AVS 65th International Symposium & Exhibition
    Advanced Ion Microscopy Focus Topic Thursday Sessions
       Session HI+AS-ThM

Paper HI+AS-ThM13
Helium and Neon Focused Ion Beam Hard Mask Lithography on Atomic Layer Deposition Films

Thursday, October 25, 2018, 12:00 pm, Room 203B

Session: Advanced Ion Microscopy & Surface Analysis
Presenter: Matthew Hunt, California Institute of Technology
Authors: M.S. Hunt, California Institute of Technology
J. Yang, University of Texas at Austin
S.A. Wood, California Institute of Technology
O.J. Painter, California Institute of Technology
Correspondent: Click to Email
A hard mask lithography technique has been developed wherein a helium or neon focused ion beam (FIB) is used to directly etch a pattern into a thin, atomic layer deposition (ALD) film before then transferring the pattern into the underlying material using a reactive ion etch (RIE). The technique takes advantage of small He-FIB and Ne-FIB probe sizes, capable of directly etching patterns with feature sizes on the order of 1s and 10s of nanometers, respectively, while sidestepping several negative consequences associated with direct etch, namely that low sputter rates prevent large-area patterning from being carried out efficiently, with straight sidewalls, and/or without inducing substrate swelling. An example of the technique is presented here in which (1) 4-10 nm of ALD aluminum-oxide is applied as the hard mask on a 60 nm thick film of aluminum, (2) a <10 pC/um Ne-FIB dose is used to pattern lines that barely etch through the hard mask, and (3) a Cl2/CH4/H2 RIE is used to etch the underlying aluminum in 10s of seconds. Neon FIB writing time is reduced by a factor of 20 or more compared to directly etching through the full 60 nm aluminum film. Nanowires as thin as 25 nm are produced with straight sidewalls on 70 nm pitch. This example is being utilized to make superconducting quantum circuit components, e.g. 4 mm long nanocoil inductors that fit into a (20x20) um2 area. The technique has potentially wide-ranging nanofabrication applications given its amenability to different ALD/substrate material sets and compatibility with both He- and Ne-FIB.