Apparatus for locating and testing areas of interest on a workpiece

A method of testing areas of interest on a workpiece where the areas of interest have an optical reflectivity different from all other areas on the workpiece and where the location of the areas of interest are unknown, said method comprising the steps of:

• scanning the surface of the workpiece with a pair of search beams in a manner such that said search beams are reflected, with each search beam having a different wavelength;
• measuring the power of each of the reflected search beams as they are scanned;
• processing the measured power of the reflected search beams to identify the location of areas of interest;
• storing the locations of the identified areas of interest;
• and
• selecting at least one of those identified areas for testing.

An apparatus for testing areas of interest on a workpiece where the areas of interest have an optical reflectivity different from all other areas on the workpiece and where the location of the areas of interest are unknown, said apparatus comprising:

• means for generating a first search beam of radiation, said first search beam having a first wavelength;
• means for generating a second search beam of radiation, said second search beam having a second wavelength different from said first wavelength;
• means for scanning said search beams over the surface of the workpiece such that they are reflected;
• means for measuring the power of the reflected search beams;
• processor means for identifying an area of interest on the workpiece based on the measured power of the reflected search beams;
• and
• means for testing the workpiece at the identified area of interest.

A method of evaluating surface conditions within the unmasked areas on a masked semiconductor wafer comprising the steps of:

• scanning the surface of the wafer with first and second search beams of radiation in a manner such that the beams are reflected, with each said beam having a different wavelength;
• measuring the power of the reflected search beams as they are scanned;
• processing the measured power of the reflected search beams to identify the location of unmasked areas on the wafer;
• periodically exciting the surface of the wafer within an identified unmasked area;
• directing said first beam of radiation within the region that is being periodically excited such that the first beam is reflected;
• and
• measuring the periodic reflected power of the first beam induced by the periodic excitation of the wafer to evaluate the surface conditions within the unmasked area.

An apparatus for evaluating surface conditions within the unmasked areas on a masked semiconductor wafer comprising:

• means for generating a pump beam of radiation having a first wavelength;
• means for intensity modulating the pump beam;
• means for generating a probe beam of radiation having a wavelength different from the pump beam;
• means for scanning said beams with respect to said wafer such that they are reflected;
• means for measuring the power of the reflected radiation beams;
• and
• processor means for controlling the operation of said beam generating means, modulating means, scanning means and measuring means, with both of said radiation beams being used as search beams that are scanned over the surface of the wafer, with the reflected power of the search beams being used to identify the location of unmasked areas on the wafer, and with selected ones of said identified areas being evaluated by intensity modulating and directing said pump beam onto an unmasked area and directing the probe beam into the region within that unmasked area that is being periodically excited by the pump beam, with the periodic changes in power of the reflected probe beam induced by the intensity modulated pump beam being used to evaluate the surface conditions on the wafer.