Simultaneous Capacitance Voltage (CV) Measurement

MOSFET IV Characterization

FACULTY OF ENGINEERING

LAB SHEET

ENT 3036 SEMICONDUCTOR DEVICES TRIMESTER 2 2013-2014

SD1 – I-V MEASUREMENT OF MOS CAPACITOR

*Note: On-the-spot evaluation may be carried out during or at the end of the experiment. Students are advised to read through this lab sheet before doing experiment. Your performance, teamwork effort, and learning attitude will count towards the marks.

/ 22 MOSFET IV Characterization

1. Introduction

A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a four terminal device that consist of a Gate (G), Source (S), Drain (D) and Substrate (B). The gate structure that controls the conduction is simply a MOS capacitor.

When the gate is biased such that the silicon surface under the gate is in accumulation or depletion (Vg < Vth), the channel region contains very few electrons and no appreciable current can flow between the drain and source.

When Vg is biased so that inversion occurs (Vg Vth), a significant number of mobile electrons are generated adjacent to the silicon channel under the gate. This results in the formation of a conducting channel between the drain and source.

Thus, the MOSFET structure allows one to modulate the source-drain conductance with voltage apply at the gate terminal.

1.1 Objectives:

1. To investigate the effect of bias on the operating modes of a MOSFET 2. To analyze the operating characteristics of a MOSFET

2. Equipment and Test Setup Procedure

2.1 Equipment Requirement

 Keithley model 93A IV Semiconductor Test System consisting of o 1 x Keithley model 236 Source Measure Unit o 1 x Keithley model 238 Source Measure Unit o 1 x Keithley model 2361 Trigger Controller o 3 x GPIB Cables o 4 x BNC to BNC Co-axial Cables  2 x Keithley model 237-ALG-2, Triaxial to Alligator Clips Cable  System Controller with Metrics Interactive Characterization Software (ICS) – Personal Computer

2.2 Connection

Please check the system connection with the diagram as in Figure 2.2

Once the connection is established, turn on the IV measurement system by pushing the “POWER ON / OFF” switch of the respective instruments in the following order:  Keithley model 2361 Trigger Controller  Keithley model 236 Source Measure Unit (SMU 1)  Keithley model 238 Source Measure Unit (SMU 2)

 System Controller (Personal Computer)

Figure 2.2: IV System Connection

2.3 Device Setup

2.3.1 Device Connection

WARNING: Before connection to the device under test, ensure that the IV System IS NOT in the OPERATE mode. (If the system is in OPERATE mode, the LED on any of the Source Measure Unit will light. To deactivate the OPERATE mode, use the METRICS ICS software and activate the MEASURE dialogue option menu and click on STOP button)

Check with the Lab. Supervisor on the pin configuration of the MOSFET device given for the session before proceeding. Make connection as indicated in the connection diagram shown in Figure 2.3.1

Figure 2.3.1: Connection Diagram for MOSFET device Testing

Ensure that Cable 1 (Triaxial side) is connected to SMU 1 (Keithley model 236) and Cable 2 (Triaxial side) is connected to SMU 2 (Keithley model 238) as indicated in the system connection diagram of Figure 2.2

Connect the MOSFET device given as follow:

 Clip the RED alligator clip of Cable 1 to the Gate Terminal of MOSFET device  Clip the GREEN alligator clip of Cable 1 to the Source Terminal of MOSFET device  Clip the RED alligator clip of Cable 2 to the Drain Terminal of MOSFET device  Clip the GREEN alligator clip of Cable 2 to the Source Terminal of MOSFET device

Once the connection to the MOSFET device is done, ensure that the device pin and the alligator clips ARE NOT SHORTED to one another. Leave the connected device on a NON CONDUCTIVE BASE

2.3 Starting Metrics ICS and Setup of Experiment

Double-Click on the Metrics ICS icon on the Desktop to execute Metrics ICS. If Figure 2.3.1A is not showing the same attribute, simply go to Project Manager to change the attribute as described in Figure 2.3.1A

2.3.1 Selection of Experiment File

 From the File Menu Options, Select “Set Project Name”.  Select the following: Year: 2011 Course: Electronics Experiment: ID-VG Package: TO-92 Device Type: 2N7000 Course ID: SD 1 Comment: Group ( no. ) Figure 2.3.1A: File Open Select

