The Challenges and Opportunities of Atomic Layer Etching

Abstract

The introduction of new and functionally improved materials into silicon based integrated circuits is a major driver to enable the continued down-scaling of circuit density and performance enhancement in analog, logic, and memory devices. Many new materials, such as multiferroics, magnetic materials and phase change materials, are much harder to pattern, thereby posing significant challenges to the design and selection of plasma etching chemistry. While ion milling is effective in patterning some of these functionally improved materials, such as complex magnetic material stacks used in magnetic tunnel junctions, it limits the scalability and integration of devices. These challenges point to the growing needs of identifying and developing viable etch chemicals and processes that are more effective in patterning complex materials and material systems.

In this talk, a generalized approach based on combined thermodynamic assessment and kinetic validation is presented to identify and validate the efficacy of various plasma chemistries. Specifically, potential reactions between the dominant vapor phase/condensed species at the surface are considered at various temperatures and reactant partial pressures. The volatility of etch product was determined to aid the selection of viable etch chemistry leading to improved etch rate of reactive ion etching process. Based on the thermodynamic screening, viable chemistries are tested experimentally to corroborate the theoretical prediction. Some of the above mentioned material systems such as magnetic materials used in magnetic tunnel junctions are used as examples to demonstrate the broad applicability of this approach.

Bio

Jane P. Chang received her B.S. degree from National Taiwan University, and M.S. and Ph.D. degrees from Massachusetts Institute of Technology. She joined Bell Labs, Lucent Technology, as a postdoctoral member of technical staff in 1998. In 1999, she joined UCLA in the Department of Chemical and Biomolecular Engineering. In 2000, she was appointed the William F. Seyer Chair in Materials Electrochemistry.

Chang’s research focuses on the synthesis and chemical processing of novel and multifunctional materials, and an atomistic understanding of their interfaces with semiconductors. Specifically, Chang’s research group studies the synthesis of metal oxide thin films and nanostructures with tailored electronic, chemical, and thermal properties by novel atomic layer controlled thermal, radical, and plasma enhanced deposition techniques and hydrothermal processing, develops highly selective plasma etching processes for patterning nano-metered thin films, designs and develops micro chemical sensors and engineers the multi-component oxide materials needed in various energy storage devices. In addition, her research group integrates the experimental and first-principle theoretical approaches to elucidate the fundamental physical and chemical origins of superior material and electronic properties.

Chang has published more than 80 scientific papers, in addition to a book, a book chapter and 4 U.S. patents. Her work has also been recognized by several awards, including Professor and Teacher of the Year, the NSF Early Career Award, the Coburn and Winters Award from the American Vacuum Society, the Office of Naval Research Young Investigator Award, the Chancellor’s Career Development Award, the AVS Peter Mark Award, and the TRW Excellence in Teaching Award.