# Broadband Sub-Micron Moth-Eye Anti-Reflection Coatings on Silicon for Wafer-Level CMOS–SOI–MEMS Thermal Infrared Sensors

## TL;DR

This paper introduces a new method to reduce light reflection in silicon-based infrared sensors using moth-eye coatings, improving their performance and sensitivity.

## Contribution

The contribution is an end-to-end framework for designing moth-eye coatings compatible with CMOS manufacturing for infrared sensors.

## Key findings

- Fabricated structures showed a 46.7% responsivity boost in thermal sensors compared to bare silicon.
- Simulations predict up to 85.1% transmission and 57.1% responsivity enhancement with double-sided patterning.
- Moth-eye metasurfaces are shown to be a scalable solution for wafer-level infrared sensor manufacturing.

## Abstract

Silicon windows in wafer-level packaged LWIR sensors suffer ~30% Fresnel reflection per interface, limiting optical throughput and detector sensitivity. We present an end-to-end design, fabrication, and validation framework for CMOS-compatible moth-eye anti-reflection coatings patterned directly on silicon wafers. Our approach integrates the effective medium theory, a transfer matrix analysis, full-wave FDTD simulations, and experimental Fourier-transform infrared (FTIR) measurements to optimize subwavelength pillar arrays for broadband (8–14 μm) and angle-tolerant performance. Fabricated structures demonstrate a 46.7% responsivity boost in CMOS–SOI–MEMS thermal sensors compared to bare silicon windows, while simulations predict up to 85.1% transmission and 57.1% responsivity enhancement for double-sided patterning. These results establish moth-eye metasurfaces as a scalable, CMOS-compatible solution for next-generation wafer-level processing and packaging infrared sensing platforms, transforming optical improvements into measurable electrical performance gains. The contribution of this work is the end-to-end framework for designing moth-eye wafer level processing and packaging for “real-life” CMOS-compatible infrared sensors manufacturing.