Patent ID: 7436527

Claim:
An apparatus for measuring a parameter of a sample, comprising: a radiation source for generating a probe beam; an optical element having a numerical aperture of at least 0.5 for focusing said probe beam onto the surface of the sample such that various rays within the focused probe beam create a spread of angles of incidence with respect to said sample; an immersion fluid between the optical element and the sample for increasing the spread of angles of incidence; a detector receiving the probe beam after the probe beam has been reflected from the sample, said detector measuring the intensity of various rays as a function of position within the reflected probe beam, with the position of the rays within said reflected probe beam corresponding to specific angles of incidence with respect to said sample; and a processor for determining a parameter of the sample based on the intensity measurements, said parameter being selected from the group consisting of material composition, thickness, index of refraction, absorption, stress, feature width, critical dimension, profile dimension, and surface roughness.