DC and CV Measurement of MOSFET's for the MOS Models

This section provides information to make the necessary measurements of your devices. It will provide information on features of the MOS Modeling Packages and how to use the graphic user interface (GUI). For hints on how to measure and what to measure using the right devices, see Chapter 3, "PSP Characterization, Chapter 4, "BSIM4 Characterization", and Chapter 5, "BSIM3v3 Characterization".

The GUI is opened by double clicking the BSIM3, BSIM4, or PSP Icon which appears in the IC-CAP/Main window after you open one of the example files. To open an example file, click File > Examples > model_files > mosfet > bsim3 (or bsim4 or PSP) then select a Measure or Extract model file. Figure 1 shows four of the files in one IC-CAP/Main window, using BSIM3 as an example.

Figure 1 Starting the BSIM3 GUI from IC-CAP/Main window

After you have double clicked the icon, the GUI window of the MOS Modeling Packages (Figure 2) appears on your screen.

Figure 2 Part of the Graphic User Interface for the MOS Modeling Packages

The top row of the GUI shows the File, Configuration, Data, Tools, and Help menus. Some menu topics are only activated when using specific tasks (depending on which folder is activated!). For example, if you are setting up the conditions for a Temperature measurement, the Configuration menu only allows you to add or delete temperatures. The rest of the menu is not active since it is not necessary to set or sort categories during temperature setup, for example.

The File menu has entries to Import and Export list and measurement data from measurement software other than IC-CAP. Those functions are described in Import Wizard.

The standard IC-CAP icons (from left to right) are located below the menu. Use these icons to create a New, to Open an existing, to Copy and Open an Example, to Save Setups or Entries, to Measure, to Display and Close plots, to Add or Delete, to define Temperature Measurements, to Set categories, or to Check SMU connections. You will be prompted before the selected action takes place. Again, some of the icons are only activated when specific folders are active.

The lower part of the window displays the project name and project directory.

To Print a setup, choose File > Print Setup. This opens a dialog box. In this dialog box, enter the command line for your specific printing device and choose OK. The folder will be printed.

From the Help menu you can choose between browsing the Topics or getting help for each of the different task folders described below. There are in depth hints for the task, for example, which device geometries to use or how to connect the instrument to the device under test to get the best extraction results from your measurements. You will find links that bring you to Chapter 3, "PSP Characterization", Chapter 4, "BSIM4 Characterization", or Chapter 5, "BSIM3v3 Characterization". Use your Browsers Back button to return to the location you were at before following the link.

Below the top row of icons are five folders. Basically, each folder is assigned to a specific task in the measurement process. They are intended to be parsed from left to right, but you are not bound to that order. Some entries into one or the other folder will change settings on another folder.

For the new user: You should process the folders in the order from left to right.

Each of the following sections describe one folder of the GUI. BSIM3, BSIM4, and PSP model folders are usually equal to each other.

Project Notes

The notes folder is provided to store notes you take on a specific project. You can enter general data like technology used to produce this wafer as well as lot, wafer, and chip number. There is a field to enter the operator's name and the date the measurement was taken. Space has been provided to enter notes on that project.

Notes entered into the measurement module will be transferred to the Information folder inside the DC_CV_Extraction modules.

Temperature Setup

Use this folder to define measurements at specified temperatures. Basically, the measurement of all DUTs is performed at SPICE default temperature TNOM, which is set to 27° Celsius.

Add new measurement temperatures using the Add icon or the Configuration menu. If you no longer need a measurement temperature, click the Delete button. You will be prompted for the temperature to be deleted. If there is a file containing measured data for this temperature, the data file will be deleted if you choose OK on the prompt dialog.

The delete window does not contain an entry for the temperature set as TNOM, since TNOM cannot be excluded from measurement and extraction.

When you add a new measurement temperature, a new column is added to the Device List folder's Device List table for DC Transistor, Capacitance, and DC Diode.

Any changes on the Temperature Setup folder must be saved prior to selecting another folder.

