Indium tin oxide (ITO) is an optoelectronic material that is applied widely in research and industry because of its two main properties: its electrical conductivity and optical transparency. ITO can be used for many applications, such as fat-panel displays, smart windows, polymer-based electronics, thinfilm photovoltaics, glass doors of supermarket freezers, and architectural windows. Moreover, ITO thinfilms for glass substrates can be helpful for glass windows to conserve energy.

Depending on the application, the ITO layer (commonly with a thickness of hundreds of nanometer) needs to be removed with high precision and without substrate damaging to create electrical circuits. Laser ITO removal has been used during last decades as provides very good results in terms of quality and throughput.

For microelectronic applications the needs to increase the density of the circuits force the use of UV laser sources with very short focal lengths generating the following problems depending of the technology used:

Direct Galvanometer processing: The use of very short focal telecentric lengths provides access to areas of a few mm2. For large areas the process forces to move ITO panel with XY stages
synchronized with the Galvanometer. The method of Step and Repeat produces Stitching errors and the use of IFV (infinite field of view) synchronized with XY stages and Galvo movements is today very complex to program for all situations.

Direct XY table processing: High process time due the needs to limit the acceleration and speed to reduce inertia and vibrations during the process. Another problem is the complete
laser beam-pointing including the drift of all opto-mechanical components generating high repeatability errors when the process time is high, for example, scribing two parallel lines
separated 3 microns after 12 hours running is almost impossible due the components drift and laser beam pointing errors, providing short circuit problems in many cases.

In order to provide a simple solution, LASING has developed a process that synchronize the laser and ultra-precise XYZ stages with advanced electronics that translate the complex XY trajectories to a ultra-high resolution raster process.

Conclusion: The raster process using high resolution stages and special signal synchronization provides control of the laser pulse position with an error of less than 200 nm with the following
benefits:
1) unlimited area (XY stages stroke).
2) No stitching errors.
3) Very low and constant pulse to pulse jitter.
4) No thermal or laser accumulation in corners as the speed is always constant.
5) No shape limitation (any “equivalent spot” can be made as
the sum of pixels).

Written by Lasing Custom Laser Solutions

Compatible products: LS-fPRO & LS-COMPACT