Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

Journal Article · Sat Mar 14 04:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4914457· OSTI ID:22399273

Heinrich, G. ^[1]; Wollgarten, M. ^[2]; Huber, H. P. ^[3]; Schmidt, M. ^[4]

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1. Technische Universität Ilmenau, Institut für Physik, Weimarer Straße 25., 98693 Ilmenau (Germany)
2. Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany)
3. Faculty of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstraße 34, 80335 Munich (Germany)
4. Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Photonische Technologien, Konrad-Zuse-Straße 3-5, 91052 Erlangen (Germany)

In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.

• OSTI ID: 22399273
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 10 Vol. 117; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABLATION
ABSORPTION
DAMAGE
DIELECTRIC MATERIALS
EFFICIENCY
ELECTROMAGNETIC PULSES
IRRADIATION
LASER RADIATION
LAYERS
NONLINEAR PROBLEMS
PHYSICAL RADIATION EFFECTS
REFLECTIVITY
SILICON
SILICON NITRIDES
SILICON SOLAR CELLS
SUBSTRATES
SURFACES
TRANSMISSION ELECTRON MICROSCOPY