 Select Instrument, as shown in Figure 2.3.1B.  Click “KI2361” in “Availability” column in “Instrument” dialogue box to highlight it and the click “Connect” button. “K1236” appears in “Selected” column.  Click “KI2361” in “Selected” column and click “Config…”. “KI2361 TCU Setup” dialogue box appears.  Poll the GPIB address as below:

K12361 17

Figure 2.3.1B: Verify the GPIB address linked to the ICS ssytem

2.3.2 Global Setup for Instruments for IV Measurement

2.3.2.1 From the ICS main menu icon option, and click “Setup Editor” to activate the Setup menu as in Figure 2.3.2.1. Click on “New” to add in ID_VG setup, choose “Device” as N-Channel MOSFET. From this new setup, highlight each instrument and click on the respective nodes on the MOSFET (G-SMU1, D- SMU2, B & S – GND).

Figure 2.3.2.1: Setup Editor Menu

2.3.2.2 From Setup Editor Menu, click “Opts” icon to activate the KI2361 Global Setup Menu for IV overall system setup  Setup the Global Menu as follows: o Max Voltage: 20 o Max Current: 900.0m o Auto Rng Delay: 0.000 o Trigger Model: Parallel o Local Sense Lockout: Check Box o Time Stamp Data: Check Box o Disable Message: Uncheck Box

Once completed, click “OK” and exit to Editor Setup Menu

 Figure 2.3.2.2 shows the Project File of the IV Characterization experiment upon opening. A Data Sheet View will be displayed. This is the main menu of ICS

Figure 2.3.2.2: Project File MOSFET IV Experiment Data Sheet View

3. IV Measurement Procedure

3.1 Drain Current (ID) versus Drain Voltage (VD) Curve

3.1.1 Instrument Test Condition Setup for ID vs VG Characterization

 From the Setup Editor (See Figure 2.3.2.1), click on the SMU 1 instrument icon (That is connected to the Gate, G Terminal), the SMU setup menu for SMU1 (Keithley model 236) will be activated as in Figure 3.1.1. [Value = 4 V]

Figure 3.1.1: SMU Setup Menu

3.1.1.1 Setup SMU 1 conditions for the MOSFET GATE terminal as follows:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VG) Measure: Current, (IG) Measure Rng (Range) Select: AUTO Force Conditions: Mode: CONST Value: 4.0 No. of Points: 101 Compl: 100m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0

Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

Once SMU 1 test conditions are completed, click on “OK” button and exit to Editor Setup Menu. In the same manner, setup the test conditions for SMU 2 by clicking on SMU 2 icon in the Editor Setup

3.1.1.2 Setup SMU 2 conditions for the MOSFET DRAIN terminal as follows:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VD) Measure: Current, (ID) Measure Rng (Range) Select: AUTO Force Conditions: Mode: SWEEP Type: LIN Start: 0.0 Stop: 4.0 No. of Points: 101 (The Step Size is automatically calculated from [Stop – Start] / [No. of Points]) OR (No. of Points = [Stop – Start] / [Step Size]). Thus either key in No. of Step OR Step Size.

Compl: 600m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0 Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box Once SMU 2 test conditions are completed, click on “OK” button and exit to Editor Setup Menu. After completing all the setup for both SMU test, click on “DONE” button on the Editor Setup Menu and exit to the Main ICS Menu.

3.1.2 Setup for Data Sheet View

Once procedure 3.1.1 had been completed, you should be in the main menu of ICS

3.1.2.1 Click on the Options Pull-down menu and select “Workspace” as shown in Figure 3.1.2.1.

 Check all the boxes in the

“Options” section for the following: Show Messages Eng Notation Enable Data View Autoscale Update During

 Once completed, click “OK” and return to ICS main menu

Figure 3.1.2.1: Workspace Menu Option

3.1.2.2 Click on the “DataView” icon on the ICS main menu to display the Define DataView options.

 Select the “Setup Name” to ID_VG from the drop down list  Check the Box for “Column Vectors” in the “Data Orientation”  From the “Data Vectors” located at the bottom left-hand of Menu, select “All Vectors”.  Click on “Add>” button to indicate all measurement parameters to be viewed in the Data Sheet. The vectors to be included will be shown in the “View Vectors” column.  Once completed, click on “Apply” button and then “Done” to return to ICS main menu

Figure 3.1.2.2: Define Data View Menu

3.2 Performing Measurement

Once the appropriate and necessary setup had been completed from procedures 2.2 to 3.1, measurement can be made.

Click on the “Measure” icon of the main menu to activate the Measure Dialogue Menu as in Figure 3.2.

