Memory and reading, writing and erasing methods thereof
A memory and reading, writing and erasing methods thereof. The memory includes: H memory planes arranged in parallel along a first direction, where each memory plane extends in a second direction, and includes M columns of memory strings; each column of memory string extends in a third direction; the first direction, the second direction and the third direction are all different, and H and M are integers greater than zero; each column of memory string includes N rows of memristive memory cells. The memory is also provided with word lines, gating transistors, gating lines, bit lines and a common source line, where memristive memory cells in last rows of all memory strings are connected to the common source line, and the common source line is connected to a reference potential through a reference resistor. Use performance of the memory can be improved.
1 . A memory, comprising:
H memory planes arranged in parallel along a first direction, wherein each memory plane extends in a second direction, and the memory plane comprises M columns of memory strings; the memory strings extend in a third direction; the first direction, the second direction and the third direction are different; and H and M are integers greater than zero;
wherein a single column of memory string comprises:
N rows of memristive memory cells connected in sequence, wherein N is an integer greater than zero;
N word lines, wherein a single word line is connected to corresponding rows of memristive memory cells; the word lines are used to receive word line voltages; and memristive memory cells in same rows receive a same word line voltage;
gating transistors, wherein sources of the gating transistors are connected to memristive memory cells in first rows;
gating lines, connected to gates of the gating transistors for receiving gating voltages, wherein all gating transistors on a memory plane receive a same gating voltage;
bit lines, connected to drains of the gating transistors for receiving bit line voltages, wherein gating transistors in same columns on different memory planes receive a same bit line voltage;
a common source line, wherein memristive memory cells in last rows of all memory strings are connected to the common source line, and the common source line is connected to a reference potential through a reference resistor.
2 . The memory according to claim 1 , wherein each memristive memory cell comprises a transistor and a memristor; a first end of the memristor is connected to a source of the transistor, and a second end of the memristor is connected to second ends of all memristors of a same memory string; the source of the transistor is connected to a drain of an adjacent transistor of the same memory string, and a source of a transistor in a last row of the memory string is connected to the common source line;
a word line is connected to a gate of the transistor.
3 . The memory according to claim 2 , wherein when a memristive memory cell to be read is located in a k-th row of a j-th memory string on an i-th memory plane, a voltage at a bit line corresponding to the j-th memory string is a bit line active voltage; voltages at other bit lines are bit line inactive voltages;
all gating transistors on the i-th memory plane is turned on, and other gating transistors are turned off;
when k=1, a transistor comprised in the memristive memory cell to be read is turned on, and no current exists in other transistors; the memristive memory cell to be read is connected to a gating transistor;
when k>1, during a first reading cycle, transistors comprised in memristive memory cells in a first row to a (k−1)-th row of the j-th memory string are all turned on first; and during a second reading cycle, transistors in the first row to the k-th row of the j-th memory string are turned on, and no current exists in other transistors;
wherein i, j and k are all integers greater than zero, and i≤H, j≤M, k≤N.
4 . The memory according to claim 2 , wherein when memristive memory cells to be read are located in a first row to an n-th row of a j-th memory string on an i-th memory plane, a voltage at a bit line corresponding to the j-th memory string is a bit line active voltage; voltages at other bit lines are bit line inactive voltages;
all gating transistors on the i-th memory plane are turned on, and other gating transistors are turned off;
transistors comprised in the memristive memory cells to be read are turned in sequence;
wherein i, j and n are all integers greater than zero, and i≤H, j≤M, 1<n≤N.
5 . The memory according to claim 2 , wherein when k>1, a target resistance value is to be written to a memristive memory cell to be written; and when the memristive memory cell to be written is located in a k-th row of a j-th memory string on an i-th memory plane, original resistance values corresponding to memristive memory cells in a first row to a (k−1)-th row of the j-th memory string on the i-th memory plane are read and saved; a level difference is determined according to the target resistance value; the level difference is set between the common source line and a bit line corresponding to the j-th memory string; each word line corresponding to the first row to the k-th row of the j-th memory string has a word line level, wherein the level difference and word line levels are used to turn on transistors comprised in the memristive memory cells in the first row to the k-th row;
except for the memristive memory cells in the first row to the k-th row, no current exists in other transistors;
all gating transistors on the i-th memory plane are turned on, and other gating transistors are turned off; at the same time as writing to the memristive memory cell to be written, the memristive memory cells in the first row to the (k−1)-th row of the j-th memory string on the i-th memory plane are also written to, wherein each memristive memory cell has the target resistance value of the k-th row after being written to; by taking the original resistance values corresponding to the memristive memory cells in the (k−1)-th row to the first row of the j-th memory string on the i-th memory plane as corresponding target resistance values, the memristive memory cells in the (k−1)-th row to the first row of the j-th memory string on the i-th memory plane are rewritten to in sequence;
wherein i, j and k are all integers greater than zero, and i≤H, j≤M, k≤N.
