HIGH TEMPERATURE PROBE STATION STANDARD OPERATION PROCEDURE

Transcription

1 Arizona State University NanoFab HIGH TEMPERATURE PROBE STATION STANDARD OPERATION PROCEDURE Rev A

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

3 1. Purpose / Scope This SOP provides the operating instructions for the High Temperature Probe Station. This includes the mechanical probe station details, the micromanipulators, electrical connections, measurements (IV s with Agilent 4155B or CV s with HP4284), software control of the switch matrix (ICV Lite) and software to automate measurements(ics). 2. Reference Documents Agilent 4155C Users Guide V1.pdf Agilent 5146C V2, Agilent 4155C Screen setup ref Agilent 4284A CV Manual Agilent Impedance Measurement Handbook Dieter K. Schroeder, Semiconductor Material and Device Characterization 3. Equipment / Supplies / Material Micromanipulator Probe Station with Video monitor Micromanipulator, Model 525 Probe holder and tungsten probe tips Thermal Chuck with Temperature controller Agilent 4155C for IV measurements HP 4284A for CV measurements Agilent 41501B Pulse Generator HP E5250A Switch Matrix PC with software to control Measurements PC for data storage 4. Safety The main safety concern is when the probe chuck is hot ( C); do not touch samples or chuck or any surrounding fixtures. 5. Set Up Procedures The setup procedures are organized into the following topics: Mechanical, Micromanipulators, Connections, Software Instrument Control A. Mechanical Probe Station Controls 1. The probe station is inside a light-tight, shielded metal box with lid. 2. X & Y stage controls are on the left and right sides. 3. Z control of the probe ring in on the front side; note that it lifts the ring, not the stage. 4. Micromanipulators are positioned around the probe ring. 5. Microscope with video camera provide sample view on monitor; focusing knobs are behind the microscope. 6. Microscope light & zoom controls are on the black box; front-right side of enclosure. Light source is below the probe box with ON/OFF switch and fiber optics to microscope. 7. Traveling microscope X & Y controls are at the back, right side. Page 2

4 8. Triax connections to the measuring equipment are on the back right side of the probe box and labeled SMU1, SMU2, SMU3, SMU4 (front to back). Connection to the chuck is on the bottom right side. 9. Note the strain relief connectors on both the left and right side of the probe station; the top 2 feed-through connectors are triax and the bottom 3 are co-ax connectors; IMPORTANT: Do not mixup triax and co-ax connectors; All the probe stage wiring uses triax connectors. 10. Triax to coax connectors are required for the direct connection to the cap bridge. 11. Vacuum control is the switch, front, left side; holds sample in place. 12. Emergency shut off is the red button on the front side. B. Micromanipulators 1. The MM micromanipulators have a vacuum hold down; vacuum switch is on the side of the base; push and hold to release and re-position; release to hold. 2. Micromanipulators have X, Y and Z controls on the backside; a coarse Z control is on the front of the manipulators; note the triax wire is connected to the probe holder. 3. The triax connector from the manipulator goes to the triax feedthrough connector on the back-left or back-right side of the stage; NOTE: the top 2 feedthrough connectors on both sides are triax, the bottom 3 are co-ax connectors on both sides; All wiring in the station uses triax wires and connectors; DO NOT MIX! 4. At the tip of the holder is the probe needle. Standard needles are ~20 mil diameter tungsten wires with sharp needles on one end. The probe holder has an angled hole for the needle; a set-screw in the end of the holder clamps the needle in place. Please do not bend the needles! 5. Needle heights are set for most wafer samples, but can be adjusted if needed. To change, contact CSSER staff 6. If the needles are damaged, contact CSSER staff for replacement. 7. The needles often pick up material from probe pads and can generate contact problems for subsequent probing. To clean the needles, use a swab with a little IPA and gently clean the needle tips; inspect using the microscope. 8. In order to position the probe needles, follow this sequence; a. Lower the needle to just above the sample using the coarse Z control. b. Release the vacuum control and slide the manipulator until needle is visible in the microscope. c. Use the standard X, Y and Z controls to position the needle above the probe pad. d. Slowly lower the needle until it makes contact (at contact, needle moves horizontally) e. Follow the above steps to connect other manipulator needles to probe pads. f. If the next pad is outside the microscope view, use the traveling microscope to locate the next probe pad. 9. When you finish probing, lift the needle(s) from your sample using the Z and coarse-z controls; release the vacuum; rotate the manipulator to the back of the stage; Turn off the vacuum; remove your sample. 10. Turn off the microscope light and the monitor; close the lid. Page 3

