Wafer-Level Manufacturing of MEMS H₂ Sensing Chips Based on Pd Nanoparticles Modified SnO₂ Film Patterns

In this manuscript, a simple method combining atomic layer deposition and magnetron sputtering is developed to fabricate high-performance Pd/SnO₂ film patterns applied for micro-electro-mechanical systems (MEMS) H₂ sensing chips. SnO₂ film is first accurately deposited in the central areas of MEMS micro hotplate arrays by a mask-assistant method, leading the patterns with wafer-level high consistency in thickness. The grain size and density of Pd nanoparticles modified on the surface of the SnO₂ film are further regulated to obtain an optimized sensing performance. The resulting MEMS H₂ sensing chips show a wide detection range from 0.5 to 500 ppm, high resolution, and good repeatability. Based on the experiments and density functional theory calculations, a sensing enhancement mechanism is also proposed: a certain amount of Pd nanoparticles modified on the SnO₂ surface could bring stronger H₂ adsorption followed by dissociation, diffusion, and reaction with surface adsorbed oxygen species. Obviously, the method provided here is quite simple and effective for the manufacturing of MEMS H₂ sensing chips with high consistency and optimized performance, which may also find broad applications in other MEMS chip technologies.