Abstract of the Disclosure

An IC chip having a Zener diode with a subsurface breakdown junction to assure stable operation. The diode is formed by a triple diffusion process compatible with conventional bipolar processing. A deep p⁺⁺ diffusion first is applied, reaching through the epitaxial region to the buried n⁺ layer; next, a shallow p⁺ diffussion is formed over the deep p⁺⁺ diffusion and extending laterally beyond that diffusion; finally, a shallow n⁺ diffusion is applied over the p diffusions, to form a subsurface breakdown junction therewith . The topology of the mask windows is selected to provide concentration profiles which insure that the breakdown occurs at the subsurface junction, and that other desirable diode characteristics are achieved

• a cross-section view of a configuration of the three mask windows used to control the diffusion pattern for a diode in accordance with this invention.

 Citations [54]:
  
3,378,915  04/1968  Zenner
3,881,179  04/1975  Howard