Ion-Beam Enhanced Stress-Relaxation of SiGe on SiO 2
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0908-OO05-21.1
Ion-Beam Enhanced Stress-Relaxation of SiGe on SiO2 M. Tanaka1, T. Sadoh1, M. Ninomiya2, M. Nakamae2, T. Enokida3, and M. Miyao1* 1 Department of Electronics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan 2 SUMCO Corporation, 2201 Oaza Kamioda, Kohoku-cho, Kishima-gun, Saga 849-0597, Japan 3 Analysis & Evaluation Center, Fukuryo Semicon Engineering Corporation, 1-1-1 Imajuku-Higashi, Fukuoka 819-0192, Japan ABSTRACT The Ge condensation by oxidation of SiGe/Si-on-insulator (SOI) structures enabled highly stress relaxed SGOI. However, the relaxation rate obtained in the SiGe layers on insulator (SGOI) abruptly decreased with decreasing SiGe thickness below 50 nm. In order to enhance the relaxation rate in ultra-thin SGOI, the technique combined with H+ irradiation with medium dose (5x1015 cm-2) and post-annealing (1200 oC) has been developed. It was demonstrated that highly relaxed (70 %) ultra-thin SGOI with low defect density (50 nm). However, the relaxation rate abruptly decreases with decreasing thickness below 50 nm. In this experiment, oxidation time is a hidden parameter. The samples with thicker SGOI layers were subjected to longer thermal treatment during oxidation, which might increase the relaxation rate. Thus, separation of effects of SGOI thickness (df) and oxidation time is necessary. In order to understand these phenomena, two sample structures (A: Si (7 nm)/Si0.93Ge0.07 (80 nm)/SOI, B: Si (30 nm)/Si0.85Ge0.15 (55 nm)/SOI) were employed. They were oxidized to condense Ge fraction to 30 % for both samples. The oxidation time, SGOI thickness, and relaxation rate for the samples A and B are summarized in table I. These results indicated that the relaxation rate for the thinner SGOI (19 nm) is smaller than that for the thicker SGOI (28 nm) in spite of the longer oxidation time (180 min). This clearly demonstrates that the relaxation rate depends on the SGOI thickness and decreases with decreasing thickness below 50 nm. This is a serious problem for realization of fully depleted strained Si devices. In order to enhance the relaxation rate in ultra-thin SGOI layers (
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