US6201737B1
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US
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Apparatus and method to characterize the threshold distribution in an NROM virtual ground array
Assignee: Monterey Research LLC
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Filing: 2000-04-26
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Granted: 2001-03-13
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Expires: 2020-04-26
Abstract
Abstract A virtual ground array based flash memory device includes a virtual ground array containing individual memory elements with supporting input/output circuitry. Variations occur in the threshold voltage of memory elements contained in the virtual ground array caused by excessive usage of the memory elements. Characterization of the variation of threshold voltage as a function of usage as well as the distribution of the various threshold voltages is important for diagnostic purposes. External sources of voltage and means of determination are necessary to characterize the threshold voltages and the I-V characteristics, when the virtual ground array is in a diagnostic mode. In this mode, the drains, sources, and gates of selected memory elements in the virtual ground array may be under independent external control. The current from the source of the selected memory element is determined in response to the externally controlled voltages, thereby creating an I-V curve. Operational elements contained in input/output multiplexors to the virtual ground array pass externally controlled near ground voltages to the selected memory element. The present arrangement and method of characterizing selected memory elements in the virtual ground array using the source side of the memory elements saves time, conserves power, and is a useful diagnostic tool.
Inventors
- 👤 Shane Hollmer
- 👤 Kazuhiro Kurihara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:40
CPC Classifications
G; G11; G11C; G11C16/00; G11C16/02; G11C16/06; G11C16/26; G11C16/04; G11C16/0491
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
69 words
A method of characterizing non-volatile memory elements in a virtual ground array from the source side comprising: selecting a set of memory elements contained in the virtual ground array; externally controlling a voltage of at least one of a gate, source, and drain of at least one selected memory element in the set of selected memory elements; and determining a current from the source of the selected memory element.
Claim 2
Independent Claim
69 words
A method of characterizing non-volatile memory elements in a virtual ground array from the source side comprising: selecting a set of memory elements contained in the virtual ground array; externally controlling a voltage of at least one of a gate, source, and drain of at least one selected memory element in the set of selected memory elements; and determining a current from the source of the selected memory element.
Claim 3
Dependent Claim
24 words
The method of claim 1 further comprising providing an operational element adapted to pass externally controlled, near ground, voltages to the selected memory element.
Claim 4
Dependent Claim
24 words
The method of claim 2 , wherein controlling comprises controlling the voltages applied to the gate and the drain of the selected memory element.
Claim 5
Dependent Claim
87 words
The method of claim 3 , wherein determining further comprises: changing the voltage applied to the gate of the selected memory element incrementally toward a predetermined voltage while holding the voltage applied to the drain of the selected memory element constant until the predetermined voltage is applied to the gate of the memory element; and ascertaining the current from the source of the selected memory element after every incremental change in the voltage applied to the gate, thereby creating an I-V curve for the selected memory element.
Claim 6
Dependent Claim
26 words
The method of claim 4 , further comprising repeating creating an I-V curve for all of the memory elements in the set of selected memory elements.
Claim 7
Dependent Claim
87 words
The method of claim 3 , wherein determining further comprises: changing the voltage applied to the drain of the selected memory element incrementally toward a predetermined voltage while holding the voltage applied to the gate of the selected memory element constant until the predetermined voltage is applied to the drain of the memory element; and ascertaining the current from the source of the selected memory element after every incremental change in the voltage applied to the drain, thereby creating an I-V curve for the selected memory element.
Claim 8
Dependent Claim
25 words
The method of claim 6 further comprising repeating creating an I-V curve for all of the memory elements in the set of selected memory elements.
Claim 9
Dependent Claim
15 words
The method of claim 1 further comprising creating an I-V curve for the memory element.
Claim 10
Independent Claim
70 words
A method of characterizing non-volatile memory elements in a virtual ground array from the source side comprising: selecting a memory element of a plurality of memory elements contained in the virtual ground array; erasing the selected memory element; externally controlling a gate voltage of a gate and a drain voltage of a drain of the selected memory element; and determining a current from a source of the selected memory element.
