Patent US6085341A successfully refreshed from Google Patents.
US6085341A
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Memory test mode for wordline resistive defects
Assignee: Micron Technology Inc
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Filing: 1998-02-23
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Granted: 2000-07-04
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Expires: 2018-02-23
Abstract
Abstract A method and apparatus for detecting resistive defects in a memory device. A pulldown device is placed at the end of a wordline opposite the end of the wordline having a wordline driver. When the test mode is enabled the wordline pulldown device is turned on. By tailoring the on resistance of the pulldown device such that it is a few times larger than the wordline wire resistance, a resistive divider may be created between the wordline wire resistance and the pulldown device resistance. If a resistive defect exists in the wordline, the increased wordline resistance will create a voltage drop in the wordline when the pulldown device is turned on. This voltage drop indicates that a defect exists in the wordline, and the defect may be located by determining the area of the wordline in which the voltage drop occurs.
Inventors
- 👤 Jeffrey K. Greason
- 👤 Daniel R. Grumbling
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:06
CPC Classifications
G; G11; G11C; G11C29/00; G11C29/04; G11C29/50; G11C29/50008; G11C29/02; G11C29/025; G11C29/08; G11C29/12; G11C29/44
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
40 words
A method for detecting defects in a memory comprising: placing a pulldown device at an end of a wordline, said pulldown device having a selected on resistance; turning said pulldown device on; and determining the voltage drop on said wordline.
Claim 2
Independent Claim
40 words
A method for detecting defects in a memory comprising: placing a pulldown device at an end of a wordline, said pulldown device having a selected on resistance; turning said pulldown device on; and determining the voltage drop on said wordline.
Claim 3
Dependent Claim
104 words
The method as described in claim 1 wherein said step of determining the voltage drop on wordline further comprises: testing said wordline for a voltage drop; and determining if a defect exists in said wordline based upon the following criteria: if no voltage drop is observed, then a defect does not exist; if a nominal voltage drop is observed, then a defect does not exist; if an intermediate voltage drop is observed and said memory functions at a lower frequency, then a defect does exist; and if a large voltage drop is observed and said memory does not function, then a defect does exist.
Claim 4
Dependent Claim
21 words
The method as described in claim 1 further comprising the step of determining the location of said defect in said memory.
Claim 5
Dependent Claim
72 words
The method as described in claim 3 wherein said step of determining the location of said defect in said memory comprises: ascertaining which portions of said memory are functioning properly; and ascertaining which portions of said memory are not functioning properly; said defect being located within a region downstream of the portions of said memory which are functioning properly and upstream of the portions of said memory which are not functioning properly.
Claim 6
Independent Claim
56 words
A method for detecting defects in a memory comprising: providing a plurality of wordlines having a first end and a second end; placing a plurality of pulldown devices at said second end of each of said plurality of wordlines; turning on said plurality of pulldown devices; and determining the voltage drop on said plurality of wordlines.
Claim 7
Independent Claim
56 words
A method for detecting defects in a memory comprising: providing a plurality of wordlines having a first end and a second end; placing a plurality of pulldown devices at said second end of each of said plurality of wordlines; turning on said plurality of pulldown devices; and determining the voltage drop on said plurality of wordlines.
Claim 8
Dependent Claim
31 words
The method as described in claim 5 wherein said plurality of pulldown devices have a selected on resistance and said plurality of pulldown devices are turned on at the same time.
Claim 9
Dependent Claim
115 words
The method as described in claim 5 wherein said step of determining the voltage drop on said plurality of wordlines further comprises: testing each of said plurality of wordlines for a voltage drop; and determining if a defect exists in each of said plurality of wordlines based upon the following criteria: if no voltage drop is observed, then a defect does not exist; if a nominal voltage drop is observed, then a defect does not exist; if an intermediate voltage drop is observed and said memory functions at a lower frequency, then a defect does exist; and if a large voltage drop is observed and said memory does not function, then a defect does exist.
Claim 10
Dependent Claim
21 words
The method as described in claim 5 further comprising the step of determining the location of said defect in said memory.
Claim 11
Dependent Claim
94 words
The method as described in claim 8 wherein said memory is divided into a plurality of rows of wordlines and said step of determining the location of said defect in said memory comprises: ascertaining which of said plurality of wordlines are functioning properly; and ascertaining which of said plurality of wordlines are not functioning properly; determining in which row of memory each of said plurality of wordlines that are not functioning properly is located; said defect being located in said first row of said memory that contains a wordline which is not functioning properly.
Claim 12
Dependent Claim
146 words
The method as described in claim 9 wherein said rows of said wordlines in said memory are further divided into a plurality of columns and said step of determining the location of said defect in said memory further comprises the steps of: ascertaining which portions of said wordline as defined by said plurality of columns are functioning properly; and ascertaining which portions of said wordline as defined by said plurality of columns are not functioning properly; said defect being located in said first row of said memory that contains a wordline which is not functioning properly and said defect being located in said column located within a region downstream of the portions of said wordline as defined by said plurality of columns which are functioning properly and upstream of the portions of said wordline as defined by said plurality of columns which are not functioning properly.
Claim 13
Independent Claim
61 words
An apparatus for detecting defects in a memory comprising: a memory a plurality of wordlines in said memory, said wordlines having a first end and a second end; a plurality of pulldown devices, said pulldown devices coupled to said second end of each of said plurality of wordlines; and a switch for turning said plurality of pulldown devices on and off.
Claim 14
Independent Claim
61 words
An apparatus for detecting defects in a memory comprising: a memory a plurality of wordlines in said memory, said wordlines having a first end and a second end; a plurality of pulldown devices, said pulldown devices coupled to said second end of each of said plurality of wordlines; and a switch for turning said plurality of pulldown devices on and off.
Claim 15
Dependent Claim
36 words
The apparatus as described in claim 11 wherein said memory is configured in an array of rows and columns, wherein said rows are made up of wordlines and said columns divide said wordlines into device portions.
Claim 16
Dependent Claim
22 words
The apparatus as described in claim 11 wherein said pulldown device is a small MOS device that has a selected on resistance.
Claim 17
Dependent Claim
23 words
The apparatus as described in claim 11 wherein said switch turns said plurality of pulldown devices on and off at the same time.
Claim 18
Independent Claim
61 words
An apparatus for detecting defects in a memory comprising: a memory a plurality of wordlines in said memory, said wordlines having a first end and a second end; a plurality of pulldown devices, said pulldown devices coupled to said second end of each of said plurality of wordlines; and a means for turning said plurality of pulldown devices on and off.
Claim 19
Independent Claim
61 words
An apparatus for detecting defects in a memory comprising: a memory a plurality of wordlines in said memory, said wordlines having a first end and a second end; a plurality of pulldown devices, said pulldown devices coupled to said second end of each of said plurality of wordlines; and a means for turning said plurality of pulldown devices on and off.
Claim 20
Dependent Claim
36 words
The apparatus as described in claim 15 wherein said memory is configured in an array of rows and columns, wherein said rows are made up of wordlines and said columns divide said wordlines into device portions.
Claim 21
Dependent Claim
33 words
The apparatus as described in claim 15 wherein said means for turning said plurality of pulldown devices on and off turns said plurality of pulldown devices on and off at the same time.
Claim 22
Dependent Claim
23 words
The apparatus as described in claim 15 wherein said means for turning said plurality of pulldown devices on and off comprises a switch.
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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) | 2003-07-04 | 2004-01-03 | 2004-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-07-04 | 2008-01-03 | 2008-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-07-04 | 2012-01-03 | 2012-07-04 | $7700.00 | Window Closed / Lapsed |