静电卡盘与晶圆之间稀薄气体传热的影响因素
Factors influcing rarefied gas heat transfer between a wafer and an electrostatic chuck

通过在晶圆背面填充稀薄气体的方式来对晶圆进行冷却或加热是等离子体刻蚀工艺中的一项关键技术。该文对晶圆与静电卡盘之间的稀薄气体传热问题进行了解析建模, 给出了一个适用于整个气压范围的气体导热解析表达式, 并用直接模拟Monte Carlo方法验证了其准确性。基于该解析模型, 还对气体压强、狭缝距离、热适应系数和气体温度等影响传热系数的参数进行了研究, 发现狭缝距离和气体温度对传热系数影响较弱, 即静电卡盘表面形貌(如凸台高度等)和刻蚀温度对于静电卡盘与晶圆之间的传热效果影响不大; 而气体压强和热适应系数都表现出对传热系数有明显的影响。因此, 在实际的刻蚀工艺中, 可以通过调节气体压强来改变静电卡盘与晶圆之间的传热效果。
Abstract：Wafer cooling/heating by gas flow along the backside of the wafer is a key part of the plasma-etching process. The rarefied gas heat transfer across the gap between the wafer and the electrostatic chuck is modeled in this article with an analytical equation developed for the entire pressure range whose predictions are verified by direct simulation Monte Carlo results. The model is then used to investigate the effects of the gas pressure, gap size, accommodation coefficient and gas temperature on the heat transfer coefficient. The gap size and gas temperature have little influence, so the etching temperature and the surface profiles like the height have little effect on the heat transfer between the wafer and the electrostatic chuck. However, the gas pressure and the accommodation coefficient significantly impact the heat transfer coefficient. Therefore, changes in the gas pressure during the etching process will significantly affect the heat transfer between the wafer and the electrostatic chuck.