Low temperature selective Si epitaxy by reduced pressure chemical vapor deposition introducing periodic deposition and e
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Low temperature selective Si epitaxy by reduced pressure chemical vapor deposition introducing periodic deposition and etching cycles with SiH4, H2 and HCl Hong-Seung Kim, Kyu-Hwan Shim, Jeong-Yong Lee1, and Jin-Yeong Kang SiGe Device Team, Microelectronics Technology Laboratory, Electronics and Telecommunications Research Institute, 161 Kajong-Dong, Yusong-Gu, Taejon, 305-350, Korea 1 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Gusung-Dong, Yusong-Gu, Taejon, 305-350, Korea ABSTRACT This paper presents the experimental results of selective Si epitaxial growth from 650 oC to 700 o C on (100) silicon wafers with oxide patterns using reduced pressure chemical vapor deposition with the SiH4-HCl-H2 gas system. In addition, an HCl etching process is introduced and the conditions of the deposition and etching processes are addressed to sustain the selectivity. As a result, we noted that the addition of HCl serves not only to reduce the growth rate on bare Si, but also to suppress the nucleation on SiO2. In these experiments it has been also observed that the Si layer was grown to 3 nm while sustaining the selectivity. Moreover, further introduction of the HCl etching process following the deposition allowed a 50 nm-thick film to sustain the selectivity for twenty periods. INRODUCTION Selective epitaxial growth (SEG) allows the fabrication of advanced device structures and is valuable in increasing device density and reducing parasitic capacitances. In fact, low temperature selective Si epitaxy is on going issue to be addressed for Si/SiGe heterostructure devices such as modulation-doped field effect transistors (MODFETs), metal-oxidesemiconductor field effect transistors (MOSFETs), and heterojunction bipolar transistors (HBTs) for applications in Si integrated circuit processing [1, 2]. Impurity diffusion, intermixing at Si/Si1-xGex interfaces, and relaxation of strain have been observed to deteriorate device performance. To improve such situations, it is known that SEG temperatures should be reduced to 700 oC or below. Currently, for low temperature selective Si epitaxy, non-chlorinated source gases such as SiH4 [3] and Si2H6 [4] are popularly used. However, it has such a limitation that selectivity is lost once a critical epitaxial layer thickness is reached. In this paper we describe our approach to extend the selective Si epitaxial layer thickness A8.2.1
range at 650 – 700 oC by introducing the periodic deposition and etching cycles. In our experiments, the SiH4/HCl/H2 gas system was used for deposition and HCl gas for etching with reduced pressure chemical vapor deposition. Thus, the dependence of the SiH4/HCl ratio, the SiH4 and HCl flow rate, and the deposition and etching time on the growth rate and selectivity are also investigated. EXPERIMENTAL DETAILS Si films were grown using an ASM EPSILON-ONE reduced pressure CVD system that is a 125 mm, single wafer CVD module. The reactor has two N2 purged load lock chambers so that the deposition chambers are not e
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