AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoM

Paper PS2-MoM7
Deep Cryo-Etching for Silicon Structures

Monday, November 15, 2004, 10:20 am, Room 213B

Session: Silicon Etching
Presenter: T.T. Tillocher, GREMI - Orléans University, France
Authors: T.T. Tillocher, GREMI - Orléans University, France
R.D. Dussart, GREMI - Orléans University, France
X.M. Mellhaoui, GREMI - Orléans University, France
P.L. Lefaucheux, GREMI - Orléans University, France
M.B. Boufnichel, ST Microelectronics - Tours, France
P.R. Ranson, GREMI - Orléans University, France
Correspondent: Click to Email
Semiconductor technology requires more and more accuracy in deep etching. The cryogenic process, which uses a SF@sub 6@/O@sub 2@-based chemistry and a cryogenically cooled wafer chuck, is promised to a great future since it provides smooth profiles and high etch rates. Indeed, this cryo-etching enables to realise with these good performances different patterns on silicon and SOI wafers (vias, trenches...) for a wide range of mask openings. This process is very accurate and fastidious to control since its efficiency results from a weak equilibrium between the simultaneous etching and passivation mechanisms. If the latter is broken, defects (black silicon, notching, bowing, undercut...) can appear and grow very quickly. We will detail these different defects and their conditions of appearance. A new cryogenic chuck, associating electrostatic clamping and a very good temperature uniformity , allows the etching of very uniform profiles all over the surface of the 6'' wafers. This is a critical aspect in the project since for certain projects the two sides of the wafer have to be etched separately and the profiles, depending on the temperature, must have the same shape from one side to the other. Parallel plasma diagnostics, such as actinometry, Langmuir probe, FTIR, interferometry, are the key to a better understanding of the process and hence to better control the process. We will present our last results on projects carried out in collaboration with STMicroelectronics/Tours. Some plasma measurements will be presented and correlated to the etching performances.