US 3808035 A
A very thin layer is deposited from a dilute gas sweep onto suitable substrates including glass, metal, plastic, etc., in an atmospheric pressure process. Moderate temperatures, i.e., between 100 DEG C and 300 DEG C, can be used, although higher temperatures are sometimes useful. For example, in a preferred embodiment for manufacturing a multiple layer optical component, e.g., a dichroic filter, relatively small amounts of gaseous deposition precursors or reactants are thoroughly admixed in a large volume of high velocity gas stream to provide a relatively dilute, gas-vapor deposition stream. To produce alternating layers, two different dilute high velocity gas streams are alternately introduced into a relatively large atmospheric pressure coating chamber containing a plurality of substrates, which substrates are preheated to a deposition temperature of about 200 DEG C.
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Description (OCR text may contain errors)
United States Patent 1191 Stelter Apr. 30, 1974 DEPOSITION OF SINGLE OR MULTIPLE LAYERS ON SUBSTRATES FROM DILUTE GAS SWEEP TO PRODUCE OPTICAL Primary Examiner-Ralph S. Kendall Assistant Examiner-Michael Esposito Attorney, Agent, or Firm-Greist, Lockwood, Green- COMPONENTS, ELECTRO-OPTICAL Walt & Dewey COMPONENTS, AND THE LIKE Inventor: Manfred K. Stelter, 605 Waukegan  ABSTRACT Rd., Glenview, [11. 60025 Filed: Dec. 9, 1970 Appl. No.: 96,428
A very thin layer is deposited from a dilute gas sweep onto suitable substrates including glass, metal, plastic, etc., in an atmospheric pressure process. Moderate temperatures, i.e., between 100C and 300C, can be used, although higher temperatures are sometimes US. Cl. 117/106 R, 117/106 A, 117/333 useful. For example, in a preferred embodiment for Int. Cl. C23c 11/00, B29d 1l/00 manufacturing a multiple layer optical component, Field of Search... 1 17/ 106, 33.3, 106 R, 106 A e.g., a dichroic filter, relatively small amounts of gaseous deposition precursors or reactants are thoroughly  References Cited admixed in a large volume of high velocity gas stream UNITED STATES PATENTS to provide a relatively dilute, gas-vapor deposition 2,831,780 4/1958 Deyrup 117/106 x i To poduce alternating layers different 3,306,768 2/1967 Peterson 7/106 R d1lute high velocity gas streams are alternately intro- 3161 11813 12/1961 Lely et al.... 117/106 R duced into a relatively large atmospheric Pressure 3,031,200 3 19 3 T0mpkin 117 10 x coating chamber containing a plurality of substrates, 3,142,586 7/1964 Colman 117/106 R which substrates are preheated to a deposition tem- 2,847,330 8/1958 Toulmin 7/1072 R perature of about 200C, 3,032,397 5/1962 Niederhauser 117/106 X 19 Claims, 4 Drawing Figures .PATENTEBAPHOM 3.808035 sum 1 or z 2 so 0 6 60 2 (D 1 0: 40
WAVELENGTH. 1N MICRONS INVENTOR MANFRED .K. STELTER ATT TPATENTEDAPR 30 I974 SHEET 2 (1F 2 MANFRED K. STELTER 0HHHHHHHHHHHHH INVEN TOR DEPOSITION OF SINGLE OR MULTIPLE LAYERS ON SUBSTRATES FROM DILUTE GAS SWEEP TO PRODUCE OPTICAL COMPONENTS, ELECTRO-OPTICAL COMPONENTS, AND THE LIKE This invention relates to a method and apparatus for producing optically or electro-optically active layers, and the like, e.g., dichroic filters of the type comprising an optical substrate having multiple micro-thin layers of optical filter material thereon.
These layered products are presently well known in the art and the industrial, commercial and scientific value of these products is well established.
One of the shortcomings of some of the specific methods heretofore available for the manufacture of these layered products is the extremely high vacuum environment which is required in these specific methods. Other previously suggested practice requires the use of expensive or sophisticated electronic equipment such as that associated with electron beam evaporation, glow discharge cleaning or RF-sputtering to manufacture corresponding optical filters.
Another shortcoming of some of the methods heretofore available for the manufacture of such layered products is the extremely high temperatures required in these methods, i.e., temperatures at or above the softening point of a glass substrate, for example. While such methods may be useful for coating glass sheets, etc., they are not suitable for use to coat pre-shaped substrates, e.g., lenses, glass flats and the like, due to the greater likelihood of distortion and shape-change, which becomes more likely to occur at softening temperatures, and at higher temperature. This distortion effect is also detrimental if parts have to be coated which contain highly accurate graduations or indicia for precision measurements. Here already temperatures above 250 C can cause irreparable damage. Moreover, methods requiring very high temperatures, e.g., above 500C do not lendthemselves for use with most pla'stic substrates.
Similar layer forming techniques have been suggested for use to deposit electro optical components, e.g., layers for photocells, or photo readout gratings. High vacuum thin film deposition, and extremely high temperature epitaxial techniques were suggested. Also, in conjunction with such methods, mechanical masks or photo-resist stencils were used for pattern generation for selective deposition.
Some heretofore suggested methods involved vapor deposition from atmosphere rich in the deposited material, or rich in a precursor, or reactant which results in or yields a material constituting the resulting layer. These methods are considered to be deficient because of the difficulty in depositing a large number of high quality substantially equal coatings simultaneously. The deficiency is believed to be the result of localized differences in availability of reactants and, at least in part, because of chemical interference at the substrate which is occasioned by what I now believe to be excessive quantity of reactants.
Another shortcoming of many heretofore available methods of manufacturing such optical filters and electro-optical layers relates to layer quality, and is believed to result from the so-called line of sight nature of deposition transfer achieved in many high vacuum methods. This results in difficulty in achieving a uniform layer reqardless of the shape of the substrate, e.g., on a concave or convex face as well as on an irregularly shaped substrate, being impinged by the layer-forming material during high vacuum methods, e.g., in electron bombardment-vapor deposition. For example, one difficulty associated with such coating methods is the tendency for the coating to be incomplete due to the presence of voids. These voids are believed to be caused by the shadow of minute surface irregularities. Since irregularities shade the regions immediately behind themselves from coating material traveling in a straight line from the source, minute projecting irregularities are found to build up and the shadows behind them are found to be deficient in, if not devoid of, layer material.
