Hot topic session 9C: Test and fault tolerance for emerging memory technologies

Ever larger on-die memory arrays for future processors in CMOS logic technology drive the need for dense and scalable embedded memory alternatives beyond SRAM and eDRAM. Recent advances in nonvolatile spin transfer torque (STT) RAM technology, which stores data by the spin orientation of a soft ferromagnetic material and shows current induced switching, have created interest for its use as embedded memory. STTRAM exhibits scalable write current, sufficient read margin and nonvolatility or persistence, all of which make it an attractive solution for last level cache, embedded cache or even main memory. In an era of on-die non-volatile storage, new defect, disturb and fault mechanisms need to be comprehended during characterization as well as manufacturing tests. The first part of the talk will introduce STTRAM and review the fundamentals of the cell design, the read and write mechanisms as well as recent advances in technology, which make it a potential successor to eDRAM, followed by how variations and thermal noise limit the material and cell design space. The second part will discuss new test models that would be required for such non-volatile storage, the necessity of large scale data collection and analysis, as well as the need for BIST and on-line testing, and conclude with challenges and opportunities in STTRAM testing that lie ahead of us.