U.S. patent application number 16/817043 was filed with the patent office on 2020-07-02 for operation method of nonvolatile memory device and storage device.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Jinbae BANG, Daeseok BYEON, Dongsup JIN, Jisu KIM, Jun Jin KONG, Eun Chu OH, Dongjin SHIN, Hong Rak SON, Taehyun SONG, Pilsang YOON.
Application Number | 20200211656 16/817043 |
Document ID | / |
Family ID | 63711617 |
Filed Date | 2020-07-02 |
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United States Patent
Application |
20200211656 |
Kind Code |
A1 |
OH; Eun Chu ; et
al. |
July 2, 2020 |
OPERATION METHOD OF NONVOLATILE MEMORY DEVICE AND STORAGE
DEVICE
Abstract
An method of operating a nonvolatile memory device including a
plurality of memory cells comprises receiving a read command from
an external device, in response to the read command, performing,
based on a reference voltage, a first cell counting operation with
respect to the plurality of memory cells, adjusting at least one
read voltage of first through nth read voltages (where n is a
natural number greater than 1) based on a first result of the first
cell counting operation, and performing, based on the adjusted at
least one read voltage, a read operation corresponding to the read
command with respect to the plurality of memory cells.
Inventors: |
OH; Eun Chu; (Hwaseong-si,
KR) ; YOON; Pilsang; (Hwaseong-si, KR) ; KONG;
Jun Jin; (Yongin-si, KR) ; KIM; Jisu; (Seoul,
KR) ; SON; Hong Rak; (Anyang-si, KR) ; BANG;
Jinbae; (Anyang-si, KR) ; BYEON; Daeseok;
(Seongnam-si, KR) ; SONG; Taehyun; (Suwon-si,
KR) ; SHIN; Dongjin; (Hwaseong-si, KR) ; JIN;
Dongsup; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
63711617 |
Appl. No.: |
16/817043 |
Filed: |
March 12, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16539290 |
Aug 13, 2019 |
10607708 |
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16817043 |
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16003729 |
Jun 8, 2018 |
10381090 |
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16539290 |
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15475670 |
Mar 31, 2017 |
10229749 |
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16003729 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11C 2211/5634 20130101;
G11C 16/26 20130101; G11C 16/0466 20130101; G11C 29/50004 20130101;
G11C 11/5628 20130101; G11C 29/021 20130101; G11C 2211/563
20130101; G11C 16/28 20130101; G11C 16/10 20130101; G11C 29/028
20130101; G11C 11/5642 20130101; G11C 2029/5004 20130101; G11C
16/0483 20130101; G11C 11/5671 20130101; G11C 16/04 20130101; G11C
16/3495 20130101 |
International
Class: |
G11C 16/28 20060101
G11C016/28; G11C 29/02 20060101 G11C029/02; G11C 16/04 20060101
G11C016/04; G11C 29/50 20060101 G11C029/50; G11C 16/26 20060101
G11C016/26; G11C 16/34 20060101 G11C016/34; G11C 11/56 20060101
G11C011/56; G11C 16/10 20060101 G11C016/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2018 |
KR |
10-2018-0002919 |
Claims
1. A storage device comprising: a nonvolatile memory device
including a plurality of memory blocks, each of the plurality of
memory blocks including a plurality of memory cells stacked in a
direction perpendicular to a substrate; and a memory controller
configured to transmit a first read command to the nonvolatile
memory device; wherein, in response to the first read command, the
nonvolatile memory device is configured to: perform, using a
reference voltage, a first sensing operation on a first memory
cells connected with a first wordline, among of the plurality of
memory cells; adjust at least one read voltage of a plurality of
read voltages based on a result of the first sensing operation; and
perform, using the adjusted at least one read voltage, at least one
second sensing operation on the first memory cells to read first
page data stored in the first memory cells.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 16/539,290, filed on Aug. 13, 2019, which is a continuation of
U.S. application Ser. No. 16/003,729, filed on Jun. 8, 2018, now
granted as U.S. Pat. No. 10,381,090 on Aug. 13, 2019, which is a
continuation-in-part of U.S. patent application Ser. No.
15/475,670, filed on Mar. 31, 2017, now granted as U.S. Pat. No.
10,229,749 on Mar. 12, 2019, and claims priority under 35 U.S.C.
.sctn. 119 to Korean Patent Application No. 10-2018-0002919, filed
on Jan. 9, 2018, the entire contents of each of which are hereby
incorporated by reference.
BACKGROUND
[0002] Inventive concepts relates to semiconductor memories, and
more particularly, to an operation method of a nonvolatile memory
device.
[0003] A semiconductor memory device is implemented using a
semiconductor such as silicon Si, germanium Ge, gallium arsenide
GaAs, indium phosphide InP, etc. A semiconductor memory device may
be classified as a volatile memory device or a nonvolatile memory
device.
[0004] A volatile memory device loses may loses stored data when a
power supply is interrupted. A nonvolatile memory device may retain
stored data even when a power supply is interrupted. Examples of
the volatile memory device include a SRAM (Static RAM), a DRAM
(Dynamic RAM), a SDRAM (Synchronous DRAM), etc. Examples of the
nonvolatile memory device are a read only memory (ROM), a
programmable ROM (PROM), an electrically programmable ROM (EPROM),
an electrically erasable and programmable ROM (EEPROM), a flash
memory device, a phase change RAM (PRAM), a magnetic RAM (MRAM), a
resistive RAM (RRAM), a ferroelectric RAM (FRAM), etc.
[0005] A flash memory may include charge trap flash (CTF) memory
cells. The charge trap flash (CTF) memory cell may remember a
program state by storing charges in a charge storage layer. Charges
stored in the charge storage layer of the charge trap flash (CTF)
memory cells are programmed and then flow into a channel. As
charges flow into the channel, a distribution of threshold voltages
of the charge trap flash (CTF) memory cells may be changed. Because
of a physical characteristic of the charge trap flash (CTF) memory
cells, reliability of data stored in the memory cells may be
degraded.
SUMMARY
[0006] A method of operating a nonvolatile memory device according
some example embodiments of inventive concepts includes receiving a
read command from an external device, in response to the read
command, performing, based on a reference voltage, a first cell
counting operation with respect to the plurality of memory cells,
adjusting at least one read voltage of first through nth read
voltages (where n is a natural number greater than 1) based on a
first result of the first cell counting operation, and performing,
based on the adjusted at least one read voltage, a read operation
corresponding to the read command with respect to the plurality of
memory cells.
[0007] A method of operating a nonvolatile memory device including
a plurality of memory cells according to some example embodiments
of inventive concepts includes receiving a read command from an
external device, in response to the read command, performing a
multi-sensing read operation based on at least two reference
voltages, adjusting at least one of first through nth read voltages
(n is a natural number greater than 1) based on a first result of
the multi-sensing read operation, and performing, based on the
first through nth read voltages, a read operation corresponding to
the read command with respect to the plurality of memory cells.
[0008] A storage device according to some example embodiments of
inventive concepts comprises a nonvolatile memory device including
a plurality of memory cells and reading data stored in the
plurality of memory cells based on first through nth read voltages
(where n is a natural number greater than 1), and a memory
controller configured to transmit parameters including information
about a read voltage level change of each of the first through nth
read voltages after transmitting a read command and an address to
the nonvolatile memory device. The nonvolatile memory device is
configured to perform a sensing operation with respect to the
plurality of memory cells based on a reference voltage, perform a
cell counting operation based on the sensing operation, adjust at
least one read voltage of the first through nth read voltages based
on a result of the cell counting operation and the parameters, and
read data stored in the plurality of memory cells based on the
adjusted at least one read voltage.
BRIEF DESCRIPTION OF THE FIGURES
[0009] Embodiments of inventive concepts will be described below in
more detail with reference to the accompanying drawings.
Embodiments of inventive concepts may, however, be implemented in
different forms and should not be constructed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of inventive concepts to those skilled
in the art. Like numbers refer to like elements throughout.
[0010] FIG. 1 is a block diagram illustrating a nonvolatile memory
storage system according to some example embodiments of inventive
concepts.
[0011] FIG. 2 is a block diagram illustrating a nonvolatile memory
storage system according to some example embodiments of inventive
concepts.
[0012] FIG. 3 is a block diagram illustrating a memory controller
illustrated in FIG. 1.
[0013] FIG. 4 is a block diagram illustrating a memory controller
illustrated in FIG. 2.
[0014] FIG. 5 is a block diagram illustrating a nonvolatile memory
device according to some example embodiments of inventive
concepts.
[0015] FIG. 6 is a circuit diagram illustrating a memory block
according to some example embodiments of inventive concepts.
[0016] FIG. 7 is a distribution diagram illustrating an initial
program threshold voltage distribution of memory cells and a
changed threshold voltage distribution of the memory cells as time
goes by.
[0017] FIG. 8 is a view illustrating a read voltage level lookup
table according to example embodiments of inventive concepts.
[0018] FIG. 9 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to some example embodiments of inventive concepts.
[0019] FIG. 10 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 8.
[0020] FIG. 11 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to some example embodiments of inventive concepts.
[0021] FIG. 12 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 10.
[0022] FIG. 13 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to example embodiments of inventive concepts.
[0023] FIG. 14 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 12.
[0024] FIG. 15 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to some example embodiments of inventive concepts.
[0025] FIG. 16 is a distribution diagram illustrating a threshold
voltage distribution of memory cells according to some example
embodiments of inventive concepts.
[0026] FIG. 17 is a flow chart describing a read operation of a
nonvolatile memory device according to some example embodiments of
inventive concepts.
[0027] FIGS. 18A and 18B are views for explaining an operation
method according to FIG. 17.
[0028] FIG. 19 is a flow chart describing a read operation of a
nonvolatile memory device according to some inventive concepts.
[0029] FIG. 20 is view for explaining an operation method of FIG.
19.
[0030] FIG. 21 is a block diagram illustrating a nonvolatile memory
device according to some example embodiments of inventive
concepts.
[0031] FIG. 22 is a flow chart describing an operation of a
nonvolatile memory device of FIG. 21.
[0032] FIG. 23 is a view for explaining an operation method of FIG.
22.
[0033] FIGS. 24A and 24B are views for explaining a multi-sensing
read operation.
[0034] FIG. 25 is a view for explaining a read operation of a
nonvolatile memory device of FIG. 21.
[0035] FIG. 26 is a flow chart describing an operation of a
nonvolatile memory device of FIG. 21.
[0036] FIG. 27 is a view for explaining an operation method of FIG.
26.
[0037] FIG. 28 is a view for explaining an operation of a
nonvolatile memory device of FIG. 21.
[0038] FIG. 29 is a flow chart describing an operation of a
nonvolatile memory device according to inventive concepts.
[0039] FIG. 30 is a timing diagram illustrating a signal received
by a nonvolatile memory device according to an operation method of
FIG. 29.
[0040] FIG. 31 is a flow chart describing an operation of a memory
controller according to inventive concepts.
[0041] FIG. 32 is a block diagram illustrating a solid state drive
(SSD) system including a storage system according to example
embodiments of inventive concepts.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0042] FIG. 1 is a block diagram illustrating a nonvolatile memory
storage system according to some example embodiments of inventive
concepts. Referring to FIG. 1, a nonvolatile memory storage system
100 may include a memory controller 110 and a nonvolatile memory
device 120.
[0043] The memory controller 110 may control the nonvolatile memory
device 120 under the control of an external device. For example,
the memory controller 110 may transmit an address ADDR, a read
command CMD_r, and a control signal CNTL to read data DATA stored
in the nonvolatile memory device 120.
[0044] The nonvolatile memory device 120 may operate under the
control of the memory controller 110. For example, the nonvolatile
memory device 120 may receive the address ADDR, a read command
CMD_r, and a control signal CNTL from the memory controller 110.
The nonvolatile memory device 120 may transmit data DATA
corresponding to the received address ADDR to the memory controller
110 in response to the received signals.
[0045] The memory controller 110 may include a read voltage level
lookup table (RVL LUT) 111. The RVL LUT 111 may include information
that maps a relation among read voltage level changes according to
a reference cell count. The reference cell count is a value which
is set to adjust a read voltage. The RVL LUT 111 will be described
with reference to FIGS. 7 and 8.
