Coatings for microelectronic devices and substrates

Abstract: The present invention relates to a method of forming a ceramic or ceramic-like coating on a substrate, especially electronic devices, as well as the substrate coated thereby. The method comprises coating said substrate with a solution comprising a solvent, hydrogen silsesquioxane resin and a modifying ceramic oxide precursor selected from the group consisting of tantalum oxide precursors, niobium oxide precursors, vanadium oxide precursors, phosphorous oxide precursors and boron oxide precursors. The solvent is then evaporated to thereby deposit a preceramic coating on the substrate. The preceramic coating is then ceramified by heating to a temperature of between about 40°C. and about 1000°C. This coating, moreover, may be covered by additional passivation and barrier coatings.

Description: This invention relates to the application of ceramic or ceramic-like coatings on substrates such as electronic devices. These coatings comprise materials such as mixed oxides of amorphous silica and a modifying ceramic oxide, silicon, silicon carbide, silicon nitride and silicon carbonitride. Electronic devices, to be serviceable under a wide variety of environmental conditions, must be able to withstand moisture, heat and abrasion, among other stresses. A significant amount of work has been reported directed toward various protective measures to minimize the exposure of these devices to the above conditions and thereby increase their reliability and life. Most of these measures, however, suffer from various drawbacks. For instance, early measures involved potting electronics within a polymeric resin and, thereby, reducing environmental exposure. These methods proved to be of limited value, however, since most resins are not impermeable to environmental moisture and generally add extra size and weight. A second method of protection involves sealing the device within a ceramic package. This process has proven to be relatively effective in increasing device reliability and is currently used in select applications. The added size, weight and cost involved in this method, however, inhibit widespread application in the electronic industry. Recently, the use of lightweight ceramic coatings has been suggested. For instance, Haluska et al. in U.S. Patent No. 4,756,977 disclose silica coatings produced by applying solutions of an hydrogen silsesquioxane resin to an electronic device, and then ceramifying the coatings by heating to temperatures of 200-1000°C. This reference (Maluska) also describes the application of other coatings containing silicon carbide, silicon nitride or silicon carbonitride onto the initial silica layer for added protection. The ceramic coatings produced thereby have many desirable characteristics such as microhardness, moisture resistance, an ion barrier characteristic, adhesion, ductility, tensile strength and thermal expansion coefficient matching, which provide excellent protection to the underlying substrate. Haluska et al. in U.S. Patent No. 4,753,855 (EP-A-0270263) also proposed the application of solutions comprising hydrogen silsesquioxane resin (H-resin) and metal oxide precursors of titanium, zirconium and aluminum to a substrate and pyrolysing said substrate to temperatures of 200-1000°C to form a mixed oxide ceramic coating. EP-A-0323103 (Haluska et al) further proposed a process for forming on a substrate a ceramic coating which process comprises: (A) applying a flowable solution comprising hydrogen silsesquioxane resin to the substrate; (B) drying the resin solution to deposit a hydrogen silsesquioxane resin on the substrate; and (C) heating the coated substrate in a substantially ammonia atmosphere to a temperature sufficient to produce a ceramic coating on the substrate. The present inventor (Loren Andrew Haluska) has now unexpectedly found that the oxide precursors of tantalum, vanadium, niobium, boron and/or phosphorus can be mixed with hydrogen silsesquioxane resin to form a soluble preceramic mixture which can be applied to a substrate and pyrolysed to yield a ceramic or ceramic-like coating on said substrate. The present invention relates to a method of forming a ceramic or ceramic-like coating on a substrate, especially electronic devices, as well as the substrate coated thereby. The method comprises coating said substrate with a solution comprising a solvent, an hydrogen silsesquioxane resin and a modifying ceramic oxide precursor which is a metal or non-metal composition having one or more hydrolysable groups bonded to a metal selected from tantalum, niobium and vanadium or a non-metal selected from boron and phosphorus, said modifying ceramic oxide precursor being selected from tantalum oxide precursors, niobium oxide precursors, vanadium