The beauty of modular instruments is their ability to be upgraded, expanded, or otherwise improved without investing in a completely new instrument. Keithley’s Model 4200-SCS semiconductor characterization system is such an animal. The latest addition to the analyzer is the Model 4225-PMU, an ultra-fast current-voltage (I-V) module. This option integrates ultra-fast voltage waveform generation and current/voltage measurement capabilities into the 4200-SCS’s arsenal.
Why do engineers characterizing devices and new materials and processes need ultra-fast IV? It’s because three types of measurements are required to fully characterize devices, materials, and processes: precision dc I-V, ac impedance, and ultra-fast or transient I-V. In adding the 4225-PMU option to the 4200-SCS system, Keithley has rounded out the instrument’s capabilities. The option enables the characterization system to serve emerging applications from high-k dielectrics to silicon-on-insulator (SOI) in small-scale CMOS, flash memory, or phase-change memory.
Keithley’s goal for the 4200-SCS system was to make characterization easy through use of a GUI-based, point-and-click interface. In adding the ultra-fast I-V testing, the same goal applied. Further, Keithley hoped to make the 4225-PMU option look, act, and feel as easy to use as an ordinary high-resolution source-measure unit (SMU).
Achieving these goals required making the module’s measurement range very broad, with similarly broad dynamic range. It also required simplification of the interconnect. The result was extremely fast measurements with correspondingly high resolution (see the figure). Current resolution ranges from 1 A to 1 pA. While the previous-generation 4200-SMU fast I-V module permitted measurement speeds as fast as 10 ms, the 4225-PMU can make some higher-current measurements as fast as 10 ns. It achieves all this while staying as close to the Johnson noise limit as possible.
Each 4225-PMU module provides two channels of integrated sourcing and measurement but takes up only one slot in the nine-slot mainframe chassis that houses the system. Each chassis can accommodate up to four modules for a maximum of eight ultra-fast source/measure channels. Each channel combines high-speed voltage outputs (with pulse widths ranging from 60 ns to dc) with simultaneous current and voltage measurements.
The module provides high-speed voltage pulsing with simultaneous current and voltage measurement, at acquisition rates of up to 200 Msamples/s with 14-bit analog-to-digital converters (ADCs), using two converters per channel (four per card). Users can choose from two voltage-source ranges (±10 V or ±40 V into 1 mΩ) and four current measurement ranges (800 mA, 200 mA, 10 mA, 100 µA).
Each 4225-PMU module can be equipped with up to two optional Model 4225-RPM remote amplifier/switches, which provide four additional low-current ranges. They also reduce cable capacitance effects and support automatic switching between the Model 4225-PMU and other SMUs installed in the chassis.
The 4225-PMU can generate four types of sweeps: linear sweep, pulsed, arbitrary waveform, and what Keithley calls Segment ARB, which simplifies creating, storing, and generating waveforms comprising up to 2048 user-defined line segments for exceptional waveform generation flexibility.
An optional multi-measurement performance cable kit connects the Model 4200-SCS to a prober manipulator, simplifying switching between dc I-V, C-V, and ultra-fast I-V testing configurations, eliminating the need for recabling, and enhancing signal fidelity.
The Model 4225-PMU costs $19,000. A typical configuration of one Model 4225-PMU and two Model 4225-RPMs costs $25,000. The Model 4220-PGU (voltage source only) costs $13,000. All three products will be available beginning in May 2010.