Stress evolution in Si during low-energy ion bombardment

Abstract

Measurements of stress evolution during low energy argon ion bombardment of Si have been made using a real-time wafer curvature technique. During irradiation, the stress reaches a steady state compressive value that depends on the flux and energy. Once irradiation is terminated, the measured stress relaxes slightly in a short period of time to a final value. To understand the ion-induced stress evolution and relaxation mechanisms, we account for the measured behavior with a model for viscous relaxation that includes the ion-induced generation and annihilation of flow defects in an amorphous Si surface layer. The analysis indicates that bimolecular annihilation (i.e., defect recombination) is the dominant mechanism controlling the defect concentration both during irradiation and after the cessation of irradiation. From the analysis we determine a value for the fluidity per flow defect.

Nonuniversality due to inhomogeneous stress in semiconductor surface nanopatterning by low-energy ion-beam irradiation

“…Our MD results imply that the interplay between ion-induced stress, viscous flow dynamics, and sputtering leads to partial defect relaxation, which is the basic idea of Davis' model for stress evolution in irradiated materials. We note that very recent measurements [42] of stress evolution during low-energy argon ion bombardment of Si seem to favor specifically a bimolecular recombination mechanism for individual flow defects [50].…”

“…In the process of improving upon our current approximations, it would be interesting to make contact with kinetic descriptions like rate equations for flow defect dynamics [50], which have been recently validated against stress measurements on Si [42]. Still, we believe that our general approach and conclusions can apply to a wide range of systems and experimental conditions.…”

“…Sustained irradiation creates a well-defined amorphous layer on top of a crystalline bulk [11,[38][39][40]. The residual stress thus built up throughout the layer is partially relaxed by defect motion and sputtering [41,42], and is described by a stress tensor τ . Thus microscopic defect creation produces macroscopic stress.…”

Ion induced controlled modifications in structural and optical properties of indium oxide thin films – studies with 25‐keV Co− and N+ beam implantations

“…As energy deposited by electronic energy loss is sufficient enough to activate interstitials to be positioned at lattice sites, the material performance is determined by the dynamic response to the defect production and their annihilation by possible synergistic or competitive processes . Further, the ion induced stress evolution and its relaxation significantly change the production and annihilation mechanism of defects and hence the dynamic response of the material . The ionic radii of In +3 is quite comparable to that of Co +2 , and the possible substitution of Co to In sites may give rise to different nucleation conditions in Co − implanted indium oxide thin films promoting the grain growth (as demonstrated in SEM images) and subsequent improvement in the crystallinity (as seen in the XRD patterns) with increasing the ion fluence.…”

Atomistic simulations of focused ion beam machining of strained silicon

“…The (0 0 1) surface is hence irradiated under normal incidence with θ [001] = 1 • , whereas the (1 0 0) surface is irradiated under an extreme grazing incidence with θ [100] = 89 • . Note that the {0 0 1} family of surfaces chosen in this study is typical for experiments on silicon wafers [10,28,29,30]. The sample dimensions are chosen to have a balance between the large volume required for correct stress-strain relaxation and reasonable computational times: 60×20×74 a 0 (33×11×43 nm 3 ) in the x, y and z directions, respectively, with a 0 = 0.5431 nm being the lattice parameter at 0 K of the chosen Si potential [31].…”