Oxide-induced deterioration of TiSi2 source/drain MOSFET contacts

A simple process for formation of a metal-oxide-semiconductor field-effect transistor (MOSFET) involves fabrication of a polysilicon/oxide gate between source and drain regions. Contact is made to source/drain regions by use of TiSi2 layers followed by Al(Cu) metal lines. A silicide layeris used toreduce contact resistance. TiSi2 is chosen as a contact layer because in the C54phase, the silicide has a lower resistivity (~12 μΏ-cm) than most other silicides (except for CoSi2 ~10-15 μΏ-cm). During formation of TiSi2 contact layers to MOSFET source/drain regions, a deterioration of the TiSi2 is occasionally observed. The deterioration typically consists of buckling and delamination of Ti(TiSi2) films from the source/drain regions. When buckling occurs, electrical contact between Al metal and MOSFET source/drain regions is quite poor. The present study investigates the microstructure and behavior of TiSi2 contact layers used at source/drain regions of MOSFETs. The cause of deterioration of contact-layers is investigated and a potential solution to this problem is explored.