Refractive index, free carrier concentration, and mobility depth profiles of ion implanted Si: optical investigation using FTIR spectroscopy (original) (raw)
Related papers
Defect evolution in ion implanted crystalline Si probed by in situ conductivity measurements
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1995
We have used in situ conductivity measurements to investigate the defect evolution and accumulation in ion implanted crystalline Si. Upon irradiation at room temperature with 400 keV Si ions the initial conductivity (4X10w2 an-l cm-') decreases by about 4 orders of magnitude to a value of 2X 10m6 fi2-l cm-l, characteristic of intrinsic silicon, at a fluence of 1X 1013/cm2 and then slowly increases at higher fluences. Deep level transient spectroscopy measurements, transmission electron microscopy analyses, and thermal annealings were performed on samples irradiated at various fluences. The data demonstrate that the strong conductivity decrease at low fluences is the result of a dopant compensation produced by deep levels introduced by divacancies and complex defects in the band gap. At higher iiuences the conduction is dominated by electron hopping in a buried continuous amorphous layer produced by irradiation. These results are reported and discussed.
Journal of The Electrochemical Society, 2001
Fourier transform infrared ͑FTIR͒ spectroscopy was employed to characterize the formation process of conducting and/or insulating layers in silicon by arsenic or oxygen ion implantation, respectively. Two methods of buried insulating layer formation were studied. The first involved implantation of 200 keV oxygen ions at a dose of 1.8 ϫ 10 18 cm Ϫ2 at implantation temperature in the range 500-550°C followed by annealing at 1300°C for 5 h. The second involved 190 keV oxygen implantation in three cycles, each cycle followed by annealing at 1315°C for 2 h. The Si overlayer of these substrates as well as bulk Si wafers were then implanted with 70 keV As ϩ ions at a nominal dose of 5 ϫ 10 15 cm Ϫ2 . Annealing at 950 or 1150°C led to dopant activation and the formation of conducting layers. The optical multilayer modeling of such inhomogeneous structures is given in detail. Depth profiles of oxygen atomic concentration or free carrier concentration as well as the corresponding refractive index depth profiles are quantified in a fast, cheap, accurate, and contactless way using FTIR spectroscopy. Furthermore, layer thickness, chemical composition, crystallinity, interface quality, and the electrical and transport properties are also evaluated. The results are in good agreement with ion beam analysis and electrical measurements and it is demonstrated that FTIR spectroscopy can act as a complementary technique to ion beam analysis techniques, taking over the role of the electrical methods ͑which are destructive͒ and giving much more information.
Optical absorption in ion implanted Si films
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1995
We present a study of the effect of ion implantation induced damage on the optical absorption spectra of Si fiims, extending from energies above the band gap down to energies far mto the srbgap region of Si. The changes induced in the optical band gap, band edge slopes and in the subgap features of the spectra are described. The various stages of formation and quenching of divacancies were monitored as a function of implantation conditions and annealing cycles through their L-8 pm absorption band. The study of the structural relaxation process in implanted and sputtered a-% gave indications that the process is associated with annihilation of defects as well as average strain reduction in the material, in agreement with earlier indications.
Journal of Applied Physics, 2014
A depth profiling technique using photocarrier radiometry (PCR) is demonstrated and used for the reconstruction of continuously varying electronic transport properties (carrier lifetime and electronic diffusivity) in the interim region between the ion residence layer and the bulk crystalline layer in H þ implanted semiconductor wafers with high implantation energies ($MeV). This defect-rich region, which is normally assumed to be part of the homogeneous "substrate" in all existing two-and three-layer models, was sliced into many virtual thin layers along the depth direction so that the continuously and monotonically variable electronic properties across its thickness can be considered uniform within each virtual layer. The depth profile reconstruction of both carrier life time and diffusivity in H þ implanted wafers with several implantation doses (3 Â 10 14 , 3 Â 10 15 , and 3 Â 10 16 cm À2) and different implantation energies (from 0.75 to 2.0 MeV) is presented. This all-optical PCR method provides a fast non-destructive way of characterizing sub-surface process-induced electronic defect profiles in devices under fabrication at any intermediate stage before final metallization and possibly lead to process correction and optimization well before electrical testing and defect diagnosis becomes possible.
Investigation of inhomogeneous structures of near-surface-layers in ion-implanted silicon
The ion implantation as a subject of investigations attracts increasing interest because of its technological applications. For example, the ion implantation and the adequate thermal treatment are the basic processes for fabrication of a new so-called delta-BSF solar cell. In this silicon solar cell, the continuous sub-structure of modified material _planar amorphous-like layer of nanometric thickness with very thin transition zones. is inserted into the single-crystal emitter. From earlier high resolution electron microscopy studies, it is evident that these two Si phases coexist in the form of well-defined layers separated by sharp heterointerfaces wZ.T. Kuznicki, J. Thibault, F. Chautain-Mathys, S. De Unamuno, Towards ion beam processed single-crystal Si solar cells with a very high efficiency, E-MRS Spring Meeting, Strasbourg, France, First Polish–Ukrainian Symposium, New Photovoltaic Materials for Solar Cells, October 21–22, Krakow, Poland, 1996.x. The aim of this paper is the further structural characterisation of silicon single crystal with buried ‘amorphous’ layer. The non-destructive X-ray diffraction methods as well as the transmission electron microscopy were used to investigate the quality of the a-Sirc-Si heterointerfaces, structural homogeneity of the layers and distribution of the stress field. The measurements were carried out on an initial, as-implanted and annealed material. The _100:-oriented Si single crystals were implanted with 180 keV energy P ions at room temperature.