6 . The memory according to claim 2 , wherein when a memory string to be erased is a j-th memory string on an i-th memory plane, there is a level difference between the common source line and a bit line corresponding to the j-th memory string; each word line corresponding to the j-th memory string has a word line level, wherein the level difference and word line levels are used to turn on each of transistors of the j-th memory string;
all gating transistors on the i-th memory plane are turned on, and other gating transistors are turned off;
and, except for the j-th memory string on the i-th memory plane, no current exists in other transistors;
wherein i and j are all integers greater than zero, and i≤H, j≤M.
7 . A memory reading method, applied to the memory according to claim 1 , wherein when a memristive memory cell to be read is located in a k-th row of a j-th memory string on an i-th memory plane, the method comprises:
inputting a bit line active voltage at a bit line corresponding to the j-th memory string;
except for the j-th memory string and memory strings in same columns as the j-th memory string, inputting bit line inactive voltages at bit lines corresponding to other memory strings;
turning on all gating transistors on the i-th memory plane, and turning off other gating transistors;
before reading, making no current exist in transistors comprised in all memristive memory cells comprised in the memory;
after starting reading, when k=1, turning on a transistor comprised in the memristive memory cell to be read;
when k>1, during a first reading cycle, turning on transistors comprised in memristive memory cells in a first row to a (k−1)-th row of the j-th memory string on the i-th memory plane; and during a second reading cycle, turning on transistors comprised in memristive memory cells in the first row to the k-th row of the j-th memory string on the i-th memory plane;
wherein i, j and k are all integers greater than zero, and i≤H, j≤M and k≤N.
8 . The memory reading method according to claim 7 , wherein when k=1, a resistance value of a memristor included in the memristive memory cell to be read is determined according to a formula
R
1
=
V
bl
_
read
_
active
-
V
1
V
1
-
V
ref
R
ref
,
wherein R 1 represents the resistance value of the memristor comprised in the memristive memory cell to be read, V bl_read_active is the bit line active voltage at the bit line corresponding to the j-th memory string, V1 is a voltage at the common source line when reading from the memristive memory cell to be read, Rref is a resistance value of the reference resistor, and Vref represents a potential difference between the reference potential and ground;
when k>1, the resistance value of the memristor comprised in the memristive memory cell to be read is determined according to a formula
R
k
=
(
V
bl
_
read
_
active
-
V
k
)
(
V
bl
_
read
_
active
-
V
k
-
1
)
(
V
bl
_
read
_
active
-
V
ref
)
(
V
k
-
V
k
-
1
)
R
ref
,
wherein R k represents the resistance value of the memristor comprised in the memristive memory cell to be read, V bl_read_active is the bit line active voltage at the bit line corresponding to the j-th memory string, V k-1 is a voltage at the common source line during the first reading cycle, and V k is a voltage at the common source line during the second reading cycle.
9 . A memory reading method, applied to the memory according to claim 1 , wherein when memristive memory cells to be read are located in a first row to an n-th row of a j-th memory string on an i-th memory plane, the method comprises:
inputting a bit line active voltage at a bit line corresponding to the j th memory string; inputting bit line inactive voltages at other bit lines;
turning on all gating transistors on the i-th memory plane, and turning off other gating transistors;
before reading, making no current exist in transistors comprised in all memristive memory cells in the memory;
after starting reading, during an x-th reading cycle, turning on transistors comprised in memristive memory cells in the first row to an x-th row of the j-th memory string on the i-th memory plane, wherein a total of n reading cycles are required;
wherein i, j, n and x are all integers greater than zero, and i≤H, j≤M, 1<n≤N, 1≤x≤n.
