Lele Cd Bias Offset Monitor Through Ovl Measurement

As device design rule has been made pattern size shrink, LELE (Litho-Etch Litho-Etch) process is used in advance pattern process more and more. The CD control is one of the most critical factors for semiconductor manufacturing. However, the numbers of current in-line measurement points are not sufficient for the whole wafer CD monitoring. It's the goal to increase inline monitor capacity without suffering process cycle time. To generate an innovation pattern to reach the goal is the purpose for the advance pattern process.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 similar to 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.