U.S. patent application number 16/528607 was filed with the patent office on 2021-02-04 for memory device and row-hammer refresh method thereof.
This patent application is currently assigned to Winbond Electronics Corp.. The applicant listed for this patent is Winbond Electronics Corp.. Invention is credited to Shinya Okuno.
Application Number | 20210035624 16/528607 |
Document ID | / |
Family ID | 1000004244203 |
Filed Date | 2021-02-04 |
United States Patent
Application |
20210035624 |
Kind Code |
A1 |
Okuno; Shinya |
February 4, 2021 |
MEMORY DEVICE AND ROW-HAMMER REFRESH METHOD THEREOF
Abstract
A memory device and a row-hammer refresh method thereof are
provided. The memory device includes a memory array and a
controller. The memory array includes a plurality of normal areas
and a redundancy area adjacent to the plurality of normal areas.
The redundancy area includes a plurality of first word lines and a
plurality of second word lines which are alternately arranged. The
controller is configured to row-hammer refresh the plurality of
normal areas without row-hammer refreshing the redundancy area.
Inventors: |
Okuno; Shinya; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Winbond Electronics Corp. |
Taichung City |
|
TW |
|
|
Assignee: |
Winbond Electronics Corp.
Taichung City
TW
|
Family ID: |
1000004244203 |
Appl. No.: |
16/528607 |
Filed: |
July 31, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11C 11/40603 20130101;
G11C 11/4085 20130101 |
International
Class: |
G11C 11/406 20060101
G11C011/406; G11C 11/408 20060101 G11C011/408 |
Claims
1. A memory device comprising: a memory array, having a plurality
of normal areas and a redundancy area adjacent to the normal areas,
wherein the redundancy area comprises a plurality of first word
lines and a plurality of second word lines which are alternately
arranged; and a controller, coupled to the memory array, wherein
the controller is configured to row-hammer refresh the normal areas
without row-hammer refreshing the redundancy area regardless of a
quantity of word lines enabled in the redundancy area.
2. The memory device according to claim 1, wherein the first word
lines are not adjacent to each other, and the second word lines are
redundant.
3. The memory device according to claim 1, wherein the controller
comprises a row-hammer address calculator, and the row-hammer
address calculator is configured to calculate a word line address
that requires row-hammer refreshing in the normal areas.
4. The memory device according to claim 1, wherein the normal areas
comprise a plurality of normal word lines, wherein when the
controller determines that a first normal word line in the normal
word lines is invalid, the controller disables the first normal
word line and enables one of the first word lines.
5. The memory device according to claim 1, wherein the controller
comprises a row-hammer address calculator, and the row-hammer
address calculator is configured to calculate a word line address
that requires row-hammer refreshing in the normal areas and the
redundancy area to enable the controller to row-hammer refresh the
normal areas and the redundancy area.
6. The memory device according to claim 1, wherein the normal areas
comprise a plurality of normal word lines, wherein when the
controller determines that data of a first normal word line in the
normal word lines is invalid, the controller disables the first
normal word line and enables one of the first word lines or one of
the second word lines.
7. The memory device according to claim 6, wherein a priority for
the controller to enable the first word lines is higher than the
second word lines.
8. The memory device according to claim 1, wherein quantities of
the first word lines and the second word lines are respectively a
first quantity and a second quantity, and the second quantity is
greater than the first quantity.
9. The memory device according to claim 8, wherein when the
controller determines that the quantity of word lines enabled in
the redundancy area is greater than the first quantity, the
controller row-hammer refreshes the first word lines and the second
word lines, and when the controller determines that the quantity of
the word lines enabled in the redundancy area is less than or equal
to the first quantity, the controller does not row-hammer refresh
the first word lines and the second word lines.
10. A row-hammer refresh method adapted for a memory device,
wherein the memory device comprises a memory array and a
controller, the memory array has a plurality of normal areas and a
redundancy area adjacent to the normal areas, the redundancy area
comprises a plurality of first word lines and a plurality of second
word lines which are alternately arranged, a quantity of the first
word lines is a first quantity, and the controller is configured to
row-hammer refresh the normal areas and the redundancy area, the
row-hammer refresh method comprising: calculating a quantity of
word lines enabled in the redundancy area; comparing the quantity
of the word lines enabled in the redundancy area with the first
quantity; when the quantity of the word lines enabled in the
redundancy area is greater than the first quantity, row-hammer
refreshing the first word lines and the second word lines; and when
the quantity of the word lines enabled in the redundancy area is
less than or equal to the first quantity, not row-hammer refreshing
the first word lines and the second word lines.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The disclosure relates to a memory device and a row-hammer
refresh method thereof, and more particularly, to a memory device
and a row-hammer refresh method thereof which do not need to
frequently row-hammer refresh word lines in a redundancy area due
to the row hammer phenomenon.