Claim 11
Independent Claim
70 words
A method of characterizing non-volatile memory elements in a virtual ground array from the source side comprising: selecting a memory element of a plurality of memory elements contained in the virtual ground array; erasing the selected memory element; externally controlling a gate voltage of a gate and a drain voltage of a drain of the selected memory element; and determining a current from a source of the selected memory element.
Claim 12
Dependent Claim
31 words
The method of claim 9 , wherein determining further comprises changing the gate voltage incrementally toward a predetermined voltage while holding the drain voltage constant until the predetermined voltage is applied.
Claim 13
Dependent Claim
23 words
The method of claim 10 further comprising repeating determining for all of the memory elements in a predetermined set of selected memory elements.
Claim 14
Dependent Claim
24 words
The method of claim 11 further comprising providing an operational element adapted to pass externally controlled, near ground, voltages to the selected memory element.
Claim 15
Dependent Claim
31 words
The method of claim 9 , wherein determining further comprises changing the drain voltage incrementally toward a predetermined voltage while holding the gate voltage constant until the predetermined voltage is applied.
Claim 16
Dependent Claim
23 words
The method of claim 13 further comprising repeating determining for all of the memory elements in a predetermined set of selected memory elements.
Claim 17
Dependent Claim
24 words
The method of claim 14 further comprising providing an operational element adapted to pass externally controlled, near ground, voltages to the selected memory element.
Claim 18
Independent Claim
261 words
An apparatus for characterizing non-volatile memory elements in a virtual ground array from the source side, the apparatus mcomprising: a virtual ground array containing memory elements, each of the memory elements having a gate selectable by a word line of a plurality of word lines, a source selectableby a first bitline of a plurality of bitlines, and a drain selectable by a second bitline of the plurality of bitlines; at least one source multiplexor, each source multiplexor operatively connected with the source of one of at least one selected memory element contained in the virtual ground array and multiplexing between the source and one of internal sense circuitry and an I/O pad, the I/O pad in communication with external sense circuitry; at least one word line multiplexor, each word line multiplexor operatively connected with the gate of one of at least one memory element contained in the virtual ground array and multiplexing between the word line and one of an internal gate voltage generator and an external gate controller; at least one drain multiplexor, each drain multiplexor operatively connected with the drain of one of at least one selected memory element contained in the virtual ground array and multiplexing between the drain and one of an internal drain voltage generator and an external drain controller; and at least one operational element adapted to pass externally controlled near ground voltages to the selected memory element; wherein the drain and the gate of the selected memory element is externally controlled, and a current is determined from the source of the selected memory element.
Claim 19
Independent Claim
261 words
An apparatus for characterizing non-volatile memory elements in a virtual ground array from the source side, the apparatus mcomprising: a virtual ground array containing memory elements, each of the memory elements having a gate selectable by a word line of a plurality of word lines, a source selectableby a first bitline of a plurality of bitlines, and a drain selectable by a second bitline of the plurality of bitlines; at least one source multiplexor, each source multiplexor operatively connected with the source of one of at least one selected memory element contained in the virtual ground array and multiplexing between the source and one of internal sense circuitry and an I/O pad, the I/O pad in communication with external sense circuitry; at least one word line multiplexor, each word line multiplexor operatively connected with the gate of one of at least one memory element contained in the virtual ground array and multiplexing between the word line and one of an internal gate voltage generator and an external gate controller; at least one drain multiplexor, each drain multiplexor operatively connected with the drain of one of at least one selected memory element contained in the virtual ground array and multiplexing between the drain and one of an internal drain voltage generator and an external drain controller; and at least one operational element adapted to pass externally controlled near ground voltages to the selected memory element; wherein the drain and the gate of the selected memory element is externally controlled, and a current is determined from the source of the selected memory element.