Another deficiency to the high vacuum, line-of-sight methods of deposition is the difficulty in uniformly coating irregularly shaped articles, and the difficulty in simultaneously uniformly coating a large number of substrates.
It is an object of this invention to provide a method and an apparatus for manufacture of single or multiple layer optical components and electro-optical components, and the like, which method does not require high vacuum conditions. It is a further object of this invention to provide a method of manufacture of optical filters such as dichroic filters, which method does not require the use of extremely high temperatures or the use of very sophisticated electrical or electronic equipment such as that involved in electron beam deposition and bombardment.
It is an additional object to provide a method of manufacturing single or multiple layer products which lends itself to multiple unit processing wherein a large number of filters or other components are simultaneously produced with great uniformity.
It is an additional object to provide a method for depositing micro-miniature patterned layers and other miniature pattern layers. It is another object to provide a method for depositing layers which permits great control over the extent and makeup of a transition layer.
It is a further object to provide a simple and reliable method for producing high quality uniform continuous optical filter layers regardless of shape of the substrate, and regardless of the presence of minute projecting irregularities on the substrate.
These and other objects which will be apparent hereinafter are all achieved in accordance with this invention as set forth in the following disclosure, wherein:
FIG. 1 illustrates a dichroic filter coated optical lens shown in side elevational view;
FIG. 2 is a greatly enlarged elevational cross sectional view taken approximately along the line 22 of FIG. 1;
FIG. 3 is a graph showing percent transmission versus wavelength, which graph illustrates the optical property of the dichroic filter shown in FIGS. 1 and 2; and
FIG. 4 is a schematicdiagram of a preferred apparatus for use in accordance with the invention.
In the figures the numeral 10 refers to an optical lens having multiple layers generally 12 of dichroic filter deposited on the convex surface 14 thereof. The layers 12 were deposited in accordance with the method of this invention, and specifically, in accordance with the preferred embodiment described hereinafter in the example. The filter segment illustrated in FIG. 2 includes a glass substrate 16 which is provided with a first coating 18 of iron oxide, a second layer 20 comprising chromium oxide, a third layer 22 comprising iron oxide, a fourth layer 24 comprising chromium oxide and an outer layer 26 comprising iron oxide. In the illustrated segment a rather sharp interface 28 is shown between glass substrate 16 and layer 18. However, transition zone 30 occurs between layer 18 and 20, and transition zones 32, 34, 36 occur respectively between layers 20, and 22, 22 and 24, and 24 and 26. These transition zones represent relatively narrow transition in which the zone has decreasing concentration of the inner layer material and increasing concentration of the nextouter material at points increasing in distance from the substrate.
The coated lens of FIG. 1 and FIG. 2 has optical properties illustrated in the graph of FIG. 3. It is noted that the percent transmission of light having wavelengths greater than 0.7 is virtually constant at about 8 percent. However, percent transmission of light at wavelengths less than 0.4 is substantially zero.
The method and apparatus of this invention is extremely simple and reliable and, in the following discussion, the apparatus will first be described briefly and the method will be described by means of the illustra tive example and subsequent general discussion.
A preferred embodiment of the apparatus of this invention which is schematically illustrated in FIG. 4 includes a number of gas-tight hermetically joined elements. Vaporizers 40, 42, in this embodiment, have an internal volume of about one pint. Vaporizers 40, 42 are heated by heating means 44, 46 respectively, which are diagrammatically illustrated by resistance coils. Any convenient, compatible method of, and apparatus for, heating vaporizers 40, 42 can be used. It is most desirable that heating means 44, 46 include means for automatically temperature-regulating vaporizers 40, 42. Either or both vaporizers 40, 42 can be supplied with a stream of helium or other inert gas through manifold 50 and conduits 52, 54, respectively. Elements 53, 55, respectively, indicate supply and metering system by which respective volatile (or gaseous) reactant meterial is charged to vaporizer mixers 40, and 42, respectively. For extremely precise control of vaporizer output rate, it is preferred to operate vaporizers practically dry, with sweep passing through, with the volatile liquid, being continuously added by means of a conventional constant advance piston, preferably one driven by a geared-down variable speed electric motor in a conventional manner. Elements 56, 58 schematically represent gas flow measuring and control devices.
Although, in the diagram, vaporizer flow is shown passing through submerged porous plates 59, 59', any conventional means for intimately contacting vaporizer sweep gas with vaporizing material can be used, e.g., a submerged inlet, fritted plate, etc.
Conduits 60, 62 carry effluent gas mixture from vaporizers 40, 42 respectively, to a second manifold 64. Valves 66, 68 provide on-off flow control from respective vaporizers 40, 42 to manifold 64. Devices 69, 69 are intended schematically to illustrate vented pressure-relief safety valves. Manifold 64 receives conduits 70, 72, and 74 for supplying reactant or sweep gases, e.g., CO 0 and N respectively. Elements designated as 76, 78, and 80 are intended schematically to indicate flow measuring and control devices for measuring and controlling respective gas flow in conduits 70, 72 and 74, respectively. Conduit 74 receives a gas stream from manifold 82. Manifold 82 also supplies conduit 84 which is equipped with on-off valve 86.
Manifold 64 empties into mix chamber which has a relatively large volume, about 1 gallon, and preferably includes a number of baffles 92. Mix chamber 90 is equipped with temperature regulating heating means 94, which temperature regulating device is diagrammatically illustrated. Mix chamber effluent is carried by way of conduit 96 from chamber 90, past on-off valve 98 into conduit 99 which is hermetically joined to coating chamber 100.
The temperature of the dilute gas stream being conveyed to chamber 100 is maintained below the deposition temperature, and below a temperature at which chemical reaction in the vapor phase is significant.
