Lithography is one of the most important semiconductor micro‐fabrication technologies that form mask pattern images onto the substrate. Since a mask is the original edition of semiconductor patterns, precise control of the mask aperture size becomes critical. The masks have to be made up in the accurately controlled patterns and zero defects. Therefore, mask inspection and metrology that guarantee the mask qualities are important key technologies for realizing the semiconductor production with high reliability and high yield. The advanced inspection and metrology are being developed. The requirements, technical issues, and current status of these technologies are reported. Mask inspection technologies for next generation lithography such as electron projection lithography (EPL) and extreme ultraviolet lithography (EUVL) are also reported. © 2003 American Institute of Physics