U.S. patent application number 15/457580 was filed with the patent office on 2018-09-13 for reducing resistance of bottom source/drain in vertical channel devices.
This patent application is currently assigned to International Business Machines Corporation. The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Shogo Mochizuki, Junli Wang.
Application Number | 20180261685 15/457580 |
Document ID | / |
Family ID | 63446595 |
Filed Date | 2018-09-13 |
United States Patent
Application |
20180261685 |
Kind Code |
A1 |
Mochizuki; Shogo ; et
al. |
September 13, 2018 |
REDUCING RESISTANCE OF BOTTOM SOURCE/DRAIN IN VERTICAL CHANNEL
DEVICES
Abstract
During a fabrication of a semiconductor device, a recess is
created in a substrate material disposed along a direction of a
plane of fabrication. A layer of a removable material is formed in
the recess. A bottom layer is formed above the layer of removable
material. A vertical channel above the bottom layer is formed in a
direction substantially orthogonal to the direction of the plane of
fabrication. A gate is formed using a metal above the bottom layer
and relative to the vertical channel. A tunnel is created under the
bottom layer by removing the removable material from under the
bottom layer such that the backside of the bottom layer forms a
ceiling of the tunnel. The tunnel is filled using a conductive
material such that the conductive material makes electrical contact
with the backside of the bottom layer.
Inventors: |
Mochizuki; Shogo; (Clifton
Park, NY) ; Wang; Junli; (Slingerlands, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Assignee: |
International Business Machines
Corporation
Armonk
NY
|
Family ID: |
63446595 |
Appl. No.: |
15/457580 |
Filed: |
March 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/823871 20130101;
H01L 29/78618 20130101; H01L 21/823885 20130101; H01L 29/66545
20130101; H01L 29/785 20130101; H01L 29/78642 20130101; H01L 29/456
20130101; H01L 29/6653 20130101; H01L 29/66666 20130101; H01L
29/41741 20130101; H01L 21/823814 20130101; H01L 29/42392 20130101;
H01L 29/78696 20130101; H01L 29/7827 20130101; H01L 29/66742
20130101 |
International
Class: |
H01L 29/66 20060101
H01L029/66; H01L 21/8238 20060101 H01L021/8238; H01L 29/45 20060101
H01L029/45 |
Claims
1. A method comprising: creating, during a fabrication of a
semiconductor device, in a substrate material disposed along a
direction of a plane of fabrication, a recess; forming, in the
recess, a layer of a removable material; forming, above the layer
of removable material, a bottom layer, wherein a backside of the
bottom layer is a side of the bottom layer that faces the layer of
removable material; forming, in a direction substantially
orthogonal to the direction of the plane of fabrication, a vertical
channel above the bottom layer; forming, above the bottom layer and
relative to the vertical channel, a gate using a metal; creating a
tunnel under the bottom layer by removing the removable material
from under the bottom layer such that the backside of the bottom
layer forms a ceiling of the tunnel; filling the tunnel using a
conductive material such that the conductive material makes
electrical contact with the backside of the bottom layer; and
electrically connecting a contact with the conductive material
filled in the tunnel to form an electrical connection with the
backside of the bottom layer.
2. The method of claim 1, further comprising: depositing, without
obstructing the tunnel, a metal on inside surfaces of the tunnel,
the depositing shrinking an opening of the tunnel but leaving the
tunnel open end-to-end, and wherein the filling occurs after the
depositing of the metal on the inside surfaces of the tunnel such
that the conductive material being filled makes electrical contact
with the deposited metal at least on the ceiling of the tunnel.
3. The method of claim 1, wherein the conductive material is a
silicide of a metal.
4. The method of claim 3, wherein the metal is one of Titanium,
Cobalt, Nickel, Nickel Platinum alloy, and Tungsten.
5. The method of claim 1, wherein the creating the tunnel occurs
after forming the gate, wherein the forming the gate employs a
temperature that is destructive to a second contact when the second
contact is placed on the bottom layer prior to the forming the
gate.
6. The method of claim 1, further comprising: forming a first
shallow trench isolation (STI) structure on one side of the bottom
layer and the layer of the removable material; forming a second STI
structure on an opposite side of the bottom layer and the layer of
the removable material; and exposing a third side of the layer of
removable material for the creating the tunnel.
7. The method of claim 1, further comprising: forming a hard mask
on top of the vertical channel; forming at least one spacer layer;
forming at least one high resistance (high-k) layer; and forming at
least one work function metal (WFM) layer.
8. The method of claim 1, further comprising: forming above the
vertical channel a top source/drain (S/D), wherein the bottom layer
is a bottom S/D, and wherein an electrical current flows between
the top S/D and the bottom S/D through the vertical channel in the
direction substantially orthogonal to the direction of the plane of
fabrication.
9. The method of claim 1, wherein the removable material is Silicon
Germanium (SiGe).
10. The method of claim 1, wherein the vertical channel device is a
vertical fin Field Effect Transistor (vertical finFET).
11. A computer usable program product comprising one or more
computer-readable storage devices, and program instructions stored
on at least one of the one or more storage devices, the stored
program instructions comprising: program instructions to create,
during a fabrication of a semiconductor device, in a substrate
material disposed along a direction of a plane of fabrication, a
recess; program instructions to form, in the recess, a layer of a
removable material; program instructions to form, above the layer
of removable material, a bottom layer, wherein a backside of the
bottom layer is a side of the bottom layer that faces the layer of
removable material; program instructions to form, in a direction
substantially orthogonal to the direction of the plane of
fabrication, a vertical channel above the bottom layer; program
instructions to form, above the bottom layer and relative to the
vertical channel, a gate using a metal; program instructions to
create a tunnel under the bottom layer by removing the removable
material from under the bottom layer such that the backside of the
bottom layer forms a ceiling of the tunnel; program instructions to
fill the tunnel using a conductive material such that the
conductive material makes electrical contact with the backside of
the bottom layer; and program instructions to electrically connect
a contact with the conductive material filled in the tunnel to form
an electrical connection with the backside of the bottom layer.
12. The computer usable program product of claim 11, further
comprising: program instructions to deposit, without obstructing
the tunnel, a metal on inside surfaces of the tunnel, the
depositing shrinking an opening of the tunnel but leaving the
tunnel open end-to-end, and wherein the filling occurs after the
depositing of the metal on the inside surfaces of the tunnel such
that the conductive material being filled makes electrical contact
with the deposited metal at least on the ceiling of the tunnel.
13. The computer usable program product of claim 11, wherein the
conductive material is a silicide of a metal.
14. The computer usable program product of claim 13, wherein the
metal is one of Titanium, Cobalt, Nickel, Nickel Platinum alloy,
and Tungsten.
15. The computer usable program product of claim 11, wherein the
program instructions to create the tunnel executes after the
program instructions to form the gate, wherein the program
instructions to form the gate employs a temperature that is
destructive to a second contact when the second contact is placed
on the bottom layer prior to the forming the gate.
16. The computer usable program product of claim 11, further
comprising: program instructions to form a first shallow trench
isolation (STI) structure on one side of the bottom layer and the
layer of the removable material; program instructions to form a
second STI structure on an opposite side of the bottom layer and
the layer of the removable material; and program instructions to
expose a third side of the layer of removable material for the
creating the tunnel.
