U.S. patent application number 16/292279 was filed with the patent office on 2020-07-30 for hybrid bonding using dummy bonding contacts and dummy interconnects.
This patent application is currently assigned to Yangtze Memory Technologies Co., Ltd.. The applicant listed for this patent is YANGTZE MEMORY TECHNOLOGIES CO., LTD.. Invention is credited to Jun Chen, Si Ping Hu, Zi Qun Hua, Shi Qi Huang, Jia Wen Wang, Tao Wang, Jifeng Zhu.
Application Number | 20200243455 16/292279 |
Document ID | 20200243455 / US20200243455 |
Family ID | 1000003973609 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200243455 |
Kind Code |
A1 |
Wang; Tao ; et al. |
July 30, 2020 |
HYBRID BONDING USING DUMMY BONDING CONTACTS AND DUMMY
INTERCONNECTS
Abstract
Embodiments of bonded semiconductor structures and fabrication
methods thereof are disclosed. In an example, a semiconductor
device includes a first and a second semiconductor structures. The
first semiconductor structure includes a first interconnect layer
including first interconnects. At least one first interconnect is a
first dummy interconnect. The first semiconductor structure further
includes a first bonding layer including first bonding contacts.
Each first interconnect is in contact with a respective first
bonding contact. The second semiconductor structure includes a
second interconnect layer including second interconnects. At least
one second interconnect is a second dummy interconnect. The second
semiconductor structure further includes a second bonding layer
including second bonding contacts. Each second interconnect is in
contact with a respective second bonding contact. The semiconductor
device further includes a bonding interface between the first and
second bonding layers. Each first bonding contact is in contact
with a respective second bonding contact at the bonding
interface.
Inventors: |
Wang; Tao; (Wuhan, CN)
; Hu; Si Ping; (Wuhan, CN) ; Wang; Jia Wen;
(Wuhan, CN) ; Huang; Shi Qi; (Wuhan, CN) ;
Zhu; Jifeng; (Wuhan, CN) ; Chen; Jun; (Wuhan,
CN) ; Hua; Zi Qun; (Wuhan, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YANGTZE MEMORY TECHNOLOGIES CO., LTD. |
Wuhan |
|
CN |
|
|
Assignee: |
Yangtze Memory Technologies Co.,
Ltd.
|
Family ID: |
1000003973609 |
Appl. No.: |
16/292279 |
Filed: |
March 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2019/073909 |
Jan 30, 2019 |
|
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16292279 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/1157 20130101;
H01L 23/53238 20130101; H01L 27/11582 20130101; H01L 24/06
20130101; H01L 21/76841 20130101; H01L 23/5384 20130101; H01L 24/20
20130101; H01L 24/19 20130101 |
International
Class: |
H01L 23/532 20060101
H01L023/532; H01L 23/538 20060101 H01L023/538; H01L 23/00 20060101
H01L023/00; H01L 21/768 20060101 H01L021/768; H01L 27/1157 20060101
H01L027/1157; H01L 27/11582 20060101 H01L027/11582 |
Claims
1. A semiconductor device, comprising: a first semiconductor
structure comprising: a first interconnect layer comprising a
plurality of first interconnects, at least one of the first
interconnects being at least one first dummy interconnect; and a
first bonding layer comprising a plurality of first bonding
contacts, each of the first interconnects being in contact with a
respective one of the first bonding contacts; a second
semiconductor structure comprising: a second interconnect layer
comprising a plurality of second interconnects, at least one of the
second interconnects being at least one second dummy interconnect;
and a second bonding layer comprising a plurality of second bonding
contacts, each of the second interconnects being in contact with a
respective one of the second bonding contacts; and a bonding
interface between the first bonding layer and the second bonding
layer, wherein each of the first bonding contacts is in contact
with a respective one of the second bonding contacts at the bonding
interface.
2. The semiconductor device of claim 1, wherein a number of the
first bonding contacts is the same as a number of the first
interconnects, and a number of the first bonding contacts is the
same as a number of the first interconnects.
3. The semiconductor device of claim 1, wherein a number of the
first dummy interconnects is the same as a number of the second
dummy interconnects.
4. The semiconductor device of claim 1, wherein each of the first
bonding contacts has a nominally same first critical dimension, and
each of the second bonding contacts has a nominally same second
critical dimension.
5. The semiconductor device of claim 1, wherein the first and
second bonding contacts comprise a pair of dummy bonding contacts
in contact with one another at the bonding interface, the pair of
dummy bonding contacts electrically connecting a respective pair of
first and second dummy interconnects.
6. The semiconductor device of claim 1, wherein the first bonding
layer further comprises a first dielectric, and the second bonding
layer further comprises a second dielectric in contact with the
first dielectric at the bonding interface.
7. The semiconductor device of claim 1, wherein the first bonding
contacts are nominally evenly disposed at the bonding interface,
and the second bonding contacts are nominally evenly disposed at
the bonding interface.
8. The semiconductor device of claim 1, wherein one of the first
semiconductor structure and the second semiconductor structure
further comprises a device layer having a NAND memory string, and
another one of the first semiconductor structure and the second
semiconductor structure further comprises a device layer having a
peripheral device.
9. The semiconductor device of claim 8, wherein the first and
second dummy interconnects are not electrically connected to the
NAND memory string and the peripheral device.
10. A bonded structure, comprising: a bonding interface; a pair of
functional bonding contacts in contact with one another at the
bonding interface, wherein the pair of functional bonding contacts
are in contact with a pair of functional interconnects on opposite
sides of the bonding interface, respectively; and a pair of dummy
bonding contacts in contact with one another at the bonding
interface, wherein the pair of dummy bonding contacts are in
contact with a pair of dummy interconnects on the opposite sides of
the bonding interface, respectively.
11. The bonding structure of claim 10, further comprising a pair of
dielectrics in contact with one another at the bonding
interface.
12. A method for forming a semiconductor device, comprising:
forming a first interconnect layer comprising a plurality of first
interconnects above a first substrate, wherein at least one of the
first interconnects is at least one first dummy interconnect;
forming a first bonding layer comprising a plurality of first
bonding contacts above the first interconnect layer, such that each
of the first interconnects is in contact with a respective one of
the first bonding contacts; forming a second interconnect layer
comprising a plurality of second interconnects above a second
substrate, wherein at least one of the second interconnects is at
least one second dummy interconnect; forming a second bonding layer
comprising a plurality of second bonding contacts above the second
interconnect layer, such that each of the second interconnects is
in contact with a respective one of the second bonding contacts;
and bonding the first substrate and the second substrate in a
face-to-face manner, such that each of the first bonding contacts
is in contact with a respective one of the second bonding contacts
at a bonding interface.
13. The method of claim 12, wherein forming the first bonding layer
comprises forming the first bonding contacts by a single patterning
process.
14. The method of claim 12, wherein forming the second bonding
layer comprises forming the second bonding contacts by a single
patterning process.
15. The method of claim 12, wherein a number of the first bonding
contacts is the same as a number of first interconnects, and a
number of the first bonding contacts is the same as a number of
first interconnects.
16. The method of claim 12, wherein each of the first bonding
contacts has a nominally same first critical dimension, and each of
the second bonding contacts has a nominally same second critical
dimension.
17. The method of claim 12, wherein: forming the first bonding
layer comprises forming a first dielectric in the first bonding
layer; forming the second bonding layer comprises forming a second
dielectric in the second bonding layer; and the first dielectric is
in contact with the second dielectric at the bonding interface
after the bonding.
18. The method of claim 12, further comprising: forming a first
device layer having a NAND memory string between the first
interconnect layer and the first substrate; and forming a second
device layer having a peripheral device between the second
interconnect layer and the second substrate, wherein the first and
second dummy interconnects are not electrically connected to the
NAND memory string and the peripheral device.
19. The method of claim 12, further comprising: forming a first
device layer having a peripheral device between the first
interconnect layer and the first substrate; and forming a second
device layer having a NAND memory string between the second
interconnect layer and the second substrate, wherein the first and
second dummy interconnects are not electrically connected to the
NAND memory string and the peripheral device.
20. The method of claim 12, wherein the bonding comprises hybrid
bonding.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is continuation of International
Application No. PCT/CN2019/073909, filed on Jan. 30, 2019, entitled
"HYBRID BONDING USING DUMMY BONDING CONTACTS AND DUMMY
INTERCONNECTS," which is hereby incorporated by reference in its
entirety. This application is also related to co-pending U.S.
application Ser. No. ______, Attorney Docketing No.:
10018-01-0033-US, filed on even date, entitled "HYBRID BONDING
USING DUMMY BONDING CONTACTS," which is hereby incorporated by
reference in its entirety.
BACKGROUND
[0002] Embodiments of the present disclosure relate to bonded
semiconductor structures and fabrication methods thereof.
[0003] Planar semiconductor devices, such as memory cells, are
scaled to smaller sizes by improving process technology, circuit
design, programming algorithm, and fabrication process. However, as
feature sizes of the semiconductor devices approach a lower limit,
planar process and fabrication techniques become challenging and
costly. A three-dimensional (3D) device architecture can address
the density limitation in some planar semiconductor devices, for
example, Flash memory devices.
[0004] A 3D semiconductor device can be formed by stacking
semiconductor wafers or dies and interconnecting them vertically
using, for instance, through-silicon vias (TSVs) or
copper-to-copper (Cu--Cu) connections, so that the resulting
structure acts as a single device to achieve performance
improvements at reduced power and smaller footprint than
conventional planar processes. Among the various techniques for
stacking semiconductor substrates, hybrid bonding is recognized as
one of the promising techniques because of its capability of
forming high-density interconnects.
SUMMARY
[0005] Embodiments of semiconductor devices, bonded structures, and
fabrication methods thereof are disclosed herein.
[0006] In one example, a semiconductor device includes a first
semiconductor structure and a second semiconductor structure. The
first semiconductor structure includes a first interconnect layer
including a plurality of first interconnects. At least one of the
first interconnects is at least one first dummy interconnect. The
first semiconductor structure further includes a first bonding
layer including a plurality of first bonding contacts. Each of the
first interconnects is in contact with a respective one of the
first bonding contacts. The second semiconductor structure includes
a second interconnect layer including a plurality of second
interconnects. At least one of the second interconnects is at least
one second dummy interconnect. The second semiconductor structure
further includes a second bonding layer including a plurality of
second bonding contacts. Each of the second interconnects is in
contact with a respective one of the second bonding contacts. The
semiconductor device further includes a bonding interface between
the first bonding layer and the second bonding layer. Each of the
first bonding contacts is in contact with a respective one of the
second bonding contacts at the bonding interface.
[0007] In another example, a bonded structure includes a bonding
interface, a pair of functional bonding contacts, and a pair of
dummy bonding contacts. The pair of functional bonding contacts are
in contact with one another at the bonding interface. The pair of
bonding contacts are in contact with a pair of functional
interconnects on opposite sides of the bonding interface,
respectively. The pair of dummy bonding contacts are in contact
with one another at the bonding interface. The pair of dummy
bonding contacts are in contact with a pair of dummy interconnects
on the opposite sides of the bonding interface, respectively.
[0008] In still another example, a method for forming a
semiconductor device is disclosed. A first interconnect layer
including a plurality of first interconnects is formed above a
first substrate. At least one of the first interconnects is at
least one first dummy interconnect. A first bonding layer including
a plurality of first bonding contacts is formed above the first
interconnect layer, such that each of the first interconnects is in
contact with a respective one of the first bonding contacts. A
second interconnect layer including a plurality of second
interconnects is formed above a second substrate. At least one of
the second interconnects is at least one second dummy interconnect.
