IEDM: Magnetic RAM debuts as 28nm embedded NVM

November 24, 2016 // By Peter Clarke
A number of magnetic RAM developments are set to be reported at the International Electron Devices Meeting coming up in San Francisco from December 3 - 7, 2016 by teams from Samsung, Toshiba, SK Hynix and others.

A team drawn from Samsung R&D and Samsung's LSI business unit are apparently going to present the same information twice once in the main program and once in poster session dedicated to MEMS development.

The topic of both the oral presentation and the poster presentation is an 8Mbit spin-torque transfer MRAM embedded in a 28nm CMOS logic manufacturing process. The title of the main presentation – paper 27.2 – describes the circuit as "highly functional and reliable." The abstract adds that a novel integration, material stack and patterning technologies have been used to embed the perpendicular magnetic tunnel junction memory cell array into the copper metal back end without open fails and without severe degradation of the magnetic properties.

The perpendicular MTJ (pMTJ) uses a MgO/CoFeB stack to achieve a tunnel magnetoresistance value of 180 percent after full integration. Ion beam etching was used to reduce short fails below 1ppm. It will be interesting to see what the implications of IBE are for production throughput. The embed MRAM macro has a side sensing margin and retains information at 85 degrees C for 10 years, the abstract states.

Depending the economics of manufacturing this could be a process of choice for low-power microcontrollers and SoCs due to their ability to be switched off and retain data.

And on the stand-alone memory front a team of researchers from SK Hynix Inc. and Toshiba Electronics Korea Corp. is set to describe the first 4Gbit spin-torque transfer MRAM. The development is based on memory cells with an area of 9F2, very close to the size of DRAM cell, according to the abstract. The design has pMTJ optimized for a high tunnelling resistance ratio and therefore a low switching current requirement. Various techniques are set to be described that were used to manage write errors arising from process-related defects.

Everspin Technologies Inc. (Chandler, Ariz.) displayed a 1Gbit pMTJ-based MRAM at Electronica this year.

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