[0046] After a program of the memory cells is completed, a
threshold voltage distribution may be changed. Accordingly, when a
read operation of the memory cells is performed using a desired
(or, alternatively, predetermined) read voltage, an error may
occur. To reduce the number of errors and occurrence probability of
the error, the nonvolatile memory device 120 may adjust a read
voltage level. A specific method of adjusting a level of the read
voltage will be described in detail with reference to drawings
below.
[0047] The memory controller 110 may transmit information of the
read voltage level lookup table RVL LUT 111 to the nonvolatile
memory device 120 together with the read command CMD_r. For
example, the memory controller 110 may transmit information of the
RVL LUT 111 to the nonvolatile memory device 120 only once together
with the read command CMD_r. In some example embodiments, whenever
transmitting the read command CMD_r to the nonvolatile memory
device 120, the memory controller 110 may transmit the information
of the RVL LUT 111 together. In some example embodiments, in
response to a request of the nonvolatile memory device 120, the
memory controller 110 may transmit the information of the read
voltage level lookup table RVL LUT 111 to the nonvolatile memory
device 120 together with the read command CMD_r. In some example
embodiments, in response to a request of a user, the memory
controller 110 may transmit the information of the RVL LUT 111 to
the nonvolatile memory device 120 together with the read command
CMD_r.
[0048] For example, the read voltage level lookup table RVL LUT 111
may be periodically updated. The read voltage level lookup table
RVL LUT 111 may be updated according to a request of a user. When
the read voltage level lookup table RVL LUT 111 is updated, the
memory controller 110 may transmit the information of the read
voltage level lookup table RVL LUT 111 together.
[0049] The memory controller 110 may transmit a control signal CNTL
to the nonvolatile memory device 120 to adjust a read voltage level
of the nonvolatile memory device 120. The nonvolatile memory device
120 may adjust the read voltage level in response to the control
signal CNTL.
[0050] In response to the read voltage, the nonvolatile memory
device 120 may count memory cells that form a current path in a
channel. Otherwise, the nonvolatile memory device 120 may count
memory cells that cut off a current path of a channel in response
to the read voltage. A cell count may be a counting result of
memory cells that form a current path in a channel or memory cells
that cut off a current path of a channel in response to the read
voltage. A count of the memory cells that form a current path in a
channel in response to the read voltage is an on-cell count and a
count of the memory cells that cut off a current path of a channel
in response to the read voltage is an off-cell count.
[0051] The nonvolatile memory device 120 may receive the
information of the RVL LUT 111 from the memory controller 110. The
nonvolatile memory device 120 may store the information of the RVL
LUT 111 in a ROM and/or in a memory (e.g., a code memory) as a part
of a firmware code of the nonvolatile memory device 120. The
nonvolatile memory device 120 may adjust the read voltage level
using the information of the RVL LUT 111 and the cell count in
response to the control signal CNTL.
[0052] The nonvolatile memory device 120 may read data DATA through
the adjusted read voltage. The nonvolatile memory device 120 may
transmit the read data DATA to the memory controller 110. The
memory controller 110 may calculate read voltage level changes
based on access environment information of when accessing the
nonvolatile memory device 120. The environment information will be
described with reference to FIG. 2.
[0053] FIG. 2 is a block diagram illustrating a nonvolatile memory
storage system according to some example embodiments of inventive
concepts. Referring to FIG. 2, a nonvolatile memory storage system
200 may include a memory controller 210 and a nonvolatile memory
device 220. Since the memory controller 210 and the nonvolatile
memory device 220 illustrated in FIG. 2 are similar to or the same
as the memory controller 110 and the nonvolatile memory device 120
illustrated in FIG. 1, a description thereof is omitted.
[0054] The memory controller 210 may include a RVL LUT 211 and a
read voltage level calculator RVL CAL 212. The RVL LUT 211 may
include information that maps a relation among read voltage level
changes according to a reference cell count.
[0055] The RVL CAL 212 may include a hardware configuration, a
software configuration, or a hybrid configuration thereof. The RVL
CAL 212 may include a special-purpose hardware circuit configured
to perform a specific operation. The RVL CAL 212 may include at
least one processor core that can execute an instruction set of a
program code configured to perform the specific operation.
[0056] The RVL CAL 212 may calculate read voltage level changes
based on access environment information. The access environment
information may include at least one of a location of a target
block, a location of a target string selection line, a location of
a target word line, temperature, program/erase count, and cell
count.
[0057] The target block information may include an address of a
memory block in which a read operation is performed or information
about a location of the target block in all memory blocks (e.g.,
information about whether the target block is located at the center
of the memory blocks or outskirts of the memory blocks). The target
string selection line information may include an address of a
string selection line corresponding to a page in which a read
operation is performed or information about a location of the
string selection line in the target block.
[0058] The target word line information may include information
about an address of a word line connected to a page in which a read
operation is performed and/or information about a location of a
word line in the target block. The temperature information may
indicate a temperature of when the controller 210 performs a read
operation on the nonvolatile memory device 220.
[0059] The program and erase count indicates the number of times
that program and erase operations are performed at a target block.
An on-cell count may indicate the number of memory cells that forms
a current path on a channel in response to a read voltage of the
nonvolatile memory device 220. An off-cell count may indicate the
number of memory cells that forms a current path on a channel in
response to a read voltage of the nonvolatile memory device
220.
[0060] The memory controller 210 may transmit at least one of
information of the RVL LUT 211 and information about read voltage
level changes calculated in the RVL CAL 212 to the nonvolatile
memory device 220.
[0061] The memory controller 210 illustrated in FIG. 2 includes the
RVL LUT 211 and the RVL CAL 212. However, inventive concepts are
not limited thereto and the memory controller 210 may include only
the RVL CAL 212. When the memory controller 210 calculates read
voltage level changes using the RVL CAL 212, the memory controller
210 may directly reflect access environment information of when
accessing the nonvolatile memory device 120. Because of this, the
memory controller 210 can more accurately calculate read voltage
level changes reflected in a read voltage.
[0062] FIG. 3 is a block diagram illustrating a memory controller
illustrated in FIG. 1. Referring to FIG. 3, the memory controller
110 may include a RVL LUT 111, a processor 112, a RAM 113, an ECC
(error correcting code) engine 114, a randomizer 115, a ROM 116, a
host interface 117, a memory interface 118, and a bus 119.
[0063] The processor 112 may include at least one processor core
that can execute an instruction set of a program code configured to
perform a specific operation. Each of the ECC engine 114 and the
randomizer 115 may include a hardware configuration, a software
configuration, or a hybrid configuration thereof to perform
operations that will be described later. Each of the ECC engine 114
and the randomizer 115 may include a special-purpose hardware
circuit configured to perform a specific operation. Each of the ECC
engine 114 and the randomizer 115 may include at least one
processor core that can execute an instruction set of a program
code configured to perform the specific operation.
[0064] The RVL LUT 111 may be managed on a per-memory block basis.
The RVL LUT 111 may be desired (or, alternatively, predetermined)
or updated according to a program and erase count of the memory
block and a characteristic of the memory block. The RVL LUT 111 may
be managed on a per-word line basis. The RVL LUT 111 may be desired
(or, alternatively, predetermined) or updated according to a
location of the word line. The RVL LUT 111 may be managed in units
of read voltages. The RVL LUT 111 may be desired (or,
alternatively, predetermined) or updated on each of the read
voltages.
[0065] The RVL LUT 111 may be stored in the RAM 113 and may be
updated by the processor 112. The RVL LUT 111 may be stored in the
ROM 116 in the form of firmware. The RVL LUT 111 updated by the
processor 112 may be flushed, e.g., sent, to the nonvolatile memory
device 120.
[0066] The processor 112 may control an overall operation of the
memory controller 110. The processor 112 may execute a command code
of firmware stored in the ROM 116. The RAM 113 may operate as at
least one of a buffer memory, a cache memory, an operation memory,
and a main memory. The RAM 113 may store the RVL LUT 111. The RAM
113 may be a SRAM.
[0067] The ECC engine 114 may generate an error correction code on
data to be stored in the nonvolatile memory device 120. The ECC
engine 114 may detect an error of data DATA read from the
nonvolatile memory device 120, and may correct the detected error
based on the error correction code.
[0068] The randomizer 115 may randomize data DATA to be stored in
the nonvolatile memory device 120. For example, at least some of
the memory cells of the nonvolatile memory device 120 may be triple
level cells (TLC) each of which stores 3-bit data. In this case,
each of the triple level cells (TLC) may be programmed to have one
of an erase state and a plurality of program states. The randomizer
115 may randomize data DATA so that program states of memory cells
connected to one word line have the same ratio. When randomized
data is stored in the memory cells connected to one word line, the
number of memory cells having the erase state among the memory
cells connected one word line and the number of memory cells having
each program state among the memory cells connected one word line
may be the same.
[0069] The ROM 116 may store various types of information required
to operate the memory controller 110. The ROM 116 may store various
types of information in the form of firmware.
[0070] The memory controller 110 may communicate with an external
device (e.g., a host) through the host interface 117. The memory
controller 110 may communicate with the nonvolatile memory device
120 through the memory interface 118. The host interface 117 may
include various interfaces such as a USB (universal serial bus), a
MMC (multimedia card), an eMMC (embedded MMC), a PCI (peripheral
component interconnection), a PCI-E (PCI-express), an ATA (advanced
technology attachment), a serial-ATA, a parallel-ATA, a SCSI (small
computer small interface), an ESDI (enhanced small disk interface),
an IDE (integrated drive electronics), a MIPI (mobile industry
processor interface), a NVMe (nonvolatile memory-express), and/or
other elements.
[0071] The bus 119 may connect the RVL LUT 111, the processor 112,
the RAM 113, the ECC engine 114, the randomizer 115, the ROM 116,
the host interface 117, and the memory interface 118 to one
another. The RVL LUT 111, the processor 112, the RAM 113, the ECC
engine 114, the randomizer 115, the ROM 116, the host interface
117, and the memory interface 118 may communicate with one another
through the bus 119.
[0072] As described above, the memory controller 110 may transmit a
read command CMD_r and information of the RVL LUT 111 to the
nonvolatile memory device 120 together. The nonvolatile memory
device 120 may adjust a read voltage level with reference to the
read command CMD_r and the information of the RVL LUT 111.
[0073] FIG. 4 is a block diagram illustrating a memory controller
illustrated in FIG. 2. The memory controller 210 may include a
processor 201, a RAM 203, an ECC engine 205, a randomizer 207, a
data pattern modulator 209, a RVL CAL 212, a ROM 213, a host
interface 215, a memory interface 217, and a bus 219.
[0074] Since the processor 201, the ECC engine 205, the randomizer
207, the ROM 213, the host interface 215, the memory interface 217,
and the bus 219 are similar to or the same as the processor 112,
the ECC engine 114, the randomizer 115, the ROM 116, the host
interface 117, the memory interface 118, and the bus 119, a
description thereof is omitted.
[0075] A RVL LUT 211 may be stored in the RAM 203 and may be
updated by the processor 201. The RVL LUT 211 may be stored in the
ROM 213 in the form of firmware. However, inventive concepts are
not limited thereto, the RVL LUT 211 updated by the processor 201
may be flushed to the nonvolatile memory device 220.
[0076] The data pattern modulator 209 may include a hardware
configuration, a software configuration, or a hybrid configuration
thereof to perform operations that will be described later. The
data pattern modulator 209 may include a special-purpose hardware
circuit configured to perform a specific operation. The data
pattern modulator 209 may include at least one processor core that
can execute an instruction set of a program code configured to
perform the specific operation.
[0077] The data pattern modulator 209 may reduce the number of data
corresponding to an error-prone program state to prevent, or reduce
the likelihood of, deterioration of data stored in memory cells of
the nonvolatile memory device 220. When the nonvolatile memory
device 220 includes triple level cells (TLC), memory cells included
in the nonvolatile memory device 220 may be programmed to one of an
erase state and first through seventh program states. At this time,
a threshold voltage of the seventh program state may have the
highest level. The data pattern modulator 209 may reduce the number
of memory cells programmed to the seventh program state by reducing
the number of 3-bit data corresponding to the seventh program
state.
[0078] FIG. 5 is a block diagram illustrating a nonvolatile memory
device according to example embodiments of inventive concepts.
