New SOI UTMOST Module

Introduction

Bulk CMOS is currently the dominant technology for VLSI integrated circuits but its scaling constraints pose ever greater as device geometries shrink. Thus, the search for a suitable replacement has begun, and Silicon-On-Insulator (SOI) technology seems to become the most attractive candidate for a suitable VLSI/CMOS technology.

The SOI technology differs significantly from the bulk technology due to the burried oxide. Because of this specific structure, SOI MOSFETs exhibit many anomalous static and dynamic effects which can be attributed to either the floating body or to self heating. Consequently, in addition to the usual Bulk MOSFET, several other characteristics must be observed to characterize correctly and accurately SOI devices. SOI utmost module has been improved accordingly to these criteria, and is presented in this article.

 

SOI Module Specificities

Number of Terminals
SOI devices are commonly designed with 4 terminals : Drain, Gate, Source and BackGate terminals. It can also be designed with a fifth terminal in order to access the internal Body (equivalent to MOS Substrate terminal). Users can switch between 4 and 5 terminals devices through the "# of Terminals" button of the Common Control Screen.

The SMU Definition Screen will be so modified accordingly to the number of terminals selected. For example, in the HP4145 case and for 5 terminal devices, the BackGate terminal will be applied on the VS1 Unit. For the HP4156, the user will be able to choose between SMU5 (if he can use this SMU) or VS1.



Figure 1. SMU Definition Screens for HP4145 and HP4156.



The general syntax to define a SOI device in UTMOST, is:
    MXX ND NG NS NBG (NB) MNAME (L=Lavlue) (W=Wvalue)

where ND is the Drain node, NG is the Gate node, NS is the Source node, NBG is the BackGate node, and NB is the optional Body node. This Body node should be present in case of body contacted devices. MNAME is the model name while L and W are respectively the length and width of the device.

 

Common Routines

ID/VD-VG Routine
This routine comes from the well known ID/VD-VG MOS routine, and has been adapted to the SOI Module allowing users to measure, simulate and optimize Output characteristics. Rubberband and modeling are also available. The drain voltage is swept over a defined voltage range for a set of VG values. BackGate (and Body if accessible) are kept to constant values.

The DC Measurement Screen variables are described below. The number of VG steps is defined in the Measurement Section field now available in both DC Measurement Screen and Routine Control Screen.

VDS_start Starting value of the Drain voltage sweep range.
VDS_stop Stop value of the Drain voltage range.
points Number of sweep data points.
VGS_start Starting value of Gate voltage.
VGS_stop Step value of the Gate voltage.
VBG_or_Body Constant voltage applied to BackGate (if Stepflag=0) or to Body-contact (if Stepflag=1).
V_constant Constant voltage applied to Body-contact (if Stepflag=0) or to BackGate (if Stepflag=1); only used with 5 terminals.
compl_smu(A) SMU current compliances.
wait Wait time in microseconds, between measurements
Stepflag BackGate-Body switch flag.




Figure 2. Typical ID/VD-VG Measured Data Set.
SOI characteristic in continuous line, and SOI
with Body-Contact in dashed line.

 




ID/VG-VB Routine
This routine also comes from the well know ID/VG-VB MOS routine. It is dedicated to the transcharacteristic analysis. Measurement, simulation, optimization, rubberband and modeling are available for this routine. The Gate voltage is swept over a defined range for a set of BackGate (or Body) values. In case of 5 terminals Body (or BackGate) is kept to a constant value. Drain is kept to a constant value too.

The DC Measurement Screen variables are described below. The number of VBG (or VBody) steps is defined in the Measurement Section field now available in both DC Measurement Screen and Routine Control Screen.

VGS_start Starting value of the Gate voltage sweep range.
VGS_stop Stop value of the Gate voltage range.
points Number of sweep data points.
VD Constant Drain voltage.
V_start Starting value for the stepped voltage (Body if Stepflag=1, BackGate if Stepflag=0).
V_step Step value for the stepped voltage Body if Stepflag=1, BackGate if Stepflag=0).
V_constant Constant voltage applied to BackGate (if Stepflag=1)or to Body (if Stepflag=0 voltage ; only used with 5 terminals.
compl_smu(A) SMU current compliances.
wait Wait time in microseconds, between measurements.
Stepflag Body voltage is stepped if 1, else BackGate voltage is stepped; only active with 5 terminals.




Figure 3. Typical SOI ID(VG) characteristic for several
VBackGate (4 terminals) with markers and dashed
lines. Usual ID/VG characteristic for several VBody
(5 terminals, stepflag=1) in continuous lines.




ALL_DC Routine
Identical to the MOS Module, the ALL_DC routine is a multi-geometry and multi-characteristic routine. This routine will allow the user to display both ID/VG-VB and ID/VD-VG curves for several devices on the same plot. This is a powerful routine, which will be strongly recommended for multiple optimizations. This routine is available for measurement, simulation, optimization, rubberband and modeling features.

