Alignment of an ellipsometer or other optical instrument using a diffraction grating
AssigneeBell Communications Research, Inc.
InventorWilliam E. Quinn
Life of this patent
Estimating the term…
Abstract
Alignment method and procedure for accurately determining the off-normal angle of incidence of an optical beam with a sample, for example, in ellipsometry. A diffraction grating is fabricated with a grating period chosen such that, when a laser beam irradiates the grating placed at the sample area, a beam is diffracted generally along the incoming laser beam. The laser is then angularly moved with respect to the grating until the two beams are auto-collimated, i.e., made coincident. The angle of incidence is then accurately determined from the laser wavelength and the grating period through well known equations.
Claims9
A method of aligning an optical instrument, comprising the steps of:
- irradiating along a first axis a diffraction grating having a grating period of d with an incident beam of light having a wavelength .lambda., thereby diffracting along a second axis at least an n-th order diffracted beam from said grating, n being an integer greater than zero;
- and
- auto-collimating said n-th order diffracted beam with said incident beam, wherein said first and second axis are made to be substantially coincident, whereby an angular orientation between said incident beam and said grating is established, thereby determining an angle of incidence between said incident beam and said grating at said established orientation.
An ellipsometer system, comprising:
- an ellipsometer including an ellipsometric light source for irradiating a sample area with an optical beam at an angle of incidence .phi..sub.i ;
- and
- a diffraction grating having a grating period d disposed at said sample area, wherein ##EQU4## wherein n is a positive integer and .lambda. is a wavelength of light emitted by a narrow-bandwidth light source physically substitutable for said light source in said ellipsometer.
Dependencies are inferred from the claim text.