  Full-scale quantum computers require the integration of millions of quantum
bits. The promise of leveraging industrial semiconductor manufacturing to meet
this requirement has fueled the pursuit of quantum computing in silicon quantum
dots. However, to date, their fabrication has relied on electron-beam
lithography and, with few exceptions, on academic style lift-off processes.
Although these fabrication techniques offer process flexibility, they suffer
from low yield and poor uniformity. An important question is whether the
processing conditions developed in the manufacturing fab environment to enable
high yield, throughput, and uniformity of transistors are suitable for quantum
dot arrays and do not compromise the delicate qubit properties. Here, we
demonstrate quantum dots hosted at a 28Si/28SiO2 interface, fabricated in a 300
mm semiconductor manufacturing facility using all-optical lithography and fully
industrial processing. As a result, we achieve nanoscale gate patterns with
remarkable homogeneity. The quantum dots are well-behaved in the multi-electron
regime, with excellent tunnel barrier control, a crucial feature for
fault-tolerant two-qubit gates. Single-spin qubit operation using magnetic
resonance reveals relaxation times of over 1 s at 1 Tesla and coherence times
of over 3 ms, matching the quality of silicon spin qubits reported to date. The
feasibility of high-quality qubits made with fully-industrial techniques
strongly enhances the prospects of a large-scale quantum computer
