A metal-insulator-silicon junction seal

Most semiconductor devices today have a costly vacuum-tight encapsulation that provides a microenvironment for high reliability and electrical connections to the circuit in which it is used. A junction seal consisting of a metal-insulator-silicon (MIS) system of materials has been developed to replace the vacuum-tight encapsulation. The MIS junction seal, consisting of platinum silicide-titanium-platinum-gold contacts and a Silicon nitride overcoat, provides the necessary encapsulation for high reliability. Electrical and mechanical connections are provided by gold beam-deads. During fabrication, the contact windows are opened in the deposited silicon nitride layer either by etching with boiling phosphoric acid using SiO2as a mask or by anodically converting the silicon nitride in the windows to a soluble oxide. The multilayer contact is then applied to complete the junction seal. The initial characteristics of sealed-junction transistors fabricated by the above methods were similar to those of the unsealed transistors. The reliability of the sealed-junction transistors determined by accelerated aging after an intentional sodium contaminafion of 10¹⁷atoms/cm²surpassed that of the standard silicon planar transistors sealed in a vacuum-tight enclosure.