Keysight Technologies B2981A Guida all'installazione

Keysight Technologies

Low Current Semiconductor Measurements

Using the B2980A Series Ammeter

Keysight B2981A/B2983A Femto/Picoammeter

Keysight B2985A/B2987A Electrometer/High Resistance Meter

Technical Overview

Introduction

Low current measurement is a key performance metric for picoammeters and

electrometers, which often specify atto-ampere (aA) level current measure-

ment resolution. In addition to ultra-low current measurement capability, it is



smooth-out noisy data and basic measurement data evaluation tools to simplify

debugging.

The four key capabilities necessary to successfully make sensitive low current

measurements are listed below:

1. Femto-ampere current measurement capability.

 

 

cancelation.

 

domain graphs, etc.

The Keysight B2981A/B2983A Femto/Picoammeter and B2985A/B2987A Elec-

trometer/High Resistance Meter provide both superior performance of 10 aA



the features listed above.

This technical overview highlights the B2980A Series ammeter current mea-



Note: The B2983A and B2987A have an internal rechargeable battery that allows them to

operate without being connected to AC power.

Important words used in

the document:

–Low-current metric system



–pico (p)= 10-12

–femto (f)= 10-15

–atto (a)= 10-18

03 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

Measurement Basics and the B2980A Series Performance

1. Low noise, low impedance and low current ammeter provides stable

measurement data

The B2980A Series ammeter has the following features:

–The B2980A’s low noise design achieves better than 100 aA current measurement (with 10 aA minimum

resolution).

–The low input resistance and low offset voltage allow a faster measurement response and more accurate

measurement results.

These features provide the B2980A Series ammeter with the ability to perform stable measurements

across a wide range of applications (especially very low current measurements).



and grounded DUTs







-

ing current to the device under test (DUT). The ammeter common is connected to the inner shield of



The chassis is connected to earth ground through the power cable ground connection.



ammeter connected at the other end. Since the ammeter is not connected to earth ground, any com-





-+DUT

Shield

(GND)

Ammeter (high)

Ammeter

Common

(Floating)

common

DC source

Ground noise

DUT is floating

No ground

loop noise



04 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

2. Floating ammeter design provides stable measurements for both

(continued)



Figure 2 shows the case where one of the ends of the DUT is grounded. In this case the con-

nection scheme shown in Figure 1 cannot be used. The reason for this is that the ammeter



-



source (Vs) is connected to the ammeter common. The source voltage (Vs) is applied through

the ammeter’s input terminal.







–The ability to synchronize the voltage source output with the measurement timing.

–The ability to display the voltage and current relationship in an X-Y graph on the instrument front panel.



functions improve measurement data quality

Measurement Speed selection:

The B2980A series supports four measurement speeds: Quick, Normal, Stable, and Manual.

The Quick, Normal and Stable measurement speeds are available when using auto mode, and

they correspond to integrating over some fraction or multiple of the power line cycle (PLC).

For these cases the measurement speed is automatically set for a given measurement range

to provide the best data for the selected speed. If you want to control this parameter, then the



Filtering capability:

-



reduce noise effects.

DUT

Shield (GND)

Guard

Ammeter is connected on the voltage source.

Ammeter (high)

Ammeter

Common

(Floating)

DUT is grounded



05 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview



functions improve measurement data quality (continued)

Null (Zero cancel) capability:

To remove the effects of any residual offset currents, you can have the instrument

automatically subtract out these currents by pressing the Null key.







have been removed using the NULL function. Using the B2985A’s Roll View the data is

displayed over a 100 second time span. With these settings it is easy to see that a stable

100 aA level measurement can be made.

4. Histogram View enables real-time data distribution analysis



measurement data statistically in real-time. Once you know the characteristics of the

noise you are seeing you can decide if it is better to reduce the noise at its source or to



you can simply use the average of the histogram.





have when making measurements in a noisy test environment.





Figure 4(a) shows Histogram View results using 0.1 power line cycle (PLC) measurement



measured sigma is 0.17 pA. Figure 4(b) shows the same measurement performed using



measurement data. In this case the measured sigma is 0.018 pA, which is about 9.5 times

(= 0.17/0.018) smaller than the sigma shown in Figure 4(a).



The Roll View graph shows the measurement is

stable at the 100 aA level within a 100 sec interval.

Measurement condition:

- Speed: Quick

- 2 pA range

- Filter: 100 moving average

- Null: zero cancel

- DUT: Open condition

Quick measurement speed

Zero cancel Filtering

06 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

4. Histogram View enables real-time data distribution analysis

(continued)



conjunction with the Histogram View to improve data quality





-

tion and data averaging.



Measurement steps on B2985A/87A front panel operation

This section gives step-by-step instructions on how to use the B2980A’s Femto/Picoam-







voltage to the LED.

















