Laser TCO Patterning

Laser Processing Optical Thin Films

Common to all Flat Panel Displays (FPD) and Solar Cells and Panels technologies is the Transparent Conducting Oxide (TCO) thin film made of Indium Tin Oxide (ITO). The ITO serves as transparent circuit interconnects on the back plane for column and row drivers between transistor and pixel, or front panel in touchscreens offering conductivity and light transmission. Commonly, the complex pattern is generated using photolithography and is the most widely used system by industry manufacturers. Through a series of masking, exposure and wet chemical etching processes the ITO is patterned before continuing into subsequent stages of the device fabrication. Some of the key disadvantages of photolithography that laser processing does not have is the tooling costs, the ability to change batch run cost effectively and in a timely manner.

TCOs are largely deposited onto glass and are recently seen to be rapidly growing in applications which use plastic for thin film technologies such as Photovoltaic (PV), Organic display (OLED) and flexible electronics such as Electroluminescence (EL). As an alternative to wet chemical etching laser processing TCO is the direct write of patterns in a single step process. Laser processing TCO involves the laser ablation of material which subsequently reduces time and waste whilst offering flexible manufacturing in a cost effective and environmentally sustainable way. The nano-second Diode Pumped Solid State (DPSS) laser offers depth and line width control ideally suited for Thin Film removal from the front or back of the panel where the laser process is taking advantage of the transparent properties of the substrate.

The Diode Pumped Solid State (DPSS) lasers employed by M-Solv can be easily manipulated by a galvanometer scanner and focused laser beam onto a substrate.  The focus of the laser beam can then be moved at high speed around on the surface of the substrate in order to 'direct write' a patternin the TCO.  Laser processing TCO using ablation (an instantaneous vapourisation of material), material is removed either in the form of a thin film by scribing micro machined features using advanced lithography.

A common application for laser processing TCO is typically in processing coated glass panels for the display or photovoltaic or solar industries.  By laser processing TCO tracks of material in a circuit structure may be written without the need to use multi step chemical etching.