Description of Related Art
[0002] When a specific word line in a dynamic random access memory
(DRAM) is repeatedly turned on multiple times, the memory cells on
the word lines adjacent to the specific word line may lose the
stored data due to the cross talk or coupling effect. This
interference phenomenon is referred to as the row hammer
phenomenon.
[0003] To address the row hammer phenomenon, the conventional
technique row-hammer refreshes the repeatedly turned-on word line
(also referred to as an aggressor word line) to protect the
adjacent word lines (also referred to as victim word lines) from
the row hammer phenomenon. However, in some DRAM structures having
a high memory cell density, it is complicated to calculate the word
line addresses of the victim word lines, so a row-hammer address
calculator having a larger area is required to calculate the word
line addresses of the victim word lines.
SUMMARY OF THE INVENTION
[0004] The invention provides a memory device and a row-hammer
refresh method thereof, in which word lines for separation are
added to a redundancy area to reduce the area of the row-hammer
address calculator. Moreover, it is not necessary to frequently
row-hammer refresh the word lines of the redundancy area, which
thereby reduces the row-hammer refresh current.
[0005] An embodiment of the invention provides a memory device. The
memory device includes a memory array and a controller. The memory
array has a plurality of normal areas and a redundancy area
adjacent to the normal areas. The redundancy area includes a
plurality of first word lines and a plurality of second word lines
which are alternately arranged. The controller is coupled to the
memory array. The controller is configured to row-hammer refresh
the normal areas without row-hammer refreshing the redundancy
area.
[0006] An embodiment of the invention provides a row-hammer refresh
method adapted for a memory device. The memory device includes a
memory array and a controller, and the memory array has a plurality
of normal areas and a redundancy area adjacent to the normal areas.
The redundancy area includes a plurality of first word lines and a
plurality of second word lines which are alternately arranged, and
a quantity of the first word lines is a first quantity. The
controller is configured to row-hammer refresh the normal areas and
the redundancy area. The row-hammer refresh method includes, but
not limited to, the following steps. A quantity of word lines
enabled in the redundancy area is calculated. The quantity of the
word lines enabled in the redundancy area is compared with the
first quantity. When the quantity of the word lines enabled in the
redundancy area is greater than the first quantity, the first word
lines and the second word lines are row-hammer refreshed. When the
quantity of the word lines enabled in the redundancy area is less
than or equal to the first quantity, the first word lines and the
second word lines are not row-hammer refreshed.
[0007] Based on the above, in some embodiments of the invention,
the memory device and the row-hammer refresh method thereof can
reduce the area of the row-hammer address calculator. Word lines
for separation are added to the redundancy area to reduce the
layout area of the row-hammer address calculator. Moreover, in the
invention, since it is not necessary to frequently row-hammer
refresh the word lines of the redundancy area, the row-hammer
refresh current can be further reduced.
[0008] To make the aforementioned more comprehensible, several
embodiments accompanied with drawings are described in detail as
follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view showing a memory device according
to an embodiment of the invention.
[0010] FIG. 2 is a schematic view showing a layout of word lines in
a memory array according to an embodiment of the invention.
[0011] FIG. 3 is a schematic view showing a layout of word lines in
a memory array according to another embodiment of the
invention.
[0012] FIG. 4 is a flowchart showing a row-hammer refresh method
according to an embodiment of the invention.
DESCRIPTION OF THE EMBODIMENTS
[0013] FIG. 1 is a schematic view showing a memory device according
to an embodiment of the invention. Referring to FIG. 1, a memory
device 100 includes a memory array 110 and a controller 120. The
memory array 110 includes a plurality of word lines and a plurality
of memory cells (not shown) and is configured to store data. The
invention does not limit the architecture of the memory array. The
controller 120 is coupled to the memory array 110, and the
controller 120 is configured to access, verify, and row-hammer
refresh the memory array 110. The invention does not limit the
architecture of the controller. The controller 120 includes a
row-hammer address calculator 130. The row-hammer address
calculator 130 is configured to calculate a word line address in
the memory array 110 that is expected to be affected by the row
hammer phenomenon and needs row-hammer refreshing. The controller
120 row-hammer refreshes the word line in the memory array 110
based on the word line address to prevent the memory cells on the
word line from losing the stored data.
