Thickness analysis of silicon membranes for stencil masks

Authors

E. Sossna, University of Kassel
R. Kassing, University of Kassel
I. W. Rangelow, University of Kassel
C. M. Herzinger, J. A. Wollam Company
T. E. Tiwald, J. A. Wollam Company
John A. Woollam, J. A. Wollam CompanyFollow
Th. Wagner, LOT–Oriel GmbH & Company KG, Im Tiefen See 58, 64293 Darmstadt, Germany

Date of this Version

11-1-2000

Comments

Published in J. Vac. Sci. Technol. B 18„(6), Nov-Dec 2000. ©2000 American Vacuum Society. Used by permission.

Abstract

Stencil masks are key to charged particle projection lithography, in particular for ion projection lithography. To fulfill pattern printing requirements in the sub-70 nm regime, excellent thickness uniformity and thermal emissivity control are critical parameters for high quality stencil mask fabrication. We propose and demonstrate a technique based on infrared variable angle spectroscopic ellipsometry (IR-VASE) to measure these parameters with adequate accuracy and precision. The refractive index of the Si membrane was evaluated using a Sellmeier dispersion model combined with a Drude model. Because of its spectral range from 2 to 33 μm, the IR-VASE method is sensitive to the thickness of layers as well as to the concentration and profile of Si membrane doping.