Ohmic Contacts For Small, Shallow Structure Devices
Original Publication Date: 1979-Sep-01
Included in the Prior Art Database: 2005-Feb-20
In the fabrication of a small, shallow emitter-base transistor by the ion implant and reactive ion etching (RIE) processes, the emitter surface is generally a few tens of nanometers below the surrounding dielectric Si interface due to the over-etching of the RIE (limit of the end-point detection capability). The lateral diffusion is relatively small due to the vertical sidewall and the ion implantation. Thus, when the metal film, such as Pt, Pd or Cr, is deposited on top of Si surface and a layer of the Si is consumed during the metal-semiconductor contact formation, there results a very thin area of emitter-base junction and nonuniform injection. Also, in some instances there is shorting through the junction, and resulting deterioration of device performance.