Abstract
As the minimum feature size shrinks down, i.e. low K1 lithography regime, the tool’s lens aberration sensitivity and user defined illumination imperfection might play a major role in patterning error. Thus, the study of impact from lens aberration and illumination on patterning is required for good tool maintenance and yield improvement. For this purpose, we collected many cases of abnormal patterning result from production line and then simulated in terms of actual lens aberration and illumination source data. LITEL products of ISI(In-situ Interferometer) and SMI(Source Metrology Interferometer) were used for characterizing lens and illumination source. Moreover, the ACE(Analysis and Characteristic Engine) of LITEL development product was used as the simulator.
In this work, deformation of pattern fidelity, for example, CD asymmetry in word line and metal contact layer, pattern bending in isolation layer and also decreasing process window in bit line layer will be discussed with experimental and simulation data. Finally, we are able to make a guideline for preventing abnormal phenomenon. From this study, we can understand which lens aberration terms and illumination imperfection take an effect of abnormal pattering result.
