The pitch calibration by a single wavelength laser and Littrow configuration laser diffractometer was presented. The calibration system consists of a green He-Ne laser, a precision angular positioning state, a four-quadrant detector, a beam splitter, and some optics. The measurement principles was based on the Littrow configuation that the reflective diffraction beam coincides with the incident beam. The pitch value was determined by the diffraction angle α and laser wavelength λ. A pitch standard, with nominal value of 292 nm, was measured by a wavelength of 543 nm green He-Ne laser diffractometer. The average pitch value was 292.10 nm. According to the "Guide to the expression of uncertainty in measurement", the system uncertainty was evaluated. The error sources included laser wavelength, refractive index of air, angular state, temperature, and coefficient of thermal expansion. The expanded uncertainty was 0.03 nm at a confidence level of 95% and 15 degrees of freedom. The main contributor of uncertainy was the positioning deviation of angular stage. Although the laser diffractometer had a high-accuracy ability, the measurement capability of Laser diffractometer was limited by the laser wavelength. The pitch p should be large than a half of laser wavelength.

Date Published: 20 November 2003
PDF: 9 pages
Proc. SPIE 5190, Recent Developments in Traceable Dimensional Measurements II, (20 November 2003); doi: 10.1117/12.505559

Published in SPIE Proceedings Vol. 5190:
Recent Developments in Traceable Dimensional Measurements II
Jennifer E. Decker; Nicholas Brown, Editor(s)