The DC Measurement Screen variables are described below. The number of VG and VBG (or VBody) steps are defined in the Measurement Section field now available in both DC Measurement Screen and Routine Control Screen.

VD_start_vd Starting value for the Drain voltage sweep (ID/VD curves).
VD_stop_vd Stop value for the Drain voltage range (ID/VD curves).
VG_start_vd Starting value of the Gate voltage step (ID/VD curves).
VG_step_vd Step value for the Gate voltage (ID/VD curves).
V_start_vd Starting value of the BackGate (or Body) voltage second step (ID/VD curves).
V_step_vd Step value for the BackGate (or Body) voltage second step (ID/VD curves).
V_points_vd Number of BackGate (or Body) step points (ID/VD curves).
V_const_vd Constant Body (or BackGate) voltage value ; only used with 5 terminals (ID/VD curves).
VG_start_vg Starting value for the Gate voltage sweep (ID/VG curves).
VG_stop_vg Stop value for the Gate voltage range (ID/VG curves).
VD_vg Constant Drain voltage value (ID/VG curve).
V_start_vg Starting value for the BackGate (or Body) voltage step (ID/VG curves).
V_step_vg Step value for the BackGate (or Body) voltage step (ID/VG curves).
V_const_vg Constant Body (or BackGate) voltage value ; only used with 5 terminals (ID/VG curves).
points Number of sweep data points.
ALL0,VD1,VG2 If 0, both ID/VD and ID/VG curves are measured. If 1, only ID/VD curves are measured.

If 2, only ID/VG curves are measured.
compl_smu(A) SMU current compliances.
wait Wait time in microseconds, between measurements.
Stepflag If 0, V_start,step,.._vd(vg) are applied on BackGate, and V_const_vd(vg) are applied on Body.

If 1, V_start,step,.._vd(vg) are applied on Body, and V_const_vd(vg) are applied on BackGate. Only used with 5 terminals.




Figure 4.Typical ALL_DC plot, with ID/VD and gds
targets for a partially depleted SOI device.




To avoid confusion between BackGate and Body value, variable definitions can be given as in Table 1.


 

Measurement variables 4 terminals 5 terminals
stepflag=0 stepflag=1
V_start_vd, V_step_vd, V_points_vd VBackGate @ID/VD VBackGate @ID/VD VExtBody @ID/VD
V_const_vd Not Used VExtBody @ID/VD VBackGate @ID/VD
V_start_vg, V_stop_vg VBackGate @ID/VD VBackGate @ID/VG VExtBody @ID/VG
V_const_vg Not Used VExtBody @ID/VG VBackGate @ID/VG

Table 1.




BSIM3_MG routine
BSIM3_MG routine derived from the MOS module and has been adapted for the SOI module. As for the MOS module, this routine will manage four characteristics: ID/VD-VG with 0V on BackGate (or Body), ID/VG-VB for low VD, ID/VD-VG for high BackGate (or Body) bias, and ID/VG-VB for high VD. If this routine is used with 5 terminals and stepflag=1, curves will be obtained as for a MOS device. All BSIM3 model parameters, as can be done in the MOS module, will be extracted.

The DC Measurement Screen is described below. The number of VG steps is given through the #_of_vgsteps variable, and the number of VBG (or VBody) steps is given through the #_of_vbsteps variable.

VGS_start_vg Starting value for the Gate voltage sweep (ID/VG curves).
VGS_stop_vg Stop value for the Gate voltage range (ID/VG curves).
VDS_low_vg Low constant Drain voltage for the linear region (ID/VG curves).
VDS_high_vg High constant Drain voltage for the saturation region (ID/VG curves).
VDS_start_vd Starting value for the Drain voltage sweep (ID/VD curves).
VDS_stop_vd Stop value for the Drain voltage range (ID/VD curves).
VGS_strt1_vd Starting value of the Gate voltage step (ID/VD curves with VBG(or VBody)=0V) ; value calculated from extracted threshold voltage and VGS_strt_off.
VGS_strt2_vd Starting value of the Gate voltage step (ID/VD curves with VBG(or VBody)=V_stop_vd) ; value calculated from extracted threshold voltage and VGS_strt_off.
VGS_strt_off Offset voltage used to determine VGS_strt1_vd and VGS_strt2_vd values.
V_stop_vd Maximum BackGate (or Body) voltage (ID/VD curves).
V_const_vd Constant Body (or BackGate) voltage (ID/VD curves) ; only used with 5 terminals.
compl_smu(A) SMU current compliances.
points Number of sweep data points.
V_stop_vg Maximum BackGate (or Body) step voltage (ID/VG curves).
V_const_vg Constant Body (or BackGate) voltage (ID/VG curves).
wait Wait time in microseconds, between measurements.
#_of_vgsteps Number of VG steps (ID/VD curves).
#_of_vbsteps Number of VBG (or VBody) steps (ID/VG curves).
Stepflag If 0, V_stop_vd(vg) are applied on Backgate ; V_const_vd(vg) are applied on Body. If 1, V_stop_vd(vg) are applied on Body ; V_const_vd(vg) are applied on BackGate. Only used with 5 terminals.





