Microstructural Evolution and Defects in Ultra-thin SIMOX Materials during Annealing
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Microstructural Evolution and Defects in Ultra-thin SIMOX Materials during Annealing Jun Sik Jeoung, Rachel Evans and Supapan Seraphin Department of Materials Science and Engineering, The University of Arizona, Tucson, AZ 85721, U.S.A. ABSTRACT The microstructure of ultra-thin SIMOX depends strongly on implantation dose, energy and annealing conditions. We used TEM combined with AES and RBS to determine the microstructural evolution of SIMOX wafers subjected to various temperatures during annealing. We found that an optimum dose window to produce a continuous buried oxide layer without Si islands is 3.0-3.5×1017 O+/cm2 for 100 keV. The thickness of the silicon overlayer and BOX layer produced in this dose window was about 170 nm and 75 nm respectively. RBS analysis showed that a high quality crystalline Si layer was produced after annealing at 1350 oC for 4 hrs. The defect density was very low (< 300/cm2) for all samples implanted at 100 keV.
1. INTRODUCTION Silicon-on-insulator (SOI) has become a significant technology for high density integrated circuits. For the fully depleted MOSFET devices operating at low-power low-voltage, SOI wafers must have a very thin silicon film and requires a tight thickness uniformity [1-2]. A lowdose low-energy separation by implanted oxygen (SIMOX) is one of the most promising technologies for making an ultra-thin SOI structure. This technology permits a direct formation of an ultra-thin Si active layer with a thin buried oxide (BOX) layer without sacrificial oxidation to achieve the thin film SOI. The low-dose low-energy implantation reduces processing cost and time, thus increasing throughput, and produces fewer defects in the Si active layer. A number of investigations have demonstrated the feasibility to fabricate a very thin SIMOX structure by using low doses [3-5]. However, the correlation between the microstructure and the processing parameters is not well established. In this work, a set of SIMOX wafers fabricated at different doses and energies were characterized using transmission electron microscopy (TEM), Auger electron spectroscopy (AES), and Rutherford backscattering spectrometry (RBS) in order to understand the correlation between implantation dose and energy and the formation of SIMOX structure.
2. EXPERIMENTAL DETAILS The SIMOX wafers were prepared using the Ibis 1000 high-current oxygen implanter. Oxygen ion doses of 2.5, 3.0, 3.5, 4.5, 6.0 and 8.0×1017 O+/cm2 were implanted into p-type Si wafers at 100 keV. In order to study the effect of implantation energy on the microstructure of SIMOX, oxygen ion doses of 2.0 and 4.5×1017 O+/cm2 were also implanted at 65 keV. The wafer temperature during implantation was approximately 560 oC and beam current was about 40 mA. The implanted wafers were transferred to an annealing furnace and were B1.2.1 Downloaded from https://www.cambridge.org/core. YBP Library Services, on 20 Aug 2018 at 16:50:44, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-716-B
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