ABSTRACT
Figure 16.3 shows an etching result of a “submicron feature-optimized” Bosch’s process. is rst example (Figure 16.4) shows a 360 nm opening-15 µm depth (aspect ratio 1:41). ick EB resist (OEBR-CAP112 PM by Tokyo Oka) was used for direct 4-in. EB exposure with high-throughput EB writer (F5112 + VD01
ADVANTEST). Designed line and space dimension on computer-aided design data was a 300 nm trench for a 550 nm pitch (250 nm for remaining silicon). A 30 nm of undercuts resulted in a 360 nm opening and 190 nm silicon n structures. A 100 nm opening trench is tried as well. An 80-nm-thick aluminum (Al) mask was patterned with li-o on a negative EB resist (OEBR-CAN028T2 PE). Because of 35 nm of undercut on both trench sides, trench opening width resulted in 170 nm (Figure 16.5). Average etching depth was 11.5 µm (aspect ratio 1:68). Etching time was 20 min (10 min + 2 min of pause + 10 min).
