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To utilize ALD near perfect step coverage in extreme dimensions


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									ALD of Metals, Metal Carbides and Nitrides

Wei-Min Li*, Eva Tois, Raija Matero, Robert Huggare, Suvi Haukka, and Marko Tuominen

ASM Microchemistry Ltd., Väinö Auerin katu 12 A, 00560 Helsinki, Finland

Atomic layer deposition (ALD) of thin films of metals and their carbides or nitrides are widely studied
for numerous applications including diffusion barrier, adhesion layer, metal electrode for logic and
memory applications, as well as for ware resistant MEM devices. It has been challenging to deposit
ultra-thin, continuous and yet low resistivity metal materials by ALD without applying external energy,
such as plasma, while fulfilling the application requirements such as sufficient low process temperature,
near perfect step coverage in extreme dimensions, and without damaging the underlying layers.

Recently we have developed a novel ALD chemistry for growing metals and their carbides or nitrides
thin film materials. These deposition processes make use of metal halides and silicon or aluminum
compounds which simultaneously remove the halide ligands and reduce the metal. For example, highly
robust deposition processes have been developed for TaC, TaCN, as well as for metallic Ta. The as-
deposited Ta based thin films have bulk resistivity of approximately 500 cm, the lowest value that
has been obtained via thermal ALD process until now. Upon annealing up to 1050 °C, a further
decrease in the bulk resistivity can be achieved, while the films still maintain their integrity. This novel
ALD chemistry allows selection of a wide range of metal and non-metal precursors, and opens up a
new way to deposit a large variety of metals and metal carbides or nitrides with different chemical and
physical properties.

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