Optimization of temperature uniformity of a serpentine thin film heater by a two-dimensional approach

In this paper, a two-step method is proposed to optimize the layout of the conventional serpentine film heater thus to improve the temperature uniformity. The optimization is made on transverse direction firstly with varied linewidths and pitches, and then on longitudinal direction with varied line shapes. Based on finite element simulation using a flow field approach, the heater geometry evolution dependent on temperature uniformity is investigated. The results show that the isothermal region extends greatly in transverse direction by the first step, while it extends subsequently in longitudinal direction by the second step and simultaneously shrinks in transverse direction. By a proper tradeoff between these two modification steps, the substrate area within 96.4% temperature uniformity increases by more than five times in comparison to the conventional serpentine heater. This area is even larger by 5% than that achieved by an optimized spiral heater, indicating that the serpentine heater is more powerful to adjust the temperature uniformity. Moreover, the optimized serpentine heater realizes a coverage ratio as high as 86.64% on a rectangular membrane, demonstrating that serpentine heaters are more flexible to substrate shapes than spiral heaters to achieve a uniform and large area temperature distribution.