Advancements in pellicle glue residue removal

摘要

A pellicle is employed to protect a photomask from particle contamination. The pellicle is positioned at a distance from the photomask pattern such that particle contaminants are out of focus. To extend the lifetime of a photomask, the pellicle must be replaced when it becomes heavily contaminated or damaged. The replacement process generally consists of the following three steps, 1) removal of the existing pellicle, 2) cleaning of the photomask, and 3) installation of a new pellicle. The cleaning step is primarily required for the removal of pellicle-glue residue unintentionally left behind during the pellicle removal process. This cleaning step has traditionally employed aggressive chemistries, such as a long process cycle, utilizing a Sulfuric Acid and Hydrogen Peroxide mix (SPM). The major drawback from this approach is that it inadvertently exposes the photomask pattern to aggressive chemistries, risking CD shift, damage to sub-resolution assist features (SRAFs), and accelerated haze growth, thus, ultimately reducing a masks lifetime [1]. To overcome these shortcomings, this paper presents a localized approach for removal of pellicle-glue residue, which does not require long SPM cycles for post-clean.