Electron beam lithography with feedback using in situ self-developed resist

Abstract

Due to the lack of feedback, conventional electron beam lithography (EBL) is a ‘blind’ open-loop process where the exposed pattern is examined only after ex situ resist development, which is too late for any improvement. Here, we report that self-developing nitrocellulose resist, for which the pattern shows up right after exposure without ex situ development, can be used as in situ feedback on the e-beam distortion and enlargement. We first exposed identical test pattern in nitrocellulose at different locations within the writing field; then, we examined in situ at high magnification the exposed patterns and adjusted the beam (notably working distance) accordingly. The process was repeated until we achieved a relatively uniform shape/size distribution of the exposed pattern across the entire writing field. Once the beam was optimized using nitrocellulose resist, under the same optimal condition, we exposed the common resist PMMA. We achieved approximately 80-nm resolution across the entire writing field of 1 mm × 1 mm, as compared to 210 nm without the beam optimization process.

Electron Beam Lithography on Irregular Surfaces Using an Evaporated Resist

“…Therefore, a trade-off between exposure time and achievable resolution on the fiber side surface has to be made. For example, with 37 μm out of focus (fiber radius is 50 μm) and 30 μm aperture size, one can achieve 80 nm resolution on a flat wafer . Moreover, in addition to beam enlargement (here to 80 nm diameter) due to out of focus, the beam spot size on the side surface is further elongated by 1/cos θ (θ is the local incident angle) along the vertical direction.…”

Stitching error reduction in electron beam lithography with in-situ feedback using self-developing resist

“…1 Figure 3(b) shows an error of 82 nm overlap along the horizontal direction that indicates too high a zoom value, and an error of $150 nm shift along the vertical direction that indicates a counter clockwise rotation error. We achieved an average stitching error (¼sqrt[(Dx) 2 þ(Dy) 2 ]) of 543 nm with a standard deviation of 334 nm.…”

Recent advances in techniques for fabrication and characterization of nanogap biosensors: A review

“…The process has several advantages, but it also have some disadvantages because the e‐beam lithographic technique takes a long time to expose an entire substrate 37 . A long exposure time leaves the user vulnerable to beam drift 111 . Moreover, other advantages such as turnaround time, the process in case of reworking, or redesign is increased unnecessarily if the pattern is not being changed.…”

“…37 A long exposure time leaves the user vulnerable to beam drift. 111 Moreover, other advantages such as turnaround time, the process in case of reworking, or redesign is increased unnecessarily if the pattern is not being changed. Although the technique produces a good surface profile especially for nanowire and gaps, the techniques also frequently introduce some defects in fabricated structures.…”