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

We describe progress in nanofabrication processes for the production of silicon-based quantum computer devices. The processes are based on single-ion implantation to place phosphorus-31 atoms in accurate locations, precisely self-aligned to metal control gates. These fabrication schemes involve multi-layer resist and metal structures, electron beam lithography and multi-angled aluminium shadow evaporation. The key feature of all fabrication schemes is an integrated combination of patterns in different resist and metal layers that together define self-aligning metal gate structures as well as channels down to the substrate through which to implant the phosphorus. Central to this process is a new technique that allows for control and detection of the implantation process at a single-ion level.