oxide precursors, phosphorus oxide precursors and boron oxide precursors. The solvent is then evaporated to thereby deposit a preceramic coating on the substrate. The preceramic coating is thereafter ceramified by heating to a temperature of between 40°C and 1000°C, whereby the desired ceramic or ceramic-like oxide coating is formed on said substrate. The present invention also relates to the formation of additional ceramic or ceramic-like coatings on the coating formed above. In a dual layer system, the second passivation layer may comprise silicon-containing coatings, silicon-carbon-containing coatings, silicon-nitrogen-containing coatings, silicon-carbon-nitrogen-containing coatings or an additional silicon dioxide and modifying ceramic oxide coating. In a triple layer system, the second passivation layer may comprise silicon-carbon-containing coatings, silicon-nitrogen-containing coatings, silicon-carbon-nitrogen-containing coatings or an additional silicon dioxide and modifying ceramic oxide coating, and the third barrier coating may comprise silicon coatings, silicon-carbon-containing coatings, silicon-nitrogen-containing coatings and silicon-carbon-nitrogen containing coatings. The additional coating layers described above may be deposited using a number of techniques including, but not limited to, chemical vapour deposition, plasma-enhanced chemical vapour deposition, metal-assisted chemical vapour deposition or ceramification of a preceramic polymer. The present invention also relates to an homogeneous liquid composition for use in forming a ceramic or ceramic-like coating on a substrate, said composition comprising a solvent, an hydrogen silsesquioxane resin and a modifying ceramic oxide precursor which is a metal or non-metal composition having one or more hydrolysable groups bonded to a metal selected from tantalum, niobium and vanadium or a non-metal selected from boron and phosphorus, said modifying ceramic oxide precursor being selected from tantalum oxide precursors, niobium oxide precursors, vanadium oxide precursors, phosphorus oxide precursors and boron oxide precursors. The present invention is based on the discovery that an hydrogen silsesquioxane resin (H-resin) and the oxide precursors of tantalum, vanadium, niobium, boron and phosphorus can be mixed in solution to form a soluble preceramic mixture which can be used to form ceramic or ceramic-like coatings. The resulting coatings are homogenous mixtures of silica and modifying amounts of one or more of the above oxides. Additionally, these coatings can be overcoated with various passivating and/or barrier coatings comprising silicon, silicon carbide, silicon nitride, silicon carbonitride or additional silicon dioxide/modifying ceramic oxide coatings as formed above. The single and multilayer coatings taught herein are particularly useful in providing protective coatings on electronic devices, electronic circuits or plastics including, for example, polyimides, epoxides, polytetrafluoroethylene and copolymers thereof, polycarbonates, acrylics and polyesters. The choice of substrates and devices to be coated by the instant invention is limited only by the need for thermal and chemical stability of the substrate at the temperature and atmosphere utilized in the present invention. The coatings taught herein may also serve, for example, as dielectric layers, interlevel dielectric layers, doped dielectric layers to produce transistor-like devices, pigment-loaded binder systems containing silicon to produce capacitor and capacitor-like devices, multilayer devices, 3-D devices, silicon-on-insulator devices, superlattice devices. As used in the present invention, the expression "ceramic-like" refers to those pyrolysed materials which are not fully free of residual carbon and/or hydrogen but which are otherwise ceramic in character; the expression "planarizing coating" refers to a coating which provides a surface barrier layer which is less irregular than the surface to be coated prior to application of the coating; and the expressions "electronic device" and "electronic circuit" include, but are not limited to, silicon-based devices, gallium arsenide-based devices, focal plane arrays, optoelectronic devices, photovoltaic cells and optical devices. As stated above, the ceramic or ceramic-like coating is formed by a process which comprises coating the substrate with a solution comprising a solvent, an H-resin and a modifying ceramic oxide precursor. The solvent is evaporated leaving a preceramic coating deposited on the substrate. The preceramic coating is then ceramified by heating to a temperature of between 40 and 1000°C. Hydrogen silsesquioxane resin (H-resin) is a preceramic polymer represented by the chemical formula (HSiO 3/2 ) n in which n is an integer greater than 10. H-resin can be manufactured by the method of Collins et al. in U.S. Patent No. 3,615,272 or that of Banks et al. in U.S.