MDC CV SYSTEM OPERATION PROCEDURE

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1 MDC CV SYSTEM OPERATION PROCEDURE Rev B

2 Table of Contents Contents Table of Contents Purpose / Scope Reference Documents Operation Manual Equipment / Supplies / Material Safety Set Up Procedures Operation Procedures Process Data Revision History Page 1

3 1. Purpose / Scope This document provides the operating instructions for the MDC CV Station including the MDC software, HP4884 Impedance Bridge and the micromanipulator probe setup 2. Reference Documents 1. Semiconductor Material and Device Characterization, Dieter K. Schroder 2. Agilent Impedance Measurement Handbook, 4 th edition. 3. ASTM F , Standard Test Method for Characterization of Metal-Oxide-Silicon (MOS) Structures by Capacitance-Voltage Measurements (1988). 4. MOS (Metal Oxide Semiconductor) Physics and Technology, E. H. Nicollian & J. R. Brews. 3. Operation Manual HP 4284A Precision LCR meter Operation Manual Software Help within the MDC program 4. Equipment / Supplies / Material HP 4284 Precision LCR meter HP 4140 picoammeter HP 4083A Switching Controller MDC Probe Box with vacuum chuck and 2 micromanipulators MDC Software on Windows XP computer Tweezers to handle samples Gloves to handle probe needles and probe components 5. Safety There are no specific safety issues with this probe system. However, cleanliness is a concern so please use tweezers to handle wafers or samples. In addition, please use clean room gloves if you need to change probe needles or handle any other probe component. 6. Set Up Procedures Connections 1. The 4284A meter has four measurement terminals labeled: Lcur, Lpot, Hpot, and Hcur. These four terminals need to be connected using co-ax connectors to the corresponding terminals on top of the gray switch box (controlled by the HP4083A). 2. The HP4140 I input needs to be connected to the pa terminal on the gray switch box; 3. The HP4140 Voutput VA connects to switch box DC voltage source 4. For device probing the two co-ax output connectors (switch box, left side) are connected to the coax connectors on the side of the probe box; 5. The Vgate terminal is connected to the top co-ax on the probe box 6. The Vsub terminal is connected to the bottom co-ax on the probe box Page 2

4 Wafer Probing The MDC probe box contains a vacuum chuck and two micromanipulators with vacuum hold-downs. Rotate the microscope over your sample, turn on the light and focus. If your sample has a top side probe pad and a back side contact, connect the micromanipulator co-ax to the top co-ax on the inside of the probe box and the chuck contact to the bottom co-ax connector. If your sample only has top side contacts, connect both micromanipulators to the two co-ax connectors. The bottom co-ax should be connected to the backside (substrate) of the sample. 7. Operation Procedures HP 4284A LCR Meter The key equipment is the HP 4284A Precision LCR meter. This meter can be controlled remotely using MDC software on a Windows computer and also manually using front panel commands. It is often valuable to connect a sample and manually check for stable readings. A brief overview of the front panel operation is given in this section; software control is covered in the following section. The on/off switch is on the left front side; on the right side is a button for local control if the HP4284 was left under remote control. The main sections include the display with soft keys on the right side, the number pad with enter key, and the DC bias toggle switch. Display: At the top of the display there are six fields: FUNC (Z- Θ, Cp-Gp, Cs-Rs, etc) RANGE (auto) FREQ (100k) BIAS (0.000V) LEVEL (ac voltage, 25-50mV) INTEG (med) The arrow keys (to the right of the display) allow the selection of each of these fields. Inputs for each fields are available using the softkeys on the right side of the display or by keying numbers on the key pad and then the enter key. Select the following: FUNC field and choose Z-Θ, Cp-G, Cs-Rs or Ls-Rs etc; note that Z-Θ are the fundamental parameters. FREQ field and the soft keys allow the frequency to be increased/decreased by either decade steps or smaller steps within each decade. BIAS field and you can type a DC voltage value on the key pad, hit the enter key (far right). Then turn on the bias with the toggle key (bottom center, red light = ON). The current readings, (depending upon function) for example Cp, Gp) are in the center of the display, along with corresponding units (pf, nf, uf or us, ms). Below the current readings are the ac Vm ( V) and Im (10 ua) values and are useful monitors of good test values; excessive leakage currents cause Vm to decrease and Im to increase. At the bottom is the field CORR: (open), indicating the type of correction (Open and/or Short). At the top center are three buttons, [Display], [Meas Setup], [Catalog/System]. [Display] opens the screen as described in the previous section. [Meas Setup] shows a set up screen including averaging and corrections. [Catalog/System] is generally not useful except for a few system functions For example, to make a manual measurement, choose a function [Cp-Gp], the frequency [100k], enter the ac level [25mV], leave the range on [auto], key in a dc bias if needed (and turn on), and leave integration at medium. Cp and Gp values are then displayed. Change conditions as needed. For example, enter voltages corresponding to depletion or accumulation conditions. Page 3

