The application of TiSi2 as a dopant diffusion source for boron and arsenic was studied. The TiSi2 layers were formed by the usual salicide process and doped by ion implantation. Diffusion was carried out by various furnace and rapid thermal processing steps. Using secondary ion mass spectrometry, scanning electron microscopy, and x-ray diffraction, clear evidence for compound formation between Ti and the two dopant species is found. This leads to low dopant concentrations at the silicide/silicon interface, very poor efficiency of the diffusion source, and unacceptably high contact resistivities.

The influence of patterned oxide layers on temperature non-uniformity during RTP is studied. It is shown that large temperature non-uniformities (up to 80 °C) can occur during RTP as a consequence of large scale patterns of thick oxides. The dependence of oxide thickness and pattern geometry on temperature non-uniformity over a wafer is studied. A set of simulation programs is developed to calculate the optical characteristics of a wafer inside a chamber and to calculate the time dependent temperature non-uniformities on patterned wafers. The calculated results agree very well with the experimental results. The simulation program was used to define the optimal optical conditions for RTP systems for minimal temperature non-uniformity due to patterned overlayers on Si.

Rksumk. L'interaction dans le systkme poly-Si sur TiSi2 sur un substrat de Si et dans le systkme polycide avec CoSi2 ainsi qu'avec TiSi2 est analys6e quand ils sont sournis ?i une temperature 6levQ dans un four classique. On dkmontrera que le premier systkme souffre d'instabilitt? due ?i la croissance epitaxiale dans la phase solide qui peut seulement Stre &it& paniellement par le dopage de la couche poly-Si. Le systsme polycide montre une couche de TiSi2 qui est devenue rude et qui pourrait poser des problkmes pour des couches poly-Si initiellement plus minces que 450 nm. Dans le cas de CoSi2, la dkgradation est d6sastreuse: le metal Co peut Ctre detect6 partout dans la couche poly-Si, ce qui est ?i peine kvitable m8me par un dopage du CoSi2 avec As ou B.

A mathematical evaluation is presented for the beam raster scanning mode of depth profiling with SIMS, combined with electronic gating of the detection system. A computer program was developed in which a former treatment of the influence of the crater edges is extended to arbitrary impurity profiles and which also accounts for neutral particles in the primary beam. It is shown that these neutrals have a dramatic effect on the obtained dynamic range and that the commonly used background subtraction technique does not necessarily lead to the correct profile. The simulation including neutrals shows good agreement with an experimentally measured profile. Finally, the influence of the crater edges and the choice of an appropriate structure for measuring depth resolution and outdiffusion are discussed.

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For the first time an operating heterojunction bipolar silicon transistor has been realized with phosphorous doped amorphous silicon (a-Si) emitter. The deposition of a-Si is a relatively simple technique. The current gain (β) of 14 at a base Gummel Number (G.N.) of 1.35 1013 s/cm4 is higher than that obtained with normal diffused emitter bipolar transistors with the same G.N. for the base. This adds a degree of freedom to the design of bipolar structures according to the compromise between base resistance and current gainCrucial points that have to be looked at further are interface recombination at the a-Si/c-Si transition and emitter resistance.

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