Agilent Technologies B1500A Training Manual
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Agilent Technologies B1500A Training Manual

Semiconductor device analyzer
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Agilent B1500A
Semiconductor Device
Analyzer
Self-paced Training Manual, 3
Agilent Technologies

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  • Page 1 Agilent B1500A Semiconductor Device Analyzer Self-paced Training Manual, 3 Agilent Technologies...
  • Page 2 Notices © Agilent Technologies 2005 - 2008 Manual Part Number ware” as defined in DFAR 252.227-7014 (June 1995), or as a “commercial item” as No part of this manual may be reproduced B1500-90042 defined in FAR 2.101(a) or as “Restricted in any form or by any means (including computer software”...
  • Page 4 EasyEXPERT. You will learn about what is the B1500A. • Module 2. Getting Started This module explains the basic operations of the B1500A. You will learn about how to launch B1500A/EasyEXPERT and how to perform application test and quick test. •...
  • Page 5 This module explains the SPGU Control classic test. You will learn how to create the classic test setup and the applications using SPGU in the course exercises. EasyEXPERT is a trademark of Agilent Technologies. All other trademarks are the property of their respective owners.
  • Page 6 Class Exercises Class exercises use the test setup listed below. The test setup data are only examples and included in the Demo.xpg file stored in the Manual CD-ROM. Module Exercise Device Test setup/definition/data Page Module 1 no exercise Module 2 Id-Vd measurement MOSFET CMOS: Id-Vd...
  • Page 7 Demo.xpg file Demo.xpg file is required to create the Demo preset group which contains the test setup data used by the class exercises. And it is stored in the \data folder on the Agilent B1500A Manual CD-ROM, Edition 4 or later.
  • Page 8 Test Setup for Class Exercises The Demo preset group contains the following test setup. The setup data are only examples for the class exercises. The following table lists the test setup name in alphabetical order. Test Setup Name Description ALWG monitor 511 kohm sampling measurement with SPGU ALWG output Charge Pumping 4T MOSFET Icp-Vbase measurement...
  • Page 9 Test Setup Name Description Trng List MOSFET Vth-gmmax measurement using I/V List Sweep Trng Multi Multi Channel I/V Sweep (Bipolar transistor and LED) 0.1 μF sampling measurement Trng Sampling Trng Switch B2200/E5250 switch setup, Input 1-3-5-7 to Output 1-3-5-7 Zero-check SMU open measurement Zero-check-ASU SMU open measurement with ASU...
  • Page 10 Required Devices for Class Exercises To perform the class exercises, you need the device set (Agilent part number 04156-87001) which contains the following devices. Description Quantity N-channel MOSFET 2 ea. NPN Bipolar Transistor 1 ea. Red Miniature LED 1 ea. 0.1 μF Capacitor 50 V 1 ea.
  • Page 11 Required Accessories for Class Exercises To perform the class exercises, you need the following accessories. Prepare the accessories shown below. Designation Description Model No. Qty. Test Fixture 1 ea. 16442A/B 28 pin socket module 1 ea. Connection wire 6 ea. Triaxial Cable 16494A 4 ea.
  • Page 12 To perform the flash memory class exercise in Module 13 and if you use the ASU, you need the following accessories. Description Model No. Qty. ASU (Atto Sense/Switch Unit) with control cable E5288A Total 3sets Triaxial Cable 16494A or Total equivalent 7ea.
  • Page 13 • • SMU/Pulse Generator Selector • B2200/E5250 Switch Control • Desktop EasyEXPERT Module 2. Getting Started • To Turn on/off B1500A • To Launch EasyEXPERT • To Specify/Create Workspace • To Perform Application Test • To Save/Recall Your Test Setup •...
  • Page 14 Contents Module 3. Data Display and Management • Data Display window • Graph Analysis Tools • Data Status • To Change Graph/List/Display Setup • To See Print Preview • To Print Display Data • To Copy Graph Plot/List Data • To Save Analysis Result •...

