# Accurate Location and Manipulation of Nano-Scaled Objects Buried under Spin-Coated Films

## TL;DR

This paper demonstrates that at the sub-micron scale, the topography of spin-coated films accurately reveals buried nano-structures, enabling precise localization and overlay fabrication without flow-induced distortions.

## Contribution

The study shows that flow effects do not obscure buried feature localization at the sub-micron scale and introduces a convolution-based method for accurate topography extraction.

## Key findings

- Resist topography can be modeled by a Gaussian convolution.
- Achieved 3 nm overlay precision in nanowire contact fabrication.
- Flow-shift paradigm does not apply at sub-micron scales.

## Abstract

Detection and precise localization of nano-scale structures buried beneath spin coated films are highly valuable additions to nano-fabrication technology. In principle, the topography of the final film contains information about the location of the buried features. However, it is generally believed that the relation is masked by flow effects, which lead to an upstream shift of the dry film's topography and render precise localization impossible. Here we demonstrate, theoretically and experimentally, that the flow-shift paradigm does not apply at the sub-micron scale. Specifically, we show that the resist topography is accurately obtained from a convolution operation with a symmetric Gaussian Kernel whose parameters solely depend on the resist characteristics. We exploit this finding for a 3 nm precise overlay fabrication of metal contacts to an InAs nanowire with a diameter of 27 nm using thermal scanning probe lithography.