17. The computer usable program product of claim 11, further
comprising: program instructions to form a hard mask on top of the
vertical channel; forming at least one spacer layer; program
instructions to form at least one high resistance (high-k) layer;
and program instructions to form at least one work function metal
(WFM) layer.
18. The computer usable program product of claim 11, wherein the
computer usable code is stored in a computer readable storage
device in a data processing system, and wherein the computer usable
code is transferred over a network from a remote data processing
system.
19. The computer usable program product of claim 11, wherein the
computer usable code is stored in a computer readable storage
device in a server data processing system, and wherein the computer
usable code is downloaded over a network to a remote data
processing system for use in a computer readable storage device
associated with the remote data processing system.
20. A computer system comprising one or more processors, one or
more computer-readable memories, and one or more computer-readable
storage devices, and program instructions stored on at least one of
the one or more storage devices for execution by at least one of
the one or more processors via at least one of the one or more
memories, the stored program instructions comprising: program
instructions to create, during a fabrication of a semiconductor
device, in a substrate material disposed along a direction of a
plane of fabrication, a recess; program instructions to form, in
the recess, a layer of a removable material; program instructions
to form, above the layer of removable material, a bottom layer,
wherein a backside of the bottom layer is a side of the bottom
layer that faces the layer of removable material; program
instructions to form, in a direction substantially orthogonal to
the direction of the plane of fabrication, a vertical channel above
the bottom layer; program instructions to form, above the bottom
layer and relative to the vertical channel, a gate using a metal;
program instructions to create a tunnel under the bottom layer by
removing the removable material from under the bottom layer such
that the backside of the bottom layer forms a ceiling of the
tunnel; program instructions to fill the tunnel using a conductive
material such that the conductive material makes electrical contact
with the backside of the bottom layer; and program instructions to
electrically connect a contact with the conductive material filled
in the tunnel to form an electrical connection with the backside of
the bottom layer.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to a method, system,
and computer program product for reducing the resistance of a
current path in vertical fin semiconductor devices. More
particularly, the present invention relates to a method, system,
and computer program product for reducing resistance of bottom
source/drain in vertical channel devices.
BACKGROUND
[0002] An integrated circuit (IC) is an electronic circuit formed
using a semiconductor material, such as Silicon, as a substrate and
by adding impurities to form solid-state semiconductor electronic
devices (device, devices), such as transistors, diodes, capacitors,
and resistors. Any reference to a "device" herein refers to a
solid-state semiconductor electronic device unless expressly
distinguished where used. Commonly known as a "chip" or a
"package," an integrated circuit is generally encased in hard
plastic, forming a "package." The components in modern day
electronics generally appear to be rectangular black plastic
packages with connector pins protruding from the plastic
encasement. Often, many such packages are electrically coupled so
that the chips therein form an electronic circuit to perform
certain functions.
[0003] The software tools used for designing ICs produce,
manipulate, or otherwise work with the circuit layout and circuit
components on very small scales. Some of the components that such a
tool may manipulate may only measure tens of nanometer across when
formed in Silicon. The designs produced and manipulated using these
software tools are complex, often including hundreds of thousands
of such components interconnected to form an intended electronic
circuitry.
[0004] A layout includes shapes that the designer selects and
positions to achieve a design objective. The objective is to have
the shape--the target shape--appear on the wafer as designed.
However, the shapes may not appear exactly as designed when
manufactured on the wafer through photolithography. For example, a
rectangular shape with sharp corners may appear as a rectangular
shape with rounded corners on the wafer.
[0005] Once a design layout, also referred to simply as a layout,
has been finalized for an IC, the design is converted into a set of
masks or reticles. A set of masks or reticles is one or more masks
or reticles. During manufacture, a semiconductor wafer is exposed
to light or radiation through a mask to form microscopic components
of the IC. This process is known as photolithography.
[0006] A manufacturing mask is a mask usable for successfully
manufacturing or printing the contents of the mask onto wafer.
During the photolithographic printing process, radiation is focused
through the mask and at certain desired intensity of the radiation.
This intensity of the radiation is commonly referred to as "dose".
The focus and the dosing of the radiation has to be precisely
controlled to achieve the desired shape and electrical
characteristics on the wafer.
[0007] A device generally uses several layers of different
materials to implement the device properties and function. A layer
of material can be conductive, semi-conductive, insulating,
resistive, capacitive, or have any number of other properties.
Different layers of materials have to be formed using different
methods, given the nature of the material, the shape, size or
placement of the material, other materials adjacent to the
material, and many other considerations.
[0008] The software tools used for designing ICs produce,
manipulate, or otherwise work with the circuit layout and circuit
components on very small scales. Some of the components that such a
tool may manipulate may only measure a few nanometers across when
formed in Silicon. The designs produced and manipulated using these
software tools are complex, often including hundreds of thousands
of such components interconnected to form an intended electronic
circuitry.
[0009] A Field Effect Transistor (FET) is a semiconductor device
that controls the electrical conductivity between a source of
electric current (source) and a destination of the electrical
current (drain). The FET uses a semiconductor structure called a
"gate" to create an electric field, which controls the shape and
consequently the electrical conductivity of a channel between the
source and the drain. The channel is a charge carrier pathway
constructed using a semiconductor material.
[0010] Many semiconductor devices are planar, i.e., where the
semiconductor structures are fabricated on one plane. A non-planar
device is a three-dimensional (3D) device where some of the
structures are formed above or below a given plane of
fabrication.
[0011] A fin-Field Effect Transistor (finFET) is a non-planar
device in which a source and a drain are connected using a
fin-shaped conducting channel (fin). A vertical channel device is a
device in which the current travels from a source to a drain in a
direction that is substantially orthogonal to the plane of
fabrication, e.g., the plane of the substrate material. A finFET
can be constructed as a vertical channel device whereby, a source
or drain (S/D) is formed in or near the plane of fabrication, a fin
is fabricated substantially perpendicular to the plane of
fabrication, and another S/D is fabricated above the fin. A finFET
with a vertical channel is referred to herein as a vertical
finFET.
[0012] The S/D that is in or near the plane of fabrication is
referred to herein as the bottom S/D. The other S/D is referred to
as the top S/D. The side of the bottom S/D that is facing the
substrate (and is opposite to the side connecting to the fin) is
referred to herein as the backside of the device.
[0013] In a FET, a gate controls the current flow between the two
S/D through the fin. The direction along the vertical length of the
fin (perpendicular to the plane of fabrication) running from one
S/D to the other S/D is referred to herein as a vertical running
direction of the fin. The direction of the current flowing between
the two S/D through the fin is therefore substantially
perpendicular to the plane of fabrication.
[0014] A CB contact is an electrical connection to a gate. A
circuit external to the finFET uses the CB contact to electrically
connect a part of the circuit to a gate in the finFET.
[0015] A TS contact is an electrical contact that provides
electrical connectivity to an S/D. A circuit external to the finFET
uses the TS contact to electrically connect a part of the circuit
to a S/D in a vertical finFET.
[0016] The illustrative embodiments recognize that the present
methods and techniques for fabricating a vertical finFET suffer
from several problems. For example, presently, the TS contact for
the bottom S/D is connected to the same side or surface of the
bottom S/D to which the fin is connected. This manner of placing
the TS contact is necessitated by the fact that once formed, the
backside of the bottom S/D not being accessible for TS contact
placement.