  • Page 15: Table Of Contents

    Contents Module 5. Basic Measurement • SMU Fundamentals • Classic Test Environment • SMUs Connected in Series or Parallel • Cabling and Fixture Issues • Kelvin and Driven Guard • Probes and Prober Connections • Triax and Coax Adapters • Safety Interlock Issues Module 6.
  • Page 16 Contents Module 7. Measurement Functions • SMU Pulsed Sweep Measurement • I/V-t Sampling Measurement • Negative Hold Time for High Speed Sampling • Auto Analysis • SMU Filter • SMU Series Resistor • Standby Function • Bias Hold Function Module 8. Capacitance Measurement •...
  • Page 17 Contents Module 9. Modifying Application Test Definitions • To Open Application Test Definition • To Modify Test Definition • To Use Debug Tools • To Use Built-in Functions • To Add Data Display • To Use Auto Analysis • To Use Test Setup Internal Variables Module 10.
  • Page 18 Contents Module 11. Advanced Definitions and Operations • To Control External GPIB Devices • To Call Execution Files • To Perform Repeat Measurements • Prober Control Script Module 12. Miscellaneous Operations • Function Status Indicator • Run Option • Automatic Data Export and Data Record •...
  • Page 19 Contents Module 13. SPGU Control and Applications • High Voltage SPGU • SPGU Control • Pulse Generator Mode • Charge Pumping • Flash Memory Test • ALWG Mode Contents-7...
  • Page 21 Basic Measurement...

