A photoresist-ashing process has been developed which, when used in conjunction with conventional g-line optical lithography, permits the controlled definition of deep-submicrometer features. The ultra-fine lines were obtained by calibrated ashing of the lithographically defined features in oxygen plasma. The technique has been successfully employed to fabricate MOSFET's with effective channel length as small as 0.15 pm that show excellent characteristics. An NMOS ring oscillator with 0.2-pm devices has been fabricated with a room-temperature propagation delay of 22 pslstage which is believed to be the fastest value obtained for a MOS technology. Studies indicate that the thinning is both reproducible and uniform so that it should be usable in circuit as well as device fabrication. Since most polymer-based resist materials are etchable with an oxygen plasma, the basic technique could be extended to supplement other lithographic processes, including e-beam and X-ray processes, for fabricating both silicon and nonsilicon devices and circuits.
Effects of growth temperature and V/III ratio on surface morphology, crystallinity and residual impurities of MOCVD-grown GaAs-on-Si have been studied. The effects are different from those on MOCVD-grown GaAs-on-GaAs. The difference arises from the heteroepitaxial problems. High silicon concentrations are found in all the GaAs-on-Si, and the electrical activation of silicon as a donor reaches 100% for higher growth temperatures. Crystallinity improves but surface morphology degrades with increasing growth temperature. The trade-off between crystallinity and surface morphology has been eliminated by the three-step growth process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.