RfSi(R)p(X)3???p???Formula 1 RFSi(R1)q(X1)3???q???Formula 4 SiX2 4???Formula 5 wherein Rf is a fluorine-containing organic group having an etheric oxygen atom, RF is a fluorine-containing organic group having no etheric oxygen atom, each of R and R1 which are independent of each other, is a C1-6 hydrocarbon group containing no fluorine atom, each of X, X1 and X2 which are independent of one anothe