5 C. Connections 1. The triax connectors from the manipulators goes to the Strain Relief triax feedthrough connectors on the left or right side of the probe station. Triax wires (white) connect the backside of these connectors to the corresponding feedthroughs on the wall of the probe box. 2. Ensure that each micromanipulator is connected to the corresponding SMU feedthrough; NOTE: they are labeled (from front to back) SMU1, SMU2, SMU3, SMU4. 3. If you are using a connection to the back side of the wafer, ensure a connection between the chuck connector on the back, bottom of the probe station and the appropriate SMU. D. Software Instrument Control 1. ICV-Lite software controls the switch matrix. This allows you to choose between the Agilent 4155C and HP 4284A measurement systems. 2. Log into the computer using your ISSAC ID and password; contact nanofab staff for computer access. 3. Open the ICV-Lite software; Use the pull-down menus; Select Development a. Select Device Connections Editor b. Choose 4155C (for IV s) or 4284A (for CV s) c. Select Edit ; Switch matrix schematic appears; Inputs are the first column; outputs are across the top row (connections to the probe box feedthroughs). O U T P U T S I 1 o N 2 o P 3 o U 4 o T 5 S Default connections for the Agilent 4255C. Page 4

6 O U T P U T S I 1 N 2 P 3 U 4 T 5 S o 10 o Default connections for the 4284A Note that Hi Pot & Hi I are connected to #9. Low Pot & Low I to #10 d. Select Make Connections Now e. Select Finish 4. This completed the section on selecting the measurement tool. You can close out the software and continue with your measurements. 6. Operation Procedures The operation procedures are divided into the following sections: IV Measurements, CV Measurements, Temperature Control, Software Measurement Control. A. IV Measurements This probe station uses an Agilent 4155C for IV measurements; Current range is from sub-pa to 100 ma; there are both voltage and power limitations. The 4155C has 4 independent power supplies [SMU1, SMU2, SMU3, SMU4] that will be connected to the corresponding 4 connectors on the probe box (back right side). 1. Place your sample on the probe stage; turn on the video monitor and light; Find correct probe pads and position micromanipulator needles (see section B ); note corresponding SMU 2. Agilent 4255C Front Panel Operation (refer to photo). Note the following blocks: a. Display on the left side with 7 vertical soft keys and 8 horizontal soft keys. Soft key functions change with screen. b. Page control block; just to the right side of the display. The 4 gray keys in a column allow one to set up and measure devices; start with the top key [Chan], then [Meas] then [Display] and then [Graph/List]. c. Knob to read out data points and arrow keys to move around screens. d. Measurement Block (right top); 6 keys; i. top row [Single, Repeat, Standby]; ii. bottom row [stop, Append, Stress(yellow)] e. Integration time keys; [Short, Medium, Long]: short tends to be noisy, medium is usually good, long yields the best resolution, but is slower] Page 5

7 f. Entry Block; Edit keys on left, Key pad with numbers or alphabet, Far right [Enter key], [blue key] for alphabet, [green key] for special characters. Note right column next to key board with suffix keys (m=milli, u=micro, n=nano, p=pico, f=femto). g. Ibasic programming keys (generally not used any more) h. File keys for saved programs. (generally not used any more) 3. Short Version of front panel measurement setup The following is a very brief description to set up and measure a 2-terminal device. a. Find the page control block with 4 gray keys in a column. b. Start with the top key [CHAN]; use soft keys (right side); Mode box [sweep]; choose best device representation for your sample [MOSFET], [Bipolar], [Diode]. c. Select [MEAS]; enter Start, Stop, Step voltages and Compliance current. d. Select [Display] key; enter graph X-axis Min, Max & Y-axis Min, Max, Linear or log scales. e. Select [Graph]; the blank graph is displayed. f. Select [Medium] integration time in the measurement bock. g. Select [Single] in the measurement block; measurement starts; green light is on; results show in graph; save your data. Page 6

