Keithley 238, 237, 236 Datasheet

LOW-LEVEL SOURCES

236, 237, and 238 Source-Measure Units

149

The 236, 237, and 238 Source-Measure Units (SMU)
are fully programmable instruments, capable of
sourcing and measuring voltage or current simulta­neously. These systems are really four instruments
in one: voltage source, current source, voltage mea­sure and current measure.

The 236 will source voltage from 100µV to 110V, and
current from 100fA to 100mA. It can also measure
voltage from 10µV to 110V and current from 10fA to
100mA. The 237 offers the same capabilities with a
decade enhancement in voltage source and mea-

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sure (1100V). In this higher voltage range, current
source and measure is 10mA maximum. The 238
offers a decade enhancement in current source and
measure (1A). In this higher current range, voltage
source and measure is 15V maximum.

The 236, 237, and 238 will measure very small cur­rents and voltages. With current sensitivity of 10fA,
measurement capabilities are equal to those of an
electrometer. Selectable integration and the filtering
of multiple measurements enhances sensitivity for
demanding applications.

Both source voltages and source currents settle to
specified accuracy in as little as 500µs. Programma­ble delay and fast, integrating measurement capa­bility can provide coordinated source-measure
times of 1ms.

Applications

These instruments address a wide variety of appli­cations, including the characterization of semicon­ductor devices, and the measurement of leakage
currents or resistivity. They are particularly useful as
source and measuring instruments in automated
test equipment (ATE).

The 236, 237, and 238 provide simple, accurate mea­surements in semiconductor applications. Multiple
units controlled with a personal computer make a

powerful semiconductor parameter analyzer. Non­standard tests are also performed efficiently be­cause of the unique versatility of these units.

Two accessory semiconductor test fixtures maintain
the signal integrity of the SMUs all the way to your
device. The 8006 is a general purpose test fixture,
and the 8007 is designed to accommodate either 24­or 48-pin devices. These test fixtures can be safety
interlocked with the 236, 237, and 238 to prevent
accidental shock.

A Keithley Model 707A or 708A switching matrix
and semiconductor switching cards may be used in
conjunction with the 236, 237, and 238 for opti­mum performance in automated semiconductor
measurement applications.

Keithley SMUs are powerful tools for research and
industrial test applications. The short set-up time
and simplified programming are big advantages for
tests that need to be up and running quickly. The
overall versatility is ideal for constantly changing
research use.

The large dynamic range of source and measure
capabilities permits accurate measurement of insu­lation resistance, leakage current, and dissipation
factors. The high sensitivity of these units make
them ideal for characterizing the electrical proper­ties of many materials.

Enhanced System Versatility

A single Source-Measure Unit eliminates most of the
complicated system integration problems involved
with setting up and programming individual sources
and meters. This new, compact module also saves
rack space and can be more economical than sepa­rate components.

New test systems can be developed much faster with
SMUs. There is only one set of device dependent com­mands (DDC) to learn, and the overall test system is
better coordinated for more efficient operation.

•Four instruments in one (voltage
source, voltage measure, current
source, current measure)

•10fA, 10µV measurement
sensitivity

•1100V source and measure (237
only)

•1A source and measure (238 only)

•Standard and custom sweep
capability including pulse

•1000 source/measurements per
second

•Four quadrant source operation

•Internal 1000-reading memory

ORDERING INFORMATION

236 Source-Measure Unit with two

7078- TRX-10 3-Slot Low Noise Triax
Cables, 3m (10 ft), one 236-ILC-3
Interlock Cable, 3m (10 ft), and one
237-ALG-2 Low Noise Triax Cable,
2m (6.6 ft)

237 High Voltage Source-Measure Unit

with two 7078-TRX-10 3-Slot Low
Noise Triax Cables, 3m (10 ft), one
236-ILC-3 Interlock Cable,
3m (10 ft), and one 237-ALG-2 Low
Noise Triax Cable, 2m (6.6 ft)

238 High Current Source-Measure Unit

with two 7078-TRX-10 3-Slot Low
Noise Triax Cables, 3m (10 ft), one
236-ILC-3 Interlock Cable,
3m (10 ft), and one 237-ALG-2 Low
Noise Triax Cable, 2m (6.6 ft)

These products are available with an
Extended Warranty. See page 635 for com­plete ordering information.

www.keithley.com

QUESTIONS?

