Effect of energy contamination on the p-channel transistor characteristics

The Nwell and Pwell retrograde implants are high-energy implants requiring double charge implants for some cases. The energy contamination for double charge implant poses strict control on implanter performance, with critical control on the vacuum levels on the implanter. Even with well-controlled ultra high vacuum, the energy contamination is inevitable caused by pressure changes due to resist out gassing and vacuum integrity. This poses severe challenges in tool matching between High Energy (HE) and Medium Current (MC) implanters. For the same energy the single charge implant on a HE needs to be matched to the double charge implant on a MC implanter to provide manufacturing flexibility and better utilization in a foundry environment. To achieve that a novel three step approach has been reported in this paper, to match the bulk, surface and punch through characteristics of the PMOS short and long channel transistors.