This paper is going to introduce the detection of CD variation by using overlay metrology in LELE process. The target mark was designed from AIM (Advanced Imaging Metrology) overlay mark. By placing Layer 1 and Layer 2 AIM pattern side by side, CD variation will cause related position changed. And it is able to be detected by overlay tool. On the other hand, overlay shift will not influence this model. It has an advantage over the conventional CD measurement tool. First, the overlay tool throughput is 5~10 times faster than traditional CDSEM and the measurement time is saved. Second, we are able to measure CD and overlay at the same time. Both CD/AA performances are considered and the throughput is also gained.
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Chia Ching Lin, En Chuan Lio, Chang Mao Wang, Howard Chen, Sho Shen Lee, Henry Hsing, Kince Liu, Nuriel Amir, "LELE CD bias offset monitor through OVL measurement," Proc. SPIE 9781, Design-Process-Technology Co-optimization for Manufacturability X, 978118 (16 March 2016);