Switch Matrix

Use this folder to define which measurements use a switch matrix (see Figure 3). There are three options: Use a switch matrix for DC Transistor Measurements, for Capacitance Measurements, and for Diode Measurements. You can select any one or more than one by checking the appropriate boxes.

Figure 3 Defining the use of a switch matrix for measurements

The Basic Settings provide a choice of several different Matrix Models, which are supported by IC-CAP. Type the appropriate Bus and GPIB address of the Switch Matrix (SWM Address; 22 in our example) as well as the GPIB-Interface name. See the IC-CAP Reference manual for a complete description of the GPIB settings for the selected switch matrix. Our example shows the use of an Agilent E5250A matrix model. For this type of instrument, you have to define which port is connected to which SMU or C meter input pin and which slot is equipped with a card.

Again, you have to save your changes prior to leaving this folder.

The actual pin connections are entered into the DUT Variables folder for the measurement selected to use a switch matrix (one or more of the DC Transistor, Capacitance, or Diode Measurements). For example, if you've selected DC Transistor Measurements to use with a switch matrix, you must open the model file for editing and in the DUT/Setups folder select the DC Transistor then in the DUT Variables folder enter the switch matrix pin numbers in the fields below the node names. This is especially useful if you would like to make series measurements on wafers using a probe card (e.g., for quality control).

For automatic measurements, macros are available. These macros enable you to make automatic series measurements of complete dies or arrays. They are created for automatic measurements with or without heated chucks.

For example, open the IC-CAP model for BSIM3_DC_CV_Measure (from the IC-CAP/Main window, right click the DC_CV_Measure model then select Edit). The Macros folder contains a macro called Example_Wafer_ Prober.

You will also find a macro in the $ICCAP_ROOT/examples/model_files/mosfet/BSIM3/ examples/waferprober directory named prober_control.mdl. Please use this macro or model file and tailor it to your needs. There are readme sections to explain the steps to be taken inside the macros.

The automatic measurement of model diagrams using the macro works without involving the GUI.

For your convenience, the waferscan macro in the prober_control.mdl example model file can be loaded into IC-CAP and can be run in a demo mode without taking actual measurements.

Device List

The next step in the modeling process is setting up measurement conditions for different measurement tasks like DC, Capacitance, or Diode measurements and to enter the devices to be used.

This folder is designed for easy setup of conditions for DC Transistor and Capacitance as well as DC Diode measurements. Figure 4 shows the folder used for setting up measurement conditions as well as the devices to be measured. Use the Icons or the menu to save this folder prior to proceeding to the next task.

Figure 4 Device List Folder

The left side of this folder shows a tree view of the data for this measurement project. This tree definition may be different for different models. The previous figure shows the tree used for extracting SOI device parameters.

The folder shows entries not normally present on BISM3/4 or PSP measurement projects. For example, there are no floating transistors to be measured in BSIM3 or 4 modeling tasks.

To expand the Transistor, Diode, and Capacitance entries, click the + sign to reveal a Measurement and Device List.

By clicking on Measurement, the right side of the folder shows predefined measurement sets as well as setups already selected for the specific measurement. To add a setup, click the icon.

You will be prompted to select a setup and enter a name for it. The new setup will be included in the tree below Measurement.

If you select one of the measurement setups inside the tree, the folder changes to reflect the measurement conditions valid for the selected setup.

Figure 5 Measurement Conditions for the idvg-setup

On that form, you can enter the polarity of the devices to be measured and define the conditions for DC measurements as well as to specify current limits for the SMUs (compliance settings).

Polarity

There are polarity buttons to specify whether you are measuring NMOS or PMOS devices. Select NMOS or PMOS. Our example shows the measurement of NMOS devices.

Compliance

DC Compliance settings for the source measurement units (SMUs) are located at the bottom row of the form. You can set different compliance values for each SMU.

