Hot Wall Isothermal RTP for Gate Oxide Growth and Nitridation
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Hot Wall Isothermal RTP for Gate Oxide Growth and Nitridation
Allan Laser, Christopher Ratliff, Jack Yao, Jeff Bailey, Jean-Claude Passefort, Eric Vaughan, Larry Page Silicon Valley Group, Thermal Systems Division, Scotts Valley, CA 95066, U.S.A. ABSTRACT A new system that incorporates many benefits of large batch furnaces (high quality films, growth of wet and dry oxides, chlorine capability, and low cost) into a single wafer processing module has been developed at SVG Thermal Systems. The problems associated with wafer temperature measurement and control in traditional lamp based RTP systems are avoided by utilizing a hot wall isothermal processing chamber. Unique fixturing is used to minimize thermal stress on the wafer during ramping. High quality gate oxides ranging in thickness from 20Å to 40Å have been grown in this system using both wet and dry oxidation ambients, with and without chlorine. Thin oxides grown in dry oxygen had 1-sigma uniformities in the range of 0.72-0.95%, while oxides grown in oxygen/HCl (1-3%) had uniformities of 0.80%. Steam grown oxides demonstrated growth rates of 100Å/min at 900oC and uniformities of 0.62%. Dry oxides annealed in NO and N2O had peak nitrogen incorporation levels ranging from 0.5 to 5.1 atomic percent depending on anneal ambient, temperature and time. INTRODUCTION Two trends in the manufacturing of advanced silicon devices have resulted in a shift of oxidation processes towards single wafer thermal processors. The first such trend comes about from the fact that wafer batch size has been reduced in the manufacturing process in both logic and ASIC fabs, where many different device types are often processed in small batch sizes. The small batch is desired to improve cycle time. In some of these cases, the cost of ownership (CoO) advantage long enjoyed by batch furnaces compared to single wafer processing no longer prevails. This trend will continue to accelerate as wafer production moves to 300 mm. The second trend is related to the necessity of preparing multi-processed gate dielectrics for the formation of advanced gate dielectric stacks. No longer is a simple wet or dry gate oxidation required, but in many cases, the gate oxide must be nitrided to enhance its resistance to boron penetration [1] and to increase the device reliability [2]. Nitridation is often accomplished by multi-step processing that requires the use of several different reactive gas species [3]. The smaller volume of a single wafer tools allows such reactive gases to be quickly replaced in a sequential manner resulting in improved process repeatability. Most single wafer oxidation tools are lamp heated systems. Some of these systems have difficulty growing high quality oxides in steam. As a result of the materials of construction (e.g., stainless steel) some lamp-based tools cannot grow the chlorinated oxides that are required to achieve dielectric properties comparable to oxides grown in batch furnaces. These tools also suffer from temperature measurement variability related to variations in the waf
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