Temperature Dependence

Please use the model bsim3_tutor_temp.mdl provided with the BSIM3v3 Modeling Package to visualize the temperature model parameters. Load the file into IC-CAP and run the different macros to see how certain parameters affect the device behavior of a deep submicron MOS transistor.

Built-in Temperature Dependencies

The BSIM3v3 model uses some physically based built-in temperature dependencies as listed below:

Temperature voltage:

(114)

Intrinsic carrier concentration:

(115)

Unfortunately, the surface potential S, which is a very important model parameter from a physical point of view is not temperature dependent in BSIM3.

(116)

Temperature Effects

In addition to the built-in temperature dependencies, the following temperature related effects are modeled in BSIM3. They are related to threshold voltage, mobility, saturation of carrier velocity, drain-source resistance, and the saturation current of the drain/source bulk diodes.

a) Threshold Voltage

(117)

The behavior of the threshold voltage for a large and a short device is shown in tThe following figure.

Figure 125 Threshold Voltage V_th=f(T) of a Large Device

Figure 126 Threshold Voltage V_th=f(T) of a Short Device

b) Carrier Mobility

All four model parameters of the carrier mobility are implemented in BSIM3 with a temperature dependence:

(118)

(119)

(120)

(121)

The following two diagrams show the effect of temperature dependent mobility on the transconductance of a large transistor.

Figure 127 Temperature Dependence of Carrier Mobility U0: Influence on Drain Current

Figure 128 Temperature Dependence of Carrier Mobility U0: Dependence from UTE

c) Saturation of Carrier Velocity

The carrier velocity VSAT is reduced with increasing temperature as shown in the following equation and Figure 130:

(122)

Figure 129 Output Characteristic I_d=f(V_d,T)

Figure 130 Output Characteristic V_SAT = f(T)

d) Drain source resistance

The temperature dependence of the drain source resistance is given by the following equation (see Figure 131):

(123)

Figure 131 Drain source resistance R_DSW = f(T)

e) Saturation Current of Drain/Source Bulk Diodes

The temperature dependence of the drain/source bulk diodes is given by the following equation for the saturation current density J_S:

(124)

The influence of XTI on diode current and saturation current density J_S is shown below.

Figure 132 Saturation Current as Function of Temperature