Min Yong Lee

Novel threshold voltage fine control method for FETs within a wafer using LDSi (Locally Differentiated Scanning ion implant)

The novel threshold fine voltage (hereafter Vt) control method within a wafer was successfully developed. The locally differentiated scanning ion implant (hereafter LDSi) was developed in order to equalize Vt within a whole wafer. The wafer that was done by LDSi method showed very small Vt variation range of 117mV @ thin PMOS short channel (Vt range made by conventional implant without LDSi : 224mV). There was no long channel Vt shift. The portion of high speed DRAMs over 1GHz was increased from 47% to 84% by LDSi without IDD2 fail rate loss. Without decreasing of wafer per hour, we got the dramatic results.