U.S. patent application number 16/986610 was filed with the patent office on 2022-02-10 for storage node after three-node access device formation for vertical three dimensional (3d) memory.
The applicant listed for this patent is Micron Technology, Inc.. Invention is credited to Si-Woo Lee, Armin Saeedi Vahdat, Gurtej S. Sandhu, Scott E. Sills, John A. Smythe III.
Application Number | 20220045062 16/986610 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-10 |
United States Patent
Application |
20220045062 |
Kind Code |
A1 |
Saeedi Vahdat; Armin ; et
al. |
February 10, 2022 |
STORAGE NODE AFTER THREE-NODE ACCESS DEVICE FORMATION FOR VERTICAL
THREE DIMENSIONAL (3D) MEMORY
Abstract
Systems, methods and apparatus are provided for storage node
after horizontally oriented, three-node access device formation in
vertical three dimensional (3D) memory. An example method includes
a method for forming arrays of vertically stacked memory cells,
having horizontally oriented access devices and vertically oriented
access lines. The method includes depositing alternating layers of
a dielectric material and a sacrificial material to form a vertical
stack. A plurality of first vertical openings are formed through
the vertical stack to form elongated vertical, pillar columns with
sidewalls in the vertical stack. A first conductive material is
conformally deposited on a gate dielectric material in the first
vertical openings. Portions of the first conductive material are
removed to form a plurality of separate, vertical access lines
along the sidewalls of the elongated vertical, pillar columns. A
second vertical opening is formed through the vertical stack to
expose a first region of the sacrificial material. The first region
is selectively removed to form a first horizontal opening in which
to form a first source/drain material, a channel material, and a
second source/drain material of the three-node access device. A
third vertical opening is formed through the vertical stack to
expose a second region of the sacrificial material. The second
region is selectively removed after formation of the three-node
access device in the first region to form a second horizontal
opening in which to form a storage node electrically coupled to the
first source/drain material.
Inventors: |
Saeedi Vahdat; Armin;
(Boise, ID) ; Smythe III; John A.; (Boise, ID)
; Lee; Si-Woo; (Boise, ID) ; Sandhu; Gurtej
S.; (Boise, ID) ; Sills; Scott E.; (Boise,
ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Micron Technology, Inc. |
Boise |
ID |
US |
|
|
Appl. No.: |
16/986610 |
Filed: |
August 6, 2020 |
International
Class: |
H01L 27/108 20060101
H01L027/108; H01L 29/06 20060101 H01L029/06; H01L 29/24 20060101
H01L029/24; H01L 29/423 20060101 H01L029/423; H01L 29/786 20060101
H01L029/786; H01L 21/02 20060101 H01L021/02; H01L 29/66 20060101
H01L029/66 |
Claims
1. A method for forming arrays of vertically stacked memory cells,
having horizontally oriented access devices and vertically oriented
access lines, comprising: depositing alternating layers of a
dielectric material and a sacrificial material to form a vertical
stack; forming a plurality of first vertical openings, having a
first horizontal direction and a second horizontal direction,
through the vertical stack and extending predominantly in the
second horizontal direction to form elongated vertical, pillar
columns with sidewalls in the vertical stack; conformally
depositing first conductive material on a gate dielectric material
in the first vertical openings; removing portions of the first
conductive material to form a plurality of separate, vertical
access lines along the sidewalls of the elongated vertical, pillar
columns; forming a second vertical opening through the vertical
stack, extending predominantly in the first horizontal direction,
to expose a first region of the sacrificial material; selectively
removing the first region to form a first horizontal opening in the
sacrificial material in which to form a first source/drain
material, a channel material, and a second source/drain material of
a horizontally oriented three-node access device; forming a third
vertical opening through the vertical stack, extending
predominantly in the first horizontal direction, to expose a second
region of the sacrificial material; selectively removing the second
region to form a second horizontal opening in the sacrificial
material in which to form a storage node electrically coupled to
the first source/drain material after formation of the three-node
access device in the first region.
2. The method of claim 1, further comprising: selectively removing
the first region in the first horizontal distance from the second
vertical opening; and using an atomic layer deposition (ALD)
process to sequentially deposit: the first source/drain material;
the channel material; and the second source/drain material of the
three-node access device before selectively removing the second
region.
3. The method of claim 1, further comprising depositing a
multilayer source/drain material in the first horizontal opening to
form electrical contact with the storage node at a distal end of
the first horizontal opening from the second vertical opening.
4. The method of claim 1, further comprising depositing a first
conductive metal material that does not oxidize in contact with an
oxide semiconductor channel material as part of the first
source/drain material.
5. The method of claim 4, wherein depositing the first conductive
metal material comprises depositing a material containing ruthenium
(Ru).
6. The method of claim 1, further comprising depositing the first
conductive material which comprises a metal material that forms a
conductive oxide in contact with an oxide semiconductor channel
material as part of the first source/drain material.
7. The method of claim 6, wherein depositing the first conductive
material comprises depositing an indium tin oxide (InSnO.sub.x)
material.
8. The method of claim 1, further comprising; selectively removing
the second region in a second horizontal distance from the third
vertical opening to reach a first metal conductive material after
forming the three-node access device; and performing a selective
etch that is selective to etching a sacrificial oxide semiconductor
material and selective to not etching the first metal conductive
material to remove the second region.
9. The method of claim 8, further comprising selectively
depositing, in the second horizontal opening: a first electrode in
ohmic contact with the first metal conductive material; a cell
dielectric on the first electrode; and a second electrode on the
cell dielectric to form a capacitor cell as the storage node in the
second horizontal opening.
10. The method of claim 1, further comprising integrating a
horizontally oriented digit line to form electrical contact with
the second source/drain material.
11. A method for forming arrays of vertically stacked memory cells,
having horizontally oriented access devices and vertically oriented
access lines, comprising: depositing alternating layers of a
dielectric material and a sacrificial material to form a vertical
stack; forming a plurality of first vertical openings, having a
first horizontal direction and a second horizontal direction,
through the vertical stack and extending predominantly in the
second horizontal direction to form elongated vertical, pillar
columns with sidewalls in the vertical stack; conformally
depositing first conductive material on a gate dielectric material
in the first vertical openings; removing portions of the first
conductive material to form a plurality of separate, vertical
access lines along the sidewalls of the elongated vertical, pillar
columns; forming a second vertical opening through the vertical
stack and extending predominantly in the first horizontal direction
to expose a first region of the sacrificial material; selectively
removing the first region to form a first horizontal opening in the
sacrificial material extending a first distance from the second
vertical opening; using an atomic layer deposition (ALD) process to
sequentially deposit a first source/drain material, a channel
material, and a second source/drain material in the first
horizontal opening to form a horizontally oriented three-node
access device without a body contact; forming a third vertical
opening through the vertical stack and extending predominantly in
the first horizontal direction to expose a second region of the
sacrificial material; selectively removing the second region to
form a second horizontal opening in the sacrificial material
extending a second distance from the second vertical opening; and
using an atomic layer deposition (ALD) process to sequentially
deposit: a first electrode electrically forming electrical contact
with the first source/drain material; a high-k dielectric material
on the first electrode; and a second electrode on the high-k
dielectric subsequent to formation of the horizontally oriented
three-node access device.
12. The method of claim 11, further comprising depositing a metal
source/drain material that does not oxidize in contact with an
oxide semiconductor channel material.
13. The method of claim 11, further comprising depositing a metal
source/drain material that forms a conductive oxide in contact with
an oxide semiconductor channel material.
14. The method of claim 11, further comprising depositing an oxide
semiconductor material as the channel material.
15. The method of claim 11, further comprising depositing a
two-dimensional (2D) material comprising one or more of a
transition metal dichalcogenide as the channel material.
16. The method of claim 11, further comprising depositing a
degenerate semiconductor material as the first source/drain
material.
17. The method of claim 11, further comprising depositing a
multilayer first source/drain material having a first semiconductor
material and a second semiconductor material, wherein the second
semiconductor material has an electronic bandgap between an
electronic band gap of the first semiconductor material and an
electronic bandgap of the channel material.
18. The method of claim 11, further comprising using the first
source/drain material as an etch stop material while performing
selective etch to remove the second region.
19. A method for forming arrays of vertically stacked memory cells,
having horizontally oriented access devices and vertically oriented
access lines, comprising: depositing alternating layers of a
dielectric material and a sacrificial material to form a vertical
stack; forming a plurality of first vertical openings, having a
first horizontal direction and a second horizontal direction,
through the vertical stack and extending predominantly in the
second horizontal direction to form elongated vertical, pillar
columns with sidewalls in the vertical stack; conformally
depositing first conductive material on a gate dielectric material
in the first vertical openings; removing portions of the first
conductive material to form a plurality of separate, vertical
access lines along the sidewalls of the elongated vertical, pillar
columns; forming a second vertical opening through the vertical
stack and extending predominantly in the first horizontal direction
to expose first sidewalls adjacent a first region of the
sacrificial material; selectively removing the first region to form
a first horizontal opening in the sacrificial material;
sequentially forming a first source/drain material, a channel
material, and a second source/drain material in the first
horizontal opening to form a horizontally oriented access device
without a body contact, wherein the first source/drain material is
selected to provide ohmic contact to a first electrode of a storage
node; forming a third vertical opening through the vertical stack
and extending predominantly in the first horizontal direction to
expose second sidewalls adjacent a second region of the sacrificial
material; selectively removing the second region to form a second
horizontal opening in the sacrificial material extending to the
first source/drain material, using the first source/drain material
as an etch stop, after formation of the horizontally oriented
access device; and selectively depositing the first electrode of
the storage node on the first source/drain material in the second
horizontal opening to form direct electrical contact therewith.
20. The method of claim 19, further comprising selectively
depositing: a high-k dielectric material on the first electrode;
and a second electrode on the high-k dielectric to form a
horizontally oriented capacitor cell as the storage node after
formation of the horizontally oriented access device.
21. The method of claim 19, further comprising forming a multilayer
first source/drain material in electrical contact with the first
electrode of the storage node.
22. The method of claim 19, further comprising depositing a metal
first source/drain material that does not oxidize in contact with
an oxide semiconductor channel material prior to formation of the
second horizontal opening.
23. The method of claim 19, further comprising depositing a metal
first source/drain material that forms a conductive oxide in
contact with an oxide semiconductor channel material prior to
formation of the second horizontal opening.
24. The method of claim 19, further comprising integrating a
horizontally oriented digit line to form electrical contact with
the second source/drain material.
25. The method of claim 19, further comprising forming a
horizontally oriented digit line in electrical contact with the
second source/drain material such that the horizontally oriented
digit line is on a same plane, level with, the second source/drain
material in the vertical stack.
26. The method of claim 19, further comprising forming a
horizontally oriented storage node having the first electrode such
that the horizontally oriented storage node is on a same plane,
level with, the first source/drain material in the vertical stack.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to memory devices,
and more particularly, to storage node after three-node access
device formation and structure for vertical three dimensional (3D)
memory.
BACKGROUND
[0002] Memory is often implemented in electronic systems, such as
computers, cell phones, hand-held devices, etc. There are many
different types of memory, including volatile and non-volatile
memory. Volatile memory may require power to maintain its data and
may include random-access memory (RAM), dynamic random-access
memory (DRAM), static random-access memory (SRAM), and synchronous
dynamic random-access memory (SDRAM). Non-volatile memory may
provide persistent data by retaining stored data when not powered
and may include NAND flash memory, NOR flash memory, nitride read
only memory (NROM), phase-change memory (e.g., phase-change random
access memory), resistive memory (e.g., resistive random-access
memory), cross-point memory, ferroelectric random-access memory
(FeRAM), or the like.
