The aim of UV exposure system is to initiate the cross linkage by the activation of the PhotoActive Component (PAC) in some parts of the photoresist. This activation will change the local properties of the photoresist which after baking will be soluble or not soluble in a solvent.
There are some major parameters that must be taken into account while choosing a UV source for photolithography applications:
i) the power and the exposure time
ii) characteristics of the optical beam
iii) the light source type
iv) the variability in time and space.
Recently, the light source type has also became an important parameter, as earlier only mercury arc lamps were the only sources capable of providing high intensity light suitable for UV photolithography exposure. Thanks to the advances in LED technology, UV-LED lamps have become a very attractive alternative to the expensive and high energy-consuming mercury lamps.
Along with the ecological and security aspects, the technical advantages of UV-LEDs as compared with traditional mercury lamps are numerous and significant for photolithography. A foremost advantage of UV-LEDs is that they operate with consistent emission for very long lifetimes and with a light 100% monochromatic. As a result, daily calibration and maintenance are not required. Furthermore, by being more energy efficient, UV-LEDs have reduced heating, which greatly simplifies system cooling. In addition, unlike mercury lamps which need about 30 minutes to warm-up and stabilize before use, UV-LEDs are instant-start, and thus can be rapidly switched on and off. Finally, UV-LEDs have an average life time of 20.000 hours which is nearly 10 times longer when compared with mercury lamps.
SIMCO offers different solutions for UV Exposure.