On the reverse short‐channel effect and threshold voltage roll‐off controls for 90 nm node MOSFETs

In order to let device designers tune the short channel behavior of MOSFETs, a method is proposed in this work to demonstrate how to use LDD (lightly doped drain) and pocket implants to control RSCE (reverse short channel effect) and threshold voltage (Vt ) roll‐off. The method is based on the process parameters and silicon data of the 90 nm node technology of UMC (United Microelectronics Corporation). With the help of computers, 17 different process conditions of 8 different gate lengths were simulated using ISE TCAD to collect Vt variation data. Four characteristics representing the short channel behaviors of the MOSFETs were designed and extracted from the simulated data. Their empirical equations were also established subsequently. After verification, those mathematical models were demonstrated to help device designers in choosing the most suitable LDD and pocket implant parameters to generate required Vt characteristics.