In a plasma immersion ion implantation process, the thickness of a pre-implant chamber seasoning layer is increased (to permit implantation of a succession of wafers without replacing the seasoning layer) without loss of wafer clamping electrostatic force due to increased seasoning layer thickness. This is accomplished by first plasma-discharging residual electrostatic charge from the thick seasoning layer. The number of wafers which can be processed using the same seasoning layer is further increased by fractionally supplementing the seasoning layer after each wafer is processed, which may be followed by a brief plasma discharging of the supplemented seasoning before processing the next wafer.