Formation of Buried Oxide in Silicon by High-Dose Oxygen Implantation, and Application of this Technology to CMOS Device
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FORMATION OF BURIED OXIDE IN SILICON BY HIGH-DOSE OXYGEN IMPLANTATION,
AND
APPLICATION OF THIS TECHNOLOGY TO CMOS DEVICES
K. IZUMI, Y. OMURA, AND S. NAKASHIMA Atsugi Electrical Communication Laboratory, Atsugi-shi, Kanagawa 243-01, Japan
N.T.T.,
ABSTRACT
SIMOX (Separation by Implanted Oxygen) technology has been developed for realization of oxygen-ion implanted SOI. The distribution of implanted oxygen was analyzed by Auger electron spectroscopy and Rutherford backscattering spectroscopy. The properties of the silicon oxide formed by oxygenion implantation were investigated by infrared spectra, capacitance-voltage characteristics, dielectric strength, and dielectric constants. The crystallinity of the top layer silicon and of the epitaxially-grown silicon layer was determined by electron-beam diffraction. An electric-field-shielding effect was observed in the polycrystalline silicon region which was formed between the top layer silicon and the buried oxide. High-speed digital and high-voltage analogue CMOS LSIs, a 1kb CMOS RAM and a BSH LSI, were successfully fabricated using SIMOX technology. INTRODUCTION Watanabe and Tooi first reported on formation of silicon oxide by oxygen-ion implantation in 1966[1]. Since that time, several groups have investigated the oxygen-ion implanted oxide[2-4], with the result that the oxide now has equivalent isolation characteristics to those for thermally-
grown silicon oxide.
The authors have achieved oxygen-ion implanted SOI,
called SIMOX [5], and its application to CMOS LSIs [6] instead of using the oxygen-ion implanted oxide for surface passivation only. The others have reproduced the authors' reports [7]. In the present work, basics and advances in SIMOX technology are discussed as well as its application to high-speed digital and high-voltage analogue CMOS LSIs. EXPERIMENTAL RESULTS AND DISCUSSION Properties of the Oxygen-ion Implanted Layer Oxygen-ion implantation ýpto silicyn was carried out to form silicon oxide with a dose of 1 x 101* 0+ cmat 32keV[8]. This implantation condition was selected to form stoichiometric Si0 2 on the surface of a silicon wafer. Figure 1 shows the infrared spectra of the oxygen-ion implanted samples. In the figure, broken line A is the spectrum of asimplanted silicon, while solid line B is the one after annealing at 900°C for one hour in N2. After annealing, the broad absorption peaks of the asimplanted sample have become sharp, and absorption peak positions have shifted towards 9.3, 12.5, and 22.5pm, respectively. These values are wellknown as absorption peaks for thermally-grown SiO2 . Therefore, it is concluded that the as-implanted oxide-like silicon region becomes Si0 2 as a result of post-implantation annealing. A cross-section of the capacitor used to investigate capacitance-voltage(C-V) characteristics of the oxygen-ion implanted silicon layer is shown in Fig. 2(a). The diameter of the capacitor was 600pm, and 0.5pm thick aluminum was deposited to act as an electrode, followed by annealing at 4009C for 30min in H2 . The capacita
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