| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS1-FrM |
| Session: | Plasma-Surface Interactions in Materials Processing II |
| Presenter: | K. Katahira, Sony Semiconductor Kyushu Corporation, Japan |
| Authors: | K. Katahira, Sony Semiconductor Kyushu Corporation, Japan T. Tatsumi, Sony Corp., Japan S. Kobayashi, Sony Corp., Japan M. Fukasawa, Sony Corp., Japan T. Takizawa, Osaka University, Japan M. Isobe, Osaka University, Japan S. Hamaguchi, Osaka University, Japan K. Nagahata, Sony Corp., Japan |
| Correspondent: | Click to Email |
Silicidation of the source/drain is required to produce high-speed CMOS devices, and suppressing the fluctuation of the contact resistance is one of the most important issues. In this study, we clarified the mechanism of fluctuation in contact resistance caused by plasma processes, and we vastly improved the controllability. The relationship between the plasma parameters and the contact resistance to CoSix was investigated using a dual-frequency (27/2 MHz) CCP system. A SiO2/SiN/CoSix stacked sample with hole patterns was used. A CF4 or CH3F based plasma was used for SiN etching and O2 or H2/N2 plasma was used for the subsequent ashing process. The thickness and composition of the damaged layer were analyzed using XPS, SIMS, and TEM. The ion energy distribution function and the ion penetration depth were calculated using a Monte-Carlo simulation, and a newly developed molecular dynamics (MD) simulation for a Si-O-C-F-H system, respectively. The resistance of the contact increased more when CH3F was used than when CF4 used, and a further increase was observed in a high Vdc condition in CH3F. We found that the resistance increase was caused by incident ions from the plasma. The mass number of dominant ions (CH2F+; m/e=33) in CH3F plasma was much lower than that (CF3+; m/e=69) in CF4 plasma. An MD simulation revealed that the dissociated C, H, and F species from CH2F penetrate deeper than those from CF3 due to the mass number difference of parent ions. Deeper damage caused by the ion penetration stimulates a deeper oxidation of CoSix and raises the contact resistance. We also investigated the effect of the ashing process on the contact resistance. When using a high Vdc condition during ashing, the contact resistance increased significantly. In particular, even in H2/N2 ashing, not using O2, the contact resistance increased. When H2/N2 plasma, the damage of CoSix was formed by deep H penetration. The damaged CoSix layer can be readily oxidized during air exposure, resulting in the resistance increase. We observed that the contact resistance has a linear relationship with oxygen concentration in CoSix. Thus, precise control of the ion energy as well as proper selection of the ion species in the plasma process is indispensable in the fabricating next-generation devices.