  • Page 22: Smu Fundamentals

    Module 5 Basic Measurement In This Module • SMU Fundamentals • Classic Test Environment • SMUs Connected in Series or Parallel • Cabling and Fixture Issues • Kelvin and Driven Guard • Probes and Prober Connections • Triax and Coax Adapters •...
  • Page 23 - Current source while monitoring voltage - Source common with no monitor The SMUs on the B1500A can output V or I in constant, linear sweep, logarithmic sweep or pulsed modes. Constant V or I mode could be used for “spot” measurements or biases.
  • Page 24 Module 5 Basic Measurement Basic Sweep Measurement VAR1 Single Sweep Double Sweep Linear Sweep Log Sweep The SMUs can now sweep up to a value and then back down (double sweep). This feature is useful when the device must be tested without abruptly removing the forcing condition. Log sweeps are required any time the measurement results span many decades, such as a MOS subthreshold curve.
  • Page 25 Module 5 Basic Measurement Sweep Measurement Modes Combining VAR1, VAR1’, VAR2 VAR1 (primary sweep) Subordinate sweep VAR2 (secondary sweep) VAR1 (primary sweep) Synchronous sweep VAR1’ (synchronous sweep) A subordinate sweep variable (VAR2) may be combined with the basic sweep variable (VAR1). This corresponds to the step knob and sweep knob of a curve tracer.
  • Page 26 Module 5 Basic Measurement Why Four SMUs? Four terminal MOS device Only one configuration required Speed up testing Drain Gate Substrate Source VAR1 VAR2 Common Constant SMU3 SMU1 SMU2 SMU4 The basic semiconductor device is the 4-terminal MOS transistor. By assigning an SMU to each terminal, you have complete flexibility to make any measurement without having to change the device hookup.
  • Page 27 Module 5 Basic Measurement Class Exercise MOS Id vs Vd Basic Measurement You will connect the SMU cables and jumper leads You will then "properly" insert the MOS transistor You will learn how to load a setup data Observe Classic Test setup screen Click button to make a new measurement Observe Application Test setup screen...
  • Page 28 Connect corresponding numbers. On the 16442A/B fixture use the numbers labeled 1 - 6, not 1 - 3. Your B1500A may not match the SMU configuration shown in this figure. Note that SMU1 is the module top of the GNDU (ground unit). The SMU number become large from bottom to top as shown.
  • Page 29 GNDU Curves clamped at 10 mA level B1500A Rear View This picture shows the triax cables connected to the right set of connectors which is wrong. The 4 triax cables must be connected to the left set of connectors (FORCE).
  • Page 30 Module 5 Basic Measurement Jumper Leads – MOS transistor GNDU 1: Substrate 2: Source 3: Gate 4: Drain For all class exercises, you need the 28-pin dual in line socket which comes standard with the 4145 fixture (16058A) or the newer fixture (16442A/B). Either fixture works fine. With the 16442A/B fixture, note that there are two SMU numbering schemes..3 SMUs with force and sense, or six SMUs with force only.
  • Page 31 5. Import \data\Demo.xpg on the Manual CD-ROM The Agilent B1500A Manual CD-ROM stores demo data used for performing this class exercise. Insert the CD-ROM and import the demo data to the EasyEXPERT database. The demo.xpg file contains the test setup data used in this class exercise.
  • Page 32 Module 5 Basic Measurement To Get Setup Data To Get Classic Test Setup: 1. Highlight IDVD in My Favorite Setup 2. Click Recall button To Get Application Test Setup: 1. Highlight Id-Vd in My Favorite Setup 2. Click Recall button You can get the test setup data as shown.
  • Page 33 Module 5 Basic Measurement Classic Test – Channel Setup After you get the IDVD setup data, you will see the Classic Test setup screen as shown. The Channel Setup screen allows the user to assign a meaningful name to the force/meas functions of each SMU.
  • Page 34 Module 5 Basic Measurement Classic Test – Measurement Setup Do not abort on compliance, oscillation, etc. The Measurement Setup screen is shown here. The variables VAR1 and VAR2 define the sweep parameters. In a case where two sweep parameters are defined, the second parameter (VAR2) is called the subordinate (secondary) sweep parameter.
  • Page 35 Module 5 Basic Measurement Classic Test – Display Setup The Display Setup screen allows you to set the X-Y graph axes. The display setup is divorced from the measurement setup to allow the user to tailor the view to a particular region of interest. This screen also allows you to set data variable names to be displayed in the List Display and Parameters areas on the Data Display window which is opened when the measurement is started.
  • Page 36 Module 5 Basic Measurement To Start Measurement 1. Click Single button This opens the Data Display window and starts measurement. The Data Display window shows measurement result data graph/list. 5-16...
  • Page 37 Module 5 Basic Measurement Data Display Window – Graph Analysis tools Graph Plot Parameters Auto Scale List Display This window displays measurement result graph, list, and parameter values. Markers are used to traverse the actual measurement data. Markers cannot be placed anywhere on the screen except on an actual measurement trace.
  • Page 38 Module 5 Basic Measurement Data Display Window - List Analysis tools Graph Plot Parameters Marker position List Display The List Display corresponds exactly with the Graph Plot. Even the highlighted line of data corresponds to the marker position on the Graph Plot. Up to twenty columns of data can be set on the List Display.
  • Page 39 Module 5 Basic Measurement To Copy List Data Paste to Notepad Open by a spreadsheet software 5-19...