[0017] The illustrative embodiments recognize that placing the TS
contact on the same surface as the fin on the bottom S/D greatly
increases the distance the electrical current has to travel through
the bottom S/D. The current travels down the TS contact, down
through the bottom S/D, across the distance from the location of
the TS contact to the location of the fin, and up through the
bottom S/D to enter the fin. This down-and-up path through the
bottom S/D significantly increases the resistance faced by the
electrical current in the bottom S/D.
[0018] The illustrative embodiments recognize that if the TS
contact could be electrically connected to the backside of the
bottom S/D, the electrical current would only have to travel from
the TS contact up through the bottom S/D to enter the fin. Thus,
the electrical path through the bottom S/D, and consequently the
resistance of the bottom S/D would be significantly reduced.
Therefore, the illustrative embodiments recognize that some manner
of accessing the backside of the bottom S/D is desirable.
[0019] The illustrative embodiments further recognize that
accessing the backside of the bottom S/D is further exacerbated by
the gate fabrication process. Even though this is not how the
vertical channel devices are presently fabricated, even if some
connectivity were maintained with the backside of the bottom S/D
during the fabrication process, the gate construction step would
destroy or damage such connectivity. The illustrative embodiments
recognize that gates use a metal, and the fabrication of the gate
is a high temperature step that would be detrimental to any
connecting apparatus that could be pre-fabricated at the backside
of the bottom S/D.
[0020] Therefore, any connectivity to the backside of the bottom
S/D should be fabricated after the gates have been fabricated.
Therefore, a method for fabricating access to the backside of the
bottom S/D after the gates have been fabricated would be
desirable.
SUMMARY
[0021] The illustrative embodiments provide a method, system, and
computer program product. An embodiment includes a method that
creates, during a fabrication of a semiconductor device, in a
substrate material disposed along a direction of a plane of
fabrication, a recess. The embodiment forms, in the recess, a layer
of a removable material. The embodiment forms, above the layer of
removable material, a bottom layer, wherein a backside of the
bottom layer is a side of the bottom layer that faces the layer of
removable material. The embodiment forms, in a direction
substantially orthogonal to the direction of the plane of
fabrication, a vertical channel above the bottom layer. The
embodiment forma, above the bottom layer and relative to the
vertical channel, a gate using a metal. The embodiment creates a
tunnel under the bottom layer by removing the removable material
from under the bottom layer such that the backside of the bottom
layer forms a ceiling of the tunnel. The embodiment fills the
tunnel using a conductive material such that the conductive
material makes electrical contact with the backside of the bottom
layer. The embodiment electrically connects a contact with the
conductive material filled in the tunnel to form an electrical
connection with the backside of the bottom layer. Thus, the
embodiment enables a reduction in a path of a current, thereby
reducing the resistance of the bottom S/D of a vertical channel
device.
[0022] Another embodiment further deposits, without obstructing the
tunnel, a metal on inside surfaces of the tunnel, the depositing
shrinking an opening of the tunnel but leaving the tunnel open
end-to-end, and wherein the filling occurs after the depositing of
the metal on the inside surfaces of the tunnel such that the
conductive material being filled makes electrical contact with the
deposited metal at least on the ceiling of the tunnel. Thus, the
embodiment improves the ability to fill the tunnel with the
conductive material.
[0023] In another embodiment, the conductive material is a silicide
of a metal. Thus, the embodiment allows the tunnel to be filled
with a presently known and used the conductive material.
[0024] In another embodiment, the creating the tunnel occurs after
forming the gate, wherein the forming the gate employs a
temperature that is destructive to a second contact when the second
contact is placed on the bottom layer prior to the forming the
gate. Thus, the embodiment prevents the destruction of the
connectivity to the backside of the bottom S/D.
[0025] Another embodiment further forms a first shallow trench
isolation (STI) structure on one side of the bottom layer and the
layer of the removable material. The embodiment forms a second STI
structure on an opposite side of the bottom layer and the layer of
the removable material. The embodiment exposes a third side of the
layer of removable material for the creating the tunnel. Thus, the
embodiment enables the formation of the tunnel in a specific
manner.
[0026] Another embodiment further forms a hard mask on top of the
vertical channel. The embodiment forms at least one spacer layer.
The embodiment forms at least one high resistance (high-k) layer.
The embodiment forms at least one work function metal (WFM) layer.
Thus, the embodiment enables forming a fin as a vertical channel
device.
[0027] Another embodiment further forms above the vertical channel
a top source/drain (S/D), wherein the bottom layer is a bottom S/D,
and wherein an electrical current flows between the top S/D and the
bottom S/D through the vertical channel in the direction
substantially orthogonal to the direction of the plane of
fabrication. Thus, the embodiment limits the current flow through
the bottom S/D to a single vertical traversal through the bottom
S/D before reaching from a contact to the vertical channel.
[0028] In an embodiment, the removable material is Silicon
Germanium (SiGe). Thus, the embodiment allows a presently known
material to be used as the removable material.
[0029] In another embodiment, the vertical channel device is a
vertical fin Field Effect Transistor (vertical finFET). Thus, the
embodiment enables the fabrication of a specific type of vertical
channel semiconductor device.
[0030] An embodiment includes a computer usable program product.
The computer usable program product includes one or more
computer-readable storage devices, and program instructions stored
on at least one of the one or more storage devices.
[0031] An embodiment includes a computer system. The computer
system includes one or more processors, one or more
computer-readable memories, and one or more computer-readable
storage devices, and program instructions stored on at least one of
the one or more storage devices for execution by at least one of
the one or more processors via at least one of the one or more
memories.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The novel features believed characteristic of the invention
are set forth in the appended claims. The invention itself,
however, as well as a preferred mode of use, further objectives and
advantages thereof, will best be understood by reference to the
following detailed description of the illustrative embodiments when
read in conjunction with the accompanying drawings, wherein:
[0033] FIG. 1 depicts a block diagram of a network of data
processing systems in which illustrative embodiments may be
implemented;
[0034] FIG. 2 depicts a block diagram of a data processing system
in which illustrative embodiments may be implemented;
[0035] FIG. 3 depicts a block diagram of a portion of an example
process for fabricating an example vertical channel finFET device
in accordance with an illustrative embodiment;
[0036] FIG. 4 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0037] FIG. 5 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0038] FIG. 6 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0039] FIG. 7 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0040] FIG. 8A depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0041] FIG. 8B depicts another three-dimensional view of the filled
tunnel in accordance with an illustrative embodiment;
[0042] FIG. 9 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0043] FIG. 10 depicts a block diagram of another portion of an
example process for fabricating an example vertical channel finFET
device in accordance with an illustrative embodiment;
[0044] FIG. 11 depicts a block diagram of an example process for
fabricating multiple vertical channel devices with reduced bottom
S/D resistance in accordance with an illustrative embodiment;
and
[0045] FIG. 12 depicts a flowchart of an example process for
reducing resistance of bottom source/drain in vertical channel
devices in accordance with an illustrative embodiment.