5 MDC Software Log into the computer using the local password (note that this computer is not on the network). The HP4284 LCR meter, HP 4140B pa meter and the switching controller HP 4083A must be turned on Open the MDC software by double clicking on the desktop CSM icon. When prompted for a password, hit return; there is no password for the software. The main menu page opens (Fig. 1). Fig. 1. Main Menu Page for the MDC software. The following paragraphs will describe the pages and commands to measure and plot a conventional CV. Additional capabilities are briefly discussed later or available using the on-screen Help menus. Page 4

A. Set up capacitance meter and sample properties a.

2 System Setup and Test page Fig 3. Capacitance Meter Settings page b.

Enter the following test condition information: Frequency (Hz), Measurement Speed (normal, fast, slow)

6 A. Set up capacitance meter and sample properties a. Select the [System Setup and Test], and the [Setup] page opens (Fig 2). Fig. 2 System Setup and Test page Fig 3. Capacitance Meter Settings page b. Select [Setup Meters]; [Capacitance Meter Settings] page (Fig. 3) opens. Enter the following test condition information: Frequency (Hz), Measurement Speed (normal, fast, slow) AC test signal voltage (typically 25mV to 50mV), Delay (in seconds) {larger delays reduce noise} Cable length (1m is typical for this setup) Select [Save & Exit]; Returns to [Setup] page (Fig. 2). Fig. 4. Configuration/set variables page Page 5

7 c. Next, on the [Setup] page, select [Configure System, Set Variables]; the Configuration page (Fig. 4) opens. Select the substrate material in the pull down menu (Si in this example); the corresponding Si parameters are entered in the following 6 boxes. If your substrate is not in the list, you will need to find the parameters for your material in the format needed for this table if you want the software calculations to be correct. In the top left column is the dielectric constant for the test sample. NOTE: Temperature control is no longer available on this system. Light control is manual; open the test chamber lid and/or turn on a light (turn on/off when prompted) during the test. Fill in the other parameters as needed. d. [Save and Exit]; returns to [Setup] page (Fig. 2) e. From the [System Setup and Test] page, select [Zero meter], and the [MOS connect options] page opens (Fig. 5). Fig. 5. MOS Connect Options page (do it now or optionally, else do later) Ensure that you have an open circuit. Select [Zero Capacitance Meter] and software will prompt you to Lift probe just out of contact, respond with [OK] or [Cancel]; If OK, the meter will zero out the cable capacitance. (Alternatively, you can Zero the meters at the beginning of the test sequence.) f. After the bridge goes through the zero procedures, you will return to [System Setup and Test] Fig 2. g. Select [Exit to Main Program] and return to the [Main Menu Page] (Fig. 1). B. CV program and test sequence 1. From the Main Menu Page, Select [Engineering MOS C-V Tests] and get the [MOS Mode] page (Fig 6). (Similar test sequences are in [Production MOS C-V tests] or [Engineering Junction Tests] categories.) The main button is the [MOS C-V Plotting], but you can also get to [C-T tests for Lifetime], [N-W tests], [Quasi-Static] test recipes (file type.qsv) and corresponding setup pages. See Help menu for more details on these tests. Page 6

Fig. 6. MOS Mode Page Fig. 7. MOS Function Page 2.

Select [Edit Test Recipe] to see a list of available engineering test recipes as shown in Fig.8.

(Note: The [Production MOS C-V Tests] and [Engineering Junction Test] will have a different set of test programs &

8 Fig. 6. MOS Mode Page Fig. 7. MOS Function Page 2. Select [MOS C-V Plotting] and get the [MOS Function] page (Fig 7). 3. Select [Edit Test Recipe] to see a list of available engineering test recipes as shown in Fig.8. Files in this section have file names xxxxx.mcv. (Note: The [Production MOS C-V Tests] and [Engineering Junction Test] will have a different set of test programs & names). Fig. 8. Engineering recipe page 4. This page contains two general test recipes, PSWP (for metal/oxide/p-si) and NSWP (for metal/oxide/n-si) as well as specific test recipes generated by users. You can evaluate the recipes and see if there is an existing recipe with desired conditions matching your Page 7