  • Page 40: Application Test

    Module 5 Basic Measurement Application Test Recall Id-Vd application test setup data. After you get the Id-Vd setup data, you will see the Application Test setup screen as shown. Test Parameters area shows the device connection information and allows the user to set the SMU outputs.
  • Page 41 Module 5 Basic Measurement Application Test – Extended Setup Clicking the Extended Setup button opens … The Extended Setup dialog box allows the user to set the additional test setup parameters. In the Id- Vd setup, the additional parameters are source voltage, maximum gate current, maximum substrate current, integration time, hold time, and delay time.
  • Page 42 Module 5 Basic Measurement SMUs May Be Connected In Series or Parallel To Double the Output Voltage from 100 V to 200 V for HRSMU and MPSMU from 200 V to 400 V for HPSMU To Double the Output Current from 100 mA to 200 mA for HRSMU and MPSMU from 1 A to 2 A for HPSMU Use the VAR1’...
  • Page 43 Module 5 Basic Measurement 200 Volt Sweep (400 Volt with 2 HPSMUs) Two SMUs in Series WARNING Base current = 0 or leave open Collector Base Emitter Const. VAR1' VAR1 VAR1' VAR1 SMU2 SMU1 SMU1 SMU2 SMU3 V=0 to -100 V=0 to 100 V=0 to -100 V=0 to 100...
  • Page 44 Module 5 Basic Measurement Channel and User Function Pages Two SMUs in Series Voltage across resistor VR = V1-V2 The voltage across the resistor (VR) is the difference between V1 and V2. A simple user function can be used to plot VR. 5-24...
  • Page 45 Module 5 Basic Measurement Measurement and Display Pages Two SMUs in Series VAR1' Ratio = -1 The VAR1’ mode is used to synchronously sweep two SMUs. Setting Ratio = -1 forces one SMU to sweep in the opposite direction of the other. 5-25...
  • Page 46 Module 5 Basic Measurement Graphics Page 0 to 200 V Two SMUs in Series WARNING Use the interlock cable and observe safety precautions. 511K Resistor The result is a clean 200 V sweep. Remember that there is a serious shocking hazard. The interlock cable is necessary for any voltage sweep greater than 42 V.
  • Page 47 Module 5 Basic Measurement 200 mA Output Two SMUs in Parallel NOTE 1 ohm Use Ground Unit Ground Unit or the chassis (GNDU) or ground as the Chassis Gnd VAR1’ VAR1 SMU return path. Shorting bar SMU1 SMU2 V=0 to 0.2 V=0 to 0.2 Circuit Common Two SMUs can be operated in parallel.
  • Page 48 Module 5 Basic Measurement Channel and User Function Pages Two SMUs in Parallel Current in resistor Itotal = I1+I2 A user function totals the current in both SMUs. 5-28...
  • Page 49 Module 5 Basic Measurement Measurement and Display Pages Two SMUs in Parallel VAR1' Ratio = 1 The VAR1’ mode with Ratio = 1 forces two SMUs to sweep the same voltage. 5-29...
  • Page 50 Module 5 Basic Measurement Graphics Page 0 to 200 mA Two SMUs in Parallel 1 ohm Resistor The result is a clean sweep to 200 mV. It shows the current measurement data near 200 mA. 5-30...
  • Page 51 16442A/B fixture interlock 16058A fixture compatibility The B1500A is a precision instrument. However, the ability to make precise and reliable measurements may be compromised by your fixturing to the device. The following section provides some theory and hints for making sense out of cabling and fixturing issues.
  • Page 52 Module 5 Basic Measurement Guard Connection for Non-Kelvin Connection Simplified Diagram Buffer Guard Force The guard connection is needed for measurement < 1 nA. Below 1 nA a regular coax cable's capacitance dominates over the DUT (device under test) capacitance. What you see is cable charging current.
  • Page 53 Module 5 Basic Measurement Triaxial Cable for Non-Kelvin connection Shield (Ground) Guard Force 16494A-001 16494A-002 (1.5 m) (3.0 m) Shield Capacitance 900 pF 1800 pF Guard Capacitance 130 pF 240 pF Force Resistance 160m ohm 320m ohm Shown above are typical capacitance and series resistance of the force line. If cables are too long, high capacitance may cause the SMU to oscillate.
  • Page 54 Module 5 Basic Measurement Why Use Guarded (Triax) Cables? Shield (Ground) Shield (Ground) Leakage Guard Force Force MOSFET Subthreshold MOSFET Subthreshold Triax Cables Coax Cables Eliminate cable low current errors. The triax cable is a special low dielectric loss, high impedance cable. This cable may be used down to fA levels when properly used with a guarded probe.
  • Page 55 The internal sensing resistor Rs is the only feedback path without the Kelvin connection. Note that the B1500A operates just fine without the sense cable. This is important to know because in general you do not need the sensing Kelvin connection. Most MOS measurements are high impedance and the residual cable loss is insignificant.
  • Page 56 The triaxial cables are good for low current measurements. However, two cables are necessary for low resistance Kelvin measurements. Agilent Technologies designed a special Kelvin triaxial cable for the precision semiconductor parameter analyzers. This cable is optimized for both low current and low resistance measurement.