DC

The Measurement Data tree uses setups to define different measurement configurations. For compatibility reasons with former versions of IC-CAP, there are two basic setups provided: One called idvg for measuring the drain current dependency from the gate voltage of the device (e.g., transconductance of the device). The other one called idvd for measuring the drain current dependency from the drain voltage, the so called output characteristics of the device.

This part of the measurement conditions is designed for transfer diagram measurements. Again, there is a choice between a Linear sweep and a List of discrete voltage values, where you can enter a number of points and their respective value. For Linear sweep mode, you specify Start, Step, and Stop voltages for gate, bulk, and drain nodes. Stop value of drain voltage is set to a fixed value in order to measure the relevant range of voltages for proper extraction of the parameters used to model this device behavior.

If you set a Constant value for one of the sources, internally a list with just one entry is being used.

Figure 6 shows the typical form of a transconductance diagram.

Figure 6 Transconductance diagram

If you change the settings of the diagram in the figure above, one of the effects appearing in submicron semiconductor devices becomes visible. The following figure shows a typical transconductance diagram using a logarithmic y-axis to show the influence of the GIDL (gate induced drain leakage) effect on transistor behavior.

Figure 7 Transconductance diagram showing GIDL effect

Here you specify the stimulus voltages used for measuring the output characteristic of your devices. You can choose either a Linear sweep or a List of discrete voltage values where you enter a number of points and their respective value. For Linear sweep mode, you define Start, Step, and Stop voltages for drain, gate, and bulk nodes, respectively. Figure 8 shows the typical measured output characteristic of a MOSFET.

Figure 8 Output diagram of a MOSFET

The setups previously described cover the required standard measurement procedure and represent the minimal configuration necessary. The purpose of sweep type LIN(Vt) is to reduce measurement time by excluding areas of the output diagram that are not relevant for extraction. The following figures should help clarify this case.

Figure 9 Output characteristic of the same device measured at different values of bulk voltage: left: vb = 0, right: vb = -1.2V

The gate voltage vg in the diagrams shown above has a fixed sweep from 0.6 to 1.8V. Because the bulk voltage changed, the threshold voltage changes, which in turn changes the output characteristic too. The curves marked with a red arrow are measurements at low current levels and therefore need a considerable amount of time due to the integration of noisy currents. Therefore, the lowest gate voltage consumes a lot of time with minimal benefit for the extraction. For example, it would be better to start the left hand diagram at vg = 0.7V and the right hand diagram at vg = 0.8V. This can be achieved by making the gate voltage sweep starting points dependent on Vth of this device.

The LIN f(Vth)-sweep is a linear sweep using a starting value dependent on an extracted threshold voltage value from another Vg-type sweep.

This sweep needs a reference to another sweep of type vg. The stop condition is fixed and the start point is depending on the threshold voltage of the reference sweep. If this sweep is selected, the setup must not have any other sweeps (e.g., vb, vs, ...) because the IC-CAP rectangular data format does not support it. The referenced sweep must include the vb, vs, (ve) value of the actual sweep, which is defined to be a constant value. In the case of vd (1st sweep), the threshold voltages in the reference sweep at all vd values are taken and a mean value is generated.

Furthermore, it is necessary to specify a resolution value in order to send reasonable voltage values to a measuring instrument. Taking this into account, the effective start and step values are calculated according to the following formulas:

The following table shows the minimum source configuration. It is now possible to select an output from each source, for example, ig, ib, id, is. The source's output current is in bold letters to indicate that it was used as the minimum required output.

Table 2 Minimum measurement setups

Name	Sweep order	Mode voltage to be swept	Fixed settings	Default settings	Options
idvg	1	vg	LIN
	2	vb		LIN	LIST CON
	3	vd		LIN	LIST CON
	4	vs		CON	LIN LIST
idvd	1	vd	LIN
	2	vg		LIN	LIST CON LIN f(Vth)
	3	vb		LIN	LIST CON
	4	vs		CON	LIN LIST

When selecting LIN f(Vth), restrictions apply to the sweep options that are underlined in the table above.

