The Influence of Low Temperature Pre-Annealing on the Defect Removal and the Reduction of Junction Depth in Excimer Lase
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The Influence of Low Temperature Pre-Annealing on the Defect Removal and the Reduction of Junction Depth in Excimer Laser Annealing Sungkweon Baek, Taesung Jang, and Hyunsang Hwang Department of Materials Science and Engineering, Kwangju Institute of Science and Technology, #1, Oryongdong, Buk-gu, Gwangju, 500-712, KOREA ABSTRACT The influence of low temperature pre-annealing on p+/n ultra-shallow junction was investigated. An ultra-shallow junction was formed by means of B2H6 plasma doping at an energy of 500V. The activation was performed by excimer laser annealing. To study the low temperature annealing prior to laser annealing, furnace annealing at 300oC∼500oC for 5min was performed. Compared with control samples with no pre-annealing, the low temperature preannealing significantly improves junction characteristics, resulting in a reduction of junction depth and a lower leakage current density. A cross-sectional transmission electron microscopy analysis confirmed the lower defect density, which explains the lower leakage current. By optimizing the process conditions, excellent electrical characteristics of the p+/n ultra-shallow junction such as a junction depth of 28nm and a sheet resistance of 250Ω/sq. can be obtained. INTRODUCTION The scaling of a metal-oxide-semiconductor field-effect-transistor (MOSFET) device channel length for high-speed application requires an ultra-shallow junction depth in order to suppress the short channel effect and to obtain high current drivability. Although a shallow junction can be formed by a rapid thermal annealing (RTA) process, it is difficult to form ultra-shallow junctions due to transient enhanced diffusion (TED)[1]. The excimer laser annealing was chosen as a candidate for the rapid thermal annealing. Compared with a RTA, excimer laser annealing has advantages, which include uniform distribution and full activation.[2,3] However, since the laser annealing was performed for a very short time, all defects generated by implantation cannot be removed. To solve this problem, the pre-annealing is needed. H. Tsukamoto et al. reported on the effect of annealing at 600oC for 1h prior to the laser annealing of a shallow junction prepared by BF2 implantation at 15keV. An improvement in crystallinity and a reduction in the generationrecombination centers due to annealing at 600oC for 1h were reported.[4] However they concluded that annealing at 600oC for 1h prior to laser annealing increases the junction depth. In this paper, we report on an investigation of the structural and electrical characteristics of C1.12.1 Downloaded from https://www.cambridge.org/core. Access paid by the UCSF Library, on 09 Nov 2019 at 20:25:18, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-717-C1.12
ultra-shallow p+/n junctions formed by plasma doping at 500V and low temperature preannealing at 300oC∼500oC for 5min followed by excimer laser annealing. The structural and electrical characteristics of ultra-shallow junction were
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