Method of applying silicone passivants to etch moats in mesa device wafers

Claim 1

A method of simultaneously selectively applying a silicone elastomer passivant lining to a plurality of etch moats in a major surface of a silicon semiconductor wafer, said method comprising the steps of: applying a liquid blanket coating of uncured silicone elastomer passivant to a major surface of a silicon semiconductor wafer having a plurality of etch moats therein to which said silicone elastomer passivant will adhesively bond upon partial curing; placing on said silicone elastomer passivant blanket coating a flexible, porous sheet to which said silicone elastomer passivant will adhesively bond upon partial curing; partially curing the entirety of said silicone elastomer passivant blanket coating to produce cohesive strength in said coating and adhesive bonds between said coating and each of said sheet and said etch moats, said adhesive bonds having a strength greater than said cohesive strength; pulling said sheet and an adherent blanket layer of partially cured passivant away from said wafer surface to remove said partially cured coating as a continuous blanket, while leaving portions of said blanket interfacing with said wafer surface as a continuous coating of partially cured silicone elastomer passivant completely lining each of said etch moats; and thereafter, completing the cure of said lining of partially cured silicone elastomer passivant left within said etch moats.

Claim 2

A method of simultaneously selectively applying a silicone elastomer passivant lining to a plurality of etch moats in a major surface of a silicon semiconductor wafer, said method comprising the steps of: applying a liquid blanket coating of uncured silicone elastomer passivant to a major surface of a silicon semiconductor wafer having a plurality of etch moats therein to which said silicone elastomer passivant will adhesively bond upon partial curing; placing on said silicone elastomer passivant blanket coating a flexible, porous sheet to which said silicone elastomer passivant will adhesively bond upon partial curing; partially curing the entirety of said silicone elastomer passivant blanket coating to produce cohesive strength in said coating and adhesive bonds between said coating and each of said sheet and said etch moats, said adhesive bonds having a strength greater than said cohesive strength; pulling said sheet and an adherent blanket layer of partially cured passivant away from said wafer surface to remove said partially cured coating as a continuous blanket, while leaving portions of said blanket interfacing with said wafer surface as a continuous coating of partially cured silicone elastomer passivant completely lining each of said etch moats; and thereafter, completing the cure of said lining of partially cured silicone elastomer passivant left within said etch moats.

Claim 3

A METHOD OF APPLYING A SILICONE ELASTOMER PASSIVANT LINING TO A MAJOR SURFACE OF A SILICON SEMICONDUCTOR WAFER HAVING A PLURALITY OF DISCRETE DEVICES INCLUDED THEREIN IN WHICH EACH OF SAID DEVICES HAS AN EMITTER MESA UPSTANDING ON SAID MAJOR SURFACE, SAID METHOD COMPRISING THE STEPS OF: COATING SAID MAJOR SURFACE WITH A MASKING LAYER THAT DEFINES A PLURALITY OF ANNULAR AREAS CIRCUMSCRIBING EACH MESA EMITTER; ETCHING SAID AREAS IN SAID WAFER MAJOR SURFACE TO PRODUCE ETCH MOATS THAT EXTEND DOWN THROUGH A COLLECTOR-BASE PN JUNCTION; APPLYING A LIQUID BLANKET COATING OF UNCURED SILICONE ELASTOMER PASSIVANT TO SAID ETCH MOATS AND SAID MASKING LAYER WHEREIN THE SILICONE ELASTOMER PASSIVANT WILL ADHESIVELY BOND TO SAID ETCH MOATS UPON PARTIAL CURE; PLACING ON SAID SILICONE ELASTOMER PASSIVANT BLANKET COATING A LAYER OF FABRIC TO WHICH SAID SILICONE ELASTOMER PASSIVANT WILL ADHESIVELY BOND UPON PARTIAL CURING, WHEREIN SAID FABRIC LAYER COMPLETELY OVERLIES SAID WAFER; HEATING TO PARTICLLY CURE THE ENTIRETY OF SAID SILICONE ELASTOMER PASSIVANT BLANKET COATING TO PRODUCE COHESIVE STRENGTH IN SAID COATING BUT SO THAT THE COATING HAS A GREATER ADHERENCE TO SAID ETCH MOATS AND SAID FABRIC LAYER THAN COHESIVE STRENGTH; PULLING SAID FABRIC LAYER AND AN ADHERENT BLANKET LAYER OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT AWAY FROM SAID WAFER SURFACE TO REMOVE SAID PARTIALLY CURED COATING AS A CONTINUOUS BLANKET, WHILE LEAVING PORTIONS OF SAID BLANKET INTERFACING WITH SAID WAFER SURFACE AS A CONTINUOUS COATING OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT COMPLETELY LINING EACH OF SAID ETCH MOATS; AND THEREAFTER, HEATING TO COMPLETELY CURE SAID LINING OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT LEFT WITHIN SAID ETCH MOATS.

