Apparatus for and method of net trace prior level subtraction

A method comprising:

• performing connectivity tests of integrated circuit structures at a selected level of a die using design analysis tools, the design analysis tools filtering out via locations that will not show a voltage contrast signal if a defect exists;
• identifying potential defect locations in the die indicating via locations susceptible to systematic failure, the potential defect locations being via locations that are not filtered out;
• translating the potential defect locations to via locations for a prior level of the die that are on the same net as the vias at the selected level using a net trace tool, the prior level being below the selected level;
• after translating the potential defect locations, performing an electron beam voltage contrast comparison inspection for defects on each via location for the selected level of the die and the prior level of the die, the electron beam voltage contrast comparison inspection identifying locations of defects in vias;
• translating the locations of the defects for the prior level to the via locations for the selected level using the net trace tool, wherein defects for the prior level are translated in the opposite direction for the selected level;
• and
• subtracting the location of the translated defects for the prior level from the location of the defects for the selected level.

A method of detecting defects in levels of a die for an integrated circuit structure, the method comprising:

• identifying potential defect locations in a selected inspection level of a die, the potential defect locations being susceptible to systematic failure;
• performing connectivity tests at the susceptible locations in the die by applying voltages to the selected level of the die;
• identifying error locations from the connectivity tests;
• translating the error locations to matching locations in a level below the selected inspection level;
• after translating the error locations, performing a first inspection at the level below the selected inspection level using a net trace tool, the first inspection identifying defects comprising via opens or via shorts;
• processing the die up to the selected inspection level;
• performing an inspection on the via locations on the selected inspection level;
• translating the defects for the level below the selected inspection level to via locations for the selected inspection level, wherein defects for the level below the selected inspection level are translated in the opposite direction using the net trace tool;
• and
• subtracting the defects for the level below the selected inspection level from the defects for the selected inspection level.