Grazing incidence broad ion beams for reducing line-edge roughness

Abstract

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-developed smoothing techniques may be required to continue shrinking chip features economically. This paper reports on one such method employing the use of a broad 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 molecular-scale LER. LER reduction numbers using Ne and Ar beams are reported at both short and long spatial wavelengths. Variables include beam energy, length of time and angular dependence. LER measurements are taken using the Hitachi image-analysis software on top-down analytical scanning electron microscope (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 critical dimensions 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.

Methodology for evaluating pattern transfer completeness in inkjet printing with irregular edges

“…Although numerous inspection tools can automatically evaluate W, S, and D for lithography and specific procedures can quantify line edge roughness (LER) [16,17], these methodologies only support LER evaluation for lithographygenerated straight lines. To our best knowledge, no evaluation for PTC with patterns other than lines generated by either lithography or lithography-free techniques has been realized.…”

Understanding and controlling the structure of thin polymer films used in photolithography

“…The X-Y plane corresponds to the resist surface, the Z-axis is along the resist depth without 'shape control' and 'shape and dose control' methods, (II) with 'shape control' method, and (III) with 'shape and dose control' method for PHOST film on Si. Resist thickness: 300 nm, beam energy: 50 keV, beam diameter: 3 nm, and exposing interval: 1 nm, feature size: 25 [42].The samples were processed with a 500 eV Ne beam at an 85º angle of incidence. For both the processed and unprocessed samples, LWR increases with wavelength, though the values for unprocessed samples are higher than the processed samples.…”

“…Ruzic et al focused on improving long spatial-length LER rather than focusing on molecular-scale LER [42]. They used broad ion beams at grazing incidence along the features to heal the LER after lithography using Ne and Ar beams with beam energy, length of time and angular dependence as…”

“…Fourier graph of the LWR up to and including the wavelength of 980 nm for the unprocessed and processed samples [42].The samples were processed with a 500 eV Ne beam at an 85º angle of incidence. For both the processed and unprocessed samples, LWR increases with wavelength, though the values for unprocessed samples are higher than the processed samples.…”

“…Since photolithography involves a number of steps, and as discussed in earlier sections of this chapter, LER depends on a number of variables. In addition to optimize those variables, few post-photolithographic treatment such as resist reflow processing [9], or applying broad ion beams at grazing incidence along the features [42]. Despite this, further improvements and optimizations are still needed to achieve the ITRS goals of LER < 10% of the critical dimension.…”