A novel fabrication method of capillary tubes on quartz for chemical analysis applications

The concept of micro flow systems for chemical analysis integrated on silicon (Si) and quartz (SiO/sub 2/) substrates was investigated as an alternative to conventional chemical sensors. A commonly used manufacturing method for capillary tubes includes the etching of capillary channels in a silicon substrate, oxidation of Si and subsequent wafer bonding to form the capillary. A novel fabrication method to produce the capillaries in a wide range of dimensions on a quartz substrate is presented. The manufacturing sequence consists only of the standard steps of Very Large Scale Integration (VLSI) process: photolithography, oxidation, wet and dry etch and Low Pressure Chemical Deposition (LPCVD). Very well defined capillary tubes with the width from 10 mm to 200 mm were produced using this method. Resistance measurements performed on capillaries filled with KCl solution showed very good agreement with the theoretical calculations of the resistance values for given geometrical shapes. The original chip was designed and fabricated on quartz to investigate the effect of electroosmotic pumping of liquid. The first experimental results confirm the possibility of using this fabrication method to produce micro capillary systems for chemical analysis applications.