  We report on a flexible 300 mm process that optimally combines optical and
electron beam lithography to fabricate silicon spin qubits. It enables
on-the-fly layout design modifications while allowing devices with either n- or
p-type ohmic implants, a pitch smaller than 100 nm, and uniform critical
dimensions down to 30 nm with a standard deviation ~ 1.6 nm. Various n- and
p-type qubits are characterized in a dilution refrigerator at temperatures ~ 10
mK. Electrical measurements demonstrate well-defined quantum dots, tunable
tunnel couplings, and coherent spin control, which are essential requirements
for the implementation of a large-scale quantum processor.
