Apparatuses having a ferroelectric field-effect transistor memory array and related method
An apparatus comprises field-effect transistor (FET) structures stacked horizontally and vertically in a three-dimensional memory array architecture, gates extending vertically and spaced horizontally between the plurality of FET structures, and a ferroelectric material separating the FET structures and the gates. Individual ferroelectric FETs (FeFETs) are formed at intersections of the FET structures, the gates, and the ferroelectric material. Another apparatus comprises a plurality of bit lines and word lines. Each bit line has at least two sides that are coupled with a ferroelectric material such that each bit line is shared by neighboring gates to form a plurality of FeFETs. A method of operating a memory array comprises applying a combination of voltages to a plurality of word lines and digit lines for a desired operation for a plurality of FeFET memory cells, at least one digit line having the plurality of FeFET memory cells accessible by neighboring gates.
1. A memory device, comprising:
a first vertical string of memory cells, wherein each memory cell of the first vertical string is formed at an intersection between a respective access line and a first vertical structure of ferroelectric material that is common to the first vertical string.
2. The memory device of claim 1 , further comprising:
a second vertical string of memory cells offset from the first vertical string of memory cells, wherein each memory cell of the second vertical string is formed at an intersection between a respective access line and a second vertical structure of ferroelectric material that is common to the second vertical string.
3. The memory device of claim 1 , wherein the first vertical string of memory cells includes:
a first vertical stack including a first drain region, a first body region, and a first source region; and
a second vertical stack including a second drain region, a second body region, and a second source region, wherein each of the first drain region and the second drain region comprise an access line, and the first vertical stack and the second vertical stack are separated by a dielectric material.
4. The memory device of claim 1 , wherein the first vertical string of memory cells passes through memory cell gates extending horizontally, wherein each memory cell gate of the memory cell gates comprises an access line.
5. The memory device of claim 4 , wherein the first vertical string of memory cells includes a first vertical channel surrounded by the first vertical structure of ferroelectric material.
6. The memory device of claim 5 , wherein the first vertical channel is formed of poly-silicon.
7. The memory device of claim 5 , wherein the first vertical channel couples with a first select gate on a first end, and with a second select gate on a second end.
8. The memory device of claim 5 , wherein the first vertical channel is coupled to a bit line through a diffusion region.
9. The memory device of claim 4 , wherein the first vertical string comprises a first vertical channel coupled to a drain select gate, a source select gate, and the memory cell gates, wherein the memory cell gates are positioned between the drain select gate and the source select gate.
10. A memory device, comprising:
a three-dimensional memory array, comprising:
vertical strings of memory cells spaced apart from each other in a horizontal direction and another direction orthogonal to both the horizontal direction and a vertical direction;
ferroelectric material structures common to corresponding vertical strings of memory cells; and
memory cell gates coupled to the vertical strings and the corresponding ferroelectric material structures.
11. The memory device of claim 10 , wherein the vertical strings include stacks including a source region, a body region, and a drain region that are stacked vertically and extend in the another direction orthogonal to the vertical direction and the horizontal direction.
12. The memory device of claim 11 , wherein the memory cell gates extend in the vertical direction such that the corresponding ferroelectric material is disposed between each memory cell gate and the stacks of each corresponding vertical string.
13. The memory device of claim 10 , wherein the vertical strings include vertical channels extending in the vertical direction that pass through the memory cell gates extending in the horizontal direction.
14. A method of operating a memory device including a three-dimensional memory array, the method comprising:
applying a combination of voltages to access lines coupled to a number of vertical strings of memory cells of a three-dimensional memory array, wherein each memory cell of each vertical string of the number of vertical strings is formed at an intersection between a respective access line and a respective vertical structure of ferroelectric material that is common to each memory cell of the respective vertical string.
15. The method of claim 14 , wherein applying a combination of voltages comprises employing a V/3 selection scheme.
16. The method of claim 14 , wherein applying a combination of voltages comprises:
applying V G =3V, V S =0V, and V D =0V for a write operation for an individual memory cell;
applying V G =0V, V S =3V, and V D =3V for an erase operation for an individual memory cell; and
applying V G =1.5V, V S =1V, and V D =1V for a read operation for an individual memory cell.
17. The method of claim 14 , wherein applying the combination of voltages includes applying a positive gate-source voltage (V GS ) that has a larger amplitude than a coercive field of the ferroelectric material to cause a first polarization to be present within adjacent ferroelectric material for an individual memory cell.
18. The method of claim 17 , wherein applying the combination of voltages includes applying a negative gate-source voltage (−V GS ) that has a larger amplitude than a coercive field of the ferroelectric material to cause a second polarization to be present within the adjacent ferroelectric material for the individual memory cell.
19. The method of claim 14 , wherein applying the combination of voltages includes applying a gate-source voltage (V GS ) that does not have a larger amplitude than a coercive field of the ferroelectric material for an individual memory cell.
20. The method of claim 14 , wherein applying a combination of voltages comprises employing a V/2 selection scheme.