Jerias Batista

Temperature dependence of carrier mobility in Si wafers measured by infrared photocarrier radiometry

A recently introduced infrared photocarrier radiometry technique has been used to determine the temperature dependence of carrier mobility in Si wafers. In addition, its potential to determine simultaneously the carrier lifetime, diffusion coefficient, and surface recombination velocity is reported. This noncontact, nonintrusive, and all-optical technique relies on the detection of infrared radiation from harmonically excited free carriers (pure electronic diffusion-wave detection). Using a multiparameter fitting to a complete theory, the results showed that the lifetime increases with temperature, the diffusion coefficient decreases [D(T)∼T−1.5], and the temperature dependence of carrier mobility is μ(T)=(1.06±0.07)×109×T−2.49±0.01 cm2/V s.

Accuracy of photocarrier radiometric measurement of electronic transport properties of ion-implanted silicon wafers

The determination of the electronic transport properties of ion-implanted silicon wafers with the photocarrier radiometry (PCR) technique by fitting frequency scan data to a single layer model via a multiparameter fitting procedure is presented. A three-layer model is used to simulate the inhomogeneous structure of the ion-implanted wafers. The effects of the structural, electronic, and optical properties of the implanted layer, which are affected significantly by ion implantation, on the frequency behavior of the PCR signal of implanted wafers are discussed. Data simulated with the three-layer model are fitted to a single-layer model to extract the electronic transport properties of implanted wafers. The fitted carrier lifetime and diffusion coefficient are found to be close to that of the substrate layer which is assumed to remain intact after the ion implantation process. When self-normalized relative amplitude is used in the multiparameter fitting, the fitted surface recombination velocity is determin...

Three-layer photocarrier radiometry model of ion-implanted silicon wafers

A three-dimensional three-layer model is presented for the quantitative understanding of the infrared photocarrier radiometry (PCR) response of ion-implanted semiconductors, specifically Si. In addition to the implanted layer and intact substrate normally assumed in all existing two-layer theoretical models to describe the photothermal response of ion-implanted semiconductors, a surface layer is considered in this three-layer model to represent a thin, less severally damaged region close to the surface. The effects on the PCR signal of several structural, transport, and optical properties of ion-implanted silicon wafers affected significantly by the ion implantation process (minority carrier lifetime, diffusion coefficient, optical absorption coefficient, thickness of the implanted layer, and front surface recombination velocity) are discussed. The dependence of the PCR signal on the ion implantation dose is theoretically calculated and compared to experimental results. Good agreement between experimental...

Ion implant dose dependence of photocarrier radiometry at multiple excitation wavelengths

The dependence of the photocarrier radiometric (PCR) signal on ion implant dose in Si is reported. The results show almost entirely monotonic behavior over a large range of industrially relevant fluences (1×1010–1×1016cm−2) for B+11, As+75, P+31, and BF2+ implanted in Si wafers at various energies. In addition, the use of excitation sources with a range of absorption coefficients is shown to be very useful in improving the sensitivity of the PCR amplitude to implant dose.

Deep subsurface electronic defect image contrast and resolution amplification in Si wafers using infrared photocarrier radiometry

A photocarrier radiometry technique using a secondary subband-gap dc light source is introduced, along with the applications to deep subsurface electronic defect analysis in Si wafers. It is shown that the use of a dc light source, in addition to the modulated laser beam, drastically enhances the potential of the technique in resolving low-level damage otherwise virtually indistinguishable by conventional photothermal techniques. Using this methodology, the overall contrast enhancement was about 386% for amplitude and 5586% in phase over conventional photocarrier radiometry.

Two-beam cross-modulation photocarrier radiometry: principles and contrast amplification in semiconductor subsurface imaging

A two-beam photo-carrier radiometry (PCR) technique of semiconductors has been developed. The technique operates on the superposition of superband-gap and subband-gap laser beams which results in the cross-modulation of the backscattered subband-gap laser intensity by the harmonically varying free-carrier-wave density-dependent infrared absorption coefficient. A theory of this two-beam cross-modulation approach and various experimental configurations applied to the imaging of electronic contamination and defects in silicon wafers are presented. Owing to the nonlinear interaction of the two beams, the configuration revealed a new optoelectronic effect, the decrease of the residual subband-gap absorption coefficient due to the decreased carrier capture cross-section brought about by the depletion of occupied band-gap states in the presence of photons produced by radiative recombination. Quantitative values of the optoelectronic constant B associated with the rate of depletion of free-carrier capture cross-section with superband-gap intensity, as well as of IeR, the intensity of radiative recombination emissions, were obtained. These values cannot be measured by conventional PCR or other single-ended optoelectronic techniques. The theory explains the experimental dependence of electronic transport properties on the intensity of the subband-gap beam and accounts for optoelectronic imaging contrast amplification in contaminated or defect semiconductors. The two-beam cross-modulation PCR was further shown to enhance the imaging contrast of a certain electronic contamination type (Fe in p-Si). A dramatic phase contrast enhancement of subsurface defects made by low-dose proton implantation was demonstrated at superband-gap laser intensity levels one order of magnitude lower than possible with single-ended optoelectronic imaging methodologies. This is tentatively attributed to relatively low-injection trap-filling well below optoelectronic trap saturation.

Noncontacting laser photocarrier radiometric depth profilometry of harmonically modulated band bending in the space-charge layer at doped SiO2‐Si interfaces

Laser infrared photocarrier radiometry (PCR) was used with a harmonically modulated low-power laser pump and a superposed dc superband-gap optical bias (a secondary laser beam) to control and monitor the space-charge-layer (SCL) width in oxidized p‐Si–SiO2 and n‐Si–SiO2 interfaces (wafers) exhibiting charged interface-state related band bending. Applying the theory of PCR-SCL dynamics [A. Mandelis, J. Appl. Phys. 97, 083508 (2005)] to the experiments yielded various transport parameters of the samples as well as depth profiles of the SCL exhibiting complete ( p-type Si) or partial (n-type Si) band flattening, to a degree controlled by widely different minority-carrier capture cross section at each interface. The uncompensated charge density at the interface was also calculated from the theory.

Thermoreflectance microscopy applied to the study of electrostatic discharge degradation in metal-oxide-semiconductor field-effect transistors

We investigated the effect of electrostatic discharge on n-channel metal-oxide-semiconductor field-effect transistors using the thermoreflectance microscopy. The gate terminals of the transistors were submitted to electrostatic pulses on a zap system that respects the human body model. The pulse intensity varied from 40to140V in a cumulative sequence. Electrical characterization showed that the transistor threshold voltage was no longer positive for pulses of 110V and higher. No significant changes in the thermoreflectance maps were observed in these cases. For pulses of 140V a large leakage current appeared, and the thermoreflectance maps revealed strong peaks (localized spot) associated with the induced damage.