-A-5,010,159. It has recently been discovered that an especially preferred H-resin may be prepared by the method of Banks et al. supra in which the acid/ silane ratio is 6/1. This preferred H-resin tends to form coatings which are substantially crack-free. The modifying ceramic oxide precursors included in the present invention include compositions of various metals such as tantalum, niobium and/or vanadium as well as various non-metallic compositions such as those of boron or phosphorus. The expression "modifying ceramic oxide precursor", therefore, is meant to include such metal and non-metal compositions having one or more hydrolysable groups bonded to the above recited metals or non-metals. Examples of such hydrolysable groups include, but are not limited to, alkoxy, e.g., methoxy, ethoxy and propoxy, acyloxy, e.g., acetoxy, or other organic groups bonded to said metal or non-metal through an oxygen atom. These compositions must form soluble solutions when mixed with the H-resin, and must be capable of being hydrolysed, and subsequently pyrolysed, at relatively low temperatures and relatively rapid reaction rates to form modifying ceramic oxide coatings. Such a modifying ceramic oxide precursor is generally present in the preceramic mixture in an amount such that the final ceramic coating contains 0.1 to 30% by weight of modifying ceramic oxide. The solvent to be utilized in the instant invention may be any agent or mixture of agents which will dissolve the H-resin and modifying ceramic oxide precursor without gelation and without interfering with the ceramic coating. These solvents include, for example, aromatic hydrocarbons such as benzene or toluene, alkanes such as n-heptane or dodecane, ketones, esters or glycol ethers, in an amount sufficient to dissolve the above materials to low solids. For instance, enough of the above solvent may be included to form a 0.1-35 weight % solution. The H-resin and modifying ceramic oxide precursor may be simply dissolved in the solvent and allowed to stand at room temperature for a time sufficient to allow the modifying ceramic oxide precursor to react into the siloxane structure of the H-resin. Generally, a period of time greater than 2 hours is necessary for said reaction to occur. The solution may then be applied to the substrate as discussed infra . Alternatively, the modifying ceramic oxide precursor may be hydrolysed or partially hydrolysed, dissolved in the solution comprising the solvent and the H-resin, and then immediately applied to the substrate. Various facilitating measures such as stirring or agitation may be utilized as necessary to produce said solutions. The preceramic solution may optionally be catalysed by the simple addition of a platinum or rhodium catalyst which assists in increasing the rate and extent of ceramification. Any platinum or rhodium compound or complex which can be solubilized in this solution will be operable. For instance, an organoplatinum composition such as platinum acetylacetonate or rhodium catalyst such as RhCl 3 (CH 3 CH 2 CH 2 CH 2 S) 3 , obtained from Dow Corning Corporation, Midland, Mich. is within the scope of this invention. The above catalysts are generally added to the solution in an amount of from 15 to 200 ppm of platinum or rhodium, based on the weight of resin in solution. The preceramic solution is then coated onto the substrate. The method of coating may be, but is not limited to, spin coating, dip coating, spray coating or flow coating. The solvent in the solution is allowed to evaporate and a preceramic coating is thereby deposited. Any suitable means of evaporation may be utilized such as simple air drying by exposure to an ambient environment or the application of a vacuum or mild heat. It is to be noted that, when spin coating is utilized, an additional drying period is generally not necessary as the spinning tends to drive off the solvent. The preceramic coating is ceramified by heating to a temperature of between 40 and 1000°C. Generally, for temperatures of between 40°C. and 200°C., the coating is heated in the presence of ozone to form the ceramic coating. For temperatures between 200°C. and 1000°C., the coating may be heated in ozone or air. However, since the method utilizing ozone usually produces a more rapid, complete ceramification, it is generally preferred. It is also contemplated herein that the coatings be heated in the absence of oxygen to form hermetic coatings on substrates prone to oxidation. Any method of heating such as the use of a convection oven or radiant or microwave energy is generally functional herein. The rate of heating, moreover, is also