[0014] FIG. 2 is a schematic view showing a layout of word lines in
a memory array according to an embodiment of the invention.
Referring to FIG. 2, the memory array 110 has a normal area 210 and
a redundancy area 220 adjacent to the normal area 210. In an
embodiment, the normal area 210 is adjacent to two sides of the
redundancy area 220, but the invention is not limited thereto. The
normal area 210 includes a plurality of normal word lines NWL and
normal memory cells (not shown). The redundancy area 220 includes a
plurality of first word lines WL1, a plurality of second word lines
DWL2, and redundancy memory cells (not shown). The plurality of
first word lines WL1 and the plurality of second word lines DWL2
are alternately arranged. In an embodiment, the second word lines
DWL2 are redundant.
[0015] In an embodiment, the quantity of the first word lines WL1
is a first quantity, the quantity of the second word lines DWL2 is
a second quantity, and the second quantity is greater than the
first quantity. It is noted that since the plurality of second word
lines DWL2 separate the plurality of first word lines WL1, the
plurality of first word lines WL1 are not adjacent to each other.
Moreover, in the redundancy area 220, the word lines adjacent to
the boundary between the redundancy area 220 and the normal area
210 are the second word lines DWL2. In an embodiment, the
controller 120 is configured to row-hammer refresh the normal area
210 without row-hammer refreshing the redundancy area 220.
[0016] For example, in an embodiment, the plurality of first word
lines WL1 include first word lines WL1_1 to WL1_11, the plurality
of second word lines DWL2 include second word lines DWL2_1 to
DWL2_13. The quantities of the first word lines WL1 and the second
word lines DWL2 are only illustrated for the convenience of
description of the embodiment, and the quantities are determined by
the actual requirements and are not limited in the invention. The
first word line WL1_1 is located between the second word lines
DWL2_1 and DWL2_2, the first word line WL1_2 is located between the
second word lines DWL2_2 and DWL2_3, and so on. Namely, the second
word lines DWL2_1 to DWL2_13 are arranged such that the first word
lines WL1_1 to WL1_11 are not adjacent to each other. Moreover, the
word line at the left boundary in the redundancy area 220 is the
second word line DWL2_1, and the word line at the right boundary in
the redundancy area 220 is the second word line DWL2_13. In an
embodiment, since the second word lines DWL2_1 to DWL2_13 are
redundant (i.e., the second word lines DWL2_1 to DWL2_13 do not
need to be turned on), the second word lines DWL2_1 to DWL2_13 can
separate the row hammer between the first word lines WL1_1 to
WL1_11 and the row hammer to the normal area 210, so that it is not
necessary to consider the row hammer issue of the first word lines
WL1_1 to WL1_11 in the redundancy area 220. Accordingly, in this
embodiment, the row-hammer address calculator 130 in the controller
120 does not need to calculate the word line address that requires
row-hammer refreshing in the redundancy area 220, but only needs to
calculate the word line address that requires row-hammer refreshing
in the normal area 210, to enable the controller 120 to row-hammer
refresh the word line of the normal area 210 to prevent the row
hammer issue in the normal area 210. Since it is not necessary to
calculate the word line address that requires row-hammer refreshing
in the redundancy area 220 and it is not necessary to frequently
row-hammer refresh the redundancy area 220, it is possible to save
the layout area of the row-hammer address calculator 130 originally
provided for the redundancy area 220 and reduce the row-hammer
refresh current thereof.
[0017] In a common operation, the controller 120 accesses and
row-hammer refreshes the normal memory cells through the plurality
of normal word lines NWL. In an embodiment, when the controller 120
determines that any one of the plurality of normal word lines NWL
is invalid, the controller 120 disables the invalid normal word
line and enables one of the plurality of first word lines WL1 to
replace the invalid normal word line. For example, when the
controller 120 performs data verification and determines that one
of the plurality of normal word lines NWL is invalid, the
controller turns off the invalid normal word line to prohibit
access and turns on the first word line WL1_1 to replace the
invalid normal word line.
[0018] FIG. 3 is a schematic view showing a layout of word lines in
a memory array according to another embodiment of the invention.
