Etch characteristics of BCB film using inductively coupled plasma

The etching characteristics and mechanism of BCB thin films were investigated as a function of CF4/O2 mixing ratio in ICP system. Maximum etch rate of 830 nm/min is obtained at the mixture of O2/CF4 (=80%/20%). OES actinometry results showed that volume density of oxygen atoms fallows the same extreme behavior with the BCB etch rate, while the density of fluorine atoms changes monotonously. Therefore chemical destruction of BCB by oxygen atoms was proposed as the dominant etch mechanism. XPS analysis showed that the addition of CF4 to O2 helps to volatilize silicon atoms containing in BCB but leads to the formation of F-containing polymer layer. The profile of etched BCB film was close to 90 .deg. and the surface was clean