Keysight Technologies B2981A Installation guide

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-


A
A
-+DUT
Shield
(GND)
i
Ammeter (high)
Ammeter
Common
(Floating)
Im
common
DC source
Ground noise
DUT is floating
X
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.
A
A
-+
+
DUT
Vs
Shield (GND)
Guard
Ammeter is connected on the voltage source.
i
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
A+
+
Vs VsHigh
Ammeter
Common
LED
Test Fixture (N1295A)
J1
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.
1.
2.
3.
(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
2.
1.
3.
(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
On
(2) Ammeter On
(3) The first measurement is made automatically.
1.
2.

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.
3.
(1) Press key, then
(2) press key two times until key appears.
1.
2.
(1) Click on the VS Function by , and the VS
menu options are displayed.
(2) Press assist key.
1.
Move the cursor on the VS Function by rotating .
2.

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)
 
1.
2.
3.
4.
5.
6.
7.
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.
1.
2-1. 2-2.
2-3.