Optimization of deep wet etching borosilicate glass substrates technological process for biomedical applications

The paper presents a microcells on borosilicate glass substrate fabrication technology for used for biomedical applications. The fabrication technology improved the standard lithography and wet chemical etching processes. We have studied the masking layer and the etching solutions which allow obtaining a 90% light transmission in a large optical range (180-2500 nm) and a low optical absorption. The diameter of a cell is 20 /spl mu/m and the depth between 4-8 /spl mu/m. The best results were obtained using Cr/Au as masking layer and KOH 7M as etching solution for the borosilicate glass.

1. INTRODUCTION

Due to the advantages that can be obtained, in microsensor and rnicroactuator technologies (diffractive elements), various types of glass are widely used. Glasses can be microstructurable, are transparent in a large range of wavelengths, are good as insulating substrates (specific electrical resistivity of at 20^QC) and are compatible with many different metals, The main requirements asked for glass in microsystem technology are: ◆

should be microstructurable, preferably using a standard lithography process;

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contains easily movable ions to perform anodic bonding;

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has a low thermal expansion coefficient in order to avoid thermal stress.