Test structures for hillock growth, via filling and for measuring the quality of thin films

A test structure for assessing the quality of thin aluminium films is described. An analysis of the relationship between grain structure and hillock growth in small exposed areas of thin films during high temperature processing shows that there is a relationship between hillock growth, grain size and grain boundary structure. The test structure consists of arrays of via holes of various sizes etched in a thin layer of SiO/sub 2/ deposited at low temperature onto the metal surface. After furnace annealing, the number of vias of each size which contain hillocks can be interpreted to obtain information on film quality.