Fabrication of Si-Gate CMOS Devices In A Heteroepitaxial Si/Caf 2 /Si Structure
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FABRICATION OF Si-GATE CMOS DEVICES IN A HETEROEPITAXIAL Si/CaF 2 /Si STRUCTURE HIROSHI ONODA, MASAYOSHI SASAKI, TERUO KATOH, and NORIO HIRASHITA VLSI Research & Development Center, OKI Electric Industry Co.,Ltd. Higashiasakawa, Hachioji, Tokyo 193, Japan
ABSTRACT The results of recent developments on device fabrication in a heteroepitaxial Si/CaF /Si structure have been presented and discussed. A high quality heteroepitaxial Si/CaF /Si structure has been obtained by successive molecular beam epitaxy 0?CaFZ and Si. The epitaxial Si film on CaF 2 /Si structure has an ion channeling minimum yield of 7 %. It was found, however, that Ca and F segregated at the surface of epitaxial Si films. A possibility of reducing the segregation effect by the use of solid phase epitaxy of Si has been proposed. Si-gate CMOS devices have been successfully fabricated in a Si/CaF /Si structure with altimproved CMOS proress. The maximum effective mobiliiies are about 570 cm /V.sec and 240 cm /V.sec for n-channel and p-channel transistors, respectively. Propagation delays below 360 ps have been = 2 u*m.These results indicate obtained for CMOS inverter chains with L that the Si/CaF 2 /Si structure has potential for the fabrication of high-speed silicon-on-insulator devices.
INTRODUCTION Heteroepitaxial growth of Si on CaF 2 /Si structures has potential applications for formation of silicon-on-insulator devices and three-dimensional integrated circuits. Film growth and film characterization have been investigated by several groups, and successful epitaxial growth of CaF 2 on Si, and Si on CaF /Si has been reported[l],[2],[3]. Device applications of an epitaxial CaF film have been studied by some groups. Metal-epitaxial insulator-semiconductor transistors by using CaF 2 as a gate insulator have been reported by Smith et al[4]. Asano and Ishiwara have reported fabrication of A!-gate field effect transistors in a Si/CaF 2 /Si(I00) structure[5]. However, there are no reports on the integrated circuits in the structure, so far. We have investigated on the applications of the Si/CaF 2 /Si structure to silicon-on-insulator integrated circuits[6],[7],[8]. The present paper deals with the results of recent developments on Si-gate device fabrication in a heteroepitaxial Si/CaF /Si structure. Growth conditions and crystalline quality of Si on CaF 2 /Si structures are first discussed. High quality of Si epitaxial growth by molecular beam epitaxy (MBE) is shown. It was found, however, that Ca and F segregated at the surface of epitaxial Si films. A possibility of reducing the segregation effect is described. An improved Si-gate CMOS process for a Si/CaF 2 /Si structure is then presented. Transistor characteristics are presented and compared with those observed in transistors prepared on bulk Si. Finally, the high speed performance of CMOS devices fabricated in a Si/CaF 2 /Si structure is shown. Mat. Res. Soc. Symp. Proc. Vol. 91.
1987 Materials Research Society
350
EPITAXIAL GROWTH Experiments Three inch p-type(l00) oriented Si wafers with a resis
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