Subsurface Damage Characterization of Hydrogen Ion Implanted Silicon Wafer with Uv/Millimeter-Wave Technique
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SUBSURFACE DAMAGE CHARACTERIZATION OF HYDROGEN ION IMPLANTED SILICON WAFER WITH UV/MILLIMETER-WAVE TECHNIQUE Yoh-Ichiro Ogita, Ken-Ichi Kobayashi, Masaki Kurokawa, Hideyuki Kondo1, and Takeo Katoh1 Kanagawa Institute of Technology, Dept. Electrical & Electronic Engg,., 1030 Shimo-Ogino, Atsugi, Kanagawa, 243-0292, Japan 0LWVXELVKL0DWHULDOV&RUS6LOLFRQ5HVHDUFK&HQWHU .LWDEXNXURFKR2PL\D 6DLWDPD-$3$1
ABSTRACT The UV/mm-wave technique composed of ultraviolet photoexcitation and millimeter wave probe was examined with photoconductivity amplitude (PCA) to characterize the slight subsurface damage induced by implanting H2+ ion into the subsurface at sub micron depth of Si wafers. The identical samples were also characterized using pulse photoconductivity amplitude (PPCA) obtained by another technique which is specified by blue laser photoexcitation and microwave probe. PCA decreased with increase of ion dose, which coincided well with the result in PPCA. PPCA decreased with increase of implantation energy as 90 to 120 keV, but PCA increased at 120keV. Both PCA and PPCA well reflected the damage at sub micron depth. PCA reflected damage in shallower depth compared to PPCA. INTRODUCTION As the gate oxide thickness of MOS devices in ULSI is thinner, the gate oxide breakdown causes a serious problem. The causes are come from as-grown crystal defects; mirror polishing induced damage, micro roughness, and heavy metal contamination in subsurface of silicon wafers. Therefore, strict characterization of the subsurface is demanded. However, it is so easy to characterize property in the subsurface. Non-contact UV/millimeter-wave photoconductivity decay (UV/mm-wave PCD) technique in which millimeter-wave is used as a probe to detect the photoconductivity change induced by ultra violet photo-excitation has characterized a thin epitaxial layer in p/p+ and n/n+ silicon wafer [1]. Moreover, the technique has characterized the subsurface damage induced by mirror polishing [2-6]. The purpose of
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this paper is to confirm whether the technique truly characterize subsurface property in sub micron region. First, characterization for the sample in which B+ ion was implanted, was tried, but we did not detect any signals based on photoconductivity change. Because of heavy damage and too high sensitivity in the technique, it was hard to detect. It was tried to create slight damage nearby surface by H2+ ion implantation. In this paper, the slight damage is characterized by photoconductivity amplitude (PCA) signal or a decay time carrier measured by UV/Millimeter Technique. Further, it is also characterized by pulse photoconductivity amplitude (PPCA) measured by Blue-Laser/Microwave technique [7]. The effects between both techniques are discussed by comparing those measurement results. WAV
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