Vertical thin-channel memory

• US 9,698,156 B2
• Filed: 03/03/2015
• Issued: 07/04/2017
• Est. Priority Date: 03/03/2015
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lue, Hang-Ting
• Primary Examiner(s): ALROBAIE, KHAMDAN N
• Application Number:
  US14/637,187
• Publication Number:
  US 20160260732A1
• Time in Patent Office: 854 Days
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/511 with a compositional variation, e.g. multilayer structures H01L29/516 takes precedence
• CPC Class Codes: H01L 29/66742 Thin film unipolar transistors
• CPC Class Codes: H01L 29/786 Thin film transistors, i.e. transistors with a channel being at least partly a thin film transistors having only the source or the drain region on an insulator layer H01L29/0653; thin film FinFETs H01L29/785
• CPC Class Codes: H10B 43/10 characterised by the top-view layout
• CPC Class Codes: H10B 43/27 the channels comprising vertical portions, e.g. U-shaped channels
• CPC Class Codes: H10B 43/35 with cell select transistors, e.g. NAND

Abstract

A memory device which can be configured as a 3D NAND flash memory, includes a plurality of stacks of conductive strips, including even stacks and odd stacks having sidewalls. Some of the conductive strips in the stacks are configured as word lines. Data storage structures are disposed on the sidewalls of the even and odd stacks. Active pillars between corresponding even and odd stacks of conductive strips include even and odd semiconductor films having outside surfaces and inside surfaces, the outside surfaces disposed on the data storage structures on the sidewalls of the corresponding even and odd stacks in the plurality of stacks forming a 3D array of memory cells, the inside surfaces are separated by an insulating structure that can include a gap. The semiconductor films can be thin-films.

Claims

1. A memory device, comprising:

first and second stacks of conductive strips having sidewalls;

data storage structures on the sidewalls of the conductive strips in the first and second stacks, and on top surfaces of the first and second stacks;

first and second vertical thin channel films having outside surfaces and inside surfaces, the outside surfaces disposed on the data storage structures on the sidewalls of the first and second stacks;

first memory cells at cross-points between the outside surfaces of the first vertical thin channel films and the conductive strips in the first stacks of conductive strips, and second memory cells at cross-points between the outside surfaces of the second vertical thin channel films and the conductive strips in the second stacks of conductive strips;

a reference conductor below the first and second stacks, and wherein the first and second vertical thin channel films are in physical contact with the reference conductor; and

insulating structures isolating the first vertical thin channel films of adjacent first memory cells along the conductive strips in the first stack of conductive strips, and isolating the second vertical thin channel films of adjacent second memory cells along the conductive strips in the second stack of conductive strips.

2. The memory device of claim 1, including a solid dielectric material between the inside surfaces of the first and second vertical thin channel films.

3. The memory device of claim 1, including a gap between the inside surfaces of the first and second vertical channel films.

4. The memory device of claim 1, wherein the data storage structure comprises a multilayer dielectric charge trapping structure.

5. The memory device of claim 1, including a conductive element connecting the first and second vertical thin channel films at upper ends, a bit line over the first and second stacks, and an interlayer connector connecting the bit line to the conductive element.

6. The memory device of claim 1, wherein the vertical thin channel films have a width, and the data storage structures include dielectric charge storage layers having a width that is less than the width of the vertical thin channel films.

7. A memory device including a plurality of memory cells, comprising:

a plurality of stacks of conductive strips, the plurality including adjacent first and second stacks, the first stack having a first side and a second side and the second stack having a first side opposed to the second side of the first stack, and a second side;

data storage structures on sidewalls of the conductive strips on the first and second sides of the stacks, and on top surfaces of the first and second stacks;

a first thin-film semiconductor strip disposed vertically in contact with the data storage structure on the first side of the first stack;

a second thin-film semiconductor strip disposed vertically in contact with the data storage structures on the second side of the first stack;

a third thin-film semiconductor strip disposed vertically in contact with the data storage structure on the first side of the second stack;

a fourth thin-film semiconductor strip disposed vertically in contact with the data storage structures on the second side of the second stack;

the memory cells in the plurality of memory cells having channels in the thin-film semiconductor strips and gates in the conductive strips;

a patterned conductor layer or layers over the plurality of stacks;

a first interlayer connector connecting a first conductor in the patterned conductor layer or layers to a top surface of the first thin-film semiconductor strip;

a second interlayer connector connecting a second conductor in the patterned conductor layer or layers to a top surface of the second and third thin-film semiconductor strips;

a reference conductor below the plurality of stacks, and wherein the second thin-film semiconductor strip and the third thin-film semiconductor strip are physically connected to the reference conductor between the adjacent first and second stacks; and

a third interlayer connector connecting a third conductor in the patterned conductor layer or layers to a top surface of the fourth thin-film semiconductor strip.