Claim 4

A METHOD OF APPLYING A SILICONE ELASTOMER PASSIVANT LINING TO A MAJOR SURFACE OF A SILICON SEMICONDUCTOR WAFER HAVING A PLURALITY OF DISCRETE DEVICES INCLUDED THEREIN IN WHICH EACH OF SAID DEVICES HAS AN EMITTER MESA UPSTANDING ON SAID MAJOR SURFACE, SAID METHOD COMPRISING THE STEPS OF: COATING SAID MAJOR SURFACE WITH A MASKING LAYER THAT DEFINES A PLURALITY OF ANNULAR AREAS CIRCUMSCRIBING EACH MESA EMITTER; ETCHING SAID AREAS IN SAID WAFER MAJOR SURFACE TO PRODUCE ETCH MOATS THAT EXTEND DOWN THROUGH A COLLECTOR-BASE PN JUNCTION; APPLYING A LIQUID BLANKET COATING OF UNCURED SILICONE ELASTOMER PASSIVANT TO SAID ETCH MOATS AND SAID MASKING LAYER WHEREIN THE SILICONE ELASTOMER PASSIVANT WILL ADHESIVELY BOND TO SAID ETCH MOATS UPON PARTIAL CURE; PLACING ON SAID SILICONE ELASTOMER PASSIVANT BLANKET COATING A LAYER OF FABRIC TO WHICH SAID SILICONE ELASTOMER PASSIVANT WILL ADHESIVELY BOND UPON PARTIAL CURING, WHEREIN SAID FABRIC LAYER COMPLETELY OVERLIES SAID WAFER; HEATING TO PARTICLLY CURE THE ENTIRETY OF SAID SILICONE ELASTOMER PASSIVANT BLANKET COATING TO PRODUCE COHESIVE STRENGTH IN SAID COATING BUT SO THAT THE COATING HAS A GREATER ADHERENCE TO SAID ETCH MOATS AND SAID FABRIC LAYER THAN COHESIVE STRENGTH; PULLING SAID FABRIC LAYER AND AN ADHERENT BLANKET LAYER OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT AWAY FROM SAID WAFER SURFACE TO REMOVE SAID PARTIALLY CURED COATING AS A CONTINUOUS BLANKET, WHILE LEAVING PORTIONS OF SAID BLANKET INTERFACING WITH SAID WAFER SURFACE AS A CONTINUOUS COATING OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT COMPLETELY LINING EACH OF SAID ETCH MOATS; AND THEREAFTER, HEATING TO COMPLETELY CURE SAID LINING OF PARTIALLY CURED SILICONE ELASTOMER PASSIVANT LEFT WITHIN SAID ETCH MOATS.

Claim 5

A method of simultaneously applying a silicone elastomer passivant lining to etch moats in a major surface of a plurality of silicon semiconductor wafers, said semiconductor wafers having a plurality of discrete devices included therein in which each of said devices has an emitter mesa upstanding on said major surface and an etch moat circumscribing each emitter mesa, said method comprising the steps of: juxtaposing a plurality of silicon semiconductor wafers on a generally flat support so that a surface opposite said major surface containing said etch moats is contiguous said support; applying a liquid blanket coating of uncured silicone elastomer passivant to said major surfaces of said wafers wherein said passivant will adhesively bond to said etch moats upon partial curing; placing on said blanket coating of passivant a silk cloth to which said passivant will adhesively bond upon partial cure, whereby said cloth completely overlies sAid wafers; partially curing the entirety of said passivant blanket coating to produce cohesive strength in said passivant coating but so that the passivant coating has a greater adherence to said etch moats and said silk cloth than cohesive strength; pulling said silk cloth and an adherent blanket layer of partially cured silicone elastomer passivant away from said plurality of wafer surfaces to remove said partially cured passivant coating as a continuous blanket, while leaving portions of said blanket interfacing with said wafer surfaces as a continuous coating of partially cured silicone elastomer passivant completely lining each of said etch moats; and thereafter, completing the cure of said lining of partially cured silicone elastomer passivant left within said etch moats.

Claim 6

A method of simultaneously applying a silicone elastomer passivant lining to etch moats in a major surface of a plurality of silicon semiconductor wafers, said semiconductor wafers having a plurality of discrete devices included therein in which each of said devices has an emitter mesa upstanding on said major surface and an etch moat circumscribing each emitter mesa, said method comprising the steps of: juxtaposing a plurality of silicon semiconductor wafers on a generally flat support so that a surface opposite said major surface containing said etch moats is contiguous said support; applying a liquid blanket coating of uncured silicone elastomer passivant to said major surfaces of said wafers wherein said passivant will adhesively bond to said etch moats upon partial curing; placing on said blanket coating of passivant a silk cloth to which said passivant will adhesively bond upon partial cure, whereby said cloth completely overlies sAid wafers; partially curing the entirety of said passivant blanket coating to produce cohesive strength in said passivant coating but so that the passivant coating has a greater adherence to said etch moats and said silk cloth than cohesive strength; pulling said silk cloth and an adherent blanket layer of partially cured silicone elastomer passivant away from said plurality of wafer surfaces to remove said partially cured passivant coating as a continuous blanket, while leaving portions of said blanket interfacing with said wafer surfaces as a continuous coating of partially cured silicone elastomer passivant completely lining each of said etch moats; and thereafter, completing the cure of said lining of partially cured silicone elastomer passivant left within said etch moats.