Grayscale lithography, also known as 3D or 2.5D lithography, creates intensity gradients in photoresist which translate into a resist topography. Micro-scale grayscale microstructures can be shaped to become micro-lenses, diffractive optical elements, computer-generated holograms, MEMS/MOEMS, etc. Nanoscale 3D structures are important in photonics, nanofluidics or cell growth substrates. Grayscale micro- and nanostructures can be patterned directly onto the target substrate, or used as a master stamp for Nano-imprint Lithography. Heidelberg Instruments offers the most advanced grayscale lithography solutions covering all the range from large area microstructures (DWL 66+) to most precise 3D nanostructures (NanoFrazor Systems).
A diffraction grating optimized for efficiency at a particular wavelength and diffraction order shows an example of a typical Micro Optics application. Both the angle of the sawtooth-like profile and the groove spacing are tuned to match the specific application requirements. Blazed gratings are key components of many optical instruments, such as monochromators and spectrometers used in sensors, communication systems and other tools. Courtesy of IGI
Diffusers and reflectors
Retro-reflector structure was patterned using DWL66+. 2.5D micro-structures designed to control reflection or diffusion of light are used in light sources and illumination, like backlight units in LCD displays. Courtesy of karmic.ch
Compound micro- and nanostructures
“Moth eye” compound microlenses array replicated with nanoimprint technology shows DLW66+ capabilities for 2.5D patterning. Texturing surfaces using grayscale lithography can control and modify their hydrophobicity, friction, haptics, and adhesion. Courtesy of ShenZhen Nahum-Eli Optical Technology Inc.
Twin Gaussian profiles with varying distance ∆x written in PPA and etched into SiO2, to be stacked in distributed Bragg reflector. Cross-sections show Gaussian profiles for different ∆x, which controls the coupling strength between the cavities and the resulting photonic molecule. Precise Gaussian profile is patterned using the NanoFrazor and the closed-loop lithography approach. Courtesy of Armin Knoll at IBM Zurich
Fresnel micro-lenses are still a crucial component in today’s micro-optics and opto-electronics. Originally invented to reduce mass and volume of lenses used in lighthouses, Fresnel micro-lenses manufactured by grayscale direct-write lithography are used in mobile devices, enabling ultra-light and compact powerful cameras that fit in our pockets. Courtesy of HIMT
Brownian motors-based nanoparticle sorting device
Nanofluidic ratchets fabricated with single-nanometer accuracy by NanoFrazor patterning. A nanofluidic device with a precisely engineered 3D topography harnesses Brownian motion to separate particles with down to 1nm size difference by guiding them in opposite directions. Courtesy of IBM Research, Publications in Science and PRL 2018