To configure a LIN f(Vth)-sweep, select the idvd-setup and choose LINf(Vth) from the Vg pull-down list of sweep types. See the following figure.

Figure 10 Part of the Device List folder with sweep type Lin f(Vth) selected

Choose an appropriate vg type setup (idvg in our example), and set Idref, offset, resolution (res), stop value, and the number of points (No.Pts.). The vg start voltage value will be calculated using this settings.

If you would like to add measurement setups, choose Configuration > Add from the menu or use the appropriate icon from the top row of icons. A window opens for you to select one of the standard setups and to enter a name for the copy of this setup. By clicking Add, the new setup will appear inside the list of setups. It will use the same settings as defined in the standard setup from which it was created. Adjust all the settings for this new setup according to your needs.

A newly created setup must be configured into a measurement set, which in turn can be used to measure the devices.

Click Configuration > Configure Measurement Setup, or use the configure icon, to open a window for creating a new measurement set or to add a newly created setup to the standard measurement sets. Just click the desired setups to be added or use the Add button to create a new set. Thus, you are able to define measurement sets measuring data from different setups.

Transistor Device List

Select Device List from the tree to enter the devices to be measured. When creating a new project, the device list contains predefined device names that you can simply overwrite with device names of your choice.

The device list table contains additional columns for each temperature you've entered on the Temperature Setup folder.

Figure 11 Device List tree with entries for the devices to be measured

The column named Measure shows the allocation of measurement sets to the devices. For each device, you have to select a measurement set to be used for this device. Using the Device List, you can define which set will be used for which device. Select Configuration > Configure Measurement Set to display a list of devices to be measured. Select a device, then select one of the available measurement sets you wish to assign to this device and click OK.

The Device List under the Transistor branch in the tree view is used to enter DUT names, geometries, and connections to the appropriate DUTs. Since there are differences between the BSIM3 and BSIM4/PSP models, some parameters are to be used only inside the appropriate model and only activated there. The BSIM4/PSP models enables stress effect modeling, which is not possible in BSIM3. Therefore, all stress effect parameters are only used inside the BSIM4/PSP Modeling Packages and are activated only there.

The Configuration menu enables you to set BSIM4/PSP-specific values. You can use different area and perimeter values as well as Number of Squares for the Drain and Source regions of the transistors to be measured (AS, AD, PS, PD, NRD, NRS). Further on you can set stress effect parameters SA, SB, SD. See Stress Effect Modeling for details.

If you deactivate one of the Configuration menu points (AS=AD, PS=PD, for example), additional columns appear in the Device List table.

Now you can enter STI-related parameters. Refer to Figure 15 for details on these parameters.

Well Proximity Effect

Taken from: P. G. Drennan, M. L. Kniffin, D. R. Locascio "Implications of Proximity Effects for Analog Design"; to be found at http://www.ieee-cicc.org/06-8-6.pdf

Highly scaled bulk CMOS technologies make use of high energy implants to form the deep retrograde well profiles needed for latch-up protection and suppression of lateral punch-through. During the implant process, atoms can scatter laterally from the edge of the photoresist mask and become embedded in the silicon surface in the vicinity of the well edge, as illustrated in Figure 12. The result is a well surface concentration that changes with lateral distance from the mask edge, over the range of 1um or more. This lateral non-uniformity in well doping causes the MOSFET threshold voltages and other electrical characteristics to vary with the distance of the transistor to the edge of the well. This phenomenon is commonly known as the well proximity effect (WPE).

Figure 12 Well Proximity Effect: a) caused by ion scattering during well implantation; b) Orientation of devices inside the well

The Well Proximity model considers the influence of the effect on threshold voltage, mobility as well as body effects.

The Configuration menu contains a selection to activate the well proximity effect, or WPE. Activating the well proximity effect inserts additional rows for WPE parameters SCA, SCB, SCC, and SC into the device list. It is possible to enter SC only after selecting the respective menu item from the Configuration menu. If this option is chosen, parameters SCA, SCB, and SCC are calculated from SC-they cannot be modified once this option is set. They will be updated as soon as you enter an SC value and select save.

