Design and fabrication of lens selectively coated with TFMG for uniform intensity of UV LED

Abstract

This UV LED lighting technology developed in this study is expected to be applied to photolithography industry. Since the accuracy of the degree of cross linking and sidewall profile could be affected by intensity of UV light dosage, this research proposes optical design and fabrication of free-curved lens for light source element of UV LED for exposure machines. In this study, the optical intensity distributions of the lens with TFMG were determined by using commercial optical simulation FRED software. Based on the design, the lenses were fabricated using thermoforming of optical glass and PMMA, respectively. Then the lens is selectively coated with thin film metallic glasses (TFMG, Ag30 Mg45 Al25). For the TFMG coating, multi-target sputtering system is applied to sputter TFMG reflecting film on the surface of lens with thickness of 100 nm to 300 nm. With the both design of TFMG selective deposition and lens curve, the optical field of Lambertian emission patterns of UV LED can be transformed to uniform profile. Through this design of reflection of UV LED light source, the intensity and uniformity could be enhanced. UV LED light source with 360 to 390 nm in wavelength was chosen as light source to simulate the effects of I-line and G-line. The specific wavelength of UV light is measured by spectrometer (USB2000+VIS-NIR, Ocean Optics) and BM7.