Off-line photolithographic parameter extraction using electrical test structures

A description is given of how and when electrical test techniques should be used for measuring photolithographic parameters. Results are given on stepper matching, reticle overlay, process latitude, and lens characteristics using electrical linewidth and misalignment structures. Electrical test structures show great flexibility and accuracy down to dimensions on the order of the wavelength of light used in comparable optical systems. Their main drawback is the need to etch and resist strip the wafer before probing. This leads to an unacceptably long turnaround time and has restricted their use to offline applications such as machine or material acceptance and process characterization.