Coating chamber 100 is of relatively large volume, about four cubic feet including the volume of contents, and includes supports 102, 104 for supporting a plurality of lenses 10. In the illustrated embodiment, supports 102, 104 are shown highly perforated to facilitate gas movement around lenses 10. Elements 102, 104 are intended to schematically illustrate either supports or separators each of which is carrying a layer of lenses 10. It is noted that'a first layer of lenses 10 is supported on element 102 and a separate layer of lenses is supported on element 104. It is also noted that lenses 10 are separated from one another horizontally, as well, to provide ready access of the gas phase in chamber 100 to the faces of lenses 10. Chamber 100 vents through vented exit conduit 106 and the flow through exit 106 can be regulated by valve 108. Lenses 10 in chamber 100 are maintained at substantially constant temperature, e.g., 200C, by heater 110. The heater can be a high resistance type heater, microwave or similar heater.
Mechanical pump 112 can be used to facilitate flow through coating chamber 100, and to provide the necessary pressure increase to recycle a portion or substantially all of the gas stream through recycle line 116 back through the system. Element 114 represents a conventional liquid nitrogen trap for freezing substantially all of the condensibles out of the recycled stream.
Cooling means 120 schematically indicated as a coiled water-cooled tubing is provided to keep conduit 99 from being excessively heated due to conduction from chamber 100. Appearance of smoke emitting from conduit 99 indicates temperature of the gas stream is too high, and heat input must be reduced upstream.
EXAMPLE I To illustrate the simultaneous manufacture of a large quantity of glass filters with a band pass in the visible but strong absorption in the ultraviolet range of the spectrum, (e.g., filters used for sunglasses) the following procedure is used in accordance with this invention:
Cleaning of Lens The lens is cleaned in strong acid, e.g., concentrated sulfuric, nitric, or the like, to remove all possible organic and inorganic contaminants. This acid treatment is followed by a water rinse and a neutralizing step. To neutralize, the glass is immersed in a solution of ammonium hydroxide and hydrogen peroxide. A second water rinse follows, and the glass is dried in a solvent mixture that absorbs water clinging to the glass and allows flash drying Without residue. A preferred drying mixture is a mixture of ethanol, methanol, isoamyl acetate, and isobutanol in the ratio of 5:l:0.5:0.4. After drying the glass is ready for deposition.
Deposition The thus cleaned glass is transferred to supports 102, 104 in chamber 100 using care not to re-contaminate the surface to be coated, and is then heated to 200C. The process is started by flushing the system comprising manifold 82, conduit 80, 84, manifold 86, mix chamber 90, conduit 99, chamber 100 and vent 106 with a nitrogen sweep. However, any other inert gas such as helium, neon, or other noble gases can be used for the sweep. It is preferable that lines leading to and coming from vaporizers 40, 42 likewise be swept with an inert gas at the initial stage of the method. After the initial sweep is completed valves 86, 80 are closed, thus interrupting the flow of nitrogen. Valve 76 is opened and adjusted to provide a flow rate of 5,000 ml/min of carbon dioxide. Valve 78 is regulated to provide a flow rate of oxygen of 5 ml/min into manifold 64. Vaporizer 40 is charged with iron amyl-acetonate and is heated to elevated temperature somewhat below the atmospheric pressure boiling point of iron-amyl-acetonate. Vaporizer 40 is then swept with helium admitted from manifold 50 through conduit 52 at a flow of 5,000 ml/min regulated by adjustment of flow measuring and controlling device 56. Hence, the carbon dioxide, oxygen, and the helium carrying gaseous iron amyl-acetonate are thoroughly mixed in manifold 64 and in mix chamber 90. In mix chamber 90 the turbulent serpentine flow of the mixture through the tortuous path defined by baffle 92 not only thoroughly mixes the gas but assures thermal equilibrium as well. The resultant gas mixture is carried through conduits 96, 99 into reaction or deposition chamber 100. Thus in chamber 100 the concentration of inert sweep gas gradually decreases as additional quantities of the first deposition mixture heretofore described is admitted thereto. Conversely, the concentration of the deposition mixture in chamber 100 gradually increases as more and more of the initial inert sweep gas is vented. The glass substrates are maintained at approximately 200C throughout the deposition. During the ensuing period of time, a highest quality uniform coating of iron oxide forms on the exposed surfaces of substrate 10. I do not want to be bound by any theories as to the chemical mechanism by which the coating is formed in the method of this invention.
After lapse of a predetermined time, valves 56, 66 are closed and valves 68, 58 are opened. Valve 58 is adjusted to regulate the sweep flow through vaporizer 42 at about 5,000 ml/min. Vaporizer 42 had been previously charged .with chromium carbonyl and is maintained at a temperature somewhat below the boiling point of chromium carbonyl. Because of the high volume sweep rate, vaporizers 40, 42 are maintained at a temperature below the atmospheric pressure boiling point of the material being vaporized.
Thus, the primary chromium carbonyl-containing helium stream now entering manifold 64 through conduit 62 is likewise mixed with the secondary carbon dioxide-oxygen stream which is maintained at the constant flow levels defined above, and the primary and secondary streams are thoroughly mixed and the temperature is equilibrated in mixing chamber 90. The mixture resulting from the primary and secondary streams may be considered to be a tertiary stream containing chromium carbonyl and oxygen in low level. The concentration of the iron amyl-acetonate in the gas in manifold 64 and mix chamber 70 abruptly drops and the concentration of chromium carbonyl in manifold 64 and mix chamber 90 abruptly increases to its equilibrium level. The chromium carbonyl-containing tertiary gas stream is conveyed through conduit 99 into largevolume deposition chamber 100. It will be appreciated that the concentration of iron amyl-acetonate in the reaction chamber 100 will decline gradually, relatively speaking, as the concentration of chromium carbonyl in the reaction chamber 100 gradually increases to its equilibrium level, i.e., about the concentration in the tertiary stream. The deposition of the respective films on respective substrates 10 during this relatively short period of time in which a mixture of iron amylacetonate and chromium carbonyl is available results in the presence of transition zones 30, 32, 34 and 36. At this stage of the method described immediately hereinbefore, the period of time during which iron amylacetonate concentration in chamber 100 is decreasing and in which the concentration of chromium carbonyl in chamber 100 is increasing depends primarily on gas flow rates, since the volume of chamber 100 is constant. This reliably results in the formation of a uniform zone 30 between layers 18-20 in separate runs, provided gas flow rates and temperatures are the same in each separate run. When the iron acetylacetonate is swept out of chamber 100 and chromium carbonyl reaches equilibrium concentration, a layer which is substantially chromium oxide is deposited. After lapse of another predetermined period of time, during which a high quality chromium oxide layer is deposited,-
valves 68, 58 are closed. Valves 56, 66 are immediately reopened and the flow of helium through vaporizer 40 is regulated to again provide 5,000 m./min. The concentration of chromium carbonyl in manifold 64 and mixer very abruptly drops to substantially zero, and the concentration of iron amyl-acetonate very abruptly increases to substantially its equilibrium level. At this stage of the method, the primary gas stream again contains iron acetyl acetonate, the secondary gas stream still contains a low level of oxygen, and the tertiary stream leaving mixer 90 is a homogeneous mixture of the two streams. However, when the new iron amylacetonate carrying tertiary stream is discharged into chamber 100, there is again a relatively gradual increase in the concentration of iron amyl-acetonate concentration, and the chromium carbonyl concentration gradually decreases. At this stage in time in which the atmosphere of chamber provides both iron amylacetonate and chromium carbonyl, the second transition zone 32 between layers 20, 22 is being formed.
