(1) Field of the Invention
The invention generally relates to a method and apparatus used in semiconductor manufacturing and, more particularly, to a system used to remove moisture from a chamber in a high-vacuum metal deposition system in the fabrication of integrated circuits.
(2) Description of Prior Art
High-vacuum metal deposition systems used widely in semiconductor processing normally have chambers kept at sub-atmospheric pressure and wafers are moved into and out of the deposition chamber through a load lock system. During preventative maintenance or corrective maintenance, the transfer chamber must be opened. This exposes the transfer chamber to the atmosphere allowing the metal to absorb moisture. When the maintenance is completed, a rate of rise (ROR) test is performed. The chamber is pumped down to a specific pressure using the roughing pump and thereafter the chamber is sealed by closing the roughing valve. The chamber pressure is monitored and the increase in pressure is recorded. Because of outgassing, the ROR test always fails thereby placing additional load on the transfer cryogenic pump. To remedy this problem, there is a bake-out procedure used to reduce the moisture and subsequent outgassing. The Applied Materials Endura System has a transfer bake-out procedure whereby high vacuum and high temperature (96xc2x0 C.) are employed. Typically, the bake-out takes about one hour and an additional five hours are required to cool the system. Thereafter the system may still fail the reflectance specification indicating excessive outgassing of oxygen into the chamber. Using the current art procedure, a minimum of three burn in test lots are required before passing the reflectance specification. Each of these test lots require approximately three hours. Therefore, the additional downtime after completing maintenance is at least fifteen hours.
Other approaches incorporating bake-out systems in vacuum chambers exist. U.S. Pat. No. 5,906,680 to Meyerson teaches a CVD system where a bake out is required prior to use of the system. In addition, baking of the wafer carrier is performed when the carrier is placed in the deposition chamber. U.S. Pat. No. 5,336,324 to Stall et al. teaches a method for depositing a coating on a wafer where chamber heating is used. U.S. Pat. No. 5,883,017 to Tepman et al. describe a method of cleaning a processing chamber where the chamber is baked out at an elevated temperature to help drive the water from the enclosure surfaces and thus provide a dry enclosure environment where a stable vacuum may be maintained. This bake out period typically lasts at least 8 hours.
A principal object of the present invention is to provide a method that reduces the pump down time for the transfer chamber in a high-vacuum metal deposition system.
Another object of the present invention is to provide a method that prevents absorption of moisture on the surfaces of the transfer chamber in a high-vacuum metal deposition system during maintenance.
Another object of the present invention is to provide a method that reduces downtime for both scheduled and unscheduled maintenance on a high-vacuum metal deposition system.
Another object of the present invention is to provide a method that increases kit life in a high-vacuum metal deposition system by decreasing burn-in time for the transfer chamber.
These objects are achieved using a system designed to warm the transfer chamber to a set temperature whenever the chamber lid is opened. This reduces moisture build-up on the inside surfaces of the chamber during maintenance, thereby reducing out gassing and time required to bring the chamber back to its base vacuum pressure.