[0003] As design rules shrink, less semiconductor space is
available to fabricate memory, including DRAM arrays. A respective
memory cell for DRAM may include an access device, e.g.,
transistor, having a first and a second source/drain regions
separated by a channel region. A gate may oppose the channel region
and be separated therefrom by a gate dielectric. An access line,
such as a word line, is electrically connected to the gate of the
DRAM cell. A DRAM cell can include a storage node, such as a
capacitor cell, coupled by the access device to a digit line. The
access device can be activated (e.g., to select the cell) by an
access line coupled to the access transistor. The capacitor can
store a charge corresponding to a data value of a respective cell
(e.g., a logic "1" or "0").
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic illustration of a vertical three
dimensional (3D) memory in accordance a number of embodiments of
the present disclosure.
[0005] FIG. 2 is a perspective view illustrating a portion of a
three-node access device in a vertical three dimensional (3D)
memory array in accordance with a number of embodiments of the
present disclosure.
[0006] FIG. 3 is a perspective view illustrating a portion of a
three-node access device in a vertical three dimensional (3D)
memory cell in accordance with a number of embodiments of the
present disclosure.
[0007] FIG. 4 illustrates an example method for forming arrays of
vertically stacked memory cells, at one stage of a semiconductor
fabrication process, to form three-node access devices in
accordance with a number of embodiments of the present
disclosure.
[0008] FIGS. 5A-5B illustrate an example method, at another stage
of a semiconductor fabrication process, for forming arrays of
vertically stacked memory cells, having three-node horizontally
oriented access devices and vertically oriented access lines, in
accordance with a number of embodiments of the present
disclosure.
[0009] FIGS. 6A to 6E illustrate an example method, at another
stage of a semiconductor fabrication process, for forming arrays of
vertically stacked memory cells, having three-node, horizontally
oriented access devices and vertically oriented access lines, in
accordance with a number of embodiments of the present
disclosure.
[0010] FIGS. 7A to 7E illustrate an example method, at another
stage of a semiconductor fabrication process, for forming arrays of
vertically stacked memory cells, having three-node, horizontally
oriented access devices and vertically oriented access lines, in
accordance with a number of embodiments of the present
disclosure.
[0011] FIGS. 8A to 8E illustrate an example method, at another
stage of a semiconductor fabrication process, for forming arrays of
vertically stacked memory cells, having three-node, horizontally
oriented access devices and vertically oriented access lines, in
accordance with a number of embodiments of the present
disclosure.
[0012] FIGS. 9A to 9E illustrate an example method, at another
stage of a semiconductor fabrication process, for forming arrays of
vertically stacked memory cells, having three-node, horizontally
oriented access devices and vertically oriented access lines, in
accordance with a number of embodiments of the present
disclosure.
[0013] FIG. 10 illustrates an example of a three-node horizontally
oriented access device coupled to a horizontally oriented storage
node and coupled to vertically oriented access lines and
horizontally oriented digit lines, in accordance with a number of
embodiments of the present disclosure.
[0014] FIG. 11 is a block diagram of an apparatus in the form of a
computing system including a memory device in accordance with a
number of embodiments of the present disclosure.
DETAILED DESCRIPTION
[0015] Embodiments of the present disclosure describe a three-node
access device for vertical three dimensional (3D) memory.
Three-node horizontal access devices are formed without body region
contacts. As used herein, three-node is intended to refer to an
access device comprising (1) a first source/drain region and (2) a
second source/drain region separated by a channel region, and (3)
one or more gates(s) opposing the channel region. The three-node
horizontal access devices are integrated with vertical access lines
and integrated with horizontal digit lines. According to
embodiments, the three-node horizontal access devices may be formed
such that the channel region has fewer, e.g., may operate free of,
minority carriers thus removing the need to control a body
potential to a body region of the access device. Advantages to the
structure and process described herein can include a lower
off-current (Ioff) for the access devices, as compared to silicon
based (Si-based) access devices, and/or reduced gate/drain induced
leakage (GIDL) for the access devices.
[0016] According to embodiments channel and/or source/drain region
replacement fabrication steps are performed before a capacitor cell
formation process. The digit line integration may be more easily
achieved in the fabrication process since a body contact to a body
region of the access device is not used. Additionally, the
embodiments described herein may achieve a better lateral scaling
path than achieved with doped polysilicon based channel regions due
to less channel length and lower source/drain semiconductor
fabrication process overhead. A further benefit is the avoidance,
e.g., no use of, gas phase doping (GPD) in the formation of the
source/drain regions.
[0017] The figures herein follow a numbering convention in which
the first digit or digits correspond to the figure number of the
drawing and the remaining digits identify an element or component
in the drawing. Similar elements or components between different
figures may be identified by the use of similar digits. For
example, reference numeral 104 may reference element "04" in FIG.
1, and a similar element may be referenced as 204 in FIG. 2.
Multiple analogous elements within one figure may be referenced
with a reference numeral followed by a hyphen and another numeral
or a letter. For example, 302-1 may reference element 302-1 in
FIGS. 3 and 302-2 may reference element 302-2, which may be
analogous to element 302-1. Such analogous elements may be
generally referenced without the hyphen and extra numeral or
letter. For example, elements 302-1 and 302-2 or other analogous
elements may be generally referenced as 302.
[0018] FIG. 1 is a block diagram of an apparatus in accordance a
number of embodiments of the present disclosure. FIG. 1 illustrates
a circuit diagram showing a cell array of a three dimensional (3D)
semiconductor memory device according to embodiments of the present
disclosure. FIG. 1 illustrates a cell array may have a plurality of
sub cell arrays 101-1, 101-2, . . . , 101-N. The sub cell arrays
101-1, 101-2, . . . , 101-N may be arranged along a second
direction (D2) 105. Each of the sub cell arrays, e.g., sub cell
array 101-2, may include a plurality of access lines 103-1, 103-2,
. . . , 103-Q (which also may be referred to a wordlines). Also,
each of the sub cell arrays, e.g., sub cell array 101-2, may
include a plurality of digit lines 107-1, 107-2, . . . , 107-P
(which also may be referred to as bitlines, data lines, or sense
lines). In FIG. 1, the digit lines 107-1, 107-2, . . . , 107-P are
illustrated extending in a first direction (D1) 109 and the access
lines 103-1, 103-2, . . . , 103-Q are illustrated extending in a
third, vertical direction (D3) 111. According to embodiments, the
first direction (D1) 109 and the second direction (D2) 105 may be
considered in a horizontal ("X-Y") plane. The third direction (D3)
111 may be considered in a vertical ("Z") plane. Hence, according
to embodiments described herein, the access lines 103-1, 103-2, . .
. , 103-Q are extending in a vertical direction, e.g., third
direction (D3) 111.
[0019] A memory cell, e.g., 110, may include an access device,
e.g., access transistor, and a storage node, e.g., capacitor,
located at an intersection of each access line 103-1, 103-2, . . .
, 103-Q and each digit line 107-1, 107-2, . . . , 107-P. Memory
cells may be written to, or read from, using the access lines
103-1, 103-2, . . . , 103-Q and digit lines 107-1, 107-2, . . . ,
107-P. The digit lines 107-1, 107-2, . . . , 107-P may conductively
interconnect memory cells along horizontal columns of each sub cell
array 101-, 101-2, . . . , 101-N, and the access lines 103-1,
103-2, . . . , 103-Q may conductively interconnect memory cells
along vertical rows of each sub cell array 101-, 101-2, . . . ,
101-N. One memory cell, e.g. 110, may be located between one access
line, e.g., 103-2, and one digit line, e.g., 107-2. Each memory
cell may be uniquely addressed through a combination of an access
line 103-1, 103-2, . . . , 103-Q and a digit line 107-1, 107-2, . .
. , 107-P.
[0020] The digit lines 107-1, 107-2, . . . , 107-P may be or
include conducting patterns (e.g., metal lines) disposed on and
spaced apart from a substrate. The digit lines 107-1, 107-2, . . .
, 107-P may extend in a first direction (D1) 109. The digit lines
107-1, 107-2, . . . , 107-P in one sub cell array, e.g., 101-2, may
be spaced apart from each other in a vertical direction, e.g., in a
third direction (D3) 111.
[0021] The access lines 103-1, 103-2, . . . , 103-Q may be or
include conductive patterns (e.g., metal lines) extending in a
vertical direction with respect to the substrate, e.g., in a third
direction (D3) 111. The access lines in one sub cell array, e.g.,
101-2, may be spaced apart from each other in the first direction
(D1) 109 by an insulating material.
[0022] A gate of a memory cell, e.g., memory cell 110, may be
connected to an access line, e.g., 103-2, and a first conductive
node, e.g., first source/drain region, of an access device, e.g.,
transistor, of the memory cell 110 may be connected to a digit
line, e.g., 107-2. Each of the memory cells, e.g., memory cell 110,
may be connected to a storage node, e.g., capacitor. A second
conductive node, e.g., second source/drain region, of the access
device, e.g, transistor, of the memory cell 110 may be connected to
the storage node, e.g., capacitor. While first and second
source/drain region reference are used herein to denote two
separate and distinct source/drain regions, it is not intended that
the source/drain region referred to as the "first" and/or "second"
source/drain regions have some unique meaning. It is intended only
that one of the source/drain regions is connected to a digit line,
e.g., 107-2, and the other may be connected to a storage node.
[0023] FIG. 2 illustrates a perspective view showing a three
dimensional (3D) semiconductor memory device, e.g., a portion of a
sub cell array 101-2 shown in FIG. 1 as a vertically oriented stack
of memory cells in an array, according to some embodiments of the
present disclosure. FIG. 3 illustrates a perspective view showing
unit cell, e.g., memory cell 110 shown in FIG. 1, of the 3D
semiconductor memory array shown in FIG. 2.
[0024] As shown in FIG. 2, a substrate 200 may have formed thereon
one of the plurality of sub cell arrays, e.g., 101-2, described in
connection with FIG. 1. For example, the substrate 200 may be or
include a silicon substrate, a germanium substrate, or a
silicon-germanium substrate, etc. Embodiments, however, are not
limited to these examples.
[0025] As shown in the example embodiment of FIG. 2, the substrate
200 may have fabricated thereon a vertically oriented stack of
memory cells, e.g., memory cell 110 in FIG. 1, extending in a
vertical direction, e.g., third direction (D3) 111. According to
some embodiments the vertically oriented stack of memory cells may
be fabricated such that each memory cell, e.g., memory cell 110 in
FIG. 1, is formed on plurality of vertical levels, e.g., a first
level (L1), a second level (L2), and a third level (L3) (also
referred to herein as "tiers"). The repeating, vertical levels, L1,
L2, and L3, may be arranged, e.g., "stacked", a vertical direction,
e.g., third direction (D3) 111 shown in FIG. 1. Each of the
repeating, vertical levels, L1, L2, and L3 may include a plurality
of discrete components, e.g., regions, to the horizontally oriented
access devices 230, e.g., transistors, and storage nodes, e.g.,
capacitors, including access line 103-1, 103-2, . . . , 103-Q
connections and digit line 107-1, 107-2, . . . , 107-P connections.
The plurality of discrete components to the horizontally oriented,
three-node access devices, e.g., transistors 110 in FIG. 1, may be
formed in a plurality of iterations of vertically, repeating layers
within each level, as described in more detail below in connection
with FIGS. 4 et. seq., and may extend horizontally in the second
direction (D2) 205, analogous to second direction (D2) 105 shown in
FIG. 1.
