Advanced Mask Inspection Method Using Deep UV Reflected Light Source

摘要

The shrinkage of design rules in semiconductor devices requires an advanced mask inspection tool with an inspection light source having a shorter wavelength for detecting minute defects. We have developed deep ultraviolet (UV) laser illumination optics with a wavelength of 257 nm for application to a mask inspection tool. Optical simulation confirmed that it is possible to enhance the signal contrast by changing the illumination optical system from a transmission optical system to a reflective optical system. Furthermore, by combining these two methods, we have succeeded in detecting signals of minute pinhole defects in phase shift masks for ArF exposure used for the fabrication of devices of the 90 nm generation and beyond.