The Study of the Formation of Thin SOI Structure by SIMOX with Water Plasma

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The Study of The Formation of Thin SOI Structure by SIMOX with Water Plasma Chen Jing, Chen Meng, Wang Xiang, Dong Yemin, Zheng Zhihong, and Wang Xi Ion Beam Laboratory, Shanghai Institute of Metallurgy, Chinese Academy of Sciences 865 Changning Road, Shanghai 200050, China ABSTRACT The biggest drawback of the widely application of SIMOX-SOI material is the low yield and the high cost which mainly due to the long implantation time by conventional beamline implanter. An implanter without an ion mass analyzer is used to fabricate SOI materials by H2O+, HO+, and O+ ions implantation using water plasma. Based on the consideration that the masses of the three ions of are quite close, their depth profiles in as-implanted wafers will not disperse much, which makes it possible for the formation of a single buried oxide layer by choosing the appropriate energy and dose. The results show that it exits a dose window at fixed implantation energy to form desirable thin or ultra-thin SOI structure with the buried oxide layer free of silicon islands. Compared to conventional SIMOX method, the sample implanted at the same dose and energy has thicker BOX layer. This probably caused by the heavy oxygen damaged region with hydrogen-induced defects in as-implanted wafer appears to be the adsorption center for the outside oxygen to diffuse into the silicon during the high-temperature annealing process. INTRODUCTION Recently, there has been a great interest in using SIMOX wafers for mainstream ULSI CMOS applications, which offer significant advantages in gain, speed, operating temperature and power consumption. However, when using conventional beamline implanter, the low yield and the high cost of SIMOX-SOI wafer will limit its wide use in the CMOS industry. An alternative method is to implant at a lower energy and lower dose of oxygen into silicon. It has been demonstrated that thin SOI structures can be formed by combining both a lower energy and dose [1]. Another novel technique like plasma immersion ion implantation (PIII) allows fabricating low cost SOI wafers as the processing time is short and independent of wafer size [2]. But the process has unresolved obstacle such as energy dispersion at pulse edge and frequently oxidation phenomena at present. In this paper, an ion implanter without mass selector (Eaton Z-200), instead of PIII system, was employed to simplify the process to fabricate SOI material but really with much higher ion current compare to conventional beam line implanter. The implanter has no mass selector, which means all the ions generated in the ion source will arrive in the processing substrate, just as in the case of PIII. However, co-existence of O+ and O2+ ions in the oxygen plasma causes a spread in the oxygen implant depth profile due to large variation in ionic mass, giving rise to non-uniformity in the oxide formation. In our work, water plasma was used as a source of oxygen for achieving a small spread in the oxygen implant profile. H2O+, HO+, and O+ ions, which are present in the water plasma, have compar