A Cost Model Comparing the Economics of Reticle Requalification Methods in Advanced Wafer fabs

Progressive mask defect (such as crystal growth, haze etc.) continues to threaten the industry (especially at 193 nm lithography) [1]. This drives the need for wafer fab mask inspection [2] which can be achieved via two methods. The first method is indirect, commonly known as image qualification[4], where a mask is being exposed followed by the inspection of the printed wafer to detect if there is any repeater on the wafer or not. The other method of mask inspection is direct mask inspection (such as STAR
light
trade). Understanding the economics involved in wafer fab mask inspection is important as litho- cluster cycle time will drive the economics for fabs even harder at nodes 65 nm and below and any methods or techniques that can reduce this litho- cluster cycle time need to be looked at seriously. It was one of the goals for this technical report to evaluate the impact (if any) of these wafer fab mask inspection methods on litho-cluster cycle time.