Qubits made by advanced semiconductor manufacturing

Spin qubits that are hosted in electrically-controlled, silicon quantum dots are promising candidates for the implementation of quantum processors. To pave the road towards large-scale quantum computing, millions of high-yield, uniform qubits are required. For classical processors, these conditions are reached by using advanced manufacturing techniques such as optical lithography and chemical-mechanical polishing. Due to the resemblance to transistors, silicon spin qubits are often claimed to be able to leverage decades of technology development in the semiconductor industry. However, the methods used in industry fabrication lines are little flexible and more intrusive than the processes that are currently used for quantum dot fabrication. It is therefore an outstanding question whether these techniques allow for the fabrication of quantum dot structures and whether the industrial processing conditions that ensure high-yield transistor fabrication do not compromise qubit quality and coherence.

 

Here, we manufacture quantum dot devices in isotopically enriched 28Si-MOS, fabricated in a standard 300-mm process line. These devices are fully fabricated with optical lithography and chemical-mechanical polishing techniques for patterning, compatible with state-of-the-art industrial fabrication. We demonstrate that this allows for exceptionally high yield and sample uniformity across a 300 mm wafer. Moreover, the samples exhibit well-controlled single and double quantum dot behaviour in the multi-electron regime. We perform charge sensing with a signal-to-noise ratio high enough for single-shot readout and form qubits in the single-electron regime, with spin coherence properties comparable to those reported in the literature. This work highlights the potential for scalability of spin qubits.