Norbert Strecker

Atomistic simulation of ion implantation and its application in Si technology

Atomistic computer simulations based on the binary collision approximation (BCA) are very well suited to predict the dependence of as-implanted dopant profiles on implant parameters like energy, dose and direction of incidence as well as on the arrangement of oxide, poly-Si and other materials on the single-crystalline Si substrate. In particular channeling effects, the enhanced dechanneling due to accumulation of radiation defects during ion bombardment and due to pre-existing ion-beam-induced defects can be simulated in a reasonable manner. The BCA code Crystal-TRIM was successfully integrated into 1D and 2D process simulators for the Si technology. The application of the trajectory splitting algorithm and the lateral duplication method ensures a high computational efficiency.

Viscoelastic material behavior: models and discretization used in process simulator DIOS

It is a known fact that melted glass, such as SiO/sub 2/, shows viscoelastic behavior. But in the range of processing temperatures the mechanical properties of SiO/sub 2/ vary strongly. While below 800/spl deg/C the material behaves like an elastic solid, at temperatures above 1000/spl deg/C it shows nearly pure viscous properties. In this paper, the governing equation, the so-called constitutive equation, describing viscoelastic behavior, and its discretization are presented. The oxide viscosity depends on the local amount of shear stresses which leads to inhomogeneous material behavior and a nonlinear theory. This new mechanical model was implemented into the process simulator DIOS-ISE. Some obtained simulation results are shown and discussed.

Damage calibration concept and novel B cluster reaction model for B transient enhanced diffusion over thermal process range from 600/spl deg/C (839 h) to 1100/spl deg/C (5 s) with various ion implantation doses and energies

We propose to use a fixed damage factor combined with an effective dose to generate an initial interstitial silicon concentration profile at a given B ion implantation conditions and demonstrate that this methodology can readily explain transient enhanced diffusion (TED) in almost all relevant cases of practical VLSI processing. We also developed a B cluster reaction model which enables us to tune time evolution of active B profiles in a flexible way.

Exploring Methods for Adequate Simulation of Sub-100nm Devices

Analysis of the current trends in the semiconductor industry suggests that a number of novel simulation methods need to be explored. Several interdisciplinary simulation tools ranging from lithography and optical proximity correction to 3D continuum and atomistic process models have been integrated into a single simulation flow. Application of this tool suite to a typical 100nm nchannel MOSFET reveals a number of 3D effects that considerably impact its performance.

Analytical models for transient diffusion and activation of ion-implanted boron during rapid thermal annealing considering ramp-up period

Analyzing experimental boron transient diffusion profiles in Si MOSFETs over a wide temperature range with the process simulator TESIM, we evaluated the related transient diffusion time t/sub E/, enhanced diffusivity D/sub enh/, and maximum transient diffusion concentration C/sub enh/. Our extracted values contradict previously reported values, but it is due to the fact that the former works neglected the ramp-up period. We show that considering the ramp-up period is indispensable for the analysis of transient diffusion. We also developed analytical models for t/sub E/, D/sub enh/, and C/sub enh/, and clarified their dependence on physical parameters implemented in TESIM.

Atomistic simulation of ion implantation into 2D structures

The successful integration of the binary collision code Crystal-TRIM into the 2D-process simulator DIOS as an optional module is reported. The new module is applied to the simulation of the formation of LDD-like structures. The use of a trajectory split method in combination with a mechanism for the lateral duplication of ion trajectories enables the simulation of the implantation step in extended targets with good depth and lateral resolution within reasonable computation times.

Precipitation phenomena and transient diffusion/activation during high concentration boron annealing

The understanding of low thermal budget transient diffusion and activation of shallow p+ implants remains a crucial issue of technology simulation. In this paper, we apply a coupled point defect assisted diffusion/precipitation model to the redistribution phenomena observed during annealing of shallow boron implants. Comparison with experimental data shows that the precipitation model can account for unusual segregation phenomena in the highly disordered zone around the projected range of the as-implanted profile.

Multi-Dimensional TCAD: The PROMPT/DESSIS Approach

Designing new semiconductor devices for very large scale integrated circuits (VLSI) requires intensive use of process and device simulation tools to reduce development costs. However, valid device simulation results can only be achieved when a high geometrical modeling precision has been reached during the process simulation phase. Accurate finite element simulators embedded in a multi-dimensional process simulation environment help to fulfill this quality requirement. Since general-purpose three-dimensional (3D) process simulators are not yet available, a modern design environment combines solid modeling techniques with one-dimensional (1D) and two-dimensional (2D) finite element simulators. In this article we present a consistent and integrated process simulation environment that eases the characterization and optimization of semiconductor devices. The straightforward modeling in all three dimensions of an EEPROM cell illustrates the presented approach.

A Hybrid Approach for Building 2D and 3D Conforming Delaunay Meshes Suitable for Process and Device Simulation

We present the latest results of our research regarding meshes suitable for both process and device simulation. Two major results are discussed in this paper: a consistent multi-dimensional mesh quality definition and a new hybrid multi-dimensional mesh generation approach. The consistent definition achieved is based on the conditions imposed by the Box integration method applied for both semiconductor process and device equations. The hybrid approach developed reaches a consistent mesh quality in all dimensions and it overcomes the severe limitations of our former mesh generators. Finally, it has been experimentally demonstrated that both the unified conditions and the hybrid approach are suitable for stable discretization schemes for device simulations based on the Box method.

Damage Accumulation by Arsenic Ion Implantation and Its Impact on Transient Enhanced Diffusion of As and B

Utilizing buried layer substrates into which As was ion implanted at the surface, we evaluated the damage factor associated with As ion implantation, and succeeded in explaining the transient enhanced diffusion of buried layer B as well as the surface As redistribution.