Transfer by direct photo etching of poly(vinylidene flouride) using X-rays

Abstract

A direct pattern transfer method has been developed by photo etching poly(vinylidene fluoride) (PVDF) using X rays (1-16 keV) from a synchrotron storage ring. The ability to pattern thin film of PVDF, a piezoelectric, pyroelectric and ferroelectric polymer, has potential applications in the areas of MEMS, nonlinear optics, and nonvolatile ferroelectric random access memory technology. Without the use of any reactive chemical gas, a maximum etched depth in excess of 9 /spl mu/m is achieved. The etched depth for a given photon energy approaches saturation with respect to exposure time. An in situ mass spectrometry revealed the evolution of hydrogen, fluorine, and hydrogen fluoride species. The etched regions turned dark in color indicating a possible increase in the fraction of carbon atoms. The X-ray transmittance of photo etched PVDF approached that of a pure carbon as the exposure time is increased. Upon etching the root mean-square surface roughness of the etched portion increased by more than a factor of two. The rate of etching increased at elevated sample temperatures.