Nanofabrication processes for single-ion implantation of silicon quantum computer devices

Full text: We report on the progress of three nanofabrication regimes for the construction of silicon-based quantum computer devices. The devices are based on single phosphorous-31 ions implanted in silicon, all utilising a combination of single and multi-layer resist structures, metal structures, electron beam lithography and multi-angle aluminium shadow evaporation to precisely align gates and read-out components to an implanted ion. The first scheme involves a trilayer organic resist structure with an electron beam written pattern that defines both the implant channels as well as a shadow mask for self-aligned gates and read-out structures. In the second scheme, the central resist layer is substituted with a germanium layer, which has the advantage of a enabling dry-etch processing which can achieve narrow channels for the implantation stage. In the third scheme, the metal gate array in conjunction with a single patterned layer of resist forms the mask for the implantation stage. In this case, read-out structures are produced in a separate fabrication step using a double resist layer. The relative merits of each of these three schemes will be discussed and progress towards the fabrication of a fully-functional quantum computer device will be presented