Note: The Measure Dialogue Menu can be activated and de-activated by clicking on the “Measure” icon button.

 Select the Setup Name “ID_VG” from the drop down list.  Select measurement mode to “STANDARD” from the drop down list  Ensure that all cables to the IV measurement system and device pins are properly connected  Click on the “SINGLE” button on the Measure Dialogue to begin the Measurement  Once the measurement is completed, the results will be reflected in the Data Sheet View

Figure 3.2: Measure Dialogue 3.3 Graph Plotting

Upon completion of the IV measurement, plot the following graphs:

3.3.1 Drain Voltage, VD versus Drain Current (X-axis=VD, Y1-axis=ID)

Scale Type: LIN for both axes

The graphs can be plotted as follows:

 Click on the Plot View icon  From the Plot View Setup Menu, select the appropriate measurement vectors from the drop down list of Data Group for the respective axis  Ensure that selection of “Scale Type” is correct for each graph  Click “Apply” then “Done” when completed to exit from Plot View Setup and return to ICS main menu

Figure 3.3: Plot View Setup Menu

3.4 MOSFET Family Characterization

After the measurement had been completed for ID_VG curve, go to the Setup Editor as in procedure 2.3.2.1.

3.4.1 Click on the “Copy” icon on the Setup Editor Menu

This will copy the present setup of ID_VG as another setup for the next measurement

3.4.2 When prompted for a name in the Copy Setup, enter “FAMILY” in the box and click on “OK” when done. The Setup Editor now will consist of two setups, ID_VG and FAMILY

3.4.3 To setup FAMILY characterization measurement, select “FAMILY” from the Setup Editor drop down list

Figure 3.4.3: Selecting a Setup

3.4.4 Similarly as in procedure 3.1.1, setup SMU 1 as follows:

SMU 1 conditions for the MOSFET GATE terminal: Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VG)

Measure: Current, (IG) Measure Rng (Range) Select: AUTO Force Conditions: Mode: STEP Start: 3.0 Stop: 4.5 No. of Steps: 4 (The Step Size is automatically calculated from [Stop – Start] / [No. of Steps]) OR (No. of Steps = [Stop – Start] / [Step Size]). Thus either key in No. of Step OR Step Size

Compl: 100m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0 Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

Once SMU 1 test conditions are completed, click on “DONE” button and exit to Editor Setup Menu. There will be no change for the SMU 2 setup (SMU 2 test condition setup remains the same as in ID_VG measurement). Exit to ICS main menu.

3.4.5 Repeat procedure 3.2 to perform the MOSFET FAMILY Characterization. Take note to change the Setup Name to “FAMILY” from the drop down list of the Measure Dialogue Menu

3.4.6 Once the measurement is completed, plot the graph of Drain Current (ID) vs Drain Voltage (VD) following procedure 3.3 for graph plotting (Adjust the scale whenever necessary) (X-axis=VD, Y1-axis=ID) Scale Type: LIN for both axes

3.5 Transconductance (GM) and Threshold Voltage (Vth) Extraction

Upon completion of FAMILY characterization, proceed to setup the Transconductance (GM) and Threshold Voltage (Vth) extraction.

3.5.1 As in procedure 3.4.1 to 3.4.3, select the Setup Name “GM_VTH”

3.5.2 Set the test conditions for the respective SMU 1 and SMU 2 as follows (3.4.4):

3.5.2.1 SMU 2 conditions for the MOSFET DRAIN terminal:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VD) Measure: Current, (ID) Measure Rng (Range) Select: AUTO Force Conditions: Mode: CONST Value: 0.1 No. of Points: 201 Compl: 600m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0 Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

3.5.2.2 SMU 1 conditions for the MOSFET GATE terminal:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VG) Measure: Current, (IG) Measure Rng (Range) Select: AUTO Force Conditions: Mode: SWEEP Type: LIN Start: 0.0 Stop: 5.0 No. of Points: 201 (The Step Size is automatically calculated from [Stop – Start] / [No. of Points]) OR (No. of Points = [Stop – Start] / [Step Size]). Thus either key in No. of Point OR Step Size Compl: 100m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0

Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

3.5.4 Once completing procedure 3.5.2.1 to 3.5.2.2, EXIT from Setup Editor and return to ICS Main Menu

3.5.5 The transconductance, GM is calculated from the change in the drain current to a change in the gate voltage; GM = ID / VG (EQ 3.5.5)

