High Resolution Laser Photolithography for Fabrication of Specialized, Miniature Devices, 14-R8302
Principal Investigators
W. Royall Cox
Jerome A. Helffrich
John D. Harrison
Inclusive Dates: 04/01/12 – Current
Background — Developing custom devices of ever-decreasing size has been an ongoing activity for many years. The overall objective of this project is to expand significantly the process capabilities of SwRI's Advanced Electronics Laboratories to enable the creation of specialized circuits and sensors with smaller feature sizes and enhanced capabilities.
Approach — The primary processes to be optimized are laser micromachining, photolithography, and various combinations of these technologies. SwRI will upgrade the optics of the micromachining tool to reduce the minimum focal spot size of the UV (ultraviolet) laser, thereby enabling the fabrication of circuits having smaller circuit features. In conventional photolithography an optically sensitive coating (resist) is applied to the surface of the substrate then exposed to UV light through a mask to define an electrical circuit pattern (after subsequent development, etching and removal of the remaining resist). Each iteration of the pattern design requires a new, relatively costly, mask. SwRI will develop a laser writing process to create circuit patterns by exposure or removal of the resist, thereby eliminating the need for a mask. After optimizing the various device fabrication processes, SwRI plans to demonstrate its new capabilities by making three different types of miniature devices of potential interest to clients. The first will be a miniature ultrasonic transducer for broadband sound detection, which consists of a piezoelectric element attached to a multilayer copper/polymer circuit (as shown in the figure). The second will be a miniature electronic filter with dimensions as small as 160 microns. The last device will be a miniature quartz tuning fork scanning probe for detection of metal surfaces.
Accomplishments — The reduction in laser spot size was achieved, enabling the micromachining of features as small as 50 microns. Laser writing processes were developed for exposing or removing resist coatings ranging in thickness from 2 to 250 microns. A miniature transducer was developed, and work was begun on the miniature electronic filter.
