vinyl should be removed before installing ceramic tiles. In general, it requires a total of 1.25" subfloor thickness for ceramic flooring. In most of the new constructions, the builder had put a thin layer of plywood on top of the subfloor before gluing vinyl. You may very likely need to add around 3/8" of subfloor on top. In that case, you would not have to remove the vinyl, but remember, always keep the rough side of the plywood face up, to obtain better adhesion.