Publication: Parametric analysis of the heat transfer behavior during the annealing process of the wafer vertical furnace
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Date
2022-05-01
Authors
Tan, Siew Aun
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Abstract
Nowadays, the wafer fabrication process often demands energy efficient equipment. It is thus of great significance to study furnace process chamber key components of semiconductor diffusion equipment. A furnace running at 1123 K for the annealing process was studied both experimentally and numerically in the present study. The experiment was carried out on a vertical furnace which consists of a process chamber, quartz boat, pedestal, heater element, and 175 silicon wafers. Five zones of nickel-made thermocouples were used to measure the temperature in the furnace. Meanwhile, an infrared meter is used to measure the temperature at the process door and top header. In terms of thermal modeling of furnace, three-dimensional modeling was employed to simulate the annealing process in the vertical furnace that operates at temperature 1123 K. The numerical results have been validated and compared with experimental results, and the results show a good agreement. Among all five zones, the experimental study revealed that the bottom zone of the heater needs the highest power consumption of 70 % or equivalent to 18 kW of power consumption. The temperature difference between Spike and Profile temperature for the bottom one shows a difference of 74 K. Besides, the experimental works were also extended to explore the power consumption of two types of heater elements: standard heater and augmented heater with different ceramic insulation composition. Results show that the heater with higher consumption of Al2O3 for insulation ceramic material shows significant energy saving for the bottom zone with the maximum difference of 54 % or equivalent to 13.94 kW of power consumption. By utilizing the numerical model, the change of
heater temperature, environment inert gas, and different flow rates of inlet gas study were examined in the present study. In addition, the influence of thickness of top header and
process door is also evaluated. The results show that the bottom process door dissipates 33 % more heat than the top header of a furnace. The study on the wafer uniformity for different designs was conducted. Numerical results suggest that a furnace with a full boat cover design could yield better wafer temperature uniformity and thus more even temperature distribution could be attained along the stacked wafers. Moreover, the full cover design also gives a reduction of 28 % and 22 % heat loss through the top and bottom end of the furnace. In addition, a lower nitrogen flow rate would be preferred based on flow analysis from the simulation study. In summary, a thicker top header and a better thermal insulated process door with a full boat cover are suggested to reduce the heat losses in the semiconductor furnace.