CW Line Laser for Large Area Material Refinement

In a constantly evolving laser industry new and innovative applications of laser radiation are emerging – in scope as well as in numbers. While pulsed line-shaped laser beams are already well established as mainstream manufacturing tools in the production of flat panel displays, continuous-wave line beam processes are still in their infancy. Nevertheless, they have shown great potential in research & development laboratories as well as in pilot plants for various thermal material processing applications.

Line-shaped continuous-wave laser crystallization of a 10 µm thin silicon film on a 3 mm thick glass substrate (Source: HZB / HySprint)

At Helmholtz-Zentrum Berlin für Materialien und Energie HZB, the Helmholtz Innovation Lab HySprint operates an open-access laser laboratory where it jointly investigates new and innovative ideas of its cooperation partners and comprehensively evaluates them using a variety of analytical measurement methods on site. Its partners benefit from their knowledge on material refinement and analysis. They focus in particular on large area continuous-wave line laser processing of materials. This type of laser sources and the associated manufacturing processes feature essentially unlimited scalability in terms of area and throughput at low costs. So far, the HySprint researchers concentrated their efforts on the crystallization of silicon films on foreign substrates offering such films with processes that are compatible to industrial mass production for applications requiring large area, high quality and low cost materials. However, they are open to explore a large variety of different materials.

Based on the available line lasers at the HySprint laser laboratory of HZB, all kinds of thermal material treatment can be supplied. The HySprint laser laboratory at HZB currently continues and expands the investigation of laser refinement of photovoltaic relevant materials that had been started in the past by the Institute for Silicon Photovoltaics at HZB. The main focus is on the crystallization and annealing of thin silicon films on foreign substrates. What started as a simple idea has evolved into a mature process and was the advent of the liquid phase crystallization (LPC) technology.

Silicon crystal grain structure created by cw line-shaped diode laser LPC treatment of a 10 µm Si thin film on 10 cm × 10 cm glass substrate. (Source: HZB / HySprint)

LPC technology offers a significantly lower cost per square meter compared to standard semiconductor industry grade silicon wafers plus the possibility to produce this material in large quantities on square meter sized, sub-millimeter thickness substrates using in-line manufacturing facilities. Thus LPC-Si sheets could make high end performance available to flexible and areal electronics end-use applications as diverse as, e.g., automotive, wearable electronics, industrial process engineering and illumination technology.

HZB’s Helmholtz Innovation Lab HySprint supports technology transfer of LPC and other technologies to industry by providing client-specific research and development support as well as cooperation and licensing agreements.
Laser crystallized LPC-Si is a potentially low cost and high performance semiconductor material that could be well-suited for flexible, planar electronic indoor and outdoor applications. It could support the megatrend of digitization by making available a new raw material that successfully bridges the gap between high end silicon wafers on the one hand side and low cost amorphous silicon thin films as well as printed electronics on the other hand side. (Source: HZB)

Reference: S. Kühnapfel, P. Harten, S. Gall: Continuous-Wave Line Laser for Large Area Material Refinement, Optik Photonik 13(4), 33-36, November 2018; DOI: 10.1002/opph.201800032

Link: Helmholtz Innovation Lab HySPRINT, Helmholtz-Zentrum Berlin für Materialien und Energie, HZB, Berlin, Germany


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