Haze Defects due to Pellicle Adhesive

Abstract

The minimum feature size of a semiconductor device will be smaller and smaller because of the increasing demand for high integration of the devices. According to the recently proposed international technology roadmap of semiconductor, ArF immersion lithography will be used for 65 to 45 nm technology nodes. In the 193 nm exposure process, outgassing from the adhesive of the pellicle is a serious problem in the semiconductor industry because it causes haze to form. Various materials contribute to photomask haze including chemical residuals from mask cleaning, outgassing from pellicle adhesive/materials, and contaminants from the scanner ambient. The pellicle lifetime is important in exposure processes, is directly related to the throughput in mass production, and is affected by exposure dose and the environment surrounding the mask. The dependence of the pellicle lifetime on the dose and location of exposure is the subject of this study. The distance between the adhesive of the pellicle and the exposed area was varied to determine the direct relationship between the adhesive and the haze. A 193 nm (ArF) excimer laser was used to expose the mask with and without a pellicle. The surrounding environment of the mask with and without nitrogen purging was also varied. We compared haze formation as a function of accumulated dose. As expected, the crystal growth or haze formation increased as the accumulated dose increased. The adhesive and pellicle material contribute to haze formation; nitrogen purging can reduce haze formation.