[0079] Referring to FIG. 5, a nonvolatile memory device 300 may
include a memory cell array 310, an address decoder 320, a control
logic and voltage generator 330, a page buffer 340, a cell counter
350, and an input/output circuit 360. The nonvolatile memory device
300 illustrated in FIG. 5 may be similar to or the same as the
nonvolatile memory devices 120 and 220 illustrated in FIGS. 1 and
2.
[0080] The memory cell array 310 may include a plurality of memory
blocks (e.g., BLK1.about.BLKn, where n is an integer equal to or
greater than 2). Each of the memory blocks includes a plurality of
strings. Each of the strings is connected to a plurality of bit
lines BL. Each of the strings is connected to a plurality of memory
cells. The memory cells are connected to a plurality of word lines
WL respectively. Each memory cell may be provided as either a
triple-level cell (TLC) or a quadruple-level cell (QLC) including
bits greater than 2 bits. The memory cell array 310 will be
described with reference to FIG. 6.
[0081] The address decoder 320 is connected to the memory cell
array 310 through a plurality of word lines WLs, at least one
string selection line SSL(s), and at least one ground selection
line GSL(s). The address decoder 320 may receive an address ADDR
from the memory controller 110 or 210. The address decoder 320 is
configured to decode the received address ADDR. The address decoder
320 may control a voltage applied to the word lines WLs based on
the decoded address ADDR.
[0082] The control logic and voltage generator 330 may include a
cell count comparison circuit 331 and a read voltage level selector
332. The control logic and voltage generator 330 may control the
address decoder 320 and the input/output circuit 360. The control
logic and voltage generator 330 may receive a read command CMD_r.
The control logic and voltage generator 330 may control the address
decoder 320, the page buffer 340, and the input/output circuit 360
to perform a read operation in response to the received read
command CMD_r.
[0083] The control logic and voltage generator 330 may perform a
cell count comparison operation at a specific point in time of the
read operation. When performing at least one of a plurality of read
operations, the control logic and voltage generator 330 may perform
a cell count comparison operation together. The cell count
comparison operation is an operation of comparing a reference cell
count with a cell count based on the read voltage. The cell count
comparison circuit 331 may refer to information of the RVL LUT 111
or 211 included in the read command CMD_r to perform the cell count
comparison operation. The cell count comparison circuit 331 may
refer to information of read voltage level changes calculated from
the RVL CAL 212. The cell count comparison circuit 331 may refer to
a cell count nC provided from the cell counter 350.
[0084] In one read operation, the cell count comparison circuit 331
may compare the reference cell count with the cell count nC based
on one read voltage. In the plurality of read operations, the cell
count comparison circuit 331 may perform the cell count comparison
operation several times. The cell count comparison circuit 331 may
transmit a comparison result to the read voltage level selector
332. The read voltage level selector 332 may receive the comparison
result from the cell count comparison circuit 331.
[0085] The read voltage level selector 332 may select a read
voltage level through the comparison result. The read voltage level
selector 332 may refer to the information of the read voltage level
changes of the RVL LUT 111 to select the read voltage level. The
read voltage level selector 332 may adjust at least one level of
the read voltages not used in the read operation. The read voltage
level selector 332 may output a new read voltage RD' having an
adjusted voltage level. The cell count comparison circuit 331 and
the read voltage level selector 332 may be implemented in the form
of hardware.
[0086] The cell counter 350 may count a memory cell (e.g., on-cell)
that forms a current path in a channel in response to the read
voltage in a specific time. The cell counter 350 may count a memory
cell (e.g., off-cell) that cuts off a current path of a channel in
response to the read voltage in another or the same specific time.
The cell counter 350 may count a memory cell (e.g., on-cell) that
forms a current path in a channel or a memory cell (e.g., off-cell)
that cuts off a current path of a channel in response to the read
voltage in one of the plurality of read operations. The cell
counter 350 may transmit the cell count nC to the control logic and
voltage generator 330.
[0087] The input/output circuit 360 may provide data DATA provided
from the outside to the page buffer 340. In a read operation of the
nonvolatile memory device 300, the input/output circuit 360 may
receive data DATA from the page buffer 340. The input/output
circuit 360 may transmit the received data to the memory controller
110 or 210.
[0088] FIG. 6 is a circuit diagram describing a memory block
included in a nonvolatile memory device of FIG. 5. A memory block
BLKn having a three-dimensional (3D) structure will be described
with reference to FIG. 6. However, inventive concepts are not
limited thereto, and the remaining memory blocks BLK1 to BLKn-1 may
have the same or similar structures as that of the memory block
BLKn. Referring to FIG. 6, the memory block BLKn includes a
plurality of cell strings CS11, CS12, CS21, and CS22. The cell
strings CS11, CS12, CS21, and CS22 may be arranged along a row
direction and a column direction to form rows and columns.
[0089] Each of the cell strings CS11, CS12, CS21, and CS22 may
include a plurality of cell transistors. For example, each of the
cell strings CS11, CS12, CS21, and CS22 may include string
selection transistor SSTa and SSTb, a plurality of memory cells MC1
to MC8, ground selection transistors GSTa and GSTb, and dummy
memory cell DMC1 and DMC2. In an example embodiment, each of the
memory cells MC1 to MC8 included in the cell strings CS11, CS12,
CS21, and CS22 may be a charge trap flash (CTF) memory cell.
[0090] In each cell string, the memory cells MC1 to MC8 may be
serially connected to each other and may be stacked in a height
direction that is a direction perpendicular to a plane defined by
the row direction and the column direction. In each cell string,
the string selection transistors SSTa and SSTb may be serially
connected to each other and may be arranged between the memory
cells MC1 to MC8 and a bit line BL. In each cell string, the ground
selection transistors GSTa and GSTb may be serially connected to
each other and may be arranged between the memory cells MC1 to MC8
and a common source line CSL.
[0091] In an example embodiment, in each cell string, a first dummy
memory cell DMC1 may be arranged between the memory cells MC1 to
MC8 and the ground selection transistors GSTa and GSTb. In an
example embodiment, in each cell string, a second dummy memory cell
DMC2 may be arranged between the memory cells MC1 to MC8 and the
string selection transistors SSTa and SSTb.
[0092] The ground selection transistors GSTa and GSTb of the cell
strings CS11, CS12, CS21, and CS22 may be connected in common to a
ground selection line GSL. In an example embodiment, ground
selection transistors in the same row may be connected to the same
ground selection line, and ground selection transistors in
different rows may be connected to different ground selection
lines. For example, the first ground selection transistors GSTa of
the cell strings CS11 and CS12 in the first row may be connected to
a first ground selection line, and the first ground selection
transistors GSTa of the cell strings CS21 and CS22 in the second
row may be connected to a second ground selection line.
[0093] In an example embodiment, although not illustrated in FIG.
6, ground selection transistors at the same height from a substrate
(not illustrated) may be connected to the same ground selection
line, and ground selection transistors at different heights may be
connected to different ground selection lines. For example, the
first ground selection transistors GSTa of the cell strings CS11,
CS12, CS21, and CS22 may be connected to the first ground selection
line, and the second ground selection transistors GSTb thereof may
be connected to the second ground selection line.
[0094] Memory cells of the same height from the substrate or the
ground selection transistors GSTa and GSTb may be connected in
common to the same word line, and memory cells of different heights
therefrom may be connected to different word lines. For example,
the first to eighth memory cells MC1 to MC8 in the cell strings
CS11, CS12, CS21, and CS22 may be connected in common to first to
eighth word lines WL1 to WL8, respectively.
[0095] First string selection transistors belonging to the same
row, from among the first string selection transistors SSTa at the
same height may be connected to the same string selection line, and
first string selection transistors belonging to different rows may
be connected to different string selection lines. For example, the
first string selection transistors SSTa of the cell strings CS11
and CS12 in the first row may be connected in common to a string
selection line SSL1a, and the first string selection transistors
SSTa of the cell strings CS21 and CS22 in the second row may be
connected in common to a string selection line SSL2a.
[0096] Likewise, second string selection transistors belonging to
the same row, from among the second string selection transistors
SSTb at the same height may be connected to the same string
selection line, and second string selection transistors in
different rows may be connected to different string selection
lines. For example, the second string selection transistors SSTb of
the cell strings CS11 and CS12 in the first row may be connected in
common to a string selection line SSL1b, and the second string
selection transistors SSTb of the cell strings CS21 and CS22 in the
second row may be connected in common to a string selection line
SSL2b.
[0097] Although not shown in FIG. 6, string selection transistors
of cell strings in the same row may be connected in common to the
same string selection line. For example, the first and second
string selection transistors SSTa and SSTb of the cell strings CS11
and CS12 in the first row may be connected in common to the same
string selection line. The first and second string selection
transistors SSTa and SSTb of the cell strings CS21 and CS22 in the
second row may be connected in common to the same string selection
line.
[0098] In an example embodiment, dummy memory cells at the same
height may be connected with the same dummy word line, and dummy
memory cells at different heights may be connected with different
dummy word lines. For example, the first dummy memory cells DMC1
may be connected with the first dummy word line DWL1, and the
second dummy memory cells DMC2 may be connected with the second
dummy word line DWL2.
[0099] In an example embodiment, the memory block BLKz illustrated
in FIG. 6 is only example. The number of cell strings may increase
or decrease, and the number of rows of cell strings and the number
of columns of cell strings may increase or decrease according to
the number of cell strings. Also, in the memory block BLKz, the
number of cell transistors (GST, MC, DMC, SST, etc.) may increase
or decrease. Also, a height of the memory block BLKn may increase
or decrease according to the number of cell transistors.
Furthermore, the number of lines (GSL, WL, DWL, SSL, etc.)
connected with cell transistors may increase or decrease according
to the number of cell transistors.
[0100] The following patent documents, which are hereby
incorporated by reference, describe suitable configurations for 3D
memory arrays, in which the three-dimensional memory array is
configured as a plurality of levels, with word lines and/or bit
lines shared between levels: U.S. Pat. Nos. 7,679,133; 8,553,466;
8,654,587; 8,559,235; and US Pat. Pub. No. 2011/0233648, the entire
disclosures of each of which are herein incorporated by
reference.
[0101] FIG. 7 is a distribution diagram describing an initial
program threshold voltage distribution of memory cells and a
changed threshold voltage distribution of the memory cells as time
goes by. Referring to FIG. 7, a method of reading a triple level
cell (TLC) capable of storing 3-bit data on a per-page basis is
disclosed; however, inventive concepts are not limited thereto.
[0102] A change of a threshold voltage distribution of memory cells
may be different depending on a programmed state. For example, in
the case of an erase state E or a low-order program state (e.g.,
P1), the threshold voltage distribution tends to be shifted in a
direction where threshold voltages increase. In the case of
high-order program states (e.g., P6, and P7), the threshold voltage
distribution tends to be shifted in a direction where threshold
voltages decrease. In the case of intermediate-order program states
(e.g., P2, P3, P4, and P5), there may be little or no shift in the
threshold voltage distribution.
[0103] Referring to FIGS. 1, 2 and 7 together, the nonvolatile
memory device 120, 220, and 300 may determine a program state of
memory cells programmed using first through seventh read voltages
RD1 to RD7. The first through seventh read voltages RD1 to RD7 may
be generated by the control logic and voltage generator 330. Each
of the first through seventh read voltages RD1 to RD7) may have a
desired (or, alternatively, predetermined) voltage level to
determine a program state of the programmed memory cells.
[0104] To read the least significant bit (LSB) page, the second and
fifth read voltages RD2 and RD5 may be sequentially applied. The
second read voltage RD2 may be used to distinguish between a state
having a threshold voltage lower than a first program state P1 and
a state having a threshold voltage higher than a second program
state P2. The fifth read voltage RD5 may be used to distinguish
between a state having a threshold voltage lower than a fourth
program state P4 and a state having a threshold voltage higher than
a fifth program state P5.
[0105] To read the center significant bit (CSB) page, the first,
third and sixth read voltages RD1, RD3, and RD6 may be sequentially
applied. The first read voltage RD1 may be used to distinguish
between a state having a threshold voltage lower than the erase
state E and a state having a threshold voltage higher than the
first program state P1. The third read voltage RD3 may be used to
distinguish between a state having a threshold voltage lower than
the second program state P2 and a state having a threshold voltage
higher than a third program state P3. The sixth read voltage RD6
may be used to distinguish between a state having a threshold
voltage lower than the fifth program state P5 and a state having a
threshold voltage higher than a sixth program state P6.
