Probing surface chemical processes during epitaxial semiconductor crystal growth at near-atmospheric pressures using photon-based techniques

Abstract

It is demonstrated here that for the study of epitaxial semiconductor crystal growth from vapour-phase precursors, photon-based methods may be applied under true 'in situ' conditions and can, where appropriate, reveal a great deal regarding the nature of the growing surface. While several techniques exist which may probe the gaseous phase, the study of the surface phase under conditions of high pressures (up to 1000 mbar) and high temperatures (up to 1000 K) is far from trivial. This paper sets out to emphasise recent developments in technique which permit the study of the surface phase during epitaxial crystal growth. Data are presented for several semiconductor/ substrate systems obtained using the linear technique of reflectance anisotropy and the non-linear technique of optical second-harmonic generation (SHG). In particular, the technique of reflectance anisotropy is shown to be a very powerful probe of surface stoichiometry, real-time monitoring of layer-bylayer growth processes, adsorption and desorption kinetics and also the detection of surface reconstructions that occur under high vacuum and nearatmospheric pressure conditions. For the SHG technique it is shown that the application of this method to centroasymmetric substrates such as GaAs is not trivial, yet under certain conditions surface SHG responses can be observed which are directly related to the structure of the surface layers. While the data presented are for special epitaxial semiconductor systems, throughout the paper emphasis is placed upon the applicability of the experimental approach towards the study of crystal growth systems in general.

NESSPIOM—Network for enhanced semiconductor surface processing through in situ optical monitoring

“…One of the first was generated by the Salford group then at UMIST via a fortuitous choice of experimental conditions subsequently shown to correspond to a particular condition. 30,31 In terms of the NESSPIOM group activities, Taylor at Imperial has made a study of the SHG response from an Si(001) surface during growth of Si from disilane and has observed growth oscillations that correspond to each successive layer. 32,33 It has to be said that the aim of this work is to study the fundamentals of the nonlinear surface response and not to develop a surface monitor.…”

In Situ Characterization of Epitaxy

“…A comprehensive review of linear and nonlinear light-sample interactions in relation to in situ diagnostic techniques has been written by Pemble et al [3]. A comprehensive review of linear and nonlinear light-sample interactions in relation to in situ diagnostic techniques has been written by Pemble et al [3].…”

“…As stated earlier, RAS is highly surface sensitive because it works on the basis of the symmetry reduction associated with surface reconstruction works and, for cubic materials, the bulk isotropic linear contributions cancel [3]. The sampled size is typically in the square millimeter range, and measurements can be modulated at the output using a piezoelastic modulator, or at the input using an electrooptic modulator.…”