Patent ID: 6952361
Filing Date: 2005-10-04
Classification: G11C,H01L

Abstract:
1. A volumetric data storage apparatus comprising a plurality of stacked matrix-addressable memory devices, wherein each memory device comprises first and second electrode means in the form of respective layers with parallel electrodes forming word lines and bit lines of the memory device for the matrix-addressing thereof, the word lines being oriented orthogonally to the bit lines for the matrix-addressing of a memory device, wherein each memory device comprises a layer of memory material provided between the first and second electrode means and in direct or indirect contact therewith, wherein the second electrode means forms the first electrode means of a following memory device in the stack, whereby the number of electrode means becomes one more than the number of memory devices in the stack, wherein the memory material is a polarizable dielectric material capable of exhibiting hysteresis, preferably a ferroelectric or electret material, and wherein memory cells are defined in the memory material of a memory device at or between the crossings of the word lines and bit lines thereof, wherein electrodes of each electrode means are provided in a dense arrangement and mutually insulated by barrier layer therebetween, the thickness δ of the barrier layer being only a fraction of the electrode width, whereby the area fill factor of the electrodes in an electrode means approaches unity, that the top surface of an electrode means facing the neighbouring following electrode means is provided with parallel recesses oriented orthogonally to the electrodes and mutually spaced apart by a distance comparable to the electrode width w, the parallel recesses having a cross-sectional shape conforming to the cross-sectional shape of the electrodes, that every second electrode of the adjacent following electrode means is provided extending downwards in the recesses formed in the adjacent preceding electrode means, that a memory material is provided in a layer over each electrode means covering the surface thereof as well at least the side walls and optionally the bottom of the recesses therein, and that the electrodes extending into the recesses in conjunction with the orthogonally crossing electrodes of the adjacent preceding electrode means define memory cells having at least two switching directions in the memory material provided in the recesses, whereby the volumetric data storage apparatus is provided with a very high storage density, a memory cell fill factor of each memory layer of each memory device approaching the value of the area fill factor for the electrodes of the electrode means and with every second of the memory cells in a layer of memory material capable of being switched in at least two directions.