1-800-552-1115 (U.S. only)

Call toll free for technical assistance,

product support or ordering information, or

visit our website at www.keithley.com.

149

150

LOW-LEVEL SOURCES

236, 237, and 238 Source-Measure Units

Figure 1: Internal Memory

Rotary

Dial

STEP

0001
0002
0003
0004
0005

0028

1000

SOURCE

+1.0000 V
+02.000 V
+03.000 V
+04.000 V
+05.000 V

-

-

-

+028.00 V

-

+1000.0 V

ACCESSORIES AVAILABLE

CABLES

236-ILC-3 Interlock Cable, 3m (10 ft)
237-ALG-2 3-Slot, Low Noise Triax Cable,

7078-TRX-3 3-Slot, Low Noise Triax Cable,

7078-TRX-10 3-Slot, Low Noise Triax Cable,

7078-TRX-20 3-Slot, Low Noise Triax Cable,

RACKS & RACK MOUNT KITS

1938 Fixed Rack Mount Kit
1939 Slide Rack Mount Kit
8000-10 Equipment Cabinet, 10 in high
8000-14 Equipment Cabinet, 14 in high

SOFTWARE

Metrics-ICS
Metrics-ICS-IV/TestPoint

SWITCHING (page 174)

707A Switching Matrix
708A Switching Matrix
7072 Semiconductor Matrix Card
7072-HV High Voltage Semiconductor

7153 High Voltage Low Current Matrix

7172 8×12 Low Current Matrix Card
7174A 8×12 High Speed, Low Current

TEST FIXTURES

8006 Component Test Fixture
8007 Semiconductor Test Fixture

OTHER

213 Quad Voltage Source
237-TRX-NG 3-Slot Triax to 3-Lug Female

See page 235 for descriptions of all
accessories.

2m (6.6 ft)

0.9m (3 ft)

3m (10 ft)

6m (20 ft)

Matrix Card

Card

Matrix Card

Triax Connector

QUESTIONS?

1-800-552-1115 (U.S. only)

Call toll free for technical assistance,

product support or ordering information, or

visit our website at www.keithley.com.

Measurements as a Function of Voltage,

SELECT

DELAY

00.100 s

00.100 s

00.100 s

00.100 s

00.100 s

-

00.100 s

-

00.100 s

MEASURE

+1.0921 nA
+1.1526 nA
+1.2234 nA
+2.3725 nA
+2.7713 nA

-

+3.6576 nA

-

+8.5763 nA

000.002 s

000.003 s

000.005 s

000.006 s

000.008 s

-

000.042 s

-

001.503 s

Current, or Time

Measurements can be taken and recorded in an internal
memory along with corresponding values of the source volt­age or current and time. Up to 1000 values of each variable,
correlated in time, may be accessed by the front panel using
either a rotary dial or a keypad. All measurement and source
values along with the elapsed time may also be obtained over
the IEEE-488 bus.

The internal memory is organized to obtain and present
measurement results in a versatile and easy to understand
manner. All source values and corresponding measurement
values are stored in sequence and share a common index.

Data Display

The contents of the internal memory may be accessed via the IEEE-488 bus or displayed in several for­mats using the front panel controls. Source and measure values may be displayed simultaneously or
with the index value. Delay and elapsed time may also be displayed with the index. The choice between
display modes is conveniently made using the Select keys. The delay time between source and measure­ment may be independently set from 0 to 65,000ms from the front panel or the IEEE-488 interface.

Selectable Sweeps of Voltage and Current

The 236, 237, and 238 may be programmed to perform source-measurements as a function of a stepped
voltage or current. Voltage and current may be swept linearly, logarithmically, or pulsed. The START,
STOP, STEP method of setting sweep parameters allows operators to become proficient at using the
instrument very quickly. Sweep parameters may be appended (APPEND key) to obtain more complex
test sequences.

Creating custom sweeps of voltage or current is facilitated by the use of three waveform operations: CRE­ATE, APPEND, and MODIFY. These allow the user to select waveform parameters, combine multiple
waveforms, and select and change any points in a waveform previously created or appended.