8 Agilent 4155C photo of the front panel. For this 2-terminal example, connect your device to micromanipulators wired to SMU1 and SMU3. 4. Detailed Front panel measurement setup: Details steps and corresponding screen views a. Select [Chan] key in the Page control block; in the display move curser to Mode box; Soft keys (right side) include SWEEP, SAMPLING, QSCV plus Defaults, Bipolar, FET Vd-Id, (more ½), FET Vgs-Id, and Diode VF-IF, (more 2/2); Choose best fit for your device. For example, Select [Sweep] and then [Diode] for any 2 terminal measurement. Display: Unit Vname Iname Mode Func SMU1 VF IF V VAR1 SMU2 SMU3 V I Common Const SMU4 Page 7

9 b. Select [MEAS], the 2nd gray key, in the Page control Block; Use arrows to move around screen; Use soft key selections and/or key-in values and hit [Enter] key (on right side of entry block). Display: VAR1 VAR2 UNIT SMU1 NAME VF Sweep Mode Single Lin/Log Linear Start 0 Stop 10V Step 0.1 No of steps 101 Compliance 10mA Power Comp off c. Arrow to a box labeled Sweep*, located in the lower right of the screen; Soft key options for compliance: 1. Cont at any 2. Stop at any abnormality 3. Stop at compliance Choose #3, stop at Compliance. (Turns power off if current exceeds value [10mA for this example]). d. Select [Display], the 3 rd gray key, in the page control block. This page sets the plot limits; Xmin, Xmax, Ymin, Ymax as well as liner or log scales Display: X axis Y axis Y2 axis Name VF IF Scale Linear Linear Min 0 0 Max 10 10m Arrow around the screen, pick the names and scale (linear or log) using the softkeys. Key in values for Min and Max, use suffix keys if needed, & hit [enter] key. For example, in the Max for Y axis, key in 10, hit the m key, and [enter] to get 10mA. Note: Log works for all positive or all negative values, but not for mixed positive and negative values. e. Select [Graph/LIST], the 4 th gray key, in the page control block. The graph will be displayed according to the above limits; you can always re-scale or autoscale later. Page 8

10 f. Measure Now, find the Measurement Block and its 6 keys (Top right): Single Repeat Standby Stop Append Stress Below these keys are the integration time keys: Short Medium Long Centered at the top of the display graph is the integration time; default is short ; However, [Medium] is a generally a better starting choice. Now, Select [Single] in the measurement block; Measurement starts; Voltage steps and current is measured; Hit [Stop] if any problems! Green light is on. Results are plotted as data is taken; Green light goes out when finished. Note: select Soft key below the graph: [Marker] Note: select soft key on Right side, [Marker on]; Turn dial to read measurement values; they are displayed above the graph. Note: Repeat erases the 1 st data set and re-measures the device, and continues until [stop]. Note: [Append] keeps the 1 st data set and re-measures the device; both data sets show on graph. g. Save the data! You can save the data to either a 3.5 floppy drive or to a Windows XP computer. Upon 4255C power up, the default drive is Floppy. Ensure that the windows XP computer is turned on 1. To change the drive: 2. Select [System] Key; Select [Filer] softkey; Arrow to field at the top *DISK [PC] and select PC from soft keys on the right (or else select the default FLOPPY). 3. After completing measurement, toggle the [Graph/List] key to LIST. 4. Select softkey [SPREAD SHEET]; Displays ASCII SAVE setup screen. a. The box at the top *DISK [ ] should read *DISK [PC] or *[FLOPPY] 5. Arrow to Name box; Key in file name [FileName]; hit ENTER key (on far right side). a. <= 8 characters for floppy disc files b. <= 36 characters for network files 6. The rest of the fields should be automatically filled in with default values: a. Output Data Boxes from [ 1 ] to [max] b. Unit [OFF] c. Delimiter [Space] d. String Mark [NONE] 7. Select softkey [EXECUTE], bottom left. 8. After files are written, select softkey on the right [EXIT] 9. Select [Graph/List] to return to graph and/or more measurements. Excel can read the text files to import data into a spreadsheet (use comma & space delimiters). Find a computer with a 3.5 drive for the file transfer; save on a USB memory stick. The PC for data storage has a 3.5 drive (see above) Page 9

