Memory device, integrated circuit device and method
A memory device includes a bit line, a word line, a memory cell, select bit lines, and a controller. The memory cell includes a first transistor, data storage elements, and second transistors corresponding to the data storage elements. The first transistor includes a gate electrically coupled to the word line, a first source/drain, and a second source/drain. Each of the select bit lines is electrically coupled to a gate of a corresponding second transistor. Each data storage element and the corresponding second transistor are electrically coupled in series between the first source/drain of the first transistor and the bit line. The controller turns ON the first transistor and a selected second transistor, and, while the first transistor and the selected second transistor are turned ON, applies different voltages to the bit line to perform corresponding different operations on the data storage element coupled to the selected second transistor.
1. A memory device, comprising:
at least one bit line;
at least one word line;
at least one memory cell comprising:
a first transistor comprising a gate electrically coupled to the word line, a first source/drain, and a second source/drain;
a plurality of data storage elements; and
a plurality of second transistors corresponding to the plurality of data storage elements;
a plurality of select bit lines each electrically coupled to a gate of a corresponding second transistor among the plurality of second transistors; and
a controller electrically coupled to the at least one memory cell via the at least one word line, the at least one bit line, and the plurality of select bit lines,
wherein each data storage element among the plurality of data storage elements and the corresponding second transistor are electrically coupled in series between the first source/drain of the first transistor and the bit line, and
wherein the controller is configured to
turn ON the first transistor and a selected second transistor among the plurality of second transistors, correspondingly through the at least one word line and the select bit line coupled to the selected second transistor, and
while the first transistor and the selected second transistor are turned ON, apply different voltages to the at least one bit line, the different voltages corresponding to different operations to be performed on the data storage element coupled to the selected second transistor.
2. The memory device of claim 1 , wherein
each data storage element among the plurality of data storage elements is a non-volatile, reprogrammable data storage element.
3. The memory device of claim 1 , wherein each data storage element among the plurality of data storage elements comprises
a first electrode,
a second electrode, and
a dielectric material sandwiched between the first electrode and the second electrode, and electrically switchable between
a first state corresponding to a first logic value stored in the data storage element, and
a second state corresponding to a second logic value stored in the data storage element.
4. The memory device of claim 1 , wherein
each data storage element among the plurality of data storage elements is a resistive random access memory (RRAM) element.
5. The memory device of claim 1 , wherein
the controller is configured to, in a reset operation of a selected data storage element among the plurality of data storage elements,
apply a turn-ON voltage via the at least one word line to the gate of the first transistor to turn ON the first transistor,
apply a further turn-ON voltage via the corresponding select bit line to the gate of the second transistor corresponding to the selected data storage element,
apply a turn-OFF voltage via the corresponding select bit lines to the gates of other second transistors among the plurality of second transistors, and
while the first transistor and the second transistor corresponding to the selected data storage element are turned ON and the other second transistors are turned OFF, apply a reset voltage to the at least one bit line to switch a datum stored in the selected data storage element from a first logic value to a second logic value.
6. The memory device of claim 1 , further comprising:
at least one source line electrically coupled to the second source/drain of the first transistor, wherein
the controller is electrically coupled to the at least one memory cell further via the at least one source line, and
the controller is configured to, in a reset operation of a selected data storage element among the plurality of data storage elements,
apply a turn-ON voltage via the at least one word line to the gate of the first transistor to turn ON the first transistor,
apply a further turn-ON voltage via the corresponding select bit line to the gate of the second transistor corresponding to the selected data storage element,
apply a turn-OFF voltage via the corresponding select bit lines to the gates of other second transistors among the plurality of second transistors, and
while the first transistor and the second transistor corresponding to the selected data storage element are turned ON and the other second transistors are turned OFF, apply a reset voltage to one of the at least one bit line and the at least one source line while grounding the other of the at least one bit line and the at least one source line, to switch a datum stored in the selected data storage element from a first logic value to a second logic value.
7. The memory device of claim 1 , wherein
the at least one bit line comprises first and second bit lines,
the at least one word line comprises first and second word lines,
the at least one memory cell comprises first and second memory cells,
the memory device further comprises a common source line electrically coupled to the second source/drains of the first transistors of the first and second memory cells, and
the plurality of select bit lines comprises:
a plurality of first select bit lines each electrically coupled to a gate of a corresponding second transistor among the plurality of second transistors in the first memory cell; and
a plurality of second select bit lines each electrically coupled to a gate of a corresponding second transistor among the plurality of second transistors in the second memory cell.
8. The memory device of claim 1 , further comprising:
a substrate having thereon the first transistor;
an interconnect structure over the substrate; and
a metal-insulator-metal (MIM) structure over the interconnect structure and comprising the plurality of data storage elements stacked on top each other in a thickness direction of the substrate, the interconnect structure electrically coupling the first source/drain of the first transistor to the MIM structure,
wherein the plurality of second transistors is over the MIM structure, and electrically coupled correspondingly to the plurality of data storage elements in the MIM structure.
