Sub-500 °C solid-phase epitaxy of ultra-abrupt p⁺-silicon elevated contacts and diodes

A well-controlled low-temperature process, demonstrated from 350 °C to 500 °C, has been developed for epitaxially growing elevated contacts and near-ideal diode junctions of Al-doped Si in contact windows to the Si substrate. A physical-vapor-deposited (PVD) amorphous silicon layer is converted to monocrystalline silicon selectively in the contact windows by using a PVD aluminum layer as a transport medium. This is a solid-phase-epitaxy (SPE) process by which the grown Si is Al-doped to at least 10¹⁸ cm^-3. Contact resistivity below 10^-7 Ω · cm ² is achieved to both p^- and p⁺ bulk-silicon regions. The elevated contacts have also been employed to fabricate p⁺-n diodes and p⁺-n-p bipolar transistors, the electrical characterization of which indicates a practically defect-free epitaxy at the interface.