Hillock-free aluminum wiring layer and method of forming the same

A method for forming a hillock-free wiring layer, wherein said wiring layer is formed on a substrate and comprises at least two pure aluminum (Al) layers, the method comprising the steps of:

• under a first film formation pressure and a first film formation making power, forming a first pure Al layer on the substrate;
• and
• under a second film formation pressure and a second film formation making power, forming a second pure Al layer on said first pure Al layer;
• and
• wherein said second pure Al layer has a plurality of second Al crystal particles larger substantially in size than said first Al crystal particles of said first pure Al layer, and said second Al crystal particles of said second pure Al layer are more densely distributed than said first Al crystal particles of said first pure Al layer.

A method for forming a hillock-free wiring layer including N pure aluminum layers formed on a substrate, wherein said N pure aluminum layers are deposited on the substrate and N is an integer greater than two, the method comprising the steps of:

• (a) under a first film formation pressure and a first film formation making power, forming a first pure Al layer on the substrate;
• (b) setting i to be two;
• (c) under an i-th film formation pressure and an i-th film formation making power, forming an i-th pure Al layer on an (i-1)-th pure Al layer;
• and
• (d) incrementing i by one, and repeating said steps (c) and (d) until i is greater than N;
• wherein the j-th pure Al layer has a plurality of j-th Al crystal particles, where j is an integer less than N and greater than zero, (j+1)-th Al crystal particles are substantially larger in size than j-th Al crystal particles, said (j+1)-th Al crystal particles of said (j+1)-th pure Al layer are more densely distributed than said j-th Al crystal particles of said j-th pure Al layer, and said j-th pure Al layer has an electric resistance larger than that of said (j+1)-th pure Al layer.

A wiring layer comprising at least two layers formed on a substrate, wherein said at least two layers are substantially made of aluminum (Al), said at least two layers comprising:

• a first layer formed on the substrate and substantially having a plurality of first crystal particles;
• and
• a second layer formed on said first layer and substantially having a plurality of second crystal particles;
• wherein said second crystal particles are substantially larger in size than said first crystal particles, and said second crystal particles of said second layer are more densely distributed than said first crystal particles of said first layer;
• whereby said at least two layers of the wiring layer are capable of preventing hillocks.