Modular Instruments Address IC Test

PXI, PXIe, and AXIe—from per-pin parametric measurement units (PMUs) to RF/microwave instruments—are making inroads in the semiconductor test space as vendors introduce modules suitable for IC test.

Brandon Brice, high-speed digital I/O product manager at National Instruments (NI), highlighted the challenges driving increasing acceptance of modular instruments in IC test applications: “As the complexity of semiconductor chips continues to grow, test equipment must scale accordingly, which consequently can drive cost upwards.” Evidence of the need to scale and the attendant challenges of that need, he said, “can be seen clearly in the expensive add-on options for big iron testers for RF and mixed-signal capabilities.”

Open, Flexible Architectures

Chris Ziomek, president of ZTEC Instruments, commented, “Modular instruments, especially PXI and PXIe, are well suited to IC test applications because they are based on open-standard, high-performance computing architectures. This combination creates a marketplace where many instrument vendors and test-system suppliers drive innovation.”

According to Ron Williamson, vice president of sales for worldwide semiconductor test at Aeroflex, “The key benefits of a modular solution are price/performance, scalability, flexibility, and investment protection.” Mike Dewey at Geotest-Marvin Test Systems agreed that flexibility is a key benefit, noting that PXI offers a wide range of instruments coupled with the ability to use a variety of software environments. In addition, Dewey said, modular systems can be upgraded as instruments are introduced, and they tend to offer lower costs compared with a closed system.

“A natural side effect of the vast PXI and AXIe ecosystem is intense competition,” said Williamson, adding that the competition “drives price/performance to levels not achievable in the closed-architecture big iron ATE market. As a result, customers enjoy a range of scalability and vendor flexibility that is not possible working with closed proprietary architectures.”

Added Ziomek, “Open-market competition enables faster time to market for new technology, affordable scalability, flexibility, and future upgradability. As a result, IC manufacturers are not locked into proprietary technology and a single ATE supplier.”

Specific Instruments

Aeroflex offers a variety of modular instruments based on industry-standard PXI and AXIe form factors that address semiconductor test. Williamson said the products are particularly suitable for the wireless cellular and connectivity semiconductor test markets. The RF, digital, and device power supply instrumentation available in the PXI form factor includes the 6- to 13-GHz vector signal analyzers (VSAs), 6-GHz vector signal synthesizers, bidirectional VSAs, and RF muxes, switches, combiners, and noise sources.

Figure 1. AX518 AXIe/PXI System
Courtesy of Aeroflex

As for AXIe instruments, Aeroflex offers an AXIe interface that incorporates control-bit drivers for load-board relay control, user power supplies, an I2C bus, and triggering. The company also provides a 48-channel, 400-MB/s, 32-MB memory per-pin digital subsystem and a 12-channel, 21-V/1.2-A 4-quadrant device power supply in the AXIe format.

In addition, Aeroflex markets the AX518, an integrated five-slot AXIe/18-slot PXI system (Figure 1).

Geotest offers a variety of PXI products for semiconductor test, including user power supplies, digital instruments with per-pin PMU (Figure 2), arbitrary waveform generators, digitizers, and user-programmable FPGA cards. “Our GX5290 Series of digital instruments has specific features suitable for IC test,” Dewey said, citing deep memory, real-time compare, and software tools for importing digital test vectors. “Our GX5295 also includes a PMU per-pin, which makes it ideal for DC parametric test and functional test,” he said. “All dynamic digital cards also offer high-channel-count (32) supporting up to 512 channels in one chassis. Our static digital card can provide up to 128 channels, saving slots and offering high channel density.”

Figure 2. GX5295 PMU PXI Card
Courtesy of Geotest-Marvin Test System

Geotest also offers a line of switching cards, but, said Dewey, the cards do not find widespread use in semiconductor test where most of the switching tends to be done on the load board. “We also have a standards card that can be used for in-system recertification of baseband instrumentation,” he added, “and we offer high-power 3U and 6U PXI chassis to accommodate high-channel-count digital configurations.” Dewey said Geotest’s modular products for semiconductor test address digital, mixed signal, and RF for ICs, SoCs, hybrid modules, and SiPs.

ZTEC also addresses RF test in the semiconductor space. Said Ziomek, “We offer numerous digitizers, arbitrary waveform generators, and RF test equipment well suited for semiconductor test.” He cited in particular the 6-GHz ZT8651 VSA and the ZT8751 6-GHz Vector Signal Generator, adding, “The combination of these two instruments provides a complete RF and mixed-signal test suite for semiconductor RFIC test applications.”

Ziomek summarized ZTEC’s offerings: “Our instruments have combined analog and RF capabilities, and our customers use these instruments in RF and analog/mixed-signal test applications. The DUT often is an RFIC used within radio circuitry for wireless communications, such as a power amplifier, radio transceiver SoC, or modulator/demodulator.”
NI provides an array of instrumentation for semiconductor test, said Brice, including high-speed digital instrumentation, high-precision source-measure units (SMUs), RF instruments, and instruments for high-dynamic-range audio measurements. “Recently,” he said, “NI has further increased its semiconductor applicability with a high-speed digital I/O module with per-pin parametric measurement unit (PPMU) capability.”

Brice said the PXI form factor and compact size combined with the hardware integration capabilities of NI LabVIEW software provide a flexible test platform suited to meeting the challenges faced by semiconductor design and test engineers. Compared with standard ATE solutions, he said, PXI allows for more customization regarding hardware and software.

