Method for determining an overlay correlation set

A method for insuring an alignment precision between two successive patterned material layers for each wafer of a group of wafers, wherein, for each wafer of the group of wafers, a first material layer having a first overlay mark is formed over the wafer, the method comprising:

• performing a pilot run on a first wafer in the group of wafers, wherein the pilot run comprises:
• using an exposure tool with a first overlay correlation set to form a patterned photoresist layer on the first material layer, wherein the patterned photoresist layer comprises a mark pattern and the mark pattern is located over the first overlay mark for defining a later formed second material layer on the first material layer to be a second overlay mark;
• obtaining a pre-process metrology overlay parameter set between the first overlay mark and the mark pattern;
• adjusting the first overlay correlation set at the exposure tool to be a second overlay correlation set according to the pre-process metrology overlay parameter set;
• removing the patterned photoresist layer on the first wafer and inserting the first wafer into the group of wafers;
• and
• performing a photo lithography process and a patterning process on each wafer in the group of wafers, wherein, for each wafer in the group of wafers, a second material layer having a second overlay mark is formed on the wafer with the use of the second overlay correlation set.