Referring to FIG. 3, the memory array 110 has a normal area 310 and
a redundancy area 320 adjacent to the normal area 310. In another
embodiment, the normal area 310 is adjacent to two sides of the
redundancy area 320, but the invention is not limited thereto. The
normal area 310 includes a plurality of normal word lines NWL and
normal memory cells (not shown). The redundancy area 320 includes a
plurality of first word lines WL1, a plurality of second word lines
WL2, and redundancy memory cells (not shown). The plurality of
first word lines WL1 and the plurality of second word lines WL2 are
alternately arranged. In another embodiment, the second word lines
WL2 are not redundant.
[0019] In another embodiment, the redundancy area 320 may include a
non-volatile memory, a laser fuse, or an anti-fuse, but the
invention is not limited thereto.
[0020] In another embodiment, the quantity of the first word lines
WL1 is a first quantity, the quantity of the second word lines WL2
is a second quantity, and the second quantity is greater than the
first quantity. It is noted that since the plurality of second word
lines WL2 separate the plurality of first word lines WL1, the
plurality of first word lines WL1 are not adjacent to each other.
Moreover, in the redundancy area 320, the word lines adjacent to
the boundary between the redundancy area 320 and the normal area
310 are the second word lines WL2. In another embodiment, the
controller 120 is configured to row-hammer refresh the normal area
310 and the redundancy area 320.
[0021] For example, in another embodiment, the plurality of first
word lines WL1 include first word lines WL1_1 to WL1_11, and the
plurality of second word lines WL2 include second word lines WL2_1
to WL2_13. The quantities of the first word lines WL1 and the
second word lines WL2 are only illustrated for the convenience of
description of the embodiment, and the quantities are determined by
the actual requirements and are not limited in the invention. The
first word line WL1_1 is located between the second word lines
WL2_1 and WL2_2, the first word line WL1_2 is located between the
second word lines WL2_2 and WL2_3, and so on. Namely, the second
word lines WL2_1 to WL2_13 are arranged such that the first word
lines WL1_1 to WL1_11 are not adjacent to each other. Moreover, the
word line at the left boundary in the redundancy area 320 is the
second word line WL2_1, and the word line at the right boundary in
the redundancy area 320 is the second word line WL2_13. In another
embodiment, since the second word lines WL2_1 to WL2_13 are not
redundant (i.e., the second word lines WL2_1 to WL2_13 need to be
turned on by the controller 120), it is necessary to consider the
row hammer issue between the first word lines WL1_1 to WL1_11 and
the second word lines WL2_1 to WL2_13 in the redundancy area 320.
Therefore, in another embodiment, in addition to calculating the
word line address that requires row-hammer refreshing in the normal
area 310, the row-hammer address calculator 130 of the controller
120 also needs to calculate the word line address that requires
row-hammer refreshing in the redundancy area 320, to enable the
controller 120 to row-hammer refresh the word line of the normal
area 310 and the redundancy area 320 to prevent the row hammer
issue.
[0022] In another embodiment, when the controller 120 determines
that any one of the plurality of normal word lines NWL is invalid,
the controller 120 disables the invalid normal word line NWL and
enables one of the plurality of first word lines WL1 or the
plurality of second word lines WL2 to replace the invalid normal
word line NWL. In another embodiment, the priority for the
controller 120 to enable the plurality of first word lines WL1 is
higher than the plurality of second word lines WL2. When the
controller 120 determines that the quantity of the word lines
enabled in the redundancy area 320 is less than or equal to the
total quantity (i.e., the first quantity) of the first word lines,
the controller 120 does not row-hammer refresh the first word lines
WL1 and the second word lines WL2. When the controller 120
determines that the quantity of the word lines enabled in the
redundancy area 320 is greater than the quantity (i.e., the first
quantity) of the first word lines, the controller 120 row-hammer
refreshes the first word lines WL1 and the second word lines
WL2.
[0023] For example, in another embodiment, when the controller 120
performs data verification and determines that one of the plurality
of normal word lines NWL is invalid, the controller 120 turns off
the invalid normal word line (not shown) to forbid access, and
prioritizingly turns on one of the first word lines WL1_1 to WL1_11
(e.g., turning on the first word line WL1_1) to replace the invalid
normal word line. When the controller 120 determines that the next
normal word line is invalid, the controller 120 may turn on the
first word line WL1_2 to replace the next invalid normal word line,
and so on. When the controller 120 determines that the next normal
word line is invalid and all the first word lines WL1_1 to WL1_11
in the redundancy area 320 are turned on, the controller 120 may
turn on the second word line WL2_1. After the controller 120 turns
on the second word line WL2_1, when the controller 120 determines
that the next normal word line is invalid and all the first word
lines WL1_1 to WL1_11 in the redundancy area 320 are turned on, the
controller 120 may turn on the second word line WL2_2, and so
on.