SC is defined as "The distance to a single well edge used in calculations of SCA, SCB and SCC when layout information is not available". If SCA, SCB, and SCC are not given due to lack of detailed layout information, their estimation can be made by simulators based on the assumption that for most layouts, the devices are close to only one well edge.

For details, see the BSIM4 manual from the University of Berkeley. Their website contains a link where you can download the complete manual. The address is http://www-device.eecs.berkeley.edu/~bsim3/bsim4_get.html

Defining Devices

For your convenience, there are predefined DUTs on the Device List folder when creating a new project. You can either use those predefined DUTs, only adjusting names, device geometries, connections and so on, or you can delete existing DUTs and add your own.

For each line, enter a name for the DUT, gate length and width (L, W), drain and source areas (AD, AS), perimeter length of drain and source (PD, PS), and the number of device fingers (NF) of the transistor to be measured. If modeling stress effects in BSIM4 or PSP, enter SA, SB, and SD as well. See Figure 13 as well as Figure 14 for details on device geometry, respective Figure 15 for details on STI modeling parameters. Well Proximity modeling requires the entry of parameters SCA, SCB, SCC, and/or SC.

Geometries

Shown in the following two figures are views of MOSFET's, where you can find the geometries required by the BSIM3 and BSIM4/PSP Modeling Packages.

Figure 13 .Cross section of a MOSFET showing device geometries

You are not bound to an order of entry. This means, you are not required to begin with the large transistor, the short transistor or the narrow one. Just type in the geometries into each line as you like.

Figure 14 Top view of a multifinger MOSFET

In addition to the standard BSIM4 definitions, columns for SA, SB and SD are available, see Figure 15 for a definition of the parameters used in shallow trench isolation modeling.

Figure 15 Shallow Trench Isolation related parameters

Moreover, each transistor is assigned to two different categories as is described in the following section.

Categories

The Device List shows one or more category columns, depending on what you are extracting: The first one is the size category, the second one is the STI category, and the third one is the WPE category.

The Configuration menu enables you to Sort the entries into an order or to Set the size category of your devices manually. See Transistors for DC measurements.

You can use Configuration > Sort or the appropriate icon to set the size category of your devices automatically. Otherwise, you are required to enter the size category manually using the form shown in Figure 16.

Figure 16 Set size category

The device category is used for extraction purposes. See Transistors for DC measurements in the BSIM3 Characterization chapter for an explanation of categories and requirements for proper extraction of device parameters as well as the paragraph about Stress Effect Modeling inside Chapter 4, "BSIM4 Characterization".

If you would like to delete devices:

According to your choice of temperatures on the Temperature Setup folder, one or more columns marked with the temperatures you have entered appear. The fields of those columns show either (0) for no measured data available, (M) for DUT already measured or (-) for DUT not to be measured at that temperature.

You can enter a comment for each DUT. If you are using a switch matrix, you can enter a module name and the pin numbers of the switch matrix pin connections to the transistor in the fields below the node names (those fields are present only if the use of a switch matrix is selected on the Switch Matrix folder). See Figure 17 for details.

Connections to the DUTs

The following figure shows an example for a connected device under test (DUT) to the source measurement units (SMUs) during DC Transistor measurements. The node numbers shown are to be entered into the fields on the Device List folder, see Figure 11. The above mentioned figure shows "0" under all terminal names. Those numbers have to be changed to "10" for the gate, "12" for the source, "11" for the bulk, and "9" for the drain terminal to reflect the connections used inside the following schematic. Please be careful to use the names SMU1...SMU4 during hardware setup in IC-CAP, since these are required by the measurement module of the BSIM3/4 and PSP Modeling Packages.

Figure 17 SMU connections to the device under test

Measurement of the Devices

Once all DUTs are entered with their respective geometries, switch matrix pin connection, and measurement temperatures, the actual measurement of devices can take place. For this purpose, you can use predefined measurement sets if you use the standard measurements called idvg and idvd.

