A low-cost, open-source maskless photolithography stepper for microfabrication

Abstract

Photolithography is a key part of modern semiconductor process flows, and photolithography steppers have been used for decades to achieve precise patterning for device fabrication. However, these tools are often large and expensive, which restricts their use to industry and well-funded university laboratories. In this paper, we propose a \$3000 maskless photolithography stepper that is affordable, open-source, and easy to assemble. The stepper, which uses a Digital Light Processing (DLP) projector as its optical engine, is able to achieve an optical resolution of under 2 microns. The stepper also features a motorized nanopositioning system, which is able to align features with sub-micron precision. RF-DETR, an object detection computer vision model, is used to detect fiducials on chip for automatic fine-grain alignment and stitching of patterns. These capabilities allow for use of the stepper for microfabrication to produce micron-scale devices such as NMOS transistors.