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The study of the solid-phase epitaxial growth ͑SPEG͒ process of Si ͑variously referred to as solid-phase epitaxy, solid-phase epitaxial regrowth, solid-phase epitaxial crystallization, and solid-phase epitaxial recrystallization͒ amorphized via ion implantation has been a topic of fundamental and technological importance for several decades. Overwhelmingly, SPEG has been studied ͑and viewed͒ as a single-directional process where an advancing growth front between amorphous and crystalline Si phases only has one specific crystallographic orientation. However, as it pertains to device processing, SPEG must actually be considered as multidirectional ͑or patterned͒ rather than bulk in nature with the evolving growth interface having multiple crystallographic orientations. Moreover, due to the increasingly ubiquitous nature of stresses presented during typical Si-based device fabrication, there is great interest in specifically studying the stressed-SPEG process. This work reviews the progress made in understanding the multidirectional SPEG and, more importantly, stressed multidirectional SPEG process. For the work reviewed herein, ͑001͒ Si wafers with ͗110͘-aligned, intrinsically stressed Si 3 N 4 / SiO 2 patterning consisting of square and line structures were used with unmasked regions of the Si substrate amorphized via ion implantation. It is revealed that the stresses generated in the Si substrate from the patterning, both in line and square structures, alter the kinetics and geometry of the multidirectional SPEG process and can influence the formation of mask-edge defects which form during growth to different degrees as per differences in the substrate stresses generated by each type of patterning. Likewise, it is shown that application of external stress from wafer bending during SPEG in specimens with and without patterning can also influence the geometry of the evolving growth interface. Finally, the effect of the addition of SPEG-enhancing impurities during multidirectional stressed growth is observed to alter the evolution of the growth interface, thus suggesting that stress influences on growth are much less than those from dopants. Within the context of prior work, attempts are made to correlate the prior observations in single-directional stressed SPEG with the observations from patterned stressed SPEG reviewed herein. However, as is argued in this review, it ultimately appears that much of the research performed on understanding the single-directional stressed-SPEG process cannot be reasonably extended to the multidirectional stressed-SPEG process.

Modeling the two-dimensional ͑2D͒ solid-phase epitaxial regrowth ͑SPER͒ of amorphized Si ͑variously referred to as solid-phase epitaxial growth, solid-phase epitaxy, solid-phase epitaxial crystallization, and solid-phase epitaxial recrystallization͒ has become important in light of recent studies which have indicated that relative differences in the velocities of regrowth fronts with different crystallographic orientations can lead to the formation of device degrading mask edge defects. Here, a 2D SPER model that uses level set techniques as implemented in the Florida object oriented process simulator to propagate regrowth fronts with variable crystallographic orientation ͑patterned material͒ is presented. Apart from the inherent orientation dependence of the SPER velocity, it is established that regrowth interface curvature significantly affects the regrowth velocity. Specifically, by modeling the local SPER velocity as being linearly dependent on the local regrowth interface curvature, data acquired from transmission electron microscopy experiments matches reasonably well with simulations, thus providing a stable model for simulating 2D regrowth and mask edge defect formation in Si.

Articles you may be interested inModeling two-dimensional solid-phase epitaxial regrowth using level set methods Level set methods have previously been successfully implemented in interface propagation for etching and deposition processes. In this article, the authors show that level set methods can be used to model solid phase epitaxial regrowth. The model incorporates orientation dependence of regrowth as found by Csepregi et al. ͓J. Appl. Phys. 49, 3906 ͑1978͔͒. The orientation dependent velocity data are taken from Csepregi's paper and fitted to a polynomial function to give the growth velocity for level set methods. Simulations show the capability of our model in predicting the pinching of the corners in ͗111͘ direction and humplike shape in ͗100͘ direction. This is confirmed by the transmission electron microscope pictures from recent papers. This modeling holds special interest because of the different diffusivities of boron in amorphous and crystalline silicon ͑approximately five orders of magnitude difference͒ and because of the various defects forming at the pinching corners which could lead to higher leakage current in scaled devices. The level set model is implemented in FLOOPS.

The role of applied stress on interface stability during Si solid-phase epitaxial growth was investigated. Transmission electron microscopy observations of growth interface evolution revealed in-plane uniaxial compression ͑tension͒ led to interface instability ͑stability͒. Additionally, level set simulations revealed that the stress-influenced interface instability was accurately modeled by adjusting the strength of the linear dependence of local interface velocity ͑rate of change of interface position with respect to time͒ on local interface curvature proposed in previous work. This behavior is explained in terms of tension in the growth interface controlling interface stability during growth; it is argued that compressive ͑tensile͒ stress tends to reduce ͑enhance͒ interfacial tension and results in interfacial instability ͑stability͒ during growth.