A comparison of wet and dry etching to fabricate a micro-photonic structure for use in OCT

Paul Jansz; Graham Wild; Steven Hinckley

doi:10.1117/12.810973

30 December 2008 A comparison of wet and dry etching to fabricate a micro-photonic structure for use in OCT

Paul Jansz, Graham Wild, Steven Hinckley

Proceedings Volume 7270, Biomedical Applications of Micro- and Nanoengineering IV and Complex Systems; 727016 (2008) https://doi.org/10.1117/12.810973
Event: SPIE Smart Materials, Nano- and Micro-Smart Systems, 2008, Melbourne, Australia

Abstract

In conventional time-domain Optical Coherence Tomography (OCT), a moving mirror is used as a reference optical delay line. This motion can result in instrument degradation, and in some situations it is preferable to have no moving parts. Stationary optical delay lines using a variety of methods have been proposed. Of particular interest, due to its low cost, is the use of a micro-photonic stationary optical delay line, made up of an addressable Stepped Mirror Structure (SMS) using a liquid crystal optical switch. Here the individual steps of the SMS can be selected by the liquid crystal array. For use in OCT, the discrete nature of the SMS needs to be overcome by having the step height less than the coherence length of the low coherent light source. Typical coherence lengths in current OCT systems are on the order of 10μm. Hence, micrometer size steps require the use of a relevant fabrication method. In this paper, we compare SMSs fabricated using wet and dry etching methods. Specifically, Reactive Ion Etching (RIE) using CF₄/O₂ and chemical bath etching, using a solution of HF, HNO₃ and Acetic acid. Three inch diameter silicon wafers, 400μm thick, were etched by both methods. The RIE was used to produce a SMS with five 5μm high steps each step approximately 1 cm wide. The wet etching produced an SMS with three 15μm steps approximately 2 cm wide. The overall structures of the SMSs were compared using optical profilometry. The RIE step quality was far superior to the wet etch method due to the ability to control the anisotropy of the RIE method.

Citation Download Citation

Paul Jansz, Graham Wild, and Steven Hinckley "A comparison of wet and dry etching to fabricate a micro-photonic structure for use in OCT", Proc. SPIE 7270, Biomedical Applications of Micro- and Nanoengineering IV and Complex Systems, 727016 (30 December 2008); https://doi.org/10.1117/12.810973

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available