The above procedure in which the gas streams are alternately routed through vaporizers 42, and 40 are repeated to provide a total number of five layersthree of which are iron oxide and two of which are chromium oxide, each having relatively narrow transition zones therebetween, was carried out in a total time of less than 1 hour. All the lenses in chamber 100 were identically and uniformly coated.
The procedure described in Example I hereinbefore includes a high velocity sweeps passing through the vaporizers. It is not essential that such a sweep pass through the vaporizer in accordance with this invention. It is essential however that the volatile reactant be thoroughly admixed and diluted with the inert carrier stream prior to contacting the substrate. Thus, for example, introduction of pure volatile reactant directly into a large volume gas stream passing through manifold 64 is within the concept of this invention, although such operation is not most preferred. Also, it is apparent to one skilled in the art, that heat is not essential in the vaporizer, in all instances. However, for ease of control and reproducibility, it is preferred that the vaporizer be operated at sufficiently high temperature for it to be maintained in a substantially dry condition with a relatively high velocity gas through-put while liquid volatile reactant is being continuously charged thereto at the required constant, although relatively slow, rate of addition.
It is essential in accordance with the present invention that the total concentration of the reactants in the inert carrier gas stream be below percent volume/- volume. It is more preferred that the concentration of the reactants in the carrier gas stream be less than 1 percent v/v, and use of concentrations of individual reactants at less than 0.1 percent v/v is most preferred. Though it may appear to be inefficient to provide the coating material at these low concentrations in the gas phase, at least in terms of mass-transfer, I now appreciate that use of the low concentration reactant streams in accordance with this invention provides layer uniformity and quality which was heretofore unattainable. This is particularly significant in deposition chambers in which a large number of substrates are being coated simultaneously, or in which a large number of substrates are being treated simultaneously to provide reproducible and substantially identical layers, particularly in fine or micro-miniature patterns. By not permitting the relatively dilute reactant carrier gas to stagnate, and by providing positive sweep of the carrier gas over the substrates, extremely uniform, high quality layers are deposited. While 1 do not want to be bound by any theories as to the mechanism involved, it is my belief, based on repeated observation, that one of the factors responsible for the high quality and high uniformity of the product of this invention is the fact that with the dilute gas streams, localized variations in vapor phase composition is, relatively speaking, eliminated as a source or cause for nonuniform layer deposition, and undesirable vapor phase reaction is virtually eliminated. While 1 do not want to be bound by any particular theory as to why my method works so well, I recognize the possibility that the reactions take place exclusively in an adsorbed phase on the surface of the substrate in my method. It is noted that even at the most preferred concentrations, e.g., less than 1 percent v/v of the reactants or less, more than adequate masstransfer is provided by supplying the dilute sweep in high velocity.
The foregoing example is for illustrative purposes only and is not intended to suggest any limit to the identity of the sweep gases orreactant compounds which are useful in accordance with this invention. Any metal-eontaining vaporizable material can be charged to vaporizers 40, 42, providing that material decomposes or deposits on the hot substrate surface a desired layer composition. Indeed, the number of vaporizers used and the number of kinds of layers can be greater than the two which are illustrated in the example. A larger number of compositions can be conveniently deposited as an optical filter. in accordance with this invention.
Other volatile material which can be used to provide an iron oxide layer include any of the volatile iron organo-metallic compounds, for example, iron pentacarbonyl, when used in conjunction with oxygen in the second sweep stream. Likewise, any volatile chromium compound can be used in vaporizer 42, for example, chromyl chloride. Thus, it is not necessary, in accordance with this invention, to limit the compounds utilized to organo-metallic compounds since the compounds which are used can be either organo-metallic or inorganic. The metallic compounds employed in this invention are those which exhibit a substantial vapor pressure, preferably in excess of about 40 mm Hg. at
relatively low temperatures, e.g., 200C. However, compounds having lower vapor pressures are also useful, e.g., silver formate has a low vapor pressure at 200C, and such compound is useful for doping films in the vapor phase method of this invention. Procedures for doping will be discussed in greater detail hereinafter. The secondary carrier gas need not be limited to the carbon dioxide disclosed in the example but can be nitrogen, oxygen, H 0 or similar gases. Oxygen is used only in very low levels and only when an oxide coating is desired.
Thus, in the illustrated embodiments, the primary metal-containing gas sweep stream is mixed with a secondary gas stream, in accordance with this invention, which secondary stream includes a low concentration level of a second reactant. The second reactant which was selected to provide an oxide layer in the illustrated embodiment set forth above is oxygen. However, if it is desired that the deposited layer be a sulfide, selenide, telluride, nitride, arsenide, phosphide, or other desired compound, it is only necessary to substitute for the low level of oxygen in the secondary stream a relatively low level of hydrogen sulfide, hydrogen selenide, hydrogen telluride, ammonia, arsine or phosphine, respectively, and the like. Thus, the identity of the material being laid down to provide the optical layer can be changed by varying the makeup of the gas stream entering the deposition chamber either by varying the identity of the material being vaporized in vaporizers 40, 42 and the like, or alternatively, in accordance with this invention, the material entering the manifold from the vaporizers, e.g., from vaporizer 40, can remain constant. in the latter instance the second reactant, e.g., 0 being mixed with the CO can be eliminated and can be replaced by similar amounts of a third reactant, e.g., H S, for mixing with the CO to provide an H S-CO secondary stream. Alternating the makeup of the secondary stream in this manner would provide alternating layers of iron oxide and iron sulfide, for example.
