Microprocessing of ITO and a-Si thin films using ns laser sources

Abstract

Selective ablation of thin films for the development of new photovoltaic panels and sensoring devices based on amorphous silicon (a-Si) is an emerging field, in which laser micromachining systems appear as appropriate tools for process development and device fabrication. In particular, a promising application is the development of purely photovoltaic position sensors. Standard p–i–n or Schottky configurations using transparent conductive oxides (TCO), a-Si and metals are especially well suited for these applications, appearing selective laser ablation as an ideal process for controlled material patterning and isolation. In this work a detailed study of laser ablation of a widely used TCO, indium-tin-oxide (ITO), and a-Si thin films of different thicknesses is presented, with special emphasis on the morphological analysis of the generated grooves. Excimer (KrF, λ = 248 nm) and DPSS lasers (λ = 355 and λ = 1064 nm) with nanosecond pulse duration have been used for material patterning. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) techniques have been applied for the characterization of the ablated grooves. Additionally, process parametric windows have been determined in order to assess this technology as potentially competitive to standard photolithographic processes. The encouraging results obtained, with well-defined ablation grooves having thicknesses in the order of 10 µm both in ITO and in a-Si, open up the possibility of developing a high-performance double Schottky photovoltaic matrix position sensor.

UV laser-induced high resolution cleaving of Si wafers for micro–nano devices and polymeric waveguide characterization

“…The system has been used for several applications, mainly related with microprocessing materials such as amorphous silicon and ITO. In [12] are detailed these process besides the main characteristics of the system. Fig.…”

Laser applications in thin-film photovoltaics

“…The threshold fluence of various relevant materials have been measured by Compaan et al [8], whereas the pulse shape and the pulse overlap in TF Si technologies are discussed by Haas et al [9,10]. Molpeceres et al compare the p1 process at 1064 nm and 355 nm using a tin-doped indium oxide as front TCO [11,12]. In CdTe solar cells, all three processes can be in principle performed at 1064 nm, as the ablation threshold of CdTe at this wavelength-unlike a-Si:H or µc-Si:H-is lower than the ablation threshold of the TCO [8,13].…”

Laser structuring of thin-film solar cells on polymers

“…High repetition rate lasers with a short pulse duration offer new possibilities for high efficiency structuring of conducting, semi-conducting and isolating films. Various laser sources were tested in selective ablation of thin films [2][3][4][5][6]. The main limiting factor for laser processing of the multilayer CuInSe 2 structures is deposition of molybdenum on walls of channels scribed in the films, and the phase transition of semiconducting CuInSe 2 to metallic state close to the ablation area due to the thermal effect [4].…”