A second bonding layer including a plurality of second bonding
contacts is formed above the second interconnect layer, such that
each of the second interconnects is in contact with a respective
one of the second bonding contacts. The first substrate and the
second substrate are bonded in a face-to-face manner, such that
each of the first bonding contacts is in contact with a respective
one of the second bonding contacts at a bonding interface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings, which are incorporated herein and
form a part of the specification, illustrate embodiments of the
present disclosure and, together with the description, further
serve to explain the principles of the present disclosure and to
enable a person skilled in the pertinent art to make and use the
present disclosure.
[0010] FIG. 1 illustrates a cross-section of an exemplary bonded
semiconductor device, according to some embodiments of the present
disclosure.
[0011] FIGS. 2A and 2B illustrate cross-sections of various
exemplary bonded semiconductor devices including dummy bonding
contacts, according to various embodiments of the present
disclosure.
[0012] FIG. 3 illustrates a cross-section of an exemplary bonded
semiconductor device including dummy bonding contacts and dummy
interconnects, according to some embodiments of the present
disclosure.
[0013] FIGS. 4A and 4B illustrate an exemplary fabrication process
for forming a first semiconductor structure including dummy bonding
contacts, according to some embodiments of the present
disclosure.
[0014] FIGS. 5A-5C illustrate an exemplary fabrication process for
forming a second semiconductor structure including dummy bonding
contacts, according to some embodiments of the present
disclosure.
[0015] FIG. 6 illustrates an exemplary fabrication process for
bonding a first semiconductor structure and a second semiconductor
structure, according to some embodiments of the present
disclosure.
[0016] FIGS. 7A and 7B illustrate an exemplary fabrication process
for forming a first semiconductor structure including dummy bonding
contacts and dummy interconnects, according to some embodiments of
the present disclosure.
[0017] FIGS. 8A and 8B illustrate an exemplary fabrication process
for forming a second semiconductor structure including dummy
bonding contacts and dummy interconnects, according to some
embodiments of the present disclosure.
[0018] FIG. 9 illustrates another exemplary fabrication process for
bonding a first semiconductor structure and a second semiconductor
structure, according to some embodiments of the present
disclosure.
[0019] FIG. 10 is a flowchart of a method for forming an exemplary
bonded semiconductor device including dummy bonding contacts,
according to some embodiments of the present disclosure.
[0020] FIG. 11 is a flowchart of a method for forming an exemplary
bonded semiconductor device including dummy bonding contacts and
dummy interconnects, according to some embodiments of the present
disclosure.
[0021] Embodiments of the present disclosure will be described with
reference to the accompanying drawings.
DETAILED DESCRIPTION
[0022] Although specific configurations and arrangements are
discussed, it should be understood that this is done for
illustrative purposes only. A person skilled in the pertinent art
will recognize that other configurations and arrangements can be
used without departing from the spirit and scope of the present
disclosure. It will be apparent to a person skilled in the
pertinent art that the present disclosure can also be employed in a
variety of other applications.
[0023] It is noted that references in the specification to "one
embodiment," "an embodiment," "an example embodiment," "some
embodiments," etc., indicate that the embodiment described may
include a particular feature, structure, or characteristic, but
every embodiment may not necessarily include the particular
feature, structure, or characteristic. Moreover, such phrases do
not necessarily refer to the same embodiment. Further, when a
particular feature, structure or characteristic is described in
connection with an embodiment, it would be within the knowledge of
a person skilled in the pertinent art to effect such feature,
structure or characteristic in connection with other embodiments
whether or not explicitly described.
[0024] In general, terminology may be understood at least in part
from usage in context. For example, the term "one or more" as used
herein, depending at least in part upon context, may be used to
describe any feature, structure, or characteristic in a singular
sense or may be used to describe combinations of features,
structures or characteristics in a plural sense. Similarly, terms,
such as "a," "an," or "the," again, may be understood to convey a
singular usage or to convey a plural usage, depending at least in
part upon context. In addition, the term "based on" may be
understood as not necessarily intended to convey an exclusive set
of factors and may, instead, allow for existence of additional
factors not necessarily expressly described, again, depending at
least in part on context.
[0025] It should be readily understood that the meaning of "on,"
"above," and "over" in the present disclosure should be interpreted
in the broadest manner such that "on" not only means "directly on"
something but also includes the meaning of "on" something with an
intermediate feature or a layer therebetween, and that "above" or
"over" not only means the meaning of "above" or "over" something
but can also include the meaning it is "above" or "over" something
with no intermediate feature or layer therebetween (i.e., directly
on something).
[0026] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper," and the like, may be used
herein for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. The apparatus
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0027] As used herein, the term "substrate" refers to a material
onto which subsequent material layers are added. The substrate
itself can be patterned. Materials added on top of the substrate
can be patterned or can remain unpatterned. Furthermore, the
substrate can include a wide array of semiconductor materials, such
as silicon, germanium, gallium arsenide, indium phosphide, etc.
Alternatively, the substrate can be made from an electrically
non-conductive material, such as a glass, a plastic, or a sapphire
wafer.
[0028] As used herein, the term "layer" refers to a material
portion including a region with a thickness. A layer can extend
over the entirety of an underlying or overlying structure or may
have an extent less than the extent of an underlying or overlying
structure. Further, a layer can be a region of a homogeneous or
inhomogeneous continuous structure that has a thickness less than
the thickness of the continuous structure. For example, a layer can
be located between any pair of horizontal planes between, or at, a
top surface and a bottom surface of the continuous structure. A
layer can extend horizontally, vertically, and/or along a tapered
surface. A substrate can be a layer, can include one or more layers
therein, and/or can have one or more layer thereupon, thereabove,
and/or therebelow. A layer can include multiple layers. For
example, an interconnect layer can include one or more conductor
and contact layers (in which interconnect lines and/or via contacts
are formed) and one or more dielectric layers.
[0029] As used herein, the term "nominal/nominally" refers to a
desired, or target, value of a characteristic or parameter for a
component or a process operation, set during the design phase of a
product or a process, together with a range of values above and/or
below the desired value. The range of values can be due to slight
variations in manufacturing processes or tolerances. As used
herein, the term "about" indicates the value of a given quantity
that can vary based on a particular technology node associated with
the subject semiconductor device. Based on the particular
technology node, the term "about" can indicate a value of a given
quantity that varies within, for example, 10-30% of the value
(e.g., .+-.10%, .+-.20%, or .+-.30% of the value).
[0030] As used herein, the term "3D memory device" refers to a
semiconductor device with vertically oriented strings of memory
cell transistors (referred to herein as "memory strings," such as
NAND memory strings) on a laterally-oriented substrate so that the
memory strings extend in the vertical direction with respect to the
substrate. As used herein, the term "vertical/vertically" means
nominally perpendicular to the lateral surface of a substrate.
[0031] In a high density, low feature size (e.g., below 0.5 .mu.m)
hybrid bonding process, in order to increase the bonding yield, the
bonding contacts on opposite sides of the bonding interface are
often made by two dual damascene processes each involving two
patterning processes (e.g., two photolithography and development
processes). To reduce the high cost of using four patterning
processes, fabrication processes involving only three or even two
patterning processes have been proposed to make the bonding
contacts. However, known processes cannot form dummy bonding
contacts at the bonding interface to achieve desired uniformity of
metal and dielectric distribution at the bonding interface, thereby
decreasing the bonding yield and strength. For example, the
variation of metal local density can cause the nonuniformity of
erosion control and dishing control during the subsequent chemical
mechanical polishing (CMP) process. Also, the lack of dummy bonding
contacts can cause a large number of metal-dielectric bonding and
dielectric-dielectric bonding regions, which have lower bonding
strengths than metal-metal bonding regions.
[0032] Various embodiments in accordance with the present
disclosure provide hybrid bonding using dummy bonding contacts for
improving bonding yield and strength. The dummy bonding contacts
and functional bonding contacts on at least one side of the bonding
interface can be made in a single patterning process, thereby
reducing the process cost. In some embodiments, the local density
of the bonding contacts can be controlled by adding the dummy
bonding contacts based on the design of the interconnects in the
lower layer to increase the bonding yield and strength. In some
embodiments, the dummy bonding contacts and functional bonding
contacts on each side of the bonding interface are made in a single
patterning process, thereby further reducing the cost of the hybrid
bonding process. Dummy interconnects can be added into the
interconnect layer to enable adding additional dummy bonding
contacts in the upper layer in a single patterning process without
affecting the electrical connections in the bonded device.
[0033] FIG. 1 illustrates a cross-section of an exemplary bonded
semiconductor device 100, according to some embodiments of the
present disclosure. For ease of description, bonded semiconductor
device 100 will be described as a non-monolithic 3D memory device.
However, it is understood that bonded semiconductor device 100 is
not limited to a 3D memory device and can include any suitable
bonded semiconductor devices that can use dummy bonding contacts to
improve bonding interface properties as described below in detail.
It is understood that bonded semiconductor devices that include
dummy bonding contacts at its bonding interface as disclosed herein
are not limited to the examples shown in FIG. 1 and can include any
other suitable semiconductor devices, such as logic devices,
volatile memory devices (e.g., dynamic random-access memory (DRAM)
and static random-access memory (SRAM)), and non-volatile memory
devices (e.g., Flash memory), in a 2D, 2.5D, or 3D
architecture.
[0034] Bonded semiconductor device 100 represents an example of a
non-monolithic 3D memory device. The term "non-monolithic" means
that the components of bonded semiconductor device 100 (e.g.,
peripheral devices and memory array devices) can be formed
separately on different substrates and then bonded to form a bonded
semiconductor device. Bonded semiconductor device 100 can include a
substrate 102, which can include silicon (e.g., single crystalline
silicon), silicon germanium (SiGe), gallium arsenide (GaAs),
germanium (Ge), silicon on insulator (SOI), or any other suitable
materials.
[0035] It is noted that x and y axes are included in FIG. 1 to
further illustrate the spatial relationship of the components in
bonded semiconductor device 100 having substrate 102. Substrate 102
includes two lateral surfaces (e.g., a top surface and a bottom
surface) extending laterally in the x-direction (i.e., the lateral
direction). As used herein, whether one component (e.g., a layer or
a device) is "on," "above," or "below" another component (e.g., a
layer or a device) of a semiconductor device (e.g., bonded
semiconductor device 100) is determined relative to the substrate
of the semiconductor device (e.g., substrate 102) in the
y-direction (i.e., the vertical direction) when the substrate is
positioned in the lowest plane of the semiconductor device in the
y-direction. The same notion for describing spatial relationship is
applied throughout the present disclosure.
[0036] Bonded semiconductor device 100 can include two
semiconductor structures, i.e., a memory array device chip 160 and
a peripheral device chip 162 bonded in a face-to-face manner at a
bonding interface 158. In some embodiments, bonding interface 158
is disposed between memory array device chip 160 and peripheral
device chip 162 as a result of hybrid bonding (also known as
"metal/dielectric hybrid bonding"), which is a direct bonding
technology (e.g., forming bonding between surfaces without using
intermediate layers, such as solder or adhesives) and can obtain
metal-metal bonding and dielectric-dielectric bonding
simultaneously. In some embodiments, bonding interface 158 is the
place at which memory array device chip 160 and peripheral device
chip 162 are met and bonded. In practice, bonding interface 158 can
be a layer with a certain thickness that includes the bottom
surface of memory array device chip 160 and the bottom surface of
peripheral device chip 162. It is understood that although memory
array device chip 160 is disposed above peripheral device chip 162
in FIG. 1, their relative positions can be reversed in some
embodiments. For example, memory array device chip 160 can be
disposed below peripheral device chip 162 in another bonded
semiconductor device.