9. An integrated circuit (IC) device, comprising:
a substrate having thereon a first transistor;
a plurality of data storage elements arranged at different heights over the substrate;
a plurality of second transistors over the plurality of data storage elements;
a word line coupled to a gate of the first transistor; and
a plurality of select bit lines each electrically coupled to a gate of a corresponding second transistor among the plurality of second transistors,
wherein each data storage element among the plurality of data storage elements is electrically coupled in series between a first source/drain of the first transistor and a first source/drain of a corresponding second transistor among the plurality of second transistors.
10. The IC device of claim 9 , further comprising:
a metal-insulator-metal (MIM) structure over the substrate, the MIM structure comprising the plurality of data storage elements.
11. The IC device of claim 10 , wherein
each data storage element among the plurality of data storage elements is a resistive random access memory (RRAM) element.
12. The IC device of claim 9 , wherein
the plurality of data storage elements is arranged on top each other in a thickness direction of the substrate,
each data storage element among the plurality of data storage elements comprises a first electrode, a second electrode, and a dielectric material sandwiched between the first electrode and the second electrode,
the first electrodes of the plurality of data storage elements are arranged on top each other in the thickness direction, and electrically coupled correspondingly to the first source/drains of the plurality of second transistors, and
the second electrodes of the plurality of data storage elements are electrically coupled to the first source/drain of the first transistor.
13. The IC device of claim 12 , further comprising:
a plurality of electrode layers arranged on top of each other in the thickness direction of the substrate, and electrically isolated from each other by interlayer dielectric (ILD) layers;
a via extending in the thickness direction through the plurality of electrode layers and the ILD layers;
a dielectric layer over an inner wall of the via; and
a conductor in the via,
wherein
the plurality of electrode layers correspondingly comprises the first electrodes of the plurality of data storage elements,
the conductor comprises the second electrodes of the plurality of data storage elements, and
the dielectric layer comprises a plurality of portions each sandwiched between the conductor and the first electrode of a corresponding data storage element among the plurality of data storage elements, and defining the dielectric material of the corresponding data storage element.
14. The IC device of claim 13 , further comprising:
a plurality of via structures electrically coupling the first electrodes of the plurality of data storage elements correspondingly to the first source/drains of the plurality of second transistors,
wherein
the first electrodes of the plurality of data storage elements are arranged in a stepwise structure, and
the plurality of via structures has different heights.
15. The IC device of claim 9 , further comprising:
a bit line over the plurality of second transistors, and electrically coupled to second source/drains of the plurality of second transistors,
wherein
the bit line extends in a first direction, and
the plurality of select bit lines extends in a second direction transverse to the first direction.
16. The IC device of claim 9 , further comprising:
a further first transistor on the substrate;
a plurality of further data storage elements arranged at different heights over the substrate; and
a plurality of further second transistors over the plurality of further data storage elements;
wherein
each further data storage element among the plurality of further data storage elements is electrically coupled in series between a first source/drain of the further first transistor and a first source/drain of a corresponding further second transistor among the plurality of further second transistors, and
a second source/drain of the first transistor is a second source/drain of the further first transistor.
17. The IC device of claim 9 , wherein
the plurality of second transistors comprises thin-film transistors (TFT).
18. A method, comprising:
forming a first transistor over a substrate;
forming an interconnect structure over the first transistor;
forming a plurality of data storage elements and a stepwise structure over the interconnect structure, the interconnect structure electrically coupling a first electrode of each of the plurality of data storage elements to a first source/drain of the first transistor; and
forming a plurality of second transistors over the plurality of data storage elements and the stepwise structure, a second electrode of each of the plurality of data storage elements electrically coupled by the stepwise structure to a first source/drain of a corresponding second transistor among the plurality of second transistors.
19. The method of claim 18 , wherein said forming the plurality of data storage elements and the stepwise structure comprises:
alternatingly depositing a plurality of electrode layers and interlayer dielectric (ILD) layers over the interconnect structure;
forming a via through the plurality of electrode layers and ILD layers;
depositing a dielectric layer over an inner wall and a bottom wall of the via;
removing the dielectric layer on the bottom wall of the via to expose a conductive pattern of the interconnect structure, the conductive pattern electrically coupled to the first source/drain of the first transistor;
filling a conductive material into the via; and
patterning the plurality of electrode layers and ILD layers to obtain the stepwise structure.
20. The method of claim 19 , further comprising:
depositing an insulating layer over the stepwise structure;
forming a plurality of via structures in the insulating layer over the stepwise structure, the plurality of via structures having different heights and electrically coupled correspondingly to the plurality of electrode layers,
wherein in said forming the plurality of second transistors, a first source/drain of each of the plurality of second transistors is formed over and in electrical contact with an upper end of a corresponding via structure among the plurality of via structures;
forming a bit line over the plurality of second transistors, the bit line electrically coupled to second source/drains of the plurality of second transistors; and
forming a plurality of select bit lines over the plurality of second transistors, the plurality of select bit lines electrically coupled correspondingly to gates of the plurality of second transistors.