Nonvolatile memory cell operating by increasing order in polycrystalline semiconductor material

Abstract

A nonvolatile memory cell is described, the memory cell comprising a semiconductor diode. The semiconductor material making up the diode is formed with significant defect density, and allows very low current flow at a typical read voltage. Application of a programming voltage permanently changes the nature of the semiconductor material, resulting in an improved diode. The programmed diode allows much higher current flow, in some embodiments one, two or three orders of magnitude higher, at the same read voltage. The difference in current allows a programmed memory cell to be distinguished from an unprogrammed memory cell. Fabrication techniques to generate an advantageous unprogrammed defect density are described. The memory cell of the present invention can be formed in a monolithic three dimensional memory array, having multiple stacked memory levels formed above a single substrate.

Description

RELATED APPLICATIONS [0001] This application is a continuation-in-part of Herner et al., U.S. patent application Ser. No. 10 / 955,549, “Nonvolatile Memory Cell Without a Dielectric Antifuse Having High- and Low-Impedance States,” filed Sep. 29, 2004 and hereinafter the '549 application; itself a continuation-in-part of Herner et al., U.S. patent application Ser. No. 10 / 855,784, “An Improved Method for Making High-Density Nonvolatile Memory,” filed May 26, 2004; which is a continuation of Herner et al., U.S. patent application Ser. No. 10 / 326,470, “An Improved Method for Making High-Density Nonvolatile Memory,” filed Dec. 19, 2002 (since abandoned) and hereinafter the '470 application, all assigned to the assignee of the present invention and hereby incorporated by reference in their entirety.BACKGROUND OF THE INVENTION [0002] The invention relates to a nonvolatile one-time-programmable memory cell. [0003] Prior art nonvolatile memories, such as Johnson et al., U.S. Pat. No. 6,034,882...

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Benefits of technology

[0014] The preferred aspects and embodiments will now be described with reference to the attached drawings.

Problems solved by technology

When a sufficiently large voltage is applied between the conductors, however, the dielectric antifuse layer suffers dielectric breakdown and ruptures, and a permanent conductive path is formed through the dielectric antifuse layer.

If the dielectric antifuse layer is too thin, leakage current can be a severe problem.

Disturb can also be a problem: Every time the memory cell is read, the dielectric antifuse layer is exposed to some stress, and may eventually break down and be inadvertently programmed.

Higher voltages in electronic devices, for example in portable devices, are generally disadvantageous.

If the dielectric antifuse layer is an oxide layer formed by oxidation, a thicker antifuse layer calls for either higher temperatures or slower fabrication time, both disadvantageous in forming a commercial device.

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