[0106] To read the most significant bit (MSB) page, the fourth and
seventh read voltages RD4, and RD7 may be sequentially applied. The
fourth read voltage RD4 may be used to distinguish between a state
having a threshold voltage lower than the third program state P3
and a state having a threshold voltage higher than the fourth
program state P4. The seventh read voltage RD7 may be used to
distinguish between a state having a threshold voltage lower than
the sixth program state P6 and a state having a threshold voltage
higher than a seventh program state P7.
[0107] The first through seventh read voltages RD1 to RD7 of the
nonvolatile memory device 300 (120, and 220) may be determined
based on a stabilized threshold voltage distribution (e.g., a
threshold voltage distribution after a desired (or, alternatively,
predetermined) time goes by). However, as illustrated in FIG. 7,
the threshold voltage distribution of the program states E to P7
may be shifted as time goes by. The program states E to P7 may also
be shifted by a program disturbance, a read disturbance, and/or a
coupling phenomenon. In the case of reading the programmed memory
cells using the read voltages RD1 to RD7, the nonvolatile memory
device 300 may read data DATA including an error. To prevent, or
reduce the likelihood of, data including an error from being read,
the nonvolatile memory device 300 may perform a cell count at a
specific time. The nonvolatile memory device 300 may adjust at
least one level of the read voltages to at least one level not used
in the read operation.
[0108] FIG. 8 is a view describing a RVL LUT according to example
embodiments of inventive concepts. Referring to FIGS. 1, 2 and 8,
the memory controller 110, and 210 may include the RVL LUT 111
(211). The RVL LUT 111 (211) includes mapping information on read
voltage level changes according to the reference cell count.
[0109] The RVL LUT 111 (211) is a table for adjusting a read
voltage on pages including a triple-level cell (TLC). This is an
example for describing inventive concepts. Information included in
the RVL LUT 111 (211) may become different depending on a storable
bit of a page of the nonvolatile memory device 120, 220. The RVL
LUT 111 may include a plurality of tables 111_1(211_1) to
111_7(211_7). The plurality of tables 111_1(211_1) to 111_7(211_7)
map a plurality of read voltage level changes on the read voltages
RD1 to RD7 respectively. The read voltages RD1 to RD7 may be
voltages determined based on the threshold voltage distribution
(e.g., stabilized threshold voltage distribution) before being
shifted.
[0110] Referring to the first RVL LUT 111_1(211_1), the first read
voltage RD1 is a reference cell count and has a first reference
cell count C1. When a cell count comparison operation on the first
read voltage RD1 is performed, the first RVL LUT 111_1(211_1) may
include mapping information of the read voltages RD2 to RD7 and a
plurality of read voltage level changes .DELTA.RD2_1 to
.DELTA.RD7_1. At least one of the second through seventh read
voltages RD2 to RD7 may be changed as much as a corresponding read
voltage level changes among the plurality of read voltage level
changes .DELTA.RD2_1 to .DELTA.RD7_1.
[0111] Referring to FIGS. 7 and 8, the second and third read
voltage level changes .DELTA.RD2_1, and .DELTA.RD3_1 according to
the first read voltage RD1 may be a positive value. This is
because, in the case of the low-order program states P1, and P2,
the threshold voltage distribution tends to be shifted in a
direction where threshold voltages increase. To perform a more
accurate read operation, the second and third read voltage levels
RD2, and RD3 may increase. The fourth through seventh read voltage
level changes .DELTA.RD4_1 to .DELTA.RD7_1 according to the first
read voltage RD1 may be a negative value. This is because, in the
case of the center program states P3 to P5 and the high-order
states P6, and P7, the threshold voltage distribution tends to be
shifted in a direction where threshold voltages decrease. To
perform a more accurate read operation, the fourth through seventh
read voltage levels RD4 to RD7 may increase. This is merely an
example of inventive concepts and the plurality of read voltage
level changes .DELTA.RD2_1 to .DELTA.RD7_1 according to the first
read voltage RD1 may become different depending on a tendency where
the threshold voltage distribution is shifted.
[0112] Referring to the second RVL LUT 111_2(211_2), the second
read voltage RD2 is a reference cell count and has a second
reference cell count C2. When a cell count comparison operation on
the second read voltage RD2 is performed, the second RVL LUT
111_2(211_2)) may include mapping information of the read voltages
RD1, and RD3 to RD7 and a plurality of read voltage level changes
.DELTA.RD1_2, and .DELTA.RD3_2 to .DELTA.RD7_2. At least one of the
first and third through seventh read voltages RD1, and RD3 to RD7
may be changed as much as a corresponding read voltage level
changes among the plurality of read voltage level changes
.DELTA.RD1_2, and .DELTA.RD3_2 to .DELTA.RD7_2.
[0113] Referring to FIGS. 7 and 8, the first and third read voltage
level changes .DELTA.RD1_2, and .DELTA.RD3_2 according to the
second read voltage RD2 may be a positive value. The fourth through
seventh read voltage level changes .DELTA.RD4_2 to .DELTA.RD7_2
according to the second read voltage RD2 may be a negative value.
This is merely an example of inventive concepts and the plurality
of read voltage level changes (.DELTA.RD1_2, .DELTA.RD3_2, and
.DELTA.RD4_2 to .DELTA.RD7_2) according to the second read voltage
RD2 may become different depending on a tendency where the
threshold voltage distribution is shifted.
[0114] Referring to the third RVL LUT 111_3(211_3), the third read
voltage RD3 is a reference cell count and has a third reference
cell count C3. When a cell count comparison operation on the third
read voltage RD3 is performed, the third RVL LUT 111_3(211_3) may
include mapping information of the read voltages RD1, RD2, and RD4
to RD7 and a plurality of read voltage level changes .DELTA.RD1_3,
.DELTA.RD2_3, and .DELTA.RD4_3 to .DELTA.RD7_3. At least one of the
first, second, fourth through seventh read voltages RD1, RD2, and
RD4 to RD7 may be changed as much as a corresponding read voltage
level changes among the plurality of read voltage level changes
.DELTA.RD1_3, .DELTA.RD2_3, .DELTA.RD4_3 to .DELTA.RD7_3.
[0115] Referring to FIGS. 7 and 8, the first and second read
voltage level changes .DELTA.RD1_3, and .DELTA.RD2_3 according to
the third read voltage RD3 may be a positive value. The fourth
through seventh read voltage level changes .DELTA.RD4_3 to
.DELTA.RD7_3 according to the third read voltage RD3 may be a
negative value. This is merely an example of inventive concepts and
the plurality of read voltage level changes .DELTA.RD1_3,
.DELTA.RD2_3, and .DELTA.RD4_3 to .DELTA.RD7_3 according to the
third read voltage RD3 may become different depending on a tendency
where the threshold voltage distribution is shifted.
[0116] Referring to the fourth RVL LUT 111_4(211_4), the fourth
read voltage RD4 is a reference cell count and has a fourth
reference cell count C4. When a cell count comparison operation on
the fourth read voltage RD4 is performed, the fourth RVL LUT
111_4(211_4) may include mapping information of the read voltages
RD1 to RD3, and RD5 to RD7 and a plurality of read voltage level
changes .DELTA.RD1_4 to .DELTA.RD3_4, and .DELTA.RD5_4 to
.DELTA.RD7_4. At least one of the first through third and fifth
through seventh read voltages RD1 to RD3, and RD5 to RD7 may be
changed as much as a corresponding read voltage level changes among
the plurality of read voltage level changes .DELTA.RD1_4 to
.DELTA.RD3_4, and .DELTA.RD5_4 to .DELTA.RD7_4.
[0117] Referring to FIGS. 7 and 8, the first through third read
voltage level changes .DELTA.RD1_4 to .DELTA.RD3_4 according to the
fourth read voltage RD4 may be a positive value. The fifth through
seventh read voltage level changes .DELTA.RD5_4 to .DELTA.RD7_4
according to the fourth read voltage RD4 may be a negative value.
This is merely an example of inventive concepts and the plurality
of read voltage level changes .DELTA.RD1_4 to .DELTA.RD3_4, and
.DELTA.RD5_4 to .DELTA.RD7_4 according to the fourth read voltage
RD4 may become different depending on a tendency where the
threshold voltage distribution is shifted.
[0118] Referring to the fifth RVL LUT 111_5(211_5), the fifth read
voltage RD5 is a reference cell count and has a fifth reference
cell count C5. When a cell count comparison operation on the fifth
read voltage RD5 is performed, the fifth RVL LUT 111_5(211_5) may
include mapping information of the read voltages RD1 to RD4, RD6,
and RD7 and a plurality of read voltage level changes .DELTA.RD1_5
to .DELTA.RD4_5, .DELTA.RD6_5, and .DELTA.RD7_5. At least one of
the first through third and fifth through seventh read voltages RD1
to RD4, RD6, and RD7 may be changed as much as a corresponding read
voltage level changes among the plurality of read voltage level
changes .DELTA.RD1_5 to .DELTA.RD4_5, .DELTA.RD6_5, and
.DELTA.RD7_5.
[0119] Referring to FIGS. 7 and 8, the first through third read
voltage level changes .DELTA.RD1_5 to .DELTA.RD3_5 according to the
fifth read voltage RD5 may be a positive value. The fourth, sixth,
and seventh read voltage level changes .DELTA.RD5_4, .DELTA.RD6_5,
and .DELTA.RD7_5 according to the fifth read voltage RD5 may be a
negative value. This is merely an example of inventive concepts and
the plurality of read voltage level changes .DELTA.RD1_5 to
.DELTA.RD4_5, .DELTA.RD6_5, and .DELTA.RD7_5 according to the fifth
read voltage RD5 may become different depending on a tendency where
the threshold voltage distribution is shifted.
[0120] Referring to the sixth RVL LUT 111_6(211_6), the sixth read
voltage RD6 is a reference cell count and has a sixth reference
cell count C6. When a cell count comparison operation on the sixth
read voltage RD6 is performed, the sixth RVL LUT 111_6(211_6) may
include mapping information of the read voltages RD1 to RD5, and
RD7 and a plurality of read voltage level changes .DELTA.RD1_6 to
.DELTA.RD5_6, and .DELTA.RD7_6. At least one of the first through
fifth and seventh read voltages RD1 to RD5, and RD7 may be changed
as much as a corresponding read voltage level changes among the
plurality of read voltage level changes .DELTA.RD1_6 to
.DELTA.RD5_6, and .DELTA.RD7_6.
[0121] Referring to FIGS. 7 and 8, the first through third read
voltage level changes .DELTA.RD1_6 to .DELTA.RD3_6 according to the
sixth read voltage RD6 may be a positive value. The fourth, fifth,
and seventh read voltage level changes .DELTA.RD4_6, .DELTA.RD5_6,
and .DELTA.RD7_6 according to the sixth read voltage RD6 may be a
negative value. This is merely an example of inventive concepts and
the plurality of read voltage level changes .DELTA.RD1_6 to
.DELTA.RD5_6, and .DELTA.RD7_6 according to the sixth read voltage
RD6 may become different depending on a tendency where the
threshold voltage distribution is shifted.
[0122] Referring to the seventh RVL LUT (111_7(211_7)), the seventh
read voltage RD7 is a reference cell count and has a seventh
reference cell count C7. When a cell count comparison operation on
the seventh read voltage RD7 is performed, the seventh RVL LUT
111_7(211_7) may include mapping information of the read voltages
RD1 to RD6 and a plurality of read voltage level changes
.DELTA.RD1_7 to .DELTA.RD6_7. At least one of the first through
sixth read voltages RD1 to RD6 may be changed as much as a
corresponding read voltage level changes among the plurality of
read voltage level changes .DELTA.RD1_7 to .DELTA.RD6_7.
[0123] Referring to FIGS. 5 and 7, the first through third read
voltage level changes .DELTA.RD1_7 to .DELTA.RD3_7 according to the
seventh read voltage RD7 may be a positive value. The fourth
through sixth read voltage level changes .DELTA.RD4_7, to
.DELTA.RD6_7 according to the seventh read voltage RD7 may be a
negative value. This is merely an example of inventive concepts and
the plurality of read voltage level changes .DELTA.RD1_7 to
.DELTA.RD6_7 according to the seventh read voltage RD7 may become
different depending on a tendency where the threshold voltage
distribution is shifted.