Fully-Guarded Four-Terminal Measurements

The 236, 237, and 238 outputs and inputs are fully guarded, and the units are configured to allow four­terminal measurements. Two-terminal measurements are also available for more standard test proce­dures. These outputs may be floated up to ±200V from ground.

Source Capability

The 236, 237, and 238 deliver full output current at maximum voltage to allow for optimum character­ization of high-power devices. The 236 delivers up to 100mA at 110V, the 237 delivers 10mA at 1100V, and
the 238 delivers 1A at 15V.

Suppression

Pushbutton suppression lets you make relative measurements with respect to a baseline or cancel back­ground signals. Suppression for a particular measurement may be any value within the specified oper­ating range of the instrument.

Fast, efficient programming makes these Source-Measure Units the ideal systems for a wide range of
testing procedures in the most comprehensive systems.

FIGURE 2: Data Displays FIGURE 3: SMU Source Capability

238:
±1A at ±15V

1A

Display source and measure values simultaneously.

Display delay time between source and measurement.

Display measured current.

Display time (∆T).

100mA

10mA

1mA

–1mA

–10mA

–100mA

–1A

236, 237, 238:

±110V,
±100mA

1V 10V 100V 1000V–1V–10V–100V–1000V

237:

±1100V at
±10mA

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LOW-LEVEL SOURCES

Default

Delay

Delay

Measure

Integration Time

Source
Value

Source-Delay-Measure Cycle

B

236, 237, and 238 Source-Measure Units

SOURCE-MEASURE UNIT: Sources voltage while measuring current, or

SWEEP WAVEFORMS DESCRIPTION

LEVEL, COUNT (number of DELAY­MEASURE cycles), DELAY, BIAS

Bias

Delay

Fixed Level

Meas.

Delay

Meas.

Level
Bias

sources current while measuring voltage.

FUNCTION: Can be used as DC source or meter, sweep source, or full

source-measure unit.

SOURCE-DELAY-MEASURE CYCLE:

151

Step

Start

Bias

Linear Stair

Start

Logarithmic Stair

t

offton

Level

Pulse

Step

Start

Bias

Linear Stair Pulse

Start

ias

Logarithmic Stair Pulse

Stop

Bias

Stop

BiasBias

BiasBias

Stop

Bias

Stop

Bias

START, STOP, STEP, DELAY, BIAS

START, STOP, POINTS/DECADE (5, 10, 25,
or 50), DELAY, BIAS

LEVEL, COUNT, TON, T

START, STOP, STEP, TON, T

START, STOP, POINTS/DECADE (5, 10, 25,
or 50), TON, T

OFF

, BIAS

WAVEFORM
OPERATORS DESCRIPTION

Allows selection of waveform
parameters. Generates all source
values.

OFF

, BIAS

, BIAS

OFF

Default Delay: Fixed delay for instrument settling.
User Delay: Additional delay for device under test or system

capacitance.

MEASURE:

Integration Time

Fast 416 µs 4-digit resolution
Medium 4 ms 5-digit resolution
Line Cycle 16.67 ms (60 Hz) 5-digit resolution

20.00 ms (50 Hz)

Elapsed Time: Measures and stores time from sweep trigger to mea-

surement complete for each step of sweep.

RANGING:

Source: Auto-ranging through keypad entry; fixed range selection

using rotary dial and SELECT keys (DC function). Fully pro­grammable in SWEEP function.

Measure: Auto or fixed range. Fixed range selection made by choice

of COMPLIANCE value.

FILTER:Takes n measurements, calculates and outputs average (n = 2, 4,

8, 16, or 32, selectable).

SUPPRESS: Subtracts displayed measurement from subsequent read-

ings.

MENU: DC Measurement Delay, Default Delay On/Off, Local/Remote

Sense, 50/60Hz, IEEE Address, Self Tests.

DATA ENTRY: Numeric keypad or detented rotary dial.
TRIGGER:

Input and Output: Set for any phase of SOURCE-DELAY-MEASURE

sequence or trigger output at end of sweep.

Origin: Internal, External (including front panel MANUAL TRIGGER

button), IEEE-488 bus (TALK, GET, “X”).

MEMORY: Stores one full sweep (up to 1000 points) of source, delay, and

measure values, elapsed times, and sweep parameters. Lithium bat­tery backup.

INTERLOCK: Use with test fixture or external switch. Normally closed;

open puts instrument in standby.

