AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS2+MN-WeA

Paper PS2+MN-WeA2
The Generation and Removal of Heat during DRIE of High Aspect Ratio Structures in SOI with Buried Cavities

Wednesday, November 11, 2009, 2:20 pm, Room B2

Session: High Aspect Ratio and Deep Etching for 3D Integration and Memory
Presenter: J. Dekker, VTT Microelectronics Research Center of Finland
Authors: J. Dekker, VTT Microelectronics Research Center of Finland
F. Gao, VTT Microelectronics Research Center of Finland
J. Kyynäräinen, VTT Microelectronics Research Center of Finland
J. Kiihamäki, VTT Microelectronics Research Center of Finland
Correspondent: Click to Email
This work examines the accumulation of heat and resulting increase in local temperature and loss of selectivity which may occur when etching high aspect ratio structures in SOI wafers with buried cavities. It is shown that unlike high-load, high-rate etches treated elsewhere, in the case of HAR etches the heat is generated mainly by ion-bombardment. Due to the presence of a cavity beneath the structures being released, which typically include a mass suspended by springs, the heat may only be conducted laterally away from the released structures to the surrounding device layer. During the final stages of DRIE etch and overetch, the heat flow from suspended masses is therefore restricted to occur along the springs which attach the mass to the surrounding device layer. The limited heat conductance of long meander springs in particular is unable to remove the heat generated in suspended structures. As a result, the temperature of the suspended structures increases resulting in reduced fluorocarbon depositon upon them. That, in turn, results in a locally increased etch rate of the oxide mask on the suspended structures. The effects of releasable thermal anchors, which provide additional paths for heat conduction away from the suspended mass and therefore aid in the removal of heat, is also discussed.