Interface stability in stressed solid-phase epitaxial growth

The role of applied stress on interface stability during Si solid-phaseepitaxialgrowth was investigated. Transmission electron microscopy observations of growthinterface evolution revealed in-plane uniaxial compression (tension) led to interface instability (stability). 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 time) on local interface curvature proposed in previous work. This behavior is explained in terms of tension in the growthinterface controlling interface stability during growth; it is argued that compressive (tensile) stress tends to reduce (enhance) interfacial tension and results in interfacial instability (stability) during growth.The authors acknowledge the Semiconductor Research Corporation for funding this work

Stressed multidirectional solid-phase epitaxial growth of Si

The study of the solid-phase epitaxial growth (SPEG) process of Si (variously referred to as solid-phase epitaxy, solid-phase epitaxial regrowth, solid-phase epitaxial crystallization, and solid-phase epitaxial recrystallization) amorphized via ion implantation has been a topic of fundamental and technological importance for several decades. Overwhelmingly, SPEG has been studied (and viewed) 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 patterned) 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, (001) Si wafers with 〈 110 〉 -aligned, intrinsically stressed Si3N4/SiO2 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

Effect of n- and p-type dopants on patterned amorphous regrowth

Solid-phase epitaxial regrowth for patterned amorphous regions has been known to form device degrading mask-edge defects. Prior studies have shown that orientation dependence of regrowth leads to pinching of the slow regrowing corners (111 fronts) that create these defects [K. L. Saenger, J. Appl. Phys. 101, 104908 (2007)]. Also, the effect of n -type and p -type dopants on regrowth is known only for 001 bulk [B. C. Johnson and J. C. McCallum, Phys. Res. B 76, 045216 (2007); J. S. Williams and R. G. Elliman, Phys. Rev. Lett. 51, 1069 (1983)]. This article studies the effect of these dopants (boron and arsenic) on the patterned amorphous regrowth to see if there is any change in the corner regrowth. The experiment was done on very low resistivity wafers (∼0.003 ω cm) so that the doping concentration was constant in the whole amorphous region and the doping was high enough to have a significant effect on the regrowth. Recent studies have also shown that local α-c interface curvature is an important factor in modeling patterned amorphous regrowth for intrinsic Si [S. Morarka, J. Appl. Phys. 105, 053701 (2009)]. This experiment shows the dopant-curvature relationship that is important from modeling perspective

Modeling two-dimensional solid-phase epitaxial regrowth using level set methods

Modeling the two-dimensional (2D) solid-phase epitaxial regrowth (SPER) of amorphized Si (variously referred to as solid-phase epitaxial growth, solid-phase epitaxy, solid-phase epitaxial crystallization, and solid-phase epitaxial recrystallization) 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 material) 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

Front-end process modeling in silicon

Front-end processing mostly deals with technologies associated to junction formation in semiconductor devices. Ion implantation and thermal anneal models are key to predict active dopant placement and activation. We review the main models involved in process simulation, including ion implantation, evolution of point and extended defects, amorphization and regrowth mechanisms, and dopant-defect interactions. Hierarchical simulation schemes, going from fundamental calculations to simplified models, are emphasized in this Colloquium. Although continuum modeling is the mainstream in the semiconductor industry, atomistic techniques are starting to play an important role in process simulation for devices with nanometer size features. We illustrate in some examples the use of atomistic modeling techniques to gain insight and provide clues for process optimization