Cold Technology is Heating Up
The use of on-wafer superconducting materials, other novel materials and traditional semiconductors at cryogenic temperatures (below about 123K, or -150°C) has risen markedly in recent years. Inventive new sensors take advantage of unique material properties at very low temperatures to detect a wide variety of physical phenomena such as infrared radiation, magnetic fields, x-rays, and more, for application in many fields such as health care, defense, industrial automation, and astronomy. Recent developments in the field of quantum computing and superconducting logic promise bold energy and performance gains in the future of computing. And many more cryogenic applications and devices are in the pipeline.
FormFactor has played an active role in bringing these technologies to market, producing high-performance cryogenic and vacuum probe systems since 2000 with unmatched automation capabilities to support activities from academic research to industry production.
Cold Image Sensors See Heat Best
High-performance thermal imaging is widely used today in surveillance/security, night vision, remote sensing, meteorology, military threat and target detection, body heat analysis, astronomy, and more. These systems use FPAs (focal plane arrays) based on cooled IR sensors. Cryogenic environments reduce thermal noise so that these detector arrays can deliver improved resolution and sensitivity.
Cooled IR sensors are built from different materials to target various wavelength ranges from the near infrared (NIR) through long wave infrared (LWIR), including silicon, numerous III-V compounds (InGaAs, InSb, InAsSb, InAs/GaSb, etc.), often designed as quantum well photo detectors, MCT (mercury cadmium telluride), and superconducting photon detector technologies including YBCuO, GdBO3, MgB2, and more. Testing these low-temperature technologies on wafer requires a cryogenic probe system.
Cryogenic Circuitry Could Revolutionize Computing
Industry giants and startups alike are investing heavily today in a new use for superconductor technology – tackling the enormous challenges which threaten the future of the computing infrastructure needed to support our growing demand for data, computational power, and interconnected devices. Quantum computing, (based on qubits) promises to empower a whole new era of artificial intelligence, complex system optimization, molecular modeling for medicine, cryptography, and more. Cold superconducting CPUs using RSFQ (rapid single flux quantum), RQL (reciprocal quantum logic), or similar new logic families promise to slash the huge energy and heat issues limiting the growth and location of HPC (high performance computing) supercomputers and hyperscale data centers.
These new cryogenic processors need memory, and to maintain their energy benefits the memory systems must also be cold. Superconducting memory is years away; however, studies show that traditional CMOS DRAM structures can be very effectively used at cryogenic temperatures such as 77K or less than 7K. Cryogenic wafer testing is required to tune the process and qualify memory components for use at these temperatures.
Cryogenic Challenges Require Specialized Probe Systems
The cryogenic test environment begins with a vacuum chamber to provide a suitably sealed and evacuated environment. A cryostat using liquid nitrogen or liquid helium, or other means of refrigeration, lowers temperatures to 77K or below; resistive heaters, cryogenic grade temperature sensors and a temperature controller complete the temperature regulation. Signal feedthroughs, optics for cameras, and probe positioner controls all require special considerations for access to the extreme vacuum/cold environment. Safety, vibration, and sample mounting also present new challenges for vacuum/cryogenic conditions. Condensation and particulates are also unique complications when temperatures drop. Even the probes must be designed for use at cryogenic conditions. Finally, although many solutions are available for single small diced samples with just a few signals, process and product qualification requires a higher class of tools. High volume testing demands a large chamber for full wafer samples, multi-channel cryogenic probe cards, a software-controlled wafer stage for step-and-repeat testing across the wafer surface, and other capabilities to maximize test throughput.
High Throughput Tools Lead the Industry
FormFactor is ahead of the pack for high-throughput cryogenic wafer test, with this unmatched combination of powerful features:
- Step-and-repeat automation with programmable, motorized XYZΘ stage.
- Automatic camera-based alignment adjustments at each step.
- Up to 8 easily positioned and very stable cryogenic probes for DC, RF, and optical signals – and probe cards for even higher signal count.
- Sample sizes from fragments up to full 200mm wafers (300mm option available).
- Wafer exchange without disrupting probes or probe cards.
- Programmable, motorized positioning of multiple black-body radiation sources, microscopes, and other equipment
High test throughput enables our customers to move from lab concepts to device characterization to design debug to high-volume engineering/production test. FormFactor’s lineup includes multiple size and automation levels, and flexible/customizable configurations.
Sophisticated Tools Simplify Cryogenic Test
The Cryogenic Tool is a Velox application that enables precise on-wafer measurements in extreme environments by controlling vacuum pump and coolant parameters. It has been developed for cryogenic probe systems that enable testing of cooled IR sensors and cutting-edge technologies that require cryogenic temperatures. It supports auxiliary functions like automatic refill of the liquid nitrogen dewars and automated swapping of the IR radiation sources (blackbodies).
Graphical interface of vacuum/cryogenic probe station
Real-time display of process parameters
Semi-automated process tools
Extreme Environments Demand Probe Expertise
On-wafer test is ultimately about the measurements. FormFactor’s reputation as an analytical probing leader extends to cold conditions with a suite of high-performance probes optimized for cryogenic testing. These products make it possible for test instruments to deliver precise stimuli to test devices and collect accurate data across a comprehensive range of application requirements .