Characteristics of aluminum-titanium electrical contacts on silicon

An aluminum-titanium metallization scheme for use in silicon integrated circuits is described. This metallization can produce high-conductance electrical contacts with negligible dissolutions of silicon. The desirable contact is lost, however, if a TiAl3 reaction product is allowed to consume the entire Ti layer. The TiAl3 forms during the postmetallization heat treatment used to stabilize the electrical characteristics of the contact. The Ti layer is found to be consumed in this reaction at a rate proportional to t1/2, where the rate constant is determined to be d=d0 exp(−Ea/kT), where d0 ≈ 0.15 cm2/sec and Ea ≈ 1.85 eV. This rate constant can be used to determine the thickness of titanium layer necessary to produce the desirable electrical contact.