Electrical studies on H-implanted silicon

Abstract

Electrical properties of high-dose (1.6X 10' at./cm') H+-implanted B-doped silicon have been investigated using transient capacitance spectroscopy, capacitance-voltage, and spreading resistance profiling.The role of hydrogen is twofold: to interact with the defects created by ion implantation, modifying their electrical properties, and to neutralize the shallow-acceptor dopants. The evolution of the defects responsible for the deep levels and the depth of the neutralized region have been investigated after isochronal annealing at various temperatures up to 800'C. Deep-level transient spectroscopy spectra show three hole traps; two of them, H(0.67), H(0.33), have been tentatively identified as vacancy-hydrogen complexes (VH2, VH3) while the attribution of the third, H(0.23), detected in the samples annealed at 400-450'C, is uncertain. As a function of the heat treatment, the total number of defects is strongly reduced at 300'C, it increases for T )300 'C and at the highest temperatures, namely 800'C, the defects disappear. The first decrease is attributed to the formation of neutral VH4 complexes and the disappearance to complete decoration of point defects or their agglomeration. The thickness of the passivated region has a minimum at 300'C, which corresponds to the formation of the stable VH4. At lower temperatures, the hydrogen necessary for the passivation is the unbonded one and presumably comes from the implantation process itself. At higher temperature, H comes from the breaking of the VH4 or H"complexes. These results are in good agreement with our previous studies concerning the role played by hydrogen in affecting the crystal properties of silicon.

Hydrogen precipitation in highly oversaturated single-crystalline silicon

“…We have gained direct knowledge of the behaviour of hydrogen in ion-implanted crystalline silicon from a long series of studies started in 1989 and carried out by employing experimental techniques like secondary ion mass spectrometry (SIMS) [13 to 151, multiplecrystal X-ray diffraction (XRD) [ 131, channeling Rutherford back-scattering spectrometry (RBS) [13 to 191, elastic recoil detection analysis (ERDA) [15,191, transmission electron microscopy (TEM) [13 to 15, 17 to 191, spectroscopic ellipsometry [20], spreading resistance (SR) [21], deep level transient spectroscopy (DLTS) [21], positron annihilation technique (PAT) [22], and photoluminescence (PL) [23]; by simulating the imparted damage by means of MARLOWE and TRIM (transport of ion in matters) codes ([18] and [19], respectively); and by developing new methods for the analysis of channeling RBS spectra [18, 241. With these techniques we have studied the effects of the implanation energy E , fluence @, and temperature Tmp,, and of the subsequent annealing process (temperature T,,, and duration t,,,) on the physico-chemical properties of the hydrogen-implanted Si : H layer; the attention was mainly concentrated on lightly doped silicon implanted at low energy (15.5 keV) and high fluence (1.6 x 1OI6 cm-').…”

Visible photoluminescence from He-implanted silicon

“…12 For higher temperatures the carriers quantum confinement is probably eliminated by nanoblisters coarsening ͑giving detectable bubbles͒ and the passivation of nonradiative recombination centers decreases, due to the H loss. Nanoblisters cannot be resolved by TEM and their existence can only be detected through the measurement of the displacement field they cause within the Si lattice.…”

Evolution of implantation induced damage under further ion irradiation: Influence of damage type

“…Furthermore, chemically active implanted species such as H can neutralize dopants, thereby causing strong changes in the electrical property of crystalline silicon. 25 The low mobility of carriers in the implanted region effectively limits diffusion of excited electrons away from the vicinity of the ion track. Most of the electronic energy lost by the incident ions is stored locally as potential energy in trapped excitons ͑localized electron-hole pairs͒.…”