Double-pulsed optical interferometer for waveform probing of integrated circuits
First Claim
1. 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.
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Accused Products
Abstract
Optical interferometery is used to probe an integrated circuit device under test (DUT). During each cycle of a repetitive electrical test pattern applied to the DUT a reference pulse is provided at a fixed time relative to the test pattern, and a probe pulse is provided at a time scanned through the test pattern in the manner of equivalent time sampling. The probe and reference light pulses are each split to provide at least a second probe pulse and a second reference pulse. One probe pulse and one reference pulse interact with the DUT at the same physical location, but at displaced times with respect to each other. The second probe pulse and the second reference pulse travel an optical delay path with length controlled to compensate for motions of the DUT. The probe pulses are recombined and detected to provide a probe interference signal. The reference pulses are recombined and detected to provide a reference interference signal. For each cycle, electrical activity in the DUT is detected by preparing a ratio of the probe interference signal and the reference interference signal.
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Citations
37 Claims
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1. A method of detecting activity in a semiconductor device as a repetitive electrical test pattern is applied to the device, comprising the acts of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An apparatus for detecting activity in a semiconductor device as a repetitive electrical test pattern is applied to the device, comprising:
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a source of a first probe light pulse, thereby outputting a first probe light pulse at a selected time during each repetition of the electrical test pattern;
a source of a first reference light pulse, thereby outputting a first reference light pulse at a time displaced relative to the selected time at which the first probe light pulse is provided;
a splitter onto which the first probe light pulse and first reference light pulse are incident, whereby at least a second probe light pulse and a second reference light pulse are provided;
a support for the semiconductor device onto which the first probe light pulse and first reference light pulse are incident;
a beam combiner, located to combine the first probe light pulse and the second probe light pulse, and to combine the first reference light pulse and the second reference light pulse, after the first probe light pulse and the first reference light pulse interact with the semiconductor device;
a detector located to detect the first probe light pulse and the second probe light pulse, thereby to output a probe interference signal and to detect the first reference light pulse and the second reference light pulse, thereby to output a reference interference signal; and
a processor coupled to the detector, thereby to determine a function of the probe interference signal and the reference interference signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification