Impurity Diffusion In Silicon Research Articles

Effect of Oxidation Enhanced Diffusion on Hot Carrier Injection Induced Degradation in N-Type High-Voltage DDDMOSFET

This paper investigates how the oxidation enhanced diffusion effect influences the reliability of hot carrier injection (HCI) in N-type high-voltage double-diffused drain MOSFET (DDDMOSFET). The oxidation enhanced diffusion influences impurity diffusion in silicon evidently, thus changes the device characteristic and reliability. By NDD drive-in at high temperature with N2 + O2 mixed atmosphere, we make use of the oxidation enhanced diffusion effect in NDD region of N-type HV DDDMOSFET to improve the HCI reliability. And the results are accordant with reliability simulation of TCAD softwar.

Observation of iron impurity diffusion in silicon under bending stress by Mössbauer spectroscopy

External bending stress was applied to a 57Fe-doped n-type silicon wafer, and transmission Mossbauer spectra were measured at room temperature in order to observe directly stress induced diffusion of 57Fe atoms in the silicon matrix. As the stress is increased up to 23 MPa, the resonance area of the substitutional Fes component is found to decrease by more than 30%. In addition, a line broadening can be clearly seen in the interstitial Fe $_{\rm i}^{0}$ component, corresponding to a jump frequency of 106 s − 1. This diffusion process is interpreted to be due to the fast jumps between interstitial sites, following a formation jump of interstitial Fe $_{\rm i}^{0}$ from substitutional Fes.

Control of impurity diffusion in silicon by IR laser excitation

We report a first-time attempt of diffusion control of impurities by IR excitation, by using an intensive synchrotron radiation facility, BL43IR of SPring-8. Although the result is discouraging, the plan, experimental setup, irradiation experiment, and the result on the impurity diffusion, are described in detail, in hoping improvement of experiment in the future. It is suggested that the input power employed in the present experiment is not enough to observe the intended results.

Control of impurity diffusion in silicon by IR laser excitation

Control of the diffusion of a specific impurity species is desirable in Si device processes. IRlaser excitation matching the impurity vibration mode is a promising method for thispurpose. To illustrate the effectiveness of this method, first-principles moleculardynamics simulation has been applied. Technical issues of the simulation aredescribed in detail. It is seen that resonant effects can be reproduced in adiabaticmolecular dynamics simulations by applying an external force on the impurity only.The present study forms the basis for further developments of this approach.

Self and Impurity Diffusion in Si - Simulation by Chandrasekhar-Hopping

A novel attempt is made to study the diffusion in silicon by a simulation procedure known as Chandrashekarhopping. The method employed by Chandrasekhar on the astronomical bodies is brought down to the microscopic real systems in the present investigation and the procedure is applied for the study of self and impurity diffusion in silicon. The Fokker-Planck form of the Fick's law is used and a smooth continuous position probability density for the diffusing particle ω(r, t), which represents the position of the diffusing particle at any time t, is used for the evaluation of the diffusion constant. The results agree reasonably well with the available experimental and theoretically reported values. The existence of 'traps' in the semiconducting media is also clearly demonstrated.

Monte Carlo study of vacancy-mediated impurity diffusion in silicon

We present a kinetic lattice Monte Carlo study of the behavior of a dopant flux driven by a vacancy gradient, associated with the diffusion of substitutional impurities via a vacancy mechanism in silicon. Recent ab initio results are used for a quantitative description of the impurity-vacancy interaction. We find a dopant flux smaller than, but in the same direction as, that predicted by the pair diffusion model, with the deviation greatest at high temperatures.

Atomistic analysis of the vacancy mechanism of impurity diffusion in silicon

The complete set of the four macroscopic transport coefficients describing the coupled diffusion of impurity atoms and vacancies in silicon is calculated from the atomistic mechanism by accurately taking into account the effects of the microscopic forces between dopants and vacancies. The aim of these simulations is to come to a decision concerning the validity of models like the pair diffusion model [e.g., M. Yoshida, J. Appl. Phys. 48, 2169 (1977); R. B. Fair and J. C. C. Tsai, J. Electrochem. Soc. 124, 1107 (1977); F. F. Morehead and R. F. Lever, Appl. Phys. Lett. 48, 151 (1986); B. J. Mulvaney and W. B. Richardson, Appl. Phys. Lett. 51, 1439 (1987)] or the “non-Fickian diffusion” model [M. Kurata, Y. Morikawa, K. Nagami, and H. Kuroda, Jpn. J. Appl. Phys. 12, 472 (1973); Y. Morikawa, K. Yamamoto, and K. Nagami, Appl. Phys. Lett. 36, 997 (1980); V. V. Kozlovski, V. N. Lomasov, and L. S. Vlasenko, Radiat. Eff. 106, 37 (1988); O. V. Aleksandrov, V. V. Kozlovski, V. V. Popov, and B. E. Samorukov, Phys. Status Solidi 110, K61 (1988), K. Maser, Exp. Tech. Phys. (Berlin) 34, 213 (1986), K. Maser, Ann. Phys. (Leipzig) 45, 81 (1988), K. Maser, Exp. Tech. Phys. (Berlin) 39, 169 (1991)] that make contradicting predictions for very fundamental properties like the relative direction of the fluxes of dopants and vacancies driven by a vacancy gradient and for the relation α=Td0/Dd0 between two of the four transport coefficients. Simulation results are shown for a variety of assumed interaction potentials that establish a functional dependence between α and measurable quantities, like the factor Dd/Dtracer of enhancement of dopant diffusivity over tracer diffusion, that holds for an arbitrary interaction. The comparison with experimental values for Dd/Dtracer leads to confirmation of the pair diffusion model for boron and phosphorous. For arsenic and antimony, the large scatter of the experimental data prohibits an equally definite conclusion, but at least a qualitative confirmation of pair diffusion theory (i.e., α>0 which means that dopant and vacancy fluxes have the same direction if caused by a vacancy gradient) is possible.