3.5.6 To extract the GM, include the formula as stated in EQ 3.5.5 in the ICS transform Editor as follows: 3.5.6.1 Click on the “Transform Editor” icon in the ICS main menu, the Transform

Editor Menu will be displayed as in Figure 3.5.6.1

Figure 3.5.6.1: Transform Editor Menu

3.5.6.2 Click on the “Setup Name” to select “GM_VTH” from the drop down list

3.5.6.3 Enter on the first box provided, the transform formula for GM as follows:

GM=DELTA(ID)/DELTA(VG) (EQ 3.5.5)

3.5.6.4 Once the formula for GM had been completed, click on “SAVE” button; if there is no mistake made in entering the formula for GM, the formula will be acknowledged into the transform.

3.5.6.5 Click on “DONE” when completed and return to ICS Main menu

3.5.6.6 Repeat as in procedure 3.1.2.2 for selection of Vectors to be displayed in the Data Sheet View for GM_VTH setup and exit to ICS Main menu when completed

3.5.6.7 Repeat procedure 3.2 to perform the MOSFET GM_VTH Extraction. Take note to change the Setup Name to “GM_VTH” from the drop down list of the Measure Dialogue Menu.

3.5.6.8 Once the measurement is completed, plot the graph of Drain Current (ID) vs Gate Voltage (VG) and Transconductance (GM) vs Gate Voltage (VG) following procedure 3.3 for graph plotting in the same plot (X-axis=VG, Y1-axis=ID, Y2- axis=GM) Scale Type: LIN for all axes

3.6 Sub-Threshold Current Conduction

Upon completion of GM_VTH characterization, proceed to setup the Sub-Threshold (Sub-VTH) conduction.

3.6.1 As in procedure from 3.4.1 to 3.4.3, select the Setup Name “SUB_VTH”

3.6.2 Set the test conditions for the respective SMU 1 and SMU 2 as follows:

3.6.2.1 SMU 1 conditions for the MOSFET GATE terminal:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VG) Measure: Current, (IG) Measure Rng (Range) Select: AUTO Force Conditions: Mode: SWEEP Type: LIN Start: 0.0 Stop: 2.5 No. of Points: 101 Compl: 100m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0 Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

3.6.2.2 SMU 2 conditions for the MOSFET DRAIN terminal:

Stimulus: Voltage Stimulus Rng (Range) Select: AUTO Measure: Voltage, (VD) Measure: Current, (ID) Measure Rng (Range) Select: AUTO Force Conditions: Mode: CONST Value: 0.1 No. of Points: 101 Compl: 300m Report Compl: Check Box Options: Delay (sec): 0.0 Hold (sec): 0.0 Integration: 50Hz Filter: 1 RDG Suppress: Uncheck Box Pulse mode: Uncheck Box

3.6.2.3 Once completing procedure 3.6.2.1 to 3.6.2.2, EXIT from Setup Editor and return to ICS Main Menu

3.6.2.4 Repeat procedure 3.2 to perform the SUB-ITH measurement. Take note to change the Setup Name to “SUB_ITH” from the drop down list of the Measure Dialogue Menu.

3.6.2.5 Once the measurement is completed, plot the graph of Drain Current (ID) vs Gate Voltage (VG) following procedure 3.3. (X-axis=VG, Y1-axis=ID) Scale Type: LIN for X-axis and LOG for Y1 axis

4 Graph Plot Cursor Functions and Features

4.1 Cursor Functions

The following describes some of the features in the graphical plot to aid user on graphical extraction

 Click on the “Cursors Option Button” on the left of the graph to display the various cursor functions. (As shown in Figure 4.1)  To activate any of the cursor, click on the button next to the cursor shape. You can then use the mouse to drag the cursor along the plotted curve. On the bottom of the graph, the cursor position will also be indicated corresponding to the cursor that is activated.

Figure 4.1: Cursor Select Functions

Maximum Find: To find the maximum of a plotted graph, click on button. The active cursor will locate the maximum point of the curve selected.

Minimum Find: To find the minimum of a plotted graph, click on button. The active cursor will locate the minimum point on the curve selected.

Interpolation ON/OFF: In order to use interpolation, click on button. The interpolation will enable the cursor to be moved in between two sweep points so that a more accurate extraction of the value can be obtained.