11 10. Find your files on the PC: Go to the Windows XP computer; turn on if needed; Allow ~5 min for computer to boot up. Go to My Computer ; Open Drive labeled D:\Agilent 4155C (shortcut on Desktop) Saved files should be in this folder as filename.txt files. Move files onto your thumb drive and onto your own computer. EXCEL will open the text files; use TAB and SPACE for delimiters. Test conditions are at the top of the file followed by the data; Appended data follows the initial values. IMPORTANT: Delete your files from the common area D:\Agilent 4155C when finished. 5. Re-assigning SMU s One more useful and helpful option is the following: This shortcut saves moving connectors or micromanipulators. Assume a 2-terminal measurement with micromanipulators connected to SMU2 and SMU4. Select [Chan] key; in the display move curser to Mode box; select [Sweep]. Soft key choices (right side) include MOSFET, Bipolar, Diode, ; Select [diode] for any 2 terminal measurement. Display is as below. Display: Unit Vname Iname Mode Func SMU1 VF IF V VAR1 SMU2 SMU3 V I Common Const SMU4 Use arrow keys to go to first Vname entry [VF]. Now, select soft key on the right column labeled [channel assign]; Curser moves to SMU1 box; soft keys are now labeled [SMU1], [SMU2], [SMU3] and [SMU4]. For this example, re-assign the VF row to SMU2 using the softkey; Curser moves down one row; re-assign SMU2 to SMU1, since it is not used for this example. Curser moves to SMU3 row; re-assign SMU3 to SMU4 using the softkey; Again, since SMU4 is not in use, re-assign to SMU3. Important! use softkey [exit channel assignment]; display now reads: Display: Unit Vname Iname Mode Func SMU1 SMU2 VF IF V VAR1 SMU3 SMU4 V I Common Const Now, continue through the next 3 page control keys and set up the measurement range & display. Page 10

12 B. CV measurements We will review the front panel of the 4284A Impedance Bridge and the many options and then illustrate a simple CV measurement. This bridge measures impedance (Z) and phase angle (θ) and then calculates the equivalent parameters such as parallel Cp with parallel G (conductance). 1. Use the ICV Lite software to connect the High and Low bridge terminals to 2 of the SMU connectors (see section D. Software Instrument Control). 2. The 4284A has a display with 5 soft keys on the right. Choose fields using the Arrow keys; key in values with the number pad and the Enter key. At the top center are 3 keys: Display Format, Meas Setup, Catalog/system. 3. Select Measurement Setup key; Arrow to Function; soft key choices are below; See the Agilent Impedance Measurement Handbook for definitions of terms Function Cp-D Cs-D Lp-D Ls-D R-X G-B Cp-Q Cs-Q Lp-Q Ls-Q Z-O(deg) Y-O(deg) Cp-G Cs-G Lp-G Ls-G Z-O(rad) Y-O(rad) Cp-Rp Lp-Rp More 1/6 More 2/6 More 3/6 More 4/6 More 5/6 More 6/6 Similarly, arrow to FREQ and select frequency with soft keys; note the top and bottom keys move in decade steps, the smaller arrows move in smaller frequency steps. For example, if you start at 10KHz, the top key will shift to 100KHz and the bottom key to 1KHz; the smaller arrows allow the following frequencies:[10k, 12K, 15K, 20K, 25K, 30K, 40K, 50K, 60K, 80K, 100K]; similar intermediate values are available starting at 1K, 10K, 100K. Next arrow to LEVEL and set the ac voltage; typical values are 25 mv to 50 mv. Arrow to Bias field and enter a DC voltage on the number pad, followed by the enter key; turn on DC voltage with the key (bottom center); red light should turn on. Arrow around the screen and fill in other fields as needed. 4. Connect your sample using the correct micromanipular(s) and/or substrate connection. Do you get a good capacitance reading? Do you see the expected change in C with ±DC voltages? See software section if you want to automate the CV measurements. Page 11

