Scalability, cost, flexibility drive innovation from DC to mmWave
Increasingly complex semiconductor devices are adding to the pressure to provide flexible, scalable, and low-cost solutions for semiconductor production. On the test front, companies are applying open-architecture PXI systems and software-defined approaches to achieve favorable results. Traditional ATE manufacturers are looking to fine-tune test strategies to optimize wafer-level and package test of SoCs, and they have looked to address the current “super cycle,” in which global demand for memory chips is skyrocketing. In support of the semiconductor test industry, companies are offering products ranging from Kelvin contactors to switching systems and power supplies. Still other companies are focusing on topics ranging from molecular beam epitaxy to scanning electron microscopy. SEMICON West, scheduled for July 10-12 in San Francisco, will offer companies an opportunity to elaborate on their products and technologies.
“One of the biggest challenges that semiconductor test customers face in the lab environment is addressing the growing test complexity of modern semiconductor devices in a scalable and cost-effective manner,” said David Hall, head of semiconductor marketing at National Instruments. “From IoT transceivers to RF front-end modules (FEMs) to power-management ICs (PMICs), each new generation of devices is more complex and requires more test cases. However, engineering organizations are still subject to aggressive time-to-market schedules and capital-equipment cost constraints.”
Hall explained that NI is addressing these challenges for its semiconductor test customers by helping them to standardize on automated test systems in the lab environment. “Although automated test has long been a facet of production test, many organizations are realizing better capital-equipment utilization and faster time-to-market by automating the characterization process in R&D,” he said.
Marvin Test Solutions’ customers continue to be challenged by the cost of test, according to Mike Dewey, director of marketing. “Device costs continue to decrease, which in turn requires that test costs decrease as well,” he said. “And while test methods such as multisite can help mitigate the cost of test, users are looking for a step-function reduction in costs. We see open- architecture solutions such as PXI offering the ability to significantly decrease test costs, particularly for MEMS devices such as sensors, where the use of high-cost ATE really doesn’t fit the cost model or test needs for these types of devices.”
He continued, “And in the RF space, there is a strong, emerging need to support 5G applications—which we believe can be cost-effectively addressed with open-architecture test platforms such as PXI.” He noted that MTS is focused on providing functional-test ATE for semiconductor, board, and system applications. “The PXI platform, with its wide range of instrument offerings both from MTS and other suppliers, allows MTS to support digital, mixed-signal, and RF test needs,” he said. “By focusing solely on ATE test needs, we are able to optimize our products and solutions for specific applications.”
System-level test (SLT) is yet another concept gaining significance. “While system-level testing is not a new test methodology, it is a methodology that is gaining more attention recently, particularly for production testing,” writes Anil Bhalla, senior marketing manager at Astronics Test Systems, in an article on p. 20 of this issue. “This is not only driven due to increased pressure to lower the overall cost of test (CoT), but also due to a number of technical drivers driven by lower technology nodes (which drive higher transistor count) and the increased complexity of devices.”
When it comes to cost of test, variables include capital cost, operating expenses, and real estate to accommodate the test equipment. These issues can be addressed with compact, comparatively low-cost systems. But also of significance is the test strategy, and test-strategy analysis has become increasingly important for finding ways to reduce test costs for SoCs, according to Randy Kramer, director of SoC Factory Applications Engineering for Teradyne. In a recent article,1 he commented that for multisite testing, CoT generally decreases as you add sites because the capital cost of the test cell is amortized over more devices being tested in parallel. At some point, you will add enough sites to fully use the available instruments in your system. Adding one more site will incur the cost of additional instrumentation, but then you can continue adding sites until the new instrumentation resources are fully utilized, at which point you can add still more instruments.
“However, there is a point where the CoT curve stops declining and can inflect and begin to increase as the site count continues to increase,” Kramer wrote. “This is primarily driven by the parallel test efficiency (PTE) of the test solution. PTE effectively measures the degree of true parallelism of test that is accomplished and is driven by the efficiency of the test-system hardware, software, and device test requirements.” He presented an example in which an 8-site implementation yields a lower CoT that a 14-site implementation.
