Resistive memory device having a retention layer with non-linear ion conductivity

Abstract

A memory device is disclosed. The memory device includes a bottom contact and a memory layer connected to the bottom contact, where the memory layer has a variable resistance. The device also includes a conductive top electrode on the memory layer, where the top electrode and the memory layer cooperatively form a heterojunction memory structure. The device also includes a retention layer between the memory layer and the top electrode, where the retention layer has an ionic conductivity which varies non-linearly with voltage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of and claims priority to U.S. patent application Ser. No. 15 / 924,014, entitled “A RESISTIVE MEMORY DEVICE HAVING A RETENTION LAYER,” filed Mar. 16, 2018, which is incorporated herein by reference for all purposes.FIELD OF THE INVENTION[0002]The present invention relates generally to nonvolatile memory devices, and more particularly to memory devices having effective speed comparable to DRAM, which do not require speed-crippling error correction and include hetero junctions of oxide materials.BACKGROUND OF THE INVENTION[0003]In general, memory devices or systems can be segmented in 3 distinct categories: internet-of-things (IoT) memories, embedded memories, and high-density high-volume memories. The memory requirements (cost, density, speed, endurance, retention, power consumption) are quite different for each of these 3 categories.[0004]IoT memories tend to be inexpensive, power-efficient, and low-densi...

AI Technical Summary

Problems solved by technology

DRAM, however, is expensive and volatile (for example, the data may need to be refreshed every 60 milliseconds) and sacrifices retention to maximize speed and endurance.

NAND Flash, however, sacrifices both speed and endurance to maximize retention.

Being limited to two dimensions (2D), DRAM will likely remain expensive since silicon area largely defines cost per gigabyte.

In contrast, the cost of NAND Flash is expected to decline over time because of three dimensional (3D) stacking.

The cost gap between DRAM and NAND Flash will likely increase over time.

It is equally unlikely that any emerging memory technology will replace DRAM because its speed and endurance combination is exceptionally hard to beat.

Furthermore, there is no economic justification to build a NAND Flash replacement for high-density applications while NAND Flash prices continue to decrease.

Another issue associated with semiconductor memory manufacturing has been the substantial costs of the semiconductor foundries which can be more than a billion dollars to establish.

Amortizing expenses increase the cost of memory chips.

In Flash memories, there have been improvements, but they have become susceptible to write cycle limitations and ability to support dynamic ranges are diminished as the quantum limit is approached.

Another issue with Flash memory is its limitations in write speeds and the number of write cycle limitations the cell will tolerate before it permanently fails.

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