  • Page 57 Module 5 Basic Measurement Why Kelvin Measurements? monitor Ω Re = 735 m Slope = 1/Re (Kelvin) Ω Rcable = 214 m Ib (mA) Slope = 1/(Re+Rcable) (Non-Kelvin) Vc (mV) In the example above, the device is connected with a SMU on the base sweeping current, a voltmeter on the collector, and the emitter is grounded with a Kelvin SMU.
  • Page 58 Basic Measurement Class Exercise Bipolar Re Using A Kelvin SMU You will connect a Kelvin triax cable to the B1500A You will then connect jumper leads and the bipolar device You will get the REKELV setup You will observe Re using Kelvin and Non-Kelvin connections.
  • Page 59 SMU2 SMU1 GNDU B1500A Rear View This class example requires a Kelvin triaxial cable. If the Kelvin cable is not available, substitute two standard triax cables. SMUs 1,2,3 can all be connected with Kelvin triaxial cables, but only SMU3 requires the Kelvin connection.
  • Page 60 16: Base 15: Collector Connect jumper leads as shown. Where, the SMU4 F terminal is connected to the B1500A’s SMU3 Sense connector. So the couple of the SMU3 F and SMU4 F terminals makes a Kelvin terminal. Locate the bipolar transistor in the corner of the socket as shown, with the flat side of the device facing toward you.
  • Page 61 Module 5 Basic Measurement To Get Setup Data To Get REKELV Test Setup: 1. Highlight REKELV in My Favorite Setup 2. Click Recall button 5-41...
  • Page 62 Module 5 Basic Measurement Single Kelvin Measurement Click button to start measurement Click the Single button to make a new measurement. You should see a response similar to this, will the analysis line correctly overlaying the curve. 5-42...
  • Page 63 Module 5 Basic Measurement Non-Kelvin Measurement Click button to start append measurement You can switch the analysis line between the two curves with this softkey Remove the jumper lead connected between the terminal 17 and the SMU4 F terminal. And click the Append button to add another measurement to the graph.
  • Page 64 Module 5 Basic Measurement Prober Kelvin Cable Connection To Kelvin Probe To Guarded Chuck Photo of SMU cable connection to a Cascade Microtech Summit probe station. The Kelvin triaxial cables mate directly to the probe station. 5-44...
  • Page 65 Module 5 Basic Measurement Connector Plate Non-Kelvin Connection Shielding Box GUARD Line COMMON FORCE,SENSE Line Kelvin Triaxial Cable GUARD FORCE 16493K Prober Probe Cable (Coaxial) SENSE GUARD COMMON Insulator Connector Plate 16495H-002 Jumper to eliminate cable 16495J-002 resistance in force line This is a "hybrid"...
  • Page 66 Module 5 Basic Measurement Simplifying the Prober Connection Use single triax for basic MOS FET measurements One triax on each Force line Leave the Sense lines open...no cable connected Use triax bulkhead feedthru adapters on the prober Use a probe holder with a triaxial connector Use a probe holder than accommodates replaceable probe tips (inexpensive repair) The next section sheds light on the confusing topic of connection to the device under test.
  • Page 67 Module 5 Basic Measurement Triaxial Probes Guarded to within 2mm of tip Single Triax Kelvin Triax These probes are guarded within 2mm of the probe tip, ideal for low current applications. The Kelvin triax probe is the ideal mate for the Kelvin triax cable. A third variation of these probes is a Kelvin triax probe with only one probe.
  • Page 68 Above 1 nA guarding is of little use. Cable capacitance has a negligible effect on the bias port. Use the floating guard triax(m) to BNC(f) adapter at the B1500A rear panel. Then use standard coax BNC cables. Use sense to minimize series resistance error. 100 mV errors can occur in bias voltages if remote sensing is not used.
  • Page 69 Short required View from B1500A rear panel To prevent shock hazard, the B1500A will not operate above 42 V, unless you connect the interlock circuit. The interlock connection is required when the voltage exceeds 42 V or when the program memory is used in a control program.
  • Page 70 16493J-002 3.0 m cable The 16493J interlock cable is designed to be connected directly between the B1500A’s interlock connector and the 16442A/B. If the fixture lid is closed, internal switch is closed, and then the B1500A can perform measurement up to 100 volts; 200 V with the HPSMU.
  • Page 71 This mates directly with the 16435A Interlock Cable Adapter mentioned on the previous page. Note You will notice that the socket modules for Agilent Technologies entire DC parametric product line are interchangeable. So socket modules that came with the 4142, 4145, 4155, or 4156 will work with the 16058A, 16088A/B, and 16442A/B fixtures.
  • Page 72 Module 5 Basic Measurement 5-52...
  • Page 73 Low Current Measurement...
  • Page 74 • Low-Current Gate Oxide Leakage This module is primarily written for the B1500A installed with the HRSMU (high resolution SMU) and covers sub pA measurement techniques. Course exercises are included which fully explore speed vs. accuracy issues to the fA level.
  • Page 75 Module 6 Low Current Measurement Low Current Measurement What is possible? Measurements below 10 fA at the wafer level Repeatability within a few fA Speeds less than 1 minute for subthreshold sweep Making wafer level measurements to fA levels is easy and routine using proper measurement procedures on a low noise probe station.

