Keithley Enhances Automated Characterization Suite for WLR Tests

Keithley Instruments, Inc. (NYSE:KEI), a leader in solutions for emerging measurement needs, has enhanced its Automated Characterization Suite (ACS) software to include optional wafer level reliability (WLR) test tools for semiconductor reliability and lifetime prediction testing applications. Version 4.0 builds on the ACS software’s existing single- and multi-site parallel test capabilities, adding a database capability, as well as software tools and optional licenses for the new Reliability Test Module (RTM) and ACS Data Analysis capabilities. Together, the new Reliability Test and Data Analysis tools allow ACS-based test systems to produce lifetime predictions as much as five times faster than traditional WLR test solutions. By accelerating WLR testing during the technology development, process integration, and process monitoring phases of creating new integrated circuits, ACS systems can reduce time to market for new products significantly.

Keithley Automated Characterization Suite 4.0ACS-based test systems have the hardware configuration flexibility necessary to address a wide range of semiconductor characterization needs at the device, wafer, or cassette level. They can incorporate either Keithley’s Series 2600 System SourceMeter® instruments, the company’s Model 4200-SCS Semiconductor Characterization System, or both.

True Parallel WLR Test Delivers Critical Device Information Sooner
Wafer Level Reliability (WLR) testing is used to predict reliable lifetimes for semiconductor components such as transistors, capacitors, and interconnects. These tests, performed on on-wafer test structures, can reveal critical reliability information during research and development; similar tests are used to monitor the consistency of manufacturing processes once devices go into full production. WLR testing is designed to accelerate failure mechanisms by stressing devices with elevated levels of voltage, current, and/or heat. To determine acceleration factors, a set of devices will undergo various levels of stress over time. Unlike traditional WLR systems, which stress-test one device at a time, the new WLR tools in the ACS software allow testing multiple devices in parallel while applying different stress conditions (voltage or current) to each device.

New technical challenges, including the continuing scaling of film thicknesses and the increasing importance of device reliability in high temperature applications, have made the need for parallel WLR testing more critical than ever. Parallel testing approaches allow engineers to extract the lifetime acceleration factors by testing a single structure made up of several devices. Many of the test structures already used in traditional WLR testing are compatible with parallel test techniques, making it possible to increase system throughput by a factor of 2–5x without the need to modify their test structures. However, this level of true parallel WLR testing is only possible with test system architectures in which each pin has its own dedicated Source-Measure Unit (SMU).

ACS-based test systems configured with multiple Series 2600 System SourceMeter instruments are the only commercial solutions capable of providing this level of SMU-per-pin testing flexibility. ACS simplifies networking Series 2600 instruments into a highly flexible and dynamically reconfigurable array of SMUs by connecting their on-board Test Script Processors (TSP®) via a TSP-Link® virtual backplane. This system architecture makes it possible for the application to instruct the SMUs either to work together as a large, tightly coordinated group or as several smaller groups that work in concert to test several devices. The Series 2600′s on-board processors and virtual backplane combine with these instruments’ best-in-class measurement speed to provide precision source/measure timing, which is critical to capturing the details of fast-moving breakdown events. ACS-based systems can be configured with anywhere from two to more than forty high power Keithley SMUs, which can source and/or measure 200V or 1.5A.

Uncomplicated Test Setup and Analysis
The new Reliability Test Module (RTM) option available with ACS 4.0 is a powerful stress/measure sequencing tool that provides an interactive interface for testing device reliability (HCI, BTI, etc.), gate oxide integrity (TDDB, JRAMP, VRAMP, etc.), and metal interconnects (EM). The module’s flexible test sequencing capabilities support pre- and post-testing, as well as intra-stress testing and stress monitoring. It’s designed in compliance with JEDEC standard test methodologies (such as JESD61 and JESD92), but it also offers the flexibility needed to create new test routines quickly to characterize advanced nanoscale structures.

During reliability testing, the raw test data can be logged to the database and/or plotted in real time. These real-time plots offer reliability engineers a “sneak peek” at a test’s outcome before its completion, which allows them to judge whether time-consuming tests are on track to deliver meaningful results. The optional Data Analysis module imports test results from the database, and then applies the rules and models defined in the analysis project the reliability engineer selects. Once an analysis process has been defined, it can be reused to analyze newly imported data easily. For those who are new to WLR testing, this option eliminates the need to create custom analysis software and to manipulate data manually with spreadsheets. However, for those who have already developed their own custom analysis software that they wish to continue using, ACS 4.0 provides software tools that simplify extracting data from the database.

The Data Analysis option supports standard analysis techniques like normal fitting, acceleration, and distribution models, including Lognormal and Weibull. Models can be easily reorganized and edited to create new analysis processes. A built-in scripting language also lets users define their own models easily. The reliability formulator tool provides a variety of advanced functions, including modeling, line-fitting, standard parametric extractions, and standard math functions that allow custom data manipulation.

Offline Test Project Development and Data Analysis
Both the ACS 4.0 test executive and the Data Analysis option allow for offline installations (that is, on a PC not linked to the source-measure hardware). For test environments where multiple users or departments share access to the same ACS hardware, this allows convenient access to the software tools for building test sequences and reviewing and analyzing data offline without tying up the test system’s workstation. When purchasing the Data Analysis option, extra licenses are available to allow multiple offline installations; the ACS test executive can be installed offline without an extra license.

Flexible Hardware Configurations
ACS 4.0 software can be used to drive test systems made up exclusively of Series 2600 System SourceMeter instruments, just the Model 4200-SCS Semiconductor Characterization System, or a combination of both. With the unique capabilities of each integrated into a single system, reliability engineers can bring together the advantages of high speed, SMU-per-pin flexibility (Series 2600) and the high power pulse I-V testing capability (Model 4200-PIV) needed to characterize interface traps and isothermal behaviors, which are common in new gate stack technologies. Typically, Model 4200-SCS applications are found in the reliability lab, while the Series 2600′s high speed makes these instruments invaluable in process development, process integration, and process monitoring applications. An ACS-based system that combines both instrument types simplifies a device’s transition from the lab to the fab by allowing engineers to use the same characterization tool in both environments.

Keithley’s ACS-based test systems are designed to interoperate with a wide range of hardware components typically used in WLR testing, including popular wafer probers and probe card adapters, hot chuck controllers, single- and multi-site probe cards, and high temperature probing options.

For More Information
Pricing for Keithley’s ACS integrated test systems is based on the particular configuration and licensing and customization options desired. Systems and software upgrades are available immediately. To learn more about the latest enhancements to ACS-based integrated test systems or any of Keithley’s semiconductor test solutions, call 800-688-9951. Visit http://keithley.acrobat.com/acswlr for more information.

About Keithley Instruments, Inc.
With more than 60 years of measurement expertise, Keithley Instruments has become a world leader in advanced electrical test instruments and systems from DC to RF (radio frequency). Our products solve emerging measurement needs in production testing, process monitoring, product development, and research. Our customers are scientists and engineers in the worldwide electronics industry involved with advanced materials research, semiconductor device development and fabrication, and the production of end products such as portable wireless devices. The value we provide them is a combination of precision measurement technology and a rich understanding of their applications to improve the quality of their products and reduce their cost of test.