DETAILED DESCRIPTION
[0046] The illustrative embodiments used to describe the invention
generally address and solve the above-described problems and other
problems related to resistance of a bottom S/D in a vertical
channel finFET. The illustrative embodiments provide a fabrication
method for finFET devices that reduces the resistance of the bottom
S/D by creating a crating a hollow tunnel from a removable layer
under the bottom S/D and filling the tunnel with a suitable
conductive material, which is in electrical contact with the
backside of the bottom S/D, and to which the TS contact can be
electrically coupled.
[0047] An embodiment can be implemented as a software application.
The application implementing an embodiment can be configured as a
modification of an existing semiconductor fabrication system--such
as a photolithography system, as a separate application that
operates in conjunction with an existing semiconductor fabrication
system, a standalone application, or some combination thereof. For
example, the application causes the semiconductor fabrication
system to perform the steps described herein, to fabricate a finFET
in which an electrical contact is attached to the backside of a
bottom S/D in a vertical channel device, as described herein.
[0048] For the clarity of the description, and without implying any
limitation thereto, the illustrative embodiments are described
using a vertical channel finFET where a single vertical fin couples
the bottom S/D and the top S/D. An embodiment can be implemented
with a different number of gates, different number of fins, or
both, within the scope of the illustrative embodiments. An
embodiment can be implemented with other types of vertical channel
devices, other types of contacts that have to be placed on the
backside of a layer facing the substrate or another layer.
[0049] Furthermore, a simplified diagram of the example vertical
finFET is used in the figures and the illustrative embodiments. In
an actual fabrication of a vertical finFET, additional structures
that are not shown or described herein, or structures different
from those shown and described herein, may be present without
departing the scope of the illustrative embodiments. Similarly,
within the scope of the illustrative embodiments, a shown or
described structure in the example finFET may be fabricated
differently to yield a similar operation or result as described
herein.
[0050] Differently shaded portions in the two-dimensional drawing
of the example finFET are intended to represent different
structures in the example finFET, as described herein. The
different structures may be fabricated using suitable materials
that are known to those of ordinary skill in the art.
[0051] A specific shape or dimension of a shape depicted herein is
not intended to be limiting on the illustrative embodiments. The
shapes and dimensions are chosen only for the clarity of the
drawings and the description and may have been exaggerated,
minimized, or otherwise changed from actual shapes and dimensions
that might be used in actually fabricating a finFET according to
the illustrative embodiments.
[0052] Furthermore, the illustrative embodiments are described with
respect to a finFET only as an example. The steps described by the
various illustrative embodiments can be adapted for fabricating
other planar and non-planar devices in a similar manner, and such
adaptations are contemplated within the scope of the illustrative
embodiments. The specific contacts placements are also used only as
non-limiting examples to describe the various operations of the
illustrative embodiments. Those of ordinary skill in the art will
be able to use an embodiment to similarly provide access to the
backside of a layer for other purposes in a similar manner, and
such usage is also contemplated within the scope of the
illustrative embodiments.
[0053] An embodiment when implemented in an application causes a
fabrication process to performs certain steps as described herein.
The steps of the fabrication process are depicted in the several
figures. Not all steps may be necessary in a particular fabrication
process. Some fabrication processes may implement the steps in
different order, combine certain steps, remove or replace certain
steps, or perform some combination of these and other manipulations
of steps, without departing the scope of the illustrative
embodiments.
[0054] A method of an embodiment described herein, when implemented
to execute on a device or data processing system, comprises
substantial advancement of the functionality of that device or data
processing system in fabricating vertical channel devices with
accessibility to the backside of a bottom layer. A manner of
accessing the backside of a bottom layer without exposure to the
high temperature steps during the fabrication is unavailable in the
presently available methods. Thus, a substantial advancement of
such devices or data processing systems by executing a method of an
embodiment is in an improved fabrication of vertical channel
devices where the backside of a bottom layer becomes accessible
after the gate formation, the resistance offered by the bottom
layer is reduced, or both.
[0055] The illustrative embodiments are described with respect to
certain types of devices, electrical properties, contacts, layers,
planes, structures, materials, dimensions, numerosity, data
processing systems, environments, components, and applications only
as examples. Any specific manifestations of these and other similar
artifacts are not intended to be limiting to the invention. Any
suitable manifestation of these and other similar artifacts can be
selected within the scope of the illustrative embodiments.
[0056] Furthermore, the illustrative embodiments may be implemented
with respect to any type of data, data source, or access to a data
source over a data network. Any type of data storage device may
provide the data to an embodiment of the invention, either locally
at a data processing system or over a data network, within the
scope of the invention. Where an embodiment is described using a
mobile device, any type of data storage device suitable for use
with the mobile device may provide the data to such embodiment,
either locally at the mobile device or over a data network, within
the scope of the illustrative embodiments.
[0057] The illustrative embodiments are described using specific
code, designs, architectures, protocols, layouts, schematics, and
tools only as examples and are not limiting to the illustrative
embodiments. Furthermore, the illustrative embodiments are
described in some instances using particular software, tools, and
data processing environments only as an example for the clarity of
the description. The illustrative embodiments may be used in
conjunction with other comparable or similarly purposed structures,
systems, applications, or architectures. For example, other
comparable mobile devices, structures, systems, applications, or
architectures therefor, may be used in conjunction with such
embodiment of the invention within the scope of the invention. An
illustrative embodiment may be implemented in hardware, software,
or a combination thereof.
[0058] The examples in this disclosure are used only for the
clarity of the description and are not limiting to the illustrative
embodiments. Additional data, operations, actions, tasks,
activities, and manipulations will be conceivable from this
disclosure and the same are contemplated within the scope of the
illustrative embodiments.
[0059] Any advantages listed herein are only examples and are not
intended to be limiting to the illustrative embodiments. Additional
or different advantages may be realized by specific illustrative
embodiments. Furthermore, a particular illustrative embodiment may
have some, all, or none of the advantages listed above.
[0060] With reference to the figures and in particular with
reference to FIGS. 1 and 2, these figures are example diagrams of
data processing environments in which illustrative embodiments may
be implemented. FIGS. 1 and 2 are only examples and are not
intended to assert or imply any limitation with regard to the
environments in which different embodiments may be implemented. A
particular implementation may make many modifications to the
depicted environments based on the following description.
[0061] FIG. 1 depicts a block diagram of a network of data
processing systems in which illustrative embodiments may be
implemented. Data processing environment 100 is a network of
computers in which the illustrative embodiments may be implemented.
Data processing environment 100 includes network 102. Network 102
is the medium used to provide communications links between various
devices and computers connected together within data processing
environment 100. Network 102 may include connections, such as wire,
wireless communication links, or fiber optic cables.
[0062] Clients or servers are only example roles of certain data
processing systems connected to network 102 and are not intended to
exclude other configurations or roles for these data processing
systems. Server 104 and server 106 couple to network 102 along with
storage unit 108. Software applications may execute on any computer
in data processing environment 100. Clients 110, 112, and 114 are
also coupled to network 102. A data processing system, such as
server 104 or 106, or client 110, 112, or 114 may contain data and
may have software applications or software tools executing
thereon.
