Self-aligned floating gate in a vertical memory structure
A memory device or electronic system may include a memory cell body extending from a substrate, a self-aligned floating gate separated from the memory cell body by a tunneling dielectric film, and a control gate separated from the self-aligned floating gate by a blocking dielectric film. The floating gate is flanked by the memory cell body and the control gate to form a memory cell, and the self-aligned floating gate is at least as thick as the control gate. Methods for building such a memory device are also disclosed.
1. A memory device comprising:
a memory cell body extending from a substrate;
a self-aligned floating gate separated from the memory cell body by a tunneling dielectric film;
a control gate separated from the floating gate by a blocking dielectric film;
wherein the self-aligned floating gate is flanked by the memory cell body and the control gate to form a memory cell, and the self-aligned floating gate is at least as thick as the control gate;
wherein the memory cell body comprises a pillar with a substantially circular cross-section, the self-aligned floating gate comprises an annulus around the memory cell body, and the control gate surrounds the self-aligned floating gate; and
wherein the floating gate and the control gate are positioned between the substrate and a tier insulating layer, and the pillar with a substantially circular cross-section extends through the tier insulating layer.
2. The memory device of claim 1 , further comprising sacrificial layers sandwiching the control gate.
3. The memory device of claim 1 , wherein a near surface of the control gate is no closer to the substrate than a near surface of the self-aligned floating gate; and
a far surface of the control gate is no farther from the substrate than a far surface of the self-aligned floating gate.
4. The memory device of claim 1 , wherein the memory cell body, the self-aligned floating gate and the control gate comprise polysilicon;
the tunneling dielectric film is comprised of an oxide; and
the blocking dielectric film is an inter-poly dielectric comprising a nitride film sandwiched between two oxide films.
5. The memory device of claim 1 , wherein the self-aligned floating gate is a first floating gate, the control gate is a first control gate, and the memory cell is a first memory cell, the memory device further comprising:
a second floating gate separated from the memory cell body by the tunneling dielectric film;
a second control gate separated from the second floating gate by the blocking dielectric film; and
the tier insulating layer;
wherein the second floating gate and the second control gate are positioned on an opposite side of the tier insulating layer from the first floating gate and the first control gate; and
wherein the second floating gate is flanked by the memory cell body and the second control gate to form a second memory cell, and the second floating gate is at least as thick as the second control gate.
6. The memory device of claim 5 , further comprising:
a first sacrificial layer situated between the first control gate and the tier insulating layer; and
a second sacrificial layer situated between the tier insulating layer and the second control gate;
wherein the first and second sacrificial layers are differentiated from the tier insulating layer.
7. The memory device of claim 6 , wherein the first and second floating gates are separated from the tier insulating layer by the blocking dielectric film; and
the first and second sacrificial layers are individually no thinner than the blocking dielectric film.
8. An electronic system comprising:
supervisory circuitry; and
at least one memory device coupled to the supervisory circuitry, the memory device comprising two or more memory cells individually interposed between tier insulating layers;
a memory cell of the two or more memory cells comprising:
a body comprising a portion of a polysilicon pillar;
an annular shaped floating gate positioned around the polysilicon pillar, and separated from the polysilicon pillar by a tunneling dielectric film; and
a control gate that surrounds the floating gate and is separated from the floating gate by a blocking dielectric film;
wherein the floating gate is at least as thick as the control gate, and the polysilicon pillar is shared by the two or more memory cells and extends through the tier insulating layers.
9. The electronic system of claim 8 , further comprising I/O circuitry coupled to the supervisory circuitry.
10. The electronic system of claim 8 , wherein the electronic system comprises a solid-state drive.
11. The electronic system of claim 8 , wherein a shortest path from any point in the control gate to the polysilicon passes through the floating gate.
12. The electronic system of claim 8 , the memory cell further comprising sacrificial layers situated between the control gate and the tier insulating layers;
wherein the sacrificial layers are differentiated from the tier insulating layers.
13. The electronic system of claim 12 , wherein the floating gate is separated from the tier insulating layers by the blocking dielectric film;
wherein the sacrificial layers are individually no thinner than the blocking dielectric film.
14. The electronic system of claim 13 , wherein the floating gate and the control gate comprise polysilicon;
the tunneling dielectric film comprise an oxide; and
the blocking dielectric film is an inter-poly dielectric comprising a nitride film sandwiched between two oxide films.