A method and system for inspecting a surface of a semiconductor workpiece comprises providing a surface inspection system and using the surface inspection apparatus to cause laser light to impinge upon a test location on the workpiece surface and thereby cause the laser light to emerge from the surface as returned light comprising at least one of reflected light and scatter light; collecting the returned light and generating a signal from the returned and collected light, the signal comprising a signal value representative of a characteristic of the workpiece surface at the test location; providing a plurality of threshold candidates and causing the surface inspection system to select a threshold from among the plurality of threshold candidates; comparing the threshold to the signal value to obtain a difference value; using the difference value to assess the characteristic of the workpiece surface at the test location; and using the surface inspection system to automatically cause the method to be repeated for a plurality of test locations on the workpiece surface.