Target temperature simulation during fast-pulsing plasma immersion ion implantation

The sample temperature during plasma immersion ion implantation (PIII) of metals and semiconductors is crucial as it affects the resultant surface properties and structures. In elevated temperature PIII processes such as fast-pulsing, low-voltage PIII, the target temperature is very time dependent, particularly during the temperature rise, and accurate prediction and knowledge of the target temperature is vital. In addition, there is likely to be temperature variation across the target surface that can lead to locally different surface properties. In this paper, we describe a two-dimensional fluid model to simulate the sheath dynamics when a negative high voltage is applied to a sample with a typical PIII geometry. The equations are solved by finite difference to derive the ion distribution, sheath configuration, ion flux to the target, and energy imparted to the substrate by the ions. The calculated heat input is used to predict the temperature rise. Using this model, the effects of the implantation voltage, pulse duration, pulsing frequency, as well as plasma density on the target temperature can be determined. The developed model can be combined with experimental data acquired from a small area by using a pyrometer or thermocouple to derive the temperature distribution on the entire surface.