Superconducting Resonator Etching to Cut TLS Interface Losses
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Solution Overview
Problem
Resonators in quantum computing face energy losses due to parasitic two-level systems (TLS) defects in substrates and native oxide layers, leading to reduced quality factors and coherence times, especially at low microwave field levels and temperatures.
Innovation Solution
A method involving a liquid acidic etching solution with a higher etch rate towards the substrate than the resonator is used to reduce the interface area and smooth the resonator surfaces, eliminating the need for photoresists and minimizing TLS losses by rounding edges and removing native oxides, thereby enhancing the quality factor and coherence time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If photoresist is used to underetch resonator and reduce interface area, then TLS losses are reduced, but defects are introduced on resonator surfaces causing further losses
Solution Approach 1:
The patent removes the photoresist step from the process entirely. Instead of using photoresist to protect the resonator during etching, the method directly applies the etching solution to the resonator-substrate interface, extracting the harmful photoresist material from the process chain and eliminating the associated surface defects.
Solution Approach 2:
The patent introduces a carefully controlled etching solution as an intermediary that selectively removes substrate material at the interface without damaging the resonator. This intermediary chemical agent mediates between the need to reduce interface area and the need to preserve resonator surface quality, achieving both goals simultaneously.
2Loss of energy
If interface area between resonator and substrate is reduced, then TLS losses are reduced, but manufacturing complexity increases
Solution Approach 1:
The etching solution is applied in a way that allows the system to self-regulate the interface reduction process. The chemical etching naturally progresses until equilibrium is reached, automatically achieving optimal interface area reduction without requiring complex external control mechanisms or multiple processing steps.
Solution Approach 2:
The patent changes the etching parameters (solution composition, temperature, time) to optimize the etching rate and selectivity. By carefully controlling these parameters, the process achieves effective interface area reduction while maintaining simplicity and avoiding the need for complex manufacturing procedures.
3Ease of manufacture
If resonator edges are sharp, then manufacturing is simpler, but radiative losses increase reducing quality factor
Solution Approach 1:
The patent applies controlled curvature to the resonator edges through the etching process. Instead of maintaining sharp edges for manufacturing simplicity, the method introduces gentle rounding that reduces radiative losses while adding minimal complexity to the manufacturing process. The curvature is optimized to balance manufacturing ease with performance improvement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively reduces energy losses in resonators, achieving high-quality factors and long coherence times without the use of photoresists, and is particularly suited for niobium or tantalum resonators, ensuring reproducible resonator properties.
Implementation Method 1
contacting the resonator and the substrate with a liquid acidic etching solution selected to have a higher etch rate towards the substrate than towards the resonator
Implementation Method 2
rounding edges and removing native oxides
Implementation Method 3
removing native oxides
Data Source
AI summary
A method for forming a modified resonator is provided. In one aspect, the method includes obtaining a resonator on top of a substrate, thereby forming an interface area between a bottom surface of the resonator and a top surface of the substrate. The resonator can include niobium or tantalum. The method also includes contacting the resonator and the substrate with a liquid acidic etching solution selected so as to have a higher etch rate towards the substrate than towards the resonator and a nonzero etch rate towards the resonator.