AVS 57th International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS+MN-WeM

Paper PS+MN-WeM5
SF6/O2/HBr Plasma Processes for the Etching of High Aspect Ratio through Silicon Via

Wednesday, October 20, 2010, 9:20 am, Room Galisteo

Session: Plasma Processing for 3D Integration, TSV, and MEMS
Presenter: S. Avertin, STMicroelectronics, France
Authors: S. Avertin, STMicroelectronics, France
E. Pargon, Ltm - Umr 5129 Cnrs, France
T. Chevolleau, Ltm - Umr 5129 Cnrs, France
F. Leverd, STMicroelectronics, France
P. Gouraud, STMicroelectronics, France
C. Verove, STMicroelectronics, France
O. Joubert, Ltm - Umr 5129 Cnrs, France
Correspondent: Click to Email
Today, the integration density and the chip dynamic power consumption are limiting and restricting phenomena. More than 50% of this consumption is due to long horizontal interconnects, and this rate is projected to increase. One solution to resolve these problems is 3D-Integration which provides smaller wire-length distribution by minimizing the connection length thanks to the fabrication of vertical vias through the silicon substrate or/and the chip. The ITRS roadmap requirement is to etch vias with 2-5 µm in diameter and high aspect ratio (>5). For deep silicon etching, the Bosch etch process which consists in alternating isotropic etching and deposition steps leads to the formation of the so-called scalloping phenomenon on the sidewalls (>100nm). In this paper, we propose to characterize and develop conventional plasma etching processes as an alternative to the Bosh process. The etching development is carried out in ICP reactor accepting 300mm wafers (DPSII from AMATTM) using SF6/O2/HBr plasma chemistries. The scientific objectives are to study the etching mechanism and passivation layer formation in order to get high etch rate (>3µm.min-1), straight profiles and a controlled undercut (<50nm). The etching profiles and etch rates have been analysed using Scanning Electron Microscopy while etch and passivation mechanisms have been studied by quasi-in-situ X-ray Photoelectron Spectroscopy (XPS) and plasma diagnostics (Mass Spectroscopy, ion flux probe..). Preliminary results indicate that the etch mechanisms are strongly driven by the ratio of neutral over ion fluxes and that the etch process is very sensitive to microscopic effects such as the local loading of fluorine and oxygen radicals which is directly correlated to the local pattern density. Through a better understanding of the etch mechanisms, high aspect ratio silicon via with anisotropic profiles and minimized undercut have been obtained.