“Standard ‘rules’ or ‘practices’ cannot be generally applied to reducing test costs across the total test flow of a semiconductor SoC device,” he concluded. “Every test flow is unique, and semiconductor manufacturers need to analyze each flow to identify additional strategies to continue to reduce the overall cost of test for shipping good devices to their customers.”
Semiconductor test products
According to Hall, NI serves a variety of test and measurement needs within the semiconductor test industry, ranging from ultraprecise DC measurements to mmWave measurements. In addition, NI’s products find use at multiple stages of product development, including precision wafer measurements, design validation test, and automated production test. “Although each of these applications requires increasingly accurate measurement technology, specific applications like semiconductor ATE introduce additional requirements,” he said. “In semiconductor ATE applications, engineers face a constant battle to reduce the cost of test through faster test times and highly parallel test processes. One of the benefits of NI’s software defined-approach to semiconductor ATE applications is that it provides engineers with the tools to optimize test sequences and even measurement algorithms to improve test throughput.” For example, he said, engineers frequently take advantage of NI’s user-programmable FPGA technology to accelerate measurement results.
Commenting on recently introduced products, Hall said, “NI continues to evolve our product portfolio to address the challenges of semiconductor test,” adding that one of the most recent products is a new solution for 5G NR testing based on NI’s RFmx measurement software and utilizing NI’s second-generation Vector Signal Transceiver (VST). “A key attribute of NI’s 5G NR test solution (Figure 1) is the support of up to 1-GHz instantaneous bandwidth—which enables engineers to test RF power amplifiers (PAs), front-end modules (FEMs), and transceivers under a wide range of waveform and carrier-aggregation conditions,” he said. “This solution enables engineers to reduce their time to market for 5G NR designs and expand test coverage from product characterization to automated production test.”
Hall cited NI’s software-defined approach to instrumentation as a key differentiator. “Using this approach, engineers are able to develop highly flexible test systems which can scale to both current and future test challenges. The recent release of NI’s 5G NR test solution is a prime example of NI’s flexibility, as the new 3GPP-compliant measurement software is a mere software upgrade for existing users of NI’s Vector Signal Transceiver. What’s more, the VST easily integrates with a wide range of modular instrumentation—allowing engineers to develop comprehensive automated test benches for a wide range of semiconductor components.”
He added, “One of the seemingly ‘hidden’ benefits of NI’s software-defined test approach is the smaller size and footprint of PXI modular instruments. On the surface, ‘tester footprint’ might not seem significant. However, when you consider the environment in which products are tested, from the R&D lab to the production floor, small physical size can often directly translate to cost savings. In some instances, customers who have adopted NI for semiconductor automated production test commented that the switch to NI even allowed them to delay expansion to a larger manufacturing test facility.”
PXI for functional test
Another company employing the PXI architecture for semiconductor test is Marvin Test Solutions. Dewey said the company’s PXI-based portfolio of products and systems offers users a flexible and open architecture for functional-test applications ranging from semiconductor device testing to complete system test. “Our software and hardware products are purpose-built solutions—designed for addressing specific functional-test needs,” he said, adding that the company’s digital and analog test products are designed specifically for ATE applications with a focus on offering compact, high-density, and high-performance test capabilities.
MTS has recently introduced a 4-channel PXI SMU that customers can use to test the DC parametrics of semiconductor devices. Its multichannel configuration supports multiterminal-device DC testing or multisite device testing. “The GX3104’s unique flex-power architecture offers users the option to configure the SMU as a 4-channel, 250-mA/channel SMU or as a single-channel 1-A SMU—providing test engineers the flexibility to support both high current or multichannel SMU applications with one module,” said Dewey. “Measurement functions are supported by 24-bit ADCs, and sourcing functions are supported by 18-bit DACs.”
He added, “The four channels are electrically isolated from the PXI power supply and share a common, isolated ground. In addition, all module power is provided by the PXI bus, eliminating the need for bulky, external DC power supplies.”
Commenting on the company’s TS-900 family of semiconductor test systems, Dewey said, “Features such as high channel count, PMU and timing per-pin capabilities, and comprehensive software tools for creating test programs are all features that are incorporated into our TS-900 product family and instrumentation. Similarly, the multichannel capability of our just-released GX3104 module offers the channel density and flexibility to support both DPS and SMU functionality.” (Figure 2) shows the TS-960 system with a manipulator from Reid-Ashman Manufacturing Inc.