9 requirements. Alternatively, you can start with a basic recipe and save it to this area with your ID as name type xxxxx.mcv. 5. For example, open [PSWP] and you get the following [MOS-Test Recipe] page (Fig 9). Fig. 9. Test recipe page for PSWP 6. There are several important input parameters that are required on this test recipe page. 7. First, enter the electrode area (or Tox); note the correct units (cm^2, um^2 etc). 8. Second, Gate metal is a toggle, with several metal choices (Al, Au, N+poly, other). 9. Third, enter the gate metal work function for your sample if different from the nominal values. 10. Fourth, Measure Mode toggles from parallel (Cp-G) to series (Cs-Rs). 11. Fifth, Sweep Mode options are normal (from Vstart to Vstop), retrace (Vstart to Vstop & back to Vstart), hysteresis (V steps from 0 to Vstart, back to 0, on to Vstop, and back to 0) and Pulse (sweep from accumulation to deep depletion); examples are in Section Voltage range (Important Note, MDC assumes V s are specified on the substrate). a. Enter Vstart, Vstop and Vstep (Vstep may be + or ) for your test conditions; the number of data points is calculated. b. Note: the MDC software wants to start the test in Depletion, exposed sample to light, and then, steps to Accumulation conditions. (In the example, PSEP recipe, Vstart= - 5V puts +5V on the gate which is depletion for p-si.) For Metal/Oxide/Si this ensures that you do not go into deep depletion. (the min and max C values are used for calculations). c. The software will check the Vstep direction and applies Vstart and Vstop to see if C(measured) increases. If not, you will get a message wrong voltage direction, Do you want to continue or change? d. Select [Save this Recipe] after entering the required information. If the recipe is preexisting, you will get a prompt asking PSWP already exists. Do you want to replace it? [Yes] or [No] ; If yes you will return to the [MOS Function Page] (Fig. 10). Page 8

Fig. 10. MOS Function Page Fig. 11. MOS Connect Options e. Select [Start Test] on the [MOS Function] page; prompt asks [OK] to use the last one; [Cancel] to request a different recipe. f.

An Option on this page is to Zero Capacitance Meter if you have not already done so. h. Select [Connect], Prompt says connect sample ; connect and enter [OK]. i. Select [Connect] j.

10 Fig. 10. MOS Function Page Fig. 11. MOS Connect Options e. Select [Start Test] on the [MOS Function] page; prompt asks [OK] to use the last one; [Cancel] to request a different recipe. f. The next prompt allows you to enter Sample Number and Remarks ; Then, choices are to Measure or Abort ; Select [Measure], returns to [MOS Connect Options] (Fig. 11). g. An Option on this page is to Zero Capacitance Meter if you have not already done so. h. Select [Connect], Prompt says connect sample ; connect and enter [OK]. i. Select [Connect] j. Run test (Starts with direction test and applies Vstart, Vstop); if OK, test continues; Otherwise, prompt Incorrect sweep direction [OK] to reverse or [Ignore] to keep. k. Prompt: Light control is manual; Open box (or turn on light); leave for 5-10 sec with Si, Close box (turn off light). l. Test window [Data Gathering] opens, Vstart is applied and then C stabilization starts, measured C and V are displayed (along with a progress bar), this repeats until voltage reaches Vstop. m. When the test completes, the [MOS Function] page returns with options to [Analyze data] and [Save Data], see Fig. 12. NOTE: for some films, the initial voltage direction test will stress the sample and/or move charge around; if this is a problem, there are possible work-arounds. NOTE: on 4184A, the display Voltage is the gate voltage (top electrode) while in the software, V substrate is shown on the screen and in the data files. If you want to use the gate voltage, you will need to multiply data voltages by -1. Page 9

Select graph; using windows command Replot allows re-scaling Xmin, Xmax, Ymin, Ymax, or using default limits or changing to normalized values (C/Cox).

11 Fig. 12. MOS Function page Fig. 13. MOS Analysis Page C. Data Analysis Select [Analyze Data] and [MOS Analysis] page opens; options are listed (Fig. 13). Select [Capacitance-Voltage Plot] and the CV plot opens in a separate window. Select [Conductance-Voltage Plot] and the corresponding GV plot opens in another window. Select graph; using windows command Replot allows re-scaling Xmin, Xmax, Ymin, Ymax, or using default limits or changing to normalized values (C/Cox). Next, select a graph such as CV plot window ; Windows commands include Output. Under the Output pull-down are the following: This Graph (copies the graph to clipboard) Entire screen (copies graph + tabulated data to clipboard; then it paste into Word, see Fig. 18) List points (to) Screen Printer (NA) File (.txt) Excel (this is the easiest way to export the data) Printer setup (no printer is available) For example, Select Excel, Next, Enter File Name, Folder location (if new user, enter folder name (such as your name) hit save, Data in an Excel spreadsheet goes to this location: My Computer >> Local disc C >> CSM >> Data >> (your folder name). Excel Files can be transferred to another computer using a memory stick. Note: this saves the C-V and G-V values, but not the computed results such as Vfb, Vth, Nss. D. Options for CV testing There are a number of options for testing; a few are described below. 1. Select [Variable Frequency Tests] from the [Main Menu] page. 2. [Conductance-Frequency Mode] Page (Fig. 14) has three options. Page 10

Fig. 14. Variable Frequency Test Page Fig. 15.

