TFT光刻DICD均一性改善优化

为了对TFT((Thin Film Transistor)光刻DICD(Develop Inspection Critical Dimension)均一性进行改善,分析了光刻DICD存在差异性的原因,并建立了改善循环流程。对循环流程改善原理及方法进行说明。首先,根据处于光刻系统最佳焦平面位置光刻胶吸收光强最大,DICD最小(DICD_(min))原则,提出了调整光刻平面,使其与系统最佳焦平面趋势一致,可减小DICD差异性。接着,计算出各光刻区域与最佳焦平面位置处的DICD差值(DICD-DICD_(min)),并通过结合光刻区域台板平坦度,判断DICD-DICD_(min)各差值的正负性。然后,采用最小二乘法对光刻区域DICD-DICD_(min)进行平面方程拟合,该平面即为光刻趋势平面,并反映了光刻平面与光刻系统最佳焦平面的差异。最后,以此平面方程作为光刻机台板高度调整平面方程,并对光刻区域台板高度进行调整,从而使得实际光刻平面趋于系统最佳焦平面。结果表明:该方法连续实验3次,DICD均一性可改善30%以上。

Improvement of uniformity of TFT lithography DICD

In order to improve the uniformity of TFT lithography DICD, the reason for the difference of the DICD is analyzed, and a cycle improvement process is established. Its principle and method is illustrated. First, based on the principle that the photo resist absorbs the maximum light intensity on the best focal plane of the lithography system, and the DICD value is also minimum. Therefore, if the lithography plane is adjusted and the lithography plane trend is consistent with the best focal plane trend, the difference of DICD will be minimum. Then the difference of the DICD between the lithography area and the best focal plane area(DICD-DICD_min) is calculated, and the sign of DICD-DICD_min is judged by combining the stage flatness of the lithography area. Then the plane equation of DICD-DICD_min is fitted by the least square method, and the plane is just the lithography trend plane, which also reflects the difference between the lithography plane and the best focal plane. Finally, the plane equation is used to adjust the stage height of the lithography machine, and by adjusting the height of the stage in the lithography area, the lithography plane trend is consistent with the best focal plane trend. The results show that the uniformity of DICD can be improved by more than 30% by doing the experiment three times.