For the new project VEGAS (see AR NEWS, 25 th issue, October 2012), columnar resist structures with a thickness of 10 to up to 60 µm are required. These columns should be producible in a strictly cylindrical shape or, if needed, also conical narrowing down to the bottom.
In order to achieve this variability, the bake regime for AR-N 4400 (CAR 44) was optimized. Vertical side walls were obtained with a multi-step coating procedure. A fourfold coating of 10 µm-layers each with consecutive bake step after each coating resulted in a total film thickness of 40 µm. This particular coating procedure completely prevents the formation of the usual and disturbing edge beads. The development speed turned out to be constant across the entire film thickness, and vertical structures resulted. Even a slight undercut can be adjusted by varying the bake times of single coating steps. For this purpose, lower layers are dried faster.
These interesting results were reason enough for us to choose CAR 44 as resist of the month.
[Bild] „CAR 44“ /wMedia/img/klein/RdM_Okt12.jpg
40-µm structures with optimized bake regime for CAR 44