Application of a pulsed, RF-driven, multicusp source for low energy plasma immersion ion implantation

The multicusp ion source has the capability of producing large volumes of uniform, quiescent, high density plasmas. Due to the versatility of the multicusp source, a plasma chamber suited for plasma immersion ion implantation (PIII) was readily constructed. Conventional PIII pulses the bias voltage applied to the substrate which is immersed in a CW mode plasma. However, in the interest of finding a more efficient and improved means of implantation, a method by which the plasma itself is pulsed was developed. Typically pulse lengths of 500 μs are used and are much shorter than that of the substrate voltage pulse (~5 to 15 ms). This approach, together with low gas pressures and low bias voltages, permits the constant energy implantation of an entire wafer simultaneously without glow discharge. Results show that this process can yield implant currents of up to 2.5 mA/cm², and thus very short implant times can be achieved. Uniformity of the ion flux will also be discussed. Furthermore, as this method can be scaled to any dimension, it could be made to handle any size wafer