[0124] Referring to FIGS. 7 and 8, each of the plurality of
reference cell counts C1 to C7 may be a value to minimize
occurrence probability of an error in a read operation. Each of the
plurality of reference cell counts C1 to C7 may also be a value to
minimize the sum of the number of errors and occurrence probability
of an error in a read operation. Information included in the RVL
LUT 111(211) is transmitted to the nonvolatile memory device 120,
and 220 together with the read command CMD_r.
[0125] FIG. 9 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to example embodiments of inventive concepts. Referring to FIG. 9,
a read sequence for applying a read voltage level adjustment
according to a cell count comparison operation among read
operations of pages of a triple level cell (TLC) is classified
according to page. A plurality of read operations may be performed
on each of the pages.
[0126] Referring to FIG. 9 together with FIG. 7, the second and
fifth read voltages RD2, and RD5 may be sequentially applied to the
memory cell array 310 to perform a read operation of a page of the
least significant bit (LSB). The first and third read voltages RD1,
and RD3 may be sequentially applied to the memory cell array 310 to
perform a read operation of a page of the center significant bit
(CSB). A cell count operation and a cell count comparison operation
may be performed before the sixth read voltage RD6 is applied.
[0127] The cell counter 350 may perform a cell count operation with
reference to the third read voltage RD3. The cell counter 350 may
transmit a cell count nC on the third read voltage RD3 to the cell
count comparison circuit 331. The cell count comparison circuit 331
may perform a cell count comparison operation at a desired (or,
alternatively, predetermined) moment. The cell count comparison
circuit 331 may also perform a cell count comparison operation in
response to the control signal CNTL of the controller 110, and
210.
[0128] After the third read voltage RD3 is applied, the cell count
comparison circuit 331 may perform a cell count comparison
operation. To perform the cell count comparison operation, the cell
count comparison circuit 331 may refer to the cell count nC
provided from the cell counter 350. The cell counter 350 may count
the number of on-cells or off-cells among memory cells having the
third program state P3 in response to the third read voltage
RD3.
[0129] To perform the cell count comparison operation, the cell
count comparison circuit 331 may refer to information of the RVL
LUT 111_3(211_3) on the third read voltage RD3. The cell count
comparison circuit 331 may refer to information of read voltage
level changes calculated from the RVL CAL 212. The cell count
comparison circuit 331 may compare the third reference cell count
C3 on the third read voltage RD3 with the cell count nC on the
third read voltage RD3.
[0130] When the cell count nC is an on-cell count, if the third
reference cell count C3 is greater than the cell count nC on the
third read voltage RD3 and a difference between the third reference
cell count C3 and the cell count nC on the third read voltage RD3
is greater than a reference value, the cell count comparison
circuit 331 may output a signal that controls the read voltage
level selector 332. When the cell count nC is an off-cell count, if
the third reference cell count C3 is greater than the cell count nC
on the third read voltage RD3 and a difference between the third
reference cell count C3 and the cell count nC on the third read
voltage RD3 is less than the reference value, the cell count
comparison circuit 331 may output a signal that controls the read
voltage level selector 332. In this way, the cell count comparison
circuit 331 may output a signal that controls the read voltage
level selector 332 according to a comparison result of the cell
count nC on the third read voltage RD3 and the third reference cell
count C3.
[0131] The read voltage level selector 332 may output a new sixth
read voltage (RD6'=RD6+.DELTA.RD6_3) obtained by adding the sixth
read voltage level changes .DELTA.RD6_3 to the sixth read voltage
RD6. The new sixth read voltage RD6' may be used as a read voltage
on data stored in memory cell of the memory cell array 310. In a
read operation of a center significant bit (CSB) page, the new
sixth read voltage RD6' may be applied to the memory cell array 310
instead of the sixth read voltage RD6. To perform a read operation
of a most significant bit (MSB) page, the fourth and seventh read
voltages RD4, and RD7 may be sequentially applied to the memory
cell array 310.
[0132] FIG. 10 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 9. Referring
to FIGS. 1, 2, 5 and 10, in S110, the nonvolatile memory device
300(120, and 220) may receive the read command CMD_r from the
memory controller 110, and 210. The read command CMD_r may include
information of the RVL LUT 111(211). The read command CMD_r may
include information of read voltage level changes calculated from
the RVL CAL 212. In operation S120, the nonvolatile memory device
300(120, and 220) may perform a read operation in response to the
read command CMD_r.
[0133] In operation S130, the nonvolatile memory device 300(120,
and 220) may perform a cell count operation and a cell count
comparison operation. The nonvolatile memory device 300(120, and
220) may perform a cell count operation and a cell count comparison
operation on a read voltage among a plurality of read voltages.
[0134] In operation S140, the nonvolatile memory device 300(120,
and 220) may adjust at least one level of the read voltages not
used in the read operation with reference to the RVL LUT 111(211)
and the cell count nC. The nonvolatile memory device 300(120, and
220) may adjust at least one level of the read voltages not used in
the read operation with reference to information of read voltage
level changes calculated from the RVL CAL 212 and the cell count
nC. When a cell count on a read voltage among the plurality of read
voltages goes beyond the specified range, the nonvolatile memory
device 300(120, and 220) may adjust at least one level of the read
voltages not used in the read operation.
[0135] FIG. 11 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to example embodiments of inventive concepts. Referring to FIGS. 1,
2, 5 and 11, to perform a read operation of a page of the least
significant bit (LSB), the second read voltage RD2 may be applied
to the memory cell array 310. A cell count operation and a cell
count comparison operation may be performed before the fifth read
voltage RD5 is applied. The cell counter 350 may perform a cell
count operation on the second read voltage RD2. The cell counter
350 may transmit a cell count nC on the second read voltage RD2 to
the cell count comparison circuit 331. The cell counter 350 may
perform an on-cell count operation or an off-cell count operation
on the second read voltage RD2.
[0136] To perform a cell count comparison operation, the cell count
comparison circuit 331 may refer to information of the RVL LUT
111_2(211_2) on the second read voltage RD2. The cell count
comparison circuit 331 may compare the second reference cell count
C2 on the second read voltage RD2 with the cell count nC on the
second read voltage RD2.
[0137] According to a comparison result, the cell count comparison
circuit 331 may output a signal that controls the read voltage
level selector 332. According to a control signal, the read voltage
level selector 332 may output a new fifth read voltage
(RD5'=RD5+.DELTA.RD5_2) obtained by adding the fifth read voltage
level changes .DELTA.RD5_2 to the fifth read voltage RD5. In a read
operation of a page of the center significant bit (CSB) of FIG. 11,
a cell count operation and a cell count comparison operation may be
performed in concurrence with a read operation by the third read
voltage RD3. As the cell count operation and the cell count
comparison operation are performed in concurrence with the read
operation by the third read voltage RD3, total read operation time
may be reduced. To perform the cell count comparison operation, the
cell count comparison circuit 331 may refer to information of the
RVL LUT 111_1(211_1) on the first read voltage RD1.
[0138] The cell counter 350 may transmit a cell count nC on the
first read voltage RD1 to the cell count comparison circuit 331.
The cell count comparison circuit 331 may compare the first
reference cell count C1 on the first read voltage RD1 with the cell
count nC on the first read voltage RD1. A new sixth read voltage
RD6' may be applied to memory cells instead of the sixth read
voltage RD6 by the cell count comparison operation. The new sixth
read voltage RD6' is a value obtained by adding read voltage level
changes .DELTA.RD6_1 to the sixth read voltage RD6.
[0139] FIG. 12 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 11. Referring
to FIGS. 1, 2, 5, 11 and 12, in operation S210, the nonvolatile
memory device 300(120, and 220) may receive a read command CMD_r
from the memory controller 110, and 210. The read command CMD_r may
include information of the RVL LUT 111(211). The read command CMD_r
may include information of the read voltage level changes
calculated from the RVL CAL 212.
[0140] In operation S220, the nonvolatile memory device 300(120,
and 220) may perform a read operation in response to the read
command CMD_r. In operation S230, the nonvolatile memory device
300(120, and 220) may perform a cell count operation and a cell
count comparison operation during the read operation. In operation
S240, the nonvolatile memory device 300(120, and 220) may adjust
levels of the read voltages not used in the read operation with
reference to the RVL LUT 111(211) and a cell count nC. According to
a comparison result of the cell count, the nonvolatile memory
device 120 may reflect the read voltage level changes of the RVL
LUT 111 in the read voltage and may perform the read operation. The
nonvolatile memory device 300(120, and 220) may adjust levels of
the read voltages not used in the read operation with reference to
the information of the read voltage level changes calculated from
the RVL CAL 212 and the cell count nC.
[0141] FIG. 13 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to example embodiments of inventive concepts. Referring to FIGS. 1,
2, 5 and 13, the second read voltage RD2 may be applied to perform
a read operation of the least significant bit (LSB). After the
second read voltage RD2 is applied, a cell count operation and a
cell count comparison operation may be performed. As a result of
cell count comparison, when a cell count nC on the second read
voltage RD2 is within a specified range, the read voltage level
selector 332 may output the fifth read voltage RD5.
[0142] A process of a read operation of a page of the center
significant bit (CSB) of FIG. 13 may be the same as or similar to
that of FIG. 11. A cell count operation and a cell count comparison
operation on the first read voltage RD1 may be performed together
with a read operation on the third read voltage RD3. As a result of
cell count comparison, when a cell count nC on the first read
voltage RD1 is within a specified range, the read voltage level
selector 332 may output the sixth read voltage RD6.
[0143] The fourth read voltage RD4 may be applied to perform a read
operation of a page of the most significant bit (MSB). After the
fourth read voltage RD4 is applied, the cell count operation and
the cell count comparison operation may be performed. A level of
the seventh read voltage RD7 may be adjusted according to a result
of the cell count comparison operation. After a read operation of a
page of the center significant bit (CSB) is completed, the read
operation of the page of the most significant bit (MSB) is
performed.
[0144] The fourth read voltage RD4 may be applied to the memory
cell array 310 to perform the read operation of the page of the
most significant bit (MSB). A cell count operation and a cell count
comparison operation on the fourth read voltage RD4 may be
performed. A new seventh read voltage RD7' is applied to the memory
cell array 310 instead of the seventh read voltage RD7 according to
a comparison result. The new seventh read voltage RD7' is a value
obtained by adding read voltage level changes .DELTA.RD7_4 to the
seventh read voltage RD7.
[0145] FIG. 14 is a flowchart describing a cell count comparison
operation according to the sequence described in FIG. 13. Referring
to FIGS. 1, 2, 5, 13 and 14, in operation S310, the nonvolatile
memory device 300(120, and 220) may receive a read command CMD_r
from the memory controller 110, and 210. The read command CMD_r may
include information of the RVL LUT 111(211). The read command CMD_r
may include information of the read voltage level changes
calculated from the RVL CAL 212. In operation S320, the nonvolatile
memory device 300(120, and 220) may perform a first read operation
in response to the read command CMD_r.
[0146] In operation S330, the nonvolatile memory device 300(120,
and 220) may perform a cell count operation and a cell count
comparison operation. The nonvolatile memory device 300(120, and
220) may perform a cell count operation and a cell count comparison
operation on a read voltage applied to perform the first read
operation. In operation S340, the nonvolatile memory device
300(120, and 220) may perform a second read operation during the
cell count operation and the cell count comparison operation. The
nonvolatile memory device 300(120, and 220) may perform the second
read operation while performing the cell count operation and the
cell count comparison operation on the read voltage applied to
perform the first read operation.
[0147] In operation S350, the nonvolatile memory device 300(120,
and 220) may adjust at least one level of the read voltages not
used in the read operation with reference to the RVL LUT 111(211)
and the cell count nC. The nonvolatile memory device 300(120, and
220) may adjust at least one level of the read voltages not used in
the read operation with reference to information of read voltage
level changes calculated from the RVL CAL 212 and the cell count
nC. When a cell count on a read voltage applied to perform the
first read operation goes beyond the specified range, the
nonvolatile memory device 300(120, and 220) may adjust at least one
level of the read voltages not used in the read operation.
