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MRAM is developing the next generation of embedded devices that support AI, IoT and advanced networking technologies; in the data center, edge and endpoint. In addition, stand-alone MRAM has become an important nonvolatile cache and buffer for many applications. Providing MRAM for all of these applications requires good MTJ design and testing in a production environment. Everspin's knowledge and experience in magnetic memory design, manufacturing and delivery to related applications is unique in the semiconductor industry, for automotive, industrial and military. Cloud storage and other industries provide a large number of reliable high-quality MRAM, STT-MRAM memory chips. Everspin Tier 1 Distributor Next, we introduce Everspin MRAM device testing.

ISI has long experience in MTJ device design and factory testing to meet MRAM development and production test requirements. They are also creating new testing and production tools to help MRAM succeed. See why they should be MRAM test partners.

In addition to specialized products for hard disk head production testing, ISI was the first company to manufacture wafer-level testers for the MRAM industry and probably has the largest STT-MRAM wafer-level tester installation base. Their long experience in the hard disk head industry gives them experience in MTJ testing, which they bring to the burgeoning MRAM testing industry.

The WLA3000 STT-MRAM wafer-level analyzer, the third generation pulse generator, is equipped with its proprietary probe card interface, which generates programmable pulses as low as 5 nanoseconds, enabling ultrafast measurements of multichip assemblies in situ after pulse generation. The 4-point and 2-point venous/right ventricular testers provide pulse and DC measurements up to 3K oersted in-plane and 5K oersted perpendicular to the plane. The machine is capable of operating at a field angle of 360 degrees and temperatures up to 150 degrees with a hot chuck option. The upcoming fourth generation system includes further enhancements to these specifications, including pulse widths as low as 2 nS and vertical fields as high as 15K oersted.

In addition, they can provide thin film reliability testing, including breakdown voltage, endurance, and write probability, as well as read interference measurements, and their thermal ferromagnetic resonance (FMR) characteristics (using RF preamplifiers connected to their RF probe assemblies) can be used for process control and device development. Figure 1 shows an ANSI wafer-level quasi-static tester.

Figure 1. ISI WLA 3000 wafer level quasi-static tester

ISI can be set up with EG, TEL, and Accretech detectors (shown above), and can be configured for almost any other detector. Their electronics and test software are independent of wafer detectors, and their test heads can be mounted on any detector. A simple cantilever probe card can be used to provide multi-device testing capability on 200 or 300 mm wafers.

ISI's approach is to develop their own proprietary front-end circuits that perform pulse and measurement operations on MTJs. Figure 2 shows pulse samples from proprietary ISI pulse channels with little overshoot.

This proprietary design not only provides specific test functionality for the MRAM industry, but is unique to the industry, with ISI's fully integrated front-end providing extremely fast write/read cycle measurements, resulting in extremely high measurement performance such as bit error rates.

Figure 2 shows the error probability for pulse amplitude. These tests were configured to run 105 write/reset cycles for each data point on the curve, but the total test time for the entire curve was still below 3.2 s.

Figure 2. Measurement of Error Probability vs. Pulse Amplitude

ISI has an aggressive roadmap for future MRAM testing and other production tools. A fourth generation ISI pulser module is being developed and external pulser integration is being developed for the next generation of spin orbit torque (SOT) devices to replace fast sram memory.

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