Maskless laser patterning of indium tin oxide (ITO) thin films was studied
by the use of a diode-pumped Q-switched Nd:YLF laser. The ITO films were sp
utter-deposited either on lime glass, the standard substrate material for h
at panel display applications, or fused quartz so that the efficiency of la
ser patterning as a function of substrate absorption could be studied. The
laser wavelength was varied among infrared (lambda = 1047 nm), visible (lam
bda = 523 nm), and ultraviolet (lambda = 349 nm and lambda = 262 nm). It is
observed that strong light absorption by the substrate is a crucial requir
ement for a residue-free patterning of the ITO film. Observations and numer
ical calculations of the laser-induced surface temperature indicate that ma
terial removal occurs via thermal vaporization and that other mechanisms su
ch as photochemical decomposition or spallation can be neglected.