Four-bit FinFET NVRAM memory device

• US 7,091,551 B1
• Filed: 04/13/2005
• Issued: 08/15/2006
• Est. Priority Date: 04/13/2005
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Nowak, Edward J., Clark, William F. Jr., Anderson, Brent A.
• Primary Examiner(s): Booth, Richard A.
• Application Number:
  US10/907,712
• Time in Patent Office: 489 Days
• Field of Search: 257/324, 438257-267, 438/283
• US Class Current: 257/324
• CPC Class Codes: G11C 16/0475 comprising two or more independent storage sites which store independent data
• CPC Class Codes: H01L 29/66795 with a horizontal current flow in a vertical sidewall of a semiconductor body, e.g. FinFET, MuGFET
• CPC Class Codes: H01L 29/785 having a channel with a horizontal current flow in a vertical sidewall of a semiconductor body, e.g. FinFET, MuGFET
• CPC Class Codes: H01L 29/7887 Programmable transistors with more than two possible different levels of programmation
• CPC Class Codes: H10B 41/30 characterised by the memory core region
• 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
• CPC Class Codes: Y10S 438/954 Making oxide-nitride-oxide device

Abstract

A four-bit FinFET memory cell, method of fabricating four-bit FinFET memory cell and an NVRAM formed of four-bit FINFET memory cells. The four-bit memory cell including two charge storage regions in opposite ends of a dielectric layer on a first sidewall of a fin of a FinFET and two additional charge storage regions in opposite ends of a dielectric layer on a second sidewall of the fin of the FinFET, the first and second sidewalls being opposite one another.

Claims

1. A semiconductor device, comprising:

a fin body having opposite first and second ends and opposite first and second sidewalls, said first and second sidewalls disposed between said first and second ends;

a first gate dielectric stack disposed on said first sidewall and a second gate dielectric stack disposed on said second sidewall, said first and second stacks each comprising at least a first, a second and a third dielectric layer, said first dielectric layer of said first dielectric stack in direct physical contact with said first sidewall and said first dielectric layer of said second dielectric stack in direct physical contact with said second sidewall;

a first gate electrode in direct physical contact with said third dielectric layer of said first gate dielectric stack and a second gate electrode in direct physical contact with said third dielectric layer of said second gate dielectric stack, said first and second gate electrodes not in direct physical contact with each other;

a first source/drain in said first end of said fin body and a second source/drain in said second end of said fin body; and

a channel region in said fin body between said first and second source/drains and aligned between said first and second gate electrodes.

2. The semiconductor device of claim 1, wherein:

said second dielectric layers of said first and said second gate dielectric stacks are a same second layer; and

said third dielectric layers of said first and said second gate dielectric stacks are a same third layer.

3. The semiconductor device of claim 1, wherein:

said first dielectric layers of said first and said second gate dielectric stacks are a same first layer.

4. The semiconductor device of claim 1, wherein said first dielectric layers of said first and second gate stacks comprise silicon dioxide, said second dielectric layers of said first and second gate stacks comprise silicon nitride, and said third dielectric layers of said first and second gate stacks comprise silicon dioxide.

5. The semiconductor device of claim 1, wherein said first dielectric layers of said first and second gate stacks comprise a material selected from the group consisting of metal oxides, Ta₂O₅, BaTiO₃, HfO₂, ZrO₂, Al₂O₃, metal silicates, HfSi_xO_y, HfSi_xO_yN_z, silicon dioxide and combinations thereof.

6. The semiconductor device of claim 1, wherein said channel region of said fin body is intrinsic or doped P-type and said first and second source/drains are doped N-type.

7. The semiconductor device of claim 6, wherein said first and second gate electrodes are intrinsic or doped N-type.

8. The semiconductor device of claim 1, wherein said channel region of said fin body is intrinsic or doped N-type and said first and second source/drains are doped P-type.

