As semiconductor feature sizes and pitches shrink to ever-decreasing dimensions, Line Edge Roughness (LER) becomes
and increasing important problem. The LER is transferred from the photoresist to the substrate through the subsequent
processing steps, causing variations in, eg, gate length. This leads to mismatch in device performance and leakage.
Thus, an efficient and cost effective way to reduce the LER in the semiconductor photoresist is needed in order to keep
the imperfections from affecting processing steps further down the line. At the CPMI a new technique to reduce LER
from patterened photoresist has been developed in conjunction with INTEL. Results obtained using our technique
showed significant LER reduction from 6.9±0.47 nm to 3.9±0.61 nm for 45 nm lines and spaces. Recent results on 40
nm lines and spaces showed significant LER reduction from 5.9±0.50 nm to 4.1±0.63nm. LER reduction results on 40
nm lines and spaces reveal the fact that our technique is superior to other available techniques such as etching, vapor
smoothing, hardbake, ozonation and rinse.
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, postdevelop
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 85o 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 60o angle of