Closed-loop controlled apparatus for preventing chamber contamination

摘要

A closed-loop controlled apparatus and method for preventing contamination to a low pressure chemical vapor deposition chamber (LPCVD) are provided. The apparatus includes an exhaust vent equipped with a butterfly valve for controlling a flow rate through the vent. The exhaust vent is connected to a vacuum outlet and a vacuum pump on a process chamber in parallel with and bypassing a gate valve such that the exhaust vent can be opened for the continuous pumping of the process chamber during wafer loading and unloading steps. The exhaust vent may be constructed by two end conduits that have a larger diameter which are connected by a middle conduit that has a smaller diameter such that during vacuum evacuation, the fluid flow rate in the small diameter conduit is at least four times that in the large conduit to effectively prevent the deposition and blockage of the small conduit by reaction by-products or contaminating particles. The butterfly valve installed in the exhaust vent provides an indication of the degree of blockage of the vent and enables a process controller to shut-off the process chamber for wet cleaning when a blockage has been detected for preventing chamber contamination.