Maskless Laser Patterning of Insulating Films from Salt Solutions

Maskless Laser Patterning of Insulating Films from Salt Solutions

      Maskless thin insulating films are deposited using a focused
argon ion laser (514 nm) directed onto a substrate submerged in a
nickel salt solution.  Both electrolytic and electroless solutions
have been used successfully.  Deposits occur only where the laser is
incident at the electrolyte/substrate interface.  For optimum
results, the laser light should not be absorbed by the solution but
strongly absorbed by the surface of the substrate.  Laser power is
adjusted so that the focused incident beam is at a power level just
below that which causes boiling of the solution at the point of focus
on the substrate.  With appropriate laser focusing lenses, patterns
as thin as 25 nm and as narrow as 3 microns can be obtained in the
form of spots and lines.  The insulating dielectric films have been
deposited from an electrolytic solution, nickel sulfate with sodium
citrate, as well as electroless nickel solutions using sodium
hypophosphite as the reducing agent.  Thicker patterns can be
obtained by adjusting laser dwell time and/or the use of multiple
laser scans.  The deposition mechanisms have been studied and appear
to be quite generic, thus not limiting the solutions from which
insulating films can be obtained to those mentioned herein.