Polycrystalline diamond thin film packaging technology for wireless integrated microsystems

The paper presents a polycrystalline diamond (poly-C) thin film packaging technology that can be integrated into post-MEMS fabrication processes. The test package is fabricated using a 3-mask process. After a 0.5-μm-thick boron-doped poly-C film is deposited and patterned for feedthroughs, a 4-μm-thick poly-C film is deposited on 4.2-μm-thick sacrificial PECVD oxide. The poly-C film is patterned to provide fluidic access ports for releasing the package. The fluidic access ports are sealed with additional 4-μm poly-C deposition. Boron-doped poly-C is studied as a material for feedthroughs, which is embedded in the undoped insulating poly-C package to improve the sealing of the feedthrough. The poly-C feedthroughs are doped in-situ using tri-methyl-boron diluted in hydrogen (0.098%). This doping technique can lead to an interconnect resistivity as low as 0.003 Ω-cm. However, the resistivity of the poly-C feedthroughs film in the test package was 0.02 Ω-cm.