Paper PS1-MoM8
Materials Interactions as a Challenge for BEOL RIE at 22nm Node and Beyond

Monday, November 9, 2009, 10:40 am, Room A1

As feature critical dimension (CD) shrinks toward the 22nm node and beyond, many problems become serious challenges for BEOL plasma patterning. Dimensionally, as pitch size reaches 100nm or below, pattern breakdowns due to resist delamination, mask wiggling and dielectric flopover have been observed. One of the root causes is the high Aspect Ratio (AR) of mask/dielectric lines. Two of the most significant mechanisms, mask flopover and dielectric flopover, occur during the plasma etching process. In the event of former, the soft organic materials in the litho stacks can bend over and lead to mask flopover when the AR is high. This flopover partially shadows the trench and forms distorted dielectric lines. In the later case, the dielectric lines themselves can also flop over at high aspect ratios, which is most likely due to a combination of high AR and low material strength. In addition, wet treatment post plasma patterning can cause significant flopover due to capillary forces. Pattern profile control during BEOL RIE is another major concern and needs to be addressed in order to improve product yield and reliability. In particular, low-k material sidewall damage and trench bottom roughening during RIE need to be improved for better profile control. Moreover, characterization of feature profiles at 22nm node and beyond is a significant challenge. In this paper, the RIE efforts on pattern wiggling/flopover, pattern profile control and profile characterization will be addressed.