Automated Model Binning

Introduction

An automated SPICE model binning feature has been implemented in UTMOST III. Binning is used when the user decides to generate a separate model for each device and then combine them into groups by introducing L, W and P (WxL) parameters in a final combined model.

The binning method is widely used for empirical models. Even though BSIM3v3 is a physical model, it also supports binning. It is possible to generate a single BSIM3v3 model which can be used for all geometries. The overall error of a single model may not be as low as binned models. However the single model is compact, easy to maintain and more physical than binned models. Both methods have advantages and disadvantages and users can choose between these two methods.

Binning Feature in UTMOST

A new routine button named "BINNING" is added to the UTMOST setup and extraction screens. The UTMOST binning feature can be used in two ways:

A "global" model (including L, W and P parameters) can be generated from two, three or four single geometry models,

or

A single geometry model (without L, W and P parameters) can be generated from a "global" model.

The L, W and P parameters calculation is based on the following formula:

PARAMeff = PARAM0 + LPARAM * (1/Leff - 1/LReff) + WPARAM * (1/Weff - 1/Wreff) +PPARAM * ( 1/Leff - 1/Lreff) * (1/Weff - 1/Wreff)

Global model generation:

To generate a global model users should obtain four (best case) single geometry models before creating the global model.

For example, to generate a global model for devices: (W/L) 1/1, 1/0.35, 0.5/1 and 0.5/0.35 the user should have a model for each device.

After the single models are ready Press the "BINNING" button in the Setup and Result Screen. This will open the model Binning Setup Screen (Figure 1.).

Figure 1. Model Binning Setup Screen for global model.

 

  • Enter single model file names and W and L values for each model.
  • The constant model file is a text file containing of the parameters which will not be used in L, W and P dependent parameter generation. A typical "constant model file" has the following format:

TOX

LD

WD

CJ

CGDO

.

.

.

 

(Use only one parameter per line in the text file!)

  • Enter the global output model file name.
  • Wref and Lref are selected as the minimum L and W device within the group of four single models. In our example, WREF=0.5um and LREF=0.35um.
  • Open the Extraction screen, select the "BINNING" routine and press the measure button to generate the global output model file.

 

Single geometry model generation:

To generate a single geometry model from a global model:

  • Open the "Binning Setup Screen". Enter the "global" model name in the "Input Model File 1" text field. (Figure 2)
  • Enter the single geometry model file name in the Output Model File text field.
  • Enter the W and L values for the single geometry.
  • Open the Extraction screen. Select the "BINNING" routine. Press the measure button to generate the single geometry model.

Figure 2. Model Binning Setup Screen for single geometry model.