LEVEL 62 RPI Poli-Si TFT Model

Star-Hspice LEVEL 62 is an AIM-SPICE MOS16 poly-silicon (Poli-Si) thin-film transistor (TFT) model.

Model Features

The AIM-SPICE MOS16 Poli-Si TFT model features include:

• A design based on the crystalline MOSFET model
• Field effect mobility that becomes a function of gate bias
• Effective mobility that accounts for trap states:
• For low V gs , it is power law
• For high V gs , it is constant
• Reverse bias drain current function of electric field near drain and temperature
• A design independent of channel length
• A unified DC model that includes all four regimes for channel lengths down to 4 m:
• Leakage (thermionic emission)
• Subthreshold (diffusion-like model)
• Above threshold (c-Si-like, with mFet)
• Kink (impact ionization with feedback)
• An AC model that accurately reproduces C gc frequency dispersion
• An automatic scaling of model parameters that accurately model a wide range of device geometries

Using LEVEL 62 with Star-Hspice

When using the AIM-SPICE MOS16 Poli-Si TFT model:

1. Set LEVEL=62 to identify the model as the AIM-SPICE MOS16 Poli-Si TFT model.

2. The default value for L is 100m, and the default value for W is 100m.

3. The LEVEL 62 model is a 3-terminal model. No bulk node exists; therefore no parasitic drain-bulk or source-bulk diodes are appended to the model. A fourth node can be specified, but does not affect simulation results.

4. The default room temperature is 25oC in Star-Hspice, but is 27oC in some other simulators. The user may choose whether or not to set the nominal simulation temperature to 27oC by adding .OPTION TNOM=27 to the netlist.

Example

This is an example of a Star-Hspice model and element statement modified for use with LEVEL 62:

mckt drain gate source nch L=10e-6 W=10e-6

.MODEL nch nmos LEVEL=62

+ asat = 1 at = 3e-8 blk = 0.001 bt = 0.0 cgdo = 0.0

+ cgso = 0.0 dasat = 0.0 dd = 1.4e-7 delta = 4.0

+ dg = 2.0e-7 dmu1 = 0.0 dvt = 0.0 dvto = 0.0 eb = 0.68

+ eta = 7 etac0 = 7 etac00 = 0 i0 = 6.0 i00 = 150

+ lasat = 0lkink = 19e-6 mc = 3.0 mk = 1.3 mmu = 3.0

+ mu0 = 100 mu1 = 0.0022 mus = 1.0 rd = 0.0 rdx = 0.0

+ rs = 0.0 rsx = 0.0 tnom = 27 tox = 1.0e=7 vfb = -0.1

+ vkink = 9.1 von = 0.0 vto = 0.0

LEVEL 62 Model Parameters

Equivalent Circuit

Model Equations

Drain Current

The expression for the subthreshold current is given by:

where is the dielectric constant of the oxide and k B is the Boltzmanns constant.

Above threshold ( Vgt > 0), the conduction current is given by:

Subthreshold leakage current is the result of thermionic field emission of carriers through the grain boundary trap states and is described by:

Finally, for very large drain biases, the kink effect is observed. It is modeled as impact ionization in a narrow region near the drain. The expression can be written as:

The impact ionization current, Ikink , is added to the drain current.

Threshold Voltage

If VTO is not specified:

else:

Temperature Dependence

Capacitance

U