13 C. Temperature controls The chuck temperature is controlled by the large unit to the left of the probe station. For high temperatures (25C<T<300C) above room temperature, there is a heater in the chuck. For low temperatures, a refrigerant is circulated through the chuck. 1. The control panel is on the left side of the temperature control unit. 2. The main power switch is at the bottom center of the panel; to operate, turn on. 3. The top temperature control box is for temperatures above RT. 4. Set the desired temperature using the dials and red readout screen. 5. The current temperature is the green reading. 6. Turn on the power switch for the heater. Wait! System checks conditions before turning on the heater. 7. Chuck temperature will slowly increase to the setpoint. 8. Temperature will arrive at the setpoint and generally oscillates a couple of degrees around the setpoint. Now, run your measurement and collect data. Set a new temperature and repeat. When finished turn the heater off; chuck begins to cool. Cooling rates are slow so you can often collect measurements within a very short time, relative to the cooling rates. 9. For temperatures below RT, there are two set points that need to be controlled. 10. First, set the refrigerant temperature using the setpoint arrow keys; turn on the refrigeration unit. IMPORTANT; this temperature must be below the desired target temperature. 11. Second, set the target temperature on the second temperature control box; turn on cool. 12. If you plan to go very far below room temperature, you will need to place the extra shields above your sample. This setup will prevent moisture from condensing on your sample. Put the shields in place; note the side openings for the micromanipulators. Position the probe needles on your sample. 13. Next, turn on the N2 gas on the back wall and adjust the flow meter. Purging the chamber of water vapor is a slow process. When finished, turn off the N2 gas on the back wall. 14. Measure your sample; the chuck temperature changes are slow. 15. Remove shields etc when finished. Turn off the heater or cooling control unit; turn off the main power switch. Page 12

14 D. Software control of measurements ICS software allows the programming of measurement conditions and data collection and saving both the program and data. A short overview of the software follows 1. Log in to the computer and open the software ICS 2. On the screen are icons and at the top are the typical windows pull down menus. 3. Use the icons and start on the left and continue to the right. 4. Instrument: select either the 4155 or the 4284 and select connect. 5. New: enter a name for your program; select OK; this will become the file name. 6. Device: select the schematic for your device from the menu; schematic shows up with small adjacent boxes for each connection point. 7. Source units: Power supplies are listed, SMU1, SMU2, SMU3, SMU4; highlight the desired power supply, click on the corresponding square on the schematic; continue with other SMU s. 8. Double click on SMU; resulting screen is similar to the front panel; you will need to fill in all the measurement conditions and select the data (V, I) to be measured. 9. Options: select this key and set up the compliance and integration time. 10. MEAS key; opens the measurement controls: single, append, stop, auto seq. Selecting the single key starts the measurement. 11. AUTO Sequence: you can generate several programs and chain them together in an auto sequence. 12. Measure you sample: select single, results are placed in a spreadsheet ; select the spreadsheet key and select the data for each column. 13. Select Graph: This generates a graph of the data in the spreadsheet; auto scales the data. The graph button allows changes to all graph paramters. 14. Save to EXCEL: open Excel in the background, select the columns of data (shift, select); Go to Edit menu and select COPY (note that Ctrl C does not work!); open Excel, paste data into Excel (note that Ctrl V does work!), save your data! 7. Process Data Frequently, the measured data is exported to Excel. Calculations and graphs can be generated within Excel. For example, if you measure both forward and reverse currents for a diode, you can plot the log[abs(i)] versus V. This allows you to plot a wide range of currents with both positive & negative values. Page 13

15 8. Revision History Effective Date Originator DESCRIPTION OF REVISION Issue 7/13/2016 Wayne Paulson Initial Release A B C D E F G H Page 14