| 摘要 |
A timing calibration system for a wafer level integrated circuit (IC) tester is disclosed. The tester includes a set of probes for contacting pads on a surface of an IC and having a plurality of tester channels. Each channel generates a TEST signal at a tip of a corresponding probe in response to a periodic CLOCK signal with a delay adjusted by drive calibration data supplied as input to the tester channel. The TEST signal produced by each channel includes edges occurring in a timing pattern controlled by programming data provided as input to each tester channel. To calibrate test signal timing of all channels, each channel is programmed to generate a test signal having the same repetitive edge timing pattern at the tester channel's corresponding probe tip. The test signal produced at each probe tip is then cross-correlated to a periodic reference signal having the same repetitive edge timing pattern. The drive calibration data of each channel is then iteratively adjusted to determine a value which maximizes the cross-correlation between its output test signal and the reference signal. To maximize the accuracy of the timing calibration, each repetition of the test and reference signal edge pattern provides pseudo-randomly distributed time intervals between successive signal edges. |
