Gerald G Lopez

Automated Geometry assisted PEC for electron beam direct write nanolithography

Nanoscale geometry assisted proximity effect correction (NanoPEC) is demonstrated to improve PEC for nanoscale structures over standard PEC, in terms of feature sharpness for sub-100 nm structures. The method was implemented onto an existing commercially available PEC software. Plasmonic arrays of crosses were fabricated using regular PEC and NanoPEC, and optical absorbance was measured. Results confirm that the improved sharpness of the structures leads to increased sharpness in the optical absorbance spectrum features. We also demonstrated that this method of PEC is applicable to arbitrary shaped structures beyond crosses.

Shape positional accuracy optimization via writing order correction

Shape positional accuracy is a ubiquitous challenge when writing critical features using electron beam (e-beam) lithography. Positional accuracy can be particularly important when patterning for dense pattern arrays often found in plasmonic device structures. These arrays contain structures critically placed within a few tens or hundreds of nanometers apart from one another, whereby poor positional accuracy on the same order of magnitude would impact overall device performance. The sources of positional accuracy are varied on an e-beam lithography system and can include, but are not limited to beam drift, surface charging, environmental noise, and temperature to name a few. This work demonstrates the impact of shape writing order on sub-100 nm features to tolerate these potential sources of shape positional errors. The shape positional accuracy of both proximity effect corrected (PEC) and non-PEC array patterns are studied using a 20 MHz fixed clock 50 keV Gaussian spot electron beam lithography system ex...

Isofocal dose based proximity effect correction tolerance to the effective process blur

The isofocal dose in electron beam lithography (EBL) is defined as the dose that results in the same feature size independent of the effective blur (blureff), which is the result of a combination of resist processing, spot size, beam focus, forward scattering, etc., that contributes to the final resist image. In other words, as blureff changes the same feature size is still obtained while using the same dose. This phenomenon is clearly demonstrated in EBL simulation when varying the blureff. In this work, the authors identify the isofocal dose for a given resist process consisting of 200 nm of ZEP520A from ZEON Chemicals atop a Si substrate using 300 nm line-space tower patterns with pattern densities ranging from 0% to 100% on an Elionix ELS-7500EX 50 keV EBL tool with a fixed 20 MHz clock at 200 pA with a 30 μm final aperture and a 20 nm beam step size. In this experiment, the dominant component of the blureff is the electron beam focus. By comparing line width measurements from tower patterns exposed w...