Create

Combines multiple waveforms and
adds new points to those already in
memory.

Append

Select and change any points in a
previously created (or appended)
waveform.

product support or ordering information, or

Modify

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QUESTIONS?

1-800-552-1115 (U.S. only)

Call toll free for technical assistance,

visit our website at www.keithley.com.

151

152

LOW-LEVEL SOURCES

236, 237, and 238 Source-Measure Units

EXECUTION SPEED

MINIMUM SOURCE-DELAY-MEASURE CYCLE TIME: 1ms.
RESPONSE TO IEEE-488 COMMAND (as a source): 25ms.
MEASUREMENT RATE: 1ms per point into internal buffer.
CONTINUOUS MEASUREMENT SPEED (source DC value over

IEEE-488 bus): 110 readings per second.

TRIGGER LATENCY TIME: <2ms.

IEEE-488 BUS IMPLEMENTATION

MULTILINE COMMANDS: DCL, LLO, SDC, GET, GTL, UNT, UNL,

SPE, SPD.

UNILINE COMMANDS: IFC, REN, EOI, SRQ, ATN.
INTERFACE FUNCTIONS: SH1, AH1, T6, TE0, L4, LE0, SR1, RL1, PP0,

DC1, DT1, C0, E1.

All front panel functions and setups are available over the IEEE-488

bus, in addition to Status, Service Request, Output Format, EOI,
Trigger, and Terminator.

IEEE-488 address is set from the front panel menu.

GENERAL

LOAD CAPACITANCE: Stable into 20,000pF typical.
REMOTE SENSE: Corrects for up to 2V drop in each output lead.

Maximum 1kΩ per sense lead for rated accuracy. Residual output
resistance (as a voltage source) is 0.5Ω.

GUARD: Output Resistance: ≤12kΩ.

Maximum Output Current: ±2mA.
Offset Relative to Output HI: ±2mV max.

ISOLATION (Output LO to chassis): Typically >10

500pF (650pF on Model 238).

MAXIMUM COMMON MODE VOLTAGE: 200V.
CONNECTORS: Outputs: 3-lug triax.

Trigger Input/Output: BNC.
Interlock: 3-pin miniature DIN.

TEMPERATURE COEFFICIENT (0°–18°C & 28°–50°C): ±(0.1 × appli-

cable accuracy specification)/°C.

ENVIRONMENT:

Operating: 0°–50°C, 70% relative humidity up to 35°C. Linearly der-

ate 3% RH/°C, 35°–50°C.

Storage: –25° to 65°C.
EMC: Conforms to European Union Directive 89/336/EEC.
SAFETY: Conforms to European Union Directive 73/23/EEC (meets

EN61010-1/IEC 1010).

WARM-UP: One hour to rated accuracy.
COOLING: Internal fan forced air cooling.
POWER: 105–125 or 210–250V AC (external switch selectable), 90–

110V and 180–220V version available. 100VA max. (120VA max. on

Model 238).
DIMENSIONS, WEIGHT: 89mm high × 435mm wide × 448mm deep

1

(3

⁄2in × 171⁄8in × 175⁄8in). Net weight 9kg (19.75 lb).

QUESTIONS?

1-800-552-1115 (U.S. only)

Call toll free for technical assistance,

product support or ordering information, or

visit our website at www.keithley.com.

10

Ω in parallel with

VOLTAGE

236, 237 ±1.1000 V

237 Only ±1100.0 V 100 mV ±(0.04 % + 240mV) 100 mV 10 mV ±(0.035%+100mV )
238 Only ±1.5000 V 100 µV ±(0.033% +800 µV 100 µV 10 µV ±(0.028% + 450µV

IO= Output current; IFS= Full scale on selected current range

1

Specifications apply for 5-digit resolution. For 4-digit resolution add 100ppm of range.

2

Assumes remote sense for I > 100µA.

3

On the 1A range use [IO/IFS] × 250µV.

COMPLIANCE: Bipolar current limit set with single value.

Maximum: ±100mA (except ±10mA on 1100V range in Model 237 and ±1A on 15V range in Model

Minimum: ±1% of range, except 0.5% of 1.1V range.
Accuracy,Step Size: Same as current source.

