Abstract: A method for measuring a structure that contains overlying and underlying films in a region where the overlying film's thickness rapidly decreases until the underlying film is exposed (e.g., an edge-exclusion structure). The method includes the steps of: (1) exciting acoustic modes in a first portion of the region with at least one excitation laser beam; (2) detecting the acoustic modes with a probe laser beam that is either reflected or diffracted to generate a signal beam; (3) analyzing the signal beam to determine a property of the structure (e.g., the thickness of the overlying layer) in the first portion of the region; (4) translating the structure or the excitation and probe laser beams; and (5) repeating the exciting, detecting, and analyzing steps to determine a property of the structure in a second portion of the region.

Abstract: The invention provides an apparatus for measuring a property of a sample (using, e.g., ISTS) that includes: 1) an excitation laser that generates an excitation laser beam; 2) an optical system aligned along an optical axis that separates the excitation laser beam into at least three sub-beams; 3) an imaging system aligned along the optical axis that collects the sub-beams and focuses them onto the sample to form an optical interference pattern that generates a time-dependent response in the sample; 4) a probe laser that generates a probe laser beam that diffracts off the time-dependent response to form a signal beam; 5) a detector that detects the signal beam and in response generates a radiation-induced electronic response; and 6) a processor that processes the radiation-induced electronic response to determine the property of the sample.