Summary of the technology
The new diamond thermistors can be used for temperature measurements in harsh environments such as aggressive chemicals at high temperature or in biological media due to their inertness. Furthermore, the sintered ceramic substrate guarantees superior adhesion and resistance to fracture under high mechanical loads. The fabricated temperature sensitive diamond surface comprises well adhered ohmic contacts deposited on the backside of the dielectric ceramic substrate. This configuration prevents interaction between the temperature sensitive surface and the surrounding environment which is essential for biochemical devices applications.
Furthermore, the planar geometry of the disclosed thermistor maximizes the contact region between the temperature sensitive surface and any solid flat surface on which it is placed. In this way, improved response times are obtained comparing to traditional round shaped thermistors.
Description of the technology
The present invention relates to the fabrication process of new planar diamond film NTC (Negative Temperature Coefficient) thermistors on sintered ceramic Si3N4 substrates. These devices comprise a temperature sensitive diamond surface on one of the substrate surfaces and metal carbide ohmic contacts on the other surface.
The disclosed process comprises the steps: substrate preparation; semiconducting CVD diamond growth using the hot filament chemical vapor deposition (HFCVD) technique on a dielectric ceramic substrate; metallization of the doped diamond layer by direct metal vaporization and subsequent carburization using the HFCVD reactor; mechanical polishing of two opposite lateral surfaces of the coated ceramic substrate; non-doped diamond or ceramic layer deposition on the semiconducting diamond layer. The disclosed process creates a diamond/WC interlayer that guarantees an ohmic contact and superior adhesion between the semiconducting diamond layer and the metal-like WC layer.
Main advantages of its use
- improved response times are obtained comparing to traditional round shaped thermistors.
- maximization of the contact region between the temperature sensitive surface and any solid flat surface on which it is placed
- prevention of the interaction between the temperature sensitive surface and the surrounding environment
- superior adhesion and resistance to fracture under high mechanical loads
- The planar diamond thermistors disclosed in this invention are particularly applied but not limited to temperature measurements in combustion and jet engines for the automobile and aerospace industry, respectively; lasers, fuel cells and in biological and aggressive chemical environments.