ION-IMPLANTATION OF DIAMOND AND DIAMOND FILMS

Ion implantation is widely employed in semiconductor device manufacture because it offers the possibility of precise control of dopant concentration and depth, and spatially selective doping is readily achievable using masking techniques. However, three major hurdles must be overcome before ion implantation doping of diamond can be practically realized. Firstly, methods must be found for the removal of the residual radiation damage without causing graphitization following the ion implantation. Secondly, the degree of electrical activation of the implanted dopants must be improved and thirdly, a suitable n-type dopant needs to be identified. Novel and innovative approaches designed to overcome these problems have recently been reported. These include pulsed laser annealing of deeply buried ion-implanted layers to achieve very high annealing temperatures while still preventing graphitization, the use of low energy ion-implantation during growth to minimize ion beam damage and maximize dopant incorporation into the diamond lattice, and multiple-step implantation/annealing cycles to improve dopant activation. In addition, fundamental studies examining the ion beam induced conductivity in diamond over a wide range of doses, ion energies and implantation temperatures have provided new insights into the nature of the damage introduced by the ion beam irradiation. In this paper, a brief review of the current status of our understanding of the interaction of ion beams with diamond is provided, with an emphasis on the new results mentioned above. In addition, since it is now clear that n-type doping of diamond films by addition of dopants to the chemical vapour deposition (CVD) growth mixture will not be as easy to achieve as first thought, a review of the work to date on the ion implantation of CVD diamond films is presented and the similarities and differences between the implantation of single crystal diamond and polycrystalline CVD films are discussed. Finally some novel and intriguing nonelectronic applications for ion beam modified diamond are presented.