Advances in multichannel spectroscopic ellipsometry

Since the development and perfection of automatic ellipsometers, an effort that began nearly three decades ago, spectroscopic ellipsometry (SE) has increased in popularity as a non-destructive tool for characterizing the optical properties and layered structure of bulk solids and thin films. With the more recent development of multichannel ellipsometers for high-speed spectral scanning, in situ real-time SE has emerged as a very powerful tool for characterizing the time evolution of the optical properties and layered structure of materials during preparation and processing. High-speed spectral scanning has also opened up the possibility of real-time monitoring and control for complex material systems that cannot be fully characterized using well-established real-time measurements at one (or a few) wavelength(s). In this review, we will first describe the most recent developments in multichannel, multiparameter SE, in which spectroscopic information is obtained in addition to the ellipsometric parameters (psi,Delta). Then we will discuss recent applications of multichannel SE to amorphous semiconductor film growth in order to obtain material properties in complex multilayer and graded-layer device structures. Ln general in this review, the focus will he on recent examples of the characterization of complex optical systems of technological interest. Practical situations will be described in which the dielectric functions of films are deposition-dependent and evolve with thickness due to particle and grain size effects and intentional compositional gradients, and in which film growth occurs on rough surfaces, leading to optical models for film growth that require interface and surface roughness layers. (C) 1995 Elsevier Science S.A.