporization chamber.

A horizontal thin-film evaporator provides a vaporization chamber suitable for the process of the present invention. Preferably, the liquid coating precursor is injected through the upper inlet port, and the gas mixture is admitted into the lower inlet port of the horizontal thin-film evaporator. The gas mixture is preferably preheated to a temperature approximately equal to the temperature at which the vaporization chamber is heated. The vaporization chamber is preferably heated to a temperature above that of the liquid precursor injected into it but below the vaporization temperature under normal conditions of the coating precursor.

The process of the present invention is conveniently carried out continuously, and is suitable for vaporizing coating reagent precursors for use in chemical vapor deposition. It is particularly suitable for the deposition of vapors of coating chemicals on glass produced by the floating glass process. With regard to the latter, the process includes providing a coating precursor at a temperature higher than its melting point, but substantially lower than its vaporization temperature under normal conditions, and therefore the precursor occurs. coating is in liquid form and is characterized by the fact that:

A) if the following operations are performed simultaneously and continuously:

i) injecting the liquid coating precursor into a vaporization chamber in which that precursor produces a vapor;

ii) feeding the vaporization chamber with a gaseous mixture in an amount sufficient to increase the mass transport of the coating precursor vapor and thereby cause accelerated vaporization of the liquid coating precursor; and iii) mixing the liquid coating precursor with the coating precursor vapor and the gas mixture;

such that the liquid coating precursor is completely vaporized at a temperature below its vaporization temperature under normal conditions in order to prepare a vaporized reagent gas stream having a high uniform concentration of the coating precursor; and

(B) remove the vapor mixture from the coating precursor.

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te reagent gas from the vaporization chamber; and

C) contacting said reactant gas stream with a float glass substrate maintained at a temperature of at least 399 ° C (750 ° F).

BRIEF DESCRIPTION OF DRAWINGS

In the attached drawings:

Fig. 1 is a partially schematic illustration of a device for practicing the process of the invention including a vertical cross section of the vaporization chamber, in this case a horizontal evaporator;

Fig. 2 is a vaporization vertical cross-sectional view of the chamber viewed along line 2-2 of Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more particularly to the drawings, the apparatus for carrying out the invention comprises a preheating vessel 10, equipment generally illustrated at 11 for introducing the gas mixture into the system, and a vaporization chamber, generally designated by numeral reference 12. ' The vaporization chamber 12 comprises a liquid zone 13 and a vapor zone 14.

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The boundary between the two zones is generally indicated by line 15 in Fig. 1. The liquid zone 13 is defined as the area within the vaporization chamber 12 in which the wall IS of said chamber 12 is coated with the liquid coating precursor. whereas the vapor zone 14 is defined as the area of ​​the vaporization chamber 12 in which the coating precursor has been completely converted to steam. The location of the boundary (indicated by line 15) between the liquid zone 13 and the vapor zone 14 will vary depending on the volatility of the specific coating precursor used, the mass flow rate of the gas chamber, etc. Thus, when using a relatively high volatility coating precursor, the vaporization chamber will have a relatively larger vapor zone 14.

The liquid coating precursor is injected into the liquid zone 13 of the vaporization chamber 12 through the upper inlet opening 17, so-called because it is situated adjacent to the top of the vaporization chamber 12. A gas mixture is injected into the liquid zone 13 of the vaporization chamber 12 through the lower inlet opening 18, so named because it is situated adjacent the bottom of the vaporization chamber 12. The gas mixture, which may for example comprise helium or nitrogen or mixtures thereof, is stored in gas bottles 19 and 20e and is channeled through regulators 21, flow meters 22, and valves 23 to the inlet port. 18. Close contact occurs between the falling liquid and rising gas mixture due to the gas mixture being injected from below and the coating precursor being injected from above.

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As shown in Figures 1 and 2, a set of mixing blades 24 rotates within the vaporization chamber 12 and distributes the liquid precursor as a firm and uniform film around the vaporization chamber wall (s), and promotes further mixing of the coating precursor with the gas mixture. Once converted to steam, the coating precursor is discharged, together with the gas mixture, from the steam zone 14 through the outlet opening 25. 0 The vapor may then be further treated, for example, combined with other reactant or doping vapors, and / or transported to a suitable CVD deposition area.

