Sheldon Aronowitz

Dopant diffusion control in silicon using germanium

Theory and experiment reveal that germanium, in large quantities and when integrated in the crystalline silicon environment, has a long range influence on electrically active dopant species. In regions having very high concentrations of substitutional germanium, calculations predict, and experiments confirm, sharp distinctions between the diffusion pattern exhibited by n‐type dopants and the diffusion pattern produced by p‐type dopants. n‐type dopant diffusion, whether the species occupies a substitutional site or an interstitial position, is predicted and observed to be retarded through regions of very high concentrations of germanium. On the other hand, the dual behavior pattern for p‐type dopants, predicted successfully, results in diminished diffusion of interstitial dopant but enhanced diffusion when the species occupies a substitutional site.

Dopant diffusion in silicon in the presence of other dopants: A new predictive approach based on modeling boron and phosphorous diffusion in germanium‐rich regions of silicon

The effect of dopant‐dopant interaction on diffusion in silicon for a specific set of impurities is modeled. The first step in the modeling process involved quantum chemical calculations. The connection between the atomic scale results and macroscopic behavior was made through the medium for transmission of interactions between dopants. The molecular orbitals of the lattice system comprise that medium; consequently, interactions can be transmitted, with minimal reduction in magnitude, over separations of hundreds of lattice spacings. Macroscopically, additional flux components are generated that modify the conventional expression of Fick’s second law. Detailed simulation of boron and phosphorous diffusion in germanium‐rich regions of silicon illustrate the power of this approach to successfully model and predict the complex behavior exhibited by a particular set of interacting dopant species.

Dopant diffusion in semiconductors moderated by dopant‐dopant interactions. II. Extension of theory and application to boron and gallium in silicon

A macroscopic theory of dopant diffusion moderated by dopant‐dopant interactions is extended to include three‐dimensional effects. Application to dopant diffusion in thin crystalline silicon films when a second dopant, present in high concentration and distributed uniformly throughout the film, results in unanticipated predicted dependency on thickness for very thin films. Further application to boron‐gallium diffusion patterns in silicon illustrate the success of the theory to describe relatively fast diffusing dopant species that also are strongly interacting.

NASFLOW, a simulation tool for silicon technology development

A simulation system is described for linking two-dimensional simulators for process and device to a parameter extraction program, for the purpose of generating artificial parameters for the circuit analysis program, NASPICE. A key feature of the system is that it operates under the control of a shell program which offers a simple and easy to use interface to the user. Results of an initial development using the program sequence SUPRA = > PISCES = > CADPET = > NASPICE are described. Good correlation was obtained between system generated drain characteristics and silicon for both N and P-channel MOS transistors, and similarly for CMOS DC transfer characteristics.