If you've designed a specific measurement for your purposes, you can also define a Measurement Set for those measurements. Select the Measurement subtree and Configuration > Configure Measurement Set from the menu. A window opens where you can define a name for the new measurement set and the measurement, for which this set should be used.

After selecting OK, the newly defined set appears in the list of available measurement sets.

Now you can assign the measurement sets to your devices. For this purpose, select the Device List inside the tree view, then select Configuration > Configure Measurement Set from the menu.

A window opens for you to select the appropriate measurement set to use for each of your devices to be measured.

The following figure shows the Assign Measurement Sets to Devices window. Select a device, then select one of the available Measurement Sets to use for this device. The list - and the appropriate column on the Device List subfolder - will be updated to reflect the actual assignment of Measurement Sets to Devices.

Figure 18 Configuration of Measurement Sets

Starting the measurement of the devices

You will find an appropriate icon inside the row of icons or you can use Data > Measure from the menu.

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To start measurement of the devices: Click the Measure icon (or Data > Measure) from the menu and select the DUT or Module to be measured using the dialog box that opens. You can select a measurement temperature (if there is a temperature other than TNOM defined in the temperature setup folder) as well as a specific DUT or a Module (containing all DUTs to be measured at a specific temperature). If you select a temperature other than TNOM, (must be defined under TemperatureSetup), only the devices set up for measurement at that temperature are selectable for measurement. Start measurement with Measure (or MeasureDUT in BSIM4/PSP) on that dialog box. If measuring at elevated temperatures, be sure to wait until your devices are heated up or cooled down to the desired temperature.

If you select measurement of a module, all DUTs in this module are measured automatically if the use of a switch matrix is activated.

The DUTs/Setup folder in the BSIM3/4_DC_CV_Measure model contains an AutoMeasure setup for the Configuration DUT. Using this AutoMeasure setup, you can program automatic measurements for all DUTs in one module.

You'll find the macro "Example_Wafer_Prober" and it's transforms together with a description of the transforms in the Macro folder of the BSIM3/4_DC_CV_Measure model.

There is the choice of either synthesizing data or loading an MPS File.

This synthesized data uses the voltages set on the Measurement Conditions folder to generate "measurement" data from a known set of SPICE parameters. This feature might be especially useful to convert parameters of other models into BSIM4 parameters by loading the created "measurement data" into the extraction routines and extract BSIM4 parameters.

A check for the consistency of measured data can be activated by choosing Configuration > Check Data Consistency. This check is only possible when the Measurement subfolder is selected in the tree view. You will get a message if the rules of strict consistency are observed, otherwise you will get an error message. See Consistency Check of DC measurement data for multiple measured devices for details.

If the Device List subfolder is activated, you can check the DUT configuration by selecting Configuration > Check DUT Configuration from the menu. A window opens up to show misconfigured devices in detail. You can dump the contents of this window to the IC-CAP status window for reference.

Capacitance

Click on the + sign in front of Capacitance in the tree view to open the Measurement definitions and the Device List for preparing capacitance measurements. Select Measurement to enter the polarity of the device, the measuring voltages and connections of the instrument as shown in Figure 19.

Figure 19 Capacitance measurement definitions

Physically Connecting Test Structures to your Capacitance Measurement Device

The following figure shows how to connect the CV instrument to measure oxide and overlap capacitances. See also the paragraph on test structures for CV measurement. In Table 67 you'll find recommended test structures for specific capacitances to be measured together with recommended instrument connections.

Figure 20 Measurement of oxide and overlap capacitance

The following figure shows a typical gate-to-drain/source overlap capacitance diagram that you would expect to measure with this type of connection and the default values for Start, Step, and Stop voltage V_G.

Figure 21 Example diagram of measured overlap capacity

Test Structures for CV Measurements

See Table 67 for a table of recommended test structures for CV measurements.