[0148] FIG. 15 is a table describing a characteristic of a cell
count comparison operation which is selectively applied according
to example embodiments of inventive concepts. Referring to FIGS. 11
and 15, processes of read operation by the third read voltage RD3
of a page of the center significant bit (CSB) may be the same as or
similar to each other. Levels of the sixth read voltage RD6 and the
seventh read voltage RD7 may be adjusted according to the cell
count comparison operation. After the third read voltage RD3 is
applied, a new sixth read voltage RD6' may be applied. The fourth
read voltage RD4 may be applied to perform a read operation of a
page of the most significant bit (MSB). A new seventh read voltage
RD7' is applied instead of the seventh read voltage RD7. Referring
to FIG. 15, a level of at least one read voltage may be adjusted
through the cell count comparison operation.
[0149] Referring to FIGS. 9, and 11 through 15, a cell count
operation and a cell count comparison operation may be performed at
least once in each page having a plurality of bits (LSB.about.MSB).
At least one of an on-cell count operation and an off-cell count
operation may be performed depending on a program state of memory
cells. The on-cell count operation may be performed on memory cell
programmed to the low-order program states P1, and P2. The off-cell
count operation may be performed on memory cell programmed to the
high-order program states P6, and P7. The on-cell count operation
or the off-cell count operation may be performed on all the read
voltages RD1 to RD7. The on-cell count operation or the off-cell
count operation may also be performed on some of the read voltages
RD1 to RD7.
[0150] The cell count comparison operation may be performed not
only in a read operation by the third read voltage RD3, but also in
read operations by the other read voltages RD1, RD2, and RD4 to
RD7.
[0151] Levels of the read voltages RD1 to RD7 may be adjusted
through the cell count comparison operation. For example, levels of
high-order read voltages (e.g., RD6, and RD7) where a threshold
voltage distribution is greatly shifted may be adjusted.
[0152] As described above, the levels of the read voltages are
adjusted and thereby a read error of the nonvolatile memory device
120 may be reduced. The read error may be reduced and thereby data
reliability of the nonvolatile memory device 120 may be
improved.
[0153] FIG. 16 is a distribution diagram illustrating a threshold
voltage distribution of memory cells according to example
embodiments of inventive concepts. For brief description, each of
memory cells of the nonvolatile memory device 120 may be assumed a
QLC (Quadruple Level Cell) storing 4-bit data. That is, memory
cells connected to one word line may store data regarding first
through fourth pages PG1 to PG4. However, the scope of inventive
concepts is not limited thereto.
[0154] Referring to FIGS. 1 and 16, each of the memory cells of the
nonvolatile memory device 120 may be programmed to have any one
state of an erase state E and first through fifteenth program
states P1 to P15. Similar to that described above, the nonvolatile
memory device 120 may read data stored in the memory cells by
determining states of the memory cells based on first through
fifteenth read voltages RD1 to RD15.
[0155] For example, the nonvolatile memory device 120 may read data
of the first page PG1 based on the sixth, twelfth and fourteenth
read voltages RD6, RD12 and RD14, read data of the second page PG2
based on the third, eighth, tenth and thirteenth read voltages RD3,
RD8, RD10 and RD13, read data of the third page PG3 based on the
first, fifth, seventh and eleventh read voltages RD1, RD5, RD7 and
RD11, and read data of the fourth page PG4 based on the second,
fourth, ninth and fifteenth read voltages RD2, RD4, RD9 and
RD15.
[0156] The first through fourth pages PG1 to PG4 may be a LSB page,
a first CSB page, a second CSB page, and a MSB page respectively.
The first through fourth pages PG1 to PG4 may indicate logical page
data programmed in the memory cells connected to one word line.
However, the scope of inventive concepts is not limited thereto but
read voltages with respect to each page may be variously changed
according to a bit ordering.
[0157] FIG. 17 is a flow chart describing a read operation of a
nonvolatile memory device according to some example embodiments of
inventive concepts. Referring to FIGS. 1, 16 and 17, in operation
S410, the nonvolatile memory device 120 may receive a read
command.
[0158] In operation S420, the nonvolatile memory device 120 may
perform the cell count operation based on the most significant read
voltage (e.g., the fifteenth read voltage RD15) or a read voltage
corresponding to the most significant program state (e.g., the
fifteenth program state P15). Since the cell count operation was
described above, a description thereof is omitted.
[0159] In operation S430, the nonvolatile memory device 120 may
adjust levels of the read voltages based on a result of the cell
count operation. In operation S440, the nonvolatile memory device
120 may perform a read operation based on the adjusted read
voltages.
[0160] The embodiments described above perform the cell count
operation based on a specific read level being performed during the
read operation and adjust or correct levels of the read voltages to
be used later based on the result of the cell count operation.
However, according to the example embodiment of FIG. 17, the cell
count may be performed based on a specific level (e.g., a read
level corresponding to the most significant program state) and a
read voltage of the overall read levels may be adjusted based on a
cell count result.
[0161] For brevity of description, the read operation performed
based on the adjusted read voltage is referred to as a
single-sensing read operation. Performing `the single-sensing read
operation indicates an operation of reading a state of memory cells
based on the read voltage adjusted according to various
operations.
[0162] FIGS. 18A and 18B are views for explaining an operation
method according to FIG. 17. For brevity of description,
constituent elements that are not necessary or used when explaining
the operation method of FIG. 17 are omitted. A detailed description
of the operation method or the constituent elements described above
is omitted.
[0163] Referring to FIGS. 1, 16 and 18A, the nonvolatile memory
device 120 may sequentially perform a read operation for the first
through fourth pages PG1 to PG4 in response to a read command CMD_r
from the memory controller 110. An order of the read operation for
each page or an order of the read voltages in the read operation
for each page is merely an example and the scope of inventive
concepts is not limited thereto.
[0164] The nonvolatile memory device 120 may perform the cell count
operation based on the fifteenth read voltage RD15 (i.e., read
voltage corresponding to the most significant program state P15)
before performing the read operation for the first page PG1 in
response to the read command CMD_r. The nonvolatile memory device
120 may adjust the first through fifteenth read voltages RD1 to
RD15 based on information of an RVL LUT 111 received from the
memory controller 110 and the cell count result. For example,
similar to that described with reference to FIG. 7, the RVL LUT 111
may include a reference cell count C15 with respect to the
fifteenth read voltage RD15 and an offset value of each of the
first through fifteenth read voltages RD1 to RD15 according to the
reference cell count C15. The nonvolatile memory device 120 may
determine an offset of each of the first through fifteenth read
voltages RD1 to RD15 based on the information of the RVL LUT 111,
and the cell count result and may adjust a level of each of the
first through fifteenth read voltages RD1 to RD15 based on the
determined offset.
[0165] The nonvolatile memory device 120 may sequentially perform
the single-sensing read operation for the first through fourth
pages PG1 to PG4 based on the adjusted first through fifteenth read
voltages RD1' to RD15'.
[0166] Referring to FIGS. 1, 16 and 18B, similar to FIG. 18A, the
nonvolatile memory device 120 may perform the cell count operation
based on the fifteenth read voltage RD15 before performing the read
operation for the first page PG1 in response to the read command
CMD_r. In this case, the nonvolatile memory device 120 may detect a
state of the memory cells based on the fifteenth read voltage RD15
before the read operation for the first page PG1 is performed and
may perform the cell count operation while performing read
operation for the first page PG1. In further detail, the
nonvolatile memory device 120 may determine a state of the memory
cells based on the sixth read voltage RD6 and at the same time, may
calculate the number of on-cells or off-cells based on a state of
the memory cells determined before (e.g., the state of the memory
cells determined based on the fifteenth read voltage RD15). The
nonvolatile memory device 120 may adjust levels of the remaining
read voltages (RD1 to RD5, RD8 to RD15) based on the cell count
result.
[0167] Referring to FIGS. 17 through 18B, the cell count operation
for the read voltage (i.e., fifteenth read voltage RD15)
corresponding to the most significant program state (i.e.,
fifteenth program state P15) was described but the scope of
inventive concepts is not limited thereto. The cell count operation
may be performed based on the read voltage (i.e., first read
voltage RD1) corresponding to an erase state E or a read voltage
corresponding to other program state. The cell count result may
indicate the number of off-cells or the number of on-cells.
[0168] As described above, the nonvolatile memory device 120
according to example embodiments of inventive concepts may perform
the cell count operation based on a specific read voltage and may
adjust levels of all or part of the read voltages based on the cell
count operation before performing an actual read operation for each
page in response to the read command CMD_r.
[0169] FIG. 19 is a flow chart describing a read operation of a
nonvolatile memory device according to inventive concepts.
Referring to FIGS. 1 and 19, the nonvolatile memory device 120 may
perform operations of operations S510 and S520. Since the
operations of steps S510 and S520 are similar to the operations of
the steps S410 and S420, a description thereof is omitted.
[0170] In operation S530, the nonvolatile memory device 120 may
adjust read voltage levels corresponding to an i-th page (the i is
simply a variable for explaining a repetitive operation). For
example, when the nonvolatile memory device 120 reads the first
page PG1, as illustrated in FIG. 16, the nonvolatile memory device
120 may adjust levels of the sixth, twelfth and fourteenth read
voltages RD6, RD12 and RD14 corresponding to the first page
PG1.
[0171] In operation S540, the nonvolatile memory device 120 may
perform a single-sensing read operation for the i-th page using the
adjusted read voltages. For example, the nonvolatile memory device
120 may perform a single-sensing read operation for the first page
using the adjusted sixth, twelfth and fourteenth read voltages
RD6', RD12' and RD14'.
[0172] In operation S550, the nonvolatile memory device 120 may
determine whether i is the maximum value. That is, the nonvolatile
memory device 120 may determine whether a read operation for all
the pages connected to one word line is completed.
[0173] When a variable i does not have the maximum value, in
operation S560, a value of the variable i increases by 1 and the
nonvolatile memory device 120 may perform operations of the steps
S520 to S540. When a read operation for each page is performed, the
nonvolatile memory device 120 may perform a cell count based on a
specific level (e.g., a read voltage corresponding to the most
significant program state), and may perform a single-sensing
operation for each page by adjusting read voltages corresponding to
each page based on a result of the cell count.
[0174] FIG. 20 is view for explaining an operation method of FIG.
19. For brevity of description, constituent elements that are not
necessary or used when explaining the operation method of FIG. 19
are omitted. Referring to FIGS. 1, 16 and 20, the nonvolatile
memory device 120 may perform read operations for the first through
fourth pages PG1 to PG4 in response to the read command CMD_r. In
this case, the nonvolatile memory device 120 may perform the cell
count operation based on the fifteenth read voltage RD15 and may
adjust read voltages corresponding to each page based on a result
of the cell count operation before a read operation for each page
is performed.
[0175] For example, the nonvolatile memory device 120 may perform
the cell count operation based on the fifteenth read voltage RD15
before a read operation for the first page PG1 is performed. The
nonvolatile memory device 120 may adjust levels of the sixth,
twelfth and fourteenth read voltages RD6, RD12 and RD14
corresponding to the first page PG1 based on the cell count result.
After that, the nonvolatile memory device 120 may perform a
single-sensing read operation for the first page PG1 based on the
adjusted sixth, twelfth, and fourteenth read voltages RD6', RD12'
and RD14'.
[0176] Similarly, the nonvolatile memory device 120 may perform the
cell count operation based on the fifteenth read voltage RD15 and
may adjust voltages [RD3, RD8, RD10, RD13], [RD1, RD5, RD7, RD11],
[RD2, RD4, RD9, RD15] corresponding to the second through fourth
pages PG2 to PG4 respectively based on a result of the cell count
operation before read operations for the second through fourth
pages PG2 to PG4 are performed. The nonvolatile memory device 120
may perform a single-sensing read operation for the second through
fourth pages PG2 to PG4 based on the adjusted voltages [RD3', RD8',
RD10', RD13'], [RD1', RD5', RD7', RD11'], [RD2', RD4', RD9',
RD15'].
[0177] The cell count operation for each page may be performed
based on the first read voltage RD1 corresponding to the erase
state E or a read voltage corresponding to other program state.
However, the scope of inventive concepts is not limited
thereto.