It is also contemplated that a doped layer can be deposited using the method of this invention by adding very low levels of volatile activator-metallic compounds to either the compound in vaporizer, or into the secondary reactant gas stream. For example, tetraethyl lead can be vaporized in a N stream at 5,000 ml/min sweep at 25C vaporizer temperature. The secondary reactant could be H S, at 5 m./min instead of O Argon would be used instead of CO ln second vaporizer, silver or copper activator precursor, e.g., copper formate is vaporized in argon or helium at 100C temperature or silver chloride is vaporized at 400C.
In some instances the metal, itself, can be vaporized and diluted in accordance with the present invention for incorporation into a layer, especially as a dopant. It is also contemplated that an optical component such as a filter comprising a single deposited optical filter layer can be deposited in accordance with this invention.
An example of an application of the method of this invention to the deposition of a layer coating which exhibits a continuous and continual transition from one density to another density is the use of this invention to provide a coating on glass fiber optic fibers. For'example, in accordance with the procedure illustrated in the previously set forth detailed example, a layer of material having a relatively low index of refraction is initially deposited on the glass fiber, and the concentration of thelayer precursor in the sweep gas phase is gradually decreased over a relatively long period of time, e.g., a half hour. Simultaneously the concentration of a second layer precursor,-i.e., one which provides a layer which exhibits a relatively high index of refraction, is gradually increased during the same period of time. This provides a transition zone layer or coating on the glass fiber which exhibits a low index of refraction of the coating gradually increasing with increased distance from the fiber through the coating layer. If desired, a mirror layer can be deposited at the outer surface of the thus coated fiber as described herein, also in accordancewith this invention. Such coatings improve reflection characteristics and absorbance to prevent interfere'nce from neighboring fibers.
The method of this invention is also highly useful for depositing opaque, or mirror layers, as well as for depositing transparent layers. For example, in accordance with this invention, an exterior oxide layer of a desired metal is deposited as disclosed herein. The oxide is then reduced in an oxygen-free atmosphere, e.g., with hydrogen, ammonia, carbon monoxide, or the like, most preferably by introducing the reducing gas into a high velocity stream in low concentration, e.g., at the ml/min rate in a 10,000 ml/min sweep.
It is preferably to provide an additional oxide layer on top of the reduced metal layer to protect or shield it from atmospheric corrosion. However, osmium or rhodium mirrors do not need an oxide shielding layer deposited on the top thereof. However, these layers, i.e., osmium or rhodium, are preferably laid down on a foundation layer of an oxide of tin, titanium, chromium, or iron. A preferred over-layer for use on a mirror film layer is silicon dioxide. For some mirrors, e.g.,
an iron mirror, flushing with carbon dioxide prior to exposure to atmospheric oxygen passivates the mirror metal for at least temporary corrosion protection. In the latter case it is not necessary to deposit an oxide layer before exposing the metal to atmospheric oxygen.
To employ the method of this invention to manufacture electro-optical readout systems and the like such as gratings, a thin film of photo-sensitive resist can be applied to a glass substrate cleaned as in Example I. In accordance with well known conventional procedures a photoresist relief pattern (either positive or negative) is generated and developed on the substrate, e.g., see Photo Fabrication pamphlets numbered P. 7 and P. 91 respectively published by Eastman Kodak Company, the contents of which are incorporated herein by reference thereto. Substrates so patterned, are transferred to coating chamber and the flush and layer forming procedure of Example I is repeated to produce a desired layer. After a layer is deposited, the stencil is removed by a conventional procedure.
For transparent gratings or patterns, the preferred layer or layers which are deposited is a metal oxide, e.g., an oxide of iron, chromium, cobalt, nickel, uranium, copper, manganese, vanadium, rare earths, lead, etc. For absorption characteristics alone, a single layer can suffice. lf reflection or dichroic characteristics are desired, multiple layers are used, e.g., as illustrated in Example I. For opaque patterns, a reactant composition is selected to produce an oxide which is then reduced by dilute reducing gas to a metallic mirror deposit.
ln producing the metallic mirror layer any reducing gas sufficiently reductive to reduce the specific metallic oxide to the metal can be used. For example, to produce an iron mirror,an exterior iron oxide layer is reduced, in accordance with this invention, using hydrogen, carbon monoxide, methane, or the like. lt is preferred that the sweep atmosphere in which the reducing gas is transported be nitrogen. lf passivation is required, e.g., with an iron mirror, carbon dioxide sweep over the coating or deposition is adequate for at least temporary protection. A silicon dioxide layer or other protective oxide layer is also eminently satisfactory. A preferred method for providing a silicon dioxide overcoat for a mirror layer, in accordance with this invention, includes vaporizing tetraethoxysilanol in a vaporizer with an inert gas sweep, and in a second dilute sweep, adding oxygen, and admixing these streams under the conditions described in Example I herein.
To provide an electro-optical layer, tetraethyl lead can be vaporized in a high velocity inert gas sweep through vaporizer and low concentrations of hydrogen sulfide provided in the second sweep gas. Silver chloride or copper formate can be vaporized at an extremely low rate, in a second vaporizer, as described hereinbefore, to deposit minute levels of silver or copper dopant in the lead sulfide layer. The resulting silver or copper doped lead sulfide can function as an optical sensor providing electrical readout.
The table is presented herein to illustrate the farreaching applicability of the method of this invention, with respect to elemental constitutents of the layer compound. In the table, illustrative volatile compounds or elements are set forth, and arranged in alphabetical order according to the chemical symbol for the element involved. All temperatures are suggested temperatures and are provided only for the purpose of illustration, and not for limitation. In the Table, Dop. is an abbreviation for Dopant, Min, for Mirror, and Trans. for transparent layer. A Yes under the respective column heading indicates the material set forth is readily used in accordance with this invention to provide a dopant, opaque layer (mirror) or transparent layer, respectively.
