Patent ID: 7635501

Claim:
A method for preventing deposition of a reaction by-product on an exhaust pipe which is used for discharging a gas from a reaction vacuum chamber, wherein the exhaust pipe has a dual structure comprising an inner cylinder and an outer cylinder with a gap being form therebetween, and the gap is communicated with a space inside the inner cylinder, the method comprising: discharging a gas from the inner cylinder; heating an inner wall surface of the inner cylinder to a predetermined temperature by a heating means disposed on an outer surface of the inner cylinder so as to prevent deposition of the reaction by-product, wherein the inner cylinder and the outer cylinder are connected to each other through a heat insulating material; and forming a gas layer of an inert gas or nitrogen gas along the inner wall surface of the inner cylinder, wherein the gas forming the gas layer is supplied through a gas inlet passage extending through the upstream-side end of the outer cylinder and the inner cylinder without being communicated with the gap, and the gas inlet passage opens at the inner wall surface of the inner cylinder to supply the inert gas or the nitrogen gas into the inner cylinder.