Low energy plasma enhanced chemical vapor deposition

We present a state-of-the-art growth technique, introduced recently for SiGe heteroepitaxy. At present, its most important application is the fast fabrication of high-quality relaxed SiGe buffer layers. The process is based on chemical vapor deposition (CVD), enhanced by a high intensity, low energy plasma, which is why we call it ‘low energy plasma enhanced CVD’ (LEPECVD). The key features of the process are a wide range of epitaxial growth rates (<1 Å s−1 up to at least 10 nm s−1), independent of the substrate temperature in the range of 500–750 °C and easy control of film composition, governed solely by the mixture of the precursor gases (SiH4 and GeH4). Possible applications of LEPECVD include electronic devices, such as modulation doped SiGe FETs (SiGe-MODFETs) or strained-layer SiGe MOSFETs, all based on relaxed buffer layers and targeting the fast-growing RF device market. Another field of applications is high-performance SiGe solar cells. For economic production, all these devices rely on fast, high-quality epitaxy, which is the strength of LEPECVD. The process, developed on the experimental system for 4-inch wafers, is now being transferred to a 300-mm single wafer reactor for production.