[0026] The plurality of discrete components to the horizontally
oriented three-node access devices 230, e.g., transistors, may
include a first source/drain region 221 and a second source/drain
region 223 separated by a channel region 225, extending in the
second direction (D2) 205. Three-node horizontal access devices 230
are formed without body region contacts. As used herein, three-node
is intended to refer to an access device comprising (1) a first
source/drain region 221 and (2) a second source/drain region 223
separated by a channel region 225, and (3) one or more gates(s),
e.g., vertical access lines, 203-1, 203-2, . . . , 203-Q, opposing
the channel region 225. In some embodiments, the channel region 225
may include silicon, germanium, silicon-germanium, and/or indium
gallium zinc oxide (IGZO). In some embodiments, the first and the
second source/drain regions, 221 and 223, can include an n-type
dopant region, e.g., semiconductor material, formed adjacent to a
p-type doped channel region, e.g., semiconductor material, of the
access device to form an n-type conductivity transistor. In some
embodiments, the first and the second source/drain regions, 221 and
223, may include a p-type conductivity, e.g., doped semiconductor
material, formed adjacent to an n-type conductivity channel region,
e.g., doped semiconductor material, of the access device to form a
p-type conductivity transistor. By way of example, and not by way
of limitation, the n-type dopant may include Phosphorous (P) atoms
and the p-type dopant may include atoms of Boron (B) formed in an
oppositely doped body region of polysilicon semiconductor material.
Embodiments, however, are not limited to these examples.
[0027] The storage node 227, e.g., capacitor, may be connected to
one respective end of the access device. As shown in the example of
FIG. 2, the storage node 227, e.g., capacitor may be connected to
the second source/drain region 223 of the access device. The second
source/drain region 223 could equally be labeled and referred to
herein as the first source/drain region. Again, the "first" and
"second" source/drain labels only intend that they are separate and
distinct, one connected to a digit line and the other to a storage
node. The storage node may be or include memory elements capable of
storing data. Each of the storage nodes may be a memory element
using one of a capacitor, a magnetic tunnel junction pattern,
and/or a variable resistance body which includes a phase change
material, etc. Embodiments, however, are not limited to these
examples. In some embodiments, the storage node associated with
each horizontally oriented access device of a unit cell, e.g.,
memory cell 110 in FIG. 1, may similarly extend in the second
direction (D2) 205, analogous to second direction (D2) 105 shown in
FIG. 1.
[0028] As shown in FIG. 2 a plurality of horizontally oriented
digit lines 207-1, 207-2, . . . , 207-P extend in the first
direction (D1) 209, analogous to the first direction (D1) 109 in
FIG. 1. The plurality of horizontally oriented digit lines 207-1,
207-2, . . . , 207-P may be analogous to the digit lines 107-1,
107-2, . . . , 107-P shown in FIG. 1. The plurality of horizontally
oriented digit lines 207-1, 207-2, . . . , 207-P may be arranged,
e.g., "stacked", along the third direction (D3) 211. The plurality
of horizontally oriented digit lines 207-1, 207-2, . . . , 207-P
may include a conductive material. For example, the conductive
material may include one or more of a doped semiconductor, e.g.,
doped silicon, doped germanium, etc., a conductive metal nitride,
e.g., titanium nitride, tantalum nitride, etc., a metal, e.g.,
tungsten (W), titanium (Ti), tantalum (Ta), etc., and/or a
metal-semiconductor compound, e.g., tungsten silicide, cobalt
silicide, titanium silicide, etc. Embodiments, however, are not
limited to these examples.
[0029] Among each of the vertical levels, 213-1 (L1), 213-2 (L2),
and 213-M (L3), the horizontally oriented memory cells, e.g.,
memory cell 110 in FIG. 1, may be spaced apart from one another
horizontally in the first direction (D1) 209. However, as described
in more detail below in connection with FIGS. 4 et. seq., the
plurality of discrete components to the horizontally oriented
access devices 230, e.g., first source/drain region 221 and second
source/drain region 223 separated by a channel region 225,
extending horizontally in the second direction (D2) 205, and the
plurality of horizontally oriented digit lines 207-1, 207-2, . . .
, 207-P extending horizontally in the first direction (D1) 209, may
be formed within a same plane, e.g., level with, and in a same
layer within each level. The plurality of horizontally oriented
digit lines 207-1, 207-2, . . . , 207-P, extending in the first
direction (D1) 209, may be in electrical contact with the first
source/drain regions 221 and orthogonal to the horizontally
oriented access devices 230, e.g., transistors, extending in
horizontally in the second direction (D2) 205.
[0030] In some embodiments, the plurality of horizontally oriented
digit lines 207-1, 207-2, . . . , 207-P, extending in the first
direction (D1) 209 are formed in a higher vertical layer, farther
from the substrate 200, within a level, e.g., within level (L1),
than a layer in which the discrete components, e.g., first
source/drain region 221 and second source/drain region 223
separated by a channel region 225, of the laterally oriented access
device are formed. In some embodiments, the plurality of
horizontally oriented digit lines 207-1, 207-2, . . . , 207-P,
extending in the first direction (D1) 209, may be connected to the
top surfaces of the first source/drain regions 221 directly and/or
through additional contacts including metal silicides.
[0031] As shown in the example embodiment of FIG. 2, the access
lines, 203-1, 203-2, . . . , 203-Q, extend in a vertical direction
with respect to the substrate 200, e.g., in a third direction (D3)
211. Further, as shown in FIG. 2, the access lines, 203-1, 203-2, .
. . , 203-Q, in one sub cell array, e.g., sub cell array 101-2 in
FIG. 1, may be spaced apart from each other in the first direction
(D1) 209. The access lines, 203-1, 203-2, . . . , 203-Q, may be
provided, extending vertically relative to the substrate 200 in the
third direction (D3) 211 between a pair of the horizontally
oriented, three-node access devices 230, e.g., transistors,
extending laterally in the second direction (D2) 205, but adjacent
to each other on a level, e.g., first level (L1), in the first
direction (D1) 209. Each of the access lines, 203-1, 203-2, . . . ,
203-Q, may vertically extend, in the third direction (D3), on
sidewalls of respective ones of the plurality of horizontally
oriented, three-node access devices 230, e.g., transistors, that
are vertically stacked separated from a channel region by a gate
dielectric.
[0032] For example, and as shown in more detail in FIG. 3, a first
one of the vertically extending access lines, e.g., 203-1, may be
adjacent a sidewall of a channel region 225 to a first one of the
horizontally oriented, three-node access devices 230, e.g.,
transistors, in the first level (L1) 213-1, a sidewall of a channel
region 225 of a first one of the horizontally oriented, three-node
access devices 230, e.g., transistors, in the second level (L2)
213-2, and a sidewall of a channel region 225 a first one of the
horizontally oriented, three-node access devices 230, e.g.,
transistors, in the third level (L3) 213-M, etc. Similarly, a
second one of the vertically extending access lines, e.g., 203-2,
may be adjacent a sidewall to a channel region 225 of a second one
of the horizontally oriented, three-node access devices 230, e.g.,
transistors, in the first level (L1) 213-1, spaced apart from the
first one of horizontally oriented, three-node access devices 230,
e.g., transistors, in the first level (L1) 213-1 in the first
direction (D1) 209. And the second one of the vertically extending
access lines, e.g., 203-2, may be adjacent a sidewall of a channel
region 225 of a second one of the horizontally oriented, three-node
access devices 230, e.g., transistors, in the second level (L2)
213-2, and a sidewall of a channel region 225 of a second one of
the horizontally oriented, three-node access devices 230, e.g.,
transistors, in the third level (L3) 213-M, etc. Embodiments are
not limited to a particular number of levels.
[0033] The vertically extending access lines, 203-1, 203-2, . . . ,
203-Q, may include a conductive material, such as, for example, one
of a doped semiconductor material, a conductive metal nitride,
metal, and/or a metal-semiconductor compound. The access lines,
203-1, 203-2, . . . , 203-Q, may correspond to access lines (AL),
e.g., wordlines (WL), described in connection with FIG. 1.
[0034] As shown in the example embodiment of FIG. 2, an insulating
layer dielectric (ILD) 250 may be formed extending in the first
direction (DI) 209 along an end surface of the horizontally
oriented, three-node access devices 230, e.g., transistors, in each
level (L1) 213-1, (L2) 213-2, and (L3) 213-M above the substrate
200. The ILD 250 may isolate and separate the arrays of vertically
stacked memory cells, e.g., 101-1, 101-2, . . . , 101-N in FIG. 1,
along the second direction (D2) 205. The ILD 250 may include an
insulating material, e.g., dielectric material, such as, for
example, one of an oxide material, silicon oxide (SiO.sub.2)
material, silicon nitride (SiN) material, silicon oxynitride
material, and/or combination thereof, etc.
[0035] Although not shown in FIG. 2, an insulating material may
fill other spaces in the vertically stacked array of memory cells.
For example, the insulating material may include one or more of a
silicon oxide material, a silicon nitride material, and/or a
silicon oxynitride material, etc. Embodiments, however, are not
limited to these examples.
[0036] FIG. 3 illustrates in more detail a unit cell, e.g., memory
cell 110 in FIG. 1, of the vertically stacked array of memory
cells, e.g., within a sub cell array 101-2 in FIG. 1, according to
some embodiments of the present disclosure. As shown in FIG. 3, the
first and the second source/drain regions, 321 and 323, may be
impurity doped regions to the horizontally oriented, three-node
access devices 330, e.g., transistors. The first and the second
source/drain regions, 321 and 323, may also comprise a metal,
and/or metal composite materials containing ruthenium (Ru),
molybdenum (Mo), nickel (Ni), titanium (Ti), copper (Cu), a highly
doped degenerate semiconductor material, and/or at least one of
indium oxide (In.sub.2O.sub.3), or indium tin oxide
(In.sub.2-xSn.sub.xO.sub.3), formed using an atomic layer
deposition process, etc. Embodiments, however, are not limited to
these examples. As used herein, a degenerate semiconductor material
is intended to mean a semiconductor material, such as polysilicon,
containing a high level of doping with significant interaction
between dopants, e.g., phosphorous (P), boron (B), etc.
Non-degenerate semiconductors, by contrast, contain moderate levels
of doping, where the dopant atoms are well separated from each
other in the semiconductor host lattice with negligible
interaction. The first and the second source/drain regions, 321 and
323, may be analogous to the first and the second source/drain
regions 221 and 223 shown in FIG. 2.
