AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS1-MoM

Invited Paper PS1-MoM1
Modification Mechanisms of Porous Low-k SiOCH Film during Plasma Ashing Processes

Monday, November 9, 2009, 8:20 am, Room A1

Session: Advanced Interconnect Etch
Presenter: K. Kurihara, Toshiba Corp., Japan
Authors: K. Kurihara, Toshiba Corp., Japan
T. Imamura, Toshiba Corp., Japan
K. Yamamoto, Toshiba Corp., Japan
H. Hayashi, Toshiba Corp., Japan
Y. Nakasaki, Toshiba Corp., Japan
Correspondent: Click to Email
Porous low-k SiOCH materials are being introduced in order to realize highly reliable interconnects for sub 32 nm node LSI. There are still several problems regarding its use. One of the problems is the damage to low-k materials during etching and ashing processes. During resist ashing process the loss of hydrophobic groups in the pore leads to the uptake of water into the film and results in an increase in k value. To overcome this issue, two approaches are considered. In one approach, the low-k material itself becomes resistant to the plasma processes. In the other, the low-damage plasma processes are developed. The collaboration of both approaches is probably necessary to achieve interconnection for future device generations. We studied the above two issues from the viewpoint of fundamental mechanisms. Concerning the former issue, we have examined the dependence of the plasma resistance of SiOCH films on the film structure, which contained the methylene-bridge (Si-CH2-Si) and/or the methyl groups. It was found that the decrease in the amount of carbon in the SiOCH film containing only methyl groups is larger than that in the film containing methylene bridges. Concerning the latter issue, we have investigated the mechanism of ashing process using CO2 plasma. It was found that a densified layer was formed at the outermost surface of the SiOCH film during ashing, and the layer plays an important role in the control of water absorption into the film. This ashing process resulted in lower damage to the SiOCH film compared with O2 or N2/H2 plasmas.