We propose carbon-doped polycrystalline silicon or silicon-germanium (SiGe) gate contacts for metal-oxide semiconductor field effect transistors (MOSFETs). Polycrystalline SiGe is a promising alternative for gate contacts in MOSFETs, with useful properties including the ability to manipulate work function of the contact, enhanced dopant activation, and lower boron diffusion rates. Polycrystalline SiGe and silicon with low carbon (0.05-0.2%, denoted as SiGe : C and Si : C) should inhibit boron diffusion/penetration. As gate oxide thickness shrinks in higher frequency devices, inhibition of boron penetration from polycrystalline gated during high temperature processing is a limiting issue in MOSFETs. Recently, small amounts of carbon in silicon and SiGe layers have domonstrated significantly inhibited boron diffusion. The most common means to reduce boron penetration is nitridation of the gate oxide, which may be less radiation hard. Additionally, as dielectric thickness decreases, nitrided layer thickness also shrinks, reducing its effect as a diffusion barrier. Suppression of boron penetration may ultimately require both nitrided gated dielectrics and carbon doped polycrystalline electrodes. The primary goals are to determine the effect of carbon and thermal processing on boron penetration through the gate oxide, polycrystalline layer morphology and the capacitance voltage (CV) properties of the gate stack before and after radiation testing. Anticipated Benefits and
Potential Commercial Applications: Fabrication of smaller, faster, higher frequency, lower power integrated circuits (ICs) including: monolithic micorwave Ics (MMICs), satellite, cellular and other wireless communications (e.g. for wristwatch celllular phones). The potential effect of higher speed MOSFETS in digital applications such as microprocessors is enormous.
