LEVEL 8 IDS Model

The LEVEL 8 model, derived from research at Intersil and General Electric, is an enhanced version of the LEVEL 2 ids equation. LEVEL 2 differs from LEVEL 8 in the following areas: the effective substrate doping, threshold voltage, effective mobility, channel length modulation, and subthreshold current.

LEVEL 8 Model Parameters

This section lists the LEVEL 8 model parameters.

Basic DC Model Parameters

Name (Alias)	Units	Default	Description
LEVEL		1.0	IDS equation selector. Use LEVEL 8 for the advanced model using finite differences.
COX	F/m 2	3.45314e-4	Oxide capacitance per unit gate area. This parameter is calculated from TOX if not specified.
ECRIT (ESAT)	V/cm	0.0	Critical electric field for carrier velocity saturation, from Grove: electrons 6e4 holes 2.4e4 Use zero to indicate an infinite value.
SNVB	1/ (V·cm 3 )	0.0	Slope of doping concentration versus vsb (element parameter). (Multiplied by 1e6)
TOX	m	1e-7	Oxide thickness
VMAX (VMX, VSAT)	m/s	0.0	Maximum drift velocity of carriers. Use zero to indicate an infinite value.

Effective Channel Width and Length Parameters

Name (Alias)	Units	Default	Description
DEL	m	0.0	Channel length reduction on each side. DEL is applicable in most MOSFET models. An exception is the BSIM (LEVEL 13) model, where DEL is not present. DELscaled = DEL `·` SCALM
LD (DLAT, LATD)	m		Lateral diffusion into channel from source and drain diffusion. If LD and XJ are unspecified, LD default=0.0. When LD is unspecified, but XJ is specified, LD default=0.75 `·` XJ. LDscaled = LD `·` SCALM.
LDAC	m		This parameter is the same as LD, but if LDAC is included in the .MODEL statement, it replaces LD in the Leff calculation for AC gate capacitance.
WD	m	0.0	Lateral diffusion into channel from bulk along width WDscaled = WD `·` SCALM
WDAC	m		This parameter is the same as WD, but if WDAC is included in the .MODEL statement, it replaces WD in the Weff calculation for AC gate capacitance.
LMLT		1.0	Length shrink factor
LREF	m	0.0	Channel length reference LREFscaled = LREF `·` SCALM
WMLT		1.0	Diffusion layer and width shrink factor
WREF	m	0.0	Channel width reference WREFscaled = WREF `·` SCALM
XJ	m	0.0	Metallurgical junction depth XJscaled = XJ `·` SCALM
XL (DL, LDEL)	m	0.0	Accounts for masking and etching effects XLscaled = XL · SCALM
XW (WDEL, DW)	m	0.0	Accounts for masking and etching effects XWscaled = XW `·` SCALM

Threshold Voltage Parameters

Name (Alias)	Units	Default	Description
CAV		0.0	Thermal voltage multiplier for the weak inversion equation
DELTA		0.0	Narrow width factor for adjusting threshold
ETA		0.0	Drain-induced barrier lowering (DIBL) effect coefficient for threshold voltage
GAMMA	V 1/2		Body effect factor. This parameter is calculated from NSUB if not specified (see Common Threshold Voltage Parameters).
LND	µ m/V	0.0	ND length sensitivity
LN0	µ m	0.0	N0 length sensitivity
ND	1/V	0.0	Drain subthreshold factor (typical value=1)
N0		0.0	Gate subthreshold factor (typical value=1)
WIC		0.0	Sub-threshold model selector
WND	µ m/ V	0.0	ND width sensitivity
WN0	µ m	0.0	N0 width sensitivity
NFS (DFS, NF, DNF)	cm -2 · V -1	0.0	Fast surface state density
NSUB (DNB, NB)	cm -3	1e15	Bulk surface doping. This parameter is calculated from GAMMA if not specified.
PHI	V	0.576	Surface inversion potential. This parameter is calculated from NSUB if not specified (see Common Threshold Voltage Parameters).
VTO(VT)	V		Zero-bias threshold voltage. This parameter is calculated if not specified (see Common Threshold Voltage Parameters).

Mobility Parameters

Name (Alias)	Units	Default	Description
MOB		6.0	Mobility equation selector (can be set to 2, 3, 6, or 7 in LEVEL 8)
UCRIT	V/cm	1e4	MOB=6, UEXP>0 Critical field for mobility degradation, UEXP operates as a switch. MOB=6, UEXP`<=` 0 Critical field for mobility degradation. Typical value is 0.01 V -1 .
UEXP (F2)		0.0	Critical field exponent in mobility degradation
UTRA	m/V	0.0	Transverse field coefficient (mobility)
UO (UB, UBO)	cm 2 / (V·s)	600 (N) 250 (P)	Low field bulk mobility. This parameter is calculated from KP (BETA) if KP (BETA) is input.

Channel Length Modulation Parameters

Name (Alias)	Units	Default	Description
A1		0.2	Channel length modulation exponent (CLM=8)
CLM		7	Channel length modulation equation selector
LAM1	1/m	0.0	Channel length modulation length correction
LAMBDA (LAM, LA)		0.0	Channel length modulation coefficient

LEVEL 8 Model Equations

This section lists the LEVEL 8 model equations.

IDS Equations

LEVEL 8 ids equations are the same as the LEVEL 2 model. These equations are repeated here for convenience.

Cutoff Region, vgs`<=` vth

(See subthreshold current)

On Region, vgs>vth

where:

Effective Channel Length and Width

The model calculates effective channel length and width from the drawn length and width as follows:

Effective Substrate Doping, nsub

Specify the model parameter SNVB to vary substrate doping concentration linearly as a function of vsb.

The , , and xd parameters are computed using the above equation for nsub.

If SNVB is zero, then = GAMMA. The value is adjusted for short-channel effect the same way as the LEVEL 2 model. Also, is calculated using NSUB.

Threshold Voltage, vth

Specify ETA to include the threshold voltage reduction due to potential barrier lowering effect.

The is modified for short-channel effect, the same as in the LEVEL 2 model, to get effective .

Saturation Voltage vdsat

The saturation voltage vsat is computed the same as in the LEVEL 2 model. The carrier velocity effect is included only when ECRIT is greater than zero.