Power supplies and core ATE
When asked what products AMETEK offers for semiconductor applications, James Schada, senior product manager for AMETEK Programmable Power, commented that the Sorensen SGX Series of high-power programmable DC power supplies, launched in March 2018, was designed to offer exceptional load and transient response as well as low noise. “In semiconductor fabrication, SGX Series power supplies are suitable for use in ion-implantation tools, he said. “With a full 15 kW available down to 20-V output in a 3U package, the SGX Series leads the industry in power density.”
He noted that a 5-kW power module is at the heart of the SGX Series (Figure 3), and from one to six modules can be configured in a single chassis to deliver from 5 kW to 30 kW. “Combinations of these chassis can be easily paralleled to produce power levels up to 150 kW,” he added. “Paralleled units operate like a single supply providing total system current. The SGX Series also features a touch-screen interface that allows users to control the supply intuitively.”
He said other SGX Series applications include burn-in, compliance testing, materials research, process control, battery charging, and product validation. They can also serve in rackmount ATE systems and automotive-electronics applications.
Schada also cited the water-cooled Sorensen ASD FLX Series DC power supplies, which feature a modular design that allows easy access and flexible voltage assignments. “The water-cooled design makes the ASD FLX Series ideal for harsh or demanding applications with stringent air-quality requirements, such as clean rooms or industrial environments that are dirty or potentially corrosive and damaging to air-cooled power supplies,” he said.
“Preventing equipment failures will always be a challenge in the semiconductor industry because of the high cost of equipment downtime,” Schada added. “The modular design of the ASD FLX Series makes it simple to service. The 3U chassis and lightweight, removable modules allow for uncomplicated one-person installation. The chassis can house three 10-kW modules. In addition, convenient rear panel dip switches make it easy to configure each module for the user’s desired voltage. This modular design provides n+1 redundancy, as well as a significant reduction in mean time to repair; faulty modules can be quickly swapped out for functional ones in the field.”
Jon Semancik, director of marketing for AMETEK VTI Instruments, commented that products from AMETEK Programmable Power and AMETEK VTI Instruments find use in a variety of applications, from semiconductor ATE to data acquisition. “AMETEK’s FlexSys series of common-core ATE solutions is the result of combining years of experience as a modular-instrumentation and power-supply manufacturer with that of a systems-integration service provider,” he said. “FlexSys integrated test systems incorporate pre-engineered building blocks at the core that can be easily tailored to meet specific application needs. Depending on the specific application requirements, FlexSys systems can integrate PXI Express and LXI modular instrumentation, AC/DC power sources, interconnect panels and wiring, racks, and enclosures.”
Testing WBG devices
Wide-bandgap (WBG) semiconductors represent an area of focus for Tektronix, according to James Yu, application engineer for the Keithley product line at Tektronix. “Wide-bandgap, high-power, transistor-based semiconductor wafers require high voltage/high current testing and traditional low-voltage/low-current measurement,” he said. “But because of their lack of switching capability, traditional semiconductor testers are not able to perform both of these tests. As a result, many customers are using a traditional tester for low-voltage/low-current testing and then must add another test stage and special instrument to perform the high-voltage/high-current test.” In contrast, he said, “Keithley’s S530-HV and S540 semiconductor parametric test systems provide both low- and high-voltage parameter testing with the same tester, probe card, and cabling.” (Figure 4) shows the S540 semiconductor parametric test system.
Yu noted that Tektronix provides an embedded discharge circuit. “The switch/cable/probe card can have a high voltage potential after high-voltage testing,” he said. “This charged potential can destroy other sensitive devices or be harmful to humans. Keithley’s high-voltage switch discharges automatically after any usage.” He said the equipment supports fully-automated, 3-terminal capacitance measurements to 3 kV to automatically measure the small-signal reverse-transfer capacitance (CRSS), small-signal input capacitance (CISS), and small-signal output capacitance (COSS) of power devices.
