Operating a resistive array
View Patent ↗The present invention is a means and method for constructing and operating a 3-D array and, more particularly, a 3-D memory array. This array can be manufactured as a monolithic integrated circuit at low cost by virtue of the limited number of steps per layer of memory elements. The low number of steps results by having the storage elements separated by a resistive component as opposed to an active component. The 3-D array is in essence, an array of 2-D resistive arrays (row-planes) having a long dimension (typically along the rows) and a short dimension (typically in the direction of the stacked layers). Any one row-plane can be isolated from the rest and be accessed independently from all of the other row-planes in the 3-D array. This makes it possible to operate and analyze a single row-plane as a mostly stand-alone circuit. The present invention lends itself to single bit accesses as well as simultaneous multiple bit accesses.
1. A method for accessing a two-dimensional memory array within a three-dimensional or multi-dimensional resistive memory array comprising:
i. calculating a first voltage for a first unselected post in a two-dimensional plane,
ii. applying that first voltage to that first unselected post,
iii. calculating a second voltage for a second unselected post in a two-dimensional plane, wherein the second voltage is different than the first voltage,
iv. applying that second voltage to that unselected post, and
v. applying a third voltage different than the calculated first voltage and second voltage to a selected post.
2. The method of claim 1 further comprising assuming a resistance or equivalent value for a memory element when calculating a voltage.
3. The method of claim 2 whereby the assumed resistance or equivalent value is the greatest value typically encountered for a memory element.
4. The method of claim 2 whereby the assumed resistance or equivalent value is the least value typically encountered for a memory element.
5. The method of claim 2 whereby the assumed resistance or equivalent value is midway between the greatest and the least value typically encountered for a memory element.
6. The method of claim 2 further comprising measuring a current to determine a bit state.
7. A three dimensional resistive information storage device comprising a plurality of two-dimensional arrays whereby at least one two-dimensional array comprises:
i. a first plurality of conductive lines that are connected to current controlling devices in the substrate and generally perpendicular to the substrate surface, wherein a plurality of different voltages are applied to a plurality of unselected conductive lines of the plurality of conductive lines, and
ii. a second plurality of conductive lines that are orthogonal to the first set of conductive lines and that are generally parallel to the substrate surface, wherein, and
iii. an information storage element proximate to a point of intersection of the first and second sets of conductive lines.
8. The three dimensional information storage device of claim 7 whereby the two-dimensional arrays are generally parallel to each other.
9. The three dimensional information storage device of claim 7 whereby the first plurality of conductive lines comprises a selected line and a plurality of unselected lines whereby, when an information storage element is being accessed, the lines of the plurality of unselected lines are biased such that there is little or no voltage difference between a given unselected line and the voltage on a line of the second set of conductive lines at the point where said line of the second set of conductive lines passes said unselected line.
10. The three dimensional information storage device of claim 9 whereby, when an information storage element is being accessed, a voltage is applied to the selected line such that current will flow through the information storage element being accessed.
11. The three dimensional information storage device of claim 7 whereby the information storage element comprises a phase-change material.
12. The three dimensional information storage device of claim 11 whereby the phase-change material comprises a Chalcogenide alloy.
13. The three dimensional information storage device of claim 12 whereby the Chalcogenide alloy comprises GST.