Direct-write grayscale lithography

Abstract

Grayscale lithography is used to produce three-dimensional (3D) structures on micro- and nanoscale. During the last decade, micro-optics and other applications were actively pushing the market demand for such structures. Direct-write systems that use lasers and heated scanning probes can be used for high-precision grayscale micro- and nanolithography. They provide solutions for the most demanding applications in research and industrial manufacturing. At both the micro- and nanoscale, though, some challenges remain, mainly related to throughput. Ongoing R&D efforts and emerging new applications drive several companies to join forces in order to meet the market demands for grayscale lithography of today and in the future.

Out-of-plane surface patterning by subsurface processing of polymer substrates with focused ion beams

“…Possible applications of the method for microoptical devices are discussed in detail in our previous work [4]. They include tuning the thickness of the dielectric layer in the metal-insulator-metal (MIM) structures used in linearly variable bandpass filters (LVBFs) [30][31][32][33]. The capabilities of PDMS substrates to induce multiscale surface curving are also very interesting regarding the manufacturing of photonic structures and microlens arrays.…”

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“…used in mobile cameras), patterned substrates for LEDs, diffractive optical elements, blazed gratings, waveguides, Fresnel lenses, functionalized smart surfaces etc. with micro-and nanometer dimensions is undeniable [1][2][3][4]. There are existing methods for the microfabrication of 3D microstructures such as high-precision mechanical milling with polishing, thermal reflow of the photoresists, mask-based grayscale lithography (GSL) etc.…”

“…However, the approach of mechanical milling is limited in terms of throughput and its resolution, which hinders the scalability for microfabrication of 3D microstructures. While, the thermal reflow method of photoresist, indeed results in realization of 3D geometries in photoresists; however, the system is complex to precisely model it for the realization of arbitrary shapes, thickness and sizes, and it is still under research [1,5]. Furthermore, the masked-based GSL has been reported for fabrication of 3D photoresist structures showing a gradient in their height; however, the requirement for the multiple masks and strict alignment needed to expose layouts makes this approach complicated, expensive and time consuming for the 3D exposures [1,3].…”

“…While, the thermal reflow method of photoresist, indeed results in realization of 3D geometries in photoresists; however, the system is complex to precisely model it for the realization of arbitrary shapes, thickness and sizes, and it is still under research [1,5]. Furthermore, the masked-based GSL has been reported for fabrication of 3D photoresist structures showing a gradient in their height; however, the requirement for the multiple masks and strict alignment needed to expose layouts makes this approach complicated, expensive and time consuming for the 3D exposures [1,3]. Besides, the use of GSL using direct writing laser (DWL) has been proven to be a promising technique for high throughput microfabrication of 3D microstructures at both micro-and nanoscale dimensions [1,[6][7][8].…”

“…Furthermore, the masked-based GSL has been reported for fabrication of 3D photoresist structures showing a gradient in their height; however, the requirement for the multiple masks and strict alignment needed to expose layouts makes this approach complicated, expensive and time consuming for the 3D exposures [1,3]. Besides, the use of GSL using direct writing laser (DWL) has been proven to be a promising technique for high throughput microfabrication of 3D microstructures at both micro-and nanoscale dimensions [1,[6][7][8]. The advantage of maskless exposure with the possibility of modulation of the laser exposure intensity (i.e.…”