D34 states, however, that an inert carrier gas such as argon is added only if required (see column 1, lines 66 to 70).4.1.1 Silane and methane as disclosed in D34 are amongst the preferred precursor gases according to the patent in suit (see column 5, line 58 to column 6, line 3) while the generated hydrogen represents an etching gas according to the patent in suit (see also claim 13 of this reque