Method for using a memory cell comprising switchable semiconductor memory element with trimmable resistance
First Claim
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1. A method for changing and sensing data states for a nonvolatile memory cell, the method comprising:
- switching semiconductor material from a first stable resistivity state to a second stable resistivity state, the second resistivity state lower resistivity than the first resistivity state;
switching the semiconductor material from the second stable resistivity state to a third stable resistivity state, the third resistivity state higher resistivity than the second resistivity state; and
sensing the third resistivity state as a data state of the memory cell,wherein;
the memory cell comprises a portion of a first conductor, a portion of a second conductor, and a switchable memory element comprising the semiconductor material,the semiconductor material is selected from silicon, germanium, or an alloy of silicon and/or germanium,the switchable memory element is disposed between the first and second conductors,the semiconductor material in the first stable resistivity state has a first resistivity when a read voltage is applied to the semiconductor material;
the semiconductor material in the second stable resistivity state has a second resistivity when the read voltage is applied to the semiconductor material;
the semiconductor material in the third stable resistivity state has a third resistivity when the read voltage is applied to the semiconductor material;
the first resistivity, the second resistivity, and the third resistivity are different from each other;
the semiconductor material is a doped polycrystalline material that comprises a plurality of grain boundaries;
at least some dopant atoms move away from at least some of the plurality of grain boundaries, during switching the semiconductor material from the first stable resistivity state to the second stable resistivity state; and
at least some of the dopant atoms move to at least some of the plurality of grain boundaries, during switching the semiconductor material from the second stable resistivity state to the third stable resistivity state.
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Abstract
A nonvolatile memory cell comprising a diode formed of semiconductor material can store memory states by changing the resistance of the semiconductor material by application of a set pulse (decreasing resistance) or a reset pulse (increasing resistance.) In preferred embodiments, set pulses are applied with the diode under forward bias, while reset pulses are applied with the diode in reverse bias. By switching resistivity of the semiconductor material of the diode, a memory cell can be either one-time programmable or rewriteable, and can achieve two, three, four, or more distinct data states.
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Citations
50 Claims
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1. A method for changing and sensing data states for a nonvolatile memory cell, the method comprising:
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switching semiconductor material from a first stable resistivity state to a second stable resistivity state, the second resistivity state lower resistivity than the first resistivity state; switching the semiconductor material from the second stable resistivity state to a third stable resistivity state, the third resistivity state higher resistivity than the second resistivity state; and sensing the third resistivity state as a data state of the memory cell, wherein; the memory cell comprises a portion of a first conductor, a portion of a second conductor, and a switchable memory element comprising the semiconductor material, the semiconductor material is selected from silicon, germanium, or an alloy of silicon and/or germanium, the switchable memory element is disposed between the first and second conductors, the semiconductor material in the first stable resistivity state has a first resistivity when a read voltage is applied to the semiconductor material; the semiconductor material in the second stable resistivity state has a second resistivity when the read voltage is applied to the semiconductor material; the semiconductor material in the third stable resistivity state has a third resistivity when the read voltage is applied to the semiconductor material; the first resistivity, the second resistivity, and the third resistivity are different from each other; the semiconductor material is a doped polycrystalline material that comprises a plurality of grain boundaries; at least some dopant atoms move away from at least some of the plurality of grain boundaries, during switching the semiconductor material from the first stable resistivity state to the second stable resistivity state; and at least some of the dopant atoms move to at least some of the plurality of grain boundaries, during switching the semiconductor material from the second stable resistivity state to the third stable resistivity state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for changing and sensing data states for a nonvolatile memory cell, the method comprising:
