Front end process simulation is an invaluable tool in assessing current and future process options. This review describes the application of process simulation in modeling geometry, doping and stress effects in advanced logic processes. Continuum and atomistic approaches, both necessary to capture the physics involved with the most advanced options, are discussed. Also detailed are advancements in numerical techniques which enable the efficient and robust simulation necessary to keep pace with technology development.

This paper describes advances and remaining challenges in unstructured 3D meshing techniques for both process and device simulations and parallelization of the process simulator FLOOPS. The meshing is performed using a point cloud manager to create points and an unstructured tetrahedral mesher. Distributed parallel techniques are used to parallelize the sparse matrix assembly and solution for 3D process diffusion simulations.

Boron is introduced into silicon via implantation to form p-type layers. This process creates damage in the crystal that upon annealing causes enhanced diffusion and clustering of the boron layer. Reactivation of the boron is not a well-understood process. In this letter we experimentally investigate the effect of the annealing ambient on boron reactivation kinetics. An oxidizing ambient which injects silicon interstitials is compared to an inert ambient. Contrary to published theory, an excess of interstitials does not accelerate the reactivation process.

This paper presents an integrated modeling approach to address diffusion and activation challenges in sub-90 nm CMOS technology. Co-implants of F and Ge are shown to reduce diffusion rates and a new model for the interactive effects is presented. Complex codiffusion behavior of As and P is presented and modeling concepts elucidated. Tradeoffs such as sheet resistance for a given junction depth, and how these depend on impurities, as well as soak vs. spike rapid thermal anneals (RTA), can be understood with simulation models.

In this work, a series of 13 boron implants were performed into Czochralski silicon substrates with doses of 2×1014–1.6×1015 cm−2 at energies of 10–80 keV. The boron was deliberately clustered with a 750 °C anneal of 10 or 30 min and the electrical activation of the boron implants was determined following a second anneal at 750 or 850 °C with a Hall effect system with certain samples also being analyzed with a spreading resistance technique. Analysis of the reactivation rates allows for the determination of the net energy to boron reactivation to be approximately 3.0 eV assuming the reactivation process is mediated by release of a boron interstitial with a migrational energy of 0.3 eV. This results in a critical binding energy of approximately 2.7 eV from the process limiting the dissolution of the most stable boron-interstitial cluster.

We present results from predictive atomic level simulation of boron diffusion in silicon under a wide variety of implant and annealing conditions. The parameters for this simulation have been extracted from first principles approximation models and molecular dynamics simulations. The results are compared with experiments showing good agreement final cases. The parameters and reactions used have been implemented into a continuum-level model simulator.

Boron-doped well structures formed in Czochralski silicon are subjected to a self-implant and various anneals to form a population of type {311} defects. Quantitative transmission electron microscopy is then used to measure the residual interstitials trapped in the {311} defects as a function of boron concentration and anneal temperature. We have found a strong tendency for increased dissolution rates of {311} type defects at boron concentrations above 1018 cm−3, providing direct evidence for the formation of boron–interstitial clusters. By profiling the samples with secondary ion mass steptroscopy and comparing the results to spreading resistance measurements the degree of deactivation can be determined.

A physically-based continuum diffusion/clustering model has been applied to the simulation of transient activation/reactivation of ion implanted boron. This work is aimed at the optimization and development of post-implant thermal cycles for minimal dopant diffusion with peak activation. This model has been successfully applied to the simulation of several new structures exhibiting partial deactivation of the implanted boron.

Boron doped structures are difficult to model due to transient enhanced diffusion (TED) and defect driven clustering. The purpose of this work is to develop a new model which predicts both the defect enhanced diffusion and the defect enhanced clustering. This will enable better prediction of both threshold adjust implants and shallow boron profiles for P+ source/drain structures. This paper presents a novel approach to the development of predictive boron diffusion and clustering models based upon fundamental physical calculations performed at Lawrence Livermore National Laboratories. A continuum model has been developed, based entirely upon these energetic calculations, which is capable of accurately simulating the diffusion, clustering and subsequent reactivation of boron for a wide variety of implant and anneal conditions. As a direct consequence of this work, a mechanism has been discovered which has been shown capable of accurately modeling the surface dose loss of boron in silicon following the annealing of damage induced by shallow boron implants.

Transient Enhanced Diffusion (TED) is one of the biggest modeling challenges present in predicting scaled technologies. Damage from implantation of dopant ions changes the diffusivities of the dopants and precipitates to form complex extended defects. Developing a quantitative model for the extended defect behavior during short time, low temperature anneals is a key to explaining TED. This paper reviews some of the modeling developments over the last several years, and discusses some of the challenges that remain to be addressed. Two examples of models compared to experimental work are presented and discussed.