not critical, but it is most practical and preferred to heat as rapidly as possible. In a typical ceramification procedure, the coated substrate may be placed in a convection oven and, if necessary, a continuous flow of ozone introduced. The temperature in the oven is then raised to the desired level (such as 200°C.) and maintained at that level for a desired period of time (such as 0.5 - 8 hours). If ozone is to be utilized in this invention, ozone may be present in any quantity sufficient to enhance ceramification. Generally, concentrations of ozone greater than 0.01 weight percent are effective, with larger quantities producing better results. The ozone used may be generated by any convenient practical means such as simply exposing oxygen to a source of ultraviolet light. The UV light may come from any source capable of emitting a wavelength in the range of from 185 to 200 nm, such as, for example, a quartz-mercury lamp. The oxygen source may simply be an ambient atmosphere, but it has been found that enriched oxygen atmospheres or atmospheres of pure oxygen aid in increasing the rate of ceramification. Alteratively, the ozone may be generated by passing an oxygen source through an ozone generator. Various generators are well known in the art and many are commercially available. The process using an ozone generator is particularly advantageous since a much greater quantity of ozone may be produced. For instance, an ozone generator may produce ozone concentrations of up to 10 weight percent whereas the UV light method is only effective in producing concentrations up to 0.1 weight percent. The mechanism whereby ozone decreases the temperature necessary for ceramification has not been fully elucidated but it is believed that ozone enhances the oxidation of the H-resin and modifying ceramic oxide precursor to form the ceramic or ceramic-like coating. In addition to ozone, water vapour may also be included in the pyrolysis procedure. This inclusion has been shown to further enhance the rate of ozone oxidation. By the above methods, a thin (less than 2 micrometres (microns)) ceramic or ceramic-like planarizing coating is produced on the substrate. The coating smooths the irregular surfaces of various substrates and has excellent adhesive properties. In addition, the coating may be covered by other coatings such as further SiO 2 /modifying ceramic oxide layers, silicon-containing coatings, silicon-carbon-containing coatings, silicon-nitrogen-containing coatings and/or silicon-nitrogen-carbon-containing coatings. In a dual layer system, the second passivation layer may comprise silicon-containing coatings, silicon-carbon-containing coatings, silicon-nitrogen-containing coatings, silicon-carbon-nitrogen-containing coatings or an additional silicon dioxide and modifying ceramic oxide coating. In a triple layer system, the second passivation layer may comprise silicon-carbon-containing coatings, silicon-nitrogen-containing coatings, silicon-carbon-nitrogen-containing coatings or an additional silicon dioxide and modifying ceramic oxide coating, and the third barrier coating may comprise silicon coatings, silicon-carbon-containing coatings, silicon-nitrogen-containing coatings and silicon-carbon-nitrogen-containing coatings. The silicon-containing coating described above is applied by a method selected from (a) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, (b) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, or (c) metal assisted chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof. The silicon-carbon coating is applied by a means selected from (1) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, (2) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes, and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane or (3) plasma-enhanced chemical vapour deposition of a silacyclobutane or disilacyclobutane, as further described in U.S.-A-5,011,706. The silicon-nitrogen-containing coating is deposited by a means selected from (A) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of ammonia, (B) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof in the presence of ammonia, or (C) ceramification of a silicon and nitrogen containing preceramic polymer. The silicon-carbon-nitrogen-containing coating is deposited by a means selected from (i) chemical vapour deposition of hexamethyldisilazane, (ii) plasma-enhanced chemical vapour deposition of hexamethyldisilazane, (iii) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, (iv) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia and (v) ceramification of a preceramic solution comprising a carbon - substituted polysilazane, polysilacyclobutasilazane or polycarbosilane in the presence of ammonia. The silicon dioxide and modifying ceramic oxide coating is