NOISE (p-p):

1.1 V (1.5V on 238) <10ppm of range 15 mV

WIDEBAND NOISE: 0.1 to 20MHz, 8mV p-p typical.
OVERSHOOT: <0.01% (110V step, 10mA range).
SETTLING TIME: <500µs to 0.01% (110V step, 10mA range).
NMRR: >60dB at 50 or 60Hz (LINE CYCLE integration time selected).
CMRR: >120dB at DC, 50 or 60Hz (LINE CYCLE integration time selected).
INPUT IMPEDANCE (as a voltmeter): >10

RANGE ACCURACY ACCURACY

(Max. STEP (1 Year, RESOLUTION (1 Year,

Value) SIZE 18°–28°C) 4-Digit 5-Digit 18°–28°C)

±11.000 V 1 mV ±(0.033% + 2.4mV ) 1 mV 100 µV ±(0.025%+ 1mV)
±110.00 V 10 mV ±(0.033% + 24mV ) 10 mV 1 mV ±(0.025%+ 10mV )

±15.000 V 1 mV ±(0.033% + 2.7mV) 1 mV 100 µV ±(0.025%+ 1mV)
±110.00 V 10 mV ±(0.033% + 24mV ) 10 mV 1 mV ±(0.025%+ 10mV )

238).

RANGE 0.1–10Hz DC–20MHz

110 V – 1100 V < 3ppm of range 40 mV

11 V (15 V on 238) < 3ppm of range 15 mV

CURRENT SOURCE I MEASURE I

RANGE ACCURACY ACCURACY

(Max. STEP (1 Year, RESOLUTION (1 Year,
Value) SIZE 18°–28°C) 4-Digit 5-Digit 18°–28°C)

All ±1.0000 nA 100 fA ±(0.3 %+ 450 fA) 100 fA 10 fA ±(0.3 % + 100 fA)

±10.000 nA 1 pA ±(0.3 %+ 2 pA) 1 pA 100 fA ±(0.3 % + 1 pA)
±100.00 nA 10 pA ±(0.21%+ 20 pA) 10 pA 1 pA ±(0.21 % + 6 pA)
±1.0000 µA 100 pA ±(0.05%+ 200 pA) 100 pA 10pA ±(0.04 % + 6 pA)
±10.000 µA 1 nA ±(0.05%+ 2 nA) 1 nA 100 pA ±(0.035% + 700 pA)
±100.00 µA 10 nA ±(0.05%+ 20 nA) 10 nA 1 nA ±(0.035% + 6 nA)
±1.0000 mA 100 nA ±(0.05%+ 200 nA) 100 nA 10 nA ±(0.035% + 60 nA)
±10.000 mA 1 µA ±(0.05%+ 2 µA) 1 µA 100 nA ±(0.038% + 600 nA)

238 Only ±1.0000 A 100 µA ±(0.12%+ 700 nA) 100 µA 10µA ±(0.12 % + 300 µA)

1

2

COMPLIANCE: Bipolar voltage limit set with single value.

NOISE (p-p of range): 0.1–10Hz: <3ppm (<20ppm on 1nA and 10nA ranges and on 1A range in

OVERSHOOT: <0.01% typical (10mA step, R
SETTLING TIME: <500µs to 0.01% (10mA step, R
OUTPUT R, C: >10

±100.00 mA 10 µA ±(0.1 %+ 20 µA) 10 µA 1 µA ±(0.1 % + 6 µA)

Specifications apply for 5-digit resolution. For 4-digit resolution, all offset terms are 200ppm of range.
Offset specification applies for 23°C ± 1°C with suppression. Temperature coefficient 50fA/°C.

Maximum: ±1100V (except ±110V in Model 238 and on 100mA range in Model 237).
Minimum: ±0.1% of selected current range.
Accuracy,Step Size: Same as voltage source.

Model 238).

SOURCE V MEASURE V

2

100 µV ±(0.033%+650 µV 100 µV 10 µV ±(0.028% + 300µV

14

Ω paralleled by <20pF (on 1nA range).

+ [IO/IFS] × 450µV) + [IO/IFS] × 450µV)

= 10kΩ).

= 10kΩ).

L

3

+ [IO/IFS] × 600µV)

+ [IO/IFS] × 600µV)

14

Ω paralleled by <20pF.

L

1

1

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