9. The semiconductor device of claim 8, wherein said first and second gate electrodes are intrinsic or doped P-type.

10. The semiconductor device of claim 1, wherein said first and second gate electrodes comprise polysilicon.

11. The semiconductor device of claim 1, wherein said fin body comprises single-crystal silicon.

12. The semiconductor device of claim 1, further including:

a first charge storage region of said second dielectric layer of said first gate dielectric stack disposed adjacent to both said first gate electrode and said first source/drain;

a second charge storage region of said second dielectric layer of said first gate dielectric stack disposed adjacent to both said first gate electrode and said second source/drain;

a third charge storage region of said second dielectric layer of said second gate dielectric stack disposed adjacent to both said second gate electrode and said first source/drain; and

a fourth charge storage region of said second dielectric layer of said second gate dielectric stack disposed adjacent to both said second gate electrode and said second source/drain.

13. The semiconductor device of claim 1, wherein said first and second gate electrodes are connected to wordlines of an NVRAM memory cell and said first and second source/drains are connected to bitlines of said NVRAM memory cell.

14. An NVRAM memory, comprising:

an array of four-bit memory cells arranged in rows and columns, each 4-bit memory cell comprising;

a fin body having opposite first and second ends and opposite first and second sidewalls, said first and second sidewalls disposed between said first and second ends;

a first gate dielectric stack disposed on said first sidewall and a second gate dielectric stack disposed on said second sidewall, said first and second stacks each comprising at least a first, a second and a third dielectric layer, said first dielectric layer of said first dielectric stack in direct physical contact with said first sidewall and said first dielectric layer of said second dielectric stack in direct physical contact with said second sidewall;

a first gate electrode in direct physical contact with said third dielectric layer of said first gate dielectric stack and a second gate electrode in direct physical contact with said third dielectric layer of said second gate dielectric stack, said first and second gate electrodes not in direct physical contact with each other;

a first source/drain in said first end of said fin body and a second source/drain in said second end of said fin body; and

a channel region in said fin body between said first and second source/drains and aligned between said first and second gate electrodes;

a first wordline connected to each first gate electrode and a second wordline connected to each second gate electrode of each four-bit memory cell in a same row of four-bit memory cells of said array of four-bit memory cells; and

a first bitline connected to each first source/drain and a second bitline connected to each second source/drain of each four-bit memory cell in a same column of four-bit memory cells of said array of four-bit memory cells.

15. The NVRAM memory of claim 14, further including:

a first charge storage region of said second dielectric layer of said first gate dielectric stack disposed adjacent to both said first gate electrode and said first source/drain;

a second charge storage region of said second dielectric layer of said first gate dielectric stack disposed adjacent to both said first gate electrode and said second source/drain;

a third charge storage region of said second dielectric layer of said second gate dielectric stack disposed adjacent to both said second gate electrode and said first source/drain; and

a fourth charge storage region of said second dielectric layer of said second gate dielectric stack disposed adjacent to both said second gate electrode and said second source/drain.

16. The NVRAM memory of claim 14, wherein a second source/drain of a first four-bit memory cell of said array of four-bit memory cells is connected to a same bitline as a first source/drain of a second four-bit memory cell of said array of four-bit memory cells.

17. The NVRAM of claim 16, wherein said second source/drain of said first four-bit memory cell of said array of four-bit memory cells and said second four-bit memory cell of said array of four-bit memory cells are in adjacent columns of said array of four-bit memory cells.

18. The NVRAM memory of claim 14, wherein said first four-bit memory cell of said array of four-bit memory cells and said second four-bit memory cell of said array of four-bit memory cells are connected to a pair of adjacent wordlines.

19. The NVRAM memory of claim 14, wherein said each channel region of each fin body of each four-bit memory cell of said array of four-bit memory cells is intrinsic or doped P-type and each first source/drain and each second source/drain of each four-bit memory cell of said array of four-bit memory cells are doped N-type.

20. The NVRAM memory of claim 14, wherein said each channel region of each fin body of each four-bit memory cell of said array of four-bit memory cells is intrinsic or doped N-type and each first source/drain and each second source/drain of each four-bit memory cell of said array of four-bit memory cells are doped P-type.

21. The NVRAM memory of claim 14, wherein each first gate and each second gate electrode of each fin body of each four-bit memory cell of said array of four-bit memory cells comprise polysilicon.

22. The NVRAM memory of claim 14, wherein each fin body of each fin body of each four-bit memory cell of said array of four-bit memory cells comprise single-crystal silicon.