applied by the ceramification of a preceramic mixture comprising a silicon dioxide precursor and a modifying ceramic oxide precursor as in the initial coating. Coatings produced by the instant invention possess low defect density and are useful on electronic devices as protective coatings, as corrosion resistant and abrasion resistant coatings, as temperature - and moisture - resistant coatings, as dielectric layers in, for instance, multilayer devices and as a diffusion barrier against ionic impurities such as sodium and chloride. The following non-limiting examples are included so that one skilled in the art may more readily understand the invention. The hydrogen silsesquioxane resin in the following examples was prepared by the method of Collins et al. in U.S. Patent 3,615,272. The platinum catalyst comprised platinum acetylacetonate in toluene (0.1237 % platinum in solution). EXAMPLE 1 0.45 g of hydrogen silsesquioxane resin, 0.092 g of Ta(OCH 2 CH 3 ) 5 and 0.04 g of platinum catalyst (50 ppm platinum based on the amount of H-resin) were dissolved in 3.42 g of n-heptane and 1.0 g n-dodecane by stirring in a flask at room temperature to form a clear, non-gelled solution (10 weight percent solids). The solution was allowed to stand at room temperature for several hours. (FTIR spectra was run on this solution - See Example 6). 5 Motorola 14011B CMOS devices were coated with the above solution and then spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 1.5 hours to provide a clear SiO 2 /Ta 2 O 5 coating approximately 2000 angstroms thick. All of the coated CMOS devices were functional. The above CMOS devices were again coated with the above solution, spun at 3000 rpm for 10 seconds and pyrolyzed at 400°C. for 1.5 hours to form a second SiO 2 /Ta 2 O 5 layer approximately 2000 angstroms thick. The devices were then exposed to continuous salt spray under standard test condition MIL-STD-883C, method 1009.6 and tested in a go-no go test on a Teradyne Analogical Test Instrument J133C. The results are summarized in Table 1. EXAMPLE 2 0.45 g of hydrogen silsesquioxane resin, 0.133 g of VO(OCH 2 CH 2 CH 3 ) 3 and 0.04 g of platinum catalyst (50 ppm Pt based on the amount of H-resin) were dissolved in 3.15 g of n-heptane and 1.0 g n-dodecane by stirring in a flask at room temperature to form a clear, non-gelled solution. (10 weight percent solids). The solution was allowed to stand at room temperature for several hours. (FTIR spectra was run on this solution - See Example 8). 5 Motorola 14011B CMOS devices were coated with the above solution and then spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to provide a clear SiO 2 /V 2 O 5 coating approximately 2000 angstroms thick. All of the coated CMOS devices were functional. The above CMOS devices were again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to form a second SiO 2 /V 2 O 5 layer approximately 1000 angstroms thick. The devices were then exposed to the same salt spray conditions as Example 1 and tested in a go-no go test on a Teradyne Analogical Test Instrument J133C. The results are summarized in Table 1. EXAMPLE 3 0.45 g of hydrogen silsesquioxane resin, 0.12 g of Nb(OCH 2 CH 3 ) 5 and 0.04 g of platinum catalyst (50 ppm Pt based on the amount of H-resin) were dissolved in 3.43 g of n-heptane and 1.0 g n-dodecane by stirring in a flask at room temperature to form a clear, non-gelled solution. (10 weight percent solids). The solution was allowed to stand at room temperature for several hours. (FTIR spectra was run on this solution - See Example 7). 5 Motorola 14011B CMOS devices were coated with the above solution and then spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to provide a clear SiO 2 /Nb 2 O 5 coating approximately 2000 angstroms thick. All of the coated CMOS devices were functional. The above CMOS devices were again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to apply a second SiO 2 /Nb 2 O 5 layer approximately 1000 angstroms thick. The devices were then exposed to the same salt spray conditions as Example 1 and tested in a go-no go test on a Teradyne Analogical Test Instrument J133C. The results are summarized in Table 1. EXAMPLE 4 0.45 g of hydrogen silsesquioxane resin, 0.15 g of B 3 (OCH 3 ) 3 O 3 and 0.04 g of platinum catalyst (50 ppm Pt based on the amount of H-resin) were dissolved in 3.40 g of n-heptane and 1.0 g n-dodecane by stirring in a flask at room temperature to form a clear, non-gelled solution. (10 weight percent solids). The solution was allowed to stand at room temperature for several hours. 