AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS-MoM

Paper PS-MoM4
A Novel Gate-Electrode Fabricating Technique using a Sequential UHF-ECR Plasma Process

Monday, November 4, 2002, 9:20 am, Room C-105

Session: Conductor Etch I
Presenter: M. Mori, Hitachi, Ltd.,Japan
Authors: M. Mori, Hitachi, Ltd.,Japan
T. Tsutsumi, Hitachi High-Technologies Corp.,Japan
N. Itabashi, Hitachi, Ltd.,Japan
M. Izawa, Hitachi, Ltd.,Japan
Correspondent: Click to Email
For fabricating beyond 90 nm-node devices, ArF lithography will be increasingly used. This process demands that the gate electrode must be trimmed more than 50 nm after lithography and critical dimension (CD) shift variation must be suppressed within 3-5 nm across the wafer. However, gate-electrode trimming of more than 50 nm using only ArF trimming is difficult, because the resist is too thin or bent in followed hard-mask etching. Therefore, we have developed a sequential gate process consisting ArF/polySi trimming that uses a UHF-ECR plasma. This plasma has capability to precisely CD-shift control, because of its moderate ion-current flux (ICF) at low pressure and its by-product uniformity control.@footnote 1@ In polySi trimming, we evaluated the vertical undercut process. By using this process, we can measure gate-length with a CD SEM after wet etching. For vertical undercut process, we used multi-step etching, consisting a polySi main etching step with a thin side-wall protection film, followed by a highly selective trimming step. The amount of trimming could be controlled by the time of trimming step, and 86.5±1.5 nm trimming was obtained without punching through in a 2.5-nm gate-oxide layer. Regarding ArF trimming, it was confirmed that O@sub 2@ containing gas chemistry provided good hard-mask selectivity and good linearity of time control. Trimming - rate variation across the wafer was within 2.7 nm/min. To suppress resist bending in hard-mask etching, the vertical/horizontal etching rate ratio was controlled in ArF trimming, and CHF@sub 3@ based gas chemistry was used for the hard-mask etching. This good linearity of CD control with time in ArF/polySi trimming will be caused by UHF-ECR plasma that has more moderate ICF and less interaction with the reactor wall. @FootnoteText@ @footnote 1@ M. Mori, et al., (2000), Proceeding of Solid State Devices and Materials, p. 192.