Grazing incidence ion beams for reducing LER

As semiconductor feature sizes continue to decrease, the phenomena of line edge roughness (LER) becomes more disruptive in chip manufacturing. While many efforts are underway to decrease LER from the photoresist, post-develop smoothing techniques may be required to continue shrinking chip features economically. This paper reports on one such method employing the use of an ion beam at grazing incidence along the features. This method smooths relatively long spatial length LER, a potential advantage over other smoothing techniques that focus on just small-scale LER. LER reduction numbers using Ne and Ar beams are reported at both short and long spatial wavelength. Variables include beam energy, length of time and angular dependence. LER measurements are taken using Hitachi image analysis software on top-down analytical SEM measurements. Line profile data are taken from cross sectional SEM photographs. Tests have achieved a reduction in LER from 9.8±0.67 nm to 5.5±0.86 nm for 45 nm 1:1 lines using an Ar beam at 500 eV for 6 s at an 85° angle of incidence. A reduction from 10.1±1.07 nm to 6±1.02 nm was shown using an Ar beam at 1000 eV for 4 s at a 60° angle of incidence.