General trends in integrated circuit technology toward smaller device dimensions, lower thermal budgets, and simplified processing steps present severe physical and engineering challenges to ion implantation. These challenges, together with the need for physically based models at exceedingly small dimensions, are leading to a new level of understanding of fundamental defect science in Si. In this article, we review the current status and future trends in ion implantation of Si at low and high energies with particular emphasis on areas where recent advances have been made and where further understanding is needed. Particularly interesting are the emerging approaches to defect and dopant distribution modeling, transient enhanced diffusion, high energy implantation and defect accumulation, and metal impurity gettering. Developments in the use of ion beams for analysis indicate much progress has been made in one-dimensional analysis, but that severe challenges for two-dimensional characterization remain. The ...

Ion beams in silicon processing and characterization

The fabrication of thin, sub-40 nm doped layers in Si with high concentrations of electrically active dopants and box-like profiles is a major technological challenge. Making these regions without introducing residual defects in the material and without affecting the properties of other material regions in the device is even more difficult. The need to control these properties of doping profiles in ultra-large-scale integrated (ULSI) circuits has driven the study of low energy implantation, transient enhanced diffusion (TED), and focused the search fornew shallow junction doping techniques. In this article, wereview the motivation for shallowjunctions, specific requirements for shallow junctions used in deep sub-micron dimension metal-oxide-semiconductor field effect transistors (MOSFETs), current understanding of implant and diffusion processes, and the state-of-the-art in low energy implantation and a number of alternate doping technologies, including plasma implantation, gas-immersion laser (GILD) doping, rapid vapor-phase doping (RVD), ion shower doping, and decaborane (B10H14) implantation.

Shallow junction doping technologies for ULSI

Two-dimensional implanted dopant distributions at mask edges are studied using the Monte Carlo code IMSIL. The models implemented in the program are reviewed. An empirical model of electronic stopping describes correctly the range of channeled B, P, and As ions in a wide energy range. The damage model takes defect recombination into account but does not require the simulation of recoil cascades. Two-dimensional dopant distributions are calculated by randomly selecting the starting points of the ions between two positions defining a mask opening. The simulation results show that the penetration below the mask is larger than expected and that a Gaussian function is inappropriate to describe the lateral distribution function. The discrepancy increases with decreasing implantation energy. The dependence of the two-dimensional profiles on mask edge orientation, tilt angle, and ion species, and the influence of a screening oxide are investigated.

Monte Carlo simulation of two-dimensional implanted dopant distributions at mask edges

The formalism for the binary collision code Crystal-TRIM which simulates ion implantation effects in crystalline solids is presented The treatment of binary collisions, the kinematics and the crystal description are elucidated in detail The nuclear scattering is described by the ‘universal’ potential The scattering angles are calculated by semianalytical and analytical formulae We employ a semiempirical model to describe the electronic stopping of the ions Thermal vibrations of lattice atoms, the radiation-induced production of vacancies and interstitials and their accumulation, the generation of static lattice disorder due to electronic energy deposition and the influence of a thin amorphous surface layer are considered in the simulation model The program Crystal-TRIM is applied to calculate range profiles for P+ and B+ implantation into Si at energies between 500 keV and 1 MeV, at ion incidence into axial and planar channels and into ‘random’ directions, and at ion doses between 1013 and 

Crystal-trim and its application to investigations on channeling effects during ion implantation

Numerous profile evolution simulation studies strongly suggest that ions reflecting with glancing angles from etched feature sidewalls are responsible for microtrench formation at the feature bottom. Within these studies such reflections are traditionally assumed specular, where the ion retains all of its incident energy. In this study, we gauge the validity of that assumption by describing the distributions of reflected ion energies, Er, reflected ion angles (polar, θr; azimuthal, φr; and total scatter, αr), obtained via MD simulations of Ar+ bombardment of model SiO2 surfaces. We modeled the physics of the surface atom interactions using an empirical interatomic potential energy function developed by Feuston and Garofalini [J. Chem Phys. 89, 5818 (1988)]. We considered Ar+ ion energies, Ei, of 100 and 200 eV, and incident polar angles, θi, of 0°, 30°, 45°, 60°, 75°, and 85°, measured from the macroscopic surface normal. Each (Ei,θi) combination was used to generate a unique roughened model oxide surface...

Energetic ion bombardment of sio2 surfaces : molecular dynamics simulations

An improved Monte Carlo simulation model has been developed for boron implantation into single-crystal silicon. This model is based on the Marlowe Monte Carlo code and contains significant improvements for the modeling of ion implantation, including a newly developed local electron concentration-dependent electronic stopping model and a newly developed cumulative damage model. These improvements allow the model to reliably predict boron implant profiles not only as a function of energy, but also as a function of other important implant parameters such as tilt angle, rotation angle, and dose. In addition, profiles of implant generated point defects (silicon interstitials and vacancies) can be calculated. >

Monte Carlo simulation of boron implantation into single-crystal silicon

Ion-implantation-induced damage in crystalline material can cause the shape of implanted impurity distributions to vary strongly with dose. We have developed a model which directly simulates the accumulation of this damage and the effect it has on the trajectories of subsequently implanted ions. Comparison with experimental profiles of boron implantation into single-crystal silicon indicates that this model accurately predicts the onset and effects of this cumulative damage. Additionally, distributions of the point defects formed during implantation which reflect the expected influence of varying implant energies, tilt and rotation angles, and doses are given by this model.

Modeling of cumulative damage effects on ion-implantation profiles

A semi-empirical approach for modeling of ion-implanted impurity distributions has an inherent advantage of high computational efficiency which is a vital issue for the simulation of a large number of processing steps required in the fabrication of high density integrated circuits with submicrometer feature sizes. The accuracy of this modeling technique has been substantially improved with the introduction of the dual Pearson modeling approach for simulation of implanted impurity distributions in single-crystal silicon so that the entire profile, including the broad channeling tail, is accurately predicted[1]. The dual Pearson modeling approach is based on the use of two Pearson functions describing two scattering mechanisms encountered in ion implantation into single-crystal silicon. Since semi-empirical approaches are based on experimental data, it is crucial to maintain a sizable data base of modeling parameters extracted from measured profiles in order to fully exploit the advantages of semi-empirical approaches. In this paper, a computer program which extracts all nine parameters for the dual Pearson modeling approach will be introduced. This program provides an easy and efficient way of extracting very accurate parameters in a two-step extraction process. The first step obtains a preliminary set of nine parameters which is then used as the initial condition for the second step in which the Levenberg-Marquardt algorithm is used to find the final set of accurate parameters. The incorporation of the first step for self-generation of the initial conditions makes the program easy to use, even for those with no previous experience with Pearson functions or the curve-fitting processes.

Kevin M. Klein

Papers

Monte Carlo simulation of boron implantation into single-crystal silicon

Modeling of cumulative damage effects on ion-implantation profiles

Efficient modeling parameter extraction for dual pearson approach to simulation of implanted impurity profiles in silicon

Analysis of the Tilt and Rotation Angle Dependence of Boron Distributions Implanted into Silicon

Critical Angles for Channeling of Boron Ions Implanted into Single‐Crystal Silicon