[0037] Peripheral device chip 162 can include a peripheral device
layer 103 on substrate 102. Peripheral device layer 103 can include
a peripheral device (e.g., a plurality of transistors 104) formed
on substrate 102. Transistors 104 can be formed "on" substrate 102,
where the entirety or part of each transistor 104 is formed in
substrate 102 (e.g., below the top surface of substrate 102) and/or
directly on substrate 102. Isolation regions (e.g., shallow trench
isolations (STIs), not shown) and doped regions (e.g., source
regions and drain regions of transistors 104, not shown) can be
formed in substrate 102.
[0038] In some embodiments, the peripheral device of peripheral
device layer 103 can include any suitable digital, analog, and/or
mixed-signal peripheral circuits used for facilitating the
operation of bonded semiconductor device 100. For example, the
peripheral device of peripheral device layer 103 can include one or
more of a page buffer, a decoder (e.g., a row decoder and a column
decoder), a sense amplifier, a driver, a charge pump, a current or
voltage reference, or any active or passive components of the
circuits (e.g., transistors, diodes, resistors, or capacitors). In
some embodiments, the peripheral device of peripheral device layer
103 is formed on substrate 102 using complementary
metal-oxide-semiconductor (CMOS) technology (also known as a "CMOS
chip").
[0039] Peripheral device chip 162 can include an interconnect layer
106 (referred to herein as a "peripheral interconnect layer") above
peripheral device layer 103 to transfer electrical signals to and
from peripheral device layer 103. Peripheral interconnect layer 106
can include a plurality of interconnects 108 (also referred to
herein as "contacts"), including lateral interconnect lines and
vertical interconnect access (via) contacts. As used herein, the
term "interconnects" can broadly include any suitable types of
interconnects, such as middle-end-of-line (MEOL) interconnects and
back-end-of-line (BEOL) interconnects. As described below in
detail, interconnects 108 in peripheral interconnect layer 106 can
include functional interconnects that are electrically connected to
the peripheral device and optionally, further include dummy
interconnects that are not electrically connected to any peripheral
device in peripheral device layer 103. Peripheral interconnect
layer 106 can further include one or more interlayer dielectric
(ILD) layers (also known as "intermetal dielectric (IMD) layers")
in which the interconnect lines and via contacts can form. That is,
peripheral interconnect layer 106 can include interconnects 108 in
multiple ILD layers. Interconnects 108 in peripheral interconnect
layer 106 can include conductive materials including, but not
limited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),
silicides, or any combination thereof. The ILD layers in peripheral
interconnect layer 106 can include dielectric materials including,
but not limited to, silicon oxide, silicon nitride, silicon
oxynitride, low dielectric constant (low-k) dielectrics, or any
combination thereof.
[0040] As shown in FIG. 1, peripheral device chip 162 can further
include a bonding layer 111 at bonding interface 158 and above
peripheral interconnect layer 106 and peripheral device layer 103.
Bonding layer 111 can include a plurality of bonding contacts 112
and a dielectric 113 electrically isolating bonding contacts 112.
Bonding contacts 112 can include functional bonding contacts 112-1,
each of which is part of an electrical connection between
peripheral device chip 162 and memory array device chip 160.
Bonding contacts 112 can also include dummy bonding contacts 112-2,
each of which is not part of any electrical connection between
peripheral device chip 162 and memory array device chip 160. As
described below in detail, dummy bonding contacts 112-2 can be used
for increasing the local density of bonding contacts 112 at bonding
interface 158 to increase bonding yield and strength. Bonding
contacts 112 can include conductive materials including, but not
limited to, W, Co, Cu, Al, silicides, or any combination thereof.
The remaining area of bonding layer 111 can be formed with
dielectric 113 including, but not limited to, silicon oxide,
silicon nitride, silicon oxynitride, low-k dielectrics, or any
combination thereof. Bonding contacts 112 and dielectric 113 in
bonding layer 111 can be used for hybrid bonding as described below
in detail.
[0041] In some embodiments, memory array device chip 160 is a NAND
Flash memory device in which memory cells are provided in the form
of an array of NAND memory strings 114 each extending vertically
above peripheral device layer 103. Memory array device layer 120
can include NAND memory strings 114 that extend vertically through
a plurality of pairs each including a conductor layer 116 and a
dielectric layer 118 (referred to herein as "conductor/dielectric
layer pairs"). The stacked conductor/dielectric layer pairs are
also referred to herein as a "memory stack." Conductor layers 116
and dielectric layers 118 in the memory can stack alternately in
the vertical direction.
[0042] As shown in FIG. 1, each NAND memory string 114 can include
a semiconductor channel 124 and a dielectric layer (also known as a
"memory film"). In some embodiments, semiconductor channel 124
includes silicon, such as amorphous silicon, polysilicon, or single
crystalline silicon. In some embodiments, the memory film is a
composite layer including a tunneling layer 126, a storage layer
128 (also known as a "charge trap/storage layer"), and a blocking
layer (not shown). Each NAND memory string 114 can have a cylinder
shape (e.g., a pillar shape). Semiconductor channel 124, tunneling
layer 126, storage layer 128, and the blocking layer are arranged
radially from the center toward the outer surface of the pillar in
this order, according to some embodiments. Tunneling layer 126 can
include silicon oxide, silicon oxynitride, or any combination
thereof. Storage layer 128 can include silicon nitride, silicon
oxynitride, silicon, or any combination thereof. The blocking layer
can include silicon oxide, silicon oxynitride, high dielectric
constant (high-k) dielectrics, or any combination thereof.
[0043] In some embodiments, NAND memory strings 114 further include
a plurality of control gates (each being part of a word line). Each
conductor layer 116 in the memory stack can act as a control gate
for memory cell of each NAND memory string 114. Each NAND memory
string 114 can include a source select gate at its upper end and a
drain select gate at its lower end. As used herein, the "upper end"
of a component (e.g., NAND memory string 114) is the end farther
away from substrate 102 in the y-direction, and the "lower end" of
the component (e.g., NAND memory string 114) is the end closer to
substrate 102 in the y-direction.
[0044] In some embodiments, memory array device chip 160 further
includes a semiconductor layer 130 disposed above and in contact
with NAND memory strings 114. Memory array device layer 120 can be
disposed below semiconductor layer 130. In some embodiments,
semiconductor layer 130 includes a plurality of semiconductor plugs
132 electrically separated by isolation regions. In some
embodiments, each semiconductor plug 132 is disposed at the upper
end of corresponding NAND memory string 114 and functions as the
drain of corresponding NAND memory string 114 and thus, can be
considered as part of corresponding NAND memory string 114.
Semiconductor plug 132 can include a single crystalline silicon.
Semiconductor plug 132 can be un-doped, partially doped (in the
thickness direction and/or the width direction), or fully doped by
p-type or n-type dopants.
[0045] In some embodiments, memory array device chip 160 includes
local interconnects that are formed in one or more ILD layers and
in contact with components in memory array device layer 120, such
as the word lines (e.g., conductor layers 116) and NAND memory
strings 114. The local interconnects can include word line via
contacts 136, source line via contacts 138, and bit line via
contacts 140. Each local interconnect can include conductive
materials including, but not limited to, W, Co, Cu, Al, silicides,
or any combination thereof. Word line via contacts 136 can extend
vertically through one or more ILD layers. Each word line via
contact 136 can be in contact with corresponding conductor layer
116 to individually address a corresponding word line of bonded
semiconductor device 100. Each source line via contact 138 can be
in contact with the source of corresponding NAND memory string 114.
Bit line via contacts 140 can extend vertically through one or more
ILD layers. Each bit line via contact 140 can electrically connect
to corresponding semiconductor plug 132 (e.g., the drain) of NAND
memory string 114 to individually address corresponding NAND memory
string 114.
[0046] Similar to peripheral device chip 162, memory array device
chip 160 can also include interconnect layers for transferring
electrical signals to and from NAND memory strings 114. As shown in
FIG. 1, memory array device chip 160 can include an interconnect
layer 142 (referred to herein as an "array interconnect layer")
below memory array device layer 120. Array interconnect layer 142
can include a plurality of interconnects 144, including
interconnect lines and via contacts in one or more ILD layers. As
described below in detail, interconnects 144 in array interconnect
layer 142 can include functional interconnects that are
electrically connected to NAND memory string 114 and optionally,
further include dummy interconnects that are not electrically
connected to any NAND memory string 114 in memory array device
layer 120.
[0047] As shown in FIG. 1, memory array device chip 160 can further
include a bonding layer 147 at bonding interface 158 and below
array interconnect layer 142 and memory array device layer 120.
Bonding layer 147 can include a plurality of bonding contacts 148
and a dielectric 149 electrically isolating bonding contacts 148.
Bonding contacts 148 can include functional bonding contacts 148-1,
each of which is part of an electrical connection between
peripheral device chip 162 and memory array device chip 160.
Bonding contacts 148 can also include dummy bonding contacts 148-2,
each of which is not part of any electrical connection between
peripheral device chip 162 and memory array device chip 160. As
described below in detail, dummy bonding contacts 148-2 can be used
for increasing the local density of bonding contacts 148 at bonding
interface 158 to increase bonding yield and strength. Bonding
contacts 148 can include conductive materials including, but not
limited to, W, Co, Cu, Al, silicides, or any combination thereof.
The remaining area of bonding layer 147 can be formed with
dielectric 149 including, but not limited to, silicon oxide,
silicon nitride, silicon oxynitride, low-k dielectrics, or any
combination thereof. Bonding contacts 148 and dielectric 149 in
bonding layer 147 can be used for hybrid bonding as described below
in detail.
[0048] As shown in FIG. 1, another interconnect layer 150 (referred
to herein as a "BEOL interconnect layer") can be disposed above
memory array device layer 120 and can include interconnects, such
as interconnect lines 152 and via contacts 154 in one or more ILD
layers. BEOL interconnect layer 150 can further include contact
pads 156 and a redistribution layer (not shown) at the top portion
of bonded semiconductor device 100 for wire bonding and/or bonding
with an interposer. BEOL interconnect layer 150 and array
interconnect layer 142 can be formed on opposite sides of memory
array device layer 120. In some embodiments, interconnect lines
152, via contacts 154, and contact pads 156 in BEOL interconnect
layer 150 can transfer electrical signals between bonded
semiconductor device 100 and external circuits.
[0049] As shown in FIG. 1, bonding interface 158 can be formed
between bonding layers 111 and 147. Bonding contacts 112 are in
contact with bonding contacts 148 at bonding interface 158, and
dielectric 113 is in contact with dielectric 149, according to some
embodiments. In some embodiments, a pair of functional bonding
contacts 112-1 and 148-1 are in contact with one another at bonding
interface 158, and pair of functional bonding contacts 112-1 and
148-1 are in contact with a pair of interconnects 108 and 144 on
opposite sides of bonding interface 158, respectively. In some
embodiments, a pair of dummy bonding contacts 112-2 and 148-2 are
in contact with one another at bonding interface 158 as well. As
dummy bonding contacts for improving metal density and uniformity
at bonding interface 158 for hybrid bonding, dummy bonding contacts
112-2 and 148-2 in pair are separated from the functional
interconnects on at least one side of bonding interface 158 (e.g.,
in peripheral interconnect layer 106 and/or array interconnect
layer 142) to avoid forming an electrical connection between memory
array device chip 160 and peripheral device chip 162. In some
embodiments, peripheral interconnect layer 106 and array
interconnect layer 142 include a pair of dummy interconnects that
are not electrically connected to NAND memory strings 114 and
transistors 104, and pair of dummy bonding contacts 112-2 and 148-2
can be in contact with the pair of dummy interconnects on the
opposite sides of bonding interface 158, respectively, without
forming an electrical connection between memory array device chip
160 and peripheral device chip 162. In some embodiments, a pair of
dielectrics 113 and 149 are in contact with one another at bonding
interface 158 as well.
[0050] FIGS. 2A and 2B illustrate cross-sections of various
exemplary bonded semiconductor devices including dummy bonding
contacts, according to various embodiments of the present
disclosure. FIG. 2A illustrates a bonded structure 200 including a
first semiconductor structure 202 and a second semiconductor
structure 204, according to some embodiments. As shown in FIG. 2A,
first semiconductor structure 202 is disposed below second
semiconductor structure 204 in bonded structure 200 and includes a
substrate 206, according to some embodiments. First semiconductor
structure 202 can also include a first device layer 208 above
substrate 206. In some embodiments, first semiconductor structure
202 is a peripheral device chip or a memory array device chip, and
first device layer 208 includes a peripheral device or a NAND
memory string, respectively, as described above in FIG. 1.
Similarly, second semiconductor structure 204 can include a second
device layer 222. In some embodiments, second semiconductor
structure 204 is a memory array device chip or a peripheral device
chip, and second device layer 222 includes a NAND memory string or
a peripheral device, respectively, as described above in FIG. 1.
Bonded structure 200 can further include a bonding interface 203
between first and second semiconductor structures 202 and 204. It
is understood that bonded structure 200 can include any other
suitable semiconductor devices, such as logic devices, volatile
memory devices (e.g., dynamic random-access memory (DRAM) and
static random-access memory (SRAM)), and non-volatile memory
devices (e.g., Flash memory), in a 2D, 2.5D, or 3D
architecture.
[0051] First semiconductor structure 202 can also include a first
interconnect layer 210 above first device layer 208. First
interconnect layer 210 includes interconnects 212 and 214 in one or
more ILD layers, according to some embodiments. Two types of
interconnects 212 and 214 can be formed in first interconnect layer
210 depending on their functionalities. In some embodiments, each
interconnect 212 is a functional MEOL or BEOL interconnect (e.g.,
interconnect line or via contact) that is electrically connected to
both first device layer 208 of first semiconductor structure 202
and second device layer 222 of second semiconductor structure 204
to transfer electrical signals across bonding interface 203 and
between first and second semiconductor structure 202 and 204.
Interconnect 214 can be a functional MEOL or BEOL interconnect
(e.g., interconnect line or via contact) that is electrically
connected to first device layer 208 of first semiconductor
structure 202, but not second device layer 222 of second
semiconductor structure 204, to transfer electrical signals within
first semiconductor structure 202. In some embodiments,
interconnect 214 is a dummy interconnect that is not electrically
connected to first device layer 208 of first semiconductor
structure 202. Interconnects 212 and 214 in first interconnect
layer 210 can include conductive materials including, but not
limited to, W, Co, Cu, Al, silicides, or any combination thereof.
The ILD layers in first interconnect layer 210 can include
dielectric materials including, but not limited to, silicon oxide,
silicon nitride, silicon oxynitride, low-k dielectrics, or any
combination thereof.
[0052] First semiconductor structure 202 can further include a
first bonding layer 216 above first interconnect layer 210. First
bonding layer 216 includes bonding contacts 218 and 220 in one ILD
layer, according to some embodiments. To reduce the fabrication
cost, first bonding layer 216 can be formed by a single patterning
process (e.g., involving only one photolithography and development
process) in a single ILD layer. As a result, in some embodiments,
each bonding contact 218 or 220 has a nominally same critical
dimension (e.g., the diameter of a via contact). In some
embodiments, each bonding contact 218 or 220 is a single damascene
contact, as opposed to a dual damascene contact. Two types of
bonding contacts 218 and 220 can be formed in first bonding layer
216 depending on whether it is part of an electrical connection
between first and second semiconductor structures 202 and 204. In
some embodiments, each bonding contact 218 is a functional bonding
contact that is part of an electrical connection across bonding
interface 203 and between first and second semiconductor structures
202 and 204. In some embodiments, bonding contact 220 is a dummy
bonding contact that is not part of an electrical connection across
bonding interface 203 and between first and second semiconductor
structures 202 and 204. Bonding contacts 218 and 220 in first
bonding layer 216 can include conductive materials including, but
not limited to, W, Co, Cu, Al, or any combination thereof. In some
embodiments, bonding contacts 218 and 220 are made of Cu for hybrid
bonding.
[0053] As described above, the density of bonding contacts can
affect the hybrid bonding. In addition to functional bonding
contacts 218 that are necessary for electrical interconnections,
the density of bonding contacts can be increased to improve the
hybrid bonding yield and strength by adding dummy bonding contacts
220 in first bonding layer 216. In some embodiments, to maximize
the bonding contact density in first bonding layer 216, each of
interconnects 212 and 214 is in contact with a respective one of
bonding contacts 218 and 220. For example, interconnects 212 and
214 in first interconnect layer 210 and bonding contacts 218 and
220 in first bonding layer 216 have a one-to-one mapping
relationship, and the number of bonding contacts 218 and 220 in
first bonding layer 216 is the same as the number of interconnects
212 and 214 in first interconnect layer 210. Each interconnect 212
or 214 can act as an etch stop layer for forming corresponding
bonding contact 218 or 220. In the areas without underneath
interconnects 212 and 214, no bonding contact 218 or 220 is formed
due to the lack of underneath etch stop layers (and all the bonding
contacts 218 and 220 in first bonding layer 216 are formed by a
single patterning process), according to some embodiments.
[0054] First bonding layer 216 can further include dielectrics 221
between and electrically isolating bonding contacts 218 and 220.
Dielectrics 221 in first bonding layer 216 can include dielectric
materials including, but not limited to, silicon oxide, silicon
nitride, silicon oxynitride, low-k dielectrics, or any combination
thereof. In some embodiments, dielectrics 221 are made of silicon
oxide for hybrid bonding.
[0055] On the opposite side of bonding interface 203, second
semiconductor structure 204 can also include a second interconnect
layer 224 below second device layer 222. Second interconnect layer
224 includes interconnects 226 and 228 in one or more ILD layers,
according to some embodiments. Two types of interconnects 226 and
228 can be formed in second interconnect layer 224 depending on
their functionalities. In some embodiments, each interconnect 226
is a functional MEOL or BEOL interconnect (e.g., interconnect line
or via contact) that is electrically connected to both first device
layer 208 of first semiconductor structure 202 and second device
layer 222 of second semiconductor structure 204 to transfer
electrical signals across bonding interface 203 and between first
and second semiconductor structure 202 and 204. Interconnect 228
can be a functional MEOL or BEOL interconnect (e.g., interconnect
line or via contact) that is electrically connected to second
device layer 222 of second semiconductor structure 204, but not
first device layer 208 of first semiconductor structure 202, to
transfer electrical signals within second semiconductor structure
204. In some embodiments, interconnect 228 is a dummy interconnect
that is not electrically connected to second device layer 222 of
second semiconductor structure 204. Interconnects 226 and 228 in
second interconnect layer 224 can include conductive materials
including, but not limited to, W, Co, Cu, Al, silicides, or any
combination thereof. The ILD layers in second interconnect layer
224 can include dielectric materials including, but not limited to,
silicon oxide, silicon nitride, silicon oxynitride, low-k
dielectrics, or any combination thereof.
[0056] Second semiconductor structure 204 can further include a
second bonding layer 230 below second interconnect layer 224.
Second bonding layer 230 includes bonding contacts 232, 234, and
236 in two ILD layers, according to some embodiments. Different
from first bonding layer 216, second bonding layer 230 can be
formed by two patterning processes (e.g., two photolithography and
development processes). As a result, bonding contacts 232, 234, and
236 in second bonding layer 230 can be formed in various designs.
In some embodiments, bonding contacts 232 are dual damascene
contacts, while bonding contacts 234 and 236 are single damascene
contacts. For example, by two patterning processes, bonding contact
232 can include a first portion 232-1 having a first critical
dimension in one ILD layer and a second portion 232-2 having a
second critical dimension different from the first critical
dimension in another ILD layer. As shown in FIG. 2A, first portion
232-1 of bonding contact 232 can be in contact with corresponding
interconnect 226 in second interconnect layer 224, and second
portion 232-2 of bonding contact 232 can be in contact with
corresponding bonding contact 218 on the opposite side of bonding
interface 203. Bonding contact 232 thus can be in contact with
corresponding interconnect 226 in second interconnect layer 224. In
contrast, bonding contacts 234 and 236 each does not include a
first portion in contact with any interconnect in second
interconnect layer 224, thereby being separated from interconnects
226 and 228 in second interconnect layer 224.
[0057] Two types of bonding contacts 232, 234, and 236 can be
formed in second bonding layer 230 depending on whether it is part
of an electrical connection between first and second semiconductor
structures 202 and 204. In some embodiments, each bonding contact
232 is a functional bonding contact that is part of an electrical
connection across bonding interface 203 and between first and
second semiconductor structures 202 and 204. In some embodiments,
bonding contact 234 or 236 is a dummy bonding contact that is not
part of an electrical connection across bonding interface 203 and
between first and second semiconductor structures 202 and 204.
Bonding contacts 232, 234, and 236 in second bonding layer 230 can
include conductive materials including, but not limited to, W, Co,
Cu, Al, or any combination thereof. In some embodiments, bonding
contacts 232, 234, and 236 are made of Cu for hybrid bonding.
[0058] As described above, the density of bonding contacts can
affect the hybrid bonding. In addition to functional bonding
contacts 232 that are necessary for electrical interconnections,
the density of bonding contacts can be increased to improve the
hybrid bonding yield and strength by adding dummy bonding contacts
234 in second bonding layer 230, which can form a high strength
Cu--Cu fusion bonding with corresponding dummy bonding contacts 220
at bonding interface 203. In some cases, dummy bonding contact 236
in second bonding layer 230 may not have a corresponding dummy
bonding contact in first bonding layer 216 on the opposite side of
bonding interface 203 due to the lack of an underneath interconnect
in first interconnect layer 210 to act as the etch stop layer. As a
result, a Cu--SiO.sub.2 bonding may be formed between dummy bonding
contact 236 and dielectric 221 as well. That is, each bonding
contact 218 or 220 in first bonding layer 216 is in contact with a
respective bonding contact 232 or 234 in second bonding layer 230
across bonding interface 203, while one or more bonding contacts
(e.g., dummy bonding contact 236) in second bonding layer 230 is
not in contact with any bonding contact in first bonding layer 216,
according to some embodiments. Thus, in some embodiments, the
number of bonding contacts 232, 234, and 236 in second bonding
layer 230 is greater than the number of bonding contacts 218 and
220 in first bonding layer 216.
[0059] Second bonding layer 230 can further include dielectrics 237
between and electrically isolating bonding contacts 232, 234, and
236. Dielectrics 237 in second bonding layer 230 can include
dielectric materials including, but not limited to, silicon oxide,
silicon nitride, silicon oxynitride, low-k dielectrics, or any
combination thereof. In some embodiments, dielectrics 237 are made
of silicon oxide for hybrid bonding.
[0060] As shown in FIG. 2A, in bonded structure 200, a pair of
functional bonding contacts 218 and 232 can be in contact with one
another at bonding interface 203 and also in contact with a pair of
interconnects 212 and 226 on opposite sides of bonding interface
203, respectively, to electrically connect the pair of
interconnects 212 and 226. An electrical connection can thus be
formed between the pair of interconnects 212 and 226 by the pair of
functional bonding contacts 218 and 232. The pair of functional
bonding contacts 218 and 232 also form a high strength Cu--Cu
fusion bonding at bonding interface 203, according to some
embodiments. On the other hand, in some embodiments. a pair of
dummy bonding contacts 220 and 234 are in contact with one another
at bonding interface 203 to form a high strength Cu--Cu fusion
bonding at bonding interface 203 as well. The pair of dummy bonding
contacts 220 and 234 are in contact with interconnect 214 (by dummy
bonding contact 220) on one side of bonding interface 203 but
separated from any interconnect 226 or 228 on the opposite side of
bonding interface 203, according to some embodiments, thereby
avoiding forming an electrical connection between interconnects
across bonding interface 203. In some embodiments, at least one
dummy bonding contact 236 is separated from any bonding contact 218
or 220 at bonding interface 203, and a pair of dummy bonding
contact 236 and dielectric 221 thus form a Cu--SiO.sub.2 bonding at
bonding interface 203. In some embodiments, the remaining areas of
first and second bonding layers 216 and 230, e.g., dielectrics 221
and 237, form SiO.sub.2--SiO.sub.2 covalent bonding at bonding
interface 203.
[0061] FIG. 2B illustrates a bonded structure 201 that is similar
to bonded structure 200 illustrated in FIG. 2A except that the
relative vertical positions of the components in first and second
semiconductor structures 202 and 204 are switched. In other words,
bonded structure 200 (except substrate 206) can be flipped
vertically along bonding interface 203 to become bonded structure
201. Nevertheless, dummy bonding contacts can be added to bonded
structures 200 and 201 to increase bonding contacts density (and
Cu--Cu fusion bonding in some embodiments) at bonding interface 203
to achieve better bonding performance. The design and arrangement
of dummy bonding contacts can accommodate the reduction of total
patterning processes in forming the dummy bonding contacts, thereby
reducing the fabrication cost. For example, on one side of bonding
interface 203, the bonding contacts can be all single damascene
contacts formed by a single patterning process.
[0062] FIG. 3 illustrates a cross-section of an exemplary bonded
structure 300 including dummy bonding contacts and dummy
interconnects, according to some embodiments of the present
disclosure. Different from bonded structures 200 and 201 in which
bonding contacts on only one side of the bonding interface are
single damascene contacts formed by a single patterning process, in
bonded structure 300 in FIG. 3, bonding contacts on both sides of a
bonding interface 303 between a first semiconductor structure 302
and a second semiconductor structure 304 can be single damascene
contacts formed by a single patterning process. By further reducing
the number of patterning processes for forming the bonding
contacts, the fabrication cost can be further decreased.
[0063] As shown in FIG. 3, first semiconductor structure 302 is
disposed below second semiconductor structure 304 in bonded
structure 300 and includes a substrate 306, according to some
embodiments. First semiconductor structure 302 can also include a
first device layer 308 above substrate 306. In some embodiments,
first semiconductor structure 302 is a peripheral device chip or a
memory array device chip, and first device layer 308 includes a
peripheral device or a NAND memory string, respectively, as
described above in FIG. 1. Similarly, second semiconductor
structure 304 can include a second device layer 322. In some
embodiments, second semiconductor structure 304 is a memory array
device chip or a peripheral device chip, and second device layer
322 includes a NAND memory string or a peripheral device,
respectively, as described above in FIG. 1.
[0064] First semiconductor structure 302 can also include a first
interconnect layer 310 above first device layer 308. First
interconnect layer 310 includes interconnects 312 and 314 in one or
more ILD layers, according to some embodiments. Two types of
interconnects 312 and 314 can be formed in first interconnect layer
310 depending on their functionalities. In some embodiments, each
interconnect 312 is a functional MEOL or BEOL interconnect (e.g.,
interconnect line or via contact) that is electrically connected to
both first device layer 308 of first semiconductor structure 302
and second device layer 322 of second semiconductor structure 304
to transfer electrical signals across bonding interface 303 and
between first and second semiconductor structure 302 and 304. In
some embodiments, each interconnect 314 is a dummy interconnect
that is not electrically connected to first device layer 308 (and
the peripheral device or NAND memory string therein for example) of
first semiconductor structure 302. As described below in detail,
dummy interconnects 314 can be added into first interconnect layer
310 in order to allow more dummy bonding contacts to be formed
thereabove, thereby further increasing the bonding contact density
at bonding interface 303. Interconnects 312 and 314 in first
interconnect layer 310 can include conductive materials including,
but not limited to, W, Co, Cu, Al, silicides, or any combination
thereof. The ILD layers in first interconnect layer 310 can include
dielectric materials including, but not limited to, silicon oxide,
silicon nitride, silicon oxynitride, low-k dielectrics, or any
combination thereof.
[0065] First semiconductor structure 302 can further include a
first bonding layer 316 above first interconnect layer 310. First
bonding layer 316 includes bonding contacts 318 and 320 in one ILD
layer, according to some embodiments. To reduce the fabrication
cost, first bonding layer 316 can be formed by a single patterning
process (e.g., involving only one photolithography and development
process) in a single ILD layer. As a result, in some embodiments,
each bonding contact 318 or 320 has a nominally same critical
dimension (e.g., the diameter of a via contact). In some
embodiments, each bonding contact 318 or 320 is a single damascene
contact, as opposed to a dual damascene contact. Two types of
bonding contacts 318 and 320 can be formed in first bonding layer
316 depending on whether it is part of an electrical connection
between first and second semiconductor structures 302 and 304. In
some embodiments, each bonding contact 318 is a functional bonding
contact that is in contact with corresponding functional
interconnect 312 and that is part of an electrical connection
across bonding interface 303 and between first and second
semiconductor structures 302 and 304. In some embodiments, bonding
contact 320 is a dummy bonding contact that is in contact with
corresponding dummy interconnect 314 and that is not part of an
electrical connection across bonding interface 303 and between
first and second semiconductor structures 302 and 304. Bonding
contacts 318 and 320 in first bonding layer 316 can include
conductive materials including, but not limited to, W, Co, Cu, Al,
or any combination thereof. In some embodiments, bonding contacts
318 and 320 are made of Cu for hybrid bonding.
[0066] As described above, the density of bonding contacts can
affect the hybrid bonding. In addition to functional bonding
contacts 318 that are necessary for electrical interconnections,
the density of bonding contacts can be increased to improve the
hybrid bonding yield and strength by adding dummy interconnects 314
in first interconnect layer 310 and corresponding dummy bonding
contacts 320 in first bonding layer 316. In some embodiments, to
maximize the bonding contact density in first bonding layer 316,
each of interconnects 312 and 314 is in contact with a respective
one of bonding contacts 318 and 320. For example, interconnects 312
and 314 in first interconnect layer 310 and bonding contacts 318
and 320 in first bonding layer 316 have a one-to-one mapping
relationship, and the number of bonding contacts 318 and 320 in
first bonding layer 316 is the same as the number of interconnects
312 and 314 in first interconnect layer 310. Each interconnect 312
or 314 can act as an etch stop layer for forming corresponding
bonding contact 318 or 320. In the areas without underneath
interconnects 312 and 314, no bonding contact 318 or 320 is formed
due to the lack of underneath etch stop layers (and all the bonding
contacts 318 and 320 in first bonding layer 316 are formed by a
single patterning process), according to some embodiments.
[0067] First bonding layer 316 can further include dielectrics 321
between and electrically isolating bonding contacts 318 and 320.
Dielectrics 321 in first bonding layer 316 can include dielectric
materials including, but not limited to, silicon oxide, silicon
nitride, silicon oxynitride, low-k dielectrics, or any combination
thereof. In some embodiments, dielectrics 321 are made of silicon
oxide for hybrid bonding.
[0068] On the opposite side of bonding interface 303, second
semiconductor structure 304 can also include a second interconnect
layer 324 below second device layer 322. Second interconnect layer
324 includes interconnects 326 and 328 in one or more ILD layers,
according to some embodiments Two types of interconnects 326 and
328 can be formed in second interconnect layer 324 depending on
their functionalities. In some embodiments, each interconnect 326
is a functional MEOL or BEOL interconnect (e.g., interconnect line
or via contact) that is electrically connected to both first device
layer 308 of first semiconductor structure 302 and second device
layer 322 of second semiconductor structure 304 to transfer
electrical signals across bonding interface 303 and between first
and second semiconductor structure 302 and 304. In some
embodiments, each interconnect 328 is a dummy interconnect that is
not electrically connected to second device layer 322 (and the
peripheral device or NAND memory string therein for example) of
second semiconductor structure 304. As described below in detail,
dummy interconnects 328 can be added into second interconnect layer
324 in order to allow more dummy bonding contacts to be formed
therebelow, thereby further increasing the bonding contact density
at bonding interface 303. Interconnects 326 and 328 in second
interconnect layer 324 can include conductive materials including,
but not limited to, W, Co, Cu, Al, silicides, or any combination
thereof. The ILD layers in second interconnect layer 324 can
include dielectric materials including, but not limited to, silicon
oxide, silicon nitride, silicon oxynitride, low-k dielectrics, or
any combination thereof.
[0069] Second semiconductor structure 304 can further include a
second bonding layer 330 below second interconnect layer 324.
Different from second bonding layer 230 in FIGS. 2A and 2B having
two ILD layers, second bonding layer 330 includes bonding contacts
332 and 334 in one ILD layer, according to some embodiments. To
reduce the fabrication cost, second bonding layer 330 can be formed
by a single patterning process (e.g., involving only one
photolithography and development process) in a single ILD layer as
well, just like first bonding layer 316 on the opposite side of
bonding interface 303. As a result, in some embodiments, each
bonding contact 332 or 334 has a nominally same critical dimension
(e.g., the diameter of a via contact). In some embodiments, each
bonding contact 332 or 334 is a single damascene contact, as
opposed to a dual damascene contact. Two types of bonding contacts
332 and 334 can be formed in second bonding layer 330 depending on
whether it is part of an electrical connection between first and
second semiconductor structures 302 and 304. In some embodiments,
each bonding contact 332 is a functional bonding contact that is in
contact with corresponding functional interconnect 326 and that is
part of an electrical connection across bonding interface 303 and
between first and second semiconductor structures 302 and 304. In
some embodiments, bonding contact 334 is a dummy bonding contact
that is in contact with corresponding dummy interconnect 328 and
that is not part of an electrical connection across bonding
interface 303 and between first and second semiconductor structures
302 and 304. Bonding contacts 332 and 334 in second bonding layer
330 can include conductive materials including, but not limited to,
W, Co, Cu, Al, or any combination thereof. In some embodiments,
bonding contacts 332 and 334 are made of Cu for hybrid bonding.
[0070] As described above, the density of bonding contacts can
affect the hybrid bonding. In addition to functional bonding
contacts 332 that are necessary for electrical interconnections,
the density of bonding contacts can be increased to improve the
hybrid bonding yield and strength by adding dummy interconnects 328
in second interconnect layer 324 and corresponding dummy bonding
contacts 334 in second bonding layer 330. In some embodiments, to
maximize the bonding contact density in second bonding layer 330,
each of interconnects 326 and 328 is in contact with a respective
one of bonding contacts 332 and 334. For example, interconnects 326
and 328 in second interconnect layer 324 and bonding contacts 332
and 334 in second bonding layer 330 have a one-to-one mapping
relationship, and the number of bonding contacts 332 and 334 in
second bonding layer 330 is the same as the number of interconnects
326 and 328 in second interconnect layer 324. Each interconnect 326
or 328 can act as an etch stop layer for forming corresponding
bonding contact 332 or 334. In the areas without underneath
interconnects 326 and 328, no bonding contact 332 or 334 is formed
due to the lack of underneath etch stop layers (and all the bonding
contacts 332 and 334 in second bonding layer 330 are formed by a
single patterning process), according to some embodiments.
[0071] Second bonding layer 330 can further include dielectrics 335
between and electrically isolating bonding contacts 332 and 334.
Dielectrics 335 in second bonding layer 330 can include dielectric
materials including, but not limited to, silicon oxide, silicon
nitride, silicon oxynitride, low-k dielectrics, or any combination
thereof. In some embodiments, dielectrics 335 are made of silicon
oxide for hybrid bonding.
[0072] Different from FIGS. 2A and 2B in which the number of
bonding contacts in second bonding layer 230 (formed by two
patterning processes) may be greater than the number of bonding
contacts in first bonding layer 216 (formed by a single patterning
process), in FIG. 3, the number of bonding contacts 332 and 334 in
second bonding layer 330 (formed by a single patterning process) is
the same as the number of bonding contacts in first bonding layer
316 (formed by a single patterning process). Each bonding contact
318 or 320 in first bonding layer 316 can be in contact with a
respective bonding contact 332 or 334 in second bonding layer 330
at bonding interface 303. In other words, the bonding contacts on
the opposite sides of bonding interface 303 have a one-to-one
mapping relationship, according to some embodiments. Because
functional bonding contacts 318 and 332 are paired and dummy
bonding contacts 320 and 334 are paired as well, no bonding contact
can be paired with dielectrics 321 or 335 to form, for example, a
Cu--SiO.sub.2 bonding. Consequently, the number of high strength
Cu--Cu bondings can be further increased at bonding interface 303
to improve the bonding performance.
[0073] As shown in FIG. 3, in bonded structure 300, a pair of
functional bonding contacts 318 and 332 can be in contact with one
another at bonding interface 303 and also in contact with a pair of
functional interconnects 312 and 326 on opposite sides of bonding
interface 303, respectively, to electrically connect the pair of
functional interconnects 312 and 326. An electrical connection can
thus be formed between the pair of functional interconnects 312 and
326 by the pair of functional bonding contacts 318 and 332. The
pair of functional bonding contacts 318 and 332 also form a high
strength Cu--Cu fusion bonding at bonding interface 303, according
to some embodiments. On the other hand, in some embodiments, a pair
of dummy bonding contacts 320 and 334 are in contact with one
another at bonding interface 303 to form a high strength Cu--Cu
fusion bonding at bonding interface 303 as well. The pair of dummy
bonding contacts 320 and 334 are in contact with a pair of dummy
interconnects 314 and 328 on opposite sides of bonding interface
303, according to some embodiments. In some embodiments, the
remaining areas of first and second bonding layers 316 and 330,
e.g., dielectrics 321 and 335, form a SiO.sub.2--SiO.sub.2 covalent
bonding at bonding interface 303.
[0074] By introducing dummy interconnects 314 and 328 on both sides
of bonding interface 303, the flexibility of arranging dummy
bonding contacts 320 and 332 can be increased. In some embodiments,
to further increase the hybrid bonding yield and strength, bonding
contacts on each side of bonding interface 303 are nominally evenly
disposed at bonding interface 303 in a plan view (not shown). In
some embodiments, the local density and/or global density of
bonding contacts can be adjusted to accommodate various designs of
bonded structure 300 by adding paired dummy interconnects and dummy
contacts accordingly.
[0075] It is understood that bonded structure 200, 201, or 300 can
include or be combined with other structures, such as device
layer(s), interconnect layer(s), and substrate(s), to form any
suitable semiconductor devices, for example, logic devices,
volatile memory devices (e.g., dynamic random-access memory (DRAM)
and static random-access memory (SRAM)), and non-volatile memory
devices (e.g., Flash memory), in a 2D, 2.5D, or 3D
architecture.
[0076] FIGS. 4A and 4B illustrate an exemplary fabrication process
for forming a first semiconductor structure including dummy bonding
contacts, according to some embodiments of the present disclosure.
FIGS. 5A-5C illustrate an exemplary fabrication process for forming
a second semiconductor structure including dummy bonding contacts,
according to some embodiments of the present disclosure. FIG. 6
illustrates an exemplary fabrication process for bonding the first
semiconductor structure and the second semiconductor structure,
according to some embodiments of the present disclosure. FIG. 10 is
a flowchart of a method for forming an exemplary bonded
semiconductor device including dummy bonding contacts, according to
some embodiments of the present disclosure. Examples of the bonded
semiconductor device depicted in FIGS. 4-6 and 10 include bonded
structures 200 and 201 depicted in FIGS. 2A and 2B. FIGS. 4-6 and
10 will be described together. It is understood that the operations
shown in method 1000 are not exhaustive and that other operations
can be performed as well before, after, or between any of the
illustrated operations. Further, some of the operations may be
performed simultaneously, or in a different order than shown in
FIGS. 4-6 and 10.
[0077] Referring to FIG. 10, method 1000 starts at operation 1002,
in which a first interconnect layer including a plurality of first
interconnects is formed above a first substrate. The first
substrate can be a silicon substrate. In some embodiments, a first
device layer is formed between the first substrate and the first
interconnect layer prior to forming the first interconnect layer.
The first device layer can include a NAND memory string or a
peripheral device.
[0078] As illustrated in FIG. 4A, a first device layer 404 is
formed above a silicon substrate 402. In some embodiments, first
device layer 404 is a peripheral device layer including a plurality
of transistors (not shown) formed on silicon substrate 402 by a
plurality of processes including, but not limited to,
photolithography, dry/wet etch, thin film deposition, thermal
growth, implantation, CMP, and any other suitable processes.
[0079] In some embodiments, first device layer 404 is a memory
array device layer including a plurality of NAND memory strings
(not shown) each extending vertically through a memory stack (not
shown) formed on silicon substrate 402. To form the memory stack, a
dielectric stack including an alternating stack of sacrificial
layers (e.g., silicon nitride) and dielectric layers (e.g., silicon
oxide) can be formed on silicon substrate 402 by one or more thin
film deposition processes including, but not limited to, CVD,
physical vapor deposition (PVD), atomic layer deposition (ALD), or
any combination thereof. The memory stack then can be formed on
silicon substrate 402 by gate replacement processes, i.e.,
replacing the sacrificial layers in the dielectric stack with
conductor layers. In some embodiments, fabrication processes to
form the NAND memory strings include forming a semiconductor
channel that extends vertically through the dielectric stack,
forming a composite dielectric layer (memory film) between the
semiconductor channel and the dielectric stack, including, but not
limited to, a tunneling layer, a storage layer, and a blocking
layer. The semiconductor channel and the memory film can be formed
by one or more thin film deposition processes such as ALD, CVD,
PVD, any other suitable processes, or any combination thereof.
[0080] As illustrated in FIG. 4A, a first interconnect layer 406 is
formed above first device layer 404. First interconnect layer 406
can include interconnects 408 and 410, including interconnect lines
and via contacts in one or more ILD layers, to make electrical
connections with first device layer 404. In some embodiments, first
interconnect layer 406 includes multiple ILD layers and
interconnects therein formed by multiple processes. For example,
interconnects 408 and 410 can include conductive materials
deposited by one or more thin film deposition processes including,
but not limited to, CVD, PVD, ALD, electrochemical depositions, or
any combination thereof. The ILD layers can include dielectric
materials deposited by one or more thin film deposition processes
including, but not limited to, CVD, PVD, ALD, or any combination
thereof.
[0081] Method 1000 proceeds to operation 1004, as illustrated in
FIG. 6, in which a first bonding layer including a plurality of
first bonding contacts is formed above the first interconnect
layer, such that each of the first interconnects is in contact with
a respective one of the first bonding contacts. A first dielectric
can be formed in the first bonding layer as well. In some
embodiments, the first bonding contacts in the first bonding layers
are formed by a single patterning process. In some embodiments, the
number of the first bonding contacts is the same as the number of
first interconnects. Each of the first bonding contacts has a
nominally same critical dimension, according to some
embodiments.
[0082] As illustrated in FIG. 4B, a layer of dielectric 411 is
deposited on the top surface of first interconnect layer 406 by a
thin film deposition process including, but not limited to, CVD,
PVD, ALD, or any combination thereof. Bonding contacts 414 and 416
are formed in dielectric 411 to form a first bonding layer 412
above first interconnect layer 406 and first device layer 404,
according to some embodiments. Bonding contact 414 and 416 can be
patterned by a single patterning process involving only one
photolithography process. In some embodiments, etch masks
(photoresist and/or hard masks) are patterned by a single
patterning process to expose dielectric 411 only at the areas where
interconnects 408 and 410 are formed underneath. Opening (e.g., a
via hole and/or a trench) then can be etched through first bonding
layer 412 until being stopped by underneath interconnects 408 and
410 as etch stop layers using dry etch and/or wet etch. Bonding
contacts 414 and 416 can include a barrier/adhesion layer and a
conductor (e.g., a metal) deposited subsequently in this order by
one or more thin film deposition processes including, but not
limited to, CVD, PVD, ALD, electrochemical depositions, or any
combination thereof, to fill the openings. The excess conductor can
be removed by CMP, and the top surface of first bonding layer 412
can be planarized for bonding.
[0083] Method 1000 proceeds to operation 1006, as illustrated in
FIG. 10, in which a second interconnect layer including a plurality
of second interconnects is formed above a second substrate. The
second substrate can be a silicon substrate. In some embodiments, a
second device layer is formed between the second substrate and the
second interconnect layer prior to forming the second interconnect
layer. The second device layer can include a peripheral device or a
NAND memory string.
[0084] As illustrated in FIG. 5A, a second device layer 504 is
formed above a silicon substrate 502. In some embodiments, second
device layer 504 is a memory array device layer including a
plurality of NAND memory strings (not shown) each extending
vertically through a memory stack (not shown) formed on silicon
substrate 502. The details of forming the memory array device layer
are described above and will not be repeated. In some embodiments,
second device layer 504 is a peripheral device layer including a
plurality of transistors (not shown) formed on silicon substrate
502 by a plurality of processes including, but not limited to,
photolithography, dry/wet etch, thin film deposition, thermal
growth, implantation, CMP, and any other suitable processes.
[0085] As illustrated in FIG. 5A, a second interconnect layer 506
is formed above second device layer 504. Second interconnect layer
506 can include interconnects 508, including interconnect lines and
via contacts in one or more ILD layers, to make electrical
connections with second device layer 504. In some embodiments,
second interconnect layer 506 includes multiple ILD layers and
interconnects therein formed by multiple processes. For example,
interconnects 508 can include conductive materials deposited by one
or more thin film deposition processes including, but not limited
to, CVD, PVD, ALD, electrochemical depositions, or any combination
thereof. The ILD layers can include dielectric materials deposited
by one or more thin film deposition processes including, but not
limited to, CVD, PVD, ALD, or any combination thereof.
[0086] Method 1000 proceeds to operation 1008, as illustrated in
FIG. 10, in which a second bonding layer including a plurality of
second bonding contacts is formed above the second interconnect
layer, such that at least one of the second bonding contacts is in
contact with a respective one of the second interconnects, and at
least another one of the second bonding contacts is separated from
the second interconnects. A second dielectric can be formed in the
second bonding layer as well. In some embodiments, the second
bonding contacts in the second bonding layers are formed by two
patterning processes. In some embodiments, to form the second
bonding layer, first portions of second bonding contacts are formed
above the second interconnects by one of the two patterning
processes, and second portions of second bonding contacts are
formed above the first portions of second bonding contacts by
another one of the two patterning processes. The number of the
second portions of second bonding contacts is greater than the
number of the first portions of second bonding contacts, according
to some embodiments.
[0087] As illustrated in FIG. 5B, a first layer of dielectric 509
is deposited on the top surface of second interconnect layer 506 by
a thin film deposition process including, but not limited to, CVD,
PVD, ALD, or any combination thereof. First portions of bonding
contact 512-1 are formed in dielectric 509 to form a first bonding
sub-layer 510-1 above second interconnect layer 506 and second
device layer 504, according to some embodiments. First portions of
bonding contact 512-1 can be patterned by a first patterning
process involving one photolithography process. In some
embodiments, etch masks (photoresist and/or hard masks) are
patterned by the first patterning process to expose dielectric 509
only at the areas where cross-chip electrical connections are to be
formed. Opening (e.g., a via hole and/or a trench) then can be
etched through first bonding sub-layer 510-1 until being stopped by
underneath interconnects 508 as etch stop layers using dry etch
and/or wet etch. First portions of bonding contact 512-1 can
include a barrier/adhesion layer and a conductor (e.g., a metal)
deposited subsequently in this order by one or more thin film
deposition processes including, but not limited to, CVD, PVD, ALD,
electrochemical depositions, or any combination thereof, to fill
the openings. The excess conductor can be removed by CMP, and the
top surface of first bonding sub-layer 510-1 can be planarized.
[0088] As illustrated in FIG. 5C, a second layer of dielectric 511
is deposited on the top surface of first bonding sub-layer 510-1 by
a thin film deposition process including, but not limited to, CVD,
PVD, ALD, or any combination thereof. Second portions of bonding
contact 512-2 and 514 are formed in dielectric 511 to form a second
bonding sub-layer 510-2 above first bonding sub-layer 510-1,
according to some embodiments. First and second bonding sub-layers
510-1 and 510-2 can together be referred to here as a second
bonding layer 510. Second portions of bonding contact 512-2 and 514
can be patterned by a second patterning process involving one
photolithography process. In some embodiments, etch masks
(photoresist and/or hard masks) are patterned by the second
patterning process to expose dielectric 511 at the areas where
first portions of bonding contacts 512-1 are formed underneath,
such that first and second portions of bonding contacts 512-1 and
512-2 can together form a functional bonding contact electrically
connected to underneath interconnects 508. Additionally, etch masks
(photoresist and/or hard masks) can be patterned by the second
patterning process to expose dielectric 511 at the areas where
dummy bonding contacts 514 can be formed to increase the bonding
performance. Opening (e.g., a via hole and/or a trench) then can be
etched through second bonding sub-layer 510-2 using dry etch and/or
wet etch. Second portions of bonding contacts 512-2 and 514 can
include a barrier/adhesion layer and a conductor (e.g., a metal)
deposited subsequently in this order by one or more thin film
deposition processes including, but not limited to, CVD, PVD, ALD,
electrochemical depositions, or any combination thereof, to fill
the openings. The excess conductor can be removed by CMP, and the
top surface of second bonding layer 510 can be planarized for
bonding.
[0089] Method 1000 proceeds to operation 1010, as illustrated in
FIG. 10, in which the first substrate and the second substrate are
bonded in a face-to-face manner, such that each of the first
bonding contacts is in contact with one of the second bonding
contacts at a bonding interface. The first dielectric can be in
contact with the second dielectric as well after the bonding. The
bonding can be hybrid bonding.
[0090] As illustrated in FIG. 6, silicon substrate 502 and second
device layer 504 formed thereon are flipped upside down. Second
bonding layer 510 facing down is to be bonded with first bonding
layer 412 facing up, i.e., in a face-to-face manner. In some
embodiments, bonding contacts 414 and 416 are aligned with bonding
contacts 512 and 514 prior to hybrid bonding, such that each
bonding contact 414 or 416 is in contact with one of bonding
contacts 512 and 514 at a bonding interface after the hybrid
bonding, according to some embodiments. In some embodiments, a
treatment process, e.g., a plasma treatment, a wet treatment,
and/or a thermal treatment, is applied to the bonding surfaces
prior to the hybrid bonding. As a result of the hybrid bonding,
bonding contacts 414 and 416 can be inter-mixed with bonding
contacts 512 and 514, and dielectric 411 can be covalent-bonded
with dielectric 511, thereby forming a bonding interface between
first bonding layer 412 and second bonding layer 510.
[0091] It is understood that although second bonding layer 510 is
flipped upside down and is above first bonding layer 412 in the
resulting bonded structure as shown in FIG. 6, in some embodiments,
first bonding layer 412 is flipped upside down and is above second
bonding layer 510 in the resulting bonded structure. In one
example, first device layer 404 can be a peripheral device layer,
and second device layer 504 can be a memory array device layer. In
another example, first device layer 404 can be a memory array
device layer, and second device layer 504 can be a peripheral
device layer. In still another example, first and second device
layers 404 and 504 can be both peripheral device layers. In yet
another example, first and second device layers 404 and 504 can be
both memory array device layers.
[0092] FIGS. 7A and 7B illustrate an exemplary fabrication process
for forming a first semiconductor structure including dummy bonding
contacts and dummy interconnects, according to some embodiments of
the present disclosure. FIGS. 8A and 8B illustrate an exemplary
fabrication process for forming a second semiconductor structure
including dummy bonding contacts and dummy interconnects, according
to some embodiments of the present disclosure. FIG. 9 illustrates
another exemplary fabrication process for bonding the first
semiconductor structure and the second semiconductor structure,
according to some embodiments of the present disclosure. FIG. 11 is
a flowchart of a method for forming an exemplary bonded
semiconductor device including dummy bonding contacts and dummy
interconnects, according to some embodiments of the present
disclosure. Examples of the bonded semiconductor device depicted in
FIGS. 7-9 and 11 include bonded structure 300 depicted in FIG. 3.
FIGS. 7-9 and 11 will be described together. It is understood that
the operations shown in method 1100 are not exhaustive and that
other operations can be performed as well before, after, or between
any of the illustrated operations. Further, some of the operations
may be performed simultaneously, or in a different order than shown
in FIGS. 7-9 and 11.
[0093] Referring to FIG. 11, method 1100 starts at operation 1102,
in which a first interconnect layer including a plurality of first
interconnects is formed above a first substrate. The first
substrate can be a silicon substrate. At least one of the first
interconnects can be at least one first dummy interconnect. In some
embodiments, a first device layer is formed between the first
substrate and the first interconnect layer prior to forming the
first interconnect layer. The first device layer can include a NAND
memory string or a peripheral device. The first dummy interconnect
is not electrically connected to the NAND memory string and the
peripheral device, according to some embodiments.
[0094] As illustrated in FIG. 7A, a first device layer 704 is
formed above a silicon substrate 702. In some embodiments, first
device layer 704 is a peripheral device layer including a plurality
of transistors (not shown) formed on silicon substrate 702 by a
plurality of processes including, but not limited to,
photolithography, dry/wet etch, thin film deposition, thermal
growth, implantation, CMP, and any other suitable processes. In
some embodiments, first device layer 704 is a memory array device
layer including a plurality of NAND memory strings (not shown) each
extending vertically through a memory stack (not shown) formed on
silicon substrate 702. The details of forming the memory array
device layer are described above and will not be repeated.
[0095] As illustrated in FIG. 7A, a first interconnect layer 706 is
formed above first device layer 704. First interconnect layer 706
can include functional interconnects 708 and dummy interconnects
710, including interconnect lines and via contacts in one or more
ILD layers. Functional interconnects 708 make electrical
connections with first device layer 704, while dummy interconnects
710 are not electrically connected to first device layer 704,
according to some embodiments. In some embodiments, first
interconnect layer 706 includes multiple ILD layers and
interconnects therein formed by multiple processes. For example,
interconnects 708 and 710 can include conductive materials
deposited by one or more thin film deposition processes including,
but not limited to, CVD, PVD, ALD, electrochemical depositions, or
any combination thereof. The ILD layers can include dielectric
materials deposited by one or more thin film deposition processes
including, but not limited to, CVD, PVD, ALD, or any combination
thereof.
[0096] Method 1100 proceeds to operation 1104, as illustrated in
FIG. 11, in which a first bonding layer including a plurality of
first bonding contacts is formed above the first interconnect
layer, such that each of the first interconnects is in contact with
a respective one of the first bonding contacts. A first dielectric
can be formed in the first bonding layer as well. In some
embodiments, the first bonding contacts in the first bonding layers
are formed by a single patterning process. In some embodiments, the
number of the first bonding contacts is the same as the number of
first interconnects. Each of the first bonding contacts has a
nominally same critical dimension, according to some
embodiments.
[0097] As illustrated in FIG. 7B, a layer of dielectric 711 is
deposited on the top surface of first interconnect layer 706 by a
thin film deposition process including, but not limited to, CVD,
PVD, ALD, or any combination thereof. Functional bonding contacts
714 and dummy bonding contacts 716 are formed in dielectric 711 to
form a first bonding layer 712 above first interconnect layer 706
and first device layer 704, according to some embodiments. Bonding
contacts 714 and 716 can be patterned by a single patterning
process involving only one photolithography process. In some
embodiments, etch masks (photoresist and/or hard masks) are
patterned by a single patterning process to expose dielectric 711
only at the areas where interconnects 708 and 710 are formed
underneath. Opening (e.g., a via hole and/or a trench) then can be
etched through first bonding layer 712 until being stopped by
underneath interconnects 708 and 710 as etch stop layers using dry
etch and/or wet etch. Bonding contacts 714 and 716 can include a
barrier/adhesion layer and a conductor (e.g., a metal) deposited
subsequently in this order by one or more thin film deposition
processes including, but not limited to, CVD, PVD, ALD,
electrochemical depositions, or any combination thereof, to fill
the openings. The excess conductor can be removed by CMP, and the
top surface of first bonding layer 712 can be planarized for
bonding.
[0098] Method 1100 proceeds to operation 1106, as illustrated in
FIG. 11, in which a second interconnect layer including a plurality
of second interconnects is formed above a second substrate. The
second substrate can be a silicon substrate. At least one of the
second interconnects can be at least one second dummy interconnect.
In some embodiments, a second device layer is formed between the
second substrate and the second interconnect layer prior to forming
the second interconnect layer. The second device layer can include
a NAND memory string or a peripheral device. The second dummy
interconnect is not electrically connected to the NAND memory
string and the peripheral device, according to some
embodiments.
[0099] As illustrated in FIG. 8A, a second device layer 804 is
formed above a silicon substrate 802. In some embodiments, second
device layer 804 is a peripheral device layer including a plurality
of transistors (not shown) formed on silicon substrate 802 by a
plurality of processes including, but not limited to,
photolithography, dry/wet etch, thin film deposition, thermal
growth, implantation, CMP, and any other suitable processes. In
some embodiments, second device layer 804 is a memory array device
layer including a plurality of NAND memory strings (not shown) each
extending vertically through a memory stack (not shown) formed on
silicon substrate 802. The details of forming the memory array
device layer are described above and will not be repeated.
[0100] As illustrated in FIG. 8A, a second interconnect layer 806
is formed above second device layer 804. Second interconnect layer
806 can include functional interconnects 808 and dummy
interconnects 810, including interconnect lines and via contacts in
one or more ILD layers. Functional interconnects 808 make
electrical connections with second device layer 804, while dummy
interconnects 810 are not electrically connected to second device
layer 804, according to some embodiments. In some embodiments,
second interconnect layer 806 includes multiple ILD layers and
interconnects therein formed by multiple processes. For example,
interconnects 808 and 810 can include conductive materials
deposited by one or more thin film deposition processes including,
but not limited to, CVD, PVD, ALD, electrochemical depositions, or
any combination thereof. The ILD layers can include dielectric
materials deposited by one or more thin film deposition processes
including, but not limited to, CVD, PVD, ALD, or any combination
thereof.
[0101] Method 1100 proceeds to operation 1108, as illustrated in
FIG. 11, in which a second bonding layer including a plurality of
second bonding contacts is formed above the second interconnect
layer, such that each of the second interconnects is in contact
with a respective one of the second bonding contacts. A second
dielectric can be formed in the second bonding layer as well. In
some embodiments, the second bonding contacts in the second bonding
layers are formed by a single patterning process. In some
embodiments, the number of the second bonding contacts is the same
as the number of the second interconnects. Each of the second
bonding contacts has a nominally same critical dimension, according
to some embodiments. In some embodiments, the number of the second
bonding contacts is the same as the number of the first bonding
contacts.
[0102] As illustrated in FIG. 8B, a layer of dielectric 811 is
deposited on the top surface of second interconnect layer 806 by a
thin film deposition process including, but not limited to, CVD,
PVD, ALD, or any combination thereof. Functional bonding contacts
814 and dummy bonding contacts 816 are formed in dielectric 811 to
form a second bonding layer 812 above second interconnect layer 806
and second device layer 804, according to some embodiments. Bonding
contacts 814 and 816 can be patterned by a single patterning
process involving only one photolithography process. In some
embodiments, etch masks (photoresist and/or hard masks) are
patterned by a single patterning process to expose dielectric 811
only at the areas where interconnects 808 and 810 are formed
underneath. Opening (e.g., a via hole and/or a trench) then can be
etched through second bonding layer 812 until being stopped by
underneath interconnects 808 and 810 as etch stop layers using dry
etch and/or wet etch. Bonding contacts 814 and 816 can include a
barrier/adhesion layer and a conductor (e.g., a metal) deposited
subsequently in this order by one or more thin film deposition
processes including, but not limited to, CVD, PVD, ALD,
electrochemical depositions, or any combination thereof, to fill
the openings. The excess conductor can be removed by CMP, and the
top surface of second bonding layer 812 can be planarized for
bonding.
[0103] Method 1100 proceeds to operation 1110, as illustrated in
FIG. 11, in which the first substrate and the second substrate are
bonded in a face-to-face manner, such that each of the first
bonding contacts is in contact with a respective one of the second
bonding contacts at a bonding interface. The first dielectric can
be in contact with the second dielectric as well after the bonding.
The bonding can be hybrid bonding.
[0104] As illustrated in FIG. 9, silicon substrate 702 and first
device layer 704 formed thereon are flipped upside down. First
bonding layer 712 facing down is to be bonded with second bonding
layer 812 facing up, i.e., in a face-to-face manner. In some
embodiments, bonding contacts 714 and 716 are aligned with bonding
contacts 814 and 816 prior to hybrid bonding, such that each
bonding contact 714 or 716 is in contact with corresponding bonding
contact 814 or 816 at a bonding interface after the hybrid bonding,
according to some embodiments. In some embodiments, a treatment
process, e.g., a plasma treatment, a wet treatment, and/or a
thermal treatment, is applied to the bonding surfaces prior to the
hybrid bonding. As a result of the hybrid bonding, bonding contacts
714 and 716 can be inter-mixed with bonding contacts 814 and 816,
and dielectric 711 can be covalent-bonded with dielectric 811,
thereby forming a bonding interface between first bonding layer 712
and second bonding layer 812.
[0105] According to one aspect of the present disclosure, a
semiconductor device includes a first semiconductor structure and a
second semiconductor structure. The first semiconductor structure
includes a first interconnect layer including a plurality of first
interconnects. At least one of the first interconnects is at least
one first dummy interconnect. The first semiconductor structure
further includes a first bonding layer including a plurality of
first bonding contacts. Each of the first interconnects is in
contact with a respective one of the first bonding contacts. The
second semiconductor structure includes a second interconnect layer
including a plurality of second interconnects. At least one of the
second interconnects is at least one second dummy interconnect. The
second semiconductor structure further includes a second bonding
layer including a plurality of second bonding contacts. Each of the
second interconnects is in contact with a respective one of the
second bonding contacts. The semiconductor device further includes
a bonding interface between the first bonding layer and the second
bonding layer. Each of the first bonding contacts is in contact
with a respective one of the second bonding contacts at the bonding
interface.
[0106] In some embodiments, a number of the first bonding contacts
is the same as a number of first interconnects, and a number of the
first bonding contacts is the same as a number of the first
interconnects.
[0107] In some embodiments, a number of the first dummy
interconnects is the same as a number of the second dummy
interconnects.
[0108] In some embodiments, each of the first bonding contacts has
a nominally same first critical dimension, and each of the second
bonding contacts has a nominally same second critical
dimension.
[0109] In some embodiments, the first and second bonding contacts
include a pair of dummy bonding contacts in contact with one
another at the bonding interface, and the pair of dummy bonding
contacts electrically connect a respective pair of first and second
dummy interconnects.
[0110] In some embodiments, the first bonding layer further
includes a first dielectric, and the second bonding layer further
includes a second dielectric in contact with the first dielectric
at the bonding interface.
[0111] In some embodiments, the first bonding contacts are
nominally evenly disposed at the bonding interface, and the second
bonding contacts are nominally evenly disposed at the bonding
interface.
[0112] In some embodiments, one of the first semiconductor
structure and the second semiconductor structure further includes a
device layer having a NAND memory string, and another one of the
first semiconductor structure and the second semiconductor
structure further includes a device layer having a peripheral
device.
[0113] In some embodiments, the first and second dummy
interconnects are not electrically connected to the NAND memory
string and the peripheral device.
[0114] According to another aspect of the present disclosure, a
bonded structure includes a bonding interface, a pair of functional
bonding contacts, and a pair of dummy bonding contacts. The pair of
functional bonding contacts are in contact with one another at the
bonding interface. The pair of bonding contacts are in contact with
a pair of functional interconnects on opposite sides of the bonding
interface, respectively. The pair of dummy bonding contacts are in
contact with one another at the bonding interface. The pair of
dummy bonding contacts are in contact with a pair of dummy
interconnects on the opposite sides of the bonding interface,
respectively.
[0115] In some embodiments, the bonded structure further includes a
pair of dielectrics in contact with one another at the bonding
interface.
[0116] According to still another aspect of the present disclosure,
a method for forming a semiconductor device is disclosed. A first
interconnect layer including a plurality of first interconnects is
formed above a first substrate. At least one of the first
interconnects is at least one first dummy interconnect. A first
bonding layer including a plurality of first bonding contacts is
formed above the first interconnect layer, such that each of the
first interconnects is in contact with a respective one of the
first bonding contacts. A second interconnect layer including a
plurality of second interconnects is formed above a second
substrate. At least one of the second interconnects is at least one
second dummy interconnect. A second bonding layer including a
plurality of second bonding contacts is formed above the second
interconnect layer, such that each of the second interconnects is
in contact with a respective one of the second bonding contacts.
The first substrate and the second substrate are bonded in a
face-to-face manner, such that each of the first bonding contacts
is in contact with a respective one of the second bonding contacts
at a bonding interface.
[0117] In some embodiments, to form the first bonding layer, the
first bonding contacts are formed by a single patterning process.
In some embodiments, to form the second bonding layer, the second
bonding contacts are formed by a single patterning process.
[0118] In some embodiments, a number of the first bonding contacts
is the same as a number of first interconnects, and a number of the
first bonding contacts is the same as a number of first
interconnects.
[0119] In some embodiments, each of the first bonding contacts has
a nominally same first critical dimension, and each of the second
bonding contacts has a nominally same second critical
dimension.
[0120] In some embodiments, to form the first bonding layer, a
first dielectric is formed in the first bonding layer. In some
embodiments, to form the second bonding layer, a second dielectric
is formed in the second bonding layer. The first dielectric is in
contact with the second dielectric at the bonding interface after
the bonding, according to some embodiments.
[0121] In some embodiments, a first device layer having a NAND
memory string is formed between the first interconnect layer and
the first substrate, and a second device layer having a peripheral
device between the second interconnect layer and the second
substrate. The first and second dummy interconnects are not
electrically connected to the NAND memory string and the peripheral
device, according to some embodiments.
[0122] In some embodiments, a first device layer having a
peripheral device is formed between the first interconnect layer
and the first substrate, and a second device layer having a NAND
memory string between the second interconnect layer and the second
substrate. The first and second dummy interconnects are not
electrically connected to the NAND memory string and the peripheral
device, according to some embodiments.
[0123] In some embodiments, the bonding includes hybrid
bonding.
[0124] The foregoing description of the specific embodiments will
so reveal the general nature of the present disclosure that others
can, by applying knowledge within the skill of the art, readily
modify and/or adapt for various applications such specific
embodiments, without undue experimentation, without departing from
the general concept of the present disclosure. Therefore, such
adaptations and modifications are intended to be within the meaning
and range of equivalents of the disclosed embodiments, based on the
teaching and guidance presented herein. It is to be understood that
the phraseology or terminology herein is for the purpose of
description and not of limitation, such that the terminology or
phraseology of the present specification is to be interpreted by
the skilled artisan in light of the teachings and guidance.
[0125] Embodiments of the present disclosure have been described
above with the aid of functional building blocks illustrating the
implementation of specified functions and relationships thereof.
The boundaries of these functional building blocks have been
arbitrarily defined herein for the convenience of the description.
Alternate boundaries can be defined so long as the specified
functions and relationships thereof are appropriately
performed.
[0126] The Summary and Abstract sections may set forth one or more
but not all exemplary embodiments of the present disclosure as
contemplated by the inventor(s), and thus, are not intended to
limit the present disclosure and the appended claims in any
way.
[0127] The breadth and scope of the present disclosure should not
be limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims and
their equivalents.
* * * * *