8. The memory device of claim 7, including a gap between the second and third thin-film semiconductor strips.

9. The memory device of claim 8, including insulating layers on the second thin-film semiconductor strip and on the third thin-film semiconductor strip, the insulating layers being separated by said gap.

10. A memory device, comprising:

a plurality of stacks of conductive strips having sidewalls, the plurality of stacks including even stacks and odd stacks;

data storage structures on the sidewalls of the conductive strips in the plurality of stacks including the even and odd stacks, and on top surfaces of the plurality of stacks including the even and odd stacks;

a plurality of active pillars arranged between corresponding even and odd stacks of conductive strips in the plurality of stacks, active pillars in the plurality comprising even and odd vertical thin channel films having outside surfaces and inside surfaces, defining a multi-layer array of interface regions at cross-points between outside surfaces of the even and odd vertical thin channel films and conductive strips in the corresponding even and odd stacks of conductive strips;

a 3D array of even memory cells in the interface regions accessible via the active pillars and conductive strips in the even stacks of conductive strips and odd memory cells in the interface regions accessible via the active pillars and conductive strips in the odd stacks of conductive strips, wherein the odd memory cells on a given active pillar are configured as a first NAND string, and the even memory cells on said given active pillar are configured as a second NAND string, and wherein the inside surfaces of the even and odd vertical thin channel films of said given active pillar are separated in the interface regions;

insulating structures isolating the even vertical thin channel films of adjacent even memory cells along the conductive strips in the even stacks, and isolating the odd vertical thin channel films of adjacent odd memory cells along the conductive strips in the odd stacks;

conductive strips in an upper level in the even and odd stacks being configured as string select lines for both the first and second NAND strings on a given active pillar;

conductive strips in intermediate levels in the even and odd stacks being configured as word lines for respective ones of the first and second NAND strings on a given active pillar;

conductive strips in a lower level in the even and odd stacks being configured as ground select lines for both the first and second NAND strings on a given active pillar;

a reference conductor beneath and physically connected to active pillars in the plurality of active pillars; and

control circuitry configured to apply different bias voltages to the even and odd conductive strips.

11. The memory device of claim 10, wherein active pillars in the plurality of active pillars include a dielectric material separating the even and odd vertical thin channel films.

12. The memory device of claim 10, wherein active pillars in the plurality of active pillars include a gap separating the even and odd vertical thin channel films.

13. The memory device of claim 10, wherein the plurality of stacks of conductive strips are arranged in blocks, and in a given block, conductive strips in a given layer of an odd stack are configured in a comb-like structure with strips extending from an odd pad, and conductive strips in the given layer of an even stack are configured in a comb-like structure with strips extending from an even pad, the conductive strips extending from the odd and even pads in the given block being interdigitated.

14. The memory device of claim 10, wherein the memory cells comprise dielectric charge storage structures.

15. The memory device of claim 10, including one or more patterned conductor layers over the plurality of stacks, including bit lines, and interlayer connectors connecting the bit lines to corresponding active pillars.

16. The memory device of claim 10, including a patterned conductor disposed beside the plurality of stacks, and connected to the reference conductor.

17. A manufacturing method, comprising:

forming a reference conductor on a substrate;

forming over the reference conductor, first and second stacks of conductive strips having side walls;

forming data storage structures on the sidewalls of the first and second stacks, and on top surfaces of the first and second stacks;

forming first and second opposing vertical thin channel films on the data storage structures on the sidewalls of the first and second stacks, and in physical contact with the reference conductor; and

forming a bit line over the first and second stacks, in electrical contact with the first and second opposing vertical thin channel films.

18. The method of claim 17, including leaving a gap between the first and second vertical thin channel films.

19. The method of claim 17, including forming a conductive element connecting the first and second vertical thin channel films at upper ends, forming a contact plug on the conductive element, the bit line being in electrical communication with the contact plug.

20. The method of claim 17, wherein forming the reference conductor comprises forming a layer of semiconductor material below the first and second stacks.

21. The method of claim 17, wherein forming the first and second stacks includes:

forming a plurality of layers of conductive material separated by layers of insulating material; and

etching trenches in the plurality of layers to define the first and second stacks.

22. The method of claim 21, wherein forming the vertical thin channel films includes:

depositing a layer of semiconductor material over the first and second stacks having a thickness 10 nanometers or less on the sides of the conductive strips in the stacks; and

etching a pattern in the layer of semiconductor material to define the first and second vertical thin channel films.

23. The method of claim 21, wherein forming the data storage structures includes forming a plurality of layers of dielectric material over the sidewalls of the first and second stacks.