A research team at the Japanese Tohoku University has developed 128Mb-density STT-MRAM (spin-transfer torque magnetoresistive random access memory) with a write speed of 14 ns for use in embedded memory applications.

This is currently the world's fastest write speed for embedded memory application with a density over 100Mb and could pave the way for the mass-production of large capacity STT-MRAM.

STT-MRAM is capable of high-speed operation and consumes very little power as it retains data even when the power is off. It is gaining traction as the next-generation technology for applications such as embedded memory, main memory and logic. Three semiconductor fabrication plants have already announced plans to start risk mass-production of STT-MRAM.

Currently available STT-MRAM has a capacity ranging from 8Mb-40Mb. But in order to make STT-MRAM more practical, it is necessary to increase the memory density. The team at the Center for Innovative Integrated Electronic Systems (CIES) has increased the memory density of STT-MRAM by developing STT-MRAMs in which magnetic tunnel junctions (MTJs) are integrated with CMOS. The approach reduces the power-consumption of embedded memory such as cache and eFlash memory.

MTJs were miniaturized through a series of process developments. To reduce the memory size needed for higher-density STT-MRAM, the MTJs were formed directly on via holes - small openings that allow a conductive connection between the different layers of a semiconductor device. By using the reduced size memory cell, the research group has designed 128Mb-density STT-MRAM and fabricated a chip.

In the fabricated chip, the researchers measured a write speed of subarray, and proved a an operation of 14ns at a low power supply voltage of 1.2 V.

The results of this research were presented at the 2018 International Electron Devices Meeting held in San Francisco, U.S.A., on December 5, 2018.