  • Page 76: Low-Current Measurement Challenges

    The probes themselves must be guarded. The B1500A defaults at bootup to setup conditions which are not optimized for ultra low current. This is desirable because there is a large trade-off between speed and ultra-low current accuracy.
  • Page 77 No vibration; cables stationary Microscope light, motors, etc. off This check list covers most sources of noise or stray capacitance. In a "clean" probing environment the B1500A can be used with short integration time and no delay time between steps.
  • Page 78 Module 6 Low Current Measurement Debugging A Noisy Probe System Where to Start? Sweep 0 to 1 volt with no cables attached to SMU Check that there is a +/- 3 fA base line Add prober cables but no prober Wait several minutes Still +/- 3 fA base line? Add shielded prober but no probes...

  • Page 79: Calibration And Zero Cancel

    Use the Calibration window to perform the SMU calibration and zero cancel. See the next page. NOTE: The B1500A provides the auto calibration function which automatically starts calibration for all modules every 30 minutes if the output switches of all modules are off for 30 minutes. You can enable or disable this function on the Calibration window.
  • Page 80 Module 6 Low Current Measurement Low Current Calibration & Zero Cancel Calibration Click Calibration button to open the Calibration window. SMU calibration is performed on the SMU Calibration tab screen. Specify the modules for calibration by checking the left check box and click Start Calibration button to start calibration. If ASU (atto sense/switch unit) is connected and 1 pA range is used for measurement, check Full Range Calibration check box before clicking Start Calibration button.
  • Page 81 Module 6 Low Current Measurement Class Exercise Measurements Near Zero fA You will be able to answer the following questions: What does a sweep into an open SMU port look like? What is the time per meas using PLC integration? Add a 1.5 m cable during a sweep...how long to settle? Move and bend the cable...how much current flows? To Get Started:...
  • Page 82 Module 6 Low Current Measurement ZERO CHECK - No cable Using Default SMU Setup Cursor at the maximum point 3.17 fA Marker at the minimum point -1.84 fA +/- 3 fA variation typical, using 16 PLC integration time With slight modification of the default SMU settings of Classic Test I/V Sweep, you can check the conditions of your measurement system.

  • Page 83: Zero Check

    Module 6 Low Current Measurement ZERO CHECK Channel Setup Change Mode to V and Function to VAR1 Delete SMU1 and SMU2 Click the Classic Test tab, I/V Sweep, and Select to display the Channel Setup screen. On this display, delete the rows of SMU1 and SMU2. Change the Mode of SMU4 to V.
  • Page 84 Module 6 Low Current Measurement ZERO CHECK Measurement Setup Do not change this screen This default sweep setup is enough for the Zero Check measurement. The sweep steps are small (10 mV) and that is ideal for checking current at fA levels. Also the sweep starts at 0, so no big discontinuities on the first step of the sweep.
  • Page 85 Module 6 Low Current Measurement ZERO CHECK Range and Integration Time Change SMU Range to AUTO or LIMITED 10 pA Change Integration Time to 16 PLC You must change the range setting from the default of LIMITED 1 nA to LIMITED 10 pA or to AUTO.

