High resolution patterning on nonplanar substrates with large height variation using electron beam lithography

Abstract

High resolution patterning on nonplanar substrates with large height variation using electron beam lithography is reported. Using an automatic, high precision, noncontact laser probe microscope, a three-dimensional map of the nonplanar substrate to be patterned is obtained first. This data are converted to a format for the electron beam lithography system, which performs the write by adjusting the plane of electron beam focus based on the mapping data. As a proof of concept of this patterning scheme, three different kinds of nonplanar substrates were used including a tilted Si wafer for a uniform and unidirectional tilt, a planoconvex lens for a multidirectional tilt, and deep Si trenches with a step height variation. The patterning scheme was tested for resolution, field stitching accuracy, and field placement accuracy. The results of these tests are in very close agreement with typical results that are obtained for flat substrates with similar patterning conditions. For wafers with 10 mm tilt, 50 nm gratings show a line width variation of 18%, average field stitching error of 1.06 nm with a 3σ of 24.62 nm, and field placement error of 20.53 nm with a 3σ variation of 31.92 nm. The simplicity of this method and the fact that it can be applied for various nonplanar substrates with nanometer scale precision and over large areas open up a new avenue for the fabrication of devices based on nonplanar substrates.

Bio-inspired photonic and plasmonic systems for gas sensing: applications, fabrication, and analytical methods

“…EBL can also be used to introduce buried defects in PhCs, which is important when attempting to mimic nature’s disorder 154 . Because structures in nature are usually not perfectly flat, there is a need for patterning on non-planar substrates, which EBL accommodates 172 . Traditionally, EBL was restricted to 2D patterns, but layering and stacking enabled the creation of 3D patterns.…”

Metaform optics: Bridging nanophotonics and freeform optics

“…The toroid substrate part was designed to fit in a cassette used for EBL writing on a curved substrate ( 50 ), as shown in fig. S1.…”

“…The necessary adjustment parameters for the objective lens and the deflector were calculated for each writing field within each focal zone. The parameter values were derived on the basis of a calibration measurement using a slanted Si wafer ( 50 ). Zones 1 to 11 were then exposed sequentially by adjusting the focusing plane of the objective to be at the mid-height of each zone.…”

The evolution of the Cornell NanoScale Facility and synergies with the semiconductor Industry

“…In addition to the improved instruments, our ability to routinely correct for electron scattering effects via commercial software, improvements in resist materials, and innovations in the use of multilayer resist stacks have allowed researchers to lead technology into new areas such as: 2.5D and 3D patterning [15], molecular scale probes [16], directed self assembly of block co-polymers [17], silicon nanophotonics [18], integrated optical traps [19], free standing MEMs [20], and many other extremely challenging nanostructure projects. Despite the vastly different capabilities between the modern IC foundry and the typical academic lab, this look-into-the-future capability can directly impact forward looking aspects of Figure 7.…”