Figure 5. Example of BSIM3_MG measurement
for a long and large device. Case 5 terminals,
and Stepflag=1.



To avoid confusion between BackGate and Body value, varaible definitions can be given as in Table 2.

Measurement variables 4 terminals 5 terminals
stepflag=0 stepflag=1
V_stop_vd VBackGate @ID/VD VBackGate @ID/VD VExtBody @ID/VD
V_const_vd Not Used VExtBody @ID/VD VBackGate @ID/VD
V_stop_vg VBackGate @ID/VD VBackGate @ID/VG VExtBody @ID/VG
V_const_vg Not Used VExtBody @ID/VG VBackGate @ID/VG
#_of_vgsteps   VGate Steps @ID/VD  
#_of_vdsteps VBackGate Steps @ID/VG VBackGate Steps @ID/VG VExtBody Steps @ID/VG

Table 2.



The extraction part of this routine is derived from the MOS module, and allows the user to extract the whole MOS BSIM3 model parameters of the BSIM3SOI model.

Currently, this routine is only able to extract low VD model parameters.

 

AL_IDVGD Routine
This last routine also comes from the MOS module. This is a new multi-geometry routine, which allows users to measure the drain current over a defined gate sweep voltage for several drain voltages. A second step can be applied on the BackGate with 4 terminal devices, and on the Body with 5 terminal devices. This routine allows the measurement, simulation, optimization, rubberband and modeling features.

The DC Measurement Screen is described below. The number of VD steps is defined in the Measurement Section field.

VGS_start Starting value of the Gate voltage sweep range.
VGS_stop Stop value of the Gate voltage range.
points Number of sweep data points.
VD_start Starting value of the Drain step voltage.
VD_step Step value of the Drain voltage.
VB_start

Starting Backgate voltage value in case of 4 terminals.

Starting Body voltage value in case of 5 terminals.
VB_step

Step BackGate voltage value in case of 4 terminals.

Step Body voltage value in case of 5 terminals.
VB_points Defines the number of BackGate (or Body) bias points.
VB5_cst BackGate constant voltage ; only used with 5 terminals.
VS Constant Source voltage.
complsdb(A) SMU current compliances.
wait Wait time in microseconds, between measurements.
IDS_low_cut Drain low current limit to filter noisy data points.




Figure 6. Typical ID/VG-VD curves for
partially depleted SOI devices.




IB/VG_MG Routine
This routine stems from the well known ALL_ISUB MOS routine, and is dedicated to characterize the Impact Ionisation current. As for ALL_ISUB, it is a multi-geometry routine. Measurement, simulation, optimization, rubberband and modeling are available. Internal Body current is measured over a defined gate voltage sweep range, for several drain constant steps, and eventually for various second Body values. During all measurements, source and backgate are kept to constant values.

The DC Measurement Screen variables are described below. The number of VD steps is defined in the Measurement Section field.

VGS_start Starting value of the Gate voltage sweep range.
VGS_stop Stop value of the Gate voltage range.
VDS_start Stating value of the Drain step voltage.
VDS_step Step value of the Drain voltage.
V_start Starting value of the Body second step voltage.
V_step Step Body voltage value for the second step.
V_points Number of Body voltage steps.
VBackGate Constant Backgate voltage value.
points Number of sweep data points.
wait Wait time in microseconds, between measurements.
compl_smu(A) SMU current compliances.
VS Constant Source voltage.
compl_vs(A) Current compliance for voltage sources.




Figure 7. Typical Impact Ionisation current
characteristic for several devices and several Body bias.




IB/VB_MG routine
This new routine is dedicated to measure the well known SOI IB(VB) characteristic. This characteristic represents the current flowing through both Drain-Body and Source-Body diodes. The principle of this measurement is to fix source, drain and BackGate voltages, sweep the Body voltage for several gate bias, and measure the Body current. Also, a classical diode characteristic will be obtained. This routine is a multi-geometry routine, in which measurement, simulation, optimization, rubberband and modeling are available.

The DC Measurement Screen variables are described below. The number of VG steps are defined in the Measurement Section field.

VB_start Starting value for the Body voltage sweep range.
VB_stop Stop value for the Body voltage range.
VG_start Starting value for the Gate step voltage.
VG_step Step value for the Gate voltage.
points Number of sweep data points.
VDcst Constant Drain voltage value.
VScst Constant Source voltage value.
VBGcst Constant Backgate voltage value.
compl_smu(A) SMU current compliances.
compl_vs(A) Current compliance for the voltage sources.
wait Wait time in microseconds, between measurements.




