Write abort detection for multi-state memories
First Claim
1. A method, comprising:
- performing a search operation in a block of a nonvolatile memory for finding a last written word line, the nonvolatile memory comprising a plurality of memory cells and a plurality of word lines connected between a first end of the block and a second end of the block, each of the plurality of memory cells connected to one of the plurality of word lines, wherein the search operation comprises;
applying a first bias voltage to a first portion of the plurality of word lines;
applying a second bias voltage to a selected one of the plurality of word lines;
applying a third bias voltage to a second portion of the plurality of word lines; and
varying the first portion of the plurality of word lines, the second portion of the plurality of word lines, and the selected one of the plurality of word lines based upon a predetermined threshold until the last written word line is identified;
wherein the selected one of the plurality of word lines is located between the first portion of the plurality of word lines and the second portion of the plurality of word lines; and
wherein the third bias voltage is less than the first bias voltage.
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Abstract
Techniques are presented to determine whether a multi-state memory device suffers has a write operation aborted prior to its completion. In an example where all the word lines of a memory block is first programmed to an intermediate level (such as 2 bits per cells) before then being fully written (such as 4 bits per cell), after determining that intermediate programming pass completed, the block is searched using the read level for the highest multi-state to find the last fully programmed word line, after which the next word line is checked with the lowest state'"'"'s read level to determine whether the full programming had begun on this word line. In an example where each word line is fully written before beginning the next word line of the block, after determining the first erased word line, the preceding word line is checked as the highest state to see if programming completed and, if not, checked at the lowest read level to see if programming began.
155 Citations
20 Claims
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1. A method, comprising:
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performing a search operation in a block of a nonvolatile memory for finding a last written word line, the nonvolatile memory comprising a plurality of memory cells and a plurality of word lines connected between a first end of the block and a second end of the block, each of the plurality of memory cells connected to one of the plurality of word lines, wherein the search operation comprises; applying a first bias voltage to a first portion of the plurality of word lines; applying a second bias voltage to a selected one of the plurality of word lines; applying a third bias voltage to a second portion of the plurality of word lines; and varying the first portion of the plurality of word lines, the second portion of the plurality of word lines, and the selected one of the plurality of word lines based upon a predetermined threshold until the last written word line is identified; wherein the selected one of the plurality of word lines is located between the first portion of the plurality of word lines and the second portion of the plurality of word lines; and wherein the third bias voltage is less than the first bias voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method, comprising:
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performing a search operation on a block of a nonvolatile memory for finding a last written page of the block, the block comprising a plurality of memory cells and a plurality of word lines, each of the plurality of memory cells connected to one of the plurality of word lines, wherein the plurality of memory cells are programmed sequentially and the search operation for finding the last written page of the block comprises; applying a first bias voltage to a first portion of the plurality of word lines; applying a second bias voltage to a selected one of the plurality of word lines; applying a third bias voltage to a second portion of the plurality of word lines; comparing a number of the plurality of memory cells connected to the first portion of the word lines that are conducting with a pre-determined threshold; changing the selected one of the plurality of word lines, the first portion of the plurality of word lines, and the second portion of the plurality of word lines by a first increment based upon the number being equal to or greater than the predetermined threshold; changing the selected one of the plurality of word lines, the first portion of the plurality of word lines, and the second portion of the plurality of word lines by a second increment based upon the number being less than the predetermined threshold; wherein the plurality of memory cells connected to the second portion of the plurality of word lines are designated to be programmed after the plurality of memory cells connected to the first portion of the plurality of word lines; wherein the selected one of the plurality of word lines is located between the first portion of the plurality of word lines and the second portion of the plurality of word lines; and wherein the third bias voltage corresponds to a voltage level that causes the plurality of memory cells in an erase condition to conduct. - View Dependent Claims (14)
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15. A method comprising:
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dividing a plurality of word lines of a nonvolatile memory into a plurality of zones, wherein each of the plurality of word lines is connected to a memory cell, and wherein each of the plurality of zones comprises a sequential group of the plurality of word lines; applying a first bias voltage to a first portion of the plurality of zones; applying a second bias voltage to a second portion of the plurality of zones, wherein the first bias voltage is less than the second bias voltage; identifying one of the plurality of zones from the first portion of the plurality of zones and the second portion of the plurality of zones having a last written word line, wherein the last written word line is part of the plurality of word lines; dividing the one of the plurality of zones having the last written word line into a plurality of sub-zones; and identifying one of the plurality of sub-zones having the last written word line by applying the first bias voltage to a first portion of the plurality of sub-zones and the second bias voltage to a second portion of the plurality of sub-zones. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification