Process for forming thin-film circuit devices

Claim 1

A PROCESS FOR FORMING A THIN-FILM CIRCUIT DEVICE CONTAINING A CIRCUIT ELEMENT AND CONTACTS COMPRISING THE STEPS OF: PROVIDING A LAMINATED STRUCTURE INCLUDING A SUBSTRATE HAVING THEREON A THIN-FILM LAYER OF MATERIAL HAVING ELECTRICAL CHARACTERISTICS CORRESPONDING TO THOSE OF THE INTENDED CIRCUIT ELEMENT, THE THIN-FILM LAYER BEING COVERED BY A FIRST LAYER OF CONDUCTIVE MATERIAL UNTIL THE DESIRED BOUNDS OF THE CIRCUIT ELEMENT AND CONTACTS HAVE BEEN FORMED, AND THE FIRST LAYER BEING COVERED BY A SECOND LAYER OF CONDUCTIVE MATERIAL; APPLYING A FIRST LAYER OF A PHOTORESIST OVER SAID SECOND LAYER; FORMING AN IMAGE ON SAID FIRST LAYER OF PHOTORESIST WHICH DEFINES PREDETERMINED DIMENSIONS BETWEEN INTENDED CONTACTS; DEVELOPING SAID FIRST LAYER OF PHOTORESIST TO FORM AN APERTURE THEREIN; SELECTIVELY ETCHING A RECTANGULAR CAVITY THROUGH SAID SECOND LAYER TO EXPOSE A SURFACE OF SAID FIRST LAYER, THE DIMENSION BETWEEN A FIRST PAIR OF OPPOSITE SIDE WALLS OF SAID CAVITY BEING THE SAME AS THE DIMENSION BETWEEN THE INTENDED CONTACTS FOR SAID CIRCUIT DEVICE, AND THE DIMENSION BETWEEN A SECOND PAIR OF OPPOSITE SIDE WALLS OF SAID CAVITY BEING GREATER THAN THE DIMENSIONAL WIDTH OF THE CIRCUIT ELEMENT; REMOVNG REMAINING PORTIONS OF SAID LAYER OF PHOTORESIST; APPLYING A SECOND LAYER OF PHOTORESIST OVER EXPOSED PORTIONS OF SAID FIRST AND SECOND LAYERS OF CONDUCTIVE MATERIAL; FORMING AN IMAGE ON SAID SECOND LAYER OF PHOTORESIST WHICH DEFINES THE DESIRED BOUNDS OF THE CIRCUIT DEVICE; DEVELOPING SAID SECOND LAYER OF PHOTORESIST, SAID DEVELOPED SECOND LAYER HAVING A DIMENSIONAL WIDTH LESS THAN SAID DIMENSION BETWEEN SAID SECOND PAIR OF OPPOSITE SIDE WALLS AND EQUAL TO THE DIMENSIONAL WIDTH OF THE CIRCUIT ELEMENT; SUBSEQUENTLY SELECTIVELY ETCHING PORTIONS OF SAID FIRST, SECOND AND THIN-FILM LAYERS WITH FIRST, SECOND AND THIRD ETCHANTS RESPECTIVELY TO LEAVE PORTIONS OF SAID FIRST, SECOND AND THIN-FILM LAYERS COINCIDENT WITH THE CONFIGURATION OF THE DESIRED BOUNDS OF THE CIRCUIT DEVICE, EACH SAID LAYER BEING ATTACKED BY ONLY ITS RESPECTIVE ETCHANT, THE REMAINING PORTIONS OF SAID SECOND LAYER FORMING A PLURALITY OF INDIVIDUAL CONTACTS; REMOVING REMAINING PORTIONS OF SAID SECOND LAYER OF PHOTORESIST; AND SUBSEQUENTLY SELECTIVELY ETCHING THE EXPOSED SURFACE OF SAID FIRST LAYER TO EXPOSE A SURFACE OF SAID THIN-FILM LAYER BETWEEN CONTACTS FORMED OF THE REMAINING PORTIONS OF SAID CONDUCTIVE LAYER.