Stochastic optical proximity corrections

A method of improving mask data used in fabrication of a semiconductor device, the method comprising:

• defining a cost function associated with a defect based on stochastic failure rate of the defect;
• performing a first inverse lithography technique (ILT) optimization of the mask data using nominal values of mask pattern contours;
• performing a second ILT optimization of the first ILT optimized mask data using stochastic values of the mask pattern contours until a first value of the cost function is less than or equal to a first target value;
• Manhattanizing the mask pattern contours of the second ILT optimized mask data;
• and
• Performing, by a processor, a Manhattan optimization of the Manhattanized mask pattern contours until a second value of the cost function is less than or equal to a second target value.

A non-transitory computer readable storage medium comprising instructions which when executed by a processor cause the processor to:

• set a threshold value associated with a defect based on stochastic failure rate of the defect;
• perform a first optimal proximity correction (OPC) of the mask data using nominal values of mask pattern contours;
• identify locations within the first OPC mask data where stochastically determined mask pattern contours may lead to the defect;
• place check figures on the identified locations to enable measurement of distances between the stochastically determined mask pattern contours;
• and
• perform a second OPC of the first OPC mask data so as to cause the measured distances to be greater than the threshold value.