Semiconductor devices having a bottom electrode silver soldered to a case member

Claim 1

A SEMICONDUCTOR DEVICE COMPRISED OF (1) A FIRST ELECTRODE, SAID FIRST ELECTRODE BEING COMPRISED OF A METAL SELECTED FROM THE GROUP CONSISTING OF TANTALUM, TUNGSTEN, MOLYBDENUM AND BASE ALLOYS THEREOF, (2) A SEMICONDUCTOR WAFER HAVING A P-N JUNCTION AND HAVING ONE SURFACE BONDED TO THE ELECTRODE, (3) A LAYER OF A FIRST SOLDER FUSIBLE ABOVE 375*C. DISPOSED BETWEEN THE ELECTRODE AND THE WAFER AND BONDING THEM TO EACH OTHER, (4) A SECOND ELECTRODE BONDED TO THE OTHER SURFACE OF THE SEMICONDUCTOR WAFER, SAID SECOND ELECTRODE BEING OF AN AREA APPROXIMATELY AS GREAT AS THAT OF THE WAFER AND COMPRISED OF A METAL SELECTED FROM THE GROUP CONSISTING OF TANTALUM, MOLYBDENU, TUNGSTEN, AND BSE ALLOYS THEREOF, (5) A SECOND SOLDER DISPOSED BETWEEN THE SAID OTHER SURFACE OF THE WAFER AND THE SECOND ELECTRODE AND BONDING THE WFER TO THE SECOND ELECTRODE, SAID SECOND SOLDER BEING COMPRISED OF AT LEAST ONE METAL FROM THE GROUP CONSISTING OF GOLD, SILVER AND COPPER AND MINOR PORPORTIONS OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF LEAD, PHOSPHORUS, ARSENIC, ANTIMONY, TIN, SILICON AND GERMANIUM, SAID SOLDER HAVING A MELTING POINT ABOVE 375*C., (6) A SUPPORT MEMBER OF LARGER AREA THAN THE SECOND ELECTRODE HAVING A WELL THEREIN AND COMPRISED OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF COPPER, COPPER BASE ALLOYS, STEEL AND FERROUS BASE ALLOYS THEREOF, AND (7) A THIRD LAYER OF SOLDER DISPOSED BETWEEN THE SECOND ELECTRODE AND THE UPPER SURFACE OF THE WELL OF THE SUPPORT MEMBER, SAID THIRD SOLDER HAVING A MELTING POINT ABOVE 375*C. AND COMPRISED OF A MAJOR PORTION OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF SILVER, GOLD AND COPPER AND BASE ALLOYS THEREOF.