Fabrication of microlens array using backside exposure and DMD-based grayscale lithography

Area of Science:

• Optics and Photonics
• Microfabrication Technologies
• Materials Science

Background:

• Microlens arrays are crucial optical components in various applications.
• Traditional fabrication methods face challenges in achieving precise aspherical profiles and scalability.
• Digital micromirror devices (DMDs) offer potential for maskless, high-resolution patterning.

Purpose of the Study:

• To develop and demonstrate a novel DMD-based grayscale ultraviolet (UV) lithography system for fabricating aspherical microlens arrays.
• To investigate the efficacy of an oblique stepping method for precise UV dose control.
• To enable direct fabrication using negative-tone photoresist (PR) materials on transparent substrates.

Main Methods:

• Implementation of a grayscale UV exposure system utilizing a digital micromirror device (DMD).
• Employment of an oblique stepping method, tilting the DMD array during step-by-step exposure.
• Utilizing backside UV patterning on a transparent substrate for direct negative-tone PR processing.
• Theoretical analysis, numerical modeling, and experimental validation.

Main Results:

• Accurate shaping of aspherical microlens array profiles achieved through controlled UV dose distribution.
• High spatial resolution patterning enabled by the DMD and oblique stepping approach.
• Successful fabrication of microlens arrays using negative-tone photoresist materials.
• Demonstrated feasibility of the proposed backside UV patterning technique.

Conclusions:

• The DMD-based grayscale UV lithography system with oblique stepping is a viable method for fabricating high-quality aspherical microlens arrays.
• The backside patterning approach simplifies the fabrication process by allowing direct use of negative-tone PR.
• This technique offers a scalable and precise solution for advanced optical component manufacturing.