4.2 Line Fit Functions  To activate the line fit functions, click on the “Fits” button on the left of the graph. (As shown in Figure 4.2). Then, click on the “Fit #1” or “Fit #2” to extend the line fit functions  Click on the cursor shape that has been previously activated. (Note: At least one of the cursor must be made active in order to use the line fit function)  Move the cursor/s to the position of the curve where extraction is required

Figure 4.2: Line Fit Functions  On the bottom left of the plotted graph, the line fit value will be indicated with the X and Y intercept values

Cursor Fit: Require two cursors to be activated, click on button. Linear Fit: Require two cursors to be activated, click on button.

Exponential Fit: Require two cursors to be activated, click on button.

Tangent Fit: Require one cursor to be activated, click on button.

5. MOSFET Characterization Analysis

5.1 From the graph obtained in 3.3.1 of ID vs VD, sketch the graph on the space provided. Identify and comment on the various operation regions of the MOSFET device from the graph. (Level 1 – Knowledge)

5.2 From the graph obtained in 3.5.6.8 of ID vs VG (GM_VTH Extraction), identify the Threshold Voltage of the MOSFET device. (Hint: Obtain VG when GM is at its maximum. Locate with cursor the point on ID-VG curve at VG=GM (max). Use tangent fit to point on ID-VG curve)

VTH = ______V (Level 1 – Knowledge)

5.3 Compute the slope for Sub-Threshold Current from the graph obtained in 3.6.3.5 of ID vs VG when VG = 1.5V and 2.1V.

Sub_ITH Slope = ______(Level 3 – Application)

6. Questions

6.1 Compare the similarity and differences of p-type MOS-C (MOS-Capacitor), n- type MOS-C, NMOS (n-type channel MOSFET) and PMOS (p-type channel MOSFET). (12 points) (Level 6 – Evaluation)

6.2 Explain the output characteristics and transfer characteristics of NMOS (n- type channel MOSFET) and PMOS (p-type channel MOSFET), in enhancement & depletion modes. Describe also the three region of operation for the MOSFET. (18 points) (Level 2 - Comprehension)

6.3 For a given n-channel MOSFET where its gate and drain are tied together as 16 3 picture below. Oxide thickness xmax =100nm, NA = 10 /cm , channel 2 width/length, W/L = 8, effective electron mobility, µn= 625 cm /V-sec, and T = 300K. Employing the bulk-charge theory, determine ID when VG = VD = 1V. (10 points) (Level 3 – Application) V = V S G D

Groun d p-Si

Groun d

Marking Scheme

Lab Assessment Components Details (10%) Hands-On & Efforts (2%) The hands-on capability of the students and their efforts during the lab sessions will be assessed. On the Spot Evaluation The students will be evaluated on the spot based on the lab (2%) experiments and the observations on the transistor characteristics. Lab Report Each student will have to submit his/her lab final report within 7 (6%) days of performing the lab experiment. The report should cover the followings: 1. Introduction, which includes background information on metal oxide semiconductor field effect transistor. 2. Experimental section, which includes the general summary of the lab experiment work. 3. Results and Discussions, which include the measured results, analysis, and evaluations, with neat graphs/images of the results and recorded data.

4. Conclusion, which includes a conclusion on the experimental. 5. List of References, which includes all the technical references cited throughout the entire lab report.

The report must have references taken from online scientific journals (e.g. www.sciencedirect.com, http://ieeexplore.ieee.org/xpl/periodicals.jsp, http://www.aip.org/pubs/) and/or conference proceedings (e.g. http://ieeexplore.ieee.org/xpl/conferences.jsp).

Format of references: The references to scientific journals and text books should follow following standard format: Examples: [1] William K, Bunte E, Stiebig H, Knipp D, Influence of low temperature thermal annealing on the performance of microcrystalline silicon thin-film transistors, Journal of Applied Physics, 2007, 101, p. 074503. [2] Hodges DA, Jackson HG, Analysis and design of digital integrated circuits, New York, McGraw-Hill Book Company, 1983, p. 76.

Reports must be typed and single-spaced, and adopt a 12-point Times New Roman font for normal texts in the report. Any student found plagiarizing their reports will have the assessment marks for this component (6%) forfeited.

The lab report has to be submitted to the staff in Nanotechnology Laboratory 2. Please make sure you sign the student list for your submission. No plagiarism is allowed. Though the electrical characteristics of the measured transistor from the same group can be similar, the report write-up cannot be duplicated for group members. The individual report has to be submitted within 7 days from the date of your lab session. Late submission is strictly not allowed.