Long-pulse plasma immersion ion implantation using a grounded conduction grid

The use of a grounded conducting grid positioned between the plasma source and sample chuck has been shown theoretically to allow direct current (DC) plasma immersion ion implantation (PIII). In addition to retaining the large area and parallel processing advantages of PIII, the implantation energy monotonicity and dose uniformity can be improved. In this work, we investigate the PIII process with the conducting grid in the long pulse mode, as pure DC PIII has some limitations and is not required in many applications. We experimentally measure the sheath expansion process and plasma stabilization time and determine the optimal instrumental parameters in this mode of operation. For example, our data show that the following conditions: H₂ pressure = 5×10^-4 Torr, RF power = 1 kW, pulse width = 500 μs, and frequency = 1 kHz can yield good results. We also measure the impact energy and dose distributions, and observe that the power and time efficiency can be substantially improved using long-pulse PIII compared to conventional short-pulse PIII. Our experimental results further indicate that DC plasma implantation is very hopeful.