Atomistic modeling of high-concentration effects of impurity diffusion in silicon

The vacancy mechanism of dopant diffusion in silicon is investigated on a microscopic model level. The concentration dependence of the dopant diffusion constant in the high-concentration regime is simulated using the Monte-Carlo method and an atomistic model of clustering and precipitation. The simulation takes into account the microscopic forces between particles (dopant atoms and vacancies) in a quantitative manner. Since sufficiently accurate data for the binding strength and shape of the interaction potentials are not available, we analyze a variety of model approaches for these interactions to come to general conclusions for the macroscopic consequences of microscopic models. First, pure attractive forces between dopants and vacancies as usually assumed in the literature [S. M. Hu, Phys. Status Solidi B 60, 595 (1973)] are discussed. In contradiction to previous results from the literature [S. T. Dunham and C. D. Wu, J. Appl. Phys. 78, 2362 (1995)] we find that with this approach it is not possible to fit the experimental results. Also, models with repulsive dopant–dopant potentials of Coulomb shape together with attractive dopant–vacancy forces are found to give unrealistic results. On the other hand, a good fit to the experimental data is obtained with the assumption of a nonbinding dopant–vacancy interaction that only increases the mobility of the vacancy in the neighborhood of a dopant. The parameters of the atomistic potential are derived from a fit of the simulations to the experimental values. The simulation results for the different microscopic approaches are also used to give an assessment of the validity of models for high-concentration diffusion that are based on percolation theory [D. Mathiot and J. C. Pfister, J. Phys. (France) Lett. 43, L-453 (1982); D. Mathiot and J. C. Pfister, J. Appl. Phys. 66, 970 (1989)].

Thermodynamics of diffusion under pressure and stress: Relation to point defect mechanisms

A thermodynamic formalism is developed for illuminating the predominant point defect mechanism of self- and impurity diffusion in silicon and is used to provide a rigorous basis for point defect-based interpretation of diffusion experiments in biaxially strained epitaxial layers in the Si–Ge system. A specific combination of the hydrostatic and biaxial stress dependences of the diffusivity is ±1 times the atomic volume, depending upon whether the predominant mechanism involves vacancies or interstitials. Experimental results for Sb diffusion in biaxially strained Si–Ge films and ab initio calculations of the activation volume for Sb diffusion by a vacancy mechanism are in quantitative agreement with no free parameters. Key parameters are identified that must be measured or calculated for a quantitative test of interstitial-based mechanisms.

Impurity Diffusion in Silicon Based on the Pair Diffusion Model and Decrease in Quasi-Vacancy Formation Energy. Part Two: Arsenic

One of the experimental characteristics of As diffusion in Si is that the As diffusion coefficient is independent of its surface concentration but increases approximately linearly with electrically active As concentration. From the viewpoint of the pair diffusion model (PDM), this means that the excess vacancies are not generated and vacancies are in the thermal equilibrium state. Arsenic diffusion is studied on the basis of PDM, taking account of the decrease in quasi-vacancy formation energy. With the decrease in quasi-vacancy formation energy, the binding energy between an As atom and a vacancy also decreases. Fermi level obtained from the Boltzmann statistics is used. Using the literature data for the self-diffusion coefficient of vacancy mechanism and the As diffusion coefficient, the experimental arsenic concentration profile can be well explained.

Impurity Diffusion in Silicon Based on the Pair Diffusion Model and Decrease in Quasi-Vacancy Formation Energy. Part One: Phosphorus

The binding energy, E b, between a vacancy and a P atom or an As atom in Si is large. Therefore the pair diffusion model (PDM) and the decrease in quasi-vacancy formation energy are applicable to P and As diffusions. With the decrease in quasi-vacancy formation energy, E b also decreases. Fermi level obtained from the Boltzmann statistics is used. Anomalous diffusion of P consists of two components, a tail and a plateau. The tail has been attributed to excess vacancies, the generation of which is a characteristic of PDM. The plateau has been explained by PDM and the decrease in quasi-vacancy formation energy. The reason for this is given for the first time. It is emphasized that the large value of the phosphorus effective diffusion coefficient at the plateau is not anomalous but normal.

