Specifying Junction Diode Models

Use the diode element statement to specify the two types of junction diodes, geometric and nongeometric. Use a different element type format for the Fowler-Nordheim model.

The diode element statement parameter fields define the connecting nodes, initialization, temperature, geometric junction, and capacitance parameters of the diode model selected in the diode .MODEL statement. Both LEVEL 1 and LEVEL 3 junction diode models share the same element parameter set. Poly and metal capacitor parameters of LM, LP, WM and WP do not share the same element parameter.

Element parameters take precedence over model parameters, if repeated in the .MODEL statement as model parameters.

Parameters common to both element and model statements are:

AREA, PJ, M, LM, LP, WM, WP, W, and L.

Using the Junction Model Statement

This section describes how to use the junction model statement.

Syntax

The syntax of the junction model statement is:

.MODEL mnameD <LEVEL = val> <keyword = val> ...

Example

.MODEL D D (CO=2PF, RS=1, IS=1P)

.MODEL DFOWLER D (LEVEL=2, TOX=100, JF=1E-10, EF=1E8) 

.MODEL DGEO D (LEVEL=3, JS=1E-4, JSW=1E-8) 

.MODEL d1n750a  D

+ LEVEL=1				XP  =0.0			EG  =1.1

+ XOI  =0.0				XOM =0.0			XM  =0.0

+ WP   =0.0				WM  =0.0			LP  =0.0

+ LM   =0.0				AF  =1.0			JSW =0.0

+ PB   =0.65				PHP =0.8			M   =0.2994

+ FC   =0.95				FCS =0.4			MJSW=0.5

+ TT   =2.446e-9				BV  =4.65			RS  =19

+ IS   =1.485e-11				CJO =1.09e-9			CJP =0.0

+ PJ   =0.0				N   =1.615			IK  =0.0

+ IKR  =1.100e-2				IBV =2.00e-2

Using Junction Model Parameters

The .MODEL statement is referenced by the diode element statement. The .MODEL statement contains parameters that specify the type of diode model used (LEVEL 1, 2, or 3), as well as DC, capacitance, temperature, resistance, geometric, and noise parameters.

Setting Junction DC Parameters in LEVEL 1 and 3

Setting Junction Capacitance Parameters

Setting Metal and Poly Capacitor Parameters for LEVEL=3

Setting Noise Parameters for LEVEL=1 and 3

Providing Geometric Scaling for Diode Models

LEVEL=1 Scaling

Scaling for LEVEL 1 involves the use of the AREA and M Element parameters. The element and model parameters scaled with AREA and M include:

IK, IKR, JS, CJO, and RS. For AREA and M, default=1

This element is not a geometric model because both the area (AREA) and periphery (PJ) are measured in dimensionless values. These parameters are not affected by the SCALE and SCALM options.

The periphery junction parameter is multiplied by M, the multiplier parameter, to scale the dimensionless periphery junction.

PJeff = PJ · M

PJeff is then used to scale CJP, the zero-bias junction capacitance, and the sidewall saturation current, JSW.

CJPeff = PJeff · CJP

JSWeff = PJeff · JSW

AREA and M are used to obtain AREAeff.

AREAeff = AREA · M

CJO, IK, IKR, IBV, and IS are multiplied by AREAeff to obtain their effective scaled values. RS, however, is divided by AREAeff.

IKeff = AREAeff · IK

IKReff = AREAeff · IKR

IBVeff = AREAeff · IBV

ISeff = AREAeff · IS

RSeff = RS/AREAeff

CJOeff = CJO · AREAeff

LEVEL=3 Scaling

LEVEL 3 scaling is affected by SCALM, SCALE, SHRINK, and M.

The LEVEL 3 element parameters affected by SCALE include:

AREA, LM, LP, PJ, WM, WP, W, L

The model parameters affected by SCALM include:

AREA, IBV, IK, IKR, IS, PJ, JSW, RS, CJO, CJP, LM, LP, WP, XM, XP, W, L, XW

If you include the AREA as either an element parameter or a model parameter, the program uses SCALE or SCALM. The following equations use the AREA element parameter, instead of the AREA model parameter.

If the AREA and PJ model parameters are specified and the element is not, use SCALM as the scaling factor instead of SCALE. The scaled effective area and periphery junction element parameters are determined by:

AREAeff = AREA · M · SCALE 2 · SHRINK 2
PJeff = PJ · SCALE · M · SHRINK

or, if W and L are specified:

AREAeff = Weff · Leff · M
PJeff = (2 · Weff + 2 · Leff) · M

where

Weff = W · SCALE · SHRINK + XWeff
Leff = L · SCALE · SHRINK + XWeff

To find the value of JSWeff and CJPeff use the formula:

JSWeff = PJeff · (JSW/SCALM)
CJPeff = PJeff · (CJP/SCALM)

To determine the polysilicon and metal capacitor dimensions, multiply each by SCALE or by SCALM if specified as model parameters.

LMeff = LM · SCALE · SHRINK
WMeff = WM · SCALE · SHRINK
LPeff = LP · SCALE · SHRINK
WPeff = WP · SCALE · SHRINK
XPeff = XP · SCALM
XMeff = XM · SCALM

You can determine the effective scaled model parameters, IBeff, IKeff, IKReff, IBVeff, RSeff, and CJO as follows:

IKeff = AREAeff · IK
IKReff = AREAeff · IKR
IBVeff = (AREAeff · IBV)/SCALM 2
ISeff = IS · (AREAeff/SCALM 2 )
RSeff = RS/(AREAeff · SCALM 2 )
CJOeff = AREAeff · (CJO/SCALM 2 )

Defining Diode Models

Diode Current

Diode Current Convention shows the direction of current flow through the diode. Use either I(D1) or I1(D1) syntax to print the diode current.

If the voltage on node1 is 0.6V greater than the voltage on node2, the diode is forward biased or turned on. The anode is the p-doped side of a diode, and the cathode is the n-doped side.

Figure 15-1: Diode Current Convention

Using Diode Equivalent Circuits

Star-Hspice uses three equivalent circuits in diode analysis: transient, AC, and noise circuits. Components of these circuits form the basis for all element and model equations.

The fundamental component in the DC equivalent circuit is the DC diode current (id). For noise and AC analyses, the actual id current is not used. The partial derivative of id with respect to the terminal voltage vd is used instead. The name for this partial derivative is:

Conductance

The drain current (id) equation accounts for all basic DC effects of the diodes. Star-Hspice assumes capacitance effects to be separate from the id equations.

Figure 15-2: Equivalent Circuit, Diode Transient Analysis

Figure 15-3: Equivalent Circuit, Diode AC Analysis

Figure 15-4: Equivalent Circuit, Diode AC Noise Analysis

Determining Temperature Effects on Junction Diodes

LEVEL 1 and LEVEL 3 model statements contain parameters for the calculation of temperature effects. TLEV and TLEVC select different temperature equations for the calculation of temperature effects on energy gap, leakage current, breakdown voltage, contact potential, junction capacitance, and grading.

Setting Temperature Effect Parameters LEVEL=1 and 3