Nonlinear optical characterization of the surface of silicon wafers: In-situ detection of external stress J. Reif a, *, R. Schmid b , Th Schneider a , D. Wolramm a a Lehrstuhl Experimentalphysik II, Brandenburgische Technische Universita¨t Cottbus, D-03044, Cottbus, Germany b Lehrstuhl Physikalische Chemie und Analytik, Brandenburgische Technische Universita¨t Cottbus, D-03044, Cottbus, Germany Abstract The potential of nonlinear optical techniques for a rapid on-line and non-destructive inspection and characterization of silicon wafers is discussed. As an example, the in-situ detection of external stress on the wafer is reported, resulting from specific mounting conditions. As an outlook, the problem of radially non-uniform growth of the silicon crystal when utilizing the Czochralski-growth method is addressed. A simple technique is proposed to discriminate those sections of the wafer which are ready for use in further applications from those which are not useable for proper device fabrication, thus enabling the selection of appropriate material from as-grown crystals. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Optical characterization of semiconductor surface; Nonlinear optics at surfaces; In-situ detection of external stress; Czo- chralski-grown silicon 1. Introduction As a consequence of ever-increasing integration of semiconductor devices, an increase at the same pace is observed of the requirements of quality of the sub- strate wafer, the gate oxide layers, and the metallic contacts. Most desirable are methods for preselecting appropriate substrates as well as on-line growth-moni- toring and non-destructive characterization of sub- sequent layers. This is a genuine field for optical techniques, which are per se non-destructive and in- situ-applicable wherever light has access. A typical problem, encountered in this context, is the observation that Czochralski-grown silicon wafers are not uniform across their diameter [1]. This shows up, in particular, by the quality of gate oxide grown on this type of wafers. Two concentric regions are found with markedly dierent breakdown stability of the oxide. These regions, the width of which depends on the growth speed, are separated by a small ring, several millimeters wide, where practically no useable oxide can be grown at all (for more details see Refs. in [1]). Up to the present, several methods have been developed [1,2] to analyze this situation, all of which lack, however, the problem that the analyzed wafer is no longer usable for device fabrication. An accepted explanation for the dierent oxidation behavior of the three zones postulates dierent compo- sition during growth [1]. According to this picture, the inner zone consists of vacancy-rich silicon crystal, the outer one is oversaturated interstitial-rich. In the separ- Solid-State Electronics 44 (2000) 809–813 0038-1101/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S0038-1101(99)00277-4 * Corresponding author. Tel.: +49-355-69-3185; fax: +49- 355-69-3985. E-mail address: reif@tu-cottbus.de (J. Reif).