In Situ Studies of the Interaction of Dislocations with Point Defects during Annealing of Ion Implanted Si/SiGe/Si (001) Heterostructures

Abstract

Strained layer heterostructures provide ideal systems with which to study the dynamics of dislocation motion via in situ transmission electron microscopy, as the geometry, strain state, and kinetics can be characterized and directly controlled. We discuss how these structures are used to study dislocation-point defect interactions, emphasizing the experimental requirements necessary for quantification of dislocation motion. Following ion implantation, different concentrations and types of point defects are introduced within the SiGe epilayer depending on the implantation species, energy, and current density. By annealing samples in situ in the transmission electron microscope (TEM) following implantation, we can directly observe dislocation motion and quantify the effect of dislocation-point defect interactions on dislocation velocities. We find that dislocation motion is impeded if the implantation dose peak lies within the epilayer, as dislocations pin at point defect atmospheres. Shallow BF2 implantation into the sample capping layer results in more complicated behavior. For low current density implants, dislocation velocities may be dramatically increased; at higher current densities the magnitude of this increase is significantly smaller. Implantation of different ions separately implicates fluorine as the species responsible for the observed increases in dislocation velocities, presumably due to an electrical effect on the rate of dislocation kink nucleation.

Interactions of Moving Dislocations in Semiconductors with Point, Line and Planar Defects

“…A complete description is given by Stach et al [33]. For example, we observe that these dislocation velocity enhancement effects are a sensitive function of the implant ion current density, with substantially greater enhancements observed under otherwise identical conditions for implant fluxes of 0.5 mA/cm 2 than for 5.0 mA/cm 2 .…”

Temperature Calibration of a Specimen-heating Holder for Transmission Electron Microscopy

“…The effects of dopants and ion irradiation on the growth process in Si have also been extensively studied (Olson & Roth, 1988). Stach et al (1998) investigated the temperature calibration of the TEM heating holder using a combination of solidphase epitaxial regrowth and the focused ion beam sample preparation technique. They carefully examined the regrowth region from a sample annealed for 30 min at a thermocouple reading of 575 o C. The measured regrowth velocity for this sample was 4.4 nm/sec, which indicates that the thermocouple reading was highly accurate in this case.…”

Strain relaxation of GeSi/Si(001) heterostructures grown by low-temperature molecular-beam epitaxy

“…44,45 The threading dislocation velocity increased by factors of 5-8 if the damage peak due to radiation was located only in the upper part of the Si layer which covered the GeSi layer. As was noted in Ref.…”