Nonvolatile memory cell operating by increasing order in polycrystalline semiconductor material
First Claim
1. A nonvolatile memory cell comprising:
- a first conductor;
a diode comprising amorphous or polycrystalline semiconductor material; and
a second conductor, the semiconductor diode disposed between the first conductor and the second conductor, wherein before application of a programming voltage the diode has a first maximum barrier height, and after application of the programming voltage the diode has a second maximum barrier height, the second maximum barrier height at least 1.5 times the first maximum barrier height.
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Abstract
A nonvolatile memory cell is described, the memory cell comprising a semiconductor diode. The semiconductor material making up the diode is formed with significant defect density, and allows very low current flow at a typical read voltage. Application of a programming voltage permanently changes the nature of the semiconductor material, resulting in an improved diode. The programmed diode allows much higher current flow, in some embodiments one, two or three orders of magnitude higher, at the same read voltage. The difference in current allows a programmed memory cell to be distinguished from an unprogrammed memory cell. Fabrication techniques to generate an advantageous unprogrammed defect density are described. The memory cell of the present invention can be formed in a monolithic three dimensional memory array, having multiple stacked memory levels formed above a single substrate.
321 Citations
61 Claims
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1. A nonvolatile memory cell comprising:
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a first conductor;
a diode comprising amorphous or polycrystalline semiconductor material; and
a second conductor, the semiconductor diode disposed between the first conductor and the second conductor, wherein before application of a programming voltage the diode has a first maximum barrier height, and after application of the programming voltage the diode has a second maximum barrier height, the second maximum barrier height at least 1.5 times the first maximum barrier height. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A nonvolatile memory cell comprising:
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a first conductor;
a second conductor; and
a polycrystalline semiconductor junction diode disposed between the first and second conductors, wherein a data state of the memory cell is determined by a state of an antifuse, and wherein the polycrystalline semiconductor junction diode is the antifuse. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for forming and programming a nonvolatile memory cell, the method comprising:
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forming a first conductor;
forming a second conductor;
depositing and doping semiconductor material to form a semiconductor junction diode, the semiconductor junction diode disposed between the first and second conductors;
crystallizing the semiconductor material such that the semiconductor junction diode is polycrystalline, wherein, during the crystallizing step, the semiconductor material is not in contact with a template material having a lattice mismatch of less than 12 percent with the semiconductor material; and
programming the memory cell by applying a programming voltage between the first and second conductors, wherein no resistance-switching element having its resistance changed by application of the programming voltage by more than a factor of two is disposed between the semiconductor junction diode and the first conductor or between the semiconductor junction diode and the second conductor. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A monolithic three dimensional memory array comprising:
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a) a first memory level above a substrate, the first memory level comprising;
i) a first plurality of substantially parallel conductors;
ii) a second plurality of substantially parallel conductors above the first conductors;
iii) a first plurality of semiconductor junction diodes, each first diode disposed between one of the first conductors and one of the second conductors; and
iv) a first plurality of one-time-programmable memory cells, each first memory cell adapted to be programmed by application of a programming voltage, each memory cell comprising a portion of one of the first conductors, a portion of one of the second conductors, and one of the first diodes, wherein before programming, each first diode has a first maximum barrier height, and after programming, each first diode has a second maximum barrier height, the second maximum barrier height at least 1.5 times the first maximum barrier height; and
b) a second memory level monolithically formed above the first memory level. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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36. A monolithic three dimensional memory array comprising:
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a) a first memory level comprising;
i) a plurality of bottom conductors;
ii) a plurality of top conductors; and
iii) a plurality of first polycrystalline semiconductor junction diodes, each diode disposed between one of the bottom and one of the top conductors; and
iv) a first memory cell comprising one of the first diodes, wherein the data state of the first memory cells is determined by the state of an antifuse, and wherein the diode of the first memory cell is the antifuse; and
b) a second memory level monolithically formed above the first memory level. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. A nonvolatile memory cell comprising:
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a first conductor;
a diode comprising amorphous or polycrystalline semiconductor material; and
a second conductor, the semiconductor diode disposed between the first conductor and the second conductor, wherein before application of a programming voltage the diode has a first rectification ratio at a read voltage between about 0.5 and about 2.5 volts, and after application of the programming voltage the diode has a second rectification ratio at the read voltage, the second rectification ratio at least 10 times the first rectification ratio. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61)
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Specification