Peter Pichler

A physically based model for the spatial and temporal evolution of self-interstitial agglomerates in ion-implanted silicon

A physically motivated model that accounts for the spatial and temporal evolution of self-interstitial agglomerates in ion-implanted Si is presented. For the calibration of the model, a genetic algorithm is used to find the optimum set of physical parameters from experimental data. Mean-size evolution of {113} defects obtained by transmission electron microscopy and self-interstitial oversaturation results measured in the vicinity of extended defects are combined in the same fitting procedure. The calibration of parameters shows that binding energies of small self-interstitial clusters exhibit strong maxima, as reported in other investigations. Results of the calibrated model are compared to experimental data obtained in complementary investigations. It is demonstrated that the model is able to predict a wide variety of physical phenomena, from the oversaturation of self-interstitials via the mean-size evolution of {113} defects to the depth distribution of the density of the latter.

Determination of aluminum diffusion parameters in silicon

Aluminum as the fastest diffusing acceptor dopant in silicon is commonly used for the fabrication of power semiconductors with p–n junction depths ranging from some microns to more than a hundred microns. Although long used, its diffusion behavior was not sufficiently characterized to support computer–aided design of devices. In this work, the intrinsic diffusion of aluminum was investigated in the temperature range from 850 to 1290 °C. Combining nitridation and oxidation experiments, the fractional diffusivity via self-interstitials was determined. By diffusion in high-concentration boron- and phosphorus-doped silicon the behavior of aluminum under extrinsic conditions was investigated.

Current Understanding and Modeling of Boron-Interstitial Clusters

Scaling of devices requires not only shallow junctions but also high levels of dopant activation. For boron as the main p-type dopant, the latter requirement is especially problematic since small clusters of boron atoms and self-interstitials, known also as boron-interstitial clusters (BICs), were found to deactivate and immobilize large fractions of the implanted atoms during post-implantation annealing. In this article, the properties of BICs are reviewed and their influence on semiconductor processes are highlighted.

Distribution and segregation of arsenic at the SiO2/Si interface

The segregation and pile-up of arsenic atoms at the Si/SiO2 interface in steady state was investigated in detail by a combination of gracing incidence x-ray fluorescence spectroscopy (GI-XRF) measurements, electrical measurements, etching on the nanometer scale, and measurements of the step heights by interferometry. Using GI-XRF measurements and removal of the highly doped segregation layer by a sensitive etching process it was possible to distinguish clearly between the piled-up atoms and the arsenic atoms in the bulk over a large range of implantation doses, from 3×1012 to 1×1016 cm−2. The samples were annealed at different temperatures from 900 °C to 1200 °C for time periods long enough to make sure that the segregation reflects an equilibrium state. With additional step height measurements at line-space structures, the thickness of the layer with the piled-up arsenic and the shape of the segregation profile was determined. Electrical measurements indicated that the segregated arsenic atoms are deep d...

Diffusion and electrical activation of indium in silicon

In this work we investigate the diffusion and the electrical activation of In atoms implanted into silicon with energies ranging from 40 to 360 keV and doses of 5×1012 and 5×1013 In/cm2 during rapid thermal processing. Our investigation shows a clear dependence of In outdiffusion and electrical activation on the implant depth. For a fixed dose, the electrical activation was found to increase with the implant energy. We propose that the data can be explained by considering the balance between the local In concentration and the C background. The occurrence of coupling between the C present in the substrate and the implanted In, depending on the C/In ratio, may in fact give rise to significant formation of C–In complexes. Such complexes play a role in the enhanced electrical activation due to the shallower level they introduce into the Si band gap (Ev+0.111 eV), with respect to the rather deep level (Ev +0.156 eV) of In alone [R. Baron et al., Appl. Phys. Lett. 30, 594 (1977); R. Baron et al., ibid. 34, 257 ...

Simulation of Semiconductor Devices and Processes

Integrated micro electro mechanical systems (iMEMS) include sensors, actuators and circuits made by silicon IC technology combined with micromachining, deposition or electroplating. We present two essential iMEMS development tools: (i) the data base ICMAT of material parameters obtained from measuring process-dependent IC thin film electrical, magnetic, thermal and mechanical properties by using dedicated materials characterisation microstructures and (ii) the toolbox SOLIDIS, providing coupled numerical modelling of the electrical, magnetic, thermal and mechanical phenomena and their boundary and interface conditions occurring in iMEMS devices in a uniform and consistent environment.

Detailed arsenic concentration profiles at Si/SiO2 interfaces

The pile-up of arsenic at the Si/SiO2 interface after As implantation and annealing was investigated by high resolution Z-contrast imaging, electron energy-loss spectroscopy (EELS), grazing incidence x-ray fluorescence spectroscopy (GI-XRF), secondary ion mass spectrometry, x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, as well as Hall mobility and four-point probe resistivity measurements. After properly taking into account their respective artifacts, the results of all methods are compatible with each other, with EELS and GI-XRF combined with etching providing similar spatial resolution on the nanometer scale for the dopant profile. The sheet concentration of the piled-up As at the interface was found to be ∼1×1015 cm−2 for an implanted dose of 1×1016 cm−2 with a maximum concentration of ∼10 at. %. The strain observed in the Z-contrast images also suggests a significant concentration of local distortions within 3 nm from the interface, which, however, do not seem to involve in...

A reduced approach for modeling the influence of nanoclusters and {113} defects on transient enhanced diffusion

To simulate transient enhanced diffusion (TED) of dopants after ion implantation, a very accurate model for the interaction of self–interstitials with extended defects is indispensable. Recently, such a model has been published by Cowern including the formation of {113} defects via small self–interstitial clusters. Extracted from experimental results, this continuum model consists of a large set of coupled differential equations and, consequently, simulation times are rather high. In this letter, we present a model based on only seven differential equations leading to almost identical results in comparison to those of the original model. The reduction obtained will allow the application of the clustering model for the simulation of TED in commercial software tools.

Direct experimental evidence for diffusion of dopants via pairs with intrinsic point defects

Boron was implanted into silicon at a wafer temperature of 950 °C. The resulting boron profile showed a marked uphill diffusion at the surface and a very high diffusion enhancement. Initially homogeneously distributed antimony atoms showed remarkable redistribution effects after the implantation. These experiments allow the validation of diffusion theories, including the effects of point defect gradients on the migration of dopants. It will be shown that the experimental results agree well with the predictions of pair diffusion theories.

Comprehensive Study of the Electron Scattering Mechanisms in 4H-SiC MOSFETs

The effects of doping concentration and temperature upon the transport properties in the channel of lateral n-channel SiC MOSFETs have been studied using current-voltage and Hall-effect measurements. To interpret the electrical measurements, numerical TCAD simulations have been performed. A simulation methodology that includes the calculation of the Hall factor in the channel of SiC MOSFETs has been developed and applied. In addition, a new model for the bulk mobility has been suggested to explain the temperature dependence of the MOSFET characteristics with different background doping concentrations. Based on the good agreement between the simulated and the measured results, scattering mechanisms in the channel of SiC MOSFETs have been studied.