Selective etching of several hard-to-etch materials is achieved by cyclic repetition of conversion into volatile organometallics followed by volatilization. A feature of this etching technology is the processes of adding volatility to these materials by converting the surface of the materials into intermediatory generated organometallics with thermal stability; one key point is stabilizing materials for the organometallics, and the other is a reaction pathway via inherently stable organometallics. In layers of Co metal, one hard-to-etch material, a specific oxidation state of Co in the Co oxidizing first step avoids the reaction pathways that generate a mixture of multiple organo-cobalt complexes in the following step. For La2O3, another hard-to-etch material, an organo-lanthanum complex generated in the ligand adsorbing first step is immediately stabilized by a stabilizer. The surface-modified layer composed of the resultant stabilized organo-lanthanum complex prevents the ligand species from diffusing deeply and from increasing the modified layer thickness. The following step, in both cases, is rapid thermal annealing by infrared (IR) irradiation to remove the surface modified layer without decomposition. The etched amount increases as the number of cycle repetitions increases with high selectivity.
A selective, rapid thermal-cyclic atomic-level etching (ALE) of tungsten is developed. The first step of this process is exposing the surface of tungsten with hydrofluorocarbon plasma at −22°C to form a tungsten fluoride-based surface modified layer on the tungsten surface. The second step is rapid thermal annealing with infrared (IR) irradiation to remove the surface modified layer. Tungsten 4f peaks and a fluorine 1s peak, which were assigned to tungsten fluoride, were observed by in-situ x-ray photoelectron spectroscopy immediately after plasma exposure. The peaks that originated from tungsten fluoride disappeared after the samples were annealed. Cyclic etching tests were carried out by repeating plasma exposure and IR irradiation with a 300-mm ALE tool. Films of tungsten, TiN, and SiO2 were used as sample materials. The amount of etched tungsten increased as the number of cycle repetitions increased. The etched amount per cycle for tungsten was 0.8 nm. In comparison, etching of TiN and SiO2 was not detected. Conformal etching profiles of patterned samples after 60 cycles were obtained. Furthermore, the etched amount per cycle showed saturation behavior with regard to plasma exposure time. Selective, rapid thermal cyclic ALE of tungsten was thus successfully demonstrated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.