Micromachining PV materials with time domain tailored laser pulses

Abstract

Novel laser micromachining processes are finding their way into more and more industrial applications. New wavelengths, shorter pulse durations, increasing reliability and decreasing costs are just a few of the parameters driving this growth. Traditionally, finding the optimal laser process parameters for new applications has been problematic and has often required the development of new lasers. Furthermore very little attention was given to the subtleties of the temporal distribution of energy within a single laser pulse because it was not an adjustable parameter. However, a new Master Oscillator Power Amplifier (MOPA) fiber laser architecture has emerged recently that overcomes these limitations. Now a single laser platform can not only address a huge range of applications but also provides precise control over the temporal distribution of laser energy within a given pulse. In this paper we discuss three applications where very specific temporal laser pulse shapes have markedly improved or enabled a process. First of all, we demonstrate the importance of energy distribution within the laser pulse to successful thin film scribing in the CIGS P2 and P3 processes. Secondly, we tailor the laser pulse shape to initiate and drive a chemical decomposition process to completion in a thin film while not overheating and damaging the substrate or other underlying film layers for the CdTe P1 scribing process. Finally, we study the impact of generating a pre-pulse to modify the absorption properties of silicon in advance of a higher energy machining pulse. In all three applications we find that tailoring the laser pulse shape to the process provides a significant benefit over processing with conventional laser pulse shapes.