The entire process of this invention is preferably carried on at substantially atmospheric pressure. However, it is not essential that all portions of the system be maintained at precisely atmospheric pressure. In fact, it is highly desirable to provide the input gases at a pressure somewhat above atmospheric pressure, e.g., 5-l 5 psig, so that the flow rates through the system can be maintained at constant value. Also, to provide a higher TABLE Metal Material Being Vap. Deposit Formula Metal Name Vaporized Temp. Temp. Dop. Mir Trans.
Ag Silver Silver Chloride 400 300 Yes Yes Al Aluminum Al l 50 200 Yes Yes As Arsenic Arsine (AsH gas 200 Yes Yes Chloridc(AsCl 30 200 Yes Yes Av Gold (C H P-AuCl 30 I Yes Yes Be Beryllium diethyl beryllium, 30 200 Yes Yes dimethyl, I00 200 Yes Yes ditert butyl 30 200 Yes Yes Bi Bismuth BiH gas 200 Yes Yes BiCl; 200 200 Yes Yes 8 Boron lhH gas 300 Yes Yes Cd Cadmium Metal 400 Cond Yes Co Cobalt Co(CO) 30 200 Yes Yes acetylacetonate 30 200 Yes Yes Cr Chromium dicumene chromium 50 200 Yes Yes Yes acetyl acetonate 100 250 Yes Yes Yes ehromyl chloride 30 300 Yes Yes Yes Cr(CO), 30 300 Yes Yes Yes Cs Cesium metal 400 Cond Yes 300 Cu Copper Formate I00 300 Yes Yes Yes acetyl acetonate I00 300 Yes Yes Yes Fe lron Fe(CO) 30 200 Yes Yes acetylacetonate 300 200 Yes Yes Ge Germanium GcH, gas 300 Yes Yes Yes Gel: 30 300 Yes Yes Yes Ge(OC H,) C H 400 Yes Yes Yes Hg Mercury metal 200 100 cond. I00
diethyl mercury 50 200 Yes No Yes I lodinc lodine(l,) I00 40-60 Yes K Potassium metal 300 Cond. Yes Mg Magnesium metal 500 Cond. Yes Mn Manganese Dicyclopentadienyl 30 200 Yes Yes Mo Molybdenum Mo(CO) 200 Yes Yes Ni Nickel Ni(CO) 30 200 Yes Yes acetylacetonate I00 300 Yes Yes Os Osmium 0s(C0),Cl, I00 300 Yes Yes P Phosphorous metal 200 I50 Yes PHg gas 200 Yes Yes Pb Lead tetraethyl 30 300 Yes Yes tetramethyl 30 300 Yes Yes Rb Rhubidium metal 400 Cond. Yes Rh Rhodium RhCl 03 CO 50 200 Yes Yes S Sulfur Sulfur 300 Cond. Yes Sb Antimony SbCl 100 500 Yes Yes Yes SbH gas lOO Yes Yes Yes Se Selenium Sell gas 300 Yes Yes Yes Si Silicon metal 500 Cond. Yes
Si(OC,H 30 300 Yes Sn Tin tetramethyl 60 200 Yes Yes tetraethyl 30 200 Yes Yes triethylchloride 30 200 Yes Yes Te Tellurium metal 500 Cond. Yes Ti Titanium tetraethyl 30 300 Yes Yes We Tungsten W(CO),, 50 200 Yes Yes Zn Zinc metal 500 Cond. Yes
50 200 Yes diethyl mass transfer rate, pressures higher than atmospheric pressure can be employed, providing the essential concentration limitations are observed though elevated pressure is not necessary. For example, pressures in the range 0.1 to 4 atmospheres are eminently satisfactory.
From a consideration of the deposition temperatures set forth in the table herein it is apparent that the deposition temperatures useful in accordance with this invention are preferably in the range 40 to 400C. The more preferred temperatures range from about 100 to 280C inclusive. Higher deposition temperatures are sometimes useful. It is important that the dilute gas stream moving towards chamber 100 be maintained at temperatures below deposition temperatures when a chemical reaction is involved in the deposition mechanism. Those embodiments in which the primary and secondary streams carry first and second reactants which result in a third material in the layer, e.g., as in the detailed illustrated example herein, are of this type. However, when condensation is involved, e.g., when elemental metal is vaporized and condensed, it is imat least at a reduced rate if it is intended to change over from one deposition layer to another, in order to reduce the time in which the transition zones, e.g., 30, 32, 34, 36, are being laid down.
Also, although the detailed example set forth above is a preferred embodiment in which relatively narrow transition zones are automatically laid down, it is not essential that in all instances such transition zones be laid down. For example, after the required depth of a layer, e.g., 18, is deposited, the entire system could be flushed with an inert sweep gas, e.g., C0,, or N (or operated with valves 66, 68 closed when trap 114 is operating and recycle mode prevails) and the second deposition material, e.g., chromium carbonyl, with low level of oxygen, can be introduced into chamber 100 in a dilute sweep flow with the result that no iron amyl acetate is present during deposition of the second layer, e.g., chromium oxide. Such an embodiment provides sharp demarcation between the respective iron oxide and chromium oxide layers. However, as set forth above, it is preferred that the operation of the apparatus. of this invention be as described since this provides the relatively narrow transition zones 30, 32, 34, 36 which, for some purposes, are believed to be highly desirable.
In addition, it is within the overall scope of this invention that the magnitude of zones 30, 32, 34, 36 can be increased by providing a longer period of time in which several deposition materials are being admitted simultaneously to manifold 64, e.g., through both conduits 60, 62, inthe example. Such an embodiment in which several materials are being vaporized simultaneously requires careful'control of vaporizer input rates in order to assure a high degree of reproductivity from batch to batch, however. Since the flow rates set forth in the detailed example herein are constant, and since a given apparatus will be constant with respect to its gas-occupied volume and other structural dimensions, controlling the other parameters, i.e., time, and temperature, provides for highly reproducible dimensions of layers and transition zones. Controlling the period of time in which the deposition material is admitted to manifold 64 effectively and reproducibly controls the magnitude of the corresponding layer being laid down on lenseslO, given constant temperature of substrate from layerto layer.
