Recipe design to prevent tungsten (W) coating on wafer backside for those wafers with poly Si on wafer backside

摘要

In a CVD vacuum chamber processing system for depositing a blanket of refractory material, such as tungsten, upon a frontside of a semiconductor wafer, an inert gas, such as argon is directed to the backside of the wafer in a manner so as to prevent the chamber reaction gases from reacting with polysilicon or other materials on the backside of the wafer as well as to prevent the deposition of the blanket material on the backside of the wafer. This method alleviates the problems of particulate generation and loss of wafer backside datum surface due to the inadvertent buildup of unwanted materials. The wafer is placed on a heater platen and is secured by a specified range of vacuum pressures. The wafer is exposed to specified ranges of chamber pressure during the deposition phase. During the purge phase, the chamber pressure is reduced and the wafer chucking pressure is increased to a specified range. The method is terminated with the equalization of pressure between the front and backside of the wafer.