Process development of sub-0.5 μm nonvolatile magnetoresistive random access memory arrays

Abstract

The fabrication of magnetoresistive random access memory (MRAM) devices requires full characterization of the giant magnetoresistive ratio (GMR) permalloy films at the sub-0.5 μm feature dimensions. Future memory arrays of the 1 and 4 Gb density require GMR bit cells of a 0.25 μm and below in configurations which will require close proximity of cells. Since the cells are magnetic and act like tiny magnets, the switching field of a cell may be influenced by the polarization direction of the neighboring cell. This article describes the development of sub-0.5 μm MRAM devices using current e-beam microfabrication techniques and the implementation of the latest chemically amplified deep ultraviolet resists. Etch processing is also discussed as well as the testing results for the 0.25 μm arrays. Testing the GMR material at these dimensions consists of evaluating the single magnetic domain behavior and observing the effect of cell size on the magnetoresistance ratio. Array testing will consist of measuring switching field variations on a 0.25 μm 5×5 array to determine if there is field coupling with neighboring cells.