光刻曝光系统中新型光可变衰减器的研制

Development of a Novel Optical Variable Attenuator in Lithography Exposure System

在超大规模集成电路中,为满足数值孔径为1.35、波长为193nm的光刻曝光系统45nm的成像分辨率要求,设计了一种新型光可变衰减器,用于控制系统的光能透射率,调整曝光能量。该衰减器在光入射角为20°~40°时,衰减面的平均透射率呈线性变化并从95%降低至8%,同时保证其余三个表面的光能损失均低于1%。设计和制作了光可变衰减器的光学薄膜,其基底材料选择熔融石英,膜层材料采用LaF_3和AlF_3。实验测试了光可变衰减器系统性能,测试结果显示该系统的光能透射率在8%~90%范围内连续可调,实验结果满足设计要求。与传统光可变衰减器相比,该系统可调制衰减范围更大,衰减量更稳定,具有一定的应用价值。

In order to achieve the imaging resolution of 45 nm with a numerical aperture of 1.35 and a wavelength of 193 nm in the lithography exposure system of ultra-large scale integrated circuits, a novel optical variable attenuator is designed. The device cannot only control the light transmittance, but also adjust the exposure energy. The average transmittance of the attenuation surface decreases from 95% to 8% linearly when the light incidence angle changes from 20° to 40° , and light energy loss of the other three faces are less than 1% in this system. Optical films are designed and fabricated with fused silica as substrate, and LaF3 as well as AlF3 as optical films. Experiments are performed to investigate the attenuator performance, and the results show that the light transmittance is continuously tunable in the range from 8% to 90%, which satisfies the requirements of the system. Compared with traditional optical variable attenuators, the device is with wider attenuation modulation range and more stable attenuation, and it has potential applications.