Fabrication of semiconductor controlled rectifiers

Claim 1

A METHOD FOR THE FABRICATION OF SEMICONDUCTOR CONTROLLED RECTIFIERS COMPRISING THE STEPS OF: OBTAINING A SEMICONDUCTIVE SUBSTRATE OF A FIRST TYPE OF SEMICONDUCTIVITY; DIFFUSING A FIRST IMPURITY CAPABLE OF IMPARTING A SECOND TYPE OF SEMICONDUCTIVELT TO FORM A FIRST DIFFUSED LAYER OF SAID SECOND TYPE OF SEMICONDUCTIVITY ON SAID SUBSTRATE, SAID FIRST DIFFUSED LAYER FORMIN G A P-N JUNCTION WITH SAID JUNCTION HAVING A SHALLOW IMPURITY CONCENTRATION GRADIENT; DIFFUSING A SECOND IMPURITY CAPABLE OF IMPARTING SAID SECOND TYPE OF SEMICONDUCTIVITY INTO SAID FIRST DIFFUSED LAYER TO FORM OF SECOND DIFFUSED LAYER HAVING A HIGHER SURFACE CONCENTRATION THAN THAT OF SAID FIRST DIFFUSED LAYER; SAID FIRST AND SECOND IMPURITIES BEING DIFFUSED IN SEPARATE DIFFUSION OPERATIONS; AND SAID SECOND IMPURITY PENETRATING TO LESS THAN THE DEPTH PENETRATION OF SAID FIRST IMPURITY; FORMING A REGION OF SAID FIRST TYPE OF SEMICONDUCTIVITY IN SAID SECOND DIFFUSED LAYER; FORMING OHMIC CONTACTS ON SAID REGION OF FIRST TYPE OF SEMICONDUCTIVITY, AND ON BOTH MAJOR SURFACES OF SAID SECOND DIFFUSED LAYER; AND DIVIDING SAID FIRST AND SECOND DIFFUSED LAYERS INTO TWO DISTINCT PORTIONS, A FIRST PORTION HAVING SAID REGION OF FIRST TYPE SEMICONDUCTIVITY AND A FIRST OF SAID OHMIC CONTACTS THEREON AND A SECOND PORTION HAVING A SECOND OF SAID OHMIC CONTACTS THEREON.