One option is [Sweep at One Voltage]; see [Conductance-Frequency-Test Recipe] (Fig.15).

thickness, Save this recipe, (XXX.mdc). 4.

12 Fig. 14. Variable Frequency Test Page Fig. 15. Conductance-Frequency Test Recipe Sweep frequency at one voltage (Fig. 15) 3. One option is [Sweep at One Voltage]; see [Conductance-Frequency-Test Recipe] (Fig.15). Enter the start & stop frequencies, Test voltage (on Substrate), Known substrate V in accumulation, Tox thickness, Save this recipe, (XXX.mdc). 4. Another option is to select C(F,V) or G(F,V); see test recipe (Fig16); Enter variables. This will Measure C (and G) versus V at each frequency. Set up page for variable frequency (Hertz), Voltage range, Tox, V in accumulation. Save this recipe Start test Fig. 16. Variable Voltage C-F or G-F Test Recipe Page 11

13 5. [C-T Tests for Lifetime] option (Fig 17) is available from the [MOS-Mode] page. Required data is as follows: Enter Test time (duration), V before step, After step, Vin Accumulation, Tox [Save this recipe] Fig. 17. Lifetime test recipe page From the [Main Menu] page, other possibilities include the following: [Manual Mode] allows you to apply a voltage and get the corresponding capacitance. [TVS test] applies a triangular test voltage sweep and assumes variable temperature capabilities. More details are in the on screen help. This test was designed to evaluate mobile charge in reasonably thick dielectrics (see Schroder s book). This will not work since there is no variable temperature available. [Current Voltage Tests] generate IV data using the HP 4140B pa meter. See manual for details. Generally, IV measurements are much easier on the HT probe stage with the Agilent 4155A. Finished? Save your data and any test programs; close the software. Copy your data onto a memory stick. Log off the computer. Page 12

8. Process Data From the data analysis screen, a typical MOS CV for a thermal oxide on p-type Si is generated and shown in Fig. 18. Expand the plot to full screen.

14 8. Process Data From the data analysis screen, a typical MOS CV for a thermal oxide on p-type Si is generated and shown in Fig. 18. Expand the plot to full screen. Save this screen; to clipboard; paste to WORD. Note the voltage is the substrate voltage! The input parameters are the area and frequency; measured parameters are Cox, Cinv; calculated parameters include Tox, Winv, Cfb/Cox, Vfb, Vt, Nss, and φms. Figure 18. Output Entire screen with CV plot and tabulated values. Page 13

15 C (pf) G (us) Arizona State University NanoFab Al2O3 Piranha last, Retrace CGVs Vg= +3 to -3 to Voltage C(pF) R3E Pir G (us) R3E Hpir Fig. 19. ALD Al2O3 retrace CV (blue) and GV (red) plots showing large V-shifts. First CV starts at +3V to -3V; the retrace goes from -3V to +3V. Figure 19 shows an example of a retrace mode ; arrows indicate the sweep direction. Figures 20 shows an example of CV data using the hysteresis mode. Voltages for this test start at 0, step to +5V; return to 0; then V steps from 0 to -5V; and returns to 0. Note that the first sweep from 0 to +5 goes into deep depletion. Detailed data analysis information is available in the following references: MOS (Metal Oxide Semiconductor) Physics and Technology, E. H. Nicollian & J. R. Brews, is the classic reference for MOS CV measurements and analysis. Semiconductor Material and Device Characterization, Dieter K. Schroder, Chapter 6.. ASTM F , Standard Test Method for Characterization of Metal-Oxide-Silicon (MOS) Structures by Capacitance-Voltage Measurements (1988), shows the analysis of CV data. Agilent Impedance Measurement Handbook, 4 th edition, explains the details of impedance measurements. Page 14

16 Capacitance (pf) Arizona State University NanoFab 160 SiO2 (900A) on p-silicon Hystersis Mode CV Voltage C1 (pf) HY C2 (pf) HY C3 (pf) HY C4 (pf) HY Fig. 20. Hysteresis CV with p-si; deep depletion for 1 st sweep 0 to +5V (blue); 5V to 0V (Red); Hysteresis CV plot with p-si in accumulation. 0 to +5V (green); +5V to 0V (purple). Page 15

17 9. Revision History Effective Date Originator DESCRIPTION OF REVISION Issue 1/3/2006 P Boland Operating instructions A 6/30/15 W Paulson Change to new SOP format and RT only CV s B C D E F G H Page 16

HIGH TEMPERATURE PROBE STATION STANDARD OPERATION PROCEDURE

Arizona State University NanoFab HIGH TEMPERATURE PROBE STATION STANDARD OPERATION PROCEDURE Rev A Table of Contents Contents Table of Contents... 1 1. Purpose / Scope... 2 2. Reference Documents... 2