Uniform areal-distribution of UV intensity by synchronizing signal-waveforms and position of a UV-LED array

Abstract

This paper describes a theoretical approach to give an irradiated area a uniform distribution of LED light intensity by synchronizing the signal waveforms and position control of the LEDs. Although UV-LEDs have attracted considerable attention as alternative light sources for ultraviolet (UV) lithography in Micro Electro Mechanical Systems (MEMS) fabrication, mainly because of their low cost and low power consumption, the realization of a uniform UV intensity over an area remains challenging. Here, we propose a method to achieve a uniform areal intensity within an irradiated area by synchronizing the signal waveform and position of a UV-LED array. To verify our theoretical calculation, we developed a system with a UV-LED array whose position is controlled by a linear actuator. The intensity of the UV-LED array is controlled by a pulse width modulation (PWM) signal, which is synchronized with the position of the linear actuator. Using this system, we fabricated 2D micropatterns and 3D microstructures with high uniformity in the irradiated area. The proposed method is expected to facilitate practical LED-based lithography in MEMS fabrication.

Development of a light source with a uniform intensity reinforced by a checkerboard half-mirror positioned within inverse L-shaped UV-LED arrays

“…In previous studies, rotating or linearly actuating a UV-LED array has been tested to ensure a uniform areal distribution of the light intensity. 9,10) Light collimation was also achieved by passing the UV light rays through an opaque lens tube. However, the methods require an actuator for driving UV-LED arrays.…”

“…The vibration of the UV intensity of the previous UV exposure system using a linearly actuated UV-LED array was within ±5%. 10) The uniformity of the UV intensity of a commercial mask aligner (Süss MicroTech MA=BA6) is less than ±3% in a 6 in. area.…”