浸没式ArF曝光系统在最后一面物镜和晶圆之间引入液体作为成像介质.曝光过程中,液体存在热分布变化,并引起液体折射率的改变,导致光刻性能下降,因此,有必要确定液体热分布变化的情况.应用有限元方法,建立二维模型,分析液体在不同进口压强下的温度分布,同时分析液体流入方向与晶圆移动方向异同情况下的液体温度分布.在此基础上,分析了晶圆上残留热量对液体热分布变化的影响.结果表明,不考虑晶圆残留热量,温度升高的最大值在0.15 K左右,温升厚度最大可达到0.4 mm;考虑晶圆残留热量的影响,温度升高最大值增加0.02 K左右,温升厚度最大可达到0.45 mm.
The liquid which is inserted between the final lens and the wafer is an imaging medium in ArF immersion lithography system. During the lithographic exposure, the change of temperature distribution in the liquid can result in the change of its refractive index and the decrease of the quality of its lithography. So, it is necessary to determine the distribution of the temperature. In this work, a finite element method was applied to establish a two-dimensional computational model so that the temperature distribution of the liquid at different inlet pressure can be analyzed when the flow direction of the liquid is consistent or opposite with the movement direction of the wafer. By the analyses above, the influence of the residual thermal energy in the wafer on the temperature distribution of the liquid was analyzed. The results show that the maximum increment of the temperature is about 0.15 K and the thermal penetration depth is 0.4 mm when the residual thermal energy in the wafer is not considered and they are respectively 0.02 K and 0.45 mm when the residual thermal energy in the wafer is considered.