Brice added, “An often overlooked part of a semiconductor test system is the test-development time that goes into the characterization and production test development process.” NI, he said, lowers development times during this process by providing tools such as NI TestStand ready-to-run test management software, which is designed to help engineers develop automated test and validation systems faster. In addition, he said, NI LabVIEW system design software gives engineers and scientists the ability to create and deploy measurement and control systems through hardware integration.

Putting Modular Instruments to Work

Figure 3. PXI Platform for Analog Devices’ MEMS Test
Courtesy of National Instruments

Brice cited some specific examples of his company’s instruments serving in semiconductor test applications (Figure 3). He said engineers at Analog Devices found that “by choosing the PXI platform over a traditional big iron solution for their MEMs production test, they were able to lower cost, reduce their footprint, and lower power consumption without sacrificing performance” as described in a case study.¹

In addition, Brice said, by adopting the PXI platform, ST-Ericsson lowered the cost and improved the test time of an RFIC test system by up to 15x in some cases.² “NI is dedicated to ensuring that we continue providing hardware and software tools, such as new PXI instrumentation and NI TestStand software, which allow for automated sequencing through multiple tests and aid engineers in keeping up with the ever-evolving demands of the semiconductor industry,” he said. “While low test times are always ideal, engineers need to ensure that they are not sacrificing performance,” he added, saying that NI provides measurement capability ranging from 7½-digit DC to 14-GHz RF on multiple channels “all densely packed into a modular platform.”

As yet another example, Brice said, “TriQuint Semiconductor was able to leverage the PXI platform to reduce the characterization time of complex cellular power amplifiers while reducing equipment cost, power consumption, and footprint without sacrificing measurement accuracy.”³

Software and Interface Hardware

Instrumentation is only part of a complete semiconductor test system. Other items to consider include software, manipulators, docking systems, probe towers, probers, and handlers. When asked whether ZTEC provides complete systems or individual instruments that customers can buy and configure their own IC test systems or depends on third parties to put the systems together, Ziomek said, “We see all three scenarios. At times, our customers or third-party integrators will select the chassis, controllers, interconnections, and software and add our instruments to enhance capabilities. Other times, customers require the test capabilities offered by our instruments and prefer that we deliver an integrated turnkey solution.”

As for software, he said, “RFIC device testing does not use standard data formats such as STIL and WGL. Instead, our customers need test software that performs the physical-layer compliance tests specified by the IEEE protocol standards. Our ZProtocol Software Toolkit provides the test waveform-creation and signal-analysis tools required for full RFIC protocol compliance testing.”

Said Williamson at Aeroflex, “In addition to individual instruments, Aeroflex offers integrated subsystems that can be used as upgrades to existing assets as well as complete systems.” He explained that every customer has a specific test strategy that differentiates its product cost, performance, and quality. “With this in mind,” he said, “Aeroflex has developed a full range of solutions from individual instruments, to subsystems, to complete systems.”

The subsystems and systems, Williamson said, “…come complete with high-level software and calibration, significantly simplifying the deployment of modular-instrument-based solutions into production test.”

Dewey at Geotest said, “Our TS-900 is a complete system with an integrated test receiver as well as the option to incorporate it with a manipulator for handler applications. We do have customers using our PXI modules to construct their own systems as well—typically for the verification test segment.”

Figure 4. TS-900 Chassis With Manipulator
Courtesy of Geotest-Marvin Test Systems

The TS-900 PXI platform works with Geotest’s ATEasy program development and test-executive suite and the DIOEasy graphical vector development environment, which supports vector formats including WGL and STIL. “However,” said Dewey, “we have users that may want to use their own language and tools, which can be done since we offer a range of drivers for supporting textual and graphical programming languages.” In addition to coming with ATEasy, the TS-900 features an integrated receiver interface and works with manipulators such as the Reid Ashman OM1000 Series (Figure 4).

And Brice at NI commented, “National Instruments is committed to empowering domain experts with highly customizable tools. We’ve seen numerous examples of customers creating their own IC test systems in both validation and production scenarios.”

For large-scale systems that require more integration, he said, NI leverages the National Instruments Alliance Partner Network (www.ni.com/alliance) whose members provide vertical expertise in various areas of semiconductor test. In addition, Brice said, “NI works closely with partners to provide customized solutions that integrate probing, handling, and fixturing. One example is NI’s collaboration with Teradyne Global Services Organization to provide a fully integrated test solution, including fixturing, that is scalable from characterization to production.”

Future Challenges

The modular approach can impose some limitations. Ziomek at ZTEC noted, “One complication created by open-standard modular test systems is that customers may require integration, application, and logistical support from multiple suppliers.”

Dewey at Geotest commented that, for example, if you are building your own system, you will need to deal with integrating a receiver interface and associated cabling issues. Furthermore, instrument drivers or test environments may not be optimized for fastest test throughput. But although some performance limitations may exist, Dewey said, “We see this gap closing.”

And Williamson at Aeroflex concluded that the company “…believes that the PXI and AXIe standards will be around for the next 20 years and provide an extremely safe platform investment.”

References

1. Beckford, W. et al., Analog Devices Reduces MEMS Test Costs With PXI and LabVIEW, National Instruments, Case Study.
2. Bertrand, S., ST-Ericsson Reduces Semiconductor Test Time 10X Using LabVIEW and NI PXI RF Instruments, National Instruments, Case Study.
3. Shipley, G., TriQuint Semiconductor Uses NI PXI and LabVIEW to Reduce Characterization Time of RF Power Amplifiers, National Instruments, Case Study.