AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoA

Paper PS2-MoA9
The Role of the Reaction Products in the Silicon Etching Cryogenic Process

Monday, October 31, 2005, 4:40 pm, Room 304

Session: Silicon Etching
Presenter: R. Dussart, GREMI - Universit@aa e@ d'Orleans, France
Authors: R. Dussart, GREMI - Universit@aa e@ d'Orleans, France
X. Mellhaoui, GREMI - Universit@aa e@ d'Orleans, France
T. Tillocher, GREMI, France
P. Lefaucheux, GREMI - Universit@aa e@ d'Orleans, France
N. Mekkakia Maaza, GREMI - Universit@aa e@ d'Orleans, France
M. Boufnichel, ST Microelectronics, France
L.J. Overzet, Univ. of Texas at Dallas
P. Ranson, GREMI - Universit@aa e@ d'Orleans, France
Correspondent: Click to Email
The cryogenic process of silicon deep etching can be used in MEMS and power microelectronic component fabrication. In this process, a SF6/O2 plasma is used to etch high aspect ratio silicon microstructures. The bottom of the structure, which is submitted to ion bombardment, is etched while lateral etching is inhibited by the formation of a SiOxFy passivation layer. This layer, which only appears at low temperature and with oxygen, is continuously deposited on the microstructure sidewalls during the etching process. The formation of this passivation layer is not well characterized. It mostly desorbs when the wafer is warmed up to ambient temperature. In particular, the role of SiF4 (the main etching product) is not well understood. Experiments with SiF4/O2 and SF6/O2 plasmas were carried out to investigate the formation of the passivation layer. Mass spectrometry, profile characterization by SEM and ellipsometry measurements were carried out to better understand the role of SiF4 in the passivation layer formation in the cryogenic process.