A futuristic quantum computing chip submerged in liquid nitrogen.

Unlock Quantum Potential: How Cold Development Revolutionizes Chip Manufacturing

Mira Elwood in Tech & Innovation August 2025 • 4 min read.

"A deep dive into the innovative cold-development technique, enhancing the fabrication of Josephson junctions for advanced quantum computing and superconducting circuits."

Quantum computing, once a theoretical dream, is rapidly becoming a tangible reality, fueled by advancements in superconducting circuits. At the heart of these circuits lie Josephson junctions, tiny devices that act as the quantum equivalent of switches. Their performance critically impacts the stability and coherence of quantum bits (qubits), the fundamental building blocks of quantum computers. These junctions are frequently constructed using aluminum and aluminum oxide (Al/AlOx/Al) due to their relatively long coherence times and ease of manufacture.

Fabricating these junctions, however, is no small feat. The conventional methods often struggle with precision and reliability at the nanoscale, hindering the overall progress of quantum computing. Factors like the quality of substrate materials, such as silicon and sapphire, and the intricacies of fabrication processes play critical roles. The goal is to create junctions with well-defined geometries and minimal defects to maximize qubit coherence – the time during which a qubit can reliably perform calculations.

Now, a new approach is gaining traction: cold development. This technique, involving extremely low temperatures during the fabrication process, promises to significantly enhance the precision and repeatability of creating Josephson junctions, paving the way for more robust and powerful quantum computers.

The Chilling Effect: How Cold Development Works

A futuristic quantum computing chip submerged in liquid nitrogen.

Cold development is a fabrication process carried out at temperatures as low as -20°C. The primary goal is to improve the electron-beam lithography (EBL) process, which is used to create the incredibly small patterns needed for Josephson junctions. During EBL, a beam of electrons etches a pattern onto a resist layer, typically made of materials like methyl methacrylate (MMA) and polymethyl methacrylate (PMMA).

The magic of cold development lies in its ability to control the behavior of these resist materials. At room temperature, the resist can be overly sensitive, leading to imperfections and inconsistencies in the final pattern. By chilling the development process, the viscosity of the PMMA increases substantially, and the dissolution rate of molecules gets slowed. This reduction translates directly into several key benefits:

Reduced Sensitivity: The resist becomes less reactive to the developer, providing finer control over the etching process.
Minimized Imperfections: Fewer molecules are washed away from the edges of the etched trenches, resulting in sharper and more defined patterns.
Enhanced Repeatability: The process becomes more consistent, ensuring that each junction is nearly identical to the last.
Increased Dose Margins: The range of acceptable electron beam exposure doses widens, making the process more forgiving and easier to optimize.

In a recent study, scientists successfully employed cold development to fabricate Al/AlOx/Al Josephson junctions on both silicon and sapphire substrates. These substrates are favored in quantum computing due to their low dielectric loss tangents, which help maintain qubit coherence. The resulting junctions exhibited exceptional geometries and increased dose margins, demonstrating the effectiveness of the cold-development technique.

A Quantum Leap Forward

The development and application of cold development techniques mark a significant step towards creating more reliable and efficient quantum computers. By improving the fabrication of Josephson junctions, this method addresses a critical bottleneck in quantum technology. As research continues and these techniques are refined, we can expect to see even more powerful and stable quantum systems emerge, unlocking unprecedented computational capabilities and pushing the boundaries of scientific discovery.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1007/s11433-018-9298-3, Alternate LINK

Title: Fabrication Of Al/Alox/Al Josephson Junctions On Silicon And Sapphire Substrates Using A Cold-Development Technique

Subject: General Physics and Astronomy

Journal: Science China Physics, Mechanics & Astronomy

Publisher: Springer Science and Business Media LLC

Authors: Wei Chen, Jiazheng Pan, Zuyu Xu, Yangyang Lv, Xianjing Zhou, Xuecou Tu, Jun Li, Guozhu Sun, Huabing Wang

Published: 2018-12-17

Everything You Need To Know

What is 'cold development,' and how does it enhance the fabrication of Josephson junctions?

Cold development is a fabrication process conducted at temperatures as low as -20°C. Its main purpose is to refine electron-beam lithography (EBL), which is essential for creating the tiny patterns required for Josephson junctions. By chilling the development process, the viscosity of the PMMA increases substantially, and the dissolution rate of molecules gets slowed. This process improves control over etching, minimizes imperfections, enhances repeatability, and increases dose margins, leading to more precise and consistent Josephson junctions.

What are Josephson junctions, and why are they essential in quantum computing?

Josephson junctions are crucial components in superconducting circuits, acting as quantum switches. They significantly impact the stability and coherence of qubits, which are the fundamental building blocks of quantum computers. These junctions are often made using aluminum and aluminum oxide (Al/AlOx/Al) because of their relatively long coherence times and ease of manufacturing. The performance of quantum computers heavily relies on the quality and reliability of these junctions.

How does electron-beam lithography (EBL) work, and what role does cold development play in this process?

Electron-beam lithography (EBL) is used to create the incredibly small patterns needed for Josephson junctions. During EBL, a beam of electrons etches a pattern onto a resist layer, typically made of materials like methyl methacrylate (MMA) and polymethyl methacrylate (PMMA). Cold development enhances the EBL process by reducing the sensitivity of the resist materials, minimizing imperfections, and increasing repeatability. This makes the fabrication of Josephson junctions more precise and consistent.

What are the potential implications of using cold development techniques for quantum computing advancement?

Cold development improves the fabrication of Josephson junctions, leading to more reliable and efficient quantum computers. The cold development technique enhances the precision and repeatability of creating Josephson junctions. As these techniques are refined, we can expect to see even more powerful and stable quantum systems emerge, unlocking unprecedented computational capabilities and pushing the boundaries of scientific discovery.

What are the challenges with traditional Josephson junction fabrication methods, and how does 'cold development' address them?

Traditional methods of fabricating Josephson junctions often struggle with precision and reliability at the nanoscale, hindering the advancement of quantum computing. Factors such as the quality of substrate materials like silicon and sapphire, as well as the complexities of fabrication processes, play critical roles. The goal is to create junctions with well-defined geometries and minimal defects to maximize qubit coherence. Cold development addresses these issues by providing better control and consistency during fabrication.