The substrates which can be used in accordance with this invention include glass, ceramic, and metal, e.g., stainless steel, as well as plastics, e.g., teflon, phenolics, etc., and the like. When plastic substrates are used, it is preferred that they be selected from the class of plastics known as thermosets.
The method of this invention provides uniform layers regardlessof contour, shape, or line-of-sight accessibility of the substrate surface and regardless of number of substrates being processed. The method of this invention is likewise singularly beneficial in depositing minute microscopic patterns, e.g., microminiature patterns, on a substrate. In this regard, this invention is not directed to any particular method of masking or shielding the substrate whereby a particular pattern can be laid down. It is preferred, however, that photographyrelated techniques be employed to develop masks or shields on the substrate. The combination of the conventional photo-developed pattern generation technique with the dilute sweep layer deposition method of this invention, produces a new dimension in manufacture of microminiature patterned layers involving no manual manipulations relating to the production of the layer design on the substrate, only those manipulations involving handling of the substrate itself. Hence the resulting layers are deposited in patterns which are extremely clean-edged even under high magnification.
Thus, it will be apparent from aconsideration of the foregoing disclosure that this invention provides a substantial advance in the art of simultaneously manufacturing large numbers of layered products, e.g., selectively deposited patterns, optical filters, such as di- 14 chroic' filters, and for simultaneously depositing such layers on all surfaces of the products unless those surfaces are appropriately shielded.
It will also be apparent from the foregoing that the nature of the apparatus required is very similar to that used in ordinary chemical manufacturing processes, particularly vapor phase processes, and that the nature of the regulation and control of the process is such that it readily lends itself to automatic control and other highly automated procedures. Moreover, the level of technical skill required by an operator is low, and yet in spite of this high reproducibility and a high level of process control is conveniently practicaL' Also, since the deposition does not depend on a lineof-sight travel of the material being laid down, it is found that the coating being laid down on lenses 10 in accordance with this invention is highly uniform regardless of the shape of the face of the substrate being coated.
1. A method of depositing a micro-thin opaque or transparent layer on a substrate comprising: maintaining said substrate at a deposition temperature between [00C and 300C; forming a dilute gaseous mixture of vapor of a first metal-containing reactant in an inert gas stream, forming a second gaseous mixture comprising vapor of a second reactant in an inert gas stream, admixing said first and second mixtures, and contacting the resulting admixture in a high velocity stream with said substrate while it is at said deposition temperature at a pressure in the range 0.1 to 4 atmospheres, the total concentration of the reactants in the resulting admixture being less than 5 percent v/v and continuing said contacting until said layer is formed on said substrate.
2. The method of claim I in which said contacting takes place at a temperature in the range l00280C., inclusive.
3. The method of claim 1 in which the first reactant is a volatile organo-metallic compound and the second reactant is a member selected from .the group consisting of oxygen and hydrogen sulfide.
4. A method of claim 1 in which the product is a photoelectric element and in which the resulting gaseous admixture also includes low concentration of a dopant in a concentration less than 0.1 percent v/v.
5. The method of claim 1 in which the substrate is glassfiber.
6. A method of depositing micro-thin oxide layer on a substrate comprising: sweeping a substrate which is maintained at a temperature between l00280C with a sweep gas containing an organo-metallic compound at a concentration less than 5 percent v/v in an inert carrier gas therein, said gas sweep containing oxygen at a concentration less than 0.1 percent v/v, and continuing said sweeping for a period of time sufficient to form said layer on said substrate.
7. A method of making an opaque film on a substrate comprising: forming a micro-thin oxide layer on the substrate, by a method comprising maintaining the substrate at a deposition temperature between C to 300C, sweeping said substrate with a dilute gaseous mixture of a metal-containing vaporizable material, and oxygen in an inert carrier gas stream, said material and oxygen being present in the inert carrier gas stream in a total concentration not exceeding 5 percent v/v, said sweeping phase taking place at a pressure between 0.1 and 4 atmospheres; and continuing said sweeping for a period of time until said micro-thin oxide layer is formed on said substrate; heating the resulting substrate to a temperature in the range l280C and sweeping the thus heated substrate with an inert gas carrier containing a reducing reactant in an amount less than percent v/v therein.
8. A method of manufacturing an optical filter which includes a multiple layer light filtering coating on the surface of an optical substrate, which method comprises the steps of:
l. placing the optical substrate in a vented chamber having a relatively large volume;
2. maintaining the optical substrate at an elevated temperature between 100C and 300C;
3. sweeping the atmosphere from the chamber with an inert gas;
4. Continuously introducing into the chamber a first dilute gaseous coating mixture including at least one gaseous metal-containing material and a second reactant in an inert carrier gas, said mixture being capable of depositing at said elevated temperature on said substrate a film containing a first metal compound while continuously venting gas from said chamber, and continuing the continuous introducing and venting of step 4 for a period of time sufficient for a first layer to form on said substrate; and
5. introducing into the chamber a second gaseous coating mixture including at least one gaseous metal-containing material and a third reactant in an inert carrier gas, said second mixture being capable of depositing at said elevated temperature a film containing a second metal compound, thereby gradually reducing the concentration of said first coating mixture, while increasing the concentration of said second coating mixture, wherein the total concentration of said metal-containing materials and said second reactants in said coating mixture in steps 4 and 5 is less than 5 percent v/v while continuously venting gas from said chamber; and continuing the continuous introducing and venting of step 5 for a period of time sufficient for a second layer to form on the first layer.
9. A method of manufacturing multiple layer optical filters comprising the steps of:
forming a first dilute gaseous mixture of a first metallic compound in a large amount of inert carrier gas;
admixing with said first gaseous mixture a gaseous member selected from the group H 5, Asl-l PH NH;,, and H Te, to provide a coating-gas stream;
said first metallic compound being reactive with said gaseous member to develop a layer on said substrate; and
moving said coating gas stream over a surface to be coated, said surface being at a temperature in the range from 100C to 280C, wherein the total concentration of said compound and said member in said stream is 5 percent v/v or less, said moving continuing until an optical filter layer is formed on said substrate.