Coatings may be deposited on the surface of a hot glass substrate by a process commonly known in practice as chemical agent vapor deposition (CVD). This process is typically conducted during glass production by the floating glass process, and may occur in the floating metal bath where the glass film is at a temperature in the range of about 593 ° C (1100 ° F) to about 732 ° C (1350 ° F) in the oven (glass temperatures between about 400 ° C (750 ° F) and about 565 ° C (1050 ° F), or in the transition zone between bath and oven (glass temperatures from 552 ° C (1025 ° F) to about 593 ° C (1001 ° F) .The coating precursors are vaporized and transported to the surface, or close to the surface of the moving glass film In the presence of oxygen, the coating precursors decompose by pyrolysis to give an oxide coating on the glass surface. However, the invention is not limited to the deposition of oxide coatings, but may also be used when depositing non-oxide coatings such as silicon or titanium nitrides. In addition, the invention may be used for vapor deposition of

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chemicals on any substrate, and deposition on glass is not limited.

Suitable coating precursor agents useful in the practice of the present invention include the following, but are not limited to: dimethyl tin dichloride, tetraethoxysilane, diethyl tin dichloride, dibutyltin diacetate, tetramefeilin, lasfyl tin dichloride, triethyl tin chloride, trimethyl tin chloride, tetrabutyl titanate, tethalumdron titanium dichloromethane, tetrachloride aluminum acetylacetonate, aluminum ethylate, diethyldichlorosilane, methyl triethoxysilane, zinc acetylacetonate, zinc propionate, It's your mixtures.

These compounds are generally well known in CVD technology as precursors for the application of coatings on hot glass. The invention will work equally well for any precursor material or mixtures thereof which exert a vapor pressure. A preferred coating precursor for tin oxide deposition is dimethyl tin dichloride, or a mixture of dimethyl tin dichloride and methyl tin trichloride, for example 95 wt% dimethyl tin dichloride and 5 wt% methyl tin trichloride.

The coating precursors of the present invention may be either liquid, which exert a vapor pressure at room temperature, or solids which, when heated above room temperature but below their vaporization temperature under normal conditions, become liquid. exerting a vapor pressure at such elevated temperatures., - By the term vaporization temperature under normal conditions¹As used herein, it is understood that which is the vapor of the pure so-called liquid is equal to a vine, In which case, the inventive compounds of the invention are initially heated to a pre-heated temperature. -ú otinqirsm Sssipsra sweating cures to the sausage points fusion Φ33 auboíanoialmanfo inaeriorrs * 10 -your semϊ3-? tures have vaporization under normal conditions, At these coopipurations, 03 Raids of the RBaBiNgRaBaLiNgRiBiNiSii that 30 find their temparstures not inferior to the Turkish tempera of decay, By the aforesaid rprnej3 The jemoeroiura of vaporization in these conditions

?. ·; ç Is ”, anmo here used, it is taught a capparatura that 20 f 3 onico ó^tJG a about ds 3u * C below the temperature ds vapaνίζαραα (3) 3 3 standard conditions of a compound (the pro? Sor of? .37? 3SÍ23n; 3), such that the thermal decomposition gives oo.apoo; ? 3 grondomonte rsduríde.

λ .pdiçsc of the gaseous mixture to the aorax of the steam vapor to Saaraforurrjia d-3 vsoar aaara rsvsscisanas vapors vapor stage, Eo'õ3 steam transcrence increase: λ ·.; 23 and the coating coating originates aciasηοία of the vaporization of the liquid precursor of rovosoiaonco.

concocfo jtiãré the liquid precursor tí rrvi-seriasn tíjosa tyura occurs desirably as far as the vaporization chamber is concerned.¹As defined herein means a cracked vessel comprising a zone of the liquid or a zone of vapor in which, as the incoming liquid is driven against the internal stops of the reaction to form. above them a uniform thin capsule 3, ν or.&gt; 3sqaanfαιαηΐο vaoorizc-ss, The force that drives the irai liquid and persists can be counteracted by the rooores alone, by the flow of liquid under pressure, or by tidal forces produced by rotary blades