Semiconductor equipment in the news
Several semiconductor equipment makers have made news recently:
In December, Teradyne and Sigurd Microelectronics Corp., a provider of semiconductor IC assembly and test services based in Taiwan, announced the availability of new RF test services at Sigurd utilizing the Teradyne UltraFLEX test system with the UltraWave24 RF test option. The companies said the new capability will enable Sigurd to provide test services for 4G, wireless-networking, and IoT devices. Teradyne describes the UltraFLEX as a widely used solution for testing advanced RF transceivers, offering the accuracy and signal integrity necessary to increase device yield, reduce costs, and speed times to market.
Cohu Inc. in January announced that the company has secured a major European automotive customer for its MATRiX tri-temperature pick-and-place handler combined with its multibeam test contactors. Cohu said its MATRiX handler has a flexible test-site configuration that’s suited for a range of test applications, including analog ICs with short test times, automotive devices requiring accurate thermal control, small-pitch wireless-communication products, highly parallel microcontroller testing, and MEMS device testing.
Xcerra announced in January that it had completed a qualification at a major European IDM for a fully integrated and prevalidated test cell for barometric sensor test. The solution consists of a Multitest InStrip handler with an InBaro module, an LTX-Credence Diamondx ATE system, and Multitest contactors. In addition, Xcerra integrated a third-party pressure stimulus as well as dedicated third-party interface boards.
Also in January, Boston Semi Equipment announced that it has started shipping units of its new strip load/unload module to a top 10 semiconductor manufacturer. The automation modules handle magazines containing strips holding semiconductor devices. The freestanding modules dock to strip-processing equipment via a SMEMA-compliant interface. Operators set up and control the modules using a color touch-screen monitor.
And Keysight Technologies in January announced the third generation of its P9000 Series massively parallel parametric test system. The system accelerates the fast ramp of new technology and reduces the cost-of-test in the development and manufacturing of advanced semiconductor logic and memory ICs, the company said, adding that the third-generation system includes a new per-pin parametric test module—the Keysight P9015A—to further shorten the time needed for measuring capacitance due to multilayer interconnection and new device structures. (Figure 5) shows the system with an ACCRETECH UF3000EX wafer-probing machine.
Veeco Instruments Inc. announced that in February it completed installation of its 100th automated Molecular Beam Epitaxy (MBE) system. The installation of Veeco’s GEN10 MBE system (Figure 6) at Silanna Semiconductor PTY Ltd. in Australia marked this company milestone. Silanna is using the GEN10 system for advanced oxide R&D for optoelectronic devices. Silanna also operates a Veeco Dual GEN200 MBE system for production of advanced nitride compound semiconductor devices including ultraviolet LEDs.
In March at SEMICON China, Thermo Fisher Scientific highlighted three new products: the Verios G4 extreme high-resolution (XHR) scanning electron microscope (SEM), which helps determine root-cause defects, yield losses, and process and product failures (Figure 7); the iCAP TQs inductively coupled plasma-mass spectrometer (ICP-MS), which enables measurement of low-level contaminants in the ultrahigh purity chemicals required for advanced semiconductor manufacturing; and the Hyperion II nanoprober, which makes direct electrical measurements of individual transistors. The company described the Hyperion II as the only commercially available nanoprober based on an atomic-force microscope (AFM), which eliminates the vacuum requirements and e-beam/sample interactions of SEM-based nanoprobers.
Also in March, Xcerra’s Multitest division announced that its ecoAmp Kelvin contactor (Figure 8) successfully passed an in-depth evaluation phase at a major IDM. Based on the performance, which was demonstrated in a high-power application, the customer decided to make the Multitest ecoAmp Kelvin contactor its strategic test-interface product for existing and future high-power test applications at high-volume production.
In April, Advantest Corp. introduced its T5503HS2 memory tester, which the company called the industry’s most productive test solution for the fastest memory devices available today as well as next-generation, super-high-speed DRAMs. The new system’s flexibility extends the capabilities of the T5503 product family in the current “super cycle,” in which global demand for memory chips is skyrocketing, Advantest reported.