5 Motorola 14011B CMOS devices were coated with the above solution and then spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to provide a clear SiO 2 /B 2 O 3 coating approximately 2000 angstroms thick. All of the coated CMOS devices were functional. The above CMOS devices were again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to form a second SiO 2 /B 2 O 3 layer approximately 1000 angstroms thick. The devices were then exposed to the same salt spray conditions as Example 1 and tested in a go-no go test on a Teradyne Analogical Test Instrument J133C. The results are summarized in Table 1. EXAMPLE 5 0.45 g of hydrogen silsesquioxane resin, 0.076 g of P(OCH 2 CH 3 ) 3 O and 0.04 g of platinum catalyst (50 ppm Pt based on the amount of H-resin) were dissolved in 3.57 g of n-heptane and 1.0 g n-dodecane by stirring in a flask at room temperature to form a clear solution. (10 weight percent solids). The solution was allowed to stand at room temperature for several hours. 5 Motorola 14011B CMOS devices were coated with the above solution and then spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to provide a clear SiO 2 /P 2 O 5 coating approximately 2000 angstroms thick. All of the coated CMOS devices were functional. The above CMOS devices were again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 10 seconds. The devices were heated at 400°C. for 3 hours to form a second SiO 2 /P 2 O 5 layer approximately 1000 angstroms thick. The devices were then exposed to the same continuous salt spray as Example 1 and tested in a go-no go test on a Teradyne Analogical Test Instrument J133C. The results are summarized in Table 1. EXAMPLE 6 The solution prepared in Example 1 was coated on a Motorola 14011B CMOS device and a silicon wafer and each spun at 3000 rpm for 11 seconds. FTIR spectra of the coating on the wafer showed strong bands at 870 cm -1 and 2245 cm -1 , indicating the presence of Si-H, and a strong band at 1062 cm -1 , indicating the presence of Si-O bonds. The device and the silicon wafer were heated at 250°C. for 5.5 hours in the presence of ozone and UV light to provide clear SiO 2 /Ta 2 O 5 coatings approximately 2000 angstroms thick. FTIR spectra of the pyrolyzed coating on the silicon wafer showed a broad band at 1062 cm -1 (Si-O) and nearly complete absence of bands for SiH. The above CMOS device was again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 11 seconds. The device was heated at 250°C. for 5.5 hours in the presence of ozone and UV light to form a second SiO 2 /Ta 2 O 5 layer approximately 1000 angstroms thick. The device was tested in a go-no go test on a Teradyne Analogical Test Instrument J133C and passed the test. EXAMPLE 7 The solution prepared in Example 3 was coated on a Motorola 14011B CMOS device and a silicon wafer and each spun at 3000 rpm for 11 seconds. FTIR spectra of this coating on the silicon wafer showed strong bands at 870 cm -1 and 2245 cm -1 , indicating the presence of Si-H, and a strong band at 1062 cm -1 , indicating the presence of Si-O. The device and wafer were heated at 250°C. for 5.5 hours in the presence of ozone and UV light to provide a clear SiO 2 /Nb 2 O 5 coating approximately 2000 angstroms thick. FTIR spectra of the pyrolyzed coating on the silicon wafer showed a broad band at 1062 cm -1 (Si-O) and nearly complete absence of the bands for SiH. The above CMOS device was again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 11 seconds. The device was heated at 250°C. for 5.5 hours in the presence of ozone and UV light to form a second SiO 2 /Nb 2 O 5 layer approximately 1000 angstroms thick. The device was tested in a go-no go test on a Teradyne Analogical Test Instrument J133C and passed the test. EXAMPLE 8 The solution prepared in Example 2 was coated on a Motorola 14011B CMOS device and a silicon wafer and each spun at 3000 rpm for 11 seconds. FTIR spectra of this coating on the silicon wafer showed strong bands at 870 cm -1 and 2245 cm -1 , indicating the presence of Si-H, and a strong band at 1062 cm -1 , indicating the presence of Si-O. The device and the silicon wafer were heated at 250°C. for 5.5 hours in the presence of ozone and UV light to provide a clear SiO 2 /V 2 O 5 coating approximately 2000 angstroms thick. FTIR spectra of the heated coating on the silicon wafer showed a broad band at 1062 cm -1 (Si-O) and nearly complete absence of bands for SiH. The above CMOS device was again coated with the above solution diluted to 5 weight percent solids (in the same solvent used supra ) and spun at 3000 rpm for 11 seconds. The device was heated at 250°C. for 5.5 hours in the presence of ozone and UV light to form a second SiO 2 /V 2 O 5 layer approximately 1000 angstroms thick. The device was tested in a go-no go test on a Teradyne Analogical Test Instrument J133C and passed the test. SALT SPRAY RESISTANCE OF COATED CMOS DEVICES EXAMPLE RESULTS 1 5 of 5 passed 6 hours 4 of 5 passed 8 hours 2 of 5 passed 10 hours 1 of 5 passed 18 hours 2 4 of 5 passed 2 hours 3 of 5 passed 4 hours 2 of 5 passed 10 hours 1 of 5 passed 76 hours 3 4 of 5 passed 4 hours 3 of 5 passed 10 hours 2 of 5 passed 14 hours 1 of 5 passed 16 hours 4 3 of 5 passed 2 hours 5 3 of 5 passed 2 hours 2 of 5 passed 4 hours 1 of 5 passed 44 hours Uncoated Control fails after 5-10 minutes