Claim 20
Dependent Claim
44 words
The apparatus of claim 16 further comprising: an external gate controller adapted to supply a gate voltage to the gate of the selected memory element; and an external drain controller adapted to supply a drain voltage to the drain of the selected memory element.
Claim 21
Dependent Claim
56 words
The apparatus of claim 17 , wherein: the gate voltage is incrementally changed toward a predetermined voltage and the drain voltage is held constant until the predetermined voltage is applied; and the current from the source of the selected memory element is determined after each incremental change, thereby creating an I-V curve for the memory element.
Claim 22
Dependent Claim
25 words
The apparatus of claim 18 wherein the I-V curve is determined for all of a predetermined set of memory elements in the virtual ground array.
Claim 23
Dependent Claim
56 words
The apparatus of claim 17 , wherein: the drain voltage is incrementally changed toward a predetermined voltage and the gate voltage is held constant until the predetermined voltage is applied; and the current from the source of the selected memory element is determined after each incremental change, thereby creating an I-V curve for the memory element.
Claim 24
Dependent Claim
25 words
The apparatus of claim 20 wherein the I-V curve is determined for all of a predetermined set of memory elements in the virtual ground array.
Claim 25
Dependent Claim
61 words
The apparatus of claim 16 , the virtual ground array further comprising: select gates selectable by select gate lines; local bitlines connecting the select gates with the memory elements; and global bitlines connecting the select gates with elements external to the virtual ground array; wherein the memory elements are selectable by word lines and at least two of the select gates.
Claim 26
Dependent Claim
24 words
The apparatus of claim 22 , wherein the local bitlines are formed by a diffusion process and the global bitlines are composed of metal.
Claim 27
Dependent Claim
91 words
The apparatus of claim 22 , wherein: the memory elements disposed along each word line are arranged in series along the word line; and the virtual ground array is arranged such that a first set of pairs of select gates are connected with a first set of pairs of memory elements, a second set of pairs of select gates are connected with a second set of pairs of memory elements, and the first set of pairs of memory elements and second set of pairs of memory elements partially overlap each other.
Claim 28
Dependent Claim
132 words
The arrangement of claim 22 , further comprising: at least one multiplexor connected with the virtual ground array and both the source and drain multiplexors operative to select one memory element of a set of selected memory elements in the virtual ground array such that the drain of the selected memory element is input to the drain multiplexor and the source of the selected memory element is input to the source multiplexor, each multiplexor containing at least one operational element; and at least one column decoder connected with the virtual ground array and the word line multiplexor operative to select one memory element of a set of selected memory elements in the virtual ground array such that the word line of the selected memory element is input to the word line multiplexor.
Claim 29
Independent Claim
283 words
An apparatus for characterizing non-volatile memory elements in a virtual ground array from the source side, the apparatus comprising: a virtual ground array containing memory elements, each of the memory elements having a gate selectable by a word line of a plurality of word lines, a source selectable by a first bitline of a plurality of bitlines, and a drain selectable by a second bitline of the plurality of bitlines; at least one source multiplexor, each source multiplexor operatively connected with the source of one of at least one selected memory element contained in the virtual ground array and multiplexing between the source and one of internal sense circuitry and an I/O pad, the I/O pad in communication with external sense circuitry; at least one word line multiplexor, each word line multiplexor operatively connected with the gate of one of at least one memory element contained in the virtual ground array and multiplexing between the word line and one of an internal gate voltage generator and an external gate controller; at least one drain multiplexor, each drain multiplexor operatively connected with the drain of one of at least one selected memory element contained in the virtual ground array and multiplexing between the drain and one of an internal drain voltage generator and an external drain controller; a gate controller operative to externally control a gate voltage of the selected memory element; a drain controller operative to externally control a drain voltage of the selected memory element; and at least one operational element adapted to pass externally controlled near ground voltages to the selected memory element; wherein a current of the selected memory element is determined from the source of the selected memory element.
