Memory device including electrical circuit configured to provide reversible bias across the PMC memory cell to perform erase and write functions
View Patent ↗An integrated circuit including circuitry configured to perform erase and write functions. One embodiment includes a programmable metallization memory cell, a conductive line connected to a first node of the memory cell, and a bitline connected to a second node of the memory cell. The memory device also includes circuitry configured to perform a write operation by applying a first voltage to the conductive line and a second voltage to the bitline, perform an erase operation by applying the second voltage to the conductive line and the first voltage to the bitline, and apply a voltage midway between the first voltage and the second voltage to the conductive line when the write operation and the erase operation are not being performed.
1. A method for operating an integrated circuit, the method comprising:
programming a programmable metallization memory cell, wherein programming the memory cell comprises:
applying a first voltage to a first driver, wherein the first driver applies a first programming voltage to a first node of the memory cell when the first voltage is applied and limits a current applied to the memory cell; and
applying a second voltage to a second driver, wherein the second driver applies a second programming voltage to a second node of the memory cell when the second voltage is applied; and
erasing the memory cell, wherein erasing the memory cell comprises
applying the second voltage to the first driver, wherein the first driver applies the second programming voltage to the first node of the memory cell when the second voltage is applied; and
applying the first voltage to the second driver, wherein the second driver applies the first programming voltage to the second node of the memory cell when the first voltage is applied.
2. The method of claim 1 , further comprising:
selecting the memory cell, wherein selecting the memory cell comprises asserting a voltage on a wordline, thereby connecting the second node of the memory cell to the second driver.
3. The method of claim 1 , wherein applying the first and second programming voltage to the first and second node, respectively, of the memory cell decreases a resistance of the memory cell, and wherein applying the first and second programming voltage to the second and first node, respectively, of the memory cell increases the resistance of the memory cell.
4. The method of claim 1 , further comprising:
reading a state of the memory cell, wherein reading the state of the memory cell comprises:
applying a voltage to a read control input of the second driver, wherein the second driver applies a read voltage to the second node of the memory cell when the voltage is applied; and
sensing a current through the memory cell resulting from the read voltage, wherein the current is indicative of a resistance of the memory cell.
5. An integrated circuit comprising:
a programmable metallization memory cell of a conductive bridging random access memory;
a conductive line connected to a first node of the memory cell;
a bitline connected to a second node of the memory cell; and
circuitry configured to:
perform a write operation by applying a first voltage to the conductive line and a second voltage to the bitline;
perform an erase operation by applying the second voltage to the conductive line and the first voltage to the bitline;
apply a voltage between the first voltage and the second voltage to the conductive line when the write operation and the erase operation are not being performed; and
limit a current applied to the memory cell during a program operation of the memory cell.
6. The integrated circuit of claim 5 , wherein the conductive line and the bitline are electrically isolated from the first voltage and the second voltage when the write operation and the erase operation are not being performed.
7. The integrated circuit of claim 5 , further comprising:
an access transistor located between the second node of the memory cell and the bitline;
a wordline controlling the access transistor;
a wordline driver configured to selectively connect the bitline to the second node of the memory cell during a write operation or an erase operation of the memory cell;
a first transistor configured to selectively apply the first voltage to the conductive line;
a second transistor configured to selectively apply the second voltage to the conductive line; and
a third transistor configured to selectively apply the voltage between the first voltage and the second voltage to the conductive line.
8. The integrated circuit of claim 5 , wherein the circuitry is further configured to:
perform a read operation by applying a read voltage to the conductive line and sensing a current indicative of a state of the memory cell.
9. An integrated circuit comprising:
a programmable metallization memory cell;
a first driver for applying a first erasing and a first programming voltage to a first node of the memory cell;
a second driver for applying a second erasing and a second programming voltage to a second node of the memory cell;
circuitry configured to:
perform a programming operation of the memory cell, wherein the circuitry causes the first driver to apply the first programming voltage and the second driver to apply the second programming voltage; and
perform an erasing operation of the memory cell, wherein the circuitry causes the first driver to apply the first erasing voltage and the second driver to apply the second erasing voltage,
wherein the first driver contains a current limiting circuit designed to limit a current applied to the memory cell during a program operation of the memory cell.
10. The memory device of claim 9 , wherein the second driver contains a circuit for applying a read voltage to the memory cell during a read operation of the memory cell.
11. An integrated circuit comprising:
a programmable metallization memory cell;
a bitline connected to a first node of the memory cell;
a conductive line connected to a second node of the memory cell;
a first driver comprising a first programming input and a first erasing input, wherein the first driver is configured to:
in response to a first voltage being applied to the first programming input, apply a first programming voltage to the bitline; and
in response to a second voltage being applied to the first erasing input, apply a first erasing voltage to the bitline; and
a second driver comprising a second programming input and a second erasing input, wherein the second driver is configured to:
in response to the second voltage being applied to the second programming input, apply a second programming voltage to the conductive line; and
in response to the first voltage being applied to the to the second erasing input, apply a second erasing voltage to the conductive line,
wherein the first driver comprises a current limiting circuit designed to limit a current applied to the memory cell during a program operation of the memory cell.
12. The memory device of claim 11 :
wherein the second driver further comprises:
a read control input, wherein the second driver is further configured to:
in response to a voltage applied to the read control input, apply a read voltage to the conductive line; and
wherein the memory device further comprises sensing circuitry for sensing a current through the memory cell when the read voltage is applied to the conductive line, wherein the current is indicative of a state of the memory device.
13. The integrated circuit of claim 11 , further comprising a wordline, wherein the wordline connects the bitline to the first node of the memory cell when a voltage is applied to the wordline.
14. The integrated circuit of claim 11 , wherein the first driver and the second driver electrically isolate the programming and erasing voltages from the wordline and bitline when the memory cell is not being accessed.
15. The integrated circuit of claim 11 , wherein an intermediate voltage is applied to the conductive line, wherein the intermediate voltage is between the first programming voltage and the second programming voltage.
16. An integrated circuit comprising:
a conductive line;
a bitline;
a programmable metallization memory cell of a conductive bridging random access memory, the memory cell coupled between the conductive line and the bitline; and
a circuit configured to:
perform a write operation by applying a first voltage to the conductive line and a second voltage to the bitline;
perform an erase operation by applying the second voltage to the conductive line and the first voltage to the bitline;
apply a voltage between the first voltage and the second voltage to the conductive line when the write operation and the erase operation are not being performed; and
limit a current applied to the memory cell during a program operation of the memory cell.