This excellent paper “A maskless photolithographic prototyping system using a low-cost consumer projector and a microscope” explains how to build a cheap lithography system whose main parts are a microscope and a DLP projector. The system is claimed to support multiple layers up to a resolution of 10 microns.
The use of a DLP projector as image source elegantly and cheaply solves the problem of multilayer alignment.
Chosen excerpts from the paper:
“This overlay technique is easy to implement by placing the overlay in the master-slide mode of presentation software such as PowerPoint.”
“Creation of exposure slides using presentation software is easy. A typical slide show consists of a sequence of slides, with the design projected first in red for alignment and focusing, followed by a blue exposure slide for a controlled time, followed by a new red image to align the next pattern.”
“Students have used this system for a variety of research projects and upper-division laboratory exercises. These have included making optical diffraction patterns, catalyst pads for the growth of carbon nanotubes, and a variety of micron-scale symbols and signs. We have our used our thin-film evaporator in combination with this process to make metal patterns using the liftoff technique, where metal is deposited on the patterns made in the photoresist, and the remaining photoresist is then dissolved, leaving metal patterns stenciled on the substrates. Such films allow millimeter-scale electrical contact pads to be made for micron-scale objects such as thin-film resistors and long carbon nanotubes. Metal patterns on glass substrates should be suitable for creating custom two-dimensional binary diffractive optical elements similar to those used with inexpensive laser pointers.”