Patent ID: 6496261
Filing Date: 2002-12-17
Classification: G01R

Abstract:
A method of detecting activity in a semiconductor device as a repetitive electrical test pattern is applied to the device, comprising the acts of:providing a first probe light pulse at a selected time during each repetition of the test pattern and dividing the first probe light pulse to provide at least a second probe light pulse; providing a first reference light pulse at a time during each repetition of the test pattern displaced relative to the selected time at which the first probe light pulse is provided and dividing the first reference light pulse to provide at least a second reference light pulse; directing the first probe light pulse and the first reference light pulse onto the semiconductor device; combining the first probe light pulse with the second probe light pulse and the first reference light pulse with the second reference light pulse, after the first probe light pulse and the first reference light pulse interact with the semiconductor device, such that the first probe light pulse and the second probe light pulse overlap in space and time and the first reference light pulse and the second reference light pulse overlap in space and time; detecting the overlapped probe light pulses thereby to provide a probe interference signal; detecting the overlapped reference light pulses thereby to provide a reference interference signal; and determining a function of the probe interference signal and the reference interference signal.