In-shot (intra-field) overlay measurement considering overlay mark pattern dependency and illumination source dependency

Recently pattern overlay accuracy becomes more important because of the small pitch patterning. Immersion technology enabled usage of hyper NA beyond 1.0 and this technology provided a lot of possibility to make a very small patterns. But there was no significant technical jump for overlay. Therefore chip makers started to compensate non-linear systematic overlay errors. For example, high order inter-field overlay correction is used to improve overlay performance between the tool to tool matching. Now chip makers are planning to compensate in-shot(intra-field) overlay with higher order compensation than before. Scanner vendors provide intra-field matching options such as i-HOPC(intra-field high order process correction - ASML) and SDM (Super Distortion Matching - Nikon). Those are the methods to match inshot overlay easily. However there are a lot of arguments what the correct way is to measure the in-shot overlay and how we can feedback those measured data to APC system. Especially for the distortion measurement of scanner, we have different data from the mass production trend of distortion. The pattern dependency and another cause of in-shot (intra-field) overlay error will be defined. This will provide a clue to solve difference between the mass production in-shot overlay trend and machine distortion data. The final goal of this study is providing a small hint to design APC system controlling the in-shot(intra-field) overlay with less overlay error.