Effect of Etching Methods on Dielectric Losses in Transmons

TL;DR

This study compares how wet and dry aluminum etching methods affect dielectric losses and coherence times in transmon qubits, finding dry etching significantly improves qubit performance and reduces defect-related losses.

Contribution

It provides experimental evidence that dry etching enhances qubit coherence and reduces dielectric losses compared to wet etching in transmon fabrication.

Findings

Dry-etched qubits have over twice the relaxation and coherence times.

Dry etching reduces the impact of two-level systems causing dielectric loss.

Time fluctuation analysis identifies lower defect impact in dry-etched devices.

Abstract

Superconducting qubits are considered as a promising platform for implementing a fault tolerant quantum computing. However, surface defects of superconductors and the substrate leading to qubit state decoherence and fluctuations in qubit parameters constitute a significant problem. The amount and type of defects depend both on the chip materials and fabrication procedure. In this work, transmons produced by two different methods of aluminum etching: wet etching in a solution of weak acids and dry etching using a chlorine-based plasma are experimentally studied. The relaxation and coherence times for dry-etched qubits are more than twice as long as those for wet-etched ones. Additionally, the analysis of time fluctuations of qubit frequencies and relaxation times, which is an effective method to identify the dominant dielectric loss mechanisms, indicates a significantly lower impact of two-level systems in the dry-etched qubits compared to the wet-etched ones.