Claims: A method of forming a ceramic or ceramic-like coating on a substrate comprising: (I) coating said substrate with a solution comprising a solvent, an hydrogen silsesquioxane resin and a modifying ceramic oxide precursor which is a metal or non-metal composition having one or more hydrolysable groups bonded to a metal selected from tantalum, niobium and vanadium or a non-metal selected from boron and phosphorus, said modifying ceramic oxide precursor being selected from tantalum oxide precursors, niobium oxide precursors, vanadium oxide precursors, phosphorus oxide precursors and boron oxide precursors; (II) evaporating said solvent to thereby deposit a preceramic coating on said substrate; and (III) ceramifying said preceramic coating to a ceramic or ceramic-like coating by heating said modifying preceramic coating to a temperature of between 40°C and 1000°C. A method according to claim 1, wherein said solution contains between 0.1 and 35 weight percent solids of hydrogen silsesquioxane resin and modifying ceramic oxide precursor, said solvent is selected from aromatic hydrocarbons, alkanes, ketones, esters and glycol ethers, and said modifying ceramic oxide precursor is present in an amount such that the final ceramic coating contains between 0.1 and 30 weight percent modifying ceramic oxide. A method according to claim 1 or claim 2, wherein a platinum or rhodium catalyst is additionally present in said solution in an amount of between 15 and 200 ppm platinum or rhodium based on the weight of hydrogen silsesquioxane resin in solution. A method according to any of claims 1 to 3, further comprising: (IV) applying a passivating coating to said ceramic or ceramic-like coating, said passivating coating being selected from (i) silicon-containing coatings, (ii) silicon-carbon-containing coatings, (iii) silicon-nitrogen-containing coatings, (iv) silicon-carbon-nitrogen-containing coatings, and (v) an additional silicon dioxide and modifying ceramic oxide coating, wherein said silicon coating is applied onto said ceramic or ceramic-like coating by a means selected from (a) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, (b) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, and (c) metal-assisted chemical vapour deposition of silanes, halosilanes halodisilanes, halopolysilanes and mixtures thereof; wherein said silicon-carbon coating is applied by a means selected from (1) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, (2) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane and (3) plasma-enhanced chemical vapour deposition of a silacyclobutane or disilacyclobutane; wherein said silicone-nitrogen-containing coating is deposited by a means selected from (A) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixture thereof in the presence of ammonia, (B) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of ammonia, and (C) ceramification of a silicon and nitrogen-containing preceramic polymer; wherein said silicon-carbon-nitrogen-containing coating is deposited by a means selected from (i) chemical vapour deposition of hexamethyldisilazane, (ii) plasma-enhanced chemical vapour deposition of hexamethyldisilazane, (iii) chemical vapour deposition of silanes, alkylsilanes,, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, (iv) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, and (v) ceramification of a preceramic solution comprising a carbon-substituted polysilazane, polysilacyclobutasilazane or polycarbosilane, in the presence of ammonia; and wherein said silicon dioxide and modifying ceramic oxide coating is applied by ceramification of a preceramic mixture comprising a silicon dioxide precursor and a modifying ceramic oxide precursor as defined in claim 1, to produce said silicon-containing passivating coating, whereby a dual layer, ceramic or ceramic-like, coating is obtained on said substrate. A method according to any of claims 1 to 3, further comprising: (IV) applying a passivating coating to said ceramic or ceramic-like coating, said passivating coating being selected from (i) silicon-carbon-containing coatings, (ii) silicon-nitrogen-containing coatings, (iii) silicon-carbon-nitrogen-containing coatings, and (iv) an additional silicon dioxide and modifying ceramic oxide coating, wherein said silicon-carbon coating is applied by a means selected from (1) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, (2) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, or (3) plasma-enhanced