Abnormal Silicon-Germanium (SiGe) Epitaxial Growth in FinFETs

Abstract

In an advanced complementary metal-oxide-semiconductor (CMOS) technology node, small nano-scopic defects tend to have a significant impact on the yield and reliability of the final product. As the technology advances in fin field-effect-transistors (FinFETs), it has become increasingly challenging to control the extent of defects while also ensuring that the desired processing parameters are in place. The process of selective epitaxial growth of silicon-germanium (SiGe) on source/drain (S/D) regions is especially prone to defects due to the complexity of the process, thus giving a very narrow processing window to achieve the desired device, yield and reliability results. In this paper we evaluate a critical defect of “Abnormal epi” seen during the selective epitaxial growth of in-situ boron (B) doped SiGe on FinFETs. Abnormal epi here refers to abnormally large and spurious epitaxial growth defect occurring as random instances on a wafer die. These defects, depending on where in the layout they occur, can lead to catastrophic failure under higher test voltages due to the physical shorting of n and p FET devices. We also explore the process parameters which influence this defect including incoming surface conditions and propose mechanisms that lead to the defect. Further, an optimization of the processing parameters in the integration scheme to minimize the occurrence of these defects leads to yield gain and cost savings required for high volume manufacturing.