The Performance of The Fast Ramp Vertical Furnace

Abstract

This paper summarizes a Joint Development Project between SEMITOOL, member company and SEMATECH to demonstrate and develop the fast ramp vertical furnace. The goal of this project was to deliver a production vertical furnace capable of heating and cooling a batch of 50 wafers at average ramp rates of 75 and 50 °C/min, respectively. The furnace did meet these goals. This paper will outline the distinctive and enabling design features of the furnace, such as the use of model predictive control techniques to stabilize the wafer temperatures within 2 to 5 minutes of reaching the nominal target temperature. The test results of a ten run passive data collection for a 145 ohm/sq boron S/D anneal and a 65 angstrom gate oxidation process will be discussed. The boron S/D anneal PDC results exceeded the 3 sigma standard deviation for all points goal of 5.0%. The gate oxidation PDC gave a mean of 65 angstroms and met its 3 sigma standard deviation for all points goal of 4.5%. Using an unyielded model (defect density=0) the cost of ownership is estimated to be $3.02/wafer for a 50 wafer load and as low as $1.68 for a 200 wafers load for a gate oxide process. The fast ramp vertical furnace is designed to meet 0.25 and 0.18 micron technology needs, improve cycle time, and give the customer the flexibility of using different wafer batch sizes within a 25” flat temperature zone (where the ramp rates are adjusted according to the wafer pitch).