[0037] The first and the second source/drain regions may be
separated by a channel 325, e.g., channel region, of the
horizontally oriented, three-node access devices 330, e.g.,
transistors. The channel 325 may be a low-doped (p-) polysilicon
material. In some embodiments, the channel 325 may be a low-doped
(p-) poly-germanium (Ge) material. In some embodiments, the channel
325 may be a low doped (p-) poly-silicon-germanium (poly-SiGe)
material. However, in some embodiments the channel 325 may be
comprised of a semiconductor oxide (also referred to herein as an
"oxide semiconductor" or "oxide semiconductor material"). The
semiconductor oxide may comprise any suitable composition; and in
some embodiments may include one or more of indium, zinc, tin and
gallium. Examples of oxide semiconductor materials and/or
compositions, as used herein, including one or more of indium,
zinc, tin and gallium may include such materials as
ZnO.sub.x,O.sub.x, SnO.sub.2, Zn.sub.xO.sub.yN,
Mg.sub.xZn.sub.yO.sub.z, In.sub.xZn.sub.yO.sub.z,
In.sub.xZn.sub.yO.sub.z, In.sub.xGa.sub.yZn.sub.zO.sub.a,
In.sub.xGa.sub.ySi.sub.zO.sub.a, Zr.sub.xIn.sub.yZn.sub.zO.sub.a,
Hf.sub.xIn.sub.yZn.sub.zO.sub.a, Sn.sub.xIn.sub.yZn.sub.zO.sub.a,
Al.sub.xSn.sub.yIn.sub.zZn.sub.aO.sub.b,
Si.sub.xIn.sub.yZn.sub.zO.sub.a, Zn.sub.xSn.sub.yO.sub.z,
Al.sub.xZn.sub.ySn.sub.zO.sub.a, Ga.sub.xZn.sub.ySn.sub.zO.sub.a,
and Zr.sub.xZn.sub.ySn.sub.zO.sub.a.
[0038] In additional embodiments, the channel 325 may be comprised
of a two-dimensional (2D) material. The 2D material may comprise
any suitable composition; and in some embodiments may include one
or more of a transition metal dichalcogenide, including molybdenum
disulfide (MoS.sub.2), molybdenum diselenide (MoSe.sub.2),
molybdenum ditelluride (MoTe.sub.2), tungsten sulfide (WS.sub.2),
and tungsten selenide (WSe.sub.2). Embodiments, however, are not
limited to these examples.
[0039] In some embodiments the channel 325 may comprise a composite
material such as an indium gallium zinc oxide
(In.sub.2Ga.sub.2ZnO.sub.7) material (also referred to herein as
"IGZO"). In some embodiments, the channel 325 may include a
multi-layer In.sub.2Ga.sub.2ZnO.sub.7 channel that is indium (In)
rich in a layer closest to a surface opposing a gate dielectric,
relative to the multiple layers. In some embodiments, the channel
325 may include a multi-layer I.sub.2G.sub.2ZnO.sub.7 channel that
is gallium (Ga) rich in an outer layer, farthest from a surface
opposing a gate dielectric, relative to the multiple layers. And,
in some embodiments, the channel 325 may include a multi-layer
I.sub.2G.sub.2ZnO.sub.7 channel that is zinc (Zn) rich in an outer
layer, farthest from a surface opposing a gate dielectric, relative
to the multiple layers, etc. Embodiments, however, are not limited
to these examples.
[0040] A digit line, e.g., 307-1, analogous to the digit lines
207-1, 207-2, . . . , 207-P in FIGS. 2 and 107-1, 107-2, . . . ,
107-P shown in FIG. 1, may be formed in electrical contact with the
first source/drain region 321. As shown in the example embodiment
of FIG. 3, access lines, e.g., 303-1, analogous to the access lines
203-1, 203-2, . . . , 203-Q in FIGS. 2 and 103-1, 103-2, . . . ,
103-Q in FIG. 1, may be vertically extending in the third direction
(D3) 311 adjacent sidewall of the channel region 325 of the
horizontally oriented, three-node access devices 330, e.g.,
transistors, horizontally conducting between the first and the
second source/drain regions 321 and 323 along the second direction
(D2) 305. A gate dielectric material 304 may be interposed between
the access lines 303-1 (a portion thereof forming a gate to the
horizontally oriented, three-node access devices 330, e.g.,
transistors) and the channel region 325. The gate dielectric
material 304 may include, for example, a high-k dielectric
material, a silicon oxide material, a silicon nitride material, a
silicon oxynitride material, etc., or a combination thereof.
Embodiments are not so limited. For example, in high-k dielectric
material examples the gate dielectric material 304 may include one
or more of hafnium oxide, hafnium silicon oxide, lanthanum oxide,
zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium
oxide, barium strontium titanium oxide, barium titanium oxide,
strontium titanium oxide, lithium oxide, aluminum oxide, lead
scandium tantalum oxide, lead zinc niobite, etc.
[0041] FIG. 4 illustrates an example method, at one stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. In the example embodiment shown in the example of FIG.
4, the method comprises depositing alternating layers of a
dielectric material, 430-1, 430-2, . . . , 430-N (also referred to
herein independently and/or collectively as "430"), and a
sacrificial material, 432-1, 432-2, . . . , 432-N (also referred to
herein independently and/or collectively as "432"), in repeating
iterations to form a vertical stack 401 on a working surface of a
semiconductor substrate 400. In one embodiment, the dielectric
material 430 can be deposited to have a thickness, e.g., vertical
height in the third direction (D3), in a range of twenty (20)
nanometers (nm) to sixty (60) nm. In one embodiment, the
sacrificial material 432 can be deposited to have a thickness,
e.g., vertical height, in a range of twenty (20) nm to one hundred
(100) nm. Embodiments, however, are not limited to these
examples.
[0042] In one example, the sacrificial material, 432-1, 432-2, . .
. , 432-N, can comprise a sacrificial semiconductor material such
as polycrystalline silicon (Si), silicon nitride (SiN), or even an
oxide-based semiconductor composition. While the discussion herein
will refer to a sacrificial semiconductor material example,
embodiments are not limited to this example. It is intended that
the sacrificial material may be selectively etched relative to the
alternating layer of dielectric material, 430-1, 430-2, . . . ,
430-N.
[0043] As shown in FIG. 4, a vertical direction 411 is illustrated
as a third direction (D3), e.g., z-direction in an x-y-z coordinate
system, analogous to the third direction (D3), among first, second
and third directions, shown in FIGS. 1-3. In the example of FIG. 4,
four tiers, numbered 1, 2, 3, and 4, (also referred to in FIG. 2 as
"levels") of the repeating iterations of the vertical stack 401 are
shown. Embodiments, however, are not limited to this example and
more or fewer repeating iterations may be included. A
photolithographic hard mask (HM) layer 435 may be deposited as a
top layer on the repeating iterations of the vertical stack
401.
[0044] In some embodiments, the dielectric material, 430-1, 430-2,
. . . , 430-N, may be an interlayer dielectric (ILD). By way of
example, and not by way of limitation, the dielectric material,
430-1, 430-2, . . . , 430-N, may comprise a silicon dioxide
(SiO.sub.2) material. In another example the dielectric material,
430-1, 430-2, . . . , 430-N, may comprise a silicon nitride
(Si.sub.3N.sub.4) material (also referred to herein a "SiN"). In
another example the dielectric material, 430-1, 430-2, . . . ,
430-N, may comprise a silicon oxy-carbide (SiO.sub.xC.sub.y)
material (also referred to herein as "SiOC"). In another example
the dielectric material, 430-1, 430-2, . . . , 430-N, may include
silicon oxy-nitride (SiO.sub.xN.sub.y) material (also referred to
herein as "SiON"), and/or combinations thereof. Embodiments are not
limited to these examples. In some embodiments the sacrificial
semiconductor material, 432-1, 432-2, . . . , 432-N, may comprise a
silicon (Si) material in a polycrystalline and/or amorphous state.
In another example the sacrificial semiconductor material, 432-1,
432-2, . . . , 432-N, may comprise a silicon nitride (SiN)
material. Embodiments, however, are not limited to these
examples.
[0045] The repeating iterations of alternating dielectric material,
430-1, 430-2, . . . 430-N, layers and sacrificial semiconductor
material, 432-1, 432-2, . . . , 432-N, layers may be deposited
according to a semiconductor fabrication process such as chemical
vapor deposition (CVD) in a semiconductor fabrication apparatus.
Embodiments, however, are not limited to this example and other
suitable semiconductor fabrication techniques may be used to
deposit the alternating layers of a dielectric material, 430-1,
430-2, . . . , 430-N, and a sacrificial semiconductor material,
432-1, 432-2, . . . , 432-N, in repeating iterations to form a
vertical stack 401, as shown in FIG. 4.
[0046] FIG. 5A illustrates an example method, at another stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. FIG. 5A illustrates a top down view of a semiconductor
structure, at a particular point in time, in a semiconductor
fabrication process, according to one or more embodiments. In the
example embodiment shown in the example of FIG. 5A, the method
comprises using an etchant process to form a plurality of access
line formation vertical openings 500, having a first horizontal
direction (D1) 509 and a second horizontal direction (D2) 505,
through the vertical stack to the substrate. In one example, as
shown in FIG. 5A, the plurality of access line vertical openings
500 are extending predominantly in the second horizontal direction
(D2) 505 and may form elongated vertical, pillar columns 513 with
sidewalls 514 in the vertical stack. The plurality of access line
vertical openings 500 may be formed using photolithographic
techniques to pattern a photolithographic mask 535, e.g., to form a
hard mask (HM), on the vertical stack prior to etching the
plurality of access line vertical openings 500.
[0047] FIG. 5B is a cross sectional view, taken along cut-line A-A'
in FIG. 5A, showing another view of the semiconductor structure at
a particular time in the semiconductor fabrication process. FIG. 5B
illustrates that a conductive material, 540-1, 540-2, . . . ,
540-4, may be formed on a gate dielectric material 538 in the
plurality of first vertical openings 500. By way of example and not
by way of limitation, a gate dielectric material 538 may be
conformally deposited in the plurality of access line vertical
openings 500 using a chemical vapor deposition (CVD) process,
plasma enhanced CVD (PECVD), atomic layer deposition (ALD), or
other suitable deposition process, to cover a bottom surface and
the vertical sidewalls of the plurality of first vertical openings.
The gate dielectric 538 may be deposited to a particular thickness
(t1) as suited to a particular design rule, e.g., a gate dielectric
thickness of approximately 10 nanometers (nm). Embodiments,
however, are not limited to this example. By way of example, and
not by way of limitation, the gate dielectric 538 may comprise a
silicon dioxide (SiO.sub.2) material, aluminum oxide (Al2O3)
material, high dielectric constant (k), e.g, high-k, dielectric
material, and/or combinations thereof as also described in FIG.
3.
[0048] Further, as shown in FIG. 5B, a conductive material, 540-1,
540-2, . . . , 540-4, may be conformally deposited in the plurality
of access line vertical openings 500 on a surface of the gate
dielectric material 538. By way of example, and not by way of
limitation, the conductive material, 540-1, 540-2, . . . , 540-4,
may be conformally deposited in the plurality of access line
vertical openings 500 on a surface of the gate dielectric material
538 using a chemical vapor deposition process (CVD), plasma
enhanced CVD (PECVD), atomic layer deposition (ALD), or other
suitable deposition process, to cover a bottom surface and the
vertical sidewalls of the plurality of first vertical openings over
the gate dielectric 538. The conductive material, 540-1, 540-2, . .
. , 540-4, may be conformally deposited to a particular thickness
(t2) to form vertically oriented access lines, such as shown as
access lines 103-1, 103-2, . . . , 103-Q (which also may be
referred to a wordlines) shown in FIGS. 1, et. seq., and as suited
to a particular design rule. For example, the conductive material,
540-1, 540-2, . . . , 540-4, may be conformally deposited to a
thickness of approximately 20 nanometers (nm). Embodiments,
however, are not limited to this example. By way of example, and
not by way of limitation, the conductive material, 540-1, 540-2, .
. . , 540-4, may be comprise a metal such as tungsten (W), metal
composition, titanium nitride (TiN), doped polysilicon, and/or some
other combination thereof as also described in FIG. 3.
