Sentaurus Topography 3D
1. Getting Started

1.1 Overview
1.2 Working With This Module
1.3 File Types
1.4 Starting Sentaurus Topography 3D
1.5 Parallelization

Objectives

• To introduce the features of Sentaurus Topography 3D.
• To demonstrate how to run Sentaurus Topography 3D.

1.1 Overview

Sentaurus Topography 3D is a three-dimensional simulator for evaluating and optimizing critical topography-processing steps such as etching and deposition. Structures composed of an arbitrary number of different materials can be handled.

Sentaurus Topography 3D simulates process steps on 3D structures. Nevertheless, the two-dimensional (2D) mode (for the level-set engine only) of Sentaurus Topography 3D makes the physical models available also for 2D structures. Therefore, both 2D and 3D structures can be simulated with the same physical models, with consistent results. This feature allows you to calibrate models efficiently and to save considerable simulation time when a 3D structure is invariant along one direction and, therefore, it can be represented by a 2D cut of the 3D structure. Simulations with the particle Monte Carlo (PMC) engine are always run in three dimensions. For the same model and similar accuracy, the PMC engine is, in general, significantly faster than the level-set engine, up to factors of 100 and more.

The Sentaurus Process and Sentaurus Interconnect tools support a subset of Sentaurus Topography 3D functionality for advanced physical etching and deposition modeling (with both the level-set and PMC engines). This integration enables users of Sentaurus Process and Sentaurus Interconnect to easily incorporate one or more etching and deposition process steps into their simulation flow without having to create a separate command file and simulation node for Sentaurus Topography 3D.

Moreover, advanced lithography processes can be simulated with Sentaurus Topography 3D by invoking Sentaurus Lithography commands from within Sentaurus Topography 3D.

1.2 Working With This Module

This module presents the following examples:

• Setting up a basic simulation with built-in level-set etching and deposition models
• Setting up simulations using the rate formula module (level-set engine)
• Setting up simulations with the PMC engine for etching and deposition

In the context of these examples, the most widely used Sentaurus Topography 3D commands are introduced for generating the initial structure, defining models, setting model parameters, performing the simulation, saving the final structure, and analyzing the simulation results.

This module discusses only the parameters and options used in the examples. For comprehensive model descriptions, refer to the Sentaurus™ Topography 3D User Guide.

A link to Sentaurus Topography 3D command files is given in each section. You are encouraged to create a local copy of the command file (choose File > Save As) and to run it. Some examples are given as packaged Sentaurus Workbench projects. After creating a local copy, the files can be opened with Sentaurus Workbench.

1.3 File Types

The main file types used in Sentaurus Topography 3D are:

• Command file (*.cmd)
  This is the main input file for Sentaurus Topography 3D, containing all the simulation commands. It also can contain Tcl commands and is referred to as the command file or input file.
  
• Log file (*.log)
  Sentaurus Topography 3D generates this file during a run. It contains information about the initial structure definition, processing steps, computation mode, and the boundary conditions used in them, as well as information about the final structure saved. The amount of information written to the log file is controlled by the log_level parameter, which can be set globally with the let command. Possible values for log_level are info (default), all (more information is logged), and error (only error information is logged).
  
• TDR boundary file (*.tdr)
  This file stores the boundaries of the structure and surface plots, and can be loaded into Sentaurus Visual for visualization. The initial structure can be read from a TDR boundary file. Its name can be specified with the file parameter of the define_structure command of Sentaurus Topography 3D. The final structure is saved in the TDR boundary file format as well and can be used for further processing, for example, in Sentaurus Process or Sentaurus Structure Editor.

1.4 Starting Sentaurus Topography 3D

Sentaurus Topography 3D can be run either from within Sentaurus Workbench or on the command line. The command file, which contains the command sequence for the simulation, can be specified on the command line when starting Sentaurus Topography 3D, for example:

> sptopo3d input.cmd

1.5 Parallelization

In Sentaurus Topography 3D, the source of reactants (in most cases, a plasma) consists of two kinds of particle: neutrals and ions. Neutral and ion fluxes can interact with the surface according to different physical effects. Neutrals can react with or can be reemitted from the surface. Ions can react with the surface, or can be reflected from the surface, or can sputter away the surface material itself.

Sentaurus Topography 3D offers different numeric methods to compute the distribution of neutral and ion particles over the surface, taking into account the modeled physical effects: the radiosity method (used by default) and the Monte Carlo method. For detailed information about physical and numeric modeling, refer to the Sentaurus™ Topography 3D User Guide.

The Monte Carlo method can use multiple CPU cores or CPUs to accelerate simulations on shared-memory computers. To activate multithreaded computation, use the command:

let parallel=true

You also need to specify explicitly the number of threads to be used with the command:

let num_threads=<n>