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rizatíor or by the rotation of the vaporizer itself (with or with blades), etc. The container walls may optionally be heated to increase the vaporization rate of the liquid as it comes into contact with the vaporization chamber walls. Complicated gas mixtures include for example helium, nitrogen, hydrogen, or any other carrier gas that is chemically inert to the rsv precursor at the temperatures used, as well as their mixtures. Preferred gas mixtures are helium to nitrogen and mixtures thereof.

The coating precursor may initially be heated by any conventional device known in the art for heating solids or liquids, such as flame heating or electric heating resistors of the preheating chamber 10 containing the coating precursor. 0 The coating precursor is typically heated to a temperature above its melting point, but substantially below its vaporization temperature under normal conditions, and is subsequently injected into the vaporization chamber in liquid form.

Within the vaporization chamber 12, the liquid precursor will be vaporized. The rotary mixing blades 24 are used to mix the contents of the vaporization chamber 12. The liquid coating precursor is continuously distributed as a uniform thin film over the walls of the vaporization chamber 12 due to the centrifugal forces generated by the mixing powders 24. Turbulence is imparted to the film as it flows towards the outlet opening 25, inducing a slight heat transfer rod to the liquid film coincident with vapor formation. In addition, the precursor

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the liquid vapor, the vapor of the precursor ds rssvimscbo 3 -jaaaura qauosa are large inside the chamber the vapor is “a more than a degree higher than the Groughness of the precursor” □; : t-3 £? 2su? vs vs, under normal conditions, o preaur-0 / vavssiimonao. The work to which the οο 'ιροnontes?&gt; Are &lt;j'n rltibι 3073 daásrMined by the oscillic decoosition of the p-srouroor is specifically used for the mixture of the chosen gas mixture mass. 3 i-^!The liquid of the liquidation on the chemical accumulation of the "liquid" -433333, or as its rosy proportions of the vaporizing chamber 12, gave the liquid: the liquidation. i30-130 escoinidas, of the form qy-s ssPaja praganca a quan ».Ldcjs yjiiulsnia of the aiooora yaoosa to the oamas oco aumsnco n ·&gt; j longing V. our auntie was the forerunner of voporiza-jij revsuimeftúo, adjusting the vaporization of the liquid »daoaa.larma, the liquid precursor of her simento oompleia-vjporízatio to aao ohyhiparaurá less than its normal conditions; .

Dy / i-Jo to the pr3Ρ &amp; 0 of the liquid precursor tie rsvaaciaenàr ssr rare to vorified iris sm relative quancitistís psqusnao, already.ss-3 of the liquid anoonára 2-smpsrs high cures only oor am? Y? Ij period of the bampo and the = orocossaa 'Already the conventional convention requires the bath to be washed'; 3 ', as maintained by a rapid cure of the vaporization, giving rise to the decomposition of the liquid flow of water. dma vaz wed, following the? -33 In the invention, the liquid dent is manoid 3 ^-In addition to the desoric processes in the early or early years, the liquid spray is not minimized.

liquid coating precursor, the vapor of the gas mixture coating precursor is conveniently heated by heating the vaporization chamber 12 using conventional means such as, for example, electric resistance or flame heating, or by steam jacket. In this way, the temperature of the vaporization chamber 12 is kept constant, and the heat required for vaporization of the liquid is provided. 0 The coating precursor may be preheated within the preheating vessel 10 at a temperature above its melting point, but substantially below its vaporization temperature. The gaseous mixture is preferably preheated to approximately the temperature of the vaporization chamber prior to its introduction into the vaporization chamber.

Means are provided within the vaporization chamber 12 to ensure complete mixing of the precursor with the gas mixture, so that ultimately a uniform reagent mixture is directed to the substrate.