10. A method of manufacturing dichroic filters comprising the steps of:
heating filter substrates in a coating chamber to a temperature in the range l00-280C;
said chamber being maintained at substantially atmospheric pressure;
forming a first dilute gaseous admixture of a first reactive metallic compound and chemically inert sweep gas; admixing with said first admixture a relatively small amount of a second reactive compound, which second reactive compound is characterized as coacting with said first admixture to deposit a first filter layer material on said heated substrate, the mixture resulting being a second gaseous mixture;
sweeping said second mixture over the heated substrates by discharging the second mixture into the coating chamber and continuously venting gas from the coating chamber;
forming a third gaseous admixture of a vaporizable metallic compound and inert carrier gas, admixing the third mixture thoroughly with a relatively small amount of fourth reactive gaseous compound characterized by its ability to co-act with said third mixture to form a second filter layer material, on said first filter layer material, the admixing of said fourth compound with said third mixture resulting in a fifth gaseous mixture; and sweeping the fifth gaseous mixture over the substrate by discharging the fifth gaseous mixture into the coating chamber and continuously venting the chamber, wherein the total concentration of reactants in any substratecontacting gas stream is 5 percent v/v or less, said sweeping continuing in each instance, until a respective filter layer is deposited.
11. A method of selectively depositing a micro-thin layer on a substrate comprising: maintaining the substrate at an elevated temperature between C and 300C; contacting said substrate with a dilute gaseous mixture containing a deposit precursor consisting of a metal-containing material in vapor form and a second reactive compound characterized as co-acting with said material to form a first filter layer on the heated substrate in a concentration not exceeding 5 percent v/v, and continuing the contacting for a period of time sufficient for a layer to be deposited on said substrate, said depositing taking place through stencil means for preventing deposition in nonselected areas, and for depositing said layers in selected areas.
12. A method of depositing a micro-thin optical layer on a substrate comprising: maintaining said substrate at a deposition temperature between 100C and 300C; sweeping said substrate with a sweep of a dilute gaseous mixture containing a depositprecursor comprising a metal-containing vaporizable material in vapor form and a second reactant capable of reacting with the precursor to produce an optically active layer on said substrate, said reactants being in an inert carrier gas stream in which the total concentration of deposit precursor and second reactant does not exceed 5 percent v/v; and continuing said sweeping for a period of time sufficient to form an optically active layer on said substrate.
13. The method of claim 12 in which said sweeping takes place at a pressure between 0.l and 4 atmospheres, inclusive.
14. The method of claim 12 in which a gaseous mixture includes a plurality of reactants which produce a layer having a composition which is different from any of the reactants, and in which gaseous mixtures a concentration of no one reactant is in excess of l percent v/v.
15. A method of forming a uniform oxide coating on a substrate comprising: maintaining said substrate at a deposition temperature between 100C and 300C; sweeping said substrate with a dilute gaseous mixture of a metal-containing vaporizable material, and oxygen in an inert carrier gas stream, said material and oxygen being present in said inert carrier gas stream in a total concentration not exceeding percent v/v, said sweeping taking place at a pressure between 0.1 and 4 atmospheres; and continuing said sweeping for a period of time until a metal oxide layer is formed on said substrate.
16. The method of claim 15 in which gaseous mixture the concentration of no one reactant is in excess of 1 percent v/v.
17. The method of claim 15 in which the metal containing material is selected from the group consisting of silver chloride, Al l arsenic chloride, arsine (C H P-AuCl, dimethyl beryllium, ditert butyl beryllium, Bil-l BiCl B H cadmium metal, cobalt acetylacetonate, Co(CO) dicumene chromium, chromium acetyl acetonate, chromyl chloride, Cr(CO) cesium metal, copper formate,copper acetyl acetonate, Fe( CO) iron acetylacetonate, iron amyl-acetonate, GeH,,, Gel mercury metal, diethyl mercury, iodine (l potassium metal, magnesium metal, manganese dicyclopentadienyl, Mo(CO) Ni(CO) nickel acetylacetonate, Os(CO) Cl phosphorous, Pl-l tetraethyl lead, tetramethyl lead, rhubidium metal, RhCl O-S CO,
sulfur, SbCl SbH SeH silicon metal, Si(OC l-l tetramethyl tin, tetraethyl tin, tin triethylchloride, tellurium metal, tetraethyl titanium, W(CO) zinc metal, diethyl zinc, and diethyl beryllium.
18. A method of depositing an optically active layer on a substrate comprising: maintaining substrate at a deposition temperature between C and 300C; sweeping said substrate with a sweep of dilute gaseous mixture containing a primary and secondary reactant in an inert carrier gas stream wherein said primary reactant is a metal-containing vaporizable material, and wherein said secondary reactant is a member selected from the group consisting of oxygen, hydrogen sulfide, hydrogen selenide, hydrogen telluride, ammonia, arsine, and phosphine, and wherein said reactants are present in a concentration not exceeding 5 percent v/v, and continuing said sweeping for a period of time sufficient to form an optically active coating on said substrate.
19. The method of claim 18 wherein said primary reactant is a member selected from the group consisting of silver chloride, A1 1 arsenic chloride, arsine, (C H P'AuCl, dimethyl beryllium, diethyl beryllium, ditert butyl beryllium, BiH BiCl B H cadmium metal, cobalt acetylacetonate, Co(CO) dicumene chromium, chromium acetyl acetonate, chromyl chloride, Cr(CO) cesium metal, copper formate, copper acetyl acetonate, Fe(CO) iron acetylacetonate, iron amyl-acetonate, GeH Gel mercury metal, diethyl mercury, iodine (l potassium metal, magnesium metal, manganese dicyclopentadienyl, Mo(CO) Ni(- CO) nickel acetylacetonate, Os(CO) Cl phosphorous, PH tetraethyl lead, tetramethyl lead, rhubidium metal, RhCl O'3 CO, sulfur, SbCl SbH SeH silicon metal, Si(OC H tetramethyl tin, tetraethyl tin, tin triethylchloride, tellurium metal, tetraethyl titanium,
W(CO) zinc metal, and diethyl zinc.