A method for laser scribing first and second transparent electrically conductive layers deposited on respective opposing first and second surfaces of a transparent substrate, comprising:
- directing a first laser beam through one or more lenses to a focal spot on or closely adjacent to the first surface of the substrate such that an energy density of the first laser beam is higher at the first surface of the transparent substrate than at the second surface of the transparent substrate, the first surface of the substrate being located on a far side of the substrate relative to the first laser beam such that the focusing laser beam passes through the second electrically conductive layer and the second surface of the substrate;
- initiating relative movement between the first laser beam and the substrate in two axes in a plane orthogonal to the axis of the first laser beam to scribe a first pattern in the first electrically conductive layer;
- directing a second laser beam through one or more lenses to a focal spot on or closely adjacent to the second surface of the substrate such that an energy density of the second laser beam is higher at the second surface of the transparent substrate than at the first surface of the transparent substrate, the second surface of the substrate being located on a far side of the substrate relative to the second laser beam such that the focusing laser beam passes through the first electrically conductive layer and the first surface of the substrate;
- and
- initiating relative movement between the second laser beam and the substrate in two axes in a plane orthogonal to the axis of the second laser beam to scribe a second pattern in the second electrically conductive layer;
- wherein the first laser beam, the transparent substrate, and the first and second electrically conductive layers are mutually selected such that the threshold energy density at which the first laser beam is operable remove the first electrically conductive layer from the substrate is lower than the threshold energy density at which the first laser beam can remove the second electrically conductive layer from the substrate, and a first process window for the scribing of the first electric conductive layer with the first laser beam is greater than a process window for scribing the second electrically conductive layer with the first laser beam,
- the second laser beam, the transparent substrate, and the first and second electrically conductive layers are mutually selected such that the threshold energy density at which the second laser beam is operable to remove the second electrically conductive layer from the substrate is lower than the threshold energy density at which the second laser beam can remove the first electrically conductive layer from the substrate, and a second process window for the scribing of the second electrically conductive layer with the second laser beam is greater than a process window for scribing the first electrically conductive layer with the second laser beam,
- where the process window is defined as the range of focal positions of the laser beam relative to the target electrically conductive layer to be scribed, over which the laser beam can scribe the target electrically conductive layer without scribing the opposing electrically conductive layer, and
- the first and second laser beams, the transparent substrate, and the first and second electrically conductive layers are selected such that the first and second process windows each exceed a height variance of a respective transparent substrate surface in a height direction and/or exceed a height variance of the position of the focal plane of the respective first and second laser beams, the height direction being perpendicular to a respective substrate surface.