AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS-WeP

Paper PS-WeP3
Study of the Passivation Mechanisms Involved in the Silicon Deep Etching Cryogenic Process

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: X. Mellhaoui, GREMI, France
Authors: X. Mellhaoui, GREMI, France
R. Dussart, GREMI, France
A. Basillais, GREMI, France
T. Tillocher, GREMI, France
P. Lefaucheux, GREMI, France
P. Ranson, GREMI, France
Correspondent: Click to Email
Silicon etching is perfomed by cryogenic SF@sub6@/O@sub2@ plasma process. This process allows to obtain a high aspect ratio (depth/width > 10) and a high anisotropy. The plasma is created in an Inductively Coupled Plasma reactor. The silicon wafer is clamped on a chuck cooled with liquid nitrogen and controlled in temperature. A study of passivation mechanisms is necessary to perfectly control this process and to optimize the trench profiles. The passivating layer is a mixture of Si, F, O and S (SiO@sub x@F@suby@S@subz@). Previous XPS experiments have shown that the passivation layer is removed during the increase of temperature, which proves that the passivation layer is not mainly composed of SiO@sub2@. When destroyed, the passivation layer can be rebuilt with SiF@sub4@ and O@sub2@. This particular experiment was made and has revealed that the presence of sulphur is not necessary to build an efficient passivation layer. Experiments to better understand the passivation layer reconstruction and composition will be presented at the conference. In overpassivating conditions (high O@sub2@ flow), black silicon phenomena appear in trench bottom. Roughness and black silicon pattern depend on several parameters (temperature, bias voltage, O@sub2@/SF@sub6@ ratio). A statistical study made on the black silicon pattern will be also presented.