Quantum Computer Development with Single Ion Implantation

Abstract

Spins of single donor atoms are attractive candidates for large scale quantum information processing in silicon. Formation of devices with a few qubits is crucial for validation of basic ideas and development of a scalable architecture. We describe our development of a single ion implantation technique for placement of single atoms into device structures. Collimated highly charged ion beams are aligned with a scanning probe microscope. Enhanced secondary electron emission due to high ion charge states (e.g., 31 P 13+ , or 126 Te 33+ ) allows efficient detection of single ion impacts. Studies of electrical activation of low dose, low energy implants of 31 P in silicon show a drastic effect of dopant segregation to the SiO 2 /Si interface, while Si 3 N 4 /Si retards 31 P segregation. We discuss resolution limiting factors in ion placement, and process challenges for integration of single atom arrays with control gates and single electron transistors.

Strategies for integration of donor electron spin qubits in silicon

“…But a large fraction of donors appears to be ionized due to band bending at the ungated interface. We point out that the dopant movement is significantly less for antimony compared to low dose phosphorous implants in the presence of an SiO 2 /Si interface [7]. This is consistent with the different diffusion mechanisms for these two donors.…”

Critical issues in the formation of quantum computer test structures by ion implantation

“…Dopants diffuse and segregate during RTA through coupling to specific defects. Phosphorus is an interstitial diffuser [11][12][13][14]. Interstitials are injected from the SiO /Si interface into silicon during annealing under mildly oxidizing conditions (e. g. from residual water in the RTA chamber), while vacancies are 2 injected from silicon nitride.…”

Focusing a deterministic single-ion beam

“…However, although a wide range of postdetection schemes (e.g. the observation of Auger electrons, the generation of electron-hole pairs or changes in the conductance of field effect transistors) is available [5,6,7,8,9], most of these techniques either require highly charged ions or high implantation energies which, as a down side, generate unintentional defects in the host material. Another fabrication method revolves around the structuring of chemically treated Si-surfaces.…”

“…The trap consists of four copper plated polyimide blades which were manufactured using printed circuit board (PCB) technology and are arranged in a x-shaped manner [22]. It features a total of 15 independent dc electrodes which can be assigned to three different trap sections: A wide loading zone (electrodes 1-4) is connected via a taper (electrode 5) to a narrow experimental zone (electrodes [6][7][8][9][10][11][12][13][14]. A deflection electrode (electrode 15) is used to alter the trajectories of ions which are extracted out of the trap.…”