Charge storage apparatus and methods
Methods of forming multi-tiered semiconductor devices are described, along with apparatus and systems that include them. In one such method, an opening is formed in a tier of semiconductor material and a tier of dielectric. A portion of the tier of semiconductor material exposed by the opening is processed so that the portion is doped differently than the remaining semiconductor material in the tier. At least substantially all of the remaining semiconductor material of the tier is removed, leaving the differently doped portion of the tier of semiconductor material as a charge storage structure. A tunneling dielectric is formed on a first surface of the charge storage structure and an intergate dielectric is formed on a second surface of the charge storage structure. Additional embodiments are also described.
1. A method comprising:
forming an opening in a tier of semiconductor material and a tier of dielectric;
processing a portion of the tier of semiconductor material exposed by the opening so that the portion is doped differently than the remaining semiconductor material in the tier;
removing at least substantially all of the remaining semiconductor material of the tier, wherein the differently doped portion of the tier of semiconductor material comprises a charge storage structure;
forming a tunneling dielectric on a first surface of the charge storage structure; and
forming an intergate dielectric on a second surface of the charge storage structure.
2. The method of claim 1 , wherein forming an opening in a tier of semiconductor material and a tier of dielectric comprises forming the opening in alternating tiers of polysilicon and dielectric, and wherein processing a portion of the tier of polysilicon exposed by the opening so that the portion is doped differently than the remaining polysilicon in the tier comprises processing a respective portion of each of the tiers of polysilicon exposed by the opening so that the respective portions are doped differently than the remaining polysilicon of the tiers.
3. The method of claim 1 , wherein processing a portion of the tier of semiconductor material exposed by the opening so that the portion is doped differently than the remaining semiconductor material in the tier comprises doping a portion of a tier of polysilicon, wherein the remaining polysilicon of the tier comprises undoped polysilicon.
4. The method of claim 3 , wherein doping the portion of the tier of polysilicon comprises adding a p-type dopant through the opening to the portion of polysilicon exposed by the opening.
5. The method of claim 3 , wherein doping the portion of the tier of polysilicon comprises forming a p-type polysilicon plug in the opening and diffusing a p-type dopant from the plug into the portion.
6. The method of claim 3 , wherein doping the portion of the tier of polysilicon comprises implanting Boron.
7. The method of claim 1 , wherein forming an opening comprises forming a hole.
8. A method comprising:
forming a plurality of charge storage structures, wherein each charge storage structure at least partially surrounds a vertical opening in a semiconductor construction, and wherein each charge storage structure is separated from an adjacent charge storage structure by a first dielectric;
adding a dopant through the vertical opening to portions of polysilicon exposed by the opening;
removing substantially all remaining undoped polysilicon to leave a plurality of doped charge storage structures;
forming a second dielectric on each charge storage structure in the opening;
forming silicon on the second dielectric in the vertical opening, wherein the second dielectric separates the charge storage structures from the silicon; and
forming a third dielectric on each charge storage structure.
9. The method of claim 8 , further comprising forming a metal gate on each third dielectric.
10. The method of claim 8 , wherein the opening has a substantially square, oval, or circular geometry.
11. The method of claim 8 , wherein forming silicon comprises forming a silicon film about 3 to about 15 nanometers thick in the vertical opening.
12. The method of claim 8 , wherein:
forming a second dielectric comprises forming silicon dioxide or silicon nitride; and
forming a third dielectric comprises forming one or more of silicon dioxide and silicon nitride.
13. The method of claim 8 , wherein forming silicon in the vertical opening comprises forming silicon in a U-shaped pipe, wherein a portion of the U-shaped pipe comprises the vertical opening.
14. A method comprising:
forming an opening in a semiconductor construction, the semiconductor construction comprising alternating tiers of undoped polysilicon and a dielectric;
adding dopant to respective portions of the tiers of undoped polysilicon that at least partially surround the opening;
removing substantially all of the remaining undoped polysilicon of the tiers; and
forming dielectrics on opposing surfaces of each of the portions of doped polysilicon.
15. The method of claim 14 , further comprising forming a silicon film in the opening.
16. The method of claim 14 , further comprising forming a conductive gate adjacent to each of the portions of doped polysilicon.
17. The method of claim 14 , wherein adding dopant comprises adding p-type dopant through the opening to portions of polysilicon exposed by the opening.
18. The method of claim 14 , wherein removing substantially all of the remaining undoped polysilicon of the tiers comprises leaving a plurality of charge storage structures at least partially surrounding the opening.
19. The method of claim 18 , wherein leaving the plurality charge storage structures comprises leaving a plurality of p-type polysilicon charge storage structures.
20. The method of claim 14 , further comprising forming a metal gate adjacent to each of the portions of doped polysilicon.