Patent GB-1115458-A (GB)
Title: Process for making thin film circuit devices
IPC: G03F7/40
Filed: 1965-11-15
Abstract: <PICT:1115458/C6-C7/1> An electrically insulating layer is formed between two conductors by forming a first conductor on a substrate, covering the substrate and first conductor with a polymer coating except for predetermined exposed portions of the first conductor, bombarding the polymer coating with ionized particles to convert the polymer coating to a higher order polymer to provide a permanent insulating layer over the substrate and the covered portions of the first conductor, and forming a second conductor over the insulating layer and the exposed portions of the first conductor. The bombardment also operates to clean the exposed portions of the first conductor.  In the embodiment of the invention, cryogenic circuits are made by depositing a film of tin over a substrate 26 (Fig. 1), which may be a glass sheet, by a vacuum deposition process in vacuum chamber 12 which includes a chimney 28 containing a vessel of the metal to be deposited on the substrate and means for heating and vaporizing the metal.  The substrate 26 is then removed from the vacuum system and the tin film coated with a photo-resist which is exposed to U. V. light in pre-selected areas and developed to remove all areas of the photo-resist except where the tin film is to remain to form the tin gate strips 34 and 44 Fig. 2, (not shown).  The unprotected tin is removed by etchant and the photo-resist film preferably stripped from the substrate.  An insulating film 40 is formed over the entire substrate by applying an additional coat of the photo-resist which is dried under infrared.  Windows are then formed in the photo-resist film.  The substrate is placed in vacuum chamber 12 which is then evacuated and filled to 10-3 to 10-2 millimeters pressure with argon or other inert gases such as hydrogen, steam.  An A. C. voltage of 5000 to 15000 volts is then applied to spaced electrode 22 and adjusted until the dark portion of the glow created by the voltage envelopes the substrate 26.  Chamber 12 is evacuated and a metal film is deposited over the substrate, the metal atoms also passing through the windows in the insulating film 40.  The substrate is then removed from the chamber and portions of the second deposited film selectively removed by the photo-resist and etch techniques to produce the conductors 36, 38, 42, 46 and 49. The lead conductors such as 36, 38, 42, 46, 48 may be deposited first and then the tin strips deposited.  The photo-resist material are light-sensitive organic polymers and may be of the 'positive' or 'negative' type. The 'positive' photo-resists can be patterned after irradiation by protecting predetermined areas from irradiation with patterned metal films. 'Negative' resists are selectively removed in areas which are not exposed to U. V. light by developing.ALSO:An electrically insulating layer is formed between two conductors by forming a first conductor on a substrate, covering the substrate and first conductor with a polymer coating except for predetermined exposed portions of the first conductor, bombarding the polymer coating with ionized particles to convert the polymer coating to a higher order polymer to provide a permanent insulating layer over the substrate and the covered portions of the first conductor, and forming a second conductor over the insulating layer and the exposed portions of the first conductor.  The bombardment also operates to clean the exposed portions of the first conductor.  In the embodiment of the invention, yorogenic circuits are made by depositing a film of tin over a substrate 26 (Fig. 1), which may be a glass sheet, by a vacuum deposition process in vacuum chamber 12 which includes a chimney 28 containing a vessel of the metal to be deposited on the substrate and means for heating and vapourizing the metal. The substrate 26 is then moved from the vacuum system and the tin film coated with a photo-resist which is exposed to U.V. light in preselected areas and developed to remove all areas of the photo-resist except where the tin film is to remain to form the p tin gate strips 34 and 44 (Figure 2, not shown).  The unprotected tin is removed by etchant and the photo-resist film is preferably stripped from the substrate.  An insulating film 40 is formed over the entire substrate by applying an additional coat of the photo-resist which is dried under infra-red.  Windows are then formed in the photo-resist film.  The substrate is placed in vacuum chamber 12 which is then evacuated and filled to 10-3 to 10-2 millimeters pressure with argon or other inert gasses such as hydrogen, steam. An A.C. voltage of 5000 to 15000 volts is then applied to spaced electrode 22 and adjusted until the dark portion of the glow created by the voltage envelopes the substrate 26.  Chamber 12 is evacuated and a metal film is deposited over the substrate, the metal atoms also passing through the windows in the insulating film 40.  The substrate is then removed from the chamber and portions of the second deposited film selectively removed by the photo-resist and etch techniques to produce the conductors 36, 38, 42, 46 and 49.  The lead conductors such as 36, 38, 42, 46, 48 may be deposited first and then the tin strips deposited.  The photo-resist material are light-sensitive organic polymers and may be of the "positive" or "negative" type.  The "positive" photo-resists can be patterned after irradiation by protecting pre-determined areas from irradiation with patterned metal films.  "Negative" resists are selectively removed in areas which are not exposed to U.V. light by developing.  To measure the dielectric properties of the insulating film parallel plate capacitors are made using the insulating film as the dielectric by spinning the liquid photo-resist solutions on to a thin metallic film deposited on a substrate to form one of the capacitor plates, exposure to infra-red to drive out the solvents, subjecting the photo-resist film irradiation by organ ions using the glow discharge process, forming a second metallic film over the insulating layer which is subsequently patterned by photo-resist and etch techniques to form the second parallel capacitor plate The photo resist solution may be doped with silicon oils to improve the mechanical strength, or a fine powder of quartz crystals or barium titinate to improve the dielectric properties.