Effects of airborne molecular contamination on 157-nm resists: AMC friend or foe?

International SEMATECH(ISMT) has operated a 157nm Resist Test center since June of 2000. During this time, we have processed hundreds of 157nm photoresist samples from major resist suppliers and research organizations. Almost all of these of these early 157nm resists have demonstrated unusual susceptibility to airborne molecular contamination (AMC). Tests were completed at ISMT comparing post exposure delay stability of 157nm fluoropolymer resists to production level 193 and 248 nm resists. The 157nm resist samples were approximately 5X more sensitive to AMC. We have implemented extensive AMC control measures including the introduction of mini-environments and filtered wafer carriers to mitigate the AMC sensitivity of these resists. The effectiveness of the control measures was measured using a real time airborne base monitor, grab samples, and resist delay studies. 157nm resists were severely affected by relatively low airborne base concentrations of approximately 1 ppbv NH 3 . Hold time stability was significantly improved when the airborne base concentrations was reduced to 3 appear to be influencing resist profiles and delay response.