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switching semiconductor material from a first stable resistivity state to a second stable resistivity state, the second resistivity state lower resistivity than the first resistivity state; switching the semiconductor material from the second stable resistivity state to a third stable resistivity state, the third resistivity state higher resistivity than the second resistivity state; switching the semiconductor material from the third stable resistivity state to a fourth stable resistivity state, the fourth resistivity state lower resistivity than the third resistivity state; and sensing the fourth resistivity state as a data state of the memory cell, wherein; the memory cell comprises a portion of a first conductor, a portion of a second conductor, and a switchable memory element comprising the semiconductor material, the semiconductor material is selected from silicon, germanium, or an alloy of silicon and/or germanium, the switchable memory element is disposed between the first and second conductors, the semiconductor material in the first stable resistivity state has a first resistivity when a read voltage is applied to the semiconductor material; the semiconductor material in the second stable resistivity state has a second resistivity when the read voltage is applied to the semiconductor material; the semiconductor material in the third stable resistivity state has a third resistivity when the read voltage is applied to the semiconductor material; the semiconductor material in the fourth stable resistivity state has a fourth resistivity when the read voltage is applied to the semiconductor material; and the first resistivity, the second resistivity, the third resistivity, and the fourth resistivity are different from each other; the semiconductor material is a doped polycrystalline material that comprises a plurality of grain boundaries; at least some dopant atoms move away from at least some of the plurality of grain boundaries, during switching the semiconductor material from the first stable resistivity state to the second stable resistivity state; and at least some of the dopant atoms move to at least some of the plurality of grain boundaries, during switching the semiconductor material from the second stable resistivity state to the third stable resistivity state. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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26. A method for changing and sensing data states for a nonvolatile memory cell, the nonvolatile memory cell comprising a polycrystalline or microcrystalline semiconductor junction diode comprising semiconductor material selected from silicon, germanium, or an alloy of silicon and/or germanium, the diode disposed between a first conductor and a second conductor, the method comprising:
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switching the semiconductor material from a first resistivity state to a second resistivity state, the second resistivity state lower resistivity than the first resistivity state; switching the semiconductor material from the second resistivity state to a third resistivity state, the third resistivity state higher resistivity than the second resistivity state; and sensing the third resistivity state as a data state of the memory cell, the semiconductor material in the first stable resistivity state has a first resistivity when a read voltage is applied to the semiconductor material; the semiconductor material in the second stable resistivity state has a second resistivity when the read voltage is applied to the semiconductor material; the semiconductor material in the third stable resistivity state has a third resistivity when the read voltage is applied to the semiconductor material; and the first resistivity, the second resistivity, and the third resistivity are different from each other; the semiconductor material is a doped polycrystalline material that comprises a plurality of grain boundaries; at least some dopant atoms move away from at least some of the plurality of grain boundaries, during switching the semiconductor material from the first stable resistivity state to the second stable resistivity state; and at least some of the dopant atoms move to at least some of the plurality of grain boundaries, during switching the semiconductor material from the second stable resistivity state to the third stable resistivity state. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A method for programming and sensing a rewriteable memory cell, the method comprising:
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switching semiconductor material from a first stable resistivity state to a second stable resistivity state, the second resistivity state lower resistivity than the first resistivity state; switching the semiconductor material from the second stable resistivity state to a third stable resistivity state, the third resistivity state lower resistivity than the second resistivity state; and sensing the third resistivity state as a data state of the memory cell, wherein; the memory cell comprises a portion of a first conductor, a portion of a second conductor, and a switchable memory element comprising the semiconductor material, the semiconductor material is selected from silicon, germanium, or an alloy of silicon and/or germanium, the switchable memory element is disposed between the first and second conductors, the semiconductor material in the first stable resistivity state has a first resistivity when a read voltage is applied to the semiconductor material; the semiconductor material in the second stable resistivity state has a second resistivity when the read voltage is applied to the semiconductor material; the semiconductor material in the third stable resistivity state has a third resistivity when the read voltage is applied to the semiconductor material; and the first resistivity, the second resistivity, and the third resistivity are different from each other; the semiconductor material is a doped polycrystalline material that comprises a plurality of grain boundaries; and at least some dopant atoms move away from at least some of the plurality of grain boundaries, during switching the semiconductor material from the first stable resistivity state to the second stable resistivity state. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification