Metallization System for Electromigration Improvement
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2005-Feb-13
Improvement in Al-Cu lifetime can be achieved by reacting Al with a transition metal (Hf, Ti, Ta, Zr, Cr, etc.) to form a diffusion barrier for cracks (voids). This process is described in U. S. Patents 4,017,890 and 4,141,020. A key issue of these patents was that the intermetallic reaction product was conductive and prevented voids from penetrating the stripe (diffusion barrier). If the transition metal were oxidized (nonconducting), then the compound did not form and no lifetime improvement was observed (U. S. Patent 4,154,874). Thus, by violating the requirement that the layer remain conductive, lifetime improvement was minimal (in some cases the lifetime was less than the control; see J. Appl. Physics 49 4085 (1978), Table III).