[0049] As shown in FIG. 5B, the conductive material, 540-1, 540-2,
. . . , 540-4, may be recessed back to remain only along the
vertical sidewalls of the elongated vertical, pillar columns, shown
as 542-1, 542-2, and 542-3 in the cross-sectional view of FIG. 5B.
The conductive material, 540-1, 540-2, . . . , 540-4, may be
recessed back by using a suitable selective, anisotropic, e.g.,
directional, etch process to remove the conductive material, 540-1,
540-2, . . . , 540-4, from a bottom surface of the first vertical
openings, e.g., 500 in FIG. 5A, exposing the gate dielectric 538 on
the bottom surface to form separate, vertical access lines, 540-1,
540-2, . . . , 540-4, now shown only remaining on the sidewalls
514. As shown in FIG. 5B, a dielectric material 539, such as an
oxide or other suitable spin on dielectric (SOD), may then be
deposited in the access line vertical openings 500, using a process
such as CVD, to fill the access line vertical openings 500. The
dielectric may be planarized to a top surface of the hard mask 535
of the vertical semiconductor stack, e.g., 401 as shown in FIG. 4,
using chemical mechanical planarization (CMP) or other suitable
semiconductor fabrication technique. A subsequent photolithographic
material 536, e.g., hard mask, may be deposited using CVD and
planarized using CMP to cover and close the conductive material,
540-1, 540-2, . . . , 540-4 remaining only on sidewalls 514 of the
access line vertical openings 500. Similar semiconductor process
techniques may be used at other points of the semiconductor
fabrication process described herein.
[0050] FIG. 6A illustrates an example method, at another stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. FIG. 6A illustrates a top down view of a semiconductor
structure, at a particular point in time, in a semiconductor
fabrication process, according to one or more embodiments. In the
example embodiment of FIG. 6A, the method comprises using a
photolithographic process to pattern the photolithographic mask
636, 536 in FIG. 5B. The method in FIG. 6A, further illustrates
using a selective, isotropic (e.g., non-directional) etchant
process remove portions of the exposed conductive material, 540-1,
540-2, . . . , 540-4 in FIG. 5B, to separate and individually form
the plurality of separate, vertical access lines, 640-1, 640-2, . .
. , 640-N, 640-(N+1), . . . , 640-(Z-1), and 640-Z, e.g., access
lines 103-1, 103-2, . . . , 103-Q in FIGS. 1, et. seq. Hence the
plurality of separate, vertical access lines, 640-1, 640-2, . . . ,
640-N, 640-(N+1), . . . , 640-(Z-1), and 640-Z, are shown along the
sidewalls of the elongated vertical, pillar columns, e.g., along
sidewalls of the elongated vertical, pillar columns 542-1, 542-2,
and 542-3 in the cross-sectional view of FIG. 5B.
[0051] As shown in the example of FIG. 6A, the exposed conductive
material, 540-1, 540-2, . . . , 540-4 in FIG. 5B, may be removed
back to the gate dielectric material 638 in the access line
vertical openings, e.g., 500 in FIG. 5A, using a suitable
selective, isotropic (e.g., non-directional) etch process. As shown
in FIG. 6A, a subsequent dielectric material 641, such as an oxide
or other suitable spin on dielectric (SOD), may then be deposited,
using a process such as CVD, or other suitable technique, to fill
the remaining openings from where the exposed conductive material,
540-1, 540-2, . . . , 540-4 in FIG. 5B, was removed. The dielectric
material 641 may be planarized to a top surface of the previous
hard mask 635 of the vertical semiconductor stack, e.g., 401 as
shown in FIG. 4, using a process such as CMP, or other suitable
technique. In some embodiments, a subsequent photolithographic
material 537, e.g., hard mask, may be deposited using CVD and
planarized using ClVIP to cover and close the plurality of
separate, vertical access lines, 640-1, 640-2, . . . , 640-N,
640-(N+1), . . . , 640-(Z-1), and 640-Z, over a working surface of
the vertical semiconductor stack, 401 in FIG. 4, leaving the
plurality of separate, vertical access lines, 640-1, 640-2, . . . ,
640-N, 640-(N+1), . . . , 640-(Z-1), and 640-Z, protected along the
sidewalls of the elongated vertical, pillar columns, shown as
642-1, 642-2, and 642-3 in the cross-sectional view. Embodiments,
however, are not limited to these process examples.
[0052] FIG. 6B illustrates a cross sectional view, taken along
cut-line A-A' in FIG. 6A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 6B is away from the plurality of
separate, vertical access lines, 640-1, 640-2, . . . , 640-N,
640-(N+1), . . . , 640-(Z-1), and shows the repeating iterations of
alternating layers of a dielectric material, 630-1, 630-2, . . . ,
630-N, and a sacrificial semiconductor material, 632-1, 632-2, . .
. , 632-N, on a semiconductor substrate 400 to form the vertical
stack, e.g. 401 as shown in FIG. 4. As shown in FIG. 6B, a vertical
direction 611 is illustrated as a third direction (D3), e.g.,
z-direction in an x-y-z coordinate system, analogous to the third
direction (D3) 111, among first, second and third directions, shown
in FIGS. 1-3. The plane of the drawing sheet, extending right and
left, is in a first direction (D1) 609. In the example embodiment
of FIG. 6B, the dielectric material 641 is shown filling the
vertical openings on the residual gate dielectric 638 deposition.
The hard mask 637, described above, caps the illustrated
structure.
[0053] FIG. 6C illustrates a cross sectional view, taken along
cut-line B-B' in FIG. 6A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 6C is illustrated extending in
the second direction (D2) 605 along an axis of the repeating
iterations of alternating layers of a dielectric material, 630-1,
630-2, . . . , 630-N, and a sacrificial semiconductor material,
632-1, 632-2, . . . , 632-N, along and in which the horizontally
oriented access devices and horizontally oriented storage nodes,
e.g., capacitor cells, can be formed within the layers of
sacrificial semiconductor material, 632-1, 632-2, . . . , 632-N. In
FIG. 6C, a neighboring, opposing vertical access line 640-3 is
illustrated by a dashed line indicating a location set in from the
plane and orientation of the drawing sheet.
[0054] FIG. 6D illustrates a cross sectional view, taken along
cut-line C-C' in FIG. 6A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 6D is illustrated extending in
the second direction (D2) 605 along an axis of the repeating
iterations of alternating layers of a dielectric material, 630-1,
630-2, . . . , 630-N, and a sacrificial semiconductor material,
632-1, 632-2, . . . , 632-N, outside of a region in which the
horizontally oriented access devices and horizontally oriented
storage nodes, e.g., capacitor cells, will be formed within the
layers of sacrificial semiconductor material, 632-1, 632-2, . . . ,
632-N. In FIG. 6C, the dielectric material 641 is shown filling the
space between the horizontally oriented access devices and
horizontally oriented storage nodes, which can be spaced along a
first direction (D1), extending into and out from the plane of the
drawings sheet, for a three dimensional array of vertically
oriented memory cells. At the left end of the drawing sheet is
shown the repeating iterations of alternating layers of a
dielectric material, 630-1, 630-2, . . . , 630-(N+1), and a
sacrificial semiconductor material, 632-1, 632-2, . . . , 632-N, at
which location a horizontally oriented digit line, e.g., digit
lines 107-1, 107-2, . . . , 107-P shown in FIG. 1, et. seq., can be
integrated to form electrical contact with the second source/drain
regions, described in more detail below.
[0055] FIG. 6E illustrates a cross sectional view, taken along
cut-line D-D' in FIG. 6A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 6E is illustrated, right to left
in the plane of the drawing sheet, extending in the first direction
(D1) 609 along an axis of the repeating iterations of alternating
layers of a dielectric material, 630-1, 630-2, . . . , 630-N, and a
sacrificial semiconductor material, 632-1, 632-2, . . . , 632-N,
intersecting across the plurality of separate, vertical access
lines, 640-1, 640-2, . . . , 640-N, 640-(N+1), . . . , 640-(Z-1),
and intersecting regions of the sacrificial semiconductor material,
632-1, 632-2, . . . , 632-N, in which a channel region may be
formed, separated from the plurality of separate, vertical access
lines, 640-1, 640-2, . . . , 640-N, 640-(N+1), . . . , 640-(Z-1),
by the gate dielectric 638. In FIG. 6E, the first dielectric fill
material 639 is shown separating the space between neighboring
horizontally oriented access devices and horizontally oriented
storage nodes, which may be formed extending into and out from the
plane of the drawing sheet as described in more detail below, and
can be spaced along a first direction (D1) 609 and stacked
vertically in arrays extending in the third direction (D3) 611 in
the three dimensional (3D) memory.
[0056] FIG. 7A illustrates an example method, at another stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. FIG. 7A illustrates a top down view of a semiconductor
structure, at a particular point in time, in a semiconductor
fabrication process, according to one or more embodiments. In the
example embodiment of FIG. 7A, the method comprises using a
photolithographic process to pattern the photolithographic masks
535, 536 and/or 637, etc. as described in FIGS. 5 and 6. The method
in FIG. 7A, further illustrates using one or more etchant processes
to form a first vertical opening, 771-1 and 771-2, in access device
regions, e.g., 742 in FIG. 7A and 742 in FIG. 7C for replacement
channel and replacement source/drain transistor regions, through
the vertical stack. The first vertical openings 771-1 and 771-2 are
illustrated extending predominantly in the first horizontal
direction (D1) 709. The one or more etchant processes forms first
vertical openings, 771-1 and 771-2, to expose first sidewalls in
the repeating iterations of alternating layers of a dielectric
material, 730-1, 730-2, . . . , 730-(N+1), and a sacrificial
semiconductor material, 732-1, 732-2, . . . , 732-N, in the
vertical stack, shown in FIGS. 7B-7E, adjacent a first region of
the sacrificial semiconductor material. Other numerated components
may be analogous to those shown and discussed in connection with
FIGS. 5 and 6.
[0057] According to embodiments, an access device region 742 is
shown in FIG. 7A and 7C, e.g., transistor region, of the
sacrificial semiconductor material, 732-1, 732-2, . . . , 732-N,
may be removed from the repeating iterations of alternating layers
of a dielectric material, 730-1, 730-2, . . . , 730-(N+1), and a
sacrificial semiconductor material, 732-1, 732-2, . . . , 732-N, in
the vertical stack to form an access device, e.g. transistor.
According to embodiments, this process is performed before
selectively removing a storage node region of the sacrificial
semiconductor material in which to form a capacitor cell. According
to one embodiment the sacrificial semiconductor material, 732-1,
732-2, . . . , 732-N, is an oxide sacrificial semiconductor
material (e.g., oxide semiconductor) such as polycrystalline and/or
amorphous silicon dioxide (SiO.sub.2) According to an example
embodiment, shown in FIGS. 7B-7E, the method comprises selectively
etching the access device region 742, e.g., first region, of the
sacrificial semiconductor material, 732-1, 732-2, . . . , 732-N, to
form a first horizontal opening a first horizontal distance 751
(D1) back from first vertical openings, 771-1 and 771-2 in the
vertical stack. One example of selectively etching the sacrificial
semiconductor material, 732-1, 732-2, . . . , 732-N, comprises
using an atomic layer etching (ALE) process. Other techniques may
be used.
[0058] In some embodiments, as shown in FIGS. 7B-7E, the method
comprises forming a transistor having a first source/drain region,
channel region, and second source/drain region as the access device
in the first horizontal opening. By way of example, and not by way
of limitation, forming the first source/drain region, the channel
region, and the second source/drain region comprises using an
atomic layer deposition (ALD) process to sequentially deposit, in
the first horizontal opening, the first source/drain region, the
channel region, and the second source/drain region. One example ALD
process for forming first and second source/drain regions is
disclosed in co-filed, co-pending, U.S. patent application Ser. No.
