Controlling the Threshold Voltage of MOSFET Transistors
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
A technique is described whereby the threshold voltage of MOSFET transistors is controlled through the use of fluorine-containing ions implanted into the gate insulator of the MOSFET transistor, so as to produce a positive flatband voltage shift. This then enables device performance to be enhanced, by providing an optimal choice of substrate doping parameters. In prior art, controlling the threshold voltage of MOSFET transistors was to adjust the surface doping density by ion implantation. However, limitations were evident particularly in scaled down devices. The surface doping density required by the threshold voltage could be sufficiently high to cause degradation of channel carrier mobility, reduction of the sub-threshold slope and increase in the body effect of the transistor.