Wettability and thermal stability of fluorocarbon films deposited by deep reactive ion etching

Abstract

Fluorocarbon films have low surface energy and can be used as antistiction coating for microelectromechanical systems. By using the passivation process in a deep reactive ion etcher, the fluorocarbon films can be deposited and integrated with other processes in the clean room. The properties such as wettability, surface energies, and thermal stability, have been investigated in detail. It has been found that the fluorocarbon films deposited have a static water contact angle of 109° and a surface energy around 14.5mJ∕m2, whereas as-received and as-deposited single silicon, poly silicon, and silicon nitride have a much lower water contact angle and a higher surface energy. The fluorocarbon films keep their good hydrophobicity up to 300°C, and the degradation temperature depends on the thickness of the fluorocarbon films. Decomposition happens at lower temperatures (100–300°C) even though the decomposition rate is quite slow without affecting the contact angle. The decomposition mechanism at low temperatures (less than 300°C) might be different from that at high temperatures. It has been shown that the fluorocarbon film deposited by a deep reactive ion etcher tool provides very high hydrophobicity, low surface energy, good thermal stability, and antiadhesion behavior for use in nanoimprinting lithography.