In this contribution, we will discuss epitaxial Si growth by means of CVD at temperatures down to 330 °C and using tetrasilane (Si4H10) as Si precursor. Replacing Si3H8 by Si4H10results in ~40% higher growth rates. The growth rate also depends on the choice of the carrier gas and is affected by the underlying virtual substrate . The Si growth characteristics are discussed in view of the use for Ge surface passivation in the high-k gate module [4-6]. We use relaxed Ge fins for nFINFET devices and compressively strained Ge epitaxially grown on SiGe virtual substrates for pFINFET devices [1,3]. The deposition of the Si passivation layer on relaxed or compressively strained Ge FinFET structures is expected to be conformal as the extracted growth rate is very similar for (001) and (110) surfaces. For the given Si growth conditions, Ge segregation into the Si epi layer is supressed as confirmed for Si growth on blanket virtual substrates. CV characteristics of blanket capacitors made on such Ge virtual substrates point to the presence of an optimal Si thickness. In case of strained Ge fin structures, the Si growth results in non-uniform and high strain levels in the strained Ge fin. The non-uniform strain is caused by the extremely large lattice mismatch between the Si passivation layer and the Ge fin. Using atomistic modelling, the strain levels in the compressively strained Ge have been calculated for different shapes of the Ge fin and in function of the grown Si thickness. The high strain is the driving force for eventual Ge surface reflow during the Si deposition. The unwanted Ge surface reflow is reflected in a reduction of the compressive strain as measured by HR-XRD. The Ge surface reflow is strongly affected by the strength of the H-passivation during Si-capping and can be avoided by carefully selected process conditions.
The imec core CMOS program members, European Commission, local authorities and the imec pilot line are acknowledged for their support. Epi layers are grown in EpsilonTM3200 and IntrepidTMXP systems from ASM. Air Liquide Advanced Materials is acknowledged for providing advanced precursor gases and Bruker Semiconductor Division for their kind support in XRD characterization of high mobility materials implemented in complex device architectures.
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 R. Loo et al. accepted for The 10th Int. Conf. on Silicon Epitaxy and heterostructures (ICSI10)
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 H. Arimura et al. accepted for 2017 Symposium on VLSI Technology