Patent ID: 8189195

Claim:
A method of measuring a property of a substrate, the method comprising: generating a patterned mask configured to cause a radiation beam passing through the mask to acquire a pattern; simulating radiating the substrate with a patterned radiation beam that has been patterned using the mask to obtain a simulated pattern; determining at least one location of the simulated pattern that is prone to patterning errors; irradiating the substrate with the patterned radiation beam using a lithographic process; measuring an accuracy of at least one property of the at least one location of the pattern on the substrate that has been determined as being prone to patterning errors, the measuring comprising irradiating a measurement spot with a first radiation source, irradiating a portion of the pattern on the substrate that is larger than the measurement spot with a second radiation source, and comparing relative positions of the measurement spot and the portion of the pattern that is larger than the measurement spot; and adjusting the lithographic process according to said measuring; and reconstructing a portion of the pattern within the measurement spot using an image of the pattern and the position of the measurement spot relative to the portion of the pattern.