Self-aligned Schottky diode structure and method of fabrication

Abstract

Abstract A Schottky diode structure and self-aligned fabrication method wherein the cathode or ohmic contact is disposed in the center of the anode or Schottky contact and is isolated therefrom by an overlapping layer of insulation. This structure has a reduced area size; it allows the use of only one metal line for both anode contacts and affords a marked advantage of device density. The structure includes a substrate having an n+ sub-diffusion therein, an epitaxial layer over the sub-diffusion which serves as the cathode electrode of the Schottky barrier device, and recessed oxide regions on the substrate for isolation. A heavily doped n+ polysilicon layer is disposed over the epitaxial layer and is used as a source of impurities for the diffusion which makes contact to the Schottky barrier diode. The structure is masked and exposed by conventional photolithographic or electron-beam techniques and is etched down to the epitaxial layer leaving a strip of n+ polysilicon. This strip is employed to connect to the cathode of the Schottky barrier diode and to interconnect it to other devices. A silicon dioxide layer is then grown over the surface of the epitaxial layer and polysilicon and/or deposited over the whole surface by chemical vapor deposition. A reactive-ion-etching step is then performed to remove the oxide layer back to the surface of the epitaxial layer. This leaves a silicon dioxide layer remaining on the top and sides of the polysilicon strip. An n+ region is out-diffused from highly doped region into the epitaxial layer and Schottky barrier diode anode material, for example palladium silicide, is deposited as a film layer of metallic palladium, then is reacted with silicon at high temperature, and the unreacted metal over the silicon dioxide is selectively etched away leaving behind the reacted palladium silicide anode regions. Finally, a metal layer is deposited for contacting the Schottky barrier diode anode and is patterned for interconnection to other devices.

Inventors

• 👤 George C. Feth
• 👤 Siegfried K. Wiedmann

Bibliographic Details