Development of Uniform Ultraviolet Light Source using Light-Emitting Diode (LED) Array for Photolithography System with Controllable Exposure Dose and Duration

Abstract

This paper presents a simple and low-cost ultraviolet (UV) Light Emitting Diode (LED)-based light source with uniform and controllable light intensity for portable exposure photolithography process. The system can receive user-defined parameter values for exposure dose and duration time, controlled by the microcontroller through a LED driver circuit. The measurement results show that LED has a peak wavelength of 394 nm and very narrow full-width at half maximum (FWHM) of 12.59 nm. By rotating LED array, the UV light source can produce uniform irradiance at the average 82 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at near-zero contact, 51 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 1 cm, and 8 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 5 cm. We also found that exposure time and distance of the light source to the pattern greatly affect the results of the pattern transfer on the substrate. The smallest resolution that can be exposed in this study on the Printed Circuit Board (PCB) substrate with dimension 2 × 2cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is 100 microns. Using the developed UV-LED light source, it shows great potential as a low-cost light source and feasible applications for microfabrication.

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