Comparison of zero degree and tilted arsenic MDD implants

N-type LDD´s are commonly formed using Phosphorus implants. Phosphorus has the advantage of easily forming graded junctions that are necessary for reducing hot carrier injection. However, as gate dimensions continue to decrease, short channel effects become excessive with Phosphorus. Arsenic has the advantage of lower diffusivity. This allows for higher doping levels while maintaining shallow junction depths; such structures are known as MDD´s. Replacing a zero degree Phosphorus implant with a zero degree Arsenic implant results in high field areas under gates. This increases hot carrier injection. Angled Arsenic implants with multiple twists spread junctions laterally. This reduces hot carrier injection while still retaining the other benefits of Arsenic