The present invention discloses an improved process for spraying the coating compounds, obtaining a high and uniform concentration of the spray coating precursor and the gas mixture. This is advantageous for accurately counteracting the applied coating thickness, reducing the amount of decomposition of the coating precursor prior to coating and producing thicker coatings than those obtained by conventional spraying processes.

A horizontal thin-film evaporator, such as commercially available from Artisan Industries, Inc. Waltham, Hassachusetts, USA, the product being designated One-Half Square Foot Hototherm E®. provides a vaporization chamber 12 suitable for the present process.

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Preferably, the liquid coating precursor is injected into the vaporization chamber 12 through the inlet port 17, and the gas mixture is injected into the vaporization chamber 12 through the lower inlet port 18, which is located at the same end of the chamber. that the upper inlet opening 17.

Additionally, rotation of a set of blades 24 within the vaporization chamber 12 (in this case a horizontal thin-film evaporator) promotes perfect mixing of the coating precursor and the gas mixture. A motor 28 provides the power to rotate the blades 24. The vapor mixture is conveniently discharged from the outlet opening 25, which is located at the opposite end to the upper and lower inlet openings 17 and 18.

The process of the present invention is conducted continuously, so that a stream of the gas mixture having a high and uniform concentration of vapor of the coating precursor is continuously produced. The stream is required to flow from the vaporization chamber 12 through a conduit to the surface of the hot substrate by means of the pressure generated by vaporization of the injured liquid through the upper inlet opening 17 and the introduction of the pressurized gas mixture through it. from the lower inlet opening 18 to the vaporization chamber 12.

When using the coating precursors and gas mixtures mentioned herein according to the invention, the gas mixture is generally admitted through the lower inlet opening 18 into the vaporization chamber 12 at a pressure of about 0.14 to about 1.05 fcg / cm, and a throughput of from about 100 to about 400

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minute. The liquid precursor of the coating is first preheated to a temperature in the range of about 21 ° C to about 28 ° C, then injected into the vaporization chamber through the upper inlet port 17, and the contents of the vaporization chamber. Vaporization 12 is maintained at a temperature of from about 35 ° C to about 290 ° C. 0 The liquid coating precursor is desirably vaporized at a rate of between 0.227 to about 34.4 kg per hour. The mass flow rates referred to herein for the gas mixture and the liquid coating precursor are values ​​suggested when using for example a horizontal evaporator of 0.043 ra thin film² (1/2 ft²) of surface area, such as vaporization chamber 12. However, it should be understood that practically any flow rate of the gas mixture and liquid precursor for a given suitable vaporization chamber and the specific reaction conditions may be used. For example, larger models of Rocotherra E will vaporize larger amounts of the liquid coating precursor. The flow rates will be determined by the desired thickness and growth rate for the coating.

For example, a reagent vapor mixture suitable for chemical agent vapor deposition on a tin oxide coating may be generated using precursor diraethyl tin dichloride. The nitrogen gas mixture is generally admitted through the inlet port. lower 18 into the vaporization chamber 12 at a pressure in the range of about 0.14 to 1.03 kg / cm² a flow rate in the range of from about 100 to about 400 normal liters per minute. 0 diraethyl tin dichloride is preferably pre-cooled at a temperature in the range of from about 107 ° C to about 90 ° C, and is then injected, for example by pressure caused by liquid flow, or by pump into the chamber. and the contents of the vaporization chamber 12 are maintained at a temperature in the range of from about 121 ° C to about 204 ° C. 0 Dimethyl tin dichloride as a liquid coating precursor is desirably vaporized at a rate of about 0.45 to about 23.5 µg per hour, or from 0.77 to 49 liters per minute. Dimethyl tin dichloride flow rates such as this, together with a gas mixture flow rate of 400 liters per minute, will provide a reactant vapor stream at outlet 25 in the range 0.19% to 12.3%. of the gas phase (volume / volume) of dimethyl tin dichloride. If gas flow rates are higher or lower, the% gas phase will decrease or increase respectively. The above-mentioned mass flow rates for the gas mixture and the liquid coating precursor are suggested values ​​when using, for example, a 0.045 ra thin-film horizontal evaporator.² (1/2 ft²surface area as vaporization chamber 12. Tin oxide coatings may be deposited on the glass at growth rates up to about 2 200 Angstroms per second using dimethyl tin dichloride mixtures within the range of rates just mentioned. .

