Grazing and normal incidence interferometer having common reference surface

摘要

A system for inspecting specimens such as semiconductor wafers is provided. The system provides scanning of dual-sided specimens using a diffraction grating that widens and passes nth order (n>0) wave fronts to the specimen surface and a reflective surface for each channel of the light beam. Two channels and two reflective surfaces are preferably employed, and the wavefronts are combined using a second diffraction grating and passed to a camera system having a desired aspect ratio. The system preferably comprises a damping arrangement which filters unwanted acoustic and seismic vibration, including an optics arrangement which scans a first portion of the specimen and a translation or rotation arrangement for translating or rotating the specimen to a position where the optics arrangement can scan the remaining portion(s) of the specimen. The system further includes-means for stitching scans together, providing for smaller and less expensive optical elements.

主权项

1. A method for measuring specimen thickness variations in a specimen having at least two sides, the method comprising:
transmitting variable coherence light energy; receiving the variable coherence light energy, forming diffracted light energy, and passing the diffracted light energy toward two sides of said specimen and toward a plurality of reflective surfaces spaced apart from said specimen, the plurality of reflective surfaces comprising a semi-transparent reflective surface transparent through a first side and less than 90 percent reflective on a second side; sensing light energy from the specimen and the plurality of reflective surfaces; and performing an interferometric normal incidence inspection through the semi-transparent reflective surface.