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One dimensional process and device simulation using spreadsheets  

Authors
 Krupkina T.Yu.
 Krasukov A.Yu.
 Artamonova Ye.A.
Date of publication
 2016

Abstract
 Device simulation programs for one-dimensional modeling of MIS-structures and p-n-junctions, and silicon process simulation tools were created using spreadsheets.
Development of new semiconductor devices and process flows is almost impossible without process and device simulation. Usually it is necessary to estimate dependencies of the device parameters (such as threshold voltage, gate capacitance, breakdown voltage) versus the process modes (such as ion implantation dose and energy, oxidation and doping diffusion time and temperature).
Existing commercial simulation tools – TCAD form Synopsys [1] or Silvaco [2] are widely used for multidimensional modelling of different semiconductor devices and processes.
However such tools are very complex for studying (manuals for Sentaurus Device from Synopsys TCAD F-2011.09 have 1334 pages), occupy a lot of HDD memory and usually operates under OS Linux.
For initial estimation of silicon device parameters and technological process modes it will be useful to have small, simple, fast and user friendly programs such as very popular Process Wizard (Prowize or FAKT) the one dimensional process simulator developed still under MSDOS.
It will be useful to utilize the Microsoft Excel spreadsheets as the basis for 1D-simlutors. Spreadsheet has simple and comfortable tools for 1D-data storing and visualization. For example in [3] were developed two-dimensional program PC2D for solar cells device simulation, completely based on Excel spreadsheets.
In this article we develop several programs for one dimensional silicon process and devices simulation, based on Microsoft Excel spreadsheets. In our programs the main computation core is realized in Visual Basic, embedded in Excel [4]. There are three main programs:
- device simulation of metal-insulator-semiconductor (MIS)structures and transistors MIS1D;
- device simulation of pn-junctions PN1D;
- silicon technology process simulation Process1D.
MIS1D program can build one-dimensional MIS-
structure model with five different materials such as
Si, SiO2, Si3N4 and three other insulators with user defined parameters. Donor and acceptor concentrations can be defined as constant and Gaussian profiles. MIS model is covered by non-uniform finite-difference grid. The grid is automatically refined at region interfaces according to user-defined minimum and maximum step. MIS1D solves numerically the Poisson equation with several models and material parameters (permeability, electron affinity, band gap, intrinsic density). MIS1D is a single Excel file with two spreadsheets – the first for simulation results, and the second – for model parameters. As a result MIS1D computes and visualizes spatial distributions of potential, electric field, carrier concentrations and band diagrams. Also MIS1D computes the inversion charge–voltage- and CV- characteristics at different gate-substrate voltages.
PN1D program can build one-dimensional silicon p-n-models (p+-n, n+-p, p+-p-n, n+-n-p, n+-p-p+, p+-n-n+). with non-uniform doping distribution. The finite-difference grid is refined at p-n-junction depth (Xj) according to user-defined minimum and maximum step. PN1D can compute the surface resistance (ρs) of doping region, what allows restoring the unknown profile by given ρs and Xj. PN1D can solve the single Poisson equation for reverse-biased p-n-junction (with constant quasi-Fermi levels) at linear (1D), cylindrical (2D) and spherical (3D) coordinates and compute the avalanche breakdown voltage and pn-junction CV-characteristics at different voltages. Also PN1D can solve the drift-diffusion system (Poisson and two carrier continuity questions) in linear coordinates and compute IV-characteristics for the forward and reverse biased p-n-junction).
Process1D can model silicon process operations such as ion implantation, oxidation and diffusion for B, P,As impurities and N2,O2,H2O ambients. Ion implantation simulated using Gaussian distributions. Oxidation and diffusion simulated by solving numerically the second Fick law equation for impurities and oxidants.
Keywords
 process and device simulation, TCAD, one dimensional approach, spreadsheets.
Library reference
 Krupkina T.Yu., Krasukov A.Yu., Artamonova Ye.A. One dimensional process and device simulation using spreadsheets // Problems of Perspective Micro- and Nanoelectronic Systems Development - 2016. Proceedings / edited by A. Stempkovsky, Moscow, IPPM RAS, 2016. Part 4. P. 24-31.
URL of paper
 http://www.mes-conference.ru/data/year2016/pdf/D083.pdf

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