Fabrication and characterization of a crosstie random access memory

Device fabrication and characterization of a crosstie random access memory (CRAM) is discussed. The test vehicle is a partially accessed 64×4 bit array. Information is stored on domain walls in thin-film permalloy; two metallization layers, with insulating layers of silicon nitride, complete the structure. The device is fabricated on a silicon substrate, making possible complete integration of decoding, drive circuitry, and amplifiers on a single chip. Coincident currents in a row and a column conductor are used to write; 5 to 7.5 mA are used in each conductor. Writing has been accomplished in 20 ns. The magnetoresistance effect of the permalloy has been characterized for destructive or non-destructive read-out. Memory retention over a wide temperature range and up to 1 Mrad total radiation dose has been tested without encountering any limitations. The combination of characteristics of the CRAM is unique, with advantages over existing memory technologies for a wide range of applications.