Treatment uniformity of plasma immersion ion implantation studied with three-dimensional model systems

Plasma immersion ion implantation is a rapidly developing technique for ion-beam treatment of materials, mainly metals and semiconductors. This technique was developed initially to circumvent the line-of-sight restrictions of conventional beam-line ion implantation. In contrast to the latter, the treatment of three-dimensional samples does not require complicated manipulation of the workpiece and ion beam. With this concept, knowledge of treatment homogeneity is of particular importance for the further development of plasma immersion ion implantation. In the present paper, homogeneity measurements of model systems are discussed. Silicon wafer segments mounted on wedge-shaped and V-shaped sample holders with different edge angles (30 degrees to 120 degrees), and on a U-shaped sample holder (trench), were treated by plasma immersion ion implantation with argon ions of -45 kV high-voltage pulses. The samples were analysed for lateral implantation concentration by Rutherford backscattering spectrometry measurements. The results show that, for wedge-shaped samples, gradients in concentration of implanted argon by a factor of up to six develop, depending on the process parameters. In the case of trenches, differences of more than an order of magnitude between the implantation concentrations of the side walls and bottom of the trench were found. (C) 1998 Elsevier Science S.A.