Near neighbor averaging: A technique for improving image uniformity in aperture array lithography

Abstract

Ion beam aperture array lithography was developed to rapidly form large arrays of periodic patterns whose shape is defined at the printing step. This is accomplished with a massive array of ion beamlets formed by exposing a stencil mask with a dense array of openings to a broad ion beam; these can be moved across the wafer surface to write the shape of the unit element with each beamlet. In this work, the authors demonstrate that the uniformity of the aperture array mask image can be significantly improved by averaging the exposure with images formed by the neighboring apertures. This reduces the tolerances for patterns in the stencil mask and allows for the correction of random defects that may occur during the mask fabrication process. To achieve this, each aperture image is formed as the sum of the images of itself and its neighbors. They demonstrate, through modeling and experiment, that this process can form images where the standard deviation of the openings has been reduced by a factor of 3 when averaging the exposure over nine neighboring apertures. They show that the size distribution scales inversely with the square root of the number of near neighbor exposures.

Radiation damage in polymer films from grazing‐incidence X‐ray scattering measurements

“…A more detailed discussion of ABL exposure schemes can be found elsewhere . Irradiation doses were varied in the range of 1.6–20 mJ cm −2 .…”

“…A more detailed discussion of ABL exposure schemes can be found elsewhere. 29,30 Irradiation doses were varied in the range of 1.6-20 mJ cm 22 . PS patterns were developed within an hour of exposure by immersing the sample in toluene for 20 s at room temperature, and then immediately dried under a nitrogen stream.…”

High-Resolution, High-Throughput, Positive-Tone Patterning of Poly(ethylene glycol) by Helium Beam Exposure through Stencil Masks

“…In this source, a plasma is ignited at low pressure when electrons are trapped along long oscillatory paths through a saddle-point in the electric potential distribution, and ions escape through a small aperture machined into one end of the source. As the ions escape, a fraction is neutralized through charge-exchange collisions with the neutral helium gas ambient and a beam of mixed atoms and ions drifts along the length of a vacuum beam line to an exposure chamber, located about 1.5 meters from the source [37]. To form patterns, a stencil mask is held in proximity to the wafer by a fixture and the wafer can be moved below the mask using an in-vacuum x-y stage to allow for step-and-repeat patterning of large surfaces.…”

Suspended, micron-scale corner cube retroreflectors as ultra-bright optical labels

“…21 In this process, a stencil mask, containing a 1 × 1 cm 2 area of 5 µm square openings on a 10 µm pitch in a silicon nitride membrane, is exposed to a broad beam of energetic helium atoms. Particles that strike the opaque regions of the mask are stopped, while those that pass through the openings expose the PMMA resist on the substrate.…”

“…In Fig. 2(e), an in-house, magnetically- enhanced reactive ion etch process 21 using oxygen transfers the pattern into the SU-8, leaving a cube structure. For this process, 1 mTorr of O 2 is introduced into a chamber with a base pressure of 5 × 10 −7 mTorr.…”