Atomic Layer Deposition of Transition Metal Thin Films

Wayne State University
posted on 01/16/2012

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Microelectronics device dimensions are scheduled to reach 22 nm by 2012, and existing deposition processes will soon not be able to provide the required level of thickness control and conformality, especially in high aspect ratio features.  The atomic layer deposition (ALD) film growth method is well-suited for nanoscale film growth, since it affords inherently conformal coverage and subnanometer film thickness control, due to its self-limited growth mechanism.  Currently there are few atomic layer deposition thin film growth processes for transition metal thin films.  Copper is used as the wiring material in microelectronics devices, and nickel, cobalt, manganese, and other transition metals have many uses in microelectronics and other devices.   The best transition metal ALD processes reported to date either occur at temperatures that are too high or incorporate undesired elements.  A central problem is that many precursors have low reactivity toward common reducing agents, which necessitates high growth temperatures.  Transition metal films should be deposited ideally at ≤100 °C to afford the smallest surface roughnesses, promote facile nucleation, and give continuous films, even at thicknesses of a few nanometers.

Wayne State University researchers have circumvented precursor reactivity problems by developing a three-step deposition scheme that entails a transition metal precursor, an organic acid, and a reducing agent.  This novel process can produce high purity, low resistivity copper films at 100 °C, which is a significant breakthrough in transition metal ALD processes.

Commercial Applications:

·         Transition metal thin films in microelectronics and other devices

Technology Advantages:

·         Our new ALD process can afford high purity, low resistivity copper films at 100 °C

Patent Status:

Patent pending