16/986,510, attorney docket no. 1013.0570001, having at least one
common inventor and titled "Source/Drain Integration in Three-Node
Access Device for Vertical Three Dimensional (3D) Memory". Another
example for channel region formation is disclosed in co-filed,
co-pending, U.S. patent application Ser. No. 16/986,466, attorney
docket no. 1013.0560001, having at least one common inventor and
titled "Channel Integration in Three-Node Access Device for
Vertical Three Dimensional (3D) Memory". Other suitable
semiconductor fabrication techniques and/or storage nodes
structures may be used.
[0059] FIG. 7B illustrates a cross sectional view, taken along
cut-line A-A' in FIG. 7A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 7B is away from the plurality of
separate, vertical access lines, 740-1, 740-2, . . . , 740-N,
740-(N+1), 740-(Z-1), and shows repeating iterations of alternating
layers of a dielectric material, 730-1, 730-2, . . . , 730-(N+1),
and sacrificial semiconductor material, 732-1, 732-2, . . . ,
732-N, e.g., sacrificial oxide semiconductor material separated by
vertical isolation trenches having gate dielectric 738 lined walls
and filed with isolation material such as spin on dielectric (SOD)
741 as explained in connection with FIGS. 6B and 6D. As shown in
FIG. 7B, a vertical direction 711 is illustrated as a third
direction (D3), e.g., z-direction in an x-y-z coordinate system,
analogous to the third direction (D3) 111, among first, second and
third directions, shown in FIGS. 1-3. The plane of the drawing
sheet, extending right and left, is in a first direction (D1)
709.
[0060] FIG. 7C illustrates a cross sectional view, taken along
cut-line B-B' in FIG. 7A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 7C is illustrated extending in
the second direction (D2) 705, left and right along the plane of
the drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 730-1, 730-2, . . . ,
730-(N+1). However, now is shown that the sacrificial semiconductor
material has been removed in a access device region 742 of the
alternating layers of the vertical stack to form horizontal
openings, 733-1, 733-2, . . . , 733-N, e.g., in first region 742.
It is these horizontal openings, 733-1, 733-2, . . . , 733-N, in
which the horizontally oriented access devices having a first
source/drain region, channel region, and second source/drain region
can be formed between the vertical alternating layers of a
dielectric material, 730-1, 730-2, . . . , 730-(N+1). It is in a
second region 744 that storage nodes will be formed subsequent to
the formation of the horizontal access devices in the horizontal
openings, 733-1, 733-2, . . . , 733-N.
[0061] In the example embodiment of FIG. 7C, the horizontally
openings 730-1, 730-2, . . . , 730-N, in which to form the access
devices having a first source/drain region, channel region, and
second source/drain region, are shown extending in second direction
705 (D2), left and right in the plane of the drawing sheet, a first
distance (D1opening) 751 from the vertical openings 771-1 and 771-2
formed in the vertical stack and along an axis of orientation of
the horizontal access devices and horizontal storage nodes of the
arrays of vertically stacked memory cells of the three dimensional
(3D) memory. In FIG. 7C, a neighboring, opposing vertical access
line 740-3 is illustrated by a dashed line indicating a location
set inward from the plane and orientation of the drawing sheet
separated by a remaining wall of gate dielectric 738 deposited in
access line trenches 500 in FIGS. 5 and 6.
[0062] FIG. 7D illustrates a cross sectional view, taken along
cut-line C-C' in FIG. 7A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 7D is illustrated extending in
the second direction (D2) 705, left and right in the plane of the
drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 730-1, 730-2, . . . ,
730-N, 730-(N+1) and horizontal openings 733-1, 733-2, . . . ,
733-N, outside of a region in which the horizontally oriented
access devices and horizontally oriented storage nodes, e.g.,
capacitor cells, will be formed. In FIG. 7D, the dielectric
material 741 is shown filling the space between the horizontally
oriented access devices, which can be spaced along a first
direction (D1), extending into and out from the plane of the
drawings sheet, for a three dimensional array of vertically
oriented memory cells. At the left end of the drawing sheet is
shown the repeating iterations of alternating layers of a
dielectric material, 730-1, 730-2, . . . , 730-(N+1), and
horizontal openings, 733-1, 733-2, . . . , 733-N, at which location
a horizontally oriented digit line, e.g., digit lines 107-1, 107-2,
. . . , 107-P shown in FIG. 1, et. seq., can be integrated to form
electrical contact once the second source/drain regions of the
formed horizontal access devices are formed.
[0063] FIG. 7E illustrates a cross sectional view, taken along
cut-line D-D' in FIG. 7A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 7E is illustrated, right to left
in the plane of the drawing sheet, extending in the first direction
(D1) 709 along an axis of the repeating iterations of alternating
layers of a dielectric material, 730-1, 730-2, . . . , 730-(N+1),
and horizontal openings, 733-1, 733-2, . . . , 733-N, in which
channel regions will be formed separated from the plurality of
separate, vertical access lines, 740-1, 740-2, . . . , 740-4, by
the gate dielectric 738. In FIG. 7E, the first dielectric fill
material 739 is shown separating the space between neighboring
horizontally oriented access devices and horizontally oriented
storage nodes, which may be formed extending into and out from the
plane of the drawing sheet as described in more detail below, and
can be spaced along a first direction (D1) 709 and stacked
vertically in arrays extending in the third direction (D3) 711 in
the three dimensional (3D) memory.
[0064] FIG. 8A illustrates an example method, at another stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. FIG. 8A illustrates a top down view of a semiconductor
structure, at a particular point in time, in a semiconductor
fabrication process, according to one or more embodiments. In the
example embodiment of FIG. 8A, the vertical openings 871-1 and
871-2 remain present from FIG. 7A-7E. However, in FIGS. 8A-8E,
horizontal access devices, 898-1, 898-2, . . . , 898-N, having
first source/drain regions, channel regions, and second
source/drain regions, shown respectively as 898-1A, 898-1B, and
898-1C, in FIG. 8C, have been formed in the horizontal openings,
733-1, 733-2, . . . , 733-N shown in FIGS. 7C and 7D. The
horizontal access devices, 898-1, 898-2, 898-N, are formed
extending in the second direction 805 (D2) in the horizontal access
device regions 842 of the vertical stack. Additionally, horizontal
digit lines, 899-1, 899-2, 899-N, have been formed and integrated
in contact with the second source/drain regions, e.g., 898-1C, as
shown in FIGS. 8C and 8D. Other numerated components may be
analogous to those shown and discussed in connection with FIGS. 6,
and 7.
[0065] According to embodiments, in the access device region 842,
e.g., transistor region, the sacrificial semiconductor material,
632-1, 632-2, . . . , 632-N, in FIGS. 6A-6E, has been removed, and
the horizontal openings, 733-1, 733-2, . . . , 733-N, have been
filled with horizontal access devices 898, e.g. transistors.
According to embodiments, this process is performed before
selectively removing a storage node region 844 of the sacrificial
semiconductor material in which to form a capacitor cell. According
to an example embodiment, shown in FIGS. 8B-8E, the method
comprises selectively depositing, using an atomic layer deposition
(ALD) process, or other suitable deposition technique, a first
source/drain region 838-1A, channel region 838-1B, and second
source/drain region 838-1C in each of the horizontal openings,
733-1, 733-2, . . . , 733-N, in FIGS. 7A-7E. By way of example, and
not by way of limitation, forming the first source/drain region,
the channel region, and the second source/drain region comprises
using an atomic layer deposition (ALD) process to sequentially
deposit, in the first horizontal opening, the first source/drain
region, the channel region, and the second source/drain region
Other suitable semiconductor fabrication techniques and/or storage
nodes structures may be used.
[0066] FIG. 8B illustrates a cross sectional view, taken along
cut-line A-A' in FIG. 8A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 8B is away from the plurality of
separate, vertical access lines, 840-1, 840-2, . . . , 840-N,
840-(N+1), 840-(Z-1), and shows repeating iterations of alternating
layers of a dielectric material, 830-1, 830-2, . . . , 830-(N+1),
separated by a second region 844 of sacrificial semiconductor
material, 832-1, 832-2, . . . , 832-NAs shown in FIG. 8B, a
vertical direction 811 is illustrated as a third direction (D3),
e.g., z-direction in an x-y-z coordinate system, analogous to the
third direction (D3) 111, among first, second and third directions,
shown in FIGS. 1-3. The plane of the drawing sheet, extending right
and left, is in a first direction (D1) 809.
[0067] FIG. 8C illustrates a cross sectional view, taken along
cut-line B-B' in FIG. 8A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 8C is illustrated extending in
the second direction (D2) 805, left and right along the plane of
the drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 830-1, 830-2, . . . ,
830-(N+1).
[0068] However, now it is shown that the first source/drain region
material, channel region material, and second source/drain region
material, 898-1, 898-2, . . . , 898-N have been deposited in the
horizontal openings, 733-1, 733-2, . . . , 733-N, in FIGS. 7A-7E,
extending in the second direction 805 (D2). In one example, a first
source/drain region 898-1, a channel region 898-1B, and 898-1C are
illustrated distinctly. Further, horizontal digit line, 899-1,
899-2, . . . , 899-N, integration is achieved in contact with the
second source/drain regions, e.g., 898-1C, extending in a first
direction (D1), e.g., extending into and out from the plane of the
drawing sheet in alternating layers vertically with the dielectric
material, 830-1, 830-2, . . . , 830-(N+1) in direction (D3) 811. In
one example, the horizontal digit line, 899-1, 899-2, . . . ,
899-N, integration is achieved by filling the first vertical
openings 871 with a suitable digit line conductive material such as
tungsten (W) or highly doped semiconductor material, using a CVD
process, and isotropically etching to recess the horizontal digit
line, 899-1, 899-2, . . . , 899-N, into remaining portions of the
horizontal openings, 733-1, 733-2, . . . , 733-N in FIGS. 7, in
electrical contact with the second source/drain regions, e.g.,
898-1C. In another example, the horizontal digit line, 899-1,
899-2, . . . , 899-N, integration is achieved by using an atomic
layer deposition (ALD) process to fill the remaining portions of
the horizontal openings, 733-1, 733-2, . . . , 733-N in FIGS. 7,
and form electrical contact with the second source/drain regions,
e.g., 898-1C.
[0069] Hence, three-node horizontal access devices, 838-1, 838-2, .
. . , 838-N, have been formed and integrated to vertical access
lines, 840-1, 840-2, . . . , 840-(Z+1) and integrated to digit
lines, 899-1, 899-2, . . . , 899-N, without body contacts and with
improved capacitor cell formation sequencing. Advantages to the
structure and process described herein can include a lower
off-current (Ioff) for the access devices, as compared to silicon
based (Si-based) access devices. The channel region, e.g., 838-1B,
may be free from minority carriers for the access devices and thus
removing the need to control a body potential to a body region of
the access device, and/or reduced gate/drain induced leakage (GIDL)
for the access devices.
[0070] According to embodiments channel and/or source/drain region
replacement fabrication steps may be performed before a capacitor
cell formation process. The digit line integration may be more
easily achieved in the fabrication process since a body contact to
a body region of the access device is not used. Additionally, the
embodiments described herein may achieve a better lateral scaling
path than achieved with doped polysilicon based channel regions due
to less channel length and lower source/drain semiconductor
fabrication process formation overhead.
