Resist pattern inspection function for LM7500 reticle inspection system

Conventionally, pattern inspection is performed on completed reticles. In other words, the completed circuit pattern on a reticle is inspected after etching and removing the resist. This pattern consists of the transmission region (Qz), half transmission region (MoSi) and shading region (Cr). If the process stage where a detected defect occurred can be specified, detection can be made at an earlier process stage, enabling an improvement in the process and/or yield. When inspecting the resist pattern on a reticle before the etching process, points such as the endurance of the resist against the inspection light beam and the effect of the gas that is generated by irradiation must be considered. In addition to there being no damage to the resist pattern, there must also be no contamination of the optical elements caused by outgases. To prevent contamination, therefore, we developed a cassette-type enclosure with gasproof windows in which the reticle is set, thus shutting out outgases. Also, because the image of the resist pattern is very different from a normal pattern, we needed to develop various functions, such as algorithms, to detect defects on the resist pattern. This time, we have successfully developed a resist pattern inspection function for the LM7500 reticle inspection system. This function enables both die-to-database and die-to-die inspection and features an inspection light wavelength of 266 nm, allowing the detection of smaller defects that could not be detected with an i-line (365 nm) inspection system.