Most coating precursors, when vaporized, are extremely flammable under oxidizing conditions, and therefore can only be sent to the reaction zone in a carrier gas stream at a small percentage concentration of the gas phase. Higher concentrations of the coating precursor vapor will ignite when in contact with the hot substrate surface in an oxidizing atmosphere. Accordingly, the coating operation should be conducted using a vaporized coating precursor stream having a concentration below the flammability limit for the coating precursor concerned.

Due to the inherent variability of the prior art vaporization process, for example, said or dispersed powder flow vaporization, vaporization of particles in a compact bed, vaporization of solubilized compounds, or bubbling of a carrier gas through From a liquid metal salt, the concentration of the vapor of the coating precursor in the carrier gas produced by such processes usually varies or changes over time. Accordingly, the average usable concentration of the coating precursor vapor must be substantially below the flammability limit, so that increases in concentration do not cause the coating precursor vapor to ignite.

The process of the present invention, by contrast, promotes a stable vapor stream of the uniformly concentrated coating precursor. Due to the fact that there are less deviations from the vapor stream concentration, the vapor may be transported at temperatures closer to the flammability limit. Accordingly, more coating precursor can be vaporized and transported to the reaction zone, thereby promoting thicker coatings and higher growth rates than can be obtained by the prior art spraying processes.

It should be noted that process conditions are not strongly critical for successful preparation of the reagent vapors according to the present invention. The conditions of

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The processing methods described herein are generally exposed under conditions that are conventional to the practice of this invention. Occasionally, however, the processing conditions as described may not be precisely applicable for each compound within the scope of the invention. Such compounds for which this occurs will be readily recognized by those skilled in the art. In such cases, the process may be successfully carried out by conventional modifications known to those skilled in the art, for example by raising or lowering the temperature, varying the rates of introduction of the coating precursor or gas mixture, or switching to alternative CVD reagents or mixtures. alternative gases, routine modifications of vaporization process conditions, etc.

The invention is more readily understood by reference to a specific embodiment which is representative of the invention. It is to be understood, however, that a specific embodiment of the invention is disclosed solely for the purpose of illustration, and that the invention may be practiced differently from that illustrated in the example without departing from the spirit or scope of the invention. For example, a device other than the horizontal thin film evaporator but which promotes close contact, rapid heating, and complete mixing of the metal coating compound and gas mixture may be used as a vaporization chamber.

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Dimethyl tin dichloride is heated at about 388 ° C s

24 injected in liquid form at a rate of about 29 Xg per hour into the inlet opening 17 of the vaporization chamber 12, in which case a 0.040 m horizontal thin-film evaporator was used.² that area has that surface. At the same time 250 liters per minute of nitrogen under normal conditions (yes) shall be allowed at a pressure of about 0,5 kg / cm² through the lower inlet opening 18 of the vaporization chamber 12, and the contents of the vaporization chamber 12 is heated to maintain a temperature of about 160 ° C. The reactive stream, comprising about 50 µm vaporized dimethyl tin dichloride and about 250 µm nitrogen (± 6.5% gaseous dimethyl dichloride), is removed from the vaporization chamber 12 through outlet 25. at the end of the vaporization chamber 12, opposite the end comprising inlet openings 17 and 18. The rsag stream is then heated, combined with about 50 µg oxygen and about 23 µl water vapor, the mixture comprising at this time 13 µl of dimethyl tin dichloride in the gas phase. The combined stream of reagents is directed onto the surface of the hot glass substrate as it is produced by the floating glass process and at a temperature of about S27 ° C, resulting in a uniform tin oxide coating deposited at a rate of 2 200 Angstroms per second.

before

The above-mentioned parameters for dimethyl tin dichloride work equally well for a precursor mixture comprising 95 wt% dimethyl tin dichloride and 5% methyl tin trichloride.