AVS 57th International Symposium & Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM3
TiN Selectivity Improvement by DC Voltage Effect in a DC+ Dual Frequency Capacitive Coupled Plasma Etcher

Monday, October 18, 2010, 9:00 am, Room Aztec

Session: Advanced BEOL / Interconnect Etching I
Presenter: M. Nishino, Tokyo Electron AT Limited, Japan
Authors: M. Nishino, Tokyo Electron AT Limited, Japan
M. Honda, Tokyo Electron AT Limited, Japan
Y. Ooya, Tokyo Electron AT Limited, Japan
R. Shimizu, Tokyo Electron AT Limited, Japan
Correspondent: Click to Email
Metal Hard Mask(TiN) damascene scheme has been chosen by many logic semiconductor manufacturers for 2x or beyond BEOL processes. Due to issues related to Aspect Ratio, wiggling, and integration with low mechanical stress resistant porous low-k dielectric materials, TiN hard mask has become thinner and less resistant to etch. As the technology node decreases to sub 20nm, Self-Aligned Via(SAV) process will be introduced for MHM dual damascene scheme to maintain Via CD within the confined specifications of the MHM. With this scheme, TiN MHM is exposed to RIE etch twice: once during partial via formation and another in trench etch. Due to such tight process margins, many semiconductor manufacturing companies are focusing on high selective chemistry for TiN during both Via and Trench dielectric etch process. The DC+ Dual frequency etcher is a capacitive coupled plasma etcher with a superimposed DC voltage. This configuration has been proven to be more effective for maintaining TiN hard mask during dielectric etching. A negative DC bias is applied to the upper Si electrode. The Si electrode surface reacts with CFx radicals from fluorocarbon based plasma and the fluorine component of bulk plasma was reduced. This phenomenon is the interaction between fluorocarbon based plasma and Si electrode which was induced by DC voltage. This paper presents an investigation of TiN hard mask high selective process from this interaction. We measured Ne and Vdc areas of MHM trench process both with and without DC voltage conditions and investigated the direction of Ne/Vdc windows as MHM trench process at first . We evaluated this interaction effect from Ne and Vdc trend with DC voltage and observed that DC voltage did not only acquire higher TiN selectivity to dielectric (maintain TiN thickness) but also reduce TiN HM facet etching rate (control CD shift) in dielectric etching. This is one of the advantages for the DC+ Dual frequency capacitive coupled plasma etcher .