Fabrication process and failure analysis for robust quantum dots in silicon

Abstract

We present an improved fabrication process for overlapping aluminum gate quantum dot devices on Si/SiGe heterostructures that incorporates low-temperature inter-gate oxidation, thermal annealing of gate oxide, on-chip electrostatic discharge (ESD) protection and an optimized interconnect process for thermal budget considerations. This process reduces gate-to-gate leakage, damage from ESD, dewetting of aluminum and formation of undesired alloys in device interconnects. Additionally, cross-sectional scanning transmission electron microscopy (STEM) images elucidate gate electrode morphology in the active region as device geometry is varied. We show that overlapping aluminum gate layers homogeneously conform to the topology beneath them, independent of gate geometry and identify critical dimensions in the gate geometry where pattern transfer becomes non-ideal, causing device failure.

Materials for Silicon Quantum Dots and their Impact on Electron Spin Qubits

“…Transmission electron microscope (TEM) images of gate stack in quantum dot devices made in academic laboratories a) UNSW, and b) University of Wisconsin; [ 130 ] and in foundries c) Intel, [ 97 ] d) IMEC. [ 131 ] Reproduced with permission.…”

“…[ 131 ] Reproduced with permission. [ 97,130,131 ] Copyright 2020, IOP Publishing. Copyright 2021, The Authors, published by arXiv.…”

Advances and opportunities in materials science for scalable quantum computing

“…29 Above the semiconductor itself, electrostatic potentials applied to multiple layers of overlapping gates confine the electrons. The choice and thickness of gate dielectric, 30 gate metal, 31,32 and inter-gate insulation layer, 33 as well as the different interfaces in the device, 34,35 are all critical aspects of the device design that can impact its performance. Analogous issues associated with materials choices, interfaces, defects, and fabrication processes affect all types of qubit technologies.…”

SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits

“…Electron beam lithography was used to pattern three layers of overlapping aluminum gates isolated from one another by the plasma-ash enhanced self-oxidation of the aluminum metal, following the procedure described in Ref. [25]. (See Methods.)…”