Semiconductor wafer surface inspection apparatus and method

A surface inspection system for determining the presence of particles on the surface of a workpiece, the surface having smooth and patterned regions, the system comprising:

• means for scanning said surface in a sequence of paired line scans, each pair of line scans including a first scan and a second scan identical to said first scan;
• a surface sensor operatively coupled to said scanning means for distinguishing between features of the surface;
• a particle sensor operatively coupled to said scanning means for detecting the presence of a particle resting on the surface;
• and
• activating means operating concurrently with said scanning means for receiving data of features of the surface from said scanning means and said surface sensor during said first scan in each pair of line scans, said activating means activating said particle sensor during said second scan in each pair of line scans to be responsive to the presence of a particle located on a flat smooth region of the surface, said activating means deactivating said particle sensor in the absence of a flat smooth region of the workpiece surface.

A method of inspecting a surface of a workpiece to determine the presence of particles thereon, the method comprising the steps of:

• advancing the workpiece in a first direction;
• optically scanning a surface of the workpiece in a second direction transverse to a said first direction, said optical scanning employing a beam directed perpendicular to the surface of the workpiece;
• obtaining gross surface data in the form of locations of undulations and flat portions of the surface of the workpiece;
• repeating a scan of the workpiece surface to cover the same region covered by the first scan of the workpiece surface;
• obtaining particle data by light reflected from a particle on the workpiece surface at locations of flat portions of the surface obtained from the gross data;
• and
• continuing with the advance of the wafer in the first direction and the scanning in the second direction to obtain further data of the surface of the workpiece.