Patent ID: 8749784

Claim:
A method for detecting ultra-fine features of an integrated circuit on a semiconductor substrate, comprising: positioning an optical focus system in vicinity of a first planar surface of a semiconductor substrate, wherein the semiconductor substrate comprises an integrated circuit (IC) fabricated by 22 nanometer or smaller scale semiconductor micro-fabrication process, wherein the IC includes circuit features parallel to a circuit horizontal direction or a circuit vertical direction, wherein the circuit horizontal direction and the circuit vertical direction are substantially parallel to the first planar surface; inputting an oscillating signal into the integrated circuit; focusing a first incident light by the optical focus system to produce a first focused light spot on a portion of the integrated circuit in the semiconductor substrate, wherein the first incident light is linearly polarized in a first linear polarization substantially parallel to the circuit horizontal direction; detecting, by a photo detector, a first reflected light reflected from the portion of the integrated circuit in the semiconductor substrate; obtaining a first waveform from the first reflected light detected from the portion of the integrated circuit in the semiconductor substrate; rotating the first linear polarization of the first incident light by a polarization rotator to produce a second incident light having a second linear polarization substantially parallel to the circuit vertical direction; focusing the second incident light by the optical focus system to produce a second focused light spot on the portion of the integrated circuit in the semiconductor substrate; detecting, by the photo detector, a second reflected light reflected from the portion of the integrated circuit in the semiconductor substrate; and obtaining a second waveform from the second reflected light detected from the portion of the integrated circuit in the semiconductor substrate.