Figure 8. Typical IB(VB) characteristic,
for two devices.




IC/VCE Routine
This new routine is dedicated for parasitc Drain-Body-Source Bipolar device characterization. The aim of this routine is to measure the output characteristic of this parasitic bipolar, such as IC(VCE) characteristic for a real Bipolar device. To adapt this for the parasitic bipolar of the SOI device, the drain current for a defined drain sweep voltage should be measured, for several Body bias. We can consider the drain as the collector, the source as the emitter, and the body as the base of an equivalent real bipolar device. This routine is a multi-geometry routine, for which measurement, simulation, optimization, rubberband and modeling features are available.

The DC Measurement Screen variables are described below. The number of VB steps is defined in the Measurement Section field.

VD_start Starting value for the Drain voltage sweep range.
VD_stop Stop value for the Drain voltage range.
VB_start Starting value of the step Body voltage.
VB_step Step voltage value for the Body steps.
points Number of sweep data points.
VGcst Constant Gate voltage value.
VScst Constant Source voltage value.
VBGcst Constant BackGate voltage value.
compl_smu(A) SMU current compliances.
compl_vs(A) Current compliance for voltage sources.
wait Wait time in microseconds, between measurements.




Figure 9. Typical SOI Parasitic Bipolar Output
characteristics, for two devices.




DIODE Routine
This routine is again a completely new routine. Its origin comes from the IB/VB_MG routine, in which we measured the current flowing through both Drain-Body and Source-Body diodes. The objective of this Diode routine is to isolate the current of one diode, short-cutting the second one. We can measure the Drain-Body (respectivelly Source-Body) diode current for a defined Body voltage swep range. The principle simple. The same voltage on both Body and Source (respectivelly Drain) terminals; needs to be applied so that the Source-Body (respectivelly Drain-Body) diode will not be biased, preventing current from going through this diode. For measurement, the principle is to use the VAR1' functionnality of the HP4145 and HP4156 instruments. During all measurements, BackGate and Drain (respectivelly Source) are kept to constant values. This measurement can be repeated for several gate voltages, in order to eventually includes the effect of gate biasing on this characterisic. In terms of simulation, the nodes for Body and Source (respectivelly Drain) should be the same. This routine is again a multi-geometry routine, with measurement, simulation, optimization, rubberband and modelling features available.

The DC Measurement Screen variables are described below. The number of VG steps is defined in the Measurement Section field.

wait Wait time in microseconds, between measurements.
VB_start Starting value for the Body voltage sweep range.
VB_stop Stop value for the Body voltage range.
VG_start Starting value of the step Gate voltage.
VG_step Step value for the Gate voltage.
points Number of sweep data points.
VDcst Constant Drain voltage ; only used if VAR1'? D=0S=1 is set to 1.
VScst Constant Source voltage ; only used if VAR1'?D=0S=1 is set to 0.
VBGcst Constant BackGate voltage.
compl_smu(A) SMU current compliances.
compl_vs(A) Current compliance for voltage sources.
VAR1' D=0S=1 If 0, VAR1', is applied on Drain, and Source-Body diode current is measured. If 1, VAR1', is applied on Source, and Drain-Body diode current is measured.




Figure 10. Typical Drain-Body and Source-Body diode current characteristics.



Gummel Routine
This is a new routine dedicated, as is the IC/VCE routine, to the parasitic bipolar characterization. In order to characterize completely this bipolar, in addition to the output characteristic, the Gummel characteristic should be analyzed. For a classical bipolar device, this characteristic is composed of the Base and Collector curves versus a Base voltage sweep. For this SOI module, the equivalent is to measure the Body (for Base) and Drain (for Collector) currents for a defined Body (for Base) sweep voltage range. During all measurements, Drain, Source, Gate and BackGate are kept to constant values. As all other routines, this is a multi-geometry routine, in which measurement, simulation, optimization, rubberband and modeling features are active. The DC Measurement Screen is described below.

VB_start Starting value for the Body voltage sweep range.
VB_start Starting value for the Body voltage sweep range.
VB_stop Stop value for the Body voltage range.
VDcst Constant Drain voltage value.
VScst Constant Source voltage value.
VBGcst Constant BackGate voltage value.
points Number of sweep data points.
compl_smu(A) SMU current compliances.
compl_vs(A) Current compliance for voltage sources.
wait Wait time in microseconds, between measurements.



Conclusion

This new SOI module is now available in Utmost III, and in addition to the various SOI models of SmartSpice, will allow our users to extract a full scalable DC SOI model. The main characteristics are now available in UTMOST, all available in measurement, simulation and optimization, to allow maximum flexibility for users. Rubberband, Modeling and Log Files features are also available.

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