Time-Multiplexed Deep Etching

In time-multiplexed deep etching (TMDE), the etching and passivation gas monomers are flowed independently one at a time during operation. First, the etch step (normally <12 s) forms a shallow isotropic trench in the silicon substrate. Second, the passivation cycle (normally <10 s) forms a protective film on all the surfaces. In the subsequent etching step, ion bombardment promotes the preferential removal of the film on the horizontal surface and further isotropic etching of silicon, allowing the profile to evolve in a highly anisotropic strucmre (Fig. 5). 

Fabrication of 3D Microfiuidic Structures, Fig. 5 Four process steps for time-multiplexed deep etching (a) isotropic etching of silicon (b) polymer passivation (c) removal of formed polymer film on the horizontal surfaces (d) further isotropic etching of silicon... 

Laermer and SchUp of Robert Bosch GmbH originally invented a fluorine-based chemistry process [5], which maintains verticality (anisotropy), by using the concept of alternate etch and passivation steps, which is also called the time-multiplexed deep etching (TMDE) [6]. 

Time-multiplexed deep etching (TMDE) is a special deep reactive-irai etching (DRIE) process and has been commcmly applied in inductively coupled plasma (ICP) etching systems for anisotropic etching and 3D microstructiu e fabricatimi. 

One way to fabricate such a reactor is by deep reactive ion etching (DRIE) with a time-multiplexed inductively coupled plasma etcher (most details on fabrication are given in [77]) [7, 77, 78]. Regions of major importance such as the retainers are etched through to avoid differences in stmctural depth which may cause uneven flow. To generate various channel depths in one design, both front-side and back-... 

DRIE (Deep reactive ion etching) Advanced silicon etching (ASE ) Bosch process Switching etching Multiplexed time etching... 

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