Real-time mathematical model for wafer spin defect detection and for misalignment analyses

A method of inspecting semiconductor wafers comprising:

• comparing a Residual 3 Sigma value corresponding to at least one feature on a wafer in a lot of wafers to a mathematical model, wherein the mathematical model comprises a threshold value corresponding to the at least one feature of the wafers;
• determining whether the Residual 3 Sigma value for each wafer in the lot are not greater than the threshold value;
• grouping into a group (P) those wafers whose Residual 3 Sigma value are not greater than the threshold value;
• calculating a standard deviation (σL) and a mean (μL) for the Residual 3 Sigma value for the wafers in the lot;
• calculating a standard deviation (σP) and a mean (μP) for the Residual 3 Sigma value for the wafers in the group (P);
• flagging the lot for further inspection if:
• (σL/μL)Lot−(σP/μP)P>(x)
• wherein (x) is a predetermined threshold amount, and wherein (σL/μL)Lot represents the standard deviation of the Residual 3 Sigma values for the lot divided by the mean of the Residual 3 Sigma values for the lot, and further wherein (σP/μP)P represents the standard deviation of the Residual 3 Sigma values for the group (P) divided by the mean of the Residual 3 Sigma values for the group (P);
• and
• conveying an indication of the flagging to facilitate further inspection.

A computer readable storage medium containing program code for enabling a computer for use in inspecting semiconductor wafers, the program code comprising:

• program code for comparing a value for each wafer in a lot of wafers to a mathematical model, wherein the values include data about at least one feature on each wafer, and wherein the mathematical model comprises a threshold value corresponding to the at least one feature, and further wherein values greater than the threshold value comprise an indication of a spin defect;
• program code for determining whether any of the values of the wafers in the lot are not greater than the threshold value;
• program code for grouping into a group (P) those wafers whose values are not greater than the threshold value;
• program code for flagging for further inspection those wafers having values greater than the threshold;
• and
• program code for conveying an indication of the flagging to facilitate further inspection of those wafers having values greater than the threshold value.