Like testing of other engineered materials, measurements made on substances created with nanotechnology are aimed at discovering useful properties. The nature of nanotech materials requires some novel testing techniques.
The Model 4200-SCS is supplied with application tests specifically designed for the dynamic field of nano scale electrical characterization. For researchers not familiar with all the nuances of electrical characterization, this test project assists in the rapid and accurate measurement of structures without having to spend lots of time learning how to set up the hardware. This nano test project includes tests for I-V, pulsed and transient I-V, and C-V measurements.
Carbon Nanotube Transistors
Carbon nanotubes (CNTs) have unique properties that make them good candidates for a variety of electronic devices. They can have either the electrical conductivity of metals or act as a semiconductor. Characterizing the electrical properties of delicate nano electronic devices requires instruments and measurement techniques optimized for low power levels and high measurement sensitivity. The 4200-SCS is supplied with a test project for making some of the most commonly used CNT FET measurements. This test project includes tests for I-V, pulsed and transient I-V, and C-V measurements.
Graphene, the single-atom-thick crystal of carbon, has outstanding electrical conductivity. It also has extremely strong, yet flexible bonds. Its hardness is greater than the hardness of diamond. For the semiconductor industry, the exciting thing about graphene is that electrons travel through it unimpeded, and these electrons behave according to quantum electrodynamic principles. Carrier mobilities through graphene are on the order of 10,000cm2/V-s at room temperature, and mobility values as high as 200,000 cm2/V-s on suspended samples of graphene have been reported. Grapheneâ€™s high mobility has already led to the development of very high frequency (100GHz and higher) RF transistors.
For graphene or a graphene-based material to replace silicon, it must have a bandgap so that a FET channel can be turned on and off. A precision SMU found in the 4200-SCS analyzer is needed to modulate the substrate or â€œgateâ€ voltage to characterize the sample performance across a range of gate voltages.
MEMS devices are miniature electromechanical sensors and actuators fabricated using VLSI processing techniques. Typical sizes for MEMS devices range from nanometers to millimeters (100 nm to 1000 Î¼m).
Testing MEMS elements in the earliest stages of the manufacturing process can help contribute to lowering production cost. In particular, testing MEMS at the on-wafer or die level is critical for lowering mass production cost. C-V and Pulse I-V are common measurement techniques to evaluate the performance of a MEM. In particular, capacitive sensors have hysteresis characteristics based on the amount of electrical charge being inducted to the electrodes. This hysteresis is one of the parameters that can be evaluated by a C-V measurement.
Unlike general-purpose measurements and I-V curve generation on macro- and micro-scale components and materials, measurements on molecular wires require special care and techniques. When the resistance to be measured is relatively low or when the resistance of the probes or the contacts is relatively high, a four-point probe will yield more accurate results. This is easily accomplished with the 4200-SCS source measure units.
C-V measurements on semiconductor nanowires and nanowire-based devices can be used to derive important characteristics about the device, including mobility, carrier density, and device speed. Sometimes the capacitance is plotted as a function of channel length or gate length. These capacitance measurements can often be quite small, <1pF. As a result, using proper techniques to reduce parasitic capacitance from affecting measurement accuracy is important. The two test modules supplied with the 4200-SCS perform C-V sweeps on a two-terminal nanowire device. Both tests are similar, but use different drive frequencies. Capacitance versus voltage graphs are generated by the tests.
4200-SCS Parameter Analyzer Mainframe
The 4200-SCS is a modular, fully integrated parameter analyzer that performs electrical characterization of devices, materials or processes. With nine measurement slots and a built-in low noise ground unit, you can configure it to precisely meet your test requirements or budget constraint.
SMUs are precision instruments which are used for sourcing current or voltage and simultaneously measuring current and voltage with high accuracy and speed.
Two SMU models are available for use with the 4200-SCS, the 4200-SMU medium power SMU or 4210-SMU high power SMU. Both models occupy only one instrument slot and up to a total of nine can be installed in the 4200-SCS.