Capacitance Device List

Click on Device List to define the devices to be measured and their respective geometries. See the following cut out for an example.

This folder provides fields to enter names of DUTs, geometries and switch matrix connections, and to select temperatures at which to measure the DUTs.

For each line, you can change the predefined name for the DUT and enter necessary geometrical data. For your convenience, only relevant data should be entered for a specific group of capacities. Relevant data fields are shown with white background and can be edited. Gray shaded data fields are not editable. For example, DUTs to measure bulk-drain junction capacitances do not require gate length and width (L, W), source area (AS) and perimeter length of source (PS) geometrical data. You only have to provide drain area (AD) and drain perimeter (PD) as well as the number of device fingers (NF) of the transistor to be measured. See Figure 22 for some details on capacitances and geometries.

Remember, all geometries are to be given in microns (µm).

Figure 22 Device geometries

Depending on your choice of temperatures on the Temperature Setup folder, one or more columns are marked with the temperatures you have entered appear. The fields of those columns show either (0) for no measured data available, (M) for DUT already measured or (-) for DUT not to be measured at that temperature.

You can enter a comment for each DUT. When using a switch matrix for capacitance measurements, you can enter a module name to measure one complete module with all its DUTs at once. This is intended for use with a prober card and taking measurements using the "step and repeat" function of a wafer prober. If you are using a switch matrix, you must enter the pin numbers of the switch matrix pin connections to the capacity you`re about to measure. The fields for high and low connection of the CV measuring instrument are marked H or L respectively, the ground connection is to be entered in the column marked 0. Since a ground connection is not required for every measurement, only those fields where a ground connection is not required are marked with a "-", all others are predefined to node No. "0". See Test Structures for CV Measurements for details on device geometries and requirements for proper extraction of capacitances of your devices like test lead connections and so on.

Diode

This part of the Data tree is used to define measurements for Junctions/Diodes of the devices to be measured. First, define the measurement conditions to reflect the desired voltages, Number of Points, and Compliances used for the measurement.

Next, select the Device List to enter names of DUTs, geometries and switch matrix connections, and to select temperatures at which to measure the DUTs. Don't forget to Save your setup after you've entered the DUT data. Table 66 briefly describes usable test structures to characterize diode behavior.

Figure 23 Diode device list

For each line, enter a name for the DUT and necessary geometrical data. For your convenience, only relevant data is to be entered for specific diodes. Relevant data fields have a white background, irrelevant data fields show a dashed line. For example, DUTs to measure bulk-drain diodes do not require source area (AS) and perimeter length of source (PS) geometrical data. You only have to enter drain area (AD) and drain perimeter (PD) as well as the number of device fingers (NF) of the diode to be measured. Remember, all geometries are to be given in microns (µm).

Depending on your choice of temperatures on the Temperature Setup folder, one or more columns marked with the temperatures you have entered appear. The fields of those columns show either (0) for no measured data available, (M) for DUT already measured or (-) for DUT not to be measured at that temperature.

Drain/Source – Bulk Diodes for DC Measurements

For test structures to measure DC Drain/Source-to-Bulk diodes, see Drain/Source – Bulk Diodes for DC Measurements.

Options

This folder lets you define options for the appearance of the plot windows.

Figure 24 Options folder

To change the plot window size, deselect the FIX_PLOT_SIZE.

To change the background color of a plot window, in the plot window select Options > Exchange Black-White. This changes a white background to black or a black background to white.

You can select if you want to include Delta W and Delta L into the VTH extraction process.

You can also set a value for the normalized reference current, as well as Channel width and length reduction values for VTH extraction. Those values should be entered as a dimension in meters.

Import Wizard

This feature enables you to import data measured using data formats or software not compatible with the IC-CAP format. The base for this task are project description files in spreadsheet format (.csv files). As a template for these csv files, the File > Export menu contains selections to create devices lists for DC, Capacitance, and Diode data. Load a project into the IC-CAP Measurement module, then select either DC device list, Capacitance device list, or Diode device list. A csv style file will be created. This file can be opened with EXCEL, for example. It contains all device data that was entered into the DC, Capacitance, or Diode DUTs folder.