  • Page 86: Display Setup

    Module 6 Low Current Measurement ZERO CHECK Display Setup Linear, with zero set to mid scale The best check is done with a LINEAR scale which brackets either side of ZERO by 100 fA or less. A log scale is particularly unacceptable, Log plots of zero are not possible, and all readings of a log plot must be either all positive or all negative.
  • Page 87 Here we see the effect of connecting a cable to the open SMU port of the B1500A. The discontinuity lasted for 50 seconds of a 2 minute sweep from 0 to 1 volt in 10 mV steps.

  • Page 88: Effect Of Cable Movement

    Module 6 Low Current Measurement ZERO CHECK Effect of cable movement Bending Cable Bumping cable As you can see, your fixturing must be free from vibration. Bending cables during a test is another NO NO. The above measurements were made on a single triax cable for classic parameter analyzers. The Kelvin triax cable is less sensitive to movement (triboelectric effects).
  • Page 89 For ultra low current measurement, use ASU (atto sense/switch unit). The HRSMU has an innate 1 fA measurement resolution. And the ASU extends it to 0.1 fA. Note that the ASU must be connected to the HRSMU before turning on the B1500A. 6-17...
  • Page 90 If the ASU Serial Number field shows its serial number, the HRSMU-ASU combination is correct. If the ASU Serial Number field shows *s/n mismatch, the combination is wrong. The B1500A can work with this wrong combination however it cannot satisfy its specifications. The specifications are guaranteed for the correct combination of HRSMU and ASU.
  • Page 91 Module 6 Low Current Measurement ZERO CHECK Appendix: Using ASU HRSMU+ASU HRSMU This slide shows the open measurement results with ASU and without ASU. The ASU provides the 1 pA measurement range and the stable measurement results as shown. The 1 pA range is disabled with the default setting. To enable the 1 pA range, set the ranging mode to LIMITED 1 pA (1 pA limited auto ranging) or FIXED 1 pA (1 pA fixed range).

  • Page 92: Low-Current Subthreshold

    Module 6 Low Current Measurement Class Exercise Low Current Subthreshold You will: Check low level accuracy with fixture lid open/closed Observe trade off between resolution and speed Change resolution from LIMITED 1 nA to LIMITED 10 pA Observe trade off between averaging and speed Change integration from AUTO to PLC to MANUAL To Get Started: Use the next pages to setup the MOS FET correctly...
  • Page 93 On older fixtures, this scheme is shown in light blue lettering. In newer fixtures, this scheme is shown in white reverse background lettering. Connect the cables between the B1500A and test fixture as follows. SMU1 : SMU1 SMU2 : SMU2...
  • Page 94 Module 6 Low Current Measurement Class Exercise SD214DE MOS Subthreshold With lid closed, you should see this typical response using the IDVG setup data. If the subthreshold region is much higher, at the pA or nA level, the MOS device may be statically damaged. Replace the device using the handling procedure detailed on the previous page.

  • Page 95: Trade-Off Speed Vs Accuracy

    Module 6 Low Current Measurement Class Exercise Trade Off Speed vs Accuracy Change LIMITED range from 10 pA to 100 nA. Change Factor from 16 to 1. Change Mode from PLC to AUTO to NORMAL. You can trade off speed vs accuracy by varying the LIMITED range setting or the integration time setting.
  • Page 96 Module 6 Low Current Measurement Gummel Plot What is measured? Ve is swept while Vb and Vc are held at 0 V Ib and Ic are plotted on log scale Collector Base Emitter Constant Constant VAR1 SMU3 SMU2 SMU4 The "Gummel Plot" is an excellent low current measurement to make on a bipolar transistor. It plots log base current and log collector current against the same bias voltage.

