Analysis of formation mechanism of deposited film in a high-aspect-ratio hole during dry etching using fluorocarbon gas plasmas

In the dry etching process using fluorocarbon (FC) gas, deposited amorphous-CF x (a-CF x ) films in patterns, such as holes and trenches, strongly affect the etching performance. The influence of the FC gas molecular structures and their atomic compositions on the formation of a-CF x films at different positions in the holes were investigated. It was found that the deposition region and thickness of the a-CF x film strongly depend on the molecular structures of the FC gas, such as double bonds, benzene rings, and the atomic ratio of fluorine to carbon.