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Thermally Stable Low Au Content Ohmic Contact/Diffusion Barrier to N-Type GaAs

IP.com Disclosure Number: IPCOM000120778D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

La Tulipe, D: AUTHOR [+4]

Abstract

Disclosed is an ohmic contact to n-type GaAs with the following properties:

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Thermally Stable Low Au Content Ohmic Contact/Diffusion Barrier to
N-Type GaAs

      Disclosed is an ohmic contact to n-type GaAs with the
following properties:

      a) provides for a low contact resistance, RC   0.10-0.20 L-mm

      b) is thermally stable, RC is <0.35 L-mm after 20 hours at
400oC
      c) has a smooth surface morphology
      d) forms a shallow metal/GaAs junction (350 Ao deep)
      e) is uniform and non-spiking
      f) incorporates a diffusion barrier as part of the
         contact.

      The contact consists of a 4-layer structure plus a diffusion
barrier, shown in the figure.  The layered structure may be deposited
by a number of techniques, including vacuum evaporation and plasma
sputtering.  The contacts are formed by rapid thermal annealing.  M1
is a thin metal layer which disperses the native oxide present on the
surface prior to deposition and promotes a smoother surface
morphology.   It may consist of Ni, Pd, Co or Pt, for example. The
second layer is a thin layer of gold.  Its purpose is to create Ga
vacancies in the underlying GaAs substrate which are subsequently
occupied by group IV atoms, supplied from layer 3.  Group IV
elements, which act as electron donors when occupying the vacant Ga
sites, are Si and Ge.  M4 is a metal layer whose thickness is chosen
so as to react with layer 3 to create a high melting point germanide
or a silicide compound.  The topmost layer controls the contact sheet
res...