Role of C in the formation and kinetics of nanovoids induced by He+ implantation in Si

Abstract

The formation and growth of nanovoids in a C-doped Si layer after He+ implantation and thermal annealing are reported. A structure consisting of 240 nm of Si, 20 nm of Si doped with C at 0.8 at. %, and 240 nm of Si cap was realized by molecular beam epitaxy onto a 100 Si Czochralsky substrate. Three sets of samples were implanted with He+ at 30 keV and different doses of 81015, 31016, and 51016 cm−2 and subsequently annealed at 800 °C in N2 atmosphere. Cross-section transmission electron microscopy was used to determine the void size and location. The tensile strain of the C-doped layer was measured by high-resolution x-ray diffraction. Our studies report the double role of C in the formation and evolution of nanovoids. After the low dose implantation, the C-doped layer still shows tensile strain due to substitutional C, and voids are localized only within this layer. At higher implantation doses, all the C atoms have been displaced from substitutional sites. No more strain is present in the C-doped layer and the presence of large cavities in its neighborhood is strongly inhibited. This work shows how localized strain in epitaxial films can be effectively used to drive nanovoid formation and evolution

Irradiation-induced nano-voids in strained tin precipitates in silicon

“…8-15. In those studies, the epitaxial SiGe layer of under-critical thickness was first grown in a compressively strained state. Ion implantation of heavy (Ge, As, or Sn) [8][9][10][11] or light (He, H) [12][13][14][15] ions was used for the generation of point defects. It was demonstrated that the strained SiGe layers accumulate the implantation-induced vacancies followed by their thermally assisted evolution into voids.…”

“…It was demonstrated that the strained SiGe layers accumulate the implantation-induced vacancies followed by their thermally assisted evolution into voids. [8][9][10][11][12][13][14][15] The voids were of nanometer size and strictly assembled within the strained SiGe layers buried in the Si matrix. [8][9][10][11] More recently, the ability to collect vacancies and low-size gas atoms in compressively strained SiGe layers was used for the enhancement of exfoliation in advanced Smart-Cut technology by using either hydrogen ion implantation 14 or plasma treatment.…”

Electrode kinetics of Cu–SiO2-based resistive switching cells: Overcoming the voltage-time dilemma of electrochemical metallization memories

“…The authors interpret the enhancement of cavity nucleation in relatively thick layers ͑20 nm͒ as a consequence of the strain induced by the C incorporation in the Si lattice. 12 However, applications require a detailed experimental and theoretical analysis of the effect of enhanced cavity nucleation along embedded SiGe ͑Ge͒ or Si:C layers on the relaxation process of SiGe layers, not available up to date. Here, we report on the use of a buried ultrathin Si:C layer ͑␦-Si: C͒ on the Si͑100͒ substrate to improve the relaxation of epitaxial strained Si x Ge 1−x structures.…”

Anisotropy of strain relaxation in (100) and (110) Si/SiGe heterostructures

“…The preferential nucleation of He platelets in the Si substrate can be realized by the introduction (epitaxial growth) of an "impurity" layer which either reduces the energy associated with cavity formation, e.g., a SiGe layer 24,25 or by creating additional volume for He accumulation through introduction of smaller substitutional atoms, e.g., Si:C layer. 26,27 Such structures localize and homogenize the planar distribution of the dislocation loop sources (platelets) sensibly increasing the SiGe degree of relaxation. 27 …”