Impurity Diffusion in Silicon under Strong Interaction with the Point Defect Clusters

Impurity Diffusion in Silicon under Strong Interaction with the Point Defect Clusters

The Role of Vacancies and Self-Interstitials in Impurity Diffusion in Silicon

The Role of Vacancies and Self-Interstitials in Impurity Diffusion in Silicon

PEPPER-a process simulator for VLSI

PEPPER is a computer program that simulates in one dimension the ion implantation, diffusion, oxidation, epitaxy, deposition, and etch processes used in VLSI technology. The program contains an efficient Monte Carlo ion implantation algorithm that includes explicit calculation of ion channeling and damage. The key feature of the diffusion calculation is a general partial differential equation solver for rapid prototyping of physical models. The solver has been used to develop several unique diffusion models. A novel model for impurity diffusion in polysilicon treats the problem as a two-stream process, with relatively slow standard diffusion within the grain and a much more rapid component of diffusion along the grain boundaries. The two components are coupled at each point by a segregation term. Two other models for impurity diffusion in silicon include explicit calculation of the coupling of point defects with impurities. One of the point-defect models is a general and detailed formulation from a chemical kinetics viewpoint, while the other makes further assumptions to simplify the model for engineering analysis. >

Mechanisms of equilibrium and nonequilibrium diffusion of dopants in silicon.

We have developed a theory of impurity diffusion in silicon under equilibrium and nonequilibrium concentrations of point defects. The results of first-principles calculations of several key quantities are combined with this theory and compared to experimental data. We find that vacancies and self-interstitials mediate the equilibrium diffusion B, P, and As with comparable activation energies, but interstitials are domoinant. Sb diffusion, on the other hand, is mediated primarily by vacancies. We also find that the direct-exchange mechanism plays only a minor role for all dopants studied.

A Steady-State Model for Coupled Defect Impurity Diffusion in Silicon

AbstractWe extend our earlier model which was proposed to explain tails in the diffusion profiles of high concentration boron and phosphorus in silicon. Our quasi-steady-state approach is generalized here to include both vacancies (V) and interstitials (I) at equivalent levels. I-V recombination is regarded as near local equilibrium, occurring through reactions of the defects with defect-impurity pairs. This approach leads to the well-known plateau, kink and tail in high surface concentration P diffusions in Si and to the less well recognized tails in B as well. Our extended model, in its simplest form, allows a more complete and less restrictive treatment of Au diffusion in Si. An important advantage is the direct inclusion of these defect-impurity interactions and the resulting gradients in the defect concentrations.

Atomic Diffusion Processes in Silicon

AbstractThe mechanisms of self-diffusion and dopant impurity diffusion in silicon have been the subject of intense debate since the 1960’s. Until the mid-1980’s, there was only limited experimental information and virtually no theory. In the last five years, however, first-principles calculations of many key quantities and new experimental data have led to significant progress. This paper traces the major theoretical advances and the key experimental data that have resolved many controversies and have provided a fairly comprehensive picture of diffusion processes. Theory has also recently provided detailed microscopic information about the diffusion of interstitial hydrogen.

Impurity diffusion in silicon enhanced by low energy ion bombardment: V E Borisenko,Minsk Radioengineering Institute, P. Browka 6, 220600 Minsk, USSR

Impurity diffusion in silicon enhanced by low energy ion bombardment: V E Borisenko,Minsk Radioengineering Institute, P. Browka 6, 220600 Minsk, USSR

Unified model for impurity diffusion in silicon

A new theoretical framework for impurity diffusion in silicon is proposed. The basic mechanism employed here is the point defect-impurity pair diffusion as presented by Mulvaney and Richardson [Appl. Phys. Lett. 51, 1439 (1987)] in a generalized description of the impurity-interstitial model by Morehead and Lever [Appl. Phys. Lett. 48, 151 (1986)]. The model consists of coupled equations for the impurities and point defects, in which all species including structural defects (major new process variables) are treated on the same footing. Among other things, the model accounts for long-range point defect mediated enhancement and retardation of the diffusion. The essential features of the present formalism are the new equations for interstitials and vacancies which provide the major coupling between the impurities apart from the coupling via the Fermi level. This approach allows, for the first time, a consistent analysis and exploration of the diffusion phenomena step by step on various levels of complexity.

Model for defect-impurity pair diffusion in silicon

A new model for impurity diffusion in silicon by a point defect-impurity pair mechanism is described. A pair of coupled, nonlinear, partial differential equations for the silicon self-interstitial and the impurity is derived and solved numerically. The familiar kink and tail of phosphorus and, to a lesser extent, boron diffused profiles arise naturally from the solution. The coupling between defect and impurity becomes smaller at high temperatures and at low impurity concentrations, in agreement with experimental observations. The transient buildup of the defect concentration may have implications for models of rapid thermal processes.