[0024] In another embodiment, when the controller 120 determines
that the quantity of the word lines enabled in the redundancy area
320 is less than or equal to the total quantity (i.e., the first
quantity) of the first word lines (e.g., when only the first word
line WL1_1 and the first word line WL1_2 in the first word lines
WL1 are enabled, the quantity of the enabled word lines is 2, which
is less than or equal to the total quantity (i.e., 11) of the first
word lines WL1), since the first word line WL1_1 and the first word
line WL1_2 which are enabled in the redundancy area 320 are
separated by the second word line WL2_2 which is not turned on, it
is not necessary to consider the row hammer issue. Therefore, the
controller 120 does not need to row-hammer refresh the first word
lines WL1_1 to WL1_11 and the second word lines WL2_1 to WL2_13 in
the redundancy area 320.
[0025] In another embodiment, when the controller 120 determines
that the quantity of the word lines enabled in the redundancy area
320 is greater than the total quantity (i.e., the first quantity)
of the first word lines (e.g., when the first word lines WL1_1 to
WL1_11 and the second word lines WL2_1 to WL2_2 are all enabled,
the quantity of the enabled word lines is 13, which is greater than
the total quantity (i.e., 11) of the first word lines WL1), since
the first word lines WL1_1 to WL1_2 and the second word lines WL2_1
to WL2_2 in the redundancy area 320 are all enabled and are
adjacent to each other, and the enablement of the second word line
WL2_1 also affects the word line of the left normal area, it is
necessary to consider the row hammer issue. Therefore, in another
embodiment, the controller 120 needs to row-hammer refresh the
first word lines WL1_1 to WL1_2 and the second word lines WL2_1 to
WL2_2 in the redundancy area 320, or row-hammer refresh all the
first word lines WL1_1 to WL1_11 and the second word lines WL2_1 to
WL2_13 in the redundancy area 320. The row-hammer refreshing
strategy is determined according to the design requirements, and
the invention is not limited thereto. Accordingly, in another
embodiment, the row-hammer address calculator 130 of the controller
120 needs to calculate the word line address that requires
row-hammer refreshing in the normal area 310 and the redundancy
area 320, to enable the controller 120 to row-hammer refresh the
word line of the normal area 310 and the redundancy area 320 to
prevent the row hammer issue. In another embodiment, since it is
still necessary to calculate the word line address that requires
row-hammer refreshing in the redundancy area 320, the layout area
in the row-hammer address calculator 130 originally provided for
the redundancy area 320 cannot be saved, but the row-hammer refresh
current can still be reduced.
[0026] FIG. 4 is a flowchart showing a row-hammer refresh method
according to an embodiment of the invention. In step S410, the
controller calculates a quantity of the word lines enabled in the
redundancy area. Next, in step S420, the controller compares the
quantity of the word lines enabled in the redundancy area with a
first quantity. When the quantity of the word lines enabled in the
redundancy area is greater than the first quantity, step S430 is
performed. When the quantity of the word lines enabled in the
redundancy area is less than or equal to the first quantity, step
S440 is performed. In step S430, when the quantity of the word
lines enabled in the redundancy area is greater than the first
quantity, the controller row-hammer refreshes the first word lines
and the second word lines. In step S440, when the quantity of the
word lines enabled in the redundancy area is less than or equal to
the first quantity, the controller does not row-hammer refresh the
first word lines and the second word lines.
[0027] In summary of the above, in some embodiments of the
invention, the memory device and the row-hammer refresh method
thereof can reduce the area of the row-hammer address calculator.
Word lines for separation are added to the redundancy area to
protect the redundancy area from the row hammer phenomenon, so that
it is not necessary to calculate the word line address with row
hammer in the redundancy area, and thereby the layout area of the
row-hammer address calculator can be reduced. Moreover, in the
invention, since it is not necessary to frequently row-hammer
refresh the word lines of the redundancy area, the row-hammer
refresh current can be further reduced. On the other hand, in the
invention, the word lines for separation may be further enabled,
and the row-hammer refreshing approach may be adjusted according to
the quantity of the word lines enabled in the redundancy area, to
reduce the row-hammer refresh current.
[0028] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed
embodiments without departing from the scope or spirit of the
disclosure. In view of the foregoing, it is intended that the
disclosure covers modifications and variations provided that they
fall within the scope of the following claims and their
equivalents.
* * * * *