idonus UV-LED exposure system for photolithography

illustration UV EXP series

idonus proposes an innovative UV illumination system based on the use of high-power LEDs and high-grade homogenization optics. This product finds application in photoresist exposure and is suitable for a wide variety of substrates and photoresists used in MEMS, microfluidics, photonics, semiconductors and photovoltaic applications. Our complete line of UV illumination products addresses photolithography needs for masks and wafers up to 300 mm wide (11.8 inches). Customized solutions can be designed to suit your specific requirements (e.g., retrofit of mask aligners, OEM for your future products).


Until recently, 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-LEDs have become a very attractive alternative to the hazardous and 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. As a result, daily calibration and maintenance are not required. Furthermore, by being more energy efficient, LEDs have reduced heating, which greatly simplifies system cooling.


Benefits of UV-LED technology
  • long lifespan of LEDs, meaning no more consumable required
  • no daily calibration required, instantly stable illumination
  • instant-on, light is ON only during exposure, no mechanical shutter needed
  • low power consumption
  • narrow spectrum: no unwanted heating of the substrate and more repeatable process
  • no maintenance costs


idonus has introduced a complete line of UV-LED exposure products. Our systems integrate the most effective UV-LEDs available on the market together with high-grade microlens arrays. They are fully assembled and controlled in-house. Our design features a fully telecentric optics that provides reproducible and uniform illumination conditions over the whole exposure area – i.e., highly uniform and stable intensity with very small divergence angles. This cutting edge optics ensures perfectly uniform exposure of the entire substrate, producing cured photoresists with straight sidewalls and enabling precise microstructuring of patterns with micrometer critical dimensions.

optical system
Figure A: Optical system (simplified) • High uniformity of the illumination is achieved thanks to the use of a microlens array homogenizer.



Our UV-LED exposure system is available in several standard configurations that can be customized with a multitude of variations (e.g., single or  mixed wavelengths). As a manufacturer of special machines, idonus can also develop fully customized equipments according to client's specifications (e.g., different exposure area, adapted equipment housing). The main characteristics of our products are given in Table "Standard UV-LED exposure systems". A typical measurement performed during the calibration process is shown in Figure B. In the usable exposure area, irradiance non-uniformity, (max-min)/(max+min), is lower than 3%. The maximum collimation angle α which is illustrated in Figure A is another important parameter that we systematically characterize. Data shown in Figure C are typical results extracted from measurements performed on one of our models. To evaluate α, irradiance is measured as a function of the collimation angle: α corresponds to the FWHM (full width at half maximum). This threshold is commonly used to consider light energy effectively contributing to photoresist irradiation. Given the performance of our exposure system, about 95% of the energy is enclosed within the collimation angle.


Table: Standard UV-LED exposure systems • Typical specifications of our standard products that are optimized for different exposure areas.

Characteristics \ System type UV-EXP150R UV-EXP150S UV-EXP200S UV-EXP300S UV-EXP600S
Useful exposure area Ø 150 mm 150 × 150 mm² 200 × 200 mm² 300 × 300 mm² 600 × 600 mm²
(single or mixed)
365 nm and/or 385 nm / 395 nm / 405 nm
all models can be configured with UV-LEDs with multiple wavelength peaks
(@385/395/405 nm)
50 mW/cm² 50 mW/cm² 30 mW/cm² 17 mW/cm² 30 mW/cm²
multiple LEDs
(@365 nm)
40 mW/cm² 40 mW/cm² 25 mW/cm² 12 mW/cm² 20 mW/cm²
multiple LEDs
(max-min)/ (max+min)
3% 3% 3% 3% 3%
Max. collimation angle
(±α, FWHM)
±1.8° ±1.8° ±1.4° ±1.0° ±2.0°
Working Distance (WD) * 350 mm 300 mm 400 mm 300 mm 300 mm
Ext. dim.
H × W × D
(lamphouse only)
610 × 302 × 244 mm
607 × 352 × 294 mm 728 × 412 × 354 mm 936 × 560 × 504 mm 1500 × 1100 × 900 mm
Ext. dim.
H × W × D
(complete system)
1000 × 480 × 330 mm 960 × 500 × 420 mm 1170 × 530 × 520 mm 1270 × 670 × 670 mm **

* Note that for all models, other WD can be designed to address your specific needs.
** To be defined, as it depends on user application.


uvlight result web graph 1
Figure B: Irradiance uniformity • Measurements show non-uniformity lower than 3%. Typical values extracted from one of our models UV-EXP100S (square illumination area of 100×100 mm²).


Figure UV EXP Angular spectrum

Figure C: Angular spectrum • UV light is enclosed within the max. collimation angle (intensity threshold at FWHM, corresponding to 95% of light energy). Typical values extracted from our UV-EXP150S (max. collimation angle α of ±1.8°).


 close up view UV EXP idonus
Detail view of model UV-EXP300S. Anti-reflective coating gives this distintive color to the front lens


photo 2
Highly uniform exposure over an area of 300 × 300 mm² is obtained with model UV-EXP300S.