  • Page 97: Low-Current Gummel Plot

    Module 6 Low Current Measurement Class Exercise Low Current Gummel Plot You will notice that sub 10 fA measurements are possible To Get Started: Set the jumper leads for the bipolar transistor Insert the device and perform a zero cancel offset Get the GUMMEL setup in the Demo preset group The following pages will lead you through the setup and measurement procedure for a low current Gummel measurement.
  • Page 98 With the 16442A/B fixture, note that there are two SMU numbering schemes..3 SMUs with force and sense, or six SMUs with force only. For this class example we will use the six (6) SMU scheme. Connect the cables between the B1500A and test fixture as follows. SMU1 : SMU1...
  • Page 99 Module 6 Low Current Measurement Gummel Plot Measurement Setup Small step size. Negative sweep values. Ve is swept below ground level to keep positive bias on the NPN device. 6-27...
  • Page 100 Module 6 Low Current Measurement Gummel Plot Range and Integration Time Maximum resolution 16 PLC Medium integration smoothes the plot at the ultra low levels. Make sure the range is set to AUTO or LIMITED to lowest current range: HRSMU: 10 pA MPSMU: 1 nA HPSMU: 1 nA 6-28...
  • Page 101 Module 6 Low Current Measurement LOW CURRENT MEASUREMENT Gummel Plot This curve shows a normal gummel characteristic of the bipolar transistor. The collector current is linear when plotted on log scale from 10 mA down to fA levels. Keep the fixture lid closed and do not bump any part of the setup during the measurement. (End of This Class Exercise) 6-29...
  • Page 102 Module 6 Low Current Measurement Gummel Plot With Base-Collector Self Oscillation Fix by isolating base-collector leads Fix by using ferrite bead on base lead This is a common occurrence when high frequency bipolar transistors are tested with jumper lead connections. When RF couples in the air to the base lead, there can be enough DC rectification to increase the base current bias.
  • Page 103 ULTRA LOW CURRENT Subthreshold Curve This curve shows the high quality measurement that you would typically expect with the B1500A and a well guarded probe station. The MARKER is sitting at 5.3 fA near the subthreshold region. To get best ultra low current accuracy, zero the SMU offset error just prior to taking the measurement by using the Calibration window.
  • Page 104 To prevent charging current due to residual cable or probe capacitance, you should limit the STEP size to 100 mV. The B1500A has a built-in delay time on the low current ranges, and you do not need to add extra time.
  • Page 105 Module 6 Low Current Measurement ULTRA LOW CURRENT Effect of Cable Charging Current Not part of the subthreshold characteristic You can see an initial high current that drops off after a few measurements. This is the effect when delay time is set to zero. Any residual capacitance due to un-guarded probes is the cause. This effect is minimal in this case due to the use of fully guarded probes to within 2 mm of the probe tip.
  • Page 106 (1 fA resolution). The factory default of LIMITED 1 nA gives 100 fA resolution and is adequate for most measurements. Since the B1500A can trade off speed for resolution, you get better speed performance by limiting current ranging.
  • Page 107 Module 6 Low Current Measurement Low Current Leakage Gate Oxide Leakage to fA levels Electrical connection to wafer backside Chuck must be guarded Gate Oxide Wafer backside Substrate Gate oxide leakage tests are complicated by the fact that there is an electrical connection to the back of the wafer.
  • Page 108 MOS FET. The MARKER is set to -27.590 mA. This is the point at which rupture of the gate oxide occurred. The B1500A has the sweep abort function which automatically aborts sweep measurement when any abnormal occurs.
  • Page 109 Module 6 Low Current Measurement FOWLER-NORDHEIM PLOT Measurement Page Negative sweep. Accumulation mode. Wait for 5 V initial step A 3 second delay at the beginning of the measurement will be required. The SMU must initially step from 0 to -5 V, a very large step. Fully guarded probes to within 2 mm of probe tip and fully guarded chuck eliminated the need for delays at every measurement point.
  • Page 110 Module 6 Low Current Measurement Low Current Gate Oxide Meas. Using Guarded Chuck SMU1 SMU2 Gate Oxide Capacitor Chuck 10^13 ohms Chuck Guard 10^13 ohms Shielding Box (Ground) This is a simplified block diagram of the prober requirements for a guarded chuck connection. When implemented properly, very fast low level sweeps are possible due to the elimination of stray capacitance at the probes (wafer top side) as well as in the chuck (wafer bottom side).

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