Nanocrystalline diamond-glass platform for the development of three-dimensional micro- and nanodevices

Citation

Janssens, S. D., Vázquez-Cortés, D., Giussani, A., Kwiecinski, J. A., & Fried, E. (2019). Nanocrystalline diamond-glass platform for the development of three-dimensional micro- and nanodevices. Diamond & Related Materials, 98, 107511. https://doi.org/10.1016/j.diamond.2019.107511

Keywords

• Nanocrystalline diamond (NCD)
• Through glass vias (TGVs)
• Microfabrication
• Glass etching
• Laser ablation
• 3D micro- and nanodevices
• Single-cell culture and analysis
• Microelectrodes
• Quantum technologies
• High-temperature MEMS

Brief

This article presents a low-cost process for fabricating a nanocrystalline diamond-glass platform that could be used for micro- and nanodevices.

Summary

The 2019 article "Nanocrystalline diamond-glass platform for the development of three-dimensional micro- and nanodevices" by Stoffel D. Janssens et al., published in Diamond & Related Materials, details a novel process for creating a nanocrystalline diamond-glass platform. This platform has potential applications in various fields, including single-cell analysis, drug delivery, microelectrodes, and high-temperature MEMS.

The authors outline a low-cost fabrication method that avoids photolithography and transfer printing. The process starts with etching one side of a Lotus NXT glass substrate with hydrofluoric acid (HF) to a thickness of 50 μm. Next, blind holes with a diameter and depth of roughly 40 μm are created on the etched side using laser ablation. A nanocrystalline diamond (NCD) film, approximately 175 nm thick, is then grown on the opposite side of the substrate. A final HF etching step, thinning the substrate to about 25 μm, creates through glass vias (TGVs) sealed by the suspended NCD film.

The authors conducted various tests to refine each stage of the fabrication process. They studied the impact of HF concentration and etching time on etch depth and surface roughness. They optimized laser ablation parameters to minimize crack formation while achieving desired blind hole dimensions. Finally, they investigated the properties of the grown NCD film, including its crystallinity, thickness, and stress.

The resulting NCD-glass platform is highly transparent and can withstand pressures of at least 300 kPa. The authors suggest that further improvements in TGV smoothness could be achieved by employing alternative laser ablation techniques or laser activation of the glass. They also note that the platform's thermal properties can be fine-tuned by selecting glasses with specific coefficients of thermal expansion, enabling the development of devices for high-temperature applications.

Origin: https://www.sciencedirect.com/science/article/pii/S0925963519304650