Effects of beam incident angle control on NMOS source/drain extension applications

As CMOS device technology is scaled in pursuit of ever improving circuit performance requirements, ion implant processing must meet the demands imposed by this device scaling. Control of beam incident angle on high current implanters is one unprecedented criterion imposed on modern ion implant doping technology. While other implant doping characteristics can be easily evaluated using bare wafer analysis techniques, the angular integrity of the ion beam cannot. Shadowing is one consequence of the uncontrolled beam incident angle that leads to dose inaccuracy at the microscopic scale in device regions of interest. Such effects can only be evaluated in association with their device performance. This paper describes the effects of beam incident angle control on source/drain extension (SDE) doping for a state-of-the-art CMOS transistor technology. Device characteristics were measured and analyzed to evaluate the ion beam shadowing effects at an individual device level. This paper also suggests the level of angle control required in ion implant systems based on device characterization results.