Anisotropic pyrochemical dry etching of fluorinated ethylene propylene induced by pre-irradiation with synchrotron radiation

Kaito Fujitani,Masaya Takeuchi,Yuichi Haruyama,Akinobu Yamaguchi,Yuichi Utsumi

doi:10.1063/6.0000702

Abstract

Anisotropic pyrochemical micro-etching induced by synchrotron x-ray irradiation is developed as a microfabrication process for fluorinated ethylene propylene (FEP). X-ray irradiation is performed at room temperature, and the irradiation area is etched by heating in an oven. By measuring the irradiation area using Raman spectroscopy, the peak of the Raman spectrum is shown to decrease with an increasing irradiation dose. It is also observed that the etching can be performed at a heating temperature of around 200 °C while maintaining the chemical composition of the surface. The etching mechanism is speculated to be as follows: x-ray irradiation causes chain scission, which decreases the number-average degree of polymerization. The melting temperature of irradiated FEP decreases as the polymer chain length is decreased so that the irradiated area can be evaporated at low temperatures of post-heating. In this way, we demonstrate that anisotropic pyrochemical micro-etching of FEP proceeds only in the depth direction where x rays are absorbed. It is possible to avoid deterioration of the shape accuracy arising from thermal expansion during the transfer process of the mask pattern by separating pre-irradiation from post-heating. Through this method, it becomes possible to realize a high precision microstructure of FEP in a large area.

Highlights

Micro-chemical systems have been widely applied in various fields such as medical diagnosis, environmental analysis, and food, based on the concept of point of care testing (POCT)
This study investigated the manufacturing process of fluorinated ethylene propylene (FEP) microstructures fabricated by anisotropic pyrochemical microetching
The basic mechanism of the photodetachment reaction and etching of FEP was investigated by Raman spectroscopy, theoretical calculation, and x-ray photoelectric spectroscopy (XPS)

Summary

INTRODUCTION

Micro-chemical systems have been widely applied in various fields such as medical diagnosis, environmental analysis, and food, based on the concept of point of care testing (POCT). It has been reported that a lateral distortion strain occurs when micro-fabrication of fluorine resin is performed using synchrotron radiation at elevated substrate temperatures above 200 ○C This is considered to arise from the difference in the thermal expansion coefficients of Ni and fluorine resin used as the structural material of the x-ray mask and the expansion and contraction of the irradiation area arising from the heating and cooling of the beam scanned path. To solve this problem, we investigate the microfabrication of FEP by anisotropic pyrochemical micro-etching by separating the irradiation process of synchrotron radiation from the heating process of the irradiated substrate. We report the anisotropic pyrochemical microetching technique of FEP by x-ray irradiation and the etching mechanism

EXPERIMENTAL

RESULTS AND DISCUSSION

SUMMARY AND CONCLUSIONS