Reticle consideration for 0.30-μm design rules: between aspiration and actuality

Wafer lithographer expectation will be presented. Based on this expectation we will look at reticle tangible specification as this is required by present wafer photo process. We will attempt to generate provable rather than make-believe mask specification. We will start with a review of reticle specification based on SIA roadmap which is the aspiration of every lithographer. There are different specification for 5X I-Line lithography and for 4X 248nm excimer laser lithography. The 5X I-Line lithography needs the help of optical enhancements and as an immediate result, the Optical Proximity Corrections and Phase Shifting Masks become part of reticle specification. Next, we will talk about actuality in wafer CD budget. In this part we will discuss factors whose contribution is not commonly referred to, such as the shift in the feature edge's position or line shortening effects and variations in proximity effects with stepper illumination setup. A Focus Model will be introduced to quantify CD variations due to focus related aberration, across the exposure field. A statistical metrology model, Norman-Debora, will be used to determine reticle contribution to entire wafer CD budget for 0.30.tm technology. We will calculate process capability index, Cpk and will show how this index can decrease from values larger than one to 0.60, when reticle CD variation increases from 2% to 5% At the end, an actual reticle specification will be presented. This is a calibrated version of the aspiration requirement and is viewed in an integrated context of lithography CD budget.