[0063] Only as an example, and without implying any limitation to
such architecture, FIG. 1 depicts certain components that are
usable in an example implementation of an embodiment. For example,
servers 104 and 106, and clients 110, 112, 114, are depicted as
servers and clients only as example and not to imply a limitation
to a client-server architecture. As another example, an embodiment
can be distributed across several data processing systems and a
data network as shown, whereas another embodiment can be
implemented on a single data processing system within the scope of
the illustrative embodiments. Data processing systems 104, 106,
110, 112, and 114 also represent example nodes in a cluster,
partitions, and other configurations suitable for implementing an
embodiment.
[0064] Device 132 is an example of a data processing device or a
portable device usable for computing or communications purposes
described herein. For example, device 132 can take the form of a
smartphone, a tablet computer, a laptop computer, client 110 in a
stationary or a portable form, a wearable computing device, or any
other suitable device. Any software application described as
executing in another data processing system in FIG. 1 can be
configured to execute in device 132 in a similar manner. Any data
or information stored or produced in another data processing system
in FIG. 1 can be configured to be stored or produced in device 132
in a similar manner.
[0065] Application 105 implements an embodiment described herein.
Fabrication system 107 is any suitable system for fabricating a
semiconductor device. Application 105 provides instructions to
system 107 for fabricating a vertical channel semiconductor device
where the backside of a bottom layer--such as the backside of a
bottom S/D in a vertical finFET--is accessible for making
electrical contact, where the accessibility mechanism for such
backside access is unaffected by a high temperature step in the
fabrication of the device, or a combination thereof, in a manner
described herein.
[0066] Servers 104 and 106, storage unit 108, and clients 110, 112,
and 114 may couple to network 102 using wired connections, wireless
communication protocols, or other suitable data connectivity.
Clients 110, 112, and 114 may be, for example, personal computers
or network computers.
[0067] In the depicted example, server 104 may provide data, such
as boot files, operating system images, and applications to clients
110, 112, and 114. Clients 110, 112, and 114 may be clients to
server 104 in this example. Clients 110, 112, 114, or some
combination thereof, may include their own data, boot files,
operating system images, and applications. Data processing
environment 100 may include additional servers, clients, and other
devices that are not shown.
[0068] In the depicted example, data processing environment 100 may
be the Internet. Network 102 may represent a collection of networks
and gateways that use the Transmission Control Protocol/Internet
Protocol (TCP/IP) and other protocols to communicate with one
another. At the heart of the Internet is a backbone of data
communication links between major nodes or host computers,
including thousands of commercial, governmental, educational, and
other computer systems that route data and messages. Of course,
data processing environment 100 also may be implemented as a number
of different types of networks, such as for example, an intranet, a
local area network (LAN), or a wide area network (WAN). FIG. 1 is
intended as an example, and not as an architectural limitation for
the different illustrative embodiments.
[0069] Among other uses, data processing environment 100 may be
used for implementing a client-server environment in which the
illustrative embodiments may be implemented. A client-server
environment enables software applications and data to be
distributed across a network such that an application functions by
using the interactivity between a client data processing system and
a server data processing system. Data processing environment 100
may also employ a service oriented architecture where interoperable
software components distributed across a network may be packaged
together as coherent business applications.
[0070] With reference to FIG. 2, this figure depicts a block
diagram of a data processing system in which illustrative
embodiments may be implemented. Data processing system 200 is an
example of a computer, such as servers 104 and 106, or clients 110,
112, and 114 in FIG. 1, or another type of device in which computer
usable program code or instructions implementing the processes may
be located for the illustrative embodiments.
[0071] Data processing system 200 is also representative of a data
processing system or a configuration therein, such as data
processing system 132 in FIG. 1 in which computer usable program
code or instructions implementing the processes of the illustrative
embodiments may be located. Data processing system 200 is described
as a computer only as an example, without being limited thereto.
Implementations in the form of other data processing devices, such
as mobile device 132 in FIG. 1, may modify data processing system
200, such as by adding a touch interface, and even eliminate
certain depicted components from data processing system 200 without
departing from the general description of the operations and
functions of data processing system 200 described herein.
[0072] In the depicted example, data processing system 200 employs
a hub architecture including North Bridge and memory controller hub
(NB/MCH) 202 and South Bridge and input/output (I/O) controller hub
(SB/ICH) 204. Processing unit 206, main memory 208, and graphics
processor 210 are coupled to North Bridge and memory controller hub
(NB/MCH) 202. Processing unit 206 may contain one or more
processors and may be implemented using one or more heterogeneous
processor systems. Processing unit 206 may be a multi-core
processor. Graphics processor 210 may be coupled to NB/MCH 202
through an accelerated graphics port (AGP) in certain
implementations.
[0073] In the depicted example, local area network (LAN) adapter
212 is coupled to South Bridge and I/O controller hub (SB/ICH) 204.
Audio adapter 216, keyboard and mouse adapter 220, modem 222, read
only memory (ROM) 224, universal serial bus (USB) and other ports
232, and PCI/PCIe devices 234 are coupled to South Bridge and I/O
controller hub 204 through bus 238. Hard disk drive (HDD) or
solid-state drive (SSD) 226 and CD-ROM 230 are coupled to South
Bridge and I/O controller hub 204 through bus 240. PCI/PCIe devices
234 may include, for example, Ethernet adapters, add-in cards, and
PC cards for notebook computers. PCI uses a card bus controller,
while PCIe does not. ROM 224 may be, for example, a flash binary
input/output system (BIOS). Hard disk drive 226 and CD-ROM 230 may
use, for example, an integrated drive electronics (IDE), serial
advanced technology attachment (SATA) interface, or variants such
as external-SATA (eSATA) and micro-SATA (mSATA). A super I/O (SIO)
device 236 may be coupled to South Bridge and I/O controller hub
(SB/ICH) 204 through bus 238.
[0074] Memories, such as main memory 208, ROM 224, or flash memory
(not shown), are some examples of computer usable storage devices.
Hard disk drive or solid state drive 226, CD-ROM 230, and other
similarly usable devices are some examples of computer usable
storage devices including a computer usable storage medium.
[0075] An operating system runs on processing unit 206. The
operating system coordinates and provides control of various
components within data processing system 200 in FIG. 2. The
operating system may be a commercially available operating system
such as AIX.RTM. (AIX is a trademark of International Business
Machines Corporation in the United States and other countries),
Microsoft.RTM. Windows.RTM. (Microsoft and Windows are trademarks
of Microsoft Corporation in the United States and other countries),
Linux.RTM. (Linux is a trademark of Linus Torvalds in the United
States and other countries), iOS.TM. (iOS is a trademark of Cisco
Systems, Inc. licensed to Apple Inc. in the United States and in
other countries), or Android.TM. (Android is a trademark of Google
Inc., in the United States and in other countries). An object
oriented programming system, such as the Java.TM. programming
system, may run in conjunction with the operating system and
provide calls to the operating system from Java.TM. programs or
applications executing on data processing system 200 (Java and all
Java-based trademarks and logos are trademarks or registered
trademarks of Oracle Corporation and/or its affiliates).
[0076] Instructions for the operating system, the object-oriented
programming system, and applications or programs, such as
application 105 in FIG. 1, are located on storage devices, such as
in the form of code 226A on hard disk drive 226, and may be loaded
into at least one of one or more memories, such as main memory 208,
for execution by processing unit 206. The processes of the
illustrative embodiments may be performed by processing unit 206
using computer implemented instructions, which may be located in a
memory, such as, for example, main memory 208, read only memory
224, or in one or more peripheral devices.
[0077] Furthermore, in one case, code 226A may be downloaded over
network 201A from remote system 201B, where similar code 201C is
stored on a storage device 201D. in another case, code 226A may be
downloaded over network 201A to remote system 201B, where
downloaded code 201C is stored on a storage device 201D.
[0078] The hardware in FIGS. 1-2 may vary depending on the
implementation. Other internal hardware or peripheral devices, such
as flash memory, equivalent non-volatile memory, or optical disk
drives and the like, may be used in addition to or in place of the
hardware depicted in FIGS. 1-2. In addition, the processes of the
illustrative embodiments may be applied to a multiprocessor data
processing system.
[0079] In some illustrative examples, data processing system 200
may be a personal digital assistant (PDA), which is generally
configured with flash memory to provide non-volatile memory for
storing operating system files and/or user-generated data. A bus
system may comprise one or more buses, such as a system bus, an I/O
bus, and a PCI bus. Of course, the bus system may be implemented
using any type of communications fabric or architecture that
provides for a transfer of data between different
computer-components or data processing devices attached to the
fabric or architecture.
[0080] A communications unit may include one or more
communications-capable devices used to transmit and receive data,
such as a modem or a network adapter. A memory may be, for example,
main memory 208 or a cache, such as the cache found in North Bridge
and memory controller hub 202. A processing unit may include one or
more processors or CPUs.
[0081] The depicted examples in FIGS. 1-2 and above-described
examples are not meant to imply architectural limitations. For
example, data processing system 200 also may be a tablet computer,
laptop computer, or telephone device in addition to taking the form
of a mobile or wearable device.
[0082] Where a computer or data processing system is described as a
virtual machine, a virtual device, or a virtual component, the
virtual machine, virtual device, or the virtual component operates
in the manner of data processing system 200 using virtualized
manifestation of some or all components depicted in data processing
system 200. For example, in a virtual machine, virtual device, or
virtual component, processing unit 206 is manifested as a
virtualized instance of all or some number of hardware processing
units 206 available in a host data processing system, main memory
208 is manifested as a virtualized instance of all or some portion
of main memory 208 that may be available in the host data
processing system, and disk 226 is manifested as a virtualized
instance of all or some portion of disk 226 that may be available
in the host data processing system. The host data processing system
in such cases is represented by data processing system 200.
[0083] With reference to FIG. 3, this figure depicts a block
diagram of a portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0084] Non-limiting example substrate 300 is depicted as comprising
Silicon (Si) layer 302 and Silicon Nitride (SiN) layer 304.
Direction 306 is a direction of the plane of fabrication, as
described herein. In one step of the example process, notated as
circled 1 without implying any sequencing of the steps, space 308
is created in substrate 300, e.g., by etching a portion of
substrate 300.
[0085] In another step of the example process, notated as circled 2
without implying any sequencing of the steps, removable material
layer 310 is formed in space 308. Removable material layer 310 is
removable by any suitable method without disturbing adjacent
structures. In one embodiment, removable material 310 is Silicon
Germanium (SiGe) that is removable using hydrochloric acid (HCl) in
a known process.
[0086] Further in the step of the example process, bottom layer
312, whose backside has to be accessible, is deposited over
removable material 310. In one embodiment, bottom layer 312 is a
bottom S/D of a vertical finFET device. In one embodiment, the
material of bottom layer 312 comprises Dopes Si or implanted
Si.
[0087] In another step of the example process, notated as circled 3
without implying any sequencing of the steps, layer 304 is removed.
The removal can be accomplished using any known process, suitable
for the material of layer 304 without disturbing layer 312.
[0088] Steps 1, 2, and 3 have been depicted in a cross-sectional
view of the device being fabricated. View 314 is a
three-dimensional view of the device being fabricated.
[0089] With reference to FIG. 4, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0090] In another step of the example process, notated as circled 4
without implying any sequencing of the steps, a vertical channel
material is deposited as layer 316 above layer 302. In one
embodiment, the vertical channel material of layer 316 is un-doped
Silicon.
[0091] In another step of the example process, notated as circled 5
without implying any sequencing of the steps, portions of layer 316
is removed such that vertical channel structure 318 is left
standing in a direction substantially orthogonal to direction 306
of the plane of fabrication. Any number of vertical channel
structures 318 can be fabricated in a similar manner. Four
non-limiting example vertical channel structures 318 are shown,
where the left two can be used in an example vertical n-finFET and
the right two can be used in an example vertical p-finFET.
[0092] Hard mask (HM) 320 comprising one or more layers is
deposited on top of vertical channel structures 318. In one
embodiment, HM 320 is formed using SiN and separated from vertical
channel structures 318 by a layer of Silicon Oxide (SiO).
Generally, the SiO layer can be as thin as 2 nanometers.
[0093] Steps 4 and 5 have been depicted in a cross-sectional view
of the device being fabricated. View 324 is a three-dimensional
view of the device being fabricated.
[0094] With reference to FIG. 5, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0095] In another step of the example process, notated as circled 6
without implying any sequencing of the steps, shallow trench
isolation (STI) structure 326 is formed using a suitable material.
Only as an example, STI 326 is shown to be formed on each end of
the structures being fabricated. Generally, STI 326 can be
fabricated to separate different devices being fabricated on the
same substrate.
[0096] Step 6 has been depicted in a cross-sectional view of the
device being fabricated. View 325 is a three-dimensional view of
the device being fabricated.
[0097] With reference to FIG. 6, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0098] In another step of the example process, notated as circled 7
without implying any sequencing of the steps, additional layers or
structures are formed as shown. For example, bottom spacer layer
327 is formed as shown using a suitable material. For example, in
one embodiment, a metal oxide, nitride, or a similar material is
used to form bottom spacer layer 327 as a dielectric film.
[0099] Further, a high resistance (high-k) material is used to form
structure 328. Work function metal (WFM) layer 330 is formed as
shown. Gates 332 are formed relative to a vertical channel
structure 318 using a suitable metal as shown. For example, top
spacer layer 334 is formed as shown using a suitable material. For
example, in one embodiment, a metal oxide, nitride, or a similar
material is used to form top spacer layer 334 as a dielectric
film.
[0100] Step 7 has been depicted in a cross-sectional view of the
device being fabricated. View 335 is a three-dimensional view of
the device being fabricated. Furthermore, removable material layer
310 is caused to be exposed. For example, material obstructing
access to layer 310 is etched using a suitable method to expose at
least one side of layer 310 as is more clearly visible in
three-dimensional view 335.
[0101] With reference to FIG. 7, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0102] Note that the high temperature step of forming gates 332 has
now been completed in the step 7 or sub-steps thereof, as depicted
in FIG. 6. In step 8, which occurs after step 7 has already
occurred immediately prior to step 8 or with some other steps
intervening, removable material layer 310 is now removed to form
tunnel 336 below bottom layer 312. Tunnel 336 is a hollow space, or
void, below bottom layer 312, formed such that the backside of
bottom layer 312 forms the ceiling of tunnel 336.
[0103] Step 8 has been depicted in a cross-sectional view of the
device being fabricated. View 337 is a three-dimensional view of
the device being fabricated.
[0104] With reference to FIG. 8A, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0105] In another step of the example process, notated as circled
9, additional structures are formed as shown. In step 9, which
occurs after step 8 has already occurred immediately prior to step
9 or with some other steps intervening, tunnel 336 is filled with
conductive material 338. In one embodiment, conductive material 338
is a Silicide of a suitable metal, such as, but not limited to
Titanium Silicide, Cobalt Silicide, and many others.
[0106] Step 9 has been depicted in a cross-sectional view of the
device being fabricated. View 339A is a three-dimensional view of
the device being fabricated.
[0107] Not shown in FIG. 8A, but shown in FIG. 8B, is one
non-limiting example manner of filling tunnel 336 with material
338. In this example, material 338 is a silicide. Filling silicide
338 in tunnel 336 is performed by first coating tunnel 336--by
first depositing a metal such as Titanium (Ti), Cobalt (Co), Nickel
(Ni), Nickel Platinum alloy, or Tungsten (W), using a process such
as Chemical Vapor Deposition (CVD) or atomic layer deposition
(ALD)--such that the metal occupies only a portion of the tunnel
space, leaving tunnel 336 still open through the length of tunnel
336 and open at both ends.
[0108] For example, if the tunnel were 15 nanometers tall and 15
nanometers wide, and L nanometers long, the metal would be
deposited such that 3-4 nanometers thick layer of the metal would
deposit on each wall of tunnel 336, leaving 8-7 nanometers of width
and height still open for length L of tunnel 336. The remaining
open space of 8-7 nanometers wide and tall is then filled with a
suitable silicide.
[0109] The silicide may be, but need not be filled for the entire
length L, for the entire remaining width of the remaining opening
of tunnel 336, for the entire remaining height of the remaining
opening of tunnel 336, or some combination thereof. The silicide
filling may be filled in the remaining opening of tunnel 336 at
least to the extent that the silicide is electrically connected
with the backside of bottom layer 312, and is sufficiently exposed
and accessible to connect a contact to the silicide.
[0110] With reference to FIG. 8B, this figure depicts another
three-dimensional view of the filled tunnel in accordance with an
illustrative embodiment. View 339B is another three-dimensional
view of step 9 with the metal coating depicted.
[0111] Coating 340 is the metal deposited using CVD or other
suitable technique. Metal 340 makes electrical contact with the
backside of bottom layer 312, as shown. Filled silicide 338 makes
electrical contact with metal 340, thereby making an electrical
connection with the backside of bottom layer 312, as shown. Fully
filled tunnel 336 is shown in FIG. 8B without implying any
limitation. Partially filled tunnel 336--partially coated with
metal 340, partially filled with conducting material 338, or both,
can also be used, as described herein.
[0112] With reference to FIG. 9, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0113] In another step of the example process, notated as circled
10 without implying any sequencing of the steps, additional layers
or structures are formed as shown. Top S/D 342 is formed over a
vertical channel, e.g., over one or more vertical channels 318.
Particularly, HM 320 and any intermediate layers such as layer 322
are removed from each such vertical channel 318 over which top S/D
342 is formed, such that top S/D 342 can be electrically connected
with the one or more vertical channel 318.
[0114] Multiple top S/D can be similarly formed using different
sets of vertical channels 318--e.g., top S/D 342 formed using two
vertical channel 318 and top S/D 344 formed using two different
vertical channel 318. In one embodiment, an epitaxy (epi) is formed
for use as top S/D 342 and a different epi is formed for use as top
S/D 344.
[0115] The materials used for top S/D 342 and 344 may be same or
different depending on the devices being fabricated for example top
S/D 342 could be the top S/D for an n-finFET and top S/D 344 could
be the top S/D for a p-finFET.
[0116] Step 10 has been depicted in a cross-sectional view of the
device being fabricated. View 345 is a three-dimensional view of
the device being fabricated.
[0117] With reference to FIG. 10, this figure depicts a block
diagram of another portion of an example process for fabricating an
example vertical channel finFET device in accordance with an
illustrative embodiment. Application 105 in FIG. 1 interacts with
fabrication system 107 to produce or manipulate substrate 300 as
described herein.
[0118] In another step of the example process, notated as circled
11, additional layers or structures are formed as shown. Contact
346 is electrically coupled with top S/D 342. Contact 346 is formed
using a suitably conductive material. Similarly, contact 348 is
formed and electrically coupled with top S/D 344. Contact 350 is
formed and electrically coupled with an exposed and accessible
portion of silicide or other similarly purposed material 338, which
is electrically coupled with the backside of bottom layer 312 as
described herein.
[0119] Step 11 has been depicted in a cross-sectional view of the
device being fabricated. View 351 is a three-dimensional view of
the device being fabricated.
[0120] With reference to FIG. 11, this figure depicts a block
diagram of an example process for fabricating multiple vertical
channel devices with reduced bottom S/D resistance in accordance
with an illustrative embodiment. Application 105 in FIG. 1
interacts with fabrication system 107 to produce or manipulate
substrate 300 as described herein.
[0121] The structures formed using an embodiment and depicted in
FIG. 10, can be formed into separate devices, e.g., an n-finFET and
a p-finFET, as shown in FIG. 11. For example, STI 326 can be formed
using a suitable method between vertical channels 318A and 318B,
and extending through each layer starting at top spacer 334 and all
the way into layer 302, extending all the way to the back for the
entire length of the devices, as shown in this length-wise view
351B (if view 351B is assumed to be in the XY coordinate plane, the
length of the devices is the Z axis).
[0122] STI 326A fully isolates the example n-finFET device (bound
between STI 326A and 326B) from the example p-finFET device (bound
between STI 326A and 326C). Contact 346 becomes the top S/D contact
for the n-finFET device and connects to vertical channels 318A.
Contact 350A is placed in electrical connection with silicide or
other similarly purposed material filling 338A. Contact 348 becomes
the top S/D contact for the p-finFET device and connects to
vertical channels 318B. Contact 350B is placed in electrical
connection with silicide or other similarly purposed material
filling 338B.
[0123] With reference to FIG. 12, this figure depicts a flowchart
of an example process for reducing resistance of bottom
source/drain in vertical channel devices in accordance with an
illustrative embodiment. Process 1200 can be implemented in
application 105 in FIG. 1.
[0124] The application etches a substrate to create a recess (block
1202). The application deposits or forms a layer of SiGe or other
removable material in the recess (block 1204). The application
deposits or forms a bottom S/D layer over the SiGe layer of block
1204 using a suitable material such as doped or implanted Si (block
1206).
[0125] The application fabricates one or more vertical channels
(e.g., vertical fins) using a suitable material such as un-doped
Si, a hard mask of a suitable material over the fins and any
intermediate layers between the top of the fin and the bottom of
the hard mask (block 1208). The application constructs STI
structures on each side of the bottom S/D layer and the SiGe layer
(block 1210).
[0126] The application optionally installs spacer layers, high-k
layer, and WFM layer, or some combination thereof, as needed for
the device being fabricated (block 1212). The application
constructs one or more gates using a suitable metal (block
1214).
[0127] The application removes the SiGe layer to form a hollow
tunnel below the bottom S/D, exposing the backside of the bottom
S/D layer (block 1216). The application optionally deposits a thin
layer of a suitable metal inside the tunnel on the tunnel walls,
floor, and ceiling using a suitable method (block 1218). The
depositing of the metal still keeps the tunnel open from STI to
STI.
[0128] The application fills the remaining opening in the tunnel,
fully or partially as described herein, with a suitable silicide or
an equivalent material such that the silicide makes electrical
contact with the backside of the bottom S/D (block 1220). A removal
of some material may be needed to expose at least an STI-side end
of the SiGe layer, so that the removal of the SiGe layer, the
depositing of the metal in the tunnel, and the filling of the
silicide in the tunnel can be performed. The filling is performed
in a manner that at least a portion of the silicide remains exposed
and accessible for electrical connection.
[0129] The application connects an electrically conductive contact
to the silicide (block 1222). The application ends process 1200
thereafter. This manner of connecting the electrical contact to the
silicide causes an electrical current to advantageously travel from
the contact through low-resistance silicide and up through the
bottom S/D to the vertical channel (or a reverse of this flow
depending on the operation of the device) according to the
illustrative embodiments, without having to first travel down and
across the bottom S/D before traveling up through the bottom S/D
and to the vertical channel (or a reverse of this flow) as in the
prior-art.
[0130] Thus, a computer implemented method, system or apparatus,
and computer program product are provided in the illustrative
embodiments for reducing resistance of bottom source/drain in
vertical channel devices and other related features, functions, or
operations. Where an embodiment or a portion thereof is described
with respect to a type of mobile device, the computer implemented
method, system or apparatus, the computer program product, or a
portion thereof, are adapted or configured for use with a suitable
and comparable manifestation of that type of mobile device.
[0131] Where an embodiment is described as implemented in an
application, the delivery of the application in a Software as a
Service (SaaS) model is contemplated within the scope of the
illustrative embodiments. In a SaaS model, the capability of the
application implementing an embodiment is provided to a user by
executing the application in a cloud infrastructure. The user can
access the application using a variety of client devices through a
thin client interface such as a web browser (e.g., web-based
e-mail), or other light-weight client-applications. The user does
not manage or control the underlying cloud infrastructure including
the network, servers, operating systems, or the storage of the
cloud infrastructure. In some cases, the user may not even manage
or control the capabilities of the SaaS application. In some other
cases, the SaaS implementation of the application may permit a
possible exception of limited user-specific application
configuration settings.
[0132] The present invention may be a system, a method, and/or a
computer program product at any possible technical detail level of
integration. The computer program product may include a computer
readable storage medium (or media) having computer readable program
instructions thereon for causing a processor to carry out aspects
of the present invention.
[0133] The computer readable storage medium can be a tangible
device that can retain and store instructions for use by an
instruction execution device. The computer readable storage medium
may be, for example, but is not limited to, an electronic storage
device, a magnetic storage device, an optical storage device, an
electromagnetic storage device, a semiconductor storage device, or
any suitable combination of the foregoing. A non-exhaustive list of
more specific examples of the computer readable storage medium
includes the following: a portable computer diskette, a hard disk,
a random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM or Flash memory), a static
random access memory (SRAM), a portable compact disc read-only
memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a
floppy disk, a mechanically encoded device such as punch-cards or
raised structures in a groove having instructions recorded thereon,
and any suitable combination of the foregoing. A computer readable
storage medium, as used herein, is not to be construed as being
transitory signals per se, such as radio waves or other freely
propagating electromagnetic waves, electromagnetic waves
propagating through a waveguide or other transmission media (e.g.,
light pulses passing through a fiber-optic cable), or electrical
signals transmitted through a wire.
[0134] Computer readable program instructions described herein can
be downloaded to respective computing/processing devices from a
computer readable storage medium or to an external computer or
external storage device via a network, for example, the Internet, a
local area network, a wide area network and/or a wireless network.
The network may comprise copper transmission cables, optical
transmission fibers, wireless transmission, routers, firewalls,
switches, gateway computers and/or edge servers. A network adapter
card or network interface in each computing/processing device
receives computer readable program instructions from the network
and forwards the computer readable program instructions for storage
in a computer readable storage medium within the respective
computing/processing device.
[0135] Computer readable program instructions for carrying out
operations of the present invention may be assembler instructions,
instruction-set-architecture (ISA) instructions, machine
instructions, machine dependent instructions, microcode, firmware
instructions, state-setting data, configuration data for integrated
circuitry, or either source code or object code written in any
combination of one or more programming languages, including an
object oriented programming language such as Smalltalk, C++, or the
like, and procedural programming languages, such as the "C"
programming language or similar programming languages. The computer
readable program instructions may execute entirely on the user's
computer, partly on the user's computer, as a stand-alone software
package, partly on the user's computer and partly on a remote
computer or entirely on the remote computer or server. In the
latter scenario, the remote computer may be connected to the user's
computer through any type of network, including a local area
network (LAN) or a wide area network (WAN), or the connection may
be made to an external computer (for example, through the Internet
using an Internet Service Provider). In some embodiments,
electronic circuitry including, for example, programmable logic
circuitry, field-programmable gate arrays (FPGA), or programmable
logic arrays (PLA) may execute the computer readable program
instructions by utilizing state information of the computer
readable program instructions to personalize the electronic
circuitry, in order to perform aspects of the present
invention.
[0136] Aspects of the present invention are described herein with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems), and computer program products
according to embodiments of the invention. It will be understood
that each block of the flowchart illustrations and/or block
diagrams, and combinations of blocks in the flowchart illustrations
and/or block diagrams, can be implemented by computer readable
program instructions.
[0137] These computer readable program instructions may be provided
to a processor of a general purpose computer, special purpose
computer, or other programmable data processing apparatus to
produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or blocks.
These computer readable program instructions may also be stored in
a computer readable storage medium that can direct a computer, a
programmable data processing apparatus, and/or other devices to
function in a particular manner, such that the computer readable
storage medium having instructions stored therein comprises an
article of manufacture including instructions which implement
aspects of the function/act specified in the flowchart and/or block
diagram block or blocks.
[0138] The computer readable program instructions may also be
loaded onto a computer, other programmable data processing
apparatus, or other device to cause a series of operational steps
to be performed on the computer, other programmable apparatus or
other device to produce a computer implemented process, such that
the instructions which execute on the computer, other programmable
apparatus, or other device implement the functions/acts specified
in the flowchart and/or block diagram block or blocks.
[0139] The flowchart and block diagrams in the Figures illustrate
the architecture, functionality, and operation of possible
implementations of systems, methods, and computer program products
according to various embodiments of the present invention. In this
regard, each block in the flowchart or block diagrams may represent
a module, segment, or portion of instructions, which comprises one
or more executable instructions for implementing the specified
logical function(s). In some alternative implementations, the
functions noted in the blocks may occur out of the order noted in
the Figures. For example, two blocks shown in succession may, in
fact, be executed substantially concurrently, or the blocks may
sometimes be executed in the reverse order, depending upon the
functionality involved. It will also be noted that each block of
the block diagrams and/or flowchart illustration, and combinations
of blocks in the block diagrams and/or flowchart illustration, can
be implemented by special purpose hardware-based systems that
perform the specified functions or acts or carry out combinations
of special purpose hardware and computer instructions.
* * * * *