10 . The memory reading method according to claim 9 , wherein a resistance value of a memristor in the first row comprised in the memristive memory cells to be read is determined according to a formula
R
1
=
V
bl
_
read
_
active
-
V
1
V
1
-
V
ref
R
ref
;
wherein R 1 represents the resistance value of the memristor in the first row comprised in the memristive memory cells to be read, V bl_read_active is the bit line active voltage at the bit line corresponding to the j-th memory string, V 1 is a voltage at the common source line during a first reading cycle, R ref is a resistance value of the reference resistor, and V ref represents a potential difference between the reference potential and ground;
a resistance value of a memristor in the x-th row comprised in the memristive memory cells to be read is determined according to a formula
R
x
=
(
V
bl
_
read
_
active
-
V
x
)
(
V
bl
_
read
_
active
-
V
x
-
1
)
(
V
bl
_
read
_
active
-
V
ref
)
(
V
x
-
V
x
-
1
)
R
ref
,
wherein R x represents the resistance value of the memristor comprised in the memristive memory cell in the x-th row comprised in the memristive memory cells to be read, V bl_read_active is the bit line active voltage at the bit line corresponding to the j-th memory string, V x-1 is a voltage at the common source line during an (x−1)-th reading cycle, and V x is a voltage at the common source line during the x-th reading cycle.
11 . A memory writing method, applied to the memory according to claim 1 , wherein a target resistance value is to be written to a memristive memory cell to be written, and when a memristive memory cell to be written is located in a k-th row of a j-th memory string on an i-th memory plane, the method comprises:
determining a level difference according to the target resistance value, and setting the level difference between the common source line and a bit line corresponding to the j-th memory string, wherein each word line corresponding to a first row to the k-th row of the j-th memory string has a word line level, and the level difference and word line levels are used to turn on transistors comprised in memristive memory cells in the first row to the k-th row;
turning on all gating transistors on the i-th memory plane, and turning off other gating transistors;
wherein except for the memristive memory cells in the first row to the k-th row, no current exists in other transistors;
wherein i, j and k are all integers greater than zero, and i≤H, j≤M, k≤N.
12 . The memory writing method according to claim 11 , further comprising:
when k>1, determining the level difference according to the target resistance value, and before setting the level difference between the common source line and the bit line corresponding to the j-th memory string, reading and saving original resistance values of memristive memory cells in the first row to a (k−1)-th row of the j-th memory string on the i-th memory plane;
wherein i, j, k and x are all integers greater than zero, and i≤H, j≤M, 1<k≤N, 1≤x≤k−1.
13 . The memory writing method according to claim 12 , wherein at the same time as writing to the memristive memory cells to be written, the memristive memory cells in the first row to the (k−1)-th row of the j-th memory string on the i-th memory plane are also written to, and the target resistance value of the k-th row is to be written to each memristive memory cell.
14 . A memory erasing method, applied to the memory according to claim 1 , wherein when a memory string to be erased is a j-th memory string corresponding to an i-th memory plane, the method comprises:
setting a level difference between the common source line and a bit line corresponding to the j-th memory string, wherein each word line corresponding to the j-th memory string has a word line level, and the level difference and word line levels are used to turn on each transistor corresponding to the j-th memory string;
turning on all gating transistors corresponding to the i-th memory plane; and turning off other gating transistors;
wherein except for the j-th memory string, no current exists in other transistors.
15 . The memory writing method according to claim 12 , wherein reading and saving the original resistance values of the memristive memory cells in the first row to the (k−1)-th row of the j-th memory string on the i-th memory plane comprises:
inputting a bit line active voltage at the bit line corresponding to the j-th memory string; inputting bit line inactive voltages at others bit lines;
turning on all gating transistors on the i-th memory plane, and turning off other gating transistors;
before reading, making no current exist in transistors comprised in all memristive memory cells in the memory;
after starting reading, during an x-th reading cycle, turning on transistors comprised in memristive memory cells in the first row to an x-th row of the j-th memory string on the i-th memory plane;
wherein i, j, k and x are all integers greater than zero, and i≤H, j≤M, 1<k≤N, 1≤x≤k−1.
16 . The memory writing method according to claim 12 , wherein after turning on all gating transistors on the i-th memory plane and turning off the other gating transistors, the method further comprises: by taking the original resistance values corresponding to the memristive memory cells in the (k−1)-th row to the first row of the j-th memory string on the i-th memory plane as corresponding target resistance values, rewriting to the memristive memory cells in the (k−1)-th row to the first row of the j-th memory string on the i-th memory plane in sequence.
17 . The memory writing method according to claim 16 , wherein steps of rewriting to the memristive memory cells in the (k−1)-th row to the first row of the j-th memory string on the i-th memory plane in sequence are identical with steps of writing to the memristive memory cell to be written in the k-th row of a j-th memory string on the i-th memory plane.