DOPING AND PROCESSING EPITAXIAL GEXSI1-X FILMS ON SI(100) BY ION-IMPLANTATION FOR SI-BASED HETEROJUNCTION DEVICES APPLICATIONS

The question of whether one can effectively dope or process epitaxial Si(100)/ GeSi heterostructures by ion implantation for the fabrication of Si-based heterojunction devices is experimentally investigated. Re sults that cover several different ion species (B, C, Si, P, Ge, As, B F,, and Sb), doses (10(13) to 10(16)/cm(2)), implantation temperatures (room temperature to 150 degrees C), as well as annealing techniques (steady-state and rapid thermal annealing) are included in this minire view, and the data are compared with those available in the literature whenever possible. Implantation-induced damage and strain and their a nnealing behavior for both strained and relaxed GeSi are measured and contrasted with those in Si and Ge. The damage and strain generated in pseudomorphic GeSi by room-temperature implantation are considerably higher than the values interpolated from those of Si and Ge. Implantat ion at slightly elevated substrate temperatures (e.g., 100 degrees C) can very effectively suppress the implantation-induced damage and stra in in GeSi. The fractions of electrically active dopants in both Si an d GeSi are measured and compared for several doses and under various a nnealing conditions. Solid-phase epitaxial regrowth of GeSi amorphized by implantation has also been studied and compared with regrowth in S i and Ge. For the case of metastable epi-GeSi amorphized by implantati on, the pseudomorphic strain in the regrown GeSi is always lost and th e layer contains a high density of defects, which is very different fr om the clean regrowth of Si(100). Solid-phase epitaxy, however, facili tates the activation of dopants in both GeSi and Si, irrespective of t he annealing techniques used. For metastable GeSi films that are not a morphized by implantation, rapid thermal annealing is shown to outperf orm steady-state annealing for the preservation of pseudomorphic strai n and the activation of dopants. In general, defects generated by ion implantation can enhance the strain relaxation process of strained GeS i during post-implantation annealing. The processing window that is op timized for ion-implanted Si, therefore, has to be modified considerab ly for ion-implanted GeSi. However, with these modifications, the matu re ion implantation technology can be used to effectively dope and pro cess Si/GeSi heterostructures for device applications. Possible impact s of implantation-induced damage on the reliability of Si/GeSi heteroj unction devices are briefly discussed.