FACULTY OF ENGINEERING LAB SHEET ENT 3036 SEMICONDUCTOR DEVICES TRIMESTER

Transcription

1 FACULTY OF ENGINEERING LAB SHEET ENT 3036 SEMICONDUCTOR DEVICES TRIMESTER 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. Page 1 / 20

2 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) Page 2 / 20

3 Figure 2.2: IV System Connection 2.3 Device Setup 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 Page 3 / 20

4 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 Page 4 / 20

5 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 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: K Figure 2.3.1B: Verify the GPIB address linked to the ICS ssytem Global Setup for Instruments for IV Measurement From the ICS main menu icon option, and click Setup Editor to activate the Setup menu as in Figure Click on New to add in ID_VG setup, choose Device as N-Channel Page 5 / 20

6 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 : Setup Editor Menu 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: 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 Page 6 / 20

7 Figure 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 : Project File MOSFET IV Experiment Data Sheet View 3. IV Measurement Procedure 3.1 Drain Current (ID) versus Drain Voltage (VD) Curve Instrument Test Condition Setup for ID vs VG Characterization From the Setup Editor (See Figure ), 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 [Value = 4 V] Page 7 / 20

8 Figure 3.1.1: SMU Setup Menu 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 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 Page 8 / 20

9 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 Setup for Data Sheet View Once procedure had been completed, you should be in the main menu of ICS Click on the Options Pull-down menu and select Workspace as shown in Figure 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 : Workspace Menu Option 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. Page 9 / 20

10 Once completed, click on Apply button and then Done to return to ICS main menu 3.2 Performing Measurement Figure : Define Data View Menu 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 Figure 3.2. of the main menu to activate the Measure Dialogue Menu as in 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 Page 10 / 20

11 3.3 Graph Plotting Figure 3.2: Measure Dialogue Upon completion of the IV measurement, plot the following graphs: 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 Page 11 / 20

12 3.4 MOSFET Family Characterization After the measurement had been completed for ID_VG curve, go to the Setup Editor as in procedure 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 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 To setup FAMILY characterization measurement, select FAMILY from the Setup Editor drop down list Figure 3.4.3: Selecting a Setup 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: Page 12 / 20

13 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 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 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 As in procedure to 3.4.3, select the Setup Name GM_VTH Set the test conditions for the respective SMU 1 and SMU 2 as follows (3.4.4): 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 Page 13 / 20

14 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 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 Once completing procedure to , EXIT from Setup Editor and return to ICS Main Menu 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) Page 14 / 20

15 3.5.6 To extract the GM, include the formula as stated in EQ in the ICS transform Editor as follows: Click on the Transform Editor icon in the ICS main menu, the Transform Editor Menu will be displayed as in Figure Figure : Transform Editor Menu Click on the Setup Name to select GM_VTH from the drop down list Enter on the first box provided, the transform formula for GM as follows: GM=DELTA(ID)/DELTA(VG) (EQ 3.5.5) 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 Click on DONE when completed and return to ICS Main menu Repeat as in procedure for selection of Vectors to be displayed in the Data Sheet View for GM_VTH setup and exit to ICS Main menu when completed 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 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. Page 15 / 20

16 3.6.1 As in procedure from to 3.4.3, select the Setup Name SUB_VTH Set the test conditions for the respective SMU 1 and SMU 2 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: 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 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 Page 16 / 20

17 Once completing procedure to , EXIT from Setup Editor and return to ICS Main Menu 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 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 will locate the maximum point of the curve selected. Minimum Find: To find the minimum of a will locate the minimum point on the curve selected. plotted graph, click on button. The active cursor plotted graph, click on button. The active cursor 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. Page 17 / 20

18 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 Linear Fit: Require two cursors to be activated, click on Exponential Fit: Require two cursors to be activated, click on Tangent Fit: Require one cursor to be activated, click on button. button. button. button. 5. MOSFET Characterization Analysis 5.1 From the graph obtained in 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 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) Page 18 / 20

19 5.3 Compute the slope for Sub-Threshold Current from the graph obtained in 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 picture below. Oxide thickness x max =100nm, N A = /cm 3, channel width/length, W/L = 8, effective electron mobility, µ n= 625 cm 2 /V-sec, and T = 300K. Employing the bulk-charge theory, determine I D when V G = V D = 1V. (10 points) (Level 3 Application) S VG = VD Ground p-si Ground Page 19 / 20

20 Marking Scheme Lab (10%) Assessment Components Hands-On & Efforts (2%) On the Spot Evaluation (2%) Lab Report (6%) Details The hands-on capability of the students and their efforts during the lab sessions will be assessed. The students will be evaluated on the spot based on the lab experiments and the observations on the transistor characteristics. Each student will have to submit his/her lab final report within 7 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 and/or conference proceedings (e.g. 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 [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. Page 20 / 20