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Introduction

For next generation ULSI development,

precise characteristics evaluation of

semiconductors during device devel-

opment, process development, and

circuit design phase is essential. As

well as IV measurement, C-V measure-

ments are very important to determine

the oxide thickness. Other important

parameters such as substrate impurity

concentration can also be calculated

from C-V measurement results.

Also, improvement of test productivity

is mandatory for faster IC development.

This application note explains how

to perform accurate and efficient

C-V characteristics measurements

of multiple devices by changing con-

nections using the Agilent E5250A

Matrix Switch.

Difficulties in Device

Characterization

On Test Element Groups (TEG), there

are various devices. They are for dc

characteristics measurements and

for C-V measurements. So, to improve

test efficiency, it is necessary to auto-

mate the changing of measurement

instrument connections and multi-

probing on the wafer. A switching

matrix is required to automate

switching measurement instruments

and test devices.

Until now, there has been no suitable

switching matrix for precise low cur-

rent measurements and accurate

capacitance measurements. Using

existing switching matrices, the per-

formance of measurement instruments

was sacrificed. C-V measurement

results included big error due to the

residual impedance in the extension

cables and matrices. It was also diffi-

cult to compensate for the measure-

ment error.

For precise testing, you had to per-

form IV and/or C-V measurements on

separate probing stations. There was

no adequate matrix available to com-

bine these into one probe station.

Therefore, the biggest issue was that

measurement productivity was lowered

because you had to manually switch

measurement instruments and devices.

Accurate and Efficient C-V Measurements

Application Note E5250A-3

Agilent E5250A Low Leakage Switch Mainframe

Figure 1. Agilent 4156C, 4284A, and E5250A with wafer prober

Summary of content (8 pages)

PAGE 1
Accurate and Efficient C-V Measurements Application Note E5250A-3 Agilent E5250A Low Leakage Switch Mainframe Introduction For next generation ULSI development, precise characteristics evaluation of semiconductors during device development, process development, and circuit design phase is essential. As well as IV measurement, C-V measurements are very important to determine the oxide thickness.
PAGE 2
OUTPUT 1 2 3 4 5 6 7 8 9 10 11 12 INPUT Instrument Connection Low Leakage Path SMU 1 SMU 2 SMU 3 SMU 4 SMU 5 HF 1 CV 1 SMU 6 HF 2 C-V Path CV 2 Figure 2. E5250A Matrix Switch block diagram Solution Using the Agilent E5250A Low Leakage Switch Mainframe The Agilent E5250A Low Leakage Switch Mainframe provides the solutions to those problems. There are two types of plug-in modules: Option 001 10 × 12 Matrix Switch Module and Option 501 24-channel Multiplexer Module.
PAGE 3
Agilent 16495F/G Option 002 Connector Plate Figure 5 shows measurement circuit diagram of Agilent 4284A including matrix switch and cables. The connector plate is used as a part of return path for the measurement signal current. The compensation calculation is performed assuming the outer shield of triaxial cables are connected to each other at connector plate as shown in Figure 5.
PAGE 4
Agilent 4284A LCR Meter are not calibrated by open/short calibration. In general, load calibration should be additionally performed in such a case. But, for wafer measurements, it is very difficult to have stable and accurate load, so you should perform compensation as described next instead of load calibration.
PAGE 5
Figure 9. Setup editor Capacitance Measurement Using Agilent ICS To measure capacitance using Agilent ICS, perform the following steps. The C-V driver (Agilent E5232B) and Matrix Switch driver (Agilent E5233B) must be installed with Agilent ICS. Figure 10. Agilent 4284A Setup dialog box • Agilent 4284A Configuration Setup Set the Agilent 4284A configuration as shown in Figure 8.
PAGE 6
• Setup Matrix Switch Figure 12 is the matrix switch setup dialog box, which allows you to easily control the matrix switches. Click cross point boxes of switchings to close. This example setup is for the gate-substrate capacitance of a MOSFET. CMH is connected to the substrate terminal and CML is connected to gate. • Invert Bias Polarity Transform Editor enables you to define functions to calculate data vectors or parameters. We apply reverse staircase voltages to substrate in C-V measurement.
PAGE 7
Figure 17. Sequence setup Compensation Using Agilent IBASIC Program Capacitance compensation routine is available as a sample program on a diskette furnished with Agilent E5250A Switch Mainframe. Tips for More Accurate Capacitance Measurements • Wafer Chuck Capacitance In general, wafer chuck should be isolated from circuit common and ground. This means it should have higher impedance at the measurement frequency.
PAGE 8
Table 1. Ordering Example E5250A (*) 001 301 16494A 4284A 4156A 001 003 (*) 001 006 (*) 010 16495B 002 8120-4461 16048E 1250-2405 42091A 10833A 10833B E5230B E5231B E5232B E5233B Low Leakage Switch Mainframe 10 x 12 Matrix Switch Card (E5252A) Relay Function Test Adapter Triaxial Cable Triaxial Cable (1.5 m) Triaxial Cable (80 cm) Precision LCR Meter Power Amplifier/ DC Bias Compensation for 2 m /4 m Cable Precision Semi. Para.