Patent ID: 6931336

Claim:
A method of detecting an integrated circuit in failure among integrated circuits, based on spectrum which is a result of analyzing a frequency of a current running through an integrated circuit when a test signal is applied to said integrated circuit, without preparing data of an integrated circuit in no failure, as a reference, said method comprising the steps of: (a) testing integrated circuits to find an integrated circuit in no failure; (b) measuring spectrum of a current supplied from a power source into said integrated circuit; (c) judging said integrated circuit to be in failure; (d) repeating said steps (a) to (c) until spectrum is measured for N integrated circuits wherein N is a predetermined integer; (e) calculating a mean value and standard deviation for each frequencies with respect to said spectrum of said N integrated circuits; (f) judging whether said spectrum is abnormal or not, based on said mean value and said standard deviation; (g) deleting data of spectrum having been judged abnormal in said step (f), and repeating said steps (a) to (f); (h) defining said mean value and said standard deviation as a reference; (i) testing integrated circuits to find an integrated circuit in no failure; (j) measuring spectrum of a current supplied from a power source into said integrated circuit; (k) judging whether said spectrum is abnormal or not, based on said reference, and judging an integrated circuit to be either in no failure if said spectrum is abnormal or in failure if said spectrum is not abnormal; (l) carrying out said steps (i) to (j) for integrated circuits not tested yet; (m) defining integrated circuits having been judged to be in failure as integrated circuits not tested yet; and (n) repeating said steps (i) to (l).