You can edit the project document or you can create a new one using the same format. The first row of the sheet contains keywords. The values below these keywords will be read into IC-CAP and are assigned to the appropriate values in the MOS Modeling Toolkits. By default, the list contains a certain set of keywords. However, you can add more keywords to help define the import paths. All keywords can be used later to describe the name and the location of the stored .mdm file.

The Role of the MDM_FILE_CONSTRUCTOR

The major problem in accessing raw .mdm data is that there are many possible data organization schemes. The mdm files can be sorted according to the temperature in different directories and in one directory per device and so on.

To cover these different solutions, the MDM_FILE_CONSTRUCTOR is introduced. Its purpose is to enable you to define the mdm file structure. This is done using the different keywords from the device list files and the import GUI.

Functionality

The import routine performs the following steps:

1. Scanning the files

According to the definition in the MDM_FILE_CONSTRUCTOR, the import routine looks for all available files first, which are described by this expression. Let's assume that the MDM_FILE_CONSTRUCTOR looks like

<DIR>\<DEVICE_NAME>\<TEMP_ALIAS>\mos_<MDM_FILE>.mdm

and the different keywords have the following entries:

<DIR>	<DEVICE_NAME>	<TEMP_ALIAS>	<MDM-FILE>
C:\tmp	Transistor_1	minus40	idvg
	Transistor_2	25	idvd
	Transistor_3	125	my_idvg

One possible file would be:

c:\tmp\Transistor1\minus40\mos_idvg.mdm

In this case, all possible combinations using the 4 keywords are generated, and each combination is then checked as to whether or not the file exists.

2. Import to IC-CAP

In the second step, the existing files are imported to IC-CAP. The necessary device information (L, W, e.t.c.) is taken from the device list and is added to the file. Furthermore, different checks are performed to make sure that the file is correct. If necessary, settings are corrected or added. In particular, these are:

After these modifications, the files are saved in the new project directory.

Example Export/Import Procedure

Export a csv Sheet as a Template

Open the DC_CV_Measurement module using the model you would like to import data into (e.g., BSIM4_DC_CV_Measure). Open a project (e.g., BSIM4_for_experts). Choose File > Export > DC device list (or Capacitance device list or Diode device list). A window opens for you to enter the name and path for the file. Once the entries are made, click Save. A .csv file will be saved with the specified name and path. The following figure shows the file.

Figure 25 Via Export generated csv sheet

You can edit the template to suit your specific needs (e.g., dimensions, device names, and so on).

Import Data into the BSIM4 MOS Modeling Package

After adapting the template to your project, select File > Import > Import Wizard (.mdm). The mdm Import Wizard window opens and the "Model"_DC_CV_Measure window is temporarily closed. Select File > New from the wizard, browse to the location where you want to store the project, and enter a name for your project. Select Create.

On the Temperature Setup folder, enter TNOM in Kelvin and, if used, a temperature alias. If you have data measured at other temperatures, add those temperatures as well.

Next, open the DC Transistor DUTs folder, select the desired device list as well as the Basic data directory, then enter the MDM_FILE_CONSTRUCTOR into the line at the bottom of the window (see the following figure). Don't forget to enter the correct .mdm description in import files assignment. Check the entries by clicking the Assignment icon to check the input/output assignment.
Correct, if necessary.

In the following example, the files in the Import Wizard window are located in G:\tmp and are named W25_L50_idvg.mdm respective W25_L50_idvd.mdm.

When all folders are filled with the required information, start the automatic checking process by clicking . The Import check window appears—see below.

You can check each setting step-by-step using the Next button or you can Do All checks automatically. You will get error messages if something is wrong.

If no errors occur, the Finish button on the Import window will be activated. Press this button to complete the import process before saving the changes and exiting the wizard. The DC_CV_Measure GUI opens again and the project just created is now ready to open.