Patent GB-1083522-A (GB)
Title: Boron nitride thin film device and process for making same
IPC: H01G4/06
Filed: 1964-12-11
Abstract: A film of boron nitride is deposited on a substrate by first forming an interlayer on the substrate which will chemically bond to the substrate and to boron nitride, and then depositing boron nitride on the interlayer.  The substrate may be a refractory metal, e.g. Me, W, Nb, Ta, alloys thereof, ferrous alloys, or carbon or silicon, or another metal such as copper or a copper alloy if a layer of one of the above metals is formed thereon prior to forming the interlayer. The interlayer preferably has elements common to the substrate and boron nitride, e.g. the metal boride or nitride, but may also be e.g. an oxide.  Suitably the substrate, degreased, is held in a chamber evacuated to less than 1 micron of mercury, boron trichloride is introduced to a pressure of 5 to 500 microns and the substrate heated at 700 to 1700 DEG C. for 15 to 60 secs.  The chamber is again evacuated to less than 1 micron, filled with b -trichloroborazole to a pressure of 10 to 20 mm. and heated at 700 to 1700 DEG C. for 1 to 5 minutes to form a layer of boron nitride 0.2 to 5 microns thick. The source of boron nitride may alternatively be a mixture of boron trichloride and ammonia.  The boron nitride film may be used as insulation for a conductor, a voltage protection device, as a protective layer in equipment used for handling molten glass and metals and as a capacitor dielectric. In the latter case metal electrodes are applied to the boron nitride film by conventional methods, e.g. deposition of aluminium or gold from the vapour phase.ALSO:A film of boron nitride is deposited on a substrate by first forming an interlayer on the substrate which will chemically bond to the substrate and to boron nitride, and then depositing boron nitride on the interlayer.  The substrate may be a refractory metal, e.g. Mo, W, Nb, Ta, alloys thereof, ferrous alloys, or carbon or silicon, or another metal such as copper or a copper alloy if a layer of one of the above metals is formed thereon prior to forming the interlayer.  The interlayer preferably has elements common to the substrate and boron nitride, e.g. the metal boride or nitride, but may also be, e.g. an oxide.  Suitably the substrate, degreased, is held in a chamber evacuated to less than 1 micron of mercury, boron trichloride is introduced to a pressure of 5 to 500 microns and the substrate heated at 700 DEG  to 1700 DEG  C. for 15 to 60 secs.  The chamber is again evacuated to less than 1 micron, filled with b -trichloroborazole to a pressure of 10 to 20 mm. and heated at 700 DEG  to 1700 DEG  C. for 1 to 5 minutes to form a layer of boron nitride 0.2 to 5 microns thick.  The source of boron nitride may alternatively be a mixture of boron trichloride and ammonia.  The boron nitride film may be used as insulation for a conductor, a voltage protection device, as a protective layer in equipment used for handling molten glass and metals and as a capacitor dielectric. In the latter case metal electrodes are applied to the boron nitride film by conventional methods, e.g. deposition of aluminium or gold from the vapour phase.