\u201cTop-down\u201d and \u201cbottom-up\u201d strategies for wafer-scaled miniaturized gas sensors design and fabrication

Lin Liu,Fuqin Sun,Shuqi Wang,Sujie Qin,Lianhui Li,Yuanyuan Bai,Yingyi Wang,Yanbing Dai,Ting Zhang,Tie Li

doi:10.1038/s41378-020-0144-4

Abstract

Manufacture of large-scale patterned nanomaterials via top-down techniques, such as printing and slurry coating, have been used for fabrication of miniaturized gas sensors. However, the reproducibility and uniformity of the sensors in wafer-scale fabrication are still a challenge. In this work, a “top-down” and “bottom-up” combined strategy was proposed to manufacture wafer-scaled miniaturized gas sensors with high-throughput by in-situ growth of Ni(OH)2 nanowalls at specific locations. First, the micro-hotplate based sensor chips were fabricated on a two-inch (2”) silicon wafer by micro-electro-mechanical-system (MEMS) fabrication techniques (“top-down” strategy). Then a template-guided controllable de-wetting method was used to assemble a porous thermoplastic elastomer (TPE) thin film with uniform micro-sized holes (relative standard deviation (RSD) of the size of micro-holes <3.5 %, n > 300), which serves as the patterned mask for in-situ growing Ni(OH)2 nanowalls at the micro-hole areas (“bottom-up” strategy). The obtained gas microsensors based on this strategy showed great reproducibility of electric properties (RSD < 0.8%, n = 8) and sensing response toward real-time H2S detection (RSD < 3.5%, n = 8).

Highlights

High-throughput and low-cost wafer-scale fabrication of metal oxides based gas sensors with good reproducibility and uniformity are urgent demanded for wide applications in environmental monitoring[1,2]
After constructing all of the structures on the front side, reactive ion etching (RIE) and silicon deep etching were employed to etch the back of the silicon
A controllable template-guided de-wetting method was utilized as a bridge to integrate “top-down” and “bottom-up” strategies to implement in-situ growth of Ni(OH)[2] nanowalls at specific locations for wafer-scale fabrication (Fig. 1a)

Summary

Introduction

High-throughput and low-cost wafer-scale fabrication of metal oxides based gas sensors with good reproducibility and uniformity are urgent demanded for wide applications in environmental monitoring[1,2]. Template-guided controllable de-wetting method with the capability to precisely control the shape, size, and location of liquid droplets shows the feasibility to assemble uniform porous film due to the immiscibility of two different solutions[28]. It is a potential approach to integrate “bottom-up” (in-situ growth) and “top-down” (MEMS fabrication techniques) strategies for wafer-scale fabrication of miniaturized gas sensors by utilizing the uniform porous film as a mask for in-situ growth of metal oxides.

Results

Conclusion