Claim 30
Independent Claim
283 words
An apparatus for characterizing non-volatile memory elements in a virtual ground array from the source side, the apparatus comprising: a virtual ground array containing memory elements, each of the memory elements having a gate selectable by a word line of a plurality of word lines, a source selectable by a first bitline of a plurality of bitlines, and a drain selectable by a second bitline of the plurality of bitlines; at least one source multiplexor, each source multiplexor operatively connected with the source of one of at least one selected memory element contained in the virtual ground array and multiplexing between the source and one of internal sense circuitry and an I/O pad, the I/O pad in communication with external sense circuitry; at least one word line multiplexor, each word line multiplexor operatively connected with the gate of one of at least one memory element contained in the virtual ground array and multiplexing between the word line and one of an internal gate voltage generator and an external gate controller; at least one drain multiplexor, each drain multiplexor operatively connected with the drain of one of at least one selected memory element contained in the virtual ground array and multiplexing between the drain and one of an internal drain voltage generator and an external drain controller; a gate controller operative to externally control a gate voltage of the selected memory element; a drain controller operative to externally control a drain voltage of the selected memory element; and at least one operational element adapted to pass externally controlled near ground voltages to the selected memory element; wherein a current of the selected memory element is determined from the source of the selected memory element.
Claim 31
Dependent Claim
56 words
The apparatus of claim 26 , wherein: the gate voltage is incrementally changed toward a predetermined voltage and the drain voltage is held constant until the predetermined voltage is applied; and the current from the source of the selected memory element is determined after each incremental change, thereby creating an I-V curve for the memory element.
Claim 32
Dependent Claim
25 words
The apparatus of claim 27 wherein the I-V curve is determined for all of a predetermined set of memory elements in the virtual ground array.
Claim 33
Dependent Claim
56 words
The apparatus of claim 26 , wherein: the darin voltage is incrementally changed toward a predetermined voltage and the gate voltage is held constant until the predetermined voltage is applied; and the current from the source of the selected memory element is determined after each incremental change, thereby creating an I-V curve for the memory element.
Claim 34
Dependent Claim
25 words
The apparatus of claim 29 wherein the I-V curve is determined for all of a predetermined set of memory elements in the virtual ground array.
Claim 35
Dependent Claim
61 words
The apparatus of claim 26 , the virtual ground array further comprising: select gates selectable by select gate lines; local bitlines connecting the select gates with the memory elements; and global bitlines connecting the select gates with elements external to the virtual ground array; wherein the memory elements are selectable by word lines and at least two of the select gates.
Claim 36
Dependent Claim
24 words
The apparatus of claim 31 , wherein the local bitlines are formed by a diffusion process and the global bitlines are composed of metal.
Claim 37
Dependent Claim
91 words
The apparatus of claim 32 , wherein: the memory elements disposed along each word line are arranged in series along the word line; and the virtual ground array is arranged such that a first set of pairs of select gates are connected with a first set of pairs of memory elements, a second set of pairs of select gates are connected with a second set of pairs of memory elements, and the first set of pairs of memory elements and second set of pairs of memory elements partially overlap each other.
Claim 38
Dependent Claim
132 words
The arrangement of claim 33 , further comprising: at least one multiplexor connected with the virtual ground array and both the source and drain multiplexors operative to select one memory element of a set of selected memory elements in the virtual ground array such that the drain of the selected memory element is input to the drain multiplexor and the source of the selected memory element is input to the source multiplexor each multiplexor containing at least one operational element; and at least one column decoder connected with the virtual ground array and the word line multiplexor operative to select one memory element of a set of selected memory elements in the virtual ground array such that the word line of the selected memory element is input to the word line multiplexor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-03-12 | 2004-09-11 | 2005-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-03-12 | 2008-09-11 | 2009-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-03-12 | 2012-09-11 | 2013-03-13 | $7700.00 | Window Closed / Lapsed |