Fabrication of textured poly-crystalline silicon films from amorphous-silicon (a-Si) films using a line beam is investigated. The mechanism of laser annealing and simultaneously form a nano-textured surface using an Nd3+: YAG laser at a wavelength of 355 nm with a line beam is discussed. Amorphous-Si films coated on glass and crystalline silicon substrates were treated with different laser fluence from 100 to 600 mJ/cm2 and with 90% beam overlap. The crystallization and texturization characteristics were analyzed through SEM, Raman Spectroscopy, AFM, resistance and absorbance measurements. Generation of polycrystalline textured peaks was confirmed with different characterization methods and compared with the results of the conventional circular beam. This approach of line beam with increase in the scanning speed will allow the faster production of polycrystalline silicon from a-Si for photovoltaic application.

Nilesh Jayanthilal Vasa

Department of Engineering Design

Makaram Singaperumal

A-SI FILMS

Laser annealing

LASER TEXTURING

LINE BEAM

Photovoltaic

YAG LASER

Amorphous films

Annealing

GLASS LASERS

Laser applications

Manufacture

Microelectronics

Neodymium

Photovoltaic effects

Polycrystalline materials

Polysilicon

Raman spectroscopy

Semiconducting Silicon Compounds

Amorphous silicon

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Investigation on solid state Nd3+:YAG line beam laser annealing and texturing of amorphous silicon thin films

Proceedings of SPIE - The International Society for Optical Engineering

Influence of wavelengths and beam profiles of a pulsed Nd3+:YAG laser on the formation of a polycrystalline-silicon (poly-Si) on a-Si thin film is investigated. Two sets of samples of amorphous-Silicon (a-Si) thin films deposited on glass (a-Si/glass) and crystalline Si (a-Si/c-Si) substrates were treated with different laser-fluence values. After the laser treatment, the films were analyzed by a scanning electron microscope, the Raman spectroscopy technique and the resistance-measurement technique. In the case of the third harmonics (355 nm) of the Nd3+:YAG laser, poly-Si films were obtained with laser-fluence values ranging from 260 mJ/cm2 to 560 mJ/cm2, where as in the case of the second harmonics (532 nm), the process window for the formation of poly-Si films, in terms of the laser fluence, was ranging from 300 mJ/cm2 to 480 mJ/cm2. On the other hand, in the case of samples treated with the fundamental wavelength (1064 nm), a narrow process window with higher laser-fluence values around 1100 mJ/cm2 was observed. Further, the substrate was also affected because of the higher laser-fluence value. It has also been observed that the crystallization characteristics of poly-Si films improved with the flat-top intensity distribution as compared to the Gaussian intensity distribution of the Nd3+:YAG laser beam. A theoretical simulation based on thermal modeling was performed to understand the mechanism of crystallization. © 2009 Elsevier B.V. All rights reserved.

Thin Solid Films

Influence of laser wavelength and beam profile on Nd3+:YAG laser assisted formation of polycrystalline-Si films

Efficient doping of amorphous silicon(a-Si) is a key issue in the field of photovoltaic applications. In this paper an attempt has been made to produce a highly highly textured Sb doped a-Si. The a-Si were coated with Sb to a thickness of 200nm using vacuum evaporation method and treated with an Nd:YAG laser of 355nm with a threshold fluence of 460mJ/cm2 by overlapping the laser spots to 90% of its size. The samples are retretaed with a low laser fluence of 230mJ/cm2 respectively so as to crytsallize and diffuse the Sb on to the surface and to activate the dopant. The laser doped and subequently laser textured samples were analysed through Scanning Electron microscope (SEM), X-ray diffraction (XRD) &amp; Atomic Force Microscope(AFM).The traces of SiSb in the XRD peak with improved surface roughness were observed on the laser doped samples. This represents that the dopants are highly diffused on the a-Si. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Investigation on production of highly textured Sb doped polycrystalline silicon using solid state Nd: YAG laser for photovoltaic application

Development of textured crystalline silicon from amorphous silicon film using a pulsed Nd3+:YAG laser is reported. The technique involved is laser annealing and subsequent laser nano texturing by over lapping the laser spot by 50% and 90% of the diameter. Experimental investigations were performed using third (355 nm), second (532 nm) and fundamental harmonics (1064 nm) of the pulsed Nd3+:YAG laser. To investigate the texturization AFM measurement was performed. Absorbance and photoconductivity measurements were performed to analyze the photovoltaic properties of thin films. The process was theoretically analyzed using a 3-D heat transformation model in FEMLAB software. 355 nm laser assisted nano-texturing with 90% overlap showed an improvement in crystalline property and improved textured surface with a higher absorbance as compared to that of 50% overlap.

Fulltext

Journal of Laser Micro Nanoengineering

Investigation on laser-annealing and subsequent laser-nanotexturing of amorphous silicon (a-Si) films for photovoltaic application

In the present research, an approach of converting amorphous-silicon (a-Si) thin films into polycrystalline thin films using the third harmonics of an all-solid-state pulsed Nd3+:YAG laser (355 nm) is studied. Two different samples of a-Si thin films on alkali-free glass (a-Si/glass) substrates and a-Si thin film on crystalline-Si substrates (a-Si/c-Si) are laser treated at different laser fluences ranging from 170 to 960 mJ/cm2. The amount of heat incident on the surface has been analyzed theoretically by solving the one-dimensional heat-equation model. The ablation threshold, the region of crystallization and the depth of crystallization have been investigated theoretically. The influence of laser irradiation, ablation and crystallinity has been experimentally analyzed through in-situ reflectivity measurements, scanning electron microscopy (SEM) and Raman spectroscopy studies. In the case of a-Si/c-Si, the extent of crystallinity and the influence of structural characteristics on electronic properties are studied using the Hall-effect technique. The ablation threshold and the range of crystallization regime are in good agreement with the theoretical results. Laser fluence between 300 and 500 mJ/cm2 is required for crystallization and the ablation threshold is estimated to be above 500 mJ/cm2 for a-Si thin film with a thickness up to 400 nm. © 2009 Elsevier Ltd. All rights reserved.

Materials Science in Semiconductor Processing

Crystallization and ablation in annealing of amorphous-Si thin film on glass and crystalline-Si substrates irradiated by third harmonics of Nd3+:YAG laser

Surface and Coatings Technology

Surface-nano-texturing by aluminum-induced crystallization of amorphous silicon

Investigation on solid state Nd3+: YAG line beam laser annealing and texturing of amorphous silicon thin films

Journal	Proceedings of SPIE - The International Society for Optical Engineering
ISSN	0277786X
Open Access	No