Share Email Print
cover

Proceedings Paper

New algorithm for the measurement of pitch in metrology instruments
Author(s): Nien-Fan Zhang; Michael T. Postek; Robert D. Larrabee; Leon Carroll; William J. Keery
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

Traditionally, the measurement of pitch in metrology instruments is thought to be a benign self-compensating function. However, as the measurement uncertainty of metrology instruments is pushed to the nanometer level, evaluation of the performance of the pitch measurement algorithms becomes increasingly important. Such an evaluation was done during the development of the documentation required by NIST for the issuance of the new scanning electron microscope magnification calibration standard SRM 2090. In the course of this evaluation, a new algorithm for the measurement of pitch was developed. This algorithm, although currently applied to the data from the scanning electron microscope, also can be utilized for other types of metrology instrumentation. Traditionally, for a pitch measurement, a line is fitted to each edge of the data independently. Then the distance between some arbitrary threshold value on each of those lines is determined. The new algorithm eliminates the concern for the selection of a threshold. Two data sets are defined -- one for each of the two edges used for the pitch measurement. Then regression lines are fitted to both sets of data simultaneously with the constraint that parallelism is maintained between these lines. In this way, the data sets are always evaluated in pairs. The evaluation of uncertainty for this measurement process has also been made. Comparisons with simulated data show that the mean square and variance of the pitch distance from the new algorithm is smaller than that from the traditional one. The development of the algorithm as well as the analysis of NIST laser interferometer measurements are presented and illustrated with data obtained from SRM 2090 prototypes.

Paper Details

Date Published: 21 May 1996
PDF: 12 pages
Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); doi: 10.1117/12.240079
Show Author Affiliations
Nien-Fan Zhang, National Institute of Standards and Technology (United States)
Michael T. Postek, National Institute of Standards and Technology (United States)
Robert D. Larrabee, National Institute of Standards and Technology (United States)
Leon Carroll, National Institute of Standards and Technology (United States)
William J. Keery, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 2725:
Metrology, Inspection, and Process Control for Microlithography X
Susan K. Jones, Editor(s)

© SPIE. Terms of Use
Back to Top