Method and apparatus for determining drift depth of impurities in semiconductors

Claim 1

IN APPARATUS FOR DETERMINING THE OPTIMUM TIME FOR TERMINATING A LITHIUM DRIFTING PROCESS IN THE MANUFACTURE OF A SEMICONDUCTOR OF THE TYPE HAVING A POSITIVE REGION AND A NEGATIVE REGION, THE COMBINATION COMPRISING A FIRST ELECTRODE DISPOSED ON A SURFACE OF SAID POSITIVE REGION, AN ANNULAR SECOND ELECTRODE DISPOSED ON THE SURFACE OF SAID POSITIVE REGION AND ENCIRCLING SAID FIRST ELECTRODE, SAID FIRST ELECTRODE AND SAID SECOND ELECTRODE BEING SEPARATED BY A GAP, MEANS TO APPLY A REVERSE NEGATIVE VOLTAGE BIAS BETWEEN SAID NEGATIVE REGION AND SAID SECOND ELECTRODE, MEANS TO HEAT SAID SEMI-CONDUCTOR WHEREBY UPON APPLICATION OF SAID BIAS AND HEAT, LITHIUM DRIFTING IS EFFECTED, A RESISTANCE MEASURING INSTRUMENT CONNECTED FROM SAID FIRST ELECTRODE TO SAID SECOND ELECTRODE, A CONTROL CIRCUIT CONNECTED TO THE OUTPUT OF SAID INSTRUMENT AND PROVIDING AN OUTPUT SIGNAL IN RESPONSE TO A PREDETERMINED HIGH RESISTANCE MEASUREMENT BY SAID INSTRUMENT, MEANS OPERATIVELY COUPLED TO SAID CONTROL CIRCUIT TO CUT OFF OPERATION OF SAID MEANS TO HEAT IN RESPONSE TO SAID OUTPUT SIGNAL FROM SAID CONTROL CIRCUIT, THEREBY TERMINATING SAID DRIFTING AND WHEREBY A LITHIUM DRIFTED REGION IS FORMED WITHIN A PREDETERMINED ZONE BETWEEN SAID NEGATIVE REGION AND SAID SURFACE.