Nonvolatile memory and method of driving the same
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorKiyoshi Kato
Life of this patent
Estimating the term…
Abstract
The nonvolatile memory according to the present invention can precisely read information included in a memory transistor subject to a shift phenomenon because electrical read is performed on the memory transistor by using a reference voltage generated from a refresh memory transistor. Further, according to the present invention, the period of time during which the refresh operation is performed can be longer than before, which improves the reliability of information stored in the memory transistor. Furthermore, the margin between distributions of threshold voltages can be reduced, which improves the scale of integration of the multilevel nonvolatile memory.
Claims90
A nonvolatile memory having a memory transistor and a reference memory transistor, comprising:
- read means for electrically reading a threshold voltage of the memory transistor by using a threshold voltage of the reference memory transistor;
- first write means for performing electrical write on the memory transistor until the threshold voltage of the memory transistor is higher than a first reference voltage;
- and
- second write means for performing electrical write on the reference memory transistor until the threshold voltage of the reference memory transistor is higher than a second reference voltage.
A nonvolatile memory having a memory transistor and a reference memory transistor, comprising:
- first write means for performing electrical write on the memory transistor until a first threshold voltage of the memory transistor, which is read based on a reference voltage of the reference memory transistor, and a second threshold voltage of the memory transistor, which is read based on a first reference voltage of the reference memory transistor belong to a distribution of threshold voltages for same information;
- and
- second write means for performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
A nonvolatile memory having a unit cell in which multiple memory transistors are connected in series and a reference memory transistor, comprising:
- read means for electrically reading a threshold voltage of the memory transistor by using a threshold voltage of the reference memory transistor;
- first write means for performing electrical write on the memory transistor until the threshold voltage of the memory transistor is higher than a first reference voltage;
- and
- second write means for performing electrical write on the reference memory transistor until the threshold voltage of the reference memory transistor is higher than a second reference voltage.
A nonvolatile memory having a unit cell in which multiple memory transistors are connected in series and a reference memory transistor, comprising:
- first write means for performing electrical write on the memory transistor until a first threshold voltage of the memory transistor, which is read from a reference voltage of the reference memory transistor, and a second threshold voltage of the memory transistor, which is read from a first reference voltage of the reference memory transistor belong to a distribution of threshold voltages for same information;
- and
- second write means for performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
A nonvolatile memory having a memory transistor, a reference memory transistor and a timer, comprising:
- first write means for performing electrical write on the memory transistor for each time when an elapsed time measured by the timer reaches an arbitrarily preset time until a threshold voltage of the memory transistor, which is read based on a reference voltage of the reference memory transistor is higher than a first reference voltage;
- and
- second write means for performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
A method of driving a nonvolatile memory having a memory transistor and a reference memory transistor, comprising:
- electrically reading a threshold voltage of the memory transistor by using a threshold voltage of the reference memory transistor;
- performing electrical write on the memory transistor until the threshold voltage of the memory transistor is higher than a first reference voltage;
- and
- performing electrical write on the reference memory transistor until the threshold voltage of the reference memory transistor is higher than a second reference voltage.
A method of driving a nonvolatile memory having a memory transistor and a reference memory transistor, comprising:
- performing electrical write on the memory transistor until a first threshold voltage of the memory transistor, which is read based on a reference voltage of the reference memory transistor, and a second threshold voltage of the memory transistor, which is read based on a first reference voltage of the reference memory transistor belong to a distribution of threshold voltages for same information;
- and
- performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
A method of driving a nonvolatile memory having a unit cell in which multiple memory transistors are connected in series and a reference memory transistor, comprising:
- electrically reading a threshold voltage of the memory transistor by using a threshold voltage of the reference memory transistor;
- performing electrical write on the memory transistor until the threshold voltage of the memory transistor is higher than a first reference voltage;
- and
- performing electrical write on the reference memory transistor until the threshold voltage of the reference memory transistor is higher than a second reference voltage.
A method of driving a nonvolatile memory having a unit cell in which multiple memory transistors are connected in series and a reference memory transistor, comprising:
- performing electrical write on the memory transistor until a first threshold voltage of the memory transistor, which is read from a reference voltage of the reference memory transistor, and a second threshold voltage of the memory transistor, which is read from a first reference voltage of the reference memory transistor belong to a distribution of threshold voltages for same information;
- and
- performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
A method of driving a nonvolatile memory having a memory transistor, a reference memory transistor and a timer, comprising:
- performing electrical write on the memory transistor for each time when an elapsed time measured by the timer reaches an arbitrarily preset time until a threshold voltage of the memory transistor, which is read based on a reference voltage of the reference memory transistor, is higher than a first reference voltage;
- and
- performing electrical write on the reference memory transistor until a threshold voltage of the reference memory transistor is higher than a second reference voltage.
Dependencies are inferred from the claim text.