[0071] The first source/drain region, the channel region, and the
second source/drain region of the horizontal access devices, 898-1,
898-2, . . . , 898-N, and the horizontal digit line, 899-1, 899-2,
. . . , 899-N, integration may be performed according to ALD
processes and techniques. One example ALD process for forming first
and second source/drain regions is disclosed in co-filed,
co-pending, U.S. patent application Ser. No. 16/986,510, attorney
docket no. 1013.0570001, having at least one common inventor and
titled "Source/Drain Integration in Three-Node Access Device for
Vertical Three Dimensional (3D) Memory". Another example for
channel region formation is disclosed in co-filed, co-pending, U.S.
patent application Ser. No. 16/986,466, attorney docket no.
1013.0560001, having at least one common inventor and titled
"Channel Integration in Three-Node Access Device for Vertical Three
Dimensional (3D) Memory". According to various embodiments, a
further benefit is the avoidance, e.g., no use of, gas phase doping
(GPD) in the formation of the source/drain regions. Other suitable
semiconductor fabrication techniques and/or storage nodes
structures may be used.
[0072] In the example embodiment of FIG. 8C, the horizontal access
devices having a first source/drain region, channel region, and
second source/drain region, 898-1, 898-2, . . . , 898-N, are shown
extending in second direction 805 (D2), left and right in the plane
of the drawing sheet, a first distance (D1) (751 in FIGS. 7) from
the first vertical openings 871-1 and 871-2 formed in the vertical
stack and along an axis of orientation of the horizontal access
devices and horizontal storage nodes of the arrays of vertically
stacked memory cells of the three dimensional (3D) memory. As shown
in FIG. 10, as dielectric material may be deposited to fill the
vertical openings 871-1 and 871-2. In FIG. 8C, a neighboring,
opposing vertical access line 840-3 is illustrated by a dashed line
indicating a location set inward from the plane and orientation of
the drawing sheet.
[0073] FIG. 8D illustrates a cross sectional view, taken along
cut-line C-C' in FIG. 8A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 8D is illustrated extending in
the second direction (D2) 805, left and right in the plane of the
drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 830-1, 830-2, . . . ,
830-N, 830-(N+1) and horizontal digit lines, 899-1, 899-2, . . . ,
899-N, extending into and out from the plane of the drawing sheet
in a first direction (D1), outside of a region in which the
horizontally oriented access devices, 898-1, 898-2, . . . , 898-N,
and horizontally oriented storage nodes, e.g., capacitor cells, in
access device region 842 and storage node region 844 are formed. In
FIG. 8D, the dielectric material 841 is shown filling the space
between the horizontally oriented access devices, which can be
spaced along a first direction (D1), extending into and out from
the plane of the drawings sheet, for a three dimensional array of
vertically oriented memory cells. At the left end of the drawing
sheet is shown the repeating iterations of alternating layers of a
dielectric material, 830-1, 830-2, . . . , 830-(N+1), and
horizontal digit lines, 899-1, 899-2, . . . , 899-N, e.g., digit
lines 107-1, 107-2, . . . , 107-P shown in FIG. 1, et. seq.,
integrated to form electrical contact with the second source/drain
regions, e.g., 838-1A, of the formed horizontal access devices.
[0074] FIG. 8E illustrates a cross sectional view, taken along
cut-line D-D' in FIG. 8A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 8E is illustrated, right to left
in the plane of the drawing sheet, extending in the first direction
(D1) 809 along an axis of the repeating iterations of alternating
layers of a dielectric material, 830-1, 830-2, . . . , 830-(N+1),
and channel regions of the horizontal access devices, 898-1, 898-2,
. . . , 898-N, separated from the plurality of separate, vertical
access lines, 840-1, 840-2, . . . , 840-4, by the gate dielectric
838. In FIG. 8E, the first dielectric fill material 839 is shown
separating the space between neighboring horizontally oriented
access devices and horizontally oriented storage nodes, which may
be formed extending into and out from the plane of the drawing
sheet as described in more detail below, and can be spaced along a
first direction (D1) 809 and stacked vertically in arrays extending
in the third direction (D3) 811 in the three dimensional (3D)
memory.
[0075] FIG. 9A illustrates an example method, at another stage of a
semiconductor fabrication process, for forming arrays of vertically
stacked memory cells, having horizontally oriented access devices
and vertically oriented access lines, such as illustrated in FIGS.
1-3, and in accordance with a number of embodiments of the present
disclosure. FIG. 9A illustrates a top down view of a semiconductor
structure, at a particular point in time, in a semiconductor
fabrication process, according to one or more embodiments. In the
example embodiment of FIG. 9A, the method comprises using a
photolithographic process to pattern the photolithographic masks
935, 936 and/or 937, e.g., 635, 636, and/or 637 in FIGS. 6A-6E. The
method in FIG. 9A, further illustrates using one or more etchant
processes to form a vertical opening 951 in a storage node region
950 (and 844 in FIGS. 8A and 8C) through the vertical stack and
extending predominantly in the first horizontal direction (D1) 909.
The one or more etchant processes forms a vertical opening 951 to
expose second sidewalls in the repeating iterations of alternating
layers of a dielectric material, 930-1, 930-2, . . . , 930-N, and a
sacrificial semiconductor material, 932-1, 932-2, . . . , 932-N, in
the vertical stack, shown in FIGS. 9B-9E, adjacent a second region
of the sacrificial semiconductor material. Other numerated
components may be analogous to those shown and discussed in
connection with FIG. 6, or earlier Figures.
[0076] According to embodiments, a second region 944 of the
sacrificial semiconductor material, 932-1, 932-2, . . . , 932-N,
may be removed from the repeating iterations of alternating layers
of a dielectric material, 930-1, 930-2, . . . , 930-N, and a
sacrificial semiconductor material, 932-1, 932-2, . . . , 932-N, in
the vertical stack to form a storage node. According to
embodiments, this process is performed after selectively removing
an access device region of the sacrificial semiconductor material
in which to form a first source/drain region, channel region, and
second source/drain region of the horizontally oriented access
devices. According to embodiments, selectively etching the second
region 944 can include performing an atomic layer etching (ALE)
process selective to the sacrificial semiconductor material, 932-1,
932-2, . . . , 932-N, in the second region 944.
[0077] According to an example embodiment, shown in FIGS. 9B-9E,
the method comprises selectively etching the second region 944 of
the sacrificial semiconductor material, 932-1, 932-2, . . . ,
932-N, to form a second horizontal opening a second horizontal
distance 957 (D2opening) back from a vertical opening 951 in the
vertical stack. In some embodiments, as shown in FIGS. 9B-9E, the
method comprises forming capacitor cell as the storage node in the
second horizontal opening. By way of example, and not by way of
limitation, forming the capacitor comprises using an atomic layer
deposition (ALD) process to sequentially deposit, in the second
horizontal opening, a first electrode 961 and a second electrode
956 separated by a cell dielectric 963. Other suitable
semiconductor fabrication techniques and/or storage nodes
structures may be used.
[0078] FIG. 9B illustrates a cross sectional view, taken along
cut-line A-A' in FIG. 9A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 9B is away from the plurality of
separate, vertical access lines, 940-1, 940-2, . . . , 940-N,
940-(N+1), . . . , 940-(Z-1), and shows repeating iterations of
alternating layers of a dielectric material, 930-1, 930-2, . . . ,
930-(N+1), separated by horizontally oriented capacitor cells
having first electrodes 961, e.g., bottom cell contact electrodes,
cell dielectrics 963, and second electrodes 956, e.g., top, common
node electrodes, on a semiconductor substrate 900 to form the
vertical stack.. As shown in FIG. 9B, a vertical direction 911 is
illustrated as a third direction (D3), e.g., z-Client direction in
an x-y-z coordinate system, analogous to the third direction (D3)
111, among first, second and third directions, shown in FIGS. 1-3.
The plane of the drawing sheet, extending right and left, is in a
first direction (D1) 909. In the example embodiment of FIG. 9B, the
first electrodes 961, e.g., bottom electrodes, are in direct
electrical, ohmic contact with source/drain regions of horizontal
access devices (using the same as an etch stop in the formation
process), and second electrodes 956 are illustrated separated by a
cell dielectric material 963 extending into and out of the plane of
the drawing sheet in second direction (D2) and along an axis of
orientation of the horizontal access devices and horizontal storage
nodes of the arrays of vertically stacked memory cells of the three
dimensional (3D) memory.
[0079] The first and second electrodes may be formed of any
suitable conductive material such as doped polysilicon, metal,
e.g., titanium (Ti), tungsten (W), etc., and/or conductive metal
composition, e.g., titanium nitride (TiN), tantalum nitride (TaN),
etc. Embodiments are not limited to these examples. In various
embodiments, the cell dielectric material 963 can be a high-k
dielectric material and may include one or more of hafnium oxide,
hafnium silicon oxide, lanthanum oxide, zirconium oxide, zirconium
silicon oxide, tantalum oxide, titanium oxide, barium strontium
titanium oxide, barium titanium oxide, strontium titanium oxide,
lithium oxide, aluminum oxide, lead scandium tantalum oxide, lead
zinc niobite, etc. Embodiments are not limited to these
examples.
[0080] FIG. 9C illustrates a cross sectional view, taken along
cut-line B-B' in FIG. 9A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 9C is illustrated extending in
the second direction (D2) 905, left and right along the plane of
the drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 930-1, 930-2, . . . ,
930-(N+1), the horizontally oriented access devices 998 and
integrally formed digit lines 999 in region 942, and the
subsequently formed storage nodes, e.g., capacitor cells, formed in
region 944. In the example embodiment of FIG. 9C, the horizontally
oriented storage nodes, e.g., capacitor cells, are illustrated as
having been formed been formed in this semiconductor fabrication
process and first electrodes 961, e.g., bottom electrodes to be
coupled to source/drain regions of horizontal access devices, and
second electrodes 956, e.g., top electrodes to be coupled to a
common electrode plane such as a ground plane, separated by cell
dielectrics 963, are shown. According to embodiments, the first
electrodes 961, e.g., bottom electrodes to be coupled to
source/drain regions of horizontal access devices, and second
electrodes 956, e.g., top electrodes to be coupled to a common
electrode plane such as a ground plane, separated by cell
dielectrics 963, are formed subsequent to forming a first
source/drain region, a channel region, and a second source/drain
region in a region of the horizontally oriented access devices
998.
[0081] In the example embodiment of FIG. 9C, the horizontally
oriented storage nodes having the first electrodes 961, e.g.,
bottom electrodes to be coupled to source/drain regions of
horizontal access devices, and second electrodes 956, e.g., top
electrodes to be coupled to a common electrode plane such as a
ground plane, are shown formed in a second horizontal opening
extending in second direction (D2), left and right in the plane of
the drawing sheet, a second distance 957 (D2opening) from the
vertical opening 951 formed in the vertical stack and along an axis
of orientation of the horizontal access devices and horizontal
storage nodes of the arrays of vertically stacked memory cells of
the three dimensional (3D) memory. In FIG. 9C, a neighboring,
opposing vertical access line 940-3 is illustrated by a dashed line
indicating a location set inward from the plane and orientation of
the drawing sheet.
[0082] FIG. 9D illustrates a cross sectional view, taken along
cut-line C-C' in FIG. 9A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 9D is illustrated extending in
the second direction (D2) 905, left and right in the plane of the
drawing sheet, along an axis of the repeating iterations of
alternating layers of a dielectric material, 930-1, 930-2, . . . ,
930-N, 930-(N+1) and a sacrificial semiconductor material, 932-1,
932-2, . . . , 932-N, outside of a region in which the horizontally
oriented access devices and horizontally oriented storage nodes,
e.g., capacitor cells, are formed. In FIG. 9C, the dielectric
material 941 is shown filling the space between the horizontally
oriented access devices, which can be spaced horizontally along a
first direction (D1), extending into and out from the plane of the
drawings sheet, for a three dimensional array of vertically
oriented memory cells. In the cross sectional view of FIG. 9D, the
second electrode 956, e.g., top, common electrode to the a
capacitor cell structure, is additionally shown present in the
space between horizontally neighboring devices. At the left end of
the drawing sheet is shown the repeating iterations of alternating
layers of a dielectric material, 930-1, 930-2, . . . , 930-(N+1),
and the integrally formed horizontally oriented digit lines 999
extending into and out from the plane of the drawing sheet, and
connected to a source/drain region of the horizontally oriented
access devices.
[0083] FIG. 9E illustrates a cross sectional view, taken along
cut-line D-D' in FIG. 9A, showing another view of the semiconductor
structure at this particular point in one example semiconductor
fabrication process of an embodiment of the present disclosure. The
cross sectional view shown in FIG. 9E is illustrated, right to left
in the plane of the drawing sheet, extending in the first direction
(D1) 909 along an axis of the repeating iterations of alternating
layers of a dielectric material, 930-1, 930-2, . . . , 930-(N+1),
and a channel region, e.g., 998-1B in FIG. 9C, of the horizontally
oriented access devices 998, extending in to and out from a plane
of the drawing sheet, and intersecting across the plurality of
separate, vertical access lines, 940-1, 940-2, . . . , 940-4
separated from the channel regions by the gate dielectric 938. In
FIG. 9E, the first dielectric fill material 939 is shown separating
the space between neighboring horizontally oriented access devices
and horizontally oriented storage nodes, which may be formed
extending into and out from the plane of the drawing sheet and can
be spaced along a first direction (D1) 909 and stacked vertically
in arrays extending in the third direction (D3) 911 in the three
dimensional (3D) memory.
[0084] FIG. 10 illustrates a three-node horizontally oriented
access device 1042 coupled to a horizontally oriented storage node
1044 for vertical three dimensional (3D) memory, according to
embodiments of the present disclosures. In FIG. 10, the three-node
horizontally oriented access device 1042 is illustrated extending
in a second direction (D2) 1005, left and right in the plane of the
drawing sheet. The horizontally oriented access device 1042 is
illustrated having a first source/drain region 1098-1A in
electrical contact with a first electrode 1061, e.g., bottom
electrode, of the horizontally oriented storage node 1044, e.g.,
capacitor cell. The storage node 1044 is further illustrated with a
dielectric material 1063 separating the first electrode 1061 from a
second electrode 1056, e.g., top, common node electrode of the
capacitor cell.
[0085] A channel region 1098-1B is illustrated in electrical
contact with the first source/drain region 1098-1A. A vertically
oriented access line 1040-3 opposes the channel region 1098-1B and
is separated therefrom by a gate dielectric. The vertically
oriented access line 1040-2 is illustrated by dashed lines
indicating that the vertically oriented access line is set into
and/or out from the plane of the drawing sheet. The vertically
oriented access line 1040 may extend longer and/or shorter than the
channel region in the second direction (D2) 1005, e.g., having
source/drain overlap and/or underlap, according to particular
design rules.
[0086] A second source/drain region 1098-1C is illustrated in
electrical contact with the channel region 1098-1B and in
electrical contact with and integrated to a horizontally oriented
digit line 1099 extending into and out from a plane of the drawing
sheet. As shown in FIG. 10, the horizontally oriented access device
1042 and horizontally oriented storage node 1044 may be spaced
horizontally from neighboring memory cells by an interlayer
dielectric material 1080 along the second direction (D2) 1005 and
may be spaced vertically from stacked, neighboring cells in a three
dimensional (3D) memory by dielectric layers 1030-1 and 1030-2.
[0087] FIG. 11 is a block diagram of an apparatus in the form of a
computing system 1100 including a memory device 1103 in accordance
with a number of embodiments of the present disclosure. As used
herein, a memory device 1103, a memory array 1110, and/or a host
1102, for example, might also be separately considered an
"apparatus." According to embodiments, the memory device 1102 may
comprise at least one memory array 1110 having a three-node access
device for vertical three dimensional (3D) memory, as has been
described herein.
[0088] In this example, system 1100 includes a host 1102 coupled to
memory device 103 via an interface 1104. The computing system 1100
can be a personal laptop computer, a desktop computer, a digital
camera, a mobile telephone, a memory card reader, or an
Internet-of-Things (IoT) enabled device, among various other types
of systems. Host 1102 can include a number of processing resources
(e.g., one or more processors, microprocessors, or some other type
of controlling circuitry) capable of accessing memory 1103. The
system 1100 can include separate integrated circuits, or both the
host 1102 and the memory device 1103 can be on the same integrated
circuit. For example, the host 1102 may be a system controller of a
memory system comprising multiple memory devices 1103, with the
system controller 1105 providing access to the respective memory
devices 1103 by another processing resource such as a central
processing unit (CPU).
[0089] In the example shown in FIG. 1, the host 1102 is responsible
for executing an operating system (OS) and/or various applications
(e.g., processes) that can be loaded thereto (e.g., from memory
device 1103 via controller 1105). The OS and/or various
applications can be loaded from the memory device 1103 by providing
access commands from the host 1102 to the memory device 1103 to
access the data comprising the OS and/or the various applications.
The host 1102 can also access data utilized by the OS and/or
various applications by providing access commands to the memory
device 1103 to retrieve said data utilized in the execution of the
OS and/or the various applications.
[0090] For clarity, the system 1100 has been simplified to focus on
features with particular relevance to the present disclosure. The
memory array 1110 can be a DRAM array, SRAM array, STT RAM array,
PCRAM array, TRAM array, RRAM array, NAND flash array, and/or NOR
flash array, comprising at least one three-node access device for
three dimension (3D) memory. For example, the memory array 1110 can
be an unshielded DL 4F2 array such as a 3D-DRAM memory array. The
array 1110 can comprise memory cells arranged in rows coupled by
word lines (which may be referred to herein as access lines or
select lines) and columns coupled by digit lines (which may be
referred to herein as sense lines or data lines). Although a single
array 1110 is shown in FIG. 1, embodiments are not so limited. For
instance, memory device 1103 may include a number of arrays 1110
(e.g., a number of banks of DRAM cells).
[0091] The memory device 1103 includes address circuitry 1106 to
latch address signals provided over an interface 1104. The
interface can include, for example, a physical interface employing
a suitable protocol (e.g., a data bus, an address bus, and a
command bus, or a combined data/address/command bus). Such protocol
may be custom or proprietary, or the interface 1104 may employ a
standardized protocol, such as Peripheral Component Interconnect
Express (PCIe), Gen-Z, CCIX, or the like. Address signals are
received and decoded by a row decoder 1108 and a column decoder
1112 to access the memory array 1110. Data can be read from memory
array 1110 by sensing voltage and/or current changes on the sense
lines using sensing circuitry 111. The sensing circuitry 1111 can
comprise, for example, sense amplifiers that can read and latch a
page (e.g., row) of data from the memory array 1110. The I/O
circuitry 1107 can be used for bi-directional data communication
with the host 1102 over the interface 1104. The read/write
circuitry 1113 is used to write data to the memory array 1110 or
read data from the memory array 1110. As an example, the circuitry
1113 can comprise various drivers, latch circuitry, etc.
[0092] Control circuitry 1105 decodes signals provided by the host
1102. The signals can be commands provided by the host 1102. These
signals can include chip enable signals, write enable signals, and
address latch signals that are used to control operations performed
on the memory array 1110, including data read operations, data
write operations, and data erase operations. In various
embodiments, the control circuitry 1105 is responsible for
executing instructions from the host 1102. The control circuitry
1105 can comprise a state machine, a sequencer, and/or some other
type of control circuitry, which may be implemented in the form of
hardware, firmware, or software, or any combination of the three.
In some examples, the host 1102 can be a controller external to the
memory device 103. For example, the host 1102 can be a memory
controller which is coupled to a processing resource of a computing
device.
[0093] The term semiconductor can refer to, for example, a
material, a wafer, or a substrate, and includes any base
semiconductor structure. "Semiconductor" is to be understood as
including silicon-on-sapphire (SOS) technology,
silicon-on-insulator (SOI) technology, thin-film-transistor (TFT)
technology, doped and undoped semiconductors, epitaxial silicon
supported by a base semiconductor structure, as well as other
semiconductor structures. Furthermore, when reference is made to a
semiconductor in the preceding description, previous process steps
may have been utilized to form regions/junctions in the base
semiconductor structure, and the term semiconductor can include the
underlying materials containing such regions/junctions.
[0094] The figures herein follow a numbering convention in which
the first digit or digits correspond to the drawing figure number
and the remaining digits identify an element or component in the
drawing. Similar (e.g., the same) elements or components between
different figures may be identified by the use of similar digits.
As will be appreciated, elements shown in the various embodiments
herein can be added, exchanged, and/or eliminated so as to provide
a number of additional embodiments of the present disclosure. In
addition, as will be appreciated, the proportion and the relative
scale of the elements provided in the figures are intended to
illustrate the embodiments of the present disclosure and should not
be taken in a limiting sense.
[0095] As used herein, "a number of" or a "quantity of" something
can refer to one or more of such things. For example, a number of
or a quantity of memory cells can refer to one or more memory
cells. A "plurality" of something intends two or more. As used
herein, multiple acts being performed concurrently refers to acts
overlapping, at least in part, over a particular time period. As
used herein, the term "coupled" may include electrically coupled,
directly coupled, and/or directly connected with no intervening
elements (e.g., by direct physical contact), indirectly coupled
and/or connected with intervening elements, or wirelessly coupled.
The term coupled may further include two or more elements that
co-operate or interact with each other (e.g., as in a cause and
effect relationship). An element coupled between two elements can
be between the two elements and coupled to each of the two
elements.
[0096] It should be recognized the term vertical accounts for
variations from "exactly" vertical due to routine manufacturing,
measuring, and/or assembly variations and that one of ordinary
skill in the art would know what is meant by the term
"perpendicular." For example, the vertical can correspond to the
z-direction. As used herein, when a particular element is "adjacent
to" an other element, the particular element can cover the other
element, can be over the other element or lateral to the other
element and/or can be in direct physical contact the other element.
Lateral to may refer to the horizontal direction (e.g., the
y-direction or the x-direction) that may be perpendicular to the
z-direction, for example.
[0097] Although specific embodiments have been illustrated and
described herein, those of ordinary skill in the art will
appreciate that an arrangement calculated to achieve the same
results can be substituted for the specific embodiments shown. This
disclosure is intended to cover adaptations or variations of
various embodiments of the present disclosure. It is to be
understood that the above description has been made in an
illustrative fashion, and not a restrictive one. Combination of the
above embodiments, and other embodiments not specifically described
herein will be apparent to those of skill in the art upon reviewing
the above description. The scope of the various embodiments of the
present disclosure includes other applications in which the above
structures and methods are used. Therefore, the scope of various
embodiments of the present disclosure should be determined with
reference to the appended claims, along with the full range of
equivalents to which such claims are entitled.
* * * * *