chemical vapour deposition of a silacyclobutane or disilacyclobutane; wherein said silicon-nitrogen-containing coating is deposited by a means selected from (A) chemical vapour deposition of silanes, halosilanes halodisilanes, halopolysilanes and mixtures thereof in the presence of ammonia, (B) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of ammonia and (C) ceramification of a silicon and nitrogen-containing preceramic polymer; wherein said silicon-carbon-nitrogen-containing coating is deposited by a means selected from (i) chemical vapour deposition of hexamethyldisilazane, (ii) plasma-enhanced chemical vapour deposition of hexamethyldisilazane, (iii) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, (iv) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixture thereof in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, and (v) ceramification of an preceramic solution comprising a carbon-substituted polysilazane, polysilacyclobutasilazane or polycarbosilane, in the presence of ammonia; and wherein said silicon dioxide and modifying ceramic oxide coating is applied by ceramification of a preceramic mixture comprising a silicon dioxide precursor and a modifying ceramic oxide precursor, to produce the passivating coating; and (v) applying an additional silicon-containing barrier coating to said passivating coating, said silicon-containing barrier coating being selected from (i) silicon coatings, (ii) silicon-carbon-containing coatings, (iii) silicon-nitrogen-containing coatings, and (iv) silicon-carbon-nitrogen-containing coatings, wherein said silicon coating is applied onto the passivating coating by a means selected from (a) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, (b) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, and (c) metal-assisted chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof; wherein said silicon-carbon-containing coating is applied by a means selected from (1) chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkysilane, (2) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof in the presence of an alkane of one to six carbon atoms or an alkylsilane and (3) plasma-enhanced chemical vapour deposition of a silacyclobutane or a disilacyclobutane; and wherein the silicon-nitrogen-containing coating is deposited by a means selected from (A) chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof, in the presence of ammonia, (B) plasma-enhanced chemical vapour deposition of silanes, halosilanes, halodisilanes, halopolysilanes, and mixtures thereof, in the presence of ammonia, and (C) ceramification of a silicon and nitrogen-containing preceramic polymer, and wherein said silicon-carbon-nitrogen-containing coating is deposited by a means selected from (i) chemical vapour deposition of hexamethyldisilazane, (ii) plasma-enhanced chemical vapour deposition of hexamethyldisilazane, (iii) chemical vapour deposition of silanes, alkysilanes, halosilanes, halodisilanes, halopolysilanes, and mixtures thereof, in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, (iv) plasma-enhanced chemical vapour deposition of silanes, alkylsilanes, halosilanes, halodisilanes, halopolysilanes and mixtures thereof in the presence of an alkane of one to six carbon atoms or an alkylsilane, and further in the presence of ammonia, and (v) ceramification of a preceramic solution comprising a carbon-substituted polysilazane, a polysilacyclobutasilazane, an organopolysilane, a silsesquioxane or a polycarbosilane, in the presence of ammonia, to produce said silicon-containing barrier coating, whereby a multilayer, ceramic or ceramic-like, coating is obtained on said substrate. A method according to any of claims 1 to 5, wherein said substrate is an electronic device. An homogenous liquid composition for use in forming a ceramic or ceramic-like coating on a substrate said composition comprising a solvent, an hydrogen silsesquioxane resin and a modifying ceramic oxide precursor which is a metal or non-metal composition having one or more hydrolysable groups bonded to a metal selected from tantalum, niobium, vanadium or a non-metal selected from boron and phosphorous, said modifying ceramic oxide precursor being selected from tantalum oxide precursors, niobium oxide precursors, vanadium oxide precursors, phosphorus oxide precursors and boron oxide precursors. A liquid composition according to claim 7, wherein a platinum or rhodium catalyst is additionally present in said solution in an amount of between 15 and 200 ppm of platinum or rhodium based on the weight of hydrogen silsesquioxane resin in solution.

Inventors: HALUSKA LOREN ANDREW, HALUSKA, LOREN ANDREW
Applicants: DOW CORNING, DOW CORNING CORPORATION
Application year: 1991
Main classification: H01L21
IPC codes: H01L21, C04B41, C23C18