Flash memory cell arrays having dual control gates per memory cell charge storage element

• US 7,502,261 B2
• Filed: 04/17/2006
• Issued: 03/10/2009
• Est. Priority Date: 10/28/2002
• Status: Expired due to Term

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Harari, Eliyahou
• Primary Examiner(s): Nguyen; Viet Q
• Application Number:
  US11/379,004
• Publication Number:
  US 20060176736A1
• Time in Patent Office: 1,058 Days
• Field of Search: 365/185.17, 365/185.05, 365/185.11, 365/63, 365/185.26
• US Class Current: 365/185.17
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: H01L 29/40114 the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
• CPC Class Codes: H01L 29/42348 with trapping site formed by at least two separated sites, e.g. multi-particles trapping site
• CPC Class Codes: H01L 29/66825 with a floating gate H01L29/6684 takes precedence
• CPC Class Codes: H01L 29/7881 Programmable transistors with only two possible levels of programmation H01L29/7888 takes precedence
• CPC Class Codes: H10B 41/30 characterised by the memory core region
• CPC Class Codes: H10B 41/35 with a cell select transistor, e.g. NAND
• CPC Class Codes: H10B 69/00 Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices

Abstract

A flash NAND type EEPROM system with individual ones of an array of charge storage elements, such as floating gates, being capacitively coupled with at least two control gate lines. The control gate lines are preferably positioned between floating gates to be coupled with sidewalls of floating gates. The memory cell coupling ratio is desirably increased, as a result. Both control gate lines on opposite sides of a selected row of floating gates are usually raised to the same voltage while the second control gate lines coupled to unselected rows of floating gates immediately adjacent and on opposite sides of the selected row are kept low. The control gate lines can also be capacitively coupled with the substrate in order to selectively raise its voltage in the region of selected floating gates. The length of the floating gates and the thicknesses of the control gate lines can be made less than the minimum resolution element of the process by forming an etch mask of spacers.

Claims

1. A non-volatile memory for programming and reading data, comprising:

a plurality of charge storage elements arranged in rows and columns across a semiconductor substrate,

a plurality of control gate lines extending across the charge storage elements in a manner that opposing sidewalls on opposite sides of individual charge storage elements are capacitively coupled with at least two of the control gate lines, and

a decoder and voltage supply connected to the control gate lines to couple controlled voltages to the charge storage elements capacitively coupled therewith during programming data thereto and reading data therefrom.

2. The memory of claim 1, wherein the control gate lines are additionally capacitively coupled with the substrate in areas between charge storage elements.

3. The memory of claim 2, additionally comprising trenches formed in the substrate between the charge storage elements in the path of the control lines, the control gate lines extending into said trenches with a dielectric layer between the control lines and the substrate.

4. The memory of claim 1, wherein the memory cells are oriented in a plurality of series connected strings of memory cells, and wherein the control gates extend across multiple strings of memory cells between the charge storage elements.

5. The memory of claim 4, additionally comprising dielectric filled isolation trenches in the substrate between the plurality of strings of memory cells.

12. The memory of claim 1, wherein the charge storage elements are conductive floating gates.

6. A non-volatile memory for programming and reading data, comprising:

an array of charge storage elements positioned across a semiconductor substrate,

a plurality of control gate lines extending across the array in a manner that opposing sidewalls of individual charge storage elements are capactively coupled with at least two of the control gate lines, and

a decoder and voltage supply connected to the control gate lines to couple controlled voltages to the charge storage elements capactively coupled therewith during programming data thereto and reading data therefrom,

wherein the memory cells are oriented in a plurality of series connected strings of memory cells, and wherein the control gates extend across multiple strings of memory cells between the charge storage elements, and

wherein the control gates include a combination of doped polysilicon as a bottom portion of a height of the control gates and a metal or silicide material in contact therewith as a top portion of the height of the control gates.

7. A non-volatile memory for programming and reading data, comprising:

a plurality of charge storage elements positioned across a semiconductor substrate with rows of the charge storage elements extending in a first direction and columns of charge storage elements extending in a second direction, the first and second directions being perpendicular with each other,

a plurality of control gate lines extending across the plurality of charge storage elements in the first direction and being spaced apart in the second direction between adjacent rows of charge storage elements in a manner that opposing sidewalls on opposite sides of individual charge storage elements of the rows are capacitively coupled with at least two control gate lines on opposite sides of the charge storage elements, and

a decoder and voltage supply connected to the control gate lines to couple controlled voltages to the charge storage elements capacitively coupled therewith during programming data thereto and reading data therefrom.

8. The memory of claim 7, wherein

the control gate lines are additionally capacitively coupled with the substrate in regions thereof between the charge storage elements in the second direction, and

the decoder and voltage supply additionally provides voltages to the control gate lines for controlling a level of conduction in the substrate regions between the charge storage elements in the second direction.

9. The memory of claim 7, wherein the decoder and voltage supply provides different voltages to various of the control gate lines at one time.

10. The memory of claim 7, wherein ends of the columns are controllably connected with voltage supply levels.

11. The memory of claim 8, wherein ends of the columns are controllably connected with voltage supply levels.

13. The memory of claim 7, wherein the charge storage elements are conductive floating gates.