Photolithography system using annular illumination

Photolithography is a leading technique in LSI device fabrication. The LSI pattern size has approached the exposure wavelength such as the g or i-line of a Hg lamp. This fact indicates that the shorter wavelength or some novel technique will be needed in order to cope with finer patterns. It is known that annular illumination can improve the depth of focus and resolution. We applied the annular illumination method to the step and repeat exposure system. Experiments and simulations using annular illumination were carried out and subhalf-micron patterns were produced. The process latitudes of the annular illumination method are evaluated.