High-density very efficient magnetic film memory arrays

Partially populated arrays using very small efficient DRO magnetic film memory cells have been constructed and tested to demonstrate the packaging and performance compatibility of such cells with integrated circuits. The experimental cells were made by vapor deposition of Permalloy, copper, and other materials through a mask in a flat wire configuration with an easy direction along the wire and a closed hard direction. A multiturn sense/digit line increased signal level and reduced drive current. cell densities from 4000 to 64 000 bit/in²have been examined. A typical cross section for an array consisted of 1200 Å Permalloy films with 0.002-inch-wide word lines on 0.004-inch centers with five-turn digit lines on 0.015-inch centers (16 000 bit/in). Word currents for the 0.002-inch-wide word lines were typically 80 to 100 mA. Digit currents for the five-turn digit lines were typically 8 to 12 mA, and signal outputs were typically 5 to 7 mV with signals 15 ns in duration.