Figure 5 shows the proper connections to measure the I/V charac-

teristics of an LED. Note that it is important to connect the ammeter

common to the chassis ground using the banana to lug cable as





then this ground connection is not necessary.

(a) 0.1 PLC speed measurement. (b) Normal speed measurement using the data averaging.

Measurement condition:

- Speed: 0.1 PLC

- Filtering: None

Measurement condition:

- Speed: Normal

- Filtering: Moving average (100 points)

9.5X improvement

in noise distribution

Figure 4. Using histogram view and other functions to improve measurement data.

A+

Vs VsHigh

Ammeter

Common

LED

Test Fixture (N1295A)

B2980A Series

Triax cable

Connect with the

Banana to lug cable

Chassis ground

Vs Low

N1254A-101

adapter Coax

cable

adapter



07 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

(continued)

The following steps outline how to setup and measure the low current I/V characteristics of an LED.

Detailed B2985A front panel setup instructions



function key, and then press the [AMPS(I)] assist key at the right of the screen.

 



Step 3. (1) Press the Voltage Source [On/Off] key to enable the voltage source to output 0 V.

 

(2) Press the Ammeter [On/Off] key to connect the ammeter.

(3) A single current measurement is made automatically.

(1) Press the key to show the View function key.

(2) Press key, then

(3) press key.

(3) The field pointer changes to green (EDIT mode),

and the status information willchange to EDIT

(4) Set the voltage to zero volts by rotating the ,

and press to fix the value.

Status

(1) If the Voltage Source value is not 0 V, then

perform the following steps.

(2) Rotate and to move the field pointer onto

the Voltage Source value, and press the knob to

edit the voltage.

(1) Voltage Source

(2) Ammeter On

(3) The first measurement is made automatically.

08 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

(continued)

Step 4. Press the [Run/Stop] key to start continuous current measurements. The “AUTO” indicator at the bottom of the screen shows

that the measurement is continuously repeating.

 

Step 5. Change the voltage source to edit mode using the procedure outlined in step 2. (B2985A/87A only).

 

Step 6. (1) Continue rotating the [Knob] and increasing the voltage until the current is between 10 to 20 mA.

 

(2) The LED starts to emit light at around 1.5 V.

 

Roll View shows the measurement history

Rotate slowly to increase the voltage. The

value increases as you rotate the [knob] clockwise.

Stop when the voltage reaches approximately 1.0 V.

(3) Roll View shows the current drift status after the

LED’s temperature stabilizes.

(1) Further rotate , and increase the voltage until

the current is between 10 to 20 mA.

(2) LED light up as

shown in the picture.

As the LED

heats up the

current drifts.

09 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

(continued)



 

 

(3) Check the current transient in the Roll view display and note the

  

 

 









The following steps outline how to plot the I/V characteristics of an LED.

Step 1. (1) Press the [Meter View] function key at the bottom of the screen.

(2) Then press the [More ... 1 of 3] assist key twice so that the third set [More ... 3 of 3] of softkey labels is displayed on the

assist keys at the right of the screen.

(3) Press the [Show VS Func.] assist key to show the VS function menu.

Step 2. (1) Move the cursor by rotating the [Knob] until the cursor is on the VS Function and then select it by pushing the knob.

The VS Function is now in edit mode and the assist softkey menu at the right of the screen represents the available VS

Functions.

(2) Press on the [LINEAR SINGLE] assist key.

(3) press key.

(1) Press key, then

(2) press key two times until key appears.

(1) Click on the VS Function by , and the VS

menu options are displayed.

(2) Press assist key.

Move the cursor on the VS Function by rotating .

10 | Keysight | Low Current Semiconductor Measurements Using the B2980A Series Ammeter - Technical Overview

(continued)

Step 3. (1) The Source function graphic changes to linear single sweep (upper right corner of screen).

 

- Start: 0 V

  

- Points: 37 (or any number required to achieve the desired Step voltage.)



(3) Press the [More... 3 of 3] assist key two times until it changes to the [More... 2 of 3] softkey label.

(4) Press the [Show Trigger] assist key. The trigger sub-panel is now displayed. If the Trigger mode is set to MANUAL as shown

in step (5), then perform the following steps:

(5) Using the [Knob], place the cursor over the Trigger function and press the knob to select it. This changes the assist softkey

labels.

(6) Press the [AUTO] assist key to change the Trigger function to AUTO mode.

(7) In this mode, the trigger parameter changes automatically as you change the sweep parameters.

Step 4. (1) Press the [View] key, and then press the [Graph View] function key. The X-Y graph view panel opens.

 

2-1. Y: I (A)

2-2. X: SRC (Source V)

 

Optional steps

(1) Press key, then press soft key.

(2) Edit Y and X axis parameter to plot the data.

Use to select items, and select from the

list of the assist key.

2-1. 2-2.

2-3.

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