[0178] According to embodiments of FIGS. 19 and 20, unlike the
embodiments of FIGS. 17 through 18B, a cell count operation for
adjusting read voltages corresponding to each page may be performed
before the read operation for each page is performed. Although not
illustrated in the drawing, the cell count-based read voltage
adjusting operation described above may be performed only on some
pages. For example, to adjust read voltages corresponding to the
first and second pages PG1 and PG2, a cell count operation is
performed once and then to adjust read voltages corresponding to
the third and fourth pages PG3 and PG4, a cell count operation is
performed once.
[0179] FIG. 21 is a block diagram illustrating a nonvolatile memory
device according to example embodiments of inventive concepts.
Referring to FIG. 21, a nonvolatile memory device 1200 may include
a memory cell array 1210, an address decoder 1220, a control logic
and voltage generator 1230, a page buffer 1240, a cell counter
1250, and an input/output circuit 1260. Since the memory cell array
1210, the address decoder 1220, the control logic and voltage
generator 1230, the page buffer 1240, the cell counter 1250, and
the input/output circuit 1260 were described with reference to FIG.
5, a description thereof is omitted.
[0180] The control logic and voltage generator 1230 may include a
cell count comparison circuit 1231 and a data selector 1232. The
cell count comparison circuit 1231 may receive a cell count nC and
compare the received cell count nC. The cell count comparison
circuit 1231 may also compare the received cell count nC to
generate a plurality of counting information.
[0181] The data selector 1232 may select and output any one from
among a plurality of data stored in the page buffer 1240 based on
the plurality of counting information from the cell count
comparison circuit 1231.
[0182] For example, the nonvolatile memory device 1200 may perform
a read operation using at least two read voltages to determine one
program state. For example, the nonvolatile memory device 1200 may
determine states of memory cells based on the at least two read
voltages to divide the fourteenth and fifteenth program states P14
and P15. At least two read data may be generated by the at least
two read voltages.
[0183] The data selector 1232 may select any one from among at
least two data so that any one of the at least two data is output
through the input/output circuit 1260 based on the plurality of
counting information from the cell count comparison circuit 1231. A
method in which data is selected by the data selector 1232 will be
described in further detail with reference to FIG. 24.
[0184] For convenience of explanation, an operation is referred to
as `multi-sensing read operation` which reads states of memory
cells based on at least two voltages and selects one of at least
two data generated by a reading result to output the selected data
in order to divide adjacent two program states. That is, the
multi-sensing read operation may be similar to an on-chip valley
search operation.
[0185] FIG. 22 is a flow chart describing an operation of a
nonvolatile memory device of FIG. 21. Referring to FIGS. 21 and 22,
operations of steps S610 and S620 may be performed. Since the
operations of steps S610 and S620 are similar to the operations of
the steps S410 and S420, a detailed description thereof is
omitted.
[0186] In operation S630, the nonvolatile memory device 1200 may
adjust levels of some read voltages based on a cell count result.
For example, the nonvolatile memory device 1200 may adjust levels
of read voltages corresponding to low-order program states based on
the cell count result.
[0187] In operation S640, the nonvolatile memory device 1200 may
perform a single-sensing read operation and perform a multi-sensing
read operation based on the adjusted read voltages. For example,
the nonvolatile memory device 1200 may perform may perform a
single-sensing read operation with respect to low-order program
states and perform a multi-sensing read operation with respect to
high-order program states based on the adjusted read voltages.
[0188] In operation S650, the nonvolatile memory device 1200 may
select data corresponding to the multi-sensing read operation based
on the cell count result. For example, as described above, when the
multi-sensing read operation was performed, a plurality of data may
be generated. The nonvolatile memory device 1200 may select any one
from among the plurality of data generated by the multi-sensing
read operation, and the selected data may be output to the
outside.
[0189] FIG. 23 is a view for explaining an operation method of FIG.
22. For brevity of description, constituent elements that are not
necessary or used when explaining the operation method of FIG. 22
and a detailed description thereof are omitted.
[0190] Referring to FIGS. 21 through 23, the nonvolatile memory
device 1200 may perform a cell count operation based on the
fifteenth read voltage RD15 before performing a read operation for
the first through fourth pages PG1 to PG4 in response to the read
command CMD_r. The nonvolatile memory device 1200 may adjust read
voltages corresponding to the low-order program states based on the
cell count result. The low-order program states may indicate the
erase state E and the first through tenth program states P1 to P10
but the scope of inventive concepts is not limited thereto.
[0191] The nonvolatile memory device 1200 may perform the
corresponding single-sensing read operation based on the adjusted
read voltages. The multi-sensing read operation may be performed on
the remaining read voltages. For example, the nonvolatile memory
device 1200 may perform a read operation based on the adjusted
sixth read voltage RD6' in the read operation for the first page
PG1. After that, the nonvolatile memory device 1200 may perform the
multi-sensing read operation with respect to the twelfth and
fourteenth read voltages RD12 and RD14.
[0192] Similarly, the nonvolatile memory device 1200 may perform a
single-level read operation with respect to the second through
fourth pages PG2 to PG4 respectively based on the adjusted read
voltages. A multi-level read operation may be performed with
respect to non-adjusted read voltages.
[0193] After that, the nonvolatile memory device 1200 may select
any one from among a plurality of data generated by the multi-level
sensing operations based on the cell count result. The
multi-sensing read operation and the data selection operation are
described in further detail with reference to FIGS. 24A and
24B.
[0194] FIGS. 24A and 24B are views for explaining a multi-sensing
read operation. For brevity of description, the multi-sensing read
operation is described based on a read operation for a first CSB
page with reference to FIG. 24A.
[0195] Referring to FIGS. 21 and 24A, the nonvolatile memory device
1200 may perform a cell count operation based on the fifteenth read
voltage RD15. The nonvolatile memory device 1200 may adjust levels
of the third, eighth, and tenth read voltages RD3, RD8 and RD10
based on the cell count result. The nonvolatile memory device 1200
may perform a corresponding single-level read operation based on
the adjusted third, eighth, and tenth read voltages RD3', RD8' and
RD10'. The adjusted third, eighth, and tenth read voltages RD3',
RD8' and RD10' used in the single-level read operation may be any
one of values illustrated by a dotted line in FIG. 24A.
[0196] The nonvolatile memory device 1200 may perform a multi-level
read operation with respect to the thirteenth read voltage RD13. As
described above, the multi-level read operation indicates an
operation of reading states of memory cells based on at least two
voltages to determine adjacent two program states.
[0197] For example, as illustrated in FIG. 24B, the nonvolatile
memory device 1200 reads states of the memory cells based on a
plurality of read voltages RD13a to RD13e to determine the twelfth
and thirteenth program states P12 and P13 and thereby a plurality
of data may be generated. The plurality of data (i.e., states of
the memory cells) read by the plurality of read voltages RD13a to
RD13e may be different from each other. In this case, the
nonvolatile memory device 1200 may select any one form among the
plurality of data based on the cell count result.
[0198] As a further detailed example, when the cell count result
indicates that the number of off-cells is determined to be smaller
than a reference value, a distribution of threshold voltages of the
memory cells is in an overall lowered state. In this case, data
read by a relatively lower read voltage (e.g., RD13a) among the
plurality of read voltages RD13a to RD13e may be selected. However,
when the cell count result indicates that the number of off-cells
is determined to be greater than the reference value, a
distribution of threshold voltages of the memory cells is in an
overall heightened state (or in a relatively less lowered state).
In this case, data read by a relatively higher read voltage (e.g.,
RD13e) among the plurality of read voltages RD13a to RD13e may be
selected. As an illustration, according to the distribution diagram
illustrated in FIG. 24B, data read by the `RD13c` is selected.
[0199] A data selection by a multi-sensing read operation may be
done based on data generated by the multi-sensing read operation.
For example, the cell count comparison circuit 1231 of FIG. 21 may
generate the plurality of counting information based on data
generated by each of the plurality of read voltages RD13a to RD13e.
The plurality of counting information may correspond to the number
of cells Ca, the number of cells Cb, the number of cells Cc, and
the number of cells Cd respectively illustrated in FIG. 24B. The
number of cell Ca may indicate the number of memory cells having a
threshold voltage between the read voltages RD13a and RD13b, the
number of cell Cb may indicate the number of memory cells having a
threshold voltage between the read voltages RD13b and RD13c, the
number of cell Cc may indicate the number of memory cells having a
threshold voltage between the read voltages RD13c and RD13d, and
the number of cell Cd may indicate the number of memory cells
having a threshold voltage between the read voltages RD13d and
RD13e.
[0200] For example, by comparing sizes of the number of cells Ca,
the number of cells Cb, the number of cells Cc, and the number of
cells Cd with one another, an improved or optimum read voltage
(`RD13c` in FIG. 24B) may be determined and data (e.g., data read
by the improved read voltage) corresponding to the determined
optimum read voltage may be selected as data to be output.
[0201] As described above, the nonvolatile memory device 1200
according to inventive concepts may perform a cell count operation
based on a specific voltage before a read operation, and may adjust
a read voltage based on a cell count result or perform a
multi-sensing read operation. Thus, a nonvolatile memory device
having improved reliability may be provided.
[0202] FIG. 25 is a view for explaining a read operation of a
nonvolatile memory device of FIG. 21. For brevity of description,
constituent elements that are not necessary or overlapped and a
detailed description thereof are omitted.
[0203] Referring to FIGS. 21 and 25, the nonvolatile memory device
1200 may perform a cell count operation based on the fifteenth read
voltage RD15 before performing read operations with respect to the
first through fourth pages PG1 to PG4 in response to the read
command CMD_r respectively. The nonvolatile memory device 1200 may
adjust levels of some read voltages to perform a single-sensing
read operation and a multi-sensing read operation based on the cell
count operation. Since the adjustment of the read voltage, the
single-sensing read operation, and the multi-sensing read operation
were described before, a detailed description thereof is
omitted.
[0204] Unlike the embodiment of FIG. 23, the embodiment of FIG. 25
may perform a cell count operation before a read operation is
performed with respect to each page, and may adjust a level of a
read voltage based on a cell count result to perform single-sensing
read operation and a multi-sensing read operation.
[0205] FIG. 26 is a flow chart describing an operation of a
nonvolatile memory device of FIG. 21. Referring to FIGS. 21 and 26,
in operation S710, the nonvolatile memory device 1200 may receive a
read command. In operation S720, the nonvolatile memory device 1200
may perform a multi-sensing read operation with respect to the most
significant program state. For example, the nonvolatile memory
device 1200 may perform the multi-sensing read operation described
with reference to FIG. 24 based on voltages adjacent to the
fifteenth read voltage RD15.
[0206] In operation S730, the nonvolatile memory device 1200 may
adjust levels of the read voltage based on a result of the
multi-sensing read operation. For example, a specific read voltage
may be selected by the multi-sensing read operation and data
generated by the selected read voltage may be output as output
data. In this case, the selected read voltage may be an improved or
optimum read voltage. As an illustration, other read voltages may
be adjusted according to a difference between the improved read
voltage and the original read voltage (e.g., fifteenth read voltage
RD15).
[0207] Alternatively, other read voltages may be adjusted based on
a cell count result by the improved read voltage. As a result of
the multi-sensing read operation, a plurality of counting
information may be generated and other read voltages may be
adjusted based on the plurality of counting information.
[0208] In operation S740, the nonvolatile memory device 1200 may
perform a single-sensing read operation based on the adjusted read
voltages.
[0209] FIG. 27 is a view for explaining an operation method of FIG.
26. For brevity of description, constituent elements not necessary
for explaining an operation method of FIG. 26 are omitted.
[0210] Referring to FIGS. 21 and 27, the nonvolatile memory device
1200 may perform a read operation with respect to the first through
fourth pages PG1 to PG4 in response to the read command CMD_r. In
this case, the nonvolatile memory device 1200 may perform a
multi-sensing read operation based on the fifteenth read voltage
RD15 before performing the read operation with respect to the first
through fourth pages PG1 to PG4. The multi-sensing read operation
of the fifteenth read voltage RD15 is similar to the operation
described with reference to FIG. 24B and thus, a detailed
description thereof is omitted.
