Dis Continuities in Evaporated Aluminum Interconnections

Minute cracks have been observed in semiconductor device metallization at the edges of contact windows. The cracks are formed during deposition of the aluminum and not during subsequent processing, although subsequent processing can aggravate the effect. The cracking is shown to be caused by shadowing, aggravated in some instances by angle-of-incidence effects, and can be expected to occur with many different evaporation source geometries. The problem can be avoided by correct shaping of oxide steps or by reducing the height of the oxide step. The effectiveness of heating the substrate during evaporation in eliminating certain types of cracks is discussed.