A new etching technology developed at the U.S. Department of Energy’s (DOE) Argonne National Laboratory 
Molecular layer etching could open new avenues for nanoscale device design. Source: Matthias J. Young et al.promises to advance semiconductor design and manufacturing by enabling the precise addition and removal of thin layers in multistep fabrication processes.
Molecular layer etching facilitates removal of metal-organic thin films deposited by molecular layer deposition. Microscopic architectures are synthesized by exposing thin films, several nanometers or micrometers thick, to pulses of gas inside a vacuum chamber. The film is subjected to alternating exposures to two gases until sufficient layers are removed to achieve a desired thickness.
The researchers tested the process with sequential exposures of alucone films to lithium organic salt and trimethylaluminum precursors to produce self-limiting etching behavior. The lithium-based gas induced lithium to adhere to the film’s surface and disrupt the chemical bonding in the material. The second as exposure removed the layer of film containing lithium.
The halogen-free etching process removed 0.4 nm/cycle of alucone at 160° C and up to 3.6 nm/cycle of alucone at 266° C in ex situ etching experiments on silicon wafers. The technology is expected to provide a new microelectronics fabrication pathway for the control of material geometries at the nanoscale.