[0211] The nonvolatile memory device 1200 may adjust the first
through fourteenth read voltages RD1 to RD14 based on a result of
the multi-sensing read operation with respect to the fifteenth read
voltage RD15. For example, an improved or optimum level with
respect to the fifteenth read voltage RD15 may be selected based on
the multi-sensing read operation and the nonvolatile memory device
1200 may adjust the first through fourteenth read voltages RD1 to
RD14 based on the selected improved level. An improved or optimum
level with respect to the fifteenth read voltage RD15 may be
selected based on the multi-sensing read operation and the
nonvolatile memory device 1200 may adjust the first through
fourteenth read voltages RD1 to RD14 based on a cell count value
with respect to the selected improved level. A plurality of
counting values may be generated and the nonvolatile memory device
1200 may adjust the first through fourteenth read voltages RD1 to
RD14 based on the plurality of counting values. The method of
adjusting other read voltages based on the result of the
multi-sensing read operation is illustrative and the scope of
inventive concepts is not limited thereto.
[0212] The nonvolatile memory device 1200 may perform a
single-sensing read operation with respect to the first through
fourth pages PG1 to PG4 based on adjusted read voltages RD1' to
RD14'.
[0213] Since the multi-sensing read operation with respect to the
fifteenth read voltage RD15 was performed before an overall read
operation, the read operation with respect to the fifteenth read
voltage RD15 in the read operation with respect to the fourth page
PG4 may be omitted.
[0214] FIG. 28 is a view for explaining an operation of a
nonvolatile memory device of FIG. 21. For brevity of drawings and
convenience of description, overlapped constituent elements and a
description thereof are omitted.
[0215] Referring to FIGS. 21 and 28, the nonvolatile memory device
1200 may perform a read operation with respect to the first through
fourth pages PG1 to PG4 in response to the read command CMD_r. In
this case, the nonvolatile memory device 1200 may perform a cell
count operation based on the fifteenth read voltage RD15 and adjust
some corresponding read voltages according to a cell count result
before performing a read operation with respect to each of the
first through third pages PG1 to PG3. In the read operation with
respect to each of the first through third pages PG1 to PG3, the
nonvolatile memory device 1200 may perform a single-sensing read
operation based on the adjusted read voltage and perform a
multi-sensing read operation with respect to some read voltages.
The read operation with respect to the first through third pages
PG1 to PG3 is similar to the read method of FIG. 25 and thus, a
detailed description thereof is omitted.
[0216] In a read operation with respect to the fourth page PG, the
nonvolatile memory device 1200 may perform a multi-sensing read
operation with respect to the fifteenth read voltage RD15 and
adjust the remaining read voltages RD2, RD4 and RD9 based on a
result of the multi-sensing read operation. That is, in a specific
page, the nonvolatile memory device 1200 may perform a
multi-sensing read operation with respect to a specific read
voltage and adjust levels of other read voltages based on a result
of the multi-sensing read operation. In this case, in the read
operation with respect to the specific page, the read voltage may
be adjusted without an additional cell count operation.
[0217] The embodiments of inventive concepts described above are
examples for describing a technical spirit of inventive concepts
easily and the technical spirit of inventive concepts is not
limited thereto. For example, the nonvolatile memory device
according to inventive concepts may perform a read operation
according to a combination of the various embodiments described
above.
[0218] FIG. 29 is a flow chart describing an operation of a
nonvolatile memory device according to inventive concepts.
Referring to FIGS. 1 and 29, in operation S1110, the nonvolatile
memory device 120 may receive the read command CMD_r from the
memory controller 110. In operation S1120, the nonvolatile memory
device 120 may receive the address ADDR from the memory controller
110.
[0219] In operation S1130, the nonvolatile memory device 120 may
receive parameters for a cell count or a multi-sensing read
operation from the memory controller 110. For example, the
parameters may include information included in the RVL LUT 111 or a
reference counting value for performing a cell count described with
reference to FIG. 8, an offset value of each read voltage according
to the reference counting value, or information about a read
voltage set for performing the multi-sensing read operation. The
parameters may be provided to the nonvolatile memory device 120
through the same signal line as that used when the command CMD and
the address ADDR are provided to the nonvolatile memory device
120.
[0220] In operation s1140, the nonvolatile memory device 120 may
perform a read operation based on the parameters. For example, the
nonvolatile memory device 120 may perform the read operation
according to the embodiments described above based on the
parameters. In further detail, the nonvolatile memory device 120
may perform a cell count based on the received parameters and may
adjust read voltages based on a result of the cell count to perform
a single-sensing read operation or a multi-sensing read operation.
The nonvolatile memory device 120 may also perform a multi-sensing
read operation based on the received parameters and may adjust read
voltages based on a result of the multi-sensing read operation to
perform a single-sensing read operation.
[0221] FIG. 30 is a timing diagram illustrating a signal received
by a nonvolatile memory device according to an operation method of
FIG. 29. Referring to FIGS. 1 and 30, the nonvolatile memory device
120 may receive the read command CMD_r from the memory controller
110. After receiving the read command CMD_r, the nonvolatile memory
device 120 may receive the addresses ADDR from the memory
controller 110 during an address period. The addresses ADDR may
include row addresses and column addresses indicating a physical
location where data to be read is stored.
[0222] After receiving the addresses ADDR, the nonvolatile memory
device 120 may receive the cell count command CNT. The cell count
command CNT may indicate a command to perform a cell count
operation for adjusting read voltages as described above.
[0223] After receiving the cell count command CNT, in a reference
counting period (C_ref period), the nonvolatile memory device 120
may receive a plurality of reference counting information C1 to Cn.
The plurality of reference counting information C1 to Cn may
indicate a reference counting value used in the cell count
operation. That is, the plurality of reference counting information
C1 to Cn may be used as a reference value compared to a result of
the cell count operation.
[0224] After receiving the plurality of reference counting
information C1 to Cn, in an offset period, the nonvolatile memory
device 120 may receive plurality of offset information OF1 to OFm.
The plurality of offset information OF1 to OFm may indicate an
offset value of each read voltage with respect to the plurality of
reference counting information C1 to Cn. That is, a cell count
value is compared with the plurality of reference counting
information C1 to Cn, and one of the plurality of offset
information OF1 to OFm is selected based on a comparison result and
the selected offset information is reflected in a corresponding
read voltage. As a result, the corresponding read voltage may be
adjusted.
[0225] The nonvolatile memory device 120 may begin a read operation
at a first time t1. During the read operation, the nonvolatile
memory device 120 may receive the cell count command CNT, the
plurality of reference information C1 to Cn, and the plurality of
offset information OF1 to OFm, and may perform a cell count
operation based on the received information.
[0226] The nonvolatile memory device 120 may begin a read operation
at a second time t2. The nonvolatile memory device 120 may receive
the plurality of reference information C1 to Cn and the plurality
of offset information OF1 to OFm while performing the cell count
operation in response to the cell count command CNT. The
nonvolatile memory device 120 may adjust read voltages based on a
result of the cell count operation, the plurality of reference
information C1 to Cn, and the plurality of offset information OF1
to OFm and may perform a single-sensing read operation or a
multi-sensing read operation based on the adjusted read
voltages.
[0227] The nonvolatile memory device 120 may begin a read operation
at a third time t3. That is, nonvolatile memory device 120 may
receive the cell count command CNT, the plurality of reference
information C1 to Cn, and the plurality of offset information OF1
to OFm, may perform a cell counting operation in response to the
received information, may adjust the read voltages based on a
result of the cell count operation and the received information,
and may perform a single-sensing read operation or a multi-sensing
read operation based on the adjusted read voltages.
[0228] As described above, the nonvolatile memory device according
to inventive concepts receives information (e.g., information
required to perform the cell count operation or the multi-sensing
read operation) required or used to adjust read voltages from the
memory controller (or a separate external device) and may perform
various read operations according to the embodiments of inventive
concepts based on the received information.
[0229] FIG. 31 is a flow chart describing an operation of a memory
controller according to inventive concepts. Referring to FIGS. 1
and 31, the memory controller 110 may perform a read operation
based on a first read method. The first read method may be a
general read method of performing a read operation based on desired
(or, alternatively, predetermined) read voltages. The first read
method may be one of read methods according to the embodiments
described with reference to FIGS. 1 through 30.
[0230] In operation S1220, the memory controller 110 may detect and
correct errors read according to the first read method to determine
whether an uncorrectable error correction code (UECC) occurs. The
"UECC" may indicate a state including an error not corrected by an
ECC engine included in the memory controller 110.
[0231] When the UECC occurs, in operation S1230, the memory
controller 110 may perform a read method based on a second read
method. The second read method may be one of the read methods
according to the embodiments described with reference to FIGS. 1
through 30. The second read method may be a read method having
higher error correction ability than the first read method. For
example, when the first read method indicates a general read
operation, the second read method may indicate a read operation
according to a combination of the multi-sensing read operation and
the single-sensing read operation according to the embodiments of
inventive concepts. When the first read method is the read
operation according to a combination of the multi-sensing read
operation and the single-sensing read operation according to the
embodiments of inventive concepts, the second read method may
indicate a read operation which is a combination of the cell count
operation and the single-sensing read operation. For example, the
second read method may be one of read operations of various methods
having higher error correction ability than the first read
method.
[0232] In operation S1240, the memory controller 110 may detect and
correct an error read according to the second read method to
determine whether the UECC occurs.
[0233] When the UECC occurs, in operation S1250, the memory
controller 110 may determine whether all the read methods are
applied. For example, the memory controller 110 may be implemented
to support various read methods depending on an implementation
method. The memory controller 110 may determine whether executable
read methods are all applied.
[0234] When executable read methods remain, in operation S1260, the
memory controller 110 may perform a read operation based on an
improved read method. The improved read method may indicate a read
operation having higher error correction ability than the first and
second read method described before. The improved read method may
include any one of the read methods according to the embodiments
described with reference to FIGS. 1 through 30 or read operations
according to other read methods (e.g., soft decision, hard
decision, valley search, etc.). After that, the memory controller
110 may perform operation S1240.
[0235] The memory controller 110 may repeatedly perform operations
of the steps S1240 and S1250 until executable read methods are all
used.
[0236] In the case where executable read methods are all used but
errors are not corrected, in operation S1270, the memory controller
110 decides that the read methods fail and may transmit information
about a read failure to an external device (e.g., host).
[0237] In the case where errors are corrected in the step S1220,
S1230 or S1240 and thereby UECC does not occur, the memory
controller 110 may transmit the read data (i.e., data of which
errors are corrected) to an external device.
[0238] As described above, the memory controller according to
inventive concepts may use various read operations according to the
embodiments described with reference to FIGS. 1 through 31
according to whether an error occurs or not, or an error occurrence
step.
[0239] FIG. 32 is a block diagram illustrating a solid state drive
(SSD) system including a storage system according to example
embodiments of inventive concepts. Referring to FIG. 32, the SSD
system 2000 includes a host 2100 and a SSD 2200.
[0240] The SSD 2200 exchanges a signal with the host 2100 through a
signal connector 2201 and receives power PWR through a power
connector 2202. The SSD 2200 includes a SSD controller 2210, a
plurality of flash memories (2221 to 222n), an auxiliary power
supply 2230, and a buffer memory 2240.
[0241] The SSD controller 2210 can control the plurality of flash
memories (2221 to 222n) in response to a signal SIG received from
the host 2100. The plurality of flash memories (2221 to 222n) may
operate under the control of the SSD controller 2210. Each of the
plurality of flash memories (2221 to 222n) may be implemented by a
separate chip or a separate package. Each of the plurality of flash
memories (2221 to 222n) may operate based on the read operation
described with reference to FIGS. 1 through 30.
[0242] The auxiliary power supply 2230 is connected to the host
2100 through the power connector 2202. The auxiliary power supply
2230 may receive power PWR from the host 2100 to be charged. The
auxiliary power supply 2230 may provide power of the SSD 2200 when
a power supply from the host 2100 is not enough.
[0243] The contents described above are specific embodiments for
implementing inventive concepts. Inventive concepts may include not
only the embodiments described above but also embodiments in which
a design is simply or easily capable of being changed. Inventive
concepts may also include technologies easily changed to be
implemented using embodiments. Thus, the scope of inventive
concepts is to be determined by the following claims and their
equivalents, and shall not be restricted or limited by the
foregoing embodiments.
* * * * *