Cohu and Xcerra in May announced they have entered into a definitive merger agreement pursuant to which Cohu will acquire Xcerra for a combination of cash and stock. Cohu’s pending acquisition of Xcerra is not expected to impact customers’ day-to-day operations, according to a letter from Xcerra to its customers. “The goal is to make this acquisition process seamless to your operations and your customer experience with Xcerra as we work to build a new company focused on increasing your yield, reducing your cost of test, and accelerating your time to market,” the letter said.
Test at SEMICON West
You can expect more semiconductor equipment news at SEMICON West, scheduled July 10-12 in San Francisco. Several companies have already commented on what semiconductor test products they plan to exhibit. For example, sibling companies Pickering Interfaces and Pickering Electronics will be on hand to highlight switching systems and reed relays, respectively.
Bob Stasonis, director of sales and marketing at Pickering Interfaces, said the company will exhibit its latest product aimed at the semiconductor industry, the 65-2xx family of LXI scalable matrices (Figure 9). “It is a modular chassis, but not PXI,” he said. “Unlike PXI, the plug-in cards have rear-access analog buses allowing the user to create larger matrix configurations by merely installing additional modules in the chassis—no external interconnection cabling is needed. It is designed to handle the increasing I/O count of today’s advanced chips. It also features a sequencer option that greatly speeds up the switching patterns needed for test.”
In addition to the 65-2xx family, he said, Pickering Interfaces will showcase its latest PXI, PCI, USB, and Ethernet LXI switching solutions, ranging from general-purpose switching systems to microwave switch modules. He cited the company’s sequencer and speed of switching as unique features supporting semiconductor test applications.
Graham Dale, technical director at Pickering Electronics, said his company at SEMICON West will exhibit for the first time its new Series 124 reed relay (trademarked 4mm2), which stacks on a 4-mm x 4-mm pitch while switching up to 5 W, 0.5 A (Figure 10). “This new relay is pin-compatible with the established 1-A Series 120 but with the profile height reduced to only 9.5 mm,” he said. The Series 120 debuted at last year’s SEMICON West; it switches up to 1 A at 20 W.
Dewey at MTS said his company will showcase its PXI-based TS-960 test system for digital and mixed-signal test applications as well as its MTEK (Marvin Test Expansion Kit) platform, which offers users the ability to augment existing legacy semiconductor test platforms with advanced digital, RF, and analog test capabilities. “The MTEK platform is a cost-effective, PXI-based test solution that offers modern instrumentation with advanced specifications—extending the life and capabilities of legacy ATE,” he said.
And Astronics Test Systems can be expected to highlight its ATS 5034 system-level test system. At last year’s International Test Conference in October in Fort Worth, the company introduced an expansion of the ATS 5034 that features new semi-automatic solutions in a scalable system, supporting lower volume, higher mix, small lot, and/or longer test-duration options for semiconductor manufacturers. The system’s massively parallel approach, with up to hundreds of DUTs tested simultaneously, has produced excellent results, writes Bhalla in this issue.
“One of the big focus areas that NI will be addressing in the remainder of 2018 is an initiative to refine the software experience of NI’s automated test tools,” said Hall. “More specifically, some of NI’s newer software tools will allow engineers to more easily develop and debug automated test sequences. This is part of a long-standing initiative to allow engineers to better integrate the characterization test and production test workflows through a set of interoperable products—a proven technique to accelerate time-to-market.”
Yu at Tektronix said the company sees an increased interest in high-voltage wafer-level testing to detect process problems early in the workflow, “…thus improving yields at the packaged-part level and improving overall profitability.” High-voltage wafer-level testing is especially important for power, automotive, and wide-bandgap applications, he said.
Commented Dewey at MTS, “We will continue to address those test needs that can benefit by adopting an open architecture. Additionally, we see significant opportunities in help customers extend the life of current ATE by augmenting their test platforms with cost-effective, add-on test options.”
- Kramer, Randy, “Test strategy implications on cost of test,” EE-Evaluation Engineering, February 2018, p. 20. https://www.evaluationengineering.com/test-strategy-implications-cost-test
For more information:
AMETEK Programmable Power
Astronics Test Systems
Boston Semi Equipment
Marvin Test Solutions
Reid-Ashman Manufacturing Inc.
Thermo Fisher Scientific