Paper TF-MoM6
Atomic Layer Deposition for Passivation and Corrosion Protection of Metal Substrates

Monday, October 15, 2007, 9:40 am, Room 613/614

The unique features of Atomic Layer Deposition; capability to produce highly conformal pin-hole free films on complex structures and excellent adhesion to most surfaces, have been utilized mainly by the semiconductor industry. However, these properties are often highly appreciated by many other industries as well. As an example, silver industry has recently started using ALD to protect silver jewelry from tarnishing. Tarnishing is mostly caused by airborne sulfur compounds forming black silver sulfide on the surface of a silver object. In this application, the most important criteria are invisibility and anti-tarnish properties of the coating. A uniform 10nm thick aluminum oxide layer increases the tarnishing time by two orders of magnitude while being invisible to human eye. The same method can also be applied to other silver products as well as other metals, including copper and copper containing alloys. In addition to passivation of silver and copper based products, more demanding anti-corrosion coatings can be done on stainless steel and other common construction metal parts used in extreme conditions. Relatively low growth rate of ALD compared to other thin film techniques can be compensated with large batch size, since ALD is one of the easiest thin film processes to scale-up. ALD films can also often be much thinner compared to films prepared with other thin film techniques, for example if certain barrier properties are required. This is due to higher film uniformity and fewer pin holes in ALD films. Even though most work with ALD has been done on silicon and glass substrates, metal substrates offer many applications for ALD, since complex shaped parts are often made of metal. By careful selection of coating structure, it is possible to combine anti-corrosion coatings with other functions, including decorative and wear resistant functions.