In this article, we will analyze in-field uniformity (IFU) fluctuation of linewidth on wafer considering errors related to mask pellicle process. As gate linewidth becomes smaller, the controllability of in-field uniformity (IFU) plays a key role in wafer manufacturing yield. IFU depends on various lithography parameters including mask CD (critical dimension) uniformity, MEEF (mask error enhancement factor), exposure margin, focus margin, transmittance, flare and illumination uniformity. Although the short term repeatability of IFU is manageable, various parameters which affect IFU are still changing. During the wafer process, mask re-pellicle process is unavoidable due to haze contamination. For this reason, mask pellicle process including cleaning should be carefully controlled to achieve the long-term IFU stability on wafer as well as exposure machine (optic), resist coating (resist property). This paper will discuss the various experimental works including IFU correlation on wafer in terms of optic stability, resist stability and mask pellicle process. CD uniformity data on mask and IFU data on wafer is obtained from optical measurement tool to reduce measurement error disregarding local CD variation.