Trench doping conformality by plasma immersion ion implantation (PIII)

Plasma immersion ion implantation (PIII) is a technique which can be used to conformally dope sidewalls of Si trenches. Using junction staining techniques and subsequently calibrating the observed stained depth to measured dose, dopant distributions inside Si trenches with aspect ratios ranging from 1 to 12 are studied for various bias voltages from 5 to 20 kV. Unlike conventional collimated beam implantation, PIII was able to conformally dope all aspect ratios studied with no evidence of abrupt discontinuities in the dopant distribution along the trench surface as a result of beam shadowing by trench geometry. Furthermore, it is shown that the higher implant biases results in more directional trajectories. Thus, dopant distributions along irregular geometries can be controlled by PDIII process conditions. >