Parametric Instrument Accessories

Technical Overviews

GNDU connections

Kelvin connection

These instructions apply when all connections are Kelvin. Two probes must contact the wafer in this connection.

Connect a Keysight 16493K Kelvin triaxial cable (or two Keysight 16494A triaxial cables) between the SMU and the connector plate. Connect the FORCE and SENSE lines to probes separately. Connect the triaxial connector on the probe cable as shown in Figure 4.5. To prevent oscillations, use short cables.

Non-Kelvin connection

These instructions apply when all connections are non-Kelvin. Connect the Keysight 16494A triaxial cables between the SMU and the Connector plate.

Kelvin to non-Kelvin connection

These instructions apply when the connections up to the Connector Plate are Kelvin, but the probe is a non-Kelvin connection.

Connect a Keysight 16493K Kelvin triaxial cable (or two Keysight 16494A triaxial cables) between the SMU and the Connector plate.

ASU connection

Each ASU has one Dsub control cable, one triaxial cable, and (optionally) two coaxial cables connected to it. The cables can be connected to the ASU inside the shielding box through the 16495K plate.

When making IV measurements with the SMUs, all measurements are Kelvin. The SENSE line information is fed back to the SMU via the Dsub cable.

When making CV measurements, the four-terminal pair (4TP) connections are correctly terminated inside of the ASUs. The ASUs also allow for a current return path between the outer conductors to stabilize the series inductance and improve accuracy. You must connect the furnished wire between the two ASUs to enable this feature.

CMU accessories

B1500A has the multi frequency capacitance measurement unit (MFCMU). There are two types of CMU connection as follows.

• Standard four terminal pair (4TP) connection

• SCUU positioner-based probing mode

Connector type

There are two main styles of Kelvin SMU connections. When connecting instruments together, you need to make sure that you have the correct type of Kelvin triaxial cables.

Type A connectors have two screws, one guide pin, and two triaxial terminals. Type B connectors have one screw and two triaxial terminals. These connectors are also different in their width and thickness.


Several possibilities exist for connecting the Source Monitor Units (SMUs) to the DUT. The great variety of available cables can be categorized into mainly three types:

Triaxial cables have three layers or leads: a center conductor for the signal, a middle conductor that is actively driven to be at the same potential as the center conductor to eliminate leakage currents, and a grounded (Common) outer conductor.

Kelvin triaxial cables are similar to triaxial cables, except that both the Force and Sense lines from the SMU run through the same cable. The Force and Sense lines share a common driven guard and a common outer shield. Kelvin triaxial cables typically give better low-current measurement performance than you would get from using two separate triaxial cables for the Force and Sense lines.

The GNDU cable is a special triaxial cable designed to handle the large currents (up to 4.2 A) that the ground unit can sink. In the GNDU cable the center conductor is SENSE, the middle conductor is FORCE, and the outer conductor is Common.


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