Method of inhibiting hillock formation in films and film thereby and

Abstract

In accordance with the disclosure, certain impurities, e.g., alloying additions, are introduced in thin metal film to negate the driving force or the effect of the driving force which causes the hillock formation. Such thin metallic films are usually fabricated on the substrates which have different thermal coefficients of expansion than the film itself, and during thermal cycling stresses can be introduced into the film. This stress may serve as a driving force for atom movement and, therefore, to the formation of hillocks. The vehicle by which the induced stress in a film effects the requisite atom movement is via defect movement, and when the force is compressive this gives rise to hillocks. In the practice of this disclosure, impurity additions introduced into a film affect hillock growth by their interaction with the defects which give rise to the requisite atom movement. Systematically selected impurity additions are introduced into a film during fabrication thereof which inhibit the defect movement in the class consisting of a migration of point defects, linear defects and planar defects wherein the linear defects are dislocations and the planar defects are grain boundaries. Usually, the addition of impurities into a metal film is termed alloying and the resultant film is termed an alloyed film. The alloying addition may be either soluble or insoluble in the film. This will determine the choice of possible modes of fabrication. When the alloy addition is soluble, it is included within the limits of solubility at the temperature at which it is introduced. When the alloy addition is insoluble, it is introduced during fabrication and quantity thereof may be significantly better than the quantity capable of being sustained were the alloying addition and the film to be in thermal equilibrium.