HF vapor etching machine

• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 527538686

The fabrication of nanostructures plays a central role in the investigation of novel quantum technologies, especially in the realization of systems for quantum information processing and quantum sensors. In this context, it is often necessary to remove silicon dioxide and/or silicon nitride from samples without damaging other structures (e.g., made of silicon, gold, copper, silicon carbide, or silicon nitride). This can be achieved by chemical etching in hydrofluoric acid (HF). However, the use of liquid HF has significant disadvantages: On the one hand, the selectivity towards frequently used sample materials is low and cannot be adjusted. On the other hand, forces due to surface tension occur during removal of the sample from the acid and during subsequent drying, which often destroy larger nanostructures and thus make their fabrication impossible. These two crucial disadvantages can be avoided if HF vapor is used instead of liquid acid. In the porposed device, HF is not only vaporized in a controlled manner, but in addition, precise control of the etch rate and selectivity over other sample materials is achieved by precisely controlling the temperature, pressure and composition of the process gases. In addition, there are other advantages: The risk of sample contamination from suspended particles in solution is reduced, which significantly improves the yield for larger nanostructures. In addition, safety is increased because handling liquid HF acid and the significant health risks associated with it are avoided. Finally, an oxide-free surface termination with hydrogen atoms remains on silicon samples for several minutes, which is required for further process steps (e.g. ALD, CVD, MBE). In summary, the use of an RF vapor etching device, such as the one targeted by this proposal, will provide significant advantages in the fabrication of nanostructured quantum systems and materials. For this reason, corresponding devices are currently facing a high international demand. Purchasing of a corresponding machine would ensure that the Garching campus remains internationally competitive in the production of complex nanostructures.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: HF-Dampfätzgerät
• Instrumentation Group: 8330 Vakuumbedampfungsanlagen und -präparieranlagen für Elektronenmikroskopie
• Applicant Institution: Technische Universität München (TUM)
• Leader: Professor Dr. Andreas Reiserer