Dual-laser voltage probing of IC's
First Claim
1. A method of probing an integrated circuit device with laser light to acquire samples of a waveform appearing on the device as the device is exercised by a repetitive pattern of test vectors, comprising:
- a. applying a probe-laser pulse 832 to a region of the device at a selected time during each repetition of the pattern of test vectors and detecting energy reflected from the region as the probe-laser pulse is applied, to thereby produce a reflected-light probe sample;
b. applying a reference-laser pulse 842 to said region of the device at a time during each repetition of the pattern of test vectors which is displaced relative to the time at which the probe-laser pulse is applied, and detecting energy reflected from the region as the reference-laser pulse is applied, to thereby produce a reflected-light reference sample;
c. preparing a ratio of the reflected-light probe sample and the reflected-light reference sample for each repetition of the pattern of test vectors to produce a waveform sample having improved signal-to-noise relative to the reflected-light probe sample.
4 Assignments
0 Petitions
Accused Products
Abstract
A probe beam is used to sample the waveform on an IC device under test (DUT) during each cycle of a test pattern applied to the DUT. A reference laser beam is also used to sample the DUT. For each cycle of the test pattern, the reference and probe beams sample the DUT at the same physical location, but at displaced times with respect to each other. Each reference measurement is made at a fixed time relative to the test pattern while the probe measurements are scanned through the test-pattern time portion of interest, in the manner normal to equivalent time sampling, to reconstruct the waveform. For each test cycle, the ratio of these two measurements is taken. The fluctuations of these ratios due to noise is greatly reduced as compared to fluctuations of the probe measurements taken alone. Thus, a smaller number of averages is required to reconstruct the waveform.
-
Citations
30 Claims
-
1. A method of probing an integrated circuit device with laser light to acquire samples of a waveform appearing on the device as the device is exercised by a repetitive pattern of test vectors, comprising:
-
a. applying a probe-laser pulse 832 to a region of the device at a selected time during each repetition of the pattern of test vectors and detecting energy reflected from the region as the probe-laser pulse is applied, to thereby produce a reflected-light probe sample; b. applying a reference-laser pulse 842 to said region of the device at a time during each repetition of the pattern of test vectors which is displaced relative to the time at which the probe-laser pulse is applied, and detecting energy reflected from the region as the reference-laser pulse is applied, to thereby produce a reflected-light reference sample; c. preparing a ratio of the reflected-light probe sample and the reflected-light reference sample for each repetition of the pattern of test vectors to produce a waveform sample having improved signal-to-noise relative to the reflected-light probe sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. Apparatus for probing an integrated circuit device with laser light to acquire samples of a waveform appearing on the device as the device is exercised by a repetitive pattern of test vectors, comprising:
-
a. a laser-optical system 604, 630 for applying a probe-laser pulse 832 to a region of the device at a selected time during each repetition of the pattern of test vectors and for applying a reference-laser pulse 842 to said region of the device at a time during each repetition of the pattern of test vectors which is displaced relative to the time at which the probe-laser pulse is applied; b. a reflected-power detection system 630, 652 for detecting energy reflected from the region as the probe-laser pulse is applied, to thereby produce a reflected-light probe sample, and for detecting energy reflected from the region as the reference-laser pulse is applied, to thereby produce a reflected-light reference sample; c. a processor for preparing a ratio of the reflected-light probe sample and the reflected-light reference sample for each repetition of the pattern of test vectors to produce a waveform sample having improved signal-to-noise relative to the reflected-light probe sample. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
-
Specification