Hermetic fusion of diamond micro-components with silicon

Implantable devices which interact with neuronal systems and last for the lifetime of the recipient are an emerging field in medical research, diagnostics and therapeutics. These devices often contain sensitive micro-electronics ranging from passive radio-frequency identification tags to active sensors and stimulators. Therefore, such devices require robust and biocompatible packaging. There is a strong desire to reduce the size of such devices, enable wireless communication methods and protect these devices in the body for many decades. Diamond is a biopermanent material that provides the chemical inertness and mechanical stability to ensure long operational life of implanted devices and can also exhibit excellent optical and radiofrequency transparency. For some applications, the transparency of diamond is used to enable optical power and data communication with the encapsulated electronics. The final assembly of the device often requires the joining of diamond to diamond, and such joints are challenging to fabricate. Here we describe a new method of hermetically fusing diamond to diamond using a thin silicon interlayer as a braze material. The strong bond forms due to SiC formation at the interface of the materials. A 3.5 × 3.5 × 0.3 mm diamond box was formed from a thermal grade diamond base with a thin, transparent diamond lid. We show by helium leak detection and non-destructive optical methods, that the package is hermetically sealed to better than 2.2 × 10⁻⁹ cm³ atm/s of helium. The method is an industrially relevant route to forming long lived implantable diamond packages, in particular the incorporation of transparent diamond windows into the package to enable for optical power and data communication.