Largebias conduction model of polycrystalline silicon films
Abstract
There exists a need for a largebias conduction model of polysilicon films used in VLSI/ULSI and in high power integrated circuits. A largebias conduction model has been developed by extending the emissionbased models of Lu et al. and Mandurah et al. valid for smallbias, smallsignal conditions. The following largebias effects have been taken into account: 1) asymmetry of potential distribution around grain boundaries and 2) avalanche multiplication of carriers in the grain boundary layers at high electric fields. Since the exact nature of the grain boundary material is not yet known, and there is no direct method for determining the model parameters relating to grain boundaries, these were extracted by the parametric fitting of resistance versus temperature data of polysilicon resistors near room temperature with the above smallsignal resistivity models modified by including FermiDirac distribution. The model has been validated with experimental data on the currentvoltage characteristics of ionbeam sputtered polysilicon resistors of different sizes and aspect ratios. The dependence of model parameters relating to grain boundary scattering and avalanche multiplication on the dimensions of resistors have been explained physically. The increased kink effect in polysilicon TFT's may also be predicted from the present theory. Some results on the IV characteristics of polyresistors trimmed by high current pulses have been discussed qualitatively in the light of the present model. Although the model involves numerical integrations and a few iterations, it is reasonably fast in execution.
 Publication:

IEEE Transactions on Electron Devices
 Pub Date:
 April 1994
 DOI:
 10.1109/16.278505
 Bibcode:
 1994ITED...41..524D
 Keywords:

 Electrical Resistivity;
 Mathematical Models;
 Polycrystals;
 Printed Resistors;
 Semiconducting Films;
 Silicon Films;
 Silicon Polymers;
 Thin Films;
 Very Large Scale Integration;
 Electron Avalanche;
 Grain Boundaries;
 High Current;
 Iterative Solution;
 Numerical Integration;
 VoltAmpere Characteristics;
 Electronics and Electrical Engineering