On the Rapid Thermal Sintering of Thin Amorphous Si-Metal-Si Structures
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MENACHEM NATAN Martin Marietta Laboratories,
1450 S. Rolling Road,
Baltimore, MD 21227
ABSTRACT The development of rapid thermal annealing (RTA) or sintering (RTS) techniques for processing of Si and compound semiconductor metallizations also opens a new avenue for investigations of the initial stages of high-temperature, solid state reactions in thin Of particular interest in this regard are the nucleation and early amorphous multilayers. growth of silicides. In this study we suggest a method to prepare large numbers of specimens for TEM, using deposition of Si/metal/Si trilayers on electron microscope grids and annealing the grids in an RTA system. The method enables quick determination of first silicide phases, nuclei shape and density, relative nucleation and growth rates and, for some systems, the Seven widely used metals are investigated: Co, Cr, Nb, Ni, MN, Ti, and diffusing species. Ta. The first silicide phases determined from electron diffraction patterns are listed and TEM cross sections of compared to first phases reported in longer furnace annealings. reacted Si/Ta/Si and Si/Nb/Si show two different growth morphologies, which are discussed in terms of main diffusing species in a proposed model. INTRODUCTION The recent development of rapid thermal processing technologies, of which rapid thermal annealing (RTA) and sintering (RTS) are subsets, has been driven mainly by the requirements of electronic materials processing. These technologies are essential in process steps where thermal energy is needed for a solid state reaction of two or more components, such as in silicide formation, while unwanted side effects, such as dopant diffusion in the Si substrate, must be minimized. RTA and RTS appear to be extremely valuable complementary tools in basic materials research for the following reason: they can provide very short timetemperature cycles, in which both parameters are accurately known and controllable. This allows "freezing" of solid state reactions in thin films or bulk materials in their early stages under well-defined conditions. As a result, heretofore difficult-to-obtain data on nucleation and early growth of new phases will become easily available. With a fast annealing/sintering cycle, data collection and analysis become the ratelimiting step in "matrix" experiments which require large numbers of specimens, e.g., construction of phase diagrams, and studies of nucleation and growth kinetics and of microstructures at various reaction stages. One of the most versatile techniques for these types uf stuadio, particularly in thin fili, is tranjission nIwctruh uicroscopy (T6.i), in which generally the slowest step is specimen preparation. In the first part of this paper we report on a new method of studying the early stages of solid state reactions between two or more thin films with TEM, using specimens prepared by multilayer deposition on electron microscope grids followed by RTA. We demonstrate the value of this approach by reporting on the nucleation and early growth of sulicides in seven Si/me
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