Method for making electrical contacts

The method of forming a highly conductive electrical contact to a silicon semiconductor region of an integrated circuits device comprising:

• providing an opening to said semiconductor region through an insulating layer;
• sputter depositing in said opening a thin first layer of aluminium having a first grain size;
• sputter depositing in said opening a second layer of aluminium having a second and substantially different grain size from the said thin first layer of aluminium;
• sputter depositing in said opening a third layer of aluminium having a substantially identical grain size to that of the said thin first layer of aluminium and continuing the depositing until the said opening is filled and the said electrical contact to semiconductor region is completed;
• wherein said first layer is greater in thickness than about 500 and less than about 1500 Angstroms and the second layer is between about 500 to 2500 Angstroms in thickness, and the first grain size is between about 1.5 to 2.0 micrometers, said second grain size is between about 0.5 to 1.0 micrometers and the grain size of said third layer is between about 1.5 to 2.0 micrometers;
• and subjecting the resulting structure to temperature cycling of greater than about 300.degree. C. whereby any formed silicon nodules are either preferentially formed at the boundary of the said thin first layer of aluminium and said second layer of aluminium or the boundary of the said second layer of aluminium and the third layer of aluminium.