Electron backscatter diffraction on femtosecond laser sulfur hyperdoped silicon

Abstract

This paper analyzes the impact of femtosecond laser pulse irradiation on the crystallinity of silicon wafers by means of electron backscatter diffraction (EBSD) measurements. EBSD based image quality maps and orientation imaging microscopy maps are correlated to the grade of the silicon crystallinity. We analyze the impact of accumulated net laser irradiation originating from a laser spot overlap that is necessary to process macroscopic areas, e.g., for sulfur doping of semiconductor devices. Furthermore, we demonstrate that post processing annealing recovers crystallinity and therefore allows fs-laser processed silicon to be used in semiconductor device manufacturing

Femtosecond-laser hyperdoping silicon in an SF6 atmosphere: Dopant incorporation mechanism

“…The area probed is small compared to the laser spot size (460-lm diameter) to minimize the spatial variation of the local laser fluence across the SIMS sample region (<1%). We record counts of 29 Si, 32 S, 34 S, 19 F, and 18 O, and the S and F counts are calibrated against known ionimplanted Si samples.…”

“…Gimpel et al show that the amorphous phase is also enhanced when scanning the laser pulses, as is commonly done when fabricating large-area hyperdoped Si. 19 For large area fabrication, the amorphous region could be minimized using a flat-top beam.…”

Current Concepts for Optical Path Enhancement in Solar Cells

“…Black Si surface textures consist of densely packed needle-like peaks and pits of irregular shape and high aspect ratios (see Figure 1.4(a)). Black silicon can be prepared by several methods such as metal-assisted wet-chemical etching, inductively coupled reactive ion etching (ICP-RIE), or short-pulse laser irradiation [11][12][13][14][15]. Another important advantage of b-Si over conventional pyramidal textures is the comparatively large feature sizes of the latter.…”

Current-voltage characteristic and sheet resistances after annealing of femtosecond laser processed sulfur emitters for silicon solar cells

“…On the other hand, annealing processes are investigated in correlation with structural changes in the silicon lattice. 12,13 It is found that annealing at T ¼ 800 C improves the crystal quality. 12,13 However, it remains still unclear if the impact of annealing influences the pn-junction.…”

“…3,10 The chalcogens are impurities incorporated far above the solubility limit. 11,12 The required incorporation techniques diminish the silicon crystal quality, 11,13 leading to intrinsic defects in the silicon lattice. Subsequent thermal processes enhance among others the performance of a pn-junction with such a sulfur emitter.…”