High-power modular LED-based illumination systems for mask-aligner lithography

Abstract

Mask-aligner lithography is traditionally performed using mercury arc lamps with wavelengths ranging from 250 nm to 600 nm with intensity peaks at the i, g and h lines. Since mercury arc lamps present several disadvantages, it is of interest to replace them with high power light emitting diodes (LEDs), which recently appeared on the market at those wavelengths. In this contribution, we present a prototype of an LED-based mask-aligner illumination. An optical characterization is made and the prototype is tested in a mask-aligner. Very good performances are demonstrated. The measured uniformity in the mask plane is 2.59 ± 0.24 % which is within the uniformity of the standard lamp. Print tests show resolution of 1 micron in contact printing and of 3 microns in proximity printing with a proximity gap of 30 microns.

Printing sub-micron structures using Talbot mask-aligner lithography with a 193 nm CW laser light source

“…Furthermore, we demonstrate Talbot lithography printing in higher Talbot planes [m > 1 in Eq. (8)]. Such an approach has the following advantage: The period can be reduced, i.e., a higher resolution is achieved, while at once the proximity gap can be increased with respect to the first Talbot plane.…”

“…The integration of LED and diode laser light sources into mask-aligner lithography has been demonstrated [6][7][8], solving the task of beam shaping for uniform mask illumination in various ways. Recently, we reported on the implementation of a novel deep ultraviolet (DUV) frequencyquadrupled continuous wave (CW) light source emitting at λ = 193 nm in a mask-aligner and demonstrated test exposures [9].…”

Compact ultraviolet light-emitting diode-based lithography illumination system with tunable coherent factor

“…4 Hence, the chip-on-board UV light-emitting diode (UVLED) array is gradually becoming an effective alternative light source for the stepper lithography system or mask aligner due to its long life cycle and high flexibility. 5,6 For years, the illumination system has always been a crucial modified point for optimizing the performance of UVLED-based lithography devices, especially for the improvement of the collimation system due to the Lambert divergence angle of the UVLED directly generating stray light or a ghost image without collimation. 7,8 To solve this issue, researchers have introduced various methods, such as the application of an optical spherical lenses, 9 reflective bowl, 10 total internal reflection lens, 11 and freeform lens.…”

“…Despite its prominent UV intensity, the high-voltage mercury lamp has a number of problems, such as a short life cycle and preheating requirement 4 . Hence, the chip-on-board UV light-emitting diode (UVLED) array is gradually becoming an effective alternative light source for the stepper lithography system or mask aligner due to its long life cycle and high flexibility 5 , 6 …”

Lau Effect Using LED Array for Lithography

“…In the application of mask aligner lithography, an LED is qualified due to its low electrical power consumption, long lifetime, and free and easy switchability, etc. [6,7]. An LED array is more advantageous than a single LED due to its high output optical power [8], saving exposure time such that the disturbance from the environment is reduced.…”