Microwave Activation of Dopants & Solid Phase Epitaxy in Silicon
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0989-A06-18
Microwave Activation of Dopants & Solid Phase Epitaxy in Silicon D. C. Thompson1, J. Decker1, T. L. Alford1, J. W. Mayer1, and N. David Theodore2 1 School of Materials, Arizona State University, Tempe, AZ, 85287 2 Wireless & Packaging Systems Lab., Freescale Semiconductor Inc., Tempe, AZ, 85284 ABSTRACT Microwave heating is used to activate solid phase epitaxial re-growth of amorphous silicon layers on single crystal silicon substrates. Layers of single crystal silicon were made amorphous through ion implantation with varying doses of boron or arsenic. Microwave processing occurred inside a 2.45 GHz, 1300 W cavity applicator microwave system for timedurations of 1-120 minutes. Sample temperatures were monitored using optical pyrometery. Rutherford backscattering spectrometry, and cross-sectional transmission electron microscopy were used to monitor crystalline quality in as-implanted and annealed samples. Sheet resistance readings show dopant activation occurring in both boron and arsenic implanted samples. In samples with large doses of arsenic, the defects resulting from vacancies and/or micro cluster precipitates are seen in transmission electron micrographs. Materials properties are used to explain microwave heating of silicon and demonstrate that the damage created in the implantation process serves to enhance microwave absorption. INTRODUCTION Microwave heating has been presented as a viable alternative to other high temperature processing methods used to repair the damage inherent in ion implant processing [1-4]. The most common methods of repairing implant damage in silicon processing, lamp and laser rapid thermal processing (RTP), may result in uneven heating of the near surface device layers due to emissivity differences between device layers [2, 5]. Uneven heating results in vertical and lateral dopant diffusion, which degrades device performance [6]. Further complications with lamp and laser heating can arise because the depth of the heated region is determined by the depth of absorbed photons, 1 µm or less in silicon, resulting in conduction losses and higher power input needs [1]. Microwave heating of silicon allows for more even heating of a near surface volume due to the penetration depth associated with microwave processing. This volumetric heating may result in less power use and less dopant diffusion. Microwave heating has already found utility by activating solid state reactions in silicon [7, 8]. For this work microwave processing was used to study the effects of microwave heating on highly damaged layers of ion implanted silicon. EXPERIMENTAL To fabricate the samples used in this work Czochralski (CZ) grown, 100 mm, P-type boron doped, 50-60 Ω cm (100) orientated silicon wafers were cleaned and placed in an NV10180 batch ion implanter. Samples for monitoring implant damage and boron activation were implanted with 33 keV B+ ions, to doses ranging 1x1014 ñ 5x1015 B+ cm-2, at room temperature. Samples used to monitor implant damage and arsenic activation were implanted with 180 keV As
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