Apparatus and method for determining the surface profile of a semiconductor substrate using a laser scanning technique

A metrology tool for determining a surface profile of a substrate, the metrology tool comprising:

• a wafer mount configured to support the substrate;
• at least one movable stage coupled to move the wafer mount in at least one direction;
• an optical system comprising a plurality of components, which remain stationary at fixed positions while the at least one movable stage moves the wafer mount and the substrate supported thereon in the at least one direction, wherein plurality of components comprises:
• a beamsplitter coupled to redirect a coherent light beam onto a surface of the substrate, wherein as the wafer mount moves in the at least one direction, the coherent light beam redirected by the beamsplitter is reflected from the surface of the substrate at each of a plurality of measurement points and transmitted back through the beamsplitter as reflected light;
• a lens coupled to receive the reflected light transmitted through the beamsplitter, wherein as the wafer mount moves in the at least one direction, the reflected light from each of the plurality of measurement points is transmitted through the lens:
• (a) without redirection if a slope of the surface of the substrate is zero at a given measurement point, and (b) with redirection if the slope of the surface of the substrate is not zero at the given measurement point;
• and
• an optical sensor coupled to receive the reflected light transmitted through the lens, wherein as the wafer mount moves in the at least one direction, the optical sensor detects a position of the reflected light from each of the plurality of measurement points incident on the optical sensor, and generates a plurality of output data corresponding to the detected positions of the reflected light;
• and
• a processing device coupled to receive the plurality of output data from the optical system, wherein the processing device executes program instructions stored in non-transitory memory to:
• convert the plurality of output data into a plurality of slope data points, each corresponding to a slope of the surface of the substrate at a different measurement point on the surface of the substrate;
• and
• combine the plurality of slope data points to determine a surface profile of the substrate.