idonus offers a wide range of LED-based UV exposure systems. These products are an efficient and durable alternative to mercury lamps which have traditionally been used for UV photolithography and curing.
With what similarity can the spectrum of a mercury-vapour lamp be reproduced with LEDs? Mercury-vapour gas-discharge lamps have a continuous spectrum with characteristic strong lines at 365.4 nm (i-line, UV-A ultraviolet), 404.7 nm (h-line, violet) and 435.8 nm (g-line, blue). On the other hand, LEDs have an easily recognisable Gaussian-type spectrum. LED semiconductors can be constructed to emit light at virtually any desired peak wavelength. By combining arrays of LED dies emitting at well-defined wavelengths, it is possible to construct a broadband high-power LED that mimics the useful spectrum of a mercury lamp. Moreover, the relative intensity of these peaks can be tuned independently.
To what extent can a high-power UV-LED replace a mercury lamp in a photolithography process? The question arises when considering the overall spectral irradiance and the output irradiance in the useful UV range. Understanding the origin of the spectral behaviour of LEDs, as well as the reasons why a simple photodiode can be used as a reliable radiometric instrument should be of interest to those considering replacing their old mercury-based system. It should also spark the interest of those already familiar with the use of UV-LEDs for their processes. These topics are fully covered in the White Paper that we have just released and which we are promoting in this newsletter.
