Investigations of 2-layer PMMA lift-off structures
The system 50K/200K is more sensitive, the double layer is completely developed at 1500 pC/cm2. The variant 600K/950K in contrast requires the higher dose of 2200 pC/cm2. With increasing dose, also a larger undercut is generated if the 50K/200K system is used, which is thus predestined for complicated lift-off procedures. Variant 600K/950K may be utilized for higher total film thicknesses (> 500 nm) and is a reliable lift-off system for simple applications. For these investigations, always AR 600-60 (IPA) was used as developer which explains both the comparably high doses and the good process stability.
分子量 50k/200k的組合,其敏感度較高,雙層完全顯開約需1500 pC/cm的曝光能量. 分子量 600k/950k則需2200pC/cm的較高劑量. 複雜的懸浮剝離製程,一般先以50k/200k的組合, 增加曝光劑量可獲得較大的下切結構. 600k/950k的組合,則應用於膜厚需求較高的製程(>500nm).
The left diagram shows a comparison of the sensitivity of AR-P 679.03 in two different developers. Under otherwise identical conditions (30 kV, 165 nm film thickness), the sensitivity is almost twice as high if the standard developer AR 600-55 is used as compared to AR 600-60 (IPA). A development with IPA however results in a considerably higher contrast (10.5 : 6.6). This developer is thus predestined for higher resolutions. Experience furthermore shows that the process window is significantly larger as compared to faster developers.Dose deviations of e.g., 10 % are tolerated without any quality loss.
下圖以AR-P 679.03為例顯示在2種不同顯影劑下的敏感度的比較. 在相同參數條件下(30kV, 165nm film thickness), 使用顯影劑AR 600-55比AR 600-50 (IPA),敏感度高出2倍.
然而使用IPA顯影有高對比的特性(10.5：6.6). 因此IPA用於較高解析度的製程. 實驗也顯示其製程穩定度高於快速顯影的製程.