GaAs micromachining in the 1 H₂SO₄:1 H₂O₂:8 H₂O system. From anisotropy to simulation

Institut FEMTO-ST, Département Temps-Fréquence, 26 chemin de l'Épitaphe, 25030 Besançon Cedex, France

Corresponding author: ctellier@ens2m.fr

Received: 21 April 2010
Accepted: 14 September 2010
Published online: 28 January 2011

Abstract

The bulk micromachining on (010), (110) and (111)A GaAs substrates in the 1 H₂SO₄:1 H₂O₂:8 H₂O system is investigated. Focus is placed on anisotropy of 3D etching shapes with a special emphasis on convex and concave undercuts which are of prime importance in the wet micromachining of mechanical structures. Etched structures exhibit curved contours and more and less rounded sidewalls showing that the anisotropy is of type 2. This anisotropy can be conveniently described by a kinematic and tensorial model. Hence, a database composed of dissolution constants is further determined from experiments. A self-elaborated simulator which works with the proposed database is used to derive theoretical 3D shapes. Simulated shapes agree well with observed shapes of microstructures. The successful simulations open up two important applications for MEMS: CAD of mask patterns and meshing of simulated shapes for FEM simulation tools.