Maskless photolithography based on ultraviolet micro-LEDs and direct writing method for improving pattern resolution.

Area of Science:

• Optoelectronics
• Nanofabrication
• Photolithography

Background:

• Maskless photolithography systems utilizing micro-light-emitting diodes (micro-LEDs) are emerging but lack comprehensive studies on system parameter effects.
• Existing methods for high-resolution patterns often involve reducing micro-LED pixel size, leading to technical challenges and increased costs.

Purpose of the Study:

• To develop and investigate a maskless photolithography system using 375 nm micro-LEDs for creating micrometer-sized exposure patterns.
• To systematically analyze the impact of system parameters (exposure time, current density, stage velocity, pulse width) on static and dynamic direct writing patterns.
• To propose and validate an oblique direct writing method to enhance pattern resolution without reducing micro-LED pixel size.

Main Methods:

• Development of a maskless photolithography system employing 375 nm peak wavelength micro-LEDs.
• Systematic exploration of static direct writing parameters: exposure time and micro-LED current density.
• Systematic exploration of dynamic direct writing parameters: stage velocity and current pulse width.
• Implementation and testing of an oblique direct writing method involving sample tilting.

Main Results:

• Established the influence of exposure time and current density on static direct writing patterns.
• Determined the effect of stage velocity and current pulse width on dynamic direct writing patterns.
• Demonstrated that increasing sample tilt angle (15° and 30°) reduced linewidths by 4.0% and 15.2%, respectively, confirming improved resolution.
• Showcased the potential of the oblique writing method to correct optical distortion errors.

Conclusions:

• The developed micro-LED maskless photolithography system effectively produces micrometer-sized patterns.
• The oblique direct writing method offers a viable and cost-effective approach to enhance pattern resolution in micro-LED photolithography.
• This technique holds promise for applications in printed circuit boards (PCBs), photovoltaics, solar cells, and micro-electro-mechanical systems (MEMS).