[Future Testable] Series 2: Basic Research and Performance Research Test Scheme of Memristor Unit

[Future Testable] Series 2: Basic Research and Performance Research Test Scheme of Memristor Unit

Memristor is called memristor in English, represented by the symbol M. It constitutes four basic passive circuit devices with resistance R, capacitance C and inductance L. It is the link between magnetic flux and charge. It has the performance of both resistance and storage. It is a new generation of high-speed storage unit, usually called resistive random access memory (RRAM).

Important application areas of memristors that have attracted much attention include: nonvolatile memory, logic computing, and brain-inspired neuromorphic computing. These three completely different but interrelated technical routes provide a feasible route for developing a new computing architecture that integrates information storage and processing and breaks through the bottleneck of the traditional von Neumann architecture.

While memristor research continues to achieve new results, multifunctional coupling devices based on memristors have also become a hot topic for researchers. These new coupling devices include: magnetic coupling devices, optical coupling devices, superconducting coupling devices, phase change memristor devices, ferroelectric coupling devices, etc.

1. Basic research and testing of memristors

Memristor research can be divided into three stages: basic research, performance research, and integrated research. This research method is applicable to resistive random access memory (RRAM), phase change memory (PCM), and ferroelectric random access memory (FeRAM). The basic research stage of memristors mainly studies the material system and physical mechanism of memristors, characterizes the parameters of memristors, and classifies memristors through hysteresis loops. The basic research tests of memristors include: DC characteristics, AC characteristics, and pulse characteristics tests.

Memristor DC characteristic test is usually combined with Forming, mainly testing the memristor DC VI curve, and using it to deduce important memristor parameters such as SET/RESET voltage/current, HRS, LRS, etc., which can be scanned unidirectionally or bidirectionally. Memristor AC characteristics mainly test the pinch hysteresis loop, which is the key to identifying the type of memristor. Memristor pulse testing can effectively reduce the impact of Joule heat accumulated in DC testing, and can also be used to study the impact of heat on device performance. As memristor characterization technology is developing towards extremes, the demand for picosecond pulse erasure and signal capture is becoming increasingly strong.

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2. Memristor performance research and testing

The memristor performance research and testing process is as follows:

The performance study of non-volatile memory is achieved by testing the number of cycles or endurance and data retention of the memristor. In the cycle number and endurance test, the resistance test is usually completed by a semiconductor parameter tester with a pulse function. Due to the large number of samples to be tested and the long time consumption, programming is required for automated testing. In extreme characterization cases, the SET/RESET pulse is generated by a high-speed arbitrary wave generator.

If memristors are used in neuron research, in addition to the number of erases and writes and the data retention time, their performance tests also require synaptic resistance dynamics testing. Synaptic plasticity is the neurobiological basis of brain memory and learning, and there are many forms. According to the length of memory, it can be divided into short-term plasticity (STP) and long-term plasticity (LTP), among which short-term plasticity includes paired pulse depression (PPD), paired pulse facilitation (PPF), and posttetanic potentiation (PTP). In addition, there are some other plasticities, such as: discharge rate dependent plasticity (SRDP), discharge time dependent plasticity (STDP), etc., which are the basis for synapses to process neural signals and neural calculations.

The conductive state of the memristor can be used to represent the change of synaptic weight. By changing the shape, frequency, duration and other parameters of the stimulation pulse voltage, the characteristics of the neural stimulation signal corresponding to different synaptic functions can be simulated. Measuring the transient current can understand the dynamic process of resistance change and obtain the regulation method of neural morphological characteristics. Similar to the cycle number and endurance test, it is necessary to program the semiconductor parameter tester with pulse function or high-speed arbitrary wave generator to generate the corresponding pulse sequence for automated testing.

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Various configuration options to meet extreme surface testing needs

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Tektronix China has a local R&D team to meet customers’ customized testing needs

Many leading memristor R&D units adopt Tektronix test solutions