Offering the industryâ€™s widest dynamic range, the medium power 4200-SMU operates from 100 nA to 100 mA and 1 uV to 210 V and the high power 4210-SMU operates up to 1 A. The low current measurement capabilities of either SMU can be extended to 0.1 fA resolution by adding an optional preamplifier.
The 4200-SCS can be configured to support multi-frequency (1 kHz to 10 MHz) C-V, Very Low Frequency (10 mHz – 10 Hz) C-V, and Quasi-static C-V measurements.
The 4210-CVU multi-frequency C-V module occupies one slot in the 4200-SCS chassis and provides C-V, C-t, and C-f measurement sweeps with up to 4096 data points. Built-in compensation routines remove parasitic effects and ensures the integrity of connections to the DUT. An optional power package allows a DC voltage bias of up to +/- 200 V.
The Very Low Frequency C-V method takes advantage of the low current measurement capability of the 4200-SCS Source Measure units (SMUs) to perform C-V measurements. The Very Low Frequency C-V technique makes it possible to measure very small capacitances at a precise low test frequency. This patent-pending, narrow-band sinusoidal technique allows for low frequency C-V measurements of very high impedance devices, up to >1E15 ohms.
Quasi-static C-V employs a DC measurement technique using two 4200-SCS Source Measure Units (SMUs) with two 4200-PA preamplifiers. The SMUs are used to source a current to charge the capacitor, and then to measure the voltage, time and discharge current. The 4200-SCS software includes test programs and formulas to extract common C-V parameters.
Ultra-Fast I-V Modules
Each Model 4225-PMU module provides two channels of integrated sourcing and measurement but occupies only a single slot in the Model 4200-SCS's nine-slot chassis. Unlike competitive solutions, each channel of the Model 4225-PMU combines high speed voltage outputs (with pulse widths ranging from 60 nanoseconds to DC) with simultaneous current and voltage measurements. Each 4200-SCS chassis can accommodate up to six Model 4225-PMU modules, for a maximum of twelve ultra-fast source and measure channels.
The Model 4225-PMU can be used to perform three types of ultra-fast I-V tests: Pulsed I-V, Transient I-V, and Pulsed Sourcing. Pulse and transient measurements add a time domain dimension to your analysis and allows for dynamic characteristics to be explored. Using pulsed I-V signals to characterize devices rather than DC signals makes it possible to study or reduce the effects of self-heating or minimize current drift due to trapped charge. Pulsed sourcing can also be used to stress test a device during reliability cycling or program & erase memory devices.
Remote Amplifier/Switch Units
The low current measurement capabilities of the Ultra-fast I-V module can be extended by adding the 4225-RPM. Additionally, the RPM acts as a multiplex switch, allowing you to automatically switch between SMUs, C-V or Ultra-fast I-V modules.
One of the most difficult problems when making I-V, C-V and Pulsed I-V measurements is that the cables required for each measurement type are fundamentally different. Guarding is necessary to achieve low current I-V measurements, which makes triaxial cables necessary. C-V measurements use four coaxial cables with the outer shells connected together. Pulsed measurements require the highest bandwidth of the three measurement types, so the cable must have a characteristic impedance that matches the source impedance to prevent reflections. Multi-Measurement Performance Cables (MMPC) simplifies switching between DC I-V, C-V, and pulsed I-V testing configurations. No matter what type of measurement is being made, you won’t have to change the probe manipulator cabling just move the cables from one instrument module to another. In addition, you can change the setup while the probe needles stay in contact with a wafer, reducing pad damage and maintaining the same contact impedance for all three types of measurements. MMPC Cables are available for select Cascade Microtech, Suss, Lucas Signatone and Wentworth probe stations.
The 4200-SCS can control external equipment such as an automated or semi-automated probe stations, temperature controllers etc. Probe drivers are supplied with the 4200-SCS for select Cascade Microtech, Suss, MicroManipulator and Signatone probe stations.
Device Under Test (DUT)
The 4200-SCS is capable of testing many types of non-volatile memory devices such as: