5 LAYER STACK OF NITRIDE, OXIDE, AND AMORPHOUS-SILICON ON GLASS, ANALYZED WITH SPECTROSCOPIC ELLIPSOMETRY

A stack of nitride/oxide/amorphous Si/oxide/nitride on a glass substra te was fabricated and subsequently analyzed with spectroscopic ellipso metry. The oxides and nitrides were deposited by plasma-enhanced chemi cal-vapor-deposition and the amorphous Si was deposited with sputter d eposition. The optical constants of these materials depend on depositi on conditions and hence handbook values cannot be used. The optical co nstants of the amorphous Si layer are modeled as a combination of Lore ntz oscillators. A further complication is that the amorphous Si layer is opaque over about half of the spectral range. Drawbacks of the str aight-forward analysis method are discussed and an enhanced analysis m ethod is described and the results presented. The enhanced method impr oves the uncertainty in the thickness determination of two of the laye rs by an order of magnitude. (C) 1997 American Vacuum Society.