Amorphous IGZO TFT Pixel MixedMode Simulation

tftex14.in : Amorphous IGZO TFT Pixel MixedMode Simulation

Requires: Athena/Blaze/TFT/MixedMode
Minimum Versions: Athena 5.22.3.R / Atlas 5.28.1.R

The purpose of example explains how to make an equivalent TFT pixel circuit in Atlas/Mixedmode simulation softwares. This aims at demonstrating how to set up TFT pixel equivalent circuit including passive element such as resistance and capacitance arising from pixel and liquid crystal. The actual pixel size is very large in scale and practically device simulation takes long time to simulate pixel behavior and charging/discharging characteristics of liquid crystal. MixedMode circuit simulation performs both device level simulation and circuit level simulation, in which IGZO TFT test active structure is for device level and TFT pixel(Cst), liquild crystal(Clc) is for circuit level. As a result, users could trace pixel electrode's voltage during TFT on/off periods and additionally estimates pixel voltage shift by active device characteristics such as a-IGZO traps, backlight, and other facts.


This example performs MixedMode pixel simulations of IGZO TFT device with material properties corresponding to amorphous IGZO (indium galium zinc oxide) material. For pixel simulation, we refer to articles on SILVACO website(http://www.silvaco.com/content/kbase/tftlcd_sol.pdf or http://www.silvaco.com/tech_lib_TCAD/simulationstandard/2008/apr_may_jun/a2/a2.html).
MixedMode syntax description Mixedmode circuit description starts with .BEGIN statement and ends with .END statement. Some passiive elements(Cst and Clc) are connected to Atlas TFT structure in ATFT element. Here, Cst is storage capacitance and Clc is liquid crystal capacitance. Both are connected to active IGZO TFT device. Gate, Drain, and Vcom pulse are applied to circuit using "Vname" statement. For liquid crytal capacitance model, we used simple constant capacitance value. Regarding real LC capacitance model, we can use user-defined two terminal element which is defined in C-interpreter function(tftex14_0.c) and uncomment "bLC" statement.

The example shows:

  • Structure formation using Athena syntax
  • Structure loading into Atlas and regioin modification to have a region name "GI" and "channel"
  • MixedMode Active IGZO device and circuit element description
  • Pixel transient simulation
  • Plotting transient response of pixel

The key command in a-IGZO:TFT Mixedmode pixel simulation is the active device element which is defined in "Aname" statement between .BEGIN and .END. "atft" device's each electrodes name(gate,source,drain) is connected to passive element and time dependent voltage source via node number. For two termianl user-defined device( here, bLC), please refer to tftex14_0.c c-function file and detail descriptions on www.silvaco.com link.
.numeric controls various mixedmode convergence and iteration during solution. .options fulln sets the numerical method in mixedmode. Default is full newton method
go atlas activates Mixedmode simulation.
After completion of transient simulation, it plots charging and discharging behavior of LC in Tonyplot.
To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.