Characterisation of ultra-shallow disorder profiles and dielectric functions in ion implanted Si
Thin Solid Films, 2011
Ultra-shallow (below 20 nm) disorder profiles have been characterized by spectroscopic ellipsometry (SE). The implanted depth region has been divided into sublayers with dielectric functions calculated by the effective medium approximation using single-crystalline and disordered components. The damage depth profile has been parameterized using a box model, an independent multilayer model, a graded multilayer model, an error function, and Gaussian profiles. Literature values and Tauc-Lorentz (TL) parametrization as well as multi-sample and single-sample approaches have been compared to describe the dielectric function of the disordered component. The distribution of the implanted ions and/or damage have been cross-checked using medium energy ion scattering (MEIS), transmission electron microscopy and Monte Carlo simulations. We found a good agreement in the damage profiles obtained by the different methods. There is an offset between the SE and MEIS damage profiles due to the fact that SE is very sensitive to the surface roughness, in contrast to MEIS. The correlation between this offset and the surface roughness has been investigated using atomic force microscopy.
Depth Profiling of Electronic Transport Properties in \mathrm{H}^{+}$$ H + -Implanted n-Type Silicon
International Journal of Thermophysics, 2014
A depth profiling theory for electronic transport properties (carrier diffusivity and lifetime) in ion-implanted semiconductor wafers using infrared photocarrier radiometry (PCR) is proposed. The ion-implanted inhomogeneous sample was sliced into many virtual sub-layers along the depth direction so that the continuously variable electronic properties across the whole thickness can be considered as uniform in each incremental slice. A recursion relationship among the slices was obtained, and the overall PCR signal was built based on contributions from each slice. Experimental lifetime and electronic diffusivity reconstructions of depth profiles at two ion doses (3×10 14 cm −2 and 3×10 15 cm −2) and several implantation energies (from 0.75 MeV to 2.0 MeV) have been demonstrated.
Journal of Applied Physics, 2007
Industrial n-type Si wafers ͑resistivity of 5 -10 ⍀ cm͒ were H + ion implanted with energies between 0.75 and 2.00 MeV, and the electronic transport properties of the implanted layer ͑recombination lifetime, carrier diffusion coefficient, and front-surface and implanted-interface recombination velocities s 1 and s 2 ͒ were studied using photocarrier radiometry ͑PCR͒. A quantitative fitting procedure to the diffusing photoexcited free-carrier density wave was introduced using a relatively simple two-layer PCR model in lieu of the more realistic but substantially more complicated three-layer model. The experimental trends in the transport properties of H + -implanted Si layers extracted from the PCR amplitude and phase data as functions of implantation energy corroborate a physical model of the implanted layer in which ͑a͒ overlayer damage due to the light H + ions decreases with increased depth of implantation at higher energies, ͑b͒ the implanted region damage close to the interface is largely decoupled from the overlayer crystallinity, and ͑c͒ the concentration of implanted H + ions decreases at higher implantation energies at the interface, thus decreasing the degree of implantation damage at the interface proper.
2007
Industrial n-type Si wafers ͑resistivity of 5-10 ⍀ cm͒ were H + ion implanted with energies between 0.75 and 2.00 MeV, and the electronic transport properties of the implanted layer ͑recombination lifetime, carrier diffusion coefficient, and front-surface and implanted-interface recombination velocities s 1 and s 2 ͒ were studied using photocarrier radiometry ͑PCR͒. A quantitative fitting procedure to the diffusing photoexcited free-carrier density wave was introduced using a relatively simple two-layer PCR model in lieu of the more realistic but substantially more complicated three-layer model. The experimental trends in the transport properties of H +-implanted Si layers extracted from the PCR amplitude and phase data as functions of implantation energy corroborate a physical model of the implanted layer in which ͑a͒ overlayer damage due to the light H + ions decreases with increased depth of implantation at higher energies, ͑b͒ the implanted region damage close to the interface is largely decoupled from the overlayer crystallinity, and ͑c͒ the concentration of implanted H + ions decreases at higher implantation energies at the interface, thus decreasing the degree of implantation damage at the interface proper.
Thin Solid Films, 2009
The optical properties of ion implanted silicon and silicon-on-insulator substrates have been studied by Fourier transform infrared spectroscopy. The influence of the implanted-ion mass in changing the refractive index of a silicon target has been examined by implanting 80 keV 11 B + and 62 P 2 + ions respectively. A refractive index rise not exceeding 2% and total amorphization were observed respectively in the vicinity of the Si surface after boron and phosphorous implantations. Free carrier profiles generated after thermal annealing at 950°C/30 min and 1150°C/120 min were modeled by Pearson and half-Gaussian distributions respectively. The phosphorous implantation was also performed in silicon-on-insulator substrates, yielding after annealing nearly homogeneous free-carrier profiles in the top-Si layer and optical mobility values comparable to those of bulk-Si.