Probe placement for laser probing system

A laser probing system for laser probing a device under test having a cell, comprising:

• a laser source;
• an optical system adapted to provide an optic probe at selectable locations of the device under test in response to light from said laser source, receives reflected light from the device under test, and outputs said reflected light;
• a receiver circuit that receives said reflected light from said optical system, and provides a laser probe (LP) waveform in response to said reflected light;
• and
• a combinational logic analysis (CLA) processor that simulates an optical response at a target location of the cell of the device under test to a test pattern and forms a CLA waveform in response;
• and
• a test controller having a first input for receiving said CLA waveform, a second input for receiving said LP waveform, and an output for providing a position signal, wherein said test controller applies said test pattern to the device under test, triggers said receiver circuit to capture said LP waveform, and repositions said optic probe on the device under test closer to said target location according to a degree of fit between said LP waveform and said CLA waveform.

A method of performing an optic probe test, comprising:

• computing a combinational logic analysis (CLA) waveform at a target probe location within a cell of a device under test using a test pattern;
• positioning an optic probe at an initial location in response to an estimated location of the cell;
• applying said test pattern to the cell and obtaining a first laser probe (LP) waveform in response;
• positioning said optic probe at an adjacent location;
• applying said test pattern to the cell and obtaining a second LP waveform in response;
• and
• repositioning said optic probe at a location closer to said target probe location according to a degree of fit of a corresponding LP waveform and said CLA waveform;
• and
• identifying defects based on a comparison of an actual waveform to said CLA waveform at said location closer to said target probe location.