Plasma Etching Techniques in Semiconductor Fabrication

Plasma etching has become the cornerstone of modern semiconductor fabrication, offering unparalleled precision in the removal of material from silicon, compound semiconductors and dielectric films. By generating reactive species in a partially ionised gas, plasma etching enables directional removal of material with controlled anisotropy and high selectivity, essential for patterning ever‐smaller features on integrated circuits. Techniques such as reactive ion etching (RIE), inductively coupled plasma deep reactive ion etching (ICP-DRIE) and atomic layer etching (ALE) cater to a range of requirements from bulk micromachining to atomic-scale profile control. Key process parameters include gas chemistry, radio-frequency power, chamber pressure and substrate bias, all of which influence ion energy, radical flux and surface reaction kinetics. The development of cryogenic etching regimes, advanced fluorinated gas mixtures and pulsed plasma operation has extended capabilities to create high-aspect-ratio trenches, vertical nanowires and ultra-smooth sidewalls with nanometre precision. These advancements underpin technologies in logic devices, memory, photonics and microelectromechanical systems (MEMS), driving improvements in device density, performance and yield across global semiconductor manufacturing.

Research from Nature Portfolio

Recent studies have explored the integration of human expertise and machine learning to accelerate the development of complex plasma etching processes. A controlled virtual platform benchmarked Bayesian-optimisation algorithms against experienced process engineers, revealing that humans excel in early exploratory design while algorithms outperform near tight tolerance regimes. A hybrid strategy—where human insight guides initial parameter choices and algorithms refine conditions at high precision—was shown to halve the cost and time required to achieve target etch profiles. This human-first, computer-last approach highlights both the promise of artificial intelligence in reducing experimental cycles and the cultural challenges of deploying AI tools in foundry environments.

Research from all publishers

Deep-reactive ion etching at cryogenic temperatures has been demonstrated for the fabrication of silicon nanowire arrays with diameters down to 30 nm and aspect ratios exceeding 100. By synchronising etch parameters such as SF₆/O₂ flow, substrate cooling and bias power, researchers achieved selectivities of up to 700 against hard masks, etch rates of 4 µm min⁻¹ and surface roughness below 1 nm. This work lays the foundation for scalable nanoarchitectures in energy, quantum and biomedical devices.

Atmospheric plasma jet etching has emerged as a low-cost alternative to vacuum-based pattern transfer. Using a CF₄/O₂ plasma jet, micron-scale aluminium patterns on fused silica were replicated with etch rates of 200 nm s⁻¹, albeit with isotropic profiles and moderate under-etching. This method promises high throughput and large substrate handling without the constraints of vacuum chambers, extending plasma etching to non-planar optics and large-area microfluidic devices.

A comprehensive review of high-aspect-ratio microfabrication highlights recent advances in RIE and ICP-DRIE for materials beyond silicon, including quartz, silicon carbide and compound semiconductors. Innovations in chamber design, gas pulsing and mask materials have enabled deeper etches while maintaining vertical sidewalls and minimising scalloping. The survey emphasises how developments in plasma sources and process control converge to meet the demands of three-dimensional integration and multifunctional system-on-chip architectures.

Plasma Etching Techniques in Semiconductor Fabrication publication trend

The graph below shows the total number of articles in plasma etching techniques in semiconductor fabrication across all publications each year (not limited to Nature Index journals).

Technical terms

Reactive ion etching (RIE): A dry-etching technique combining ion bombardment and chemical reactions to achieve anisotropic material removal.

Deep reactive ion etching (DRIE): A high-aspect-ratio RIE method, often employing alternating etch and passivation steps to create deep, vertical structures.

Atomic layer etching (ALE): A sequential, self-limiting process that removes material one atomic layer at a time for ultimate precision.

Aspect ratio: The ratio of structure depth to its lateral dimension, critical for defining three-dimensional device geometries.

Selectivity: The etch rate ratio between the target material and the masking or underlying layers, determining pattern fidelity.

Anisotropy: The directional dependence of etch rates, enabling vertical sidewalls rather than isotropic undercuts.

References

1. Human–machine collaboration for improving semiconductor process development. Nature (2023).
2. Deep-reactive ion etching of silicon nanowire arrays at cryogenic temperatures. Applied Physics Reviews (2024).
3. Transfer of micron pattern with reactive atmospheric plasma jets into fused silica. Applied Surface Science Advances (2024).
4. Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication. Micromachines (2021).