Mask aligner lithography using laser illumination for versatile pattern generation

Abstract

Mask aligner lithography is a well-established back-end fabrication process in microlithography. Within the last few years, resolution enhancement techniques have been transferred and adapted from projection lithography to further develop mask aligner lithography, especially concerning achievable resolution. Nonetheless, current technology using a mercury vapor lamp as a light source has reached its limits, e.g. for high-resolution pattering. Within this paper, we present the extension of the existing mask aligner illumination system by replacing the mercury vapor lamp with a solid-state laser. Full-field mask aligner lithography is guaranteed by a rotating diffuser expanding the laser beam and minimizing undesired speckle effects. An additional integrated galvanometer scanner allows a flexible choice of arbitrary angular spectrum distributions of the photomask illumination. We show versatile results like simple binary patterns of squares and triangles, as well as a more complex lateral shape like a blazed grating.

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

“…In comparison, excimer laser sources for mask-aligner lithography have been demonstrated with an optical power of 7.5 W at 193 nm [4]. Weichelt et al reported on a pulsed solid-state laser source with an optical power of 3 W and emitting at a wavelength of 355 nm [7]. The laser output exhibits an elliptical beam profile, as depicted in the inset of Fig.…”

“…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].…”

New Illumination Technology for Mask Aligner Lithography

“…Instead of a uniform illumination of the IFPs followed by blocking out most of the light and only redistributing the residual irradiance homogenously over the photomask, the team now reversed the setup order. An InnoLas Photonics' NANIO 355-3-V laser now replaces the conventional light source [2] and no illumination filter plates are needed anymore. Instead, a galvanometer scanner produces any desired angular spectrum for illuminating the photomask, always using the full laser power.…”

“…Schematic overview of the new illumination system using the laser as an illumination source (a). A galvanometer scanner allows a flexible generation of angular spectra illuminating the photomask (b) [2]. …”

Femtosecond laser fabricated polymeric grating for spectral tuning

“…In this study, gratings with an epoxy-based negative photoresist (SU-8) are fabricated by direct writing with a Ti:sapphire femtosecond laser at a wavelength of 800 nm, a pulse width of 67 fs, and a repetition rate of 80 MHz (Libra system, Coherent Inc.). Conventional techniques to fabricate diffraction gratings include photo-masking [21], electron beam lithography [22], etching techniques [23], and holographic interference [24,25]. Holographic lithography/recording was developed to create periodic 3D microstructures, in which periodic interference patterns such as an aspheric microlens structure [26], microscopic tubular structure [27], and fast bits [28], are printed into the photoresist by multi-laser beam irradiation.…”