U.S. patent application number 17/140645 was filed with the patent office on 2021-04-29 for devices and methods for heat dissipation of semiconductor integrated circuits.
The applicant listed for this patent is Taiwan Semiconductor Manufacturing Co., Ltd.. Invention is credited to Chung-Peng HSIEH, Sa-Lly LIU, Yung-Chow PENG, Chung-Chieh YANG.
Application Number | 20210125890 17/140645 |
Document ID | / |
Family ID | 1000005316488 |
Filed Date | 2021-04-29 |
United States Patent
Application |
20210125890 |
Kind Code |
A1 |
YANG; Chung-Chieh ; et
al. |
April 29, 2021 |
DEVICES AND METHODS FOR HEAT DISSIPATION OF SEMICONDUCTOR
INTEGRATED CIRCUITS
Abstract
A semiconductor device is disclosed. In one example, the
semiconductor device includes: an electronic component having a top
surface, a bottom surface, and two end portions; a plurality of
contacts disposed on the top surface; and a plurality of metal
nodes disposed on the plurality of contacts. The plurality of
contacts includes two end contacts disposed at the two end portions
respectively and at least one intermediate contact disposed between
the two end contacts. The plurality of metal nodes includes two end
metal nodes disposed on the two end contacts respectively and at
least one intermediate metal node disposed on the at least one
intermediate contact.
Inventors: |
YANG; Chung-Chieh; (Zhubei
City, TW) ; PENG; Yung-Chow; (Hsinchu City, TW)
; HSIEH; Chung-Peng; (Hsinchu City, TW) ; LIU;
Sa-Lly; (Hsin-Chu, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Semiconductor Manufacturing Co., Ltd. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
1000005316488 |
Appl. No.: |
17/140645 |
Filed: |
January 4, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16681687 |
Nov 12, 2019 |
10886190 |
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17140645 |
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15883462 |
Jan 30, 2018 |
10510637 |
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16681687 |
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62552176 |
Aug 30, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/5228 20130101;
H01L 23/552 20130101; H01L 23/647 20130101; H01L 23/34 20130101;
H01L 28/00 20130101 |
International
Class: |
H01L 23/34 20060101
H01L023/34; H01L 23/64 20060101 H01L023/64; H01L 23/552 20060101
H01L023/552; H01L 23/522 20060101 H01L023/522; H01L 49/02 20060101
H01L049/02 |
Claims
1. A semiconductor device, comprising: an electronic component
having a top surface, a bottom surface, and two end portions; two
end contacts disposed on the top surface, wherein the two end
contacts are disposed at the two end portions respectively; two end
metal nodes disposed on the two end contacts respectively; a
dielectric layer disposed below the bottom surface; a first metal
layer in contact with the dielectric layer, wherein the first metal
layer has (a) a first length that is less than or equal to a length
of the electronic component and (b) a first width that is less than
or equal to a width of the electronic component; and a ground plane
conductively coupled to the electronic component.
2. The device of claim 1, further comprising: a second metal layer
disposed below the first metal layer, wherein the second metal
layer has (c) a second length that is greater than or equal to the
first length and (d) a second width that is greater than or equal
to the first width.
3. The device of claim 2, wherein the first and second metal layers
provide first and second intermediate metal nodes, respectively,
wherein the first and second intermediate metal nodes are each
disposed below the dielectric layer and between the two end
portions and are coupled to each other by at least one via that
thermally couples first and second metal layers.
4. The device of claim 3, further comprising a substrate disposed
below the first and second intermediate metal nodes, wherein the
first and second intermediate metal nodes thermally couples the
electronic component to the substrate.
5. The device of claim 1, wherein the electronic component is
formed of a high resistance material.
6. A semiconductor device, comprising: an electronic component
layer comprising a plurality of electronic components connected in
series, wherein each of the plurality of electronic components has
a top surface, a bottom surface, and two end portions; and a
contact layer comprising a plurality of end contacts disposed on
the electronic component layer, wherein the plurality of end
contacts comprises two end contacts disposed on the top surface of
each of the plurality of electronic components, and the two end
contacts are disposed at the two end portions of the electronic
component, respectively.
7. The device of claim 6, further comprising: a first metal node
layer comprising a first plurality of metal nodes disposed on the
contact layer, wherein each of the first plurality of metal nodes
is disposed on a corresponding one of the plurality of end
contacts, and among the first plurality of metal nodes, any two
metal nodes disposed over two adjacent end portions of two
electronic components are thermally coupled to form a pair of
coupled metal nodes, wherein each pair of coupled metal nodes
comprises a plurality of metal layers and at least one pair of
parallel vias that thermally couple adjacent metal layers in the
plurality of metal layers.
8. The device of claim 7, wherein the plurality of metal layers in
the at least one intermediate metal node further comprises: a first
metal layer in contact with the contact layer, wherein the first
metal layer has (a) a first length that is less than or equal to a
length of the electronic component layer and (b) a first width that
is less than or equal to a width of the electronic component layer;
and a second metal layer disposed over the first metal layer,
wherein the second metal layer has (c) a second length that is
greater than or equal to the first length and (d) a second width
that is greater than or equal to the first width.
9. The device of claim 7, further comprising a ground plane
disposed above the first metal node layer, wherein at least one
pair of coupled metal nodes thermally couples the electronic
component layer to the ground plane.
10. The device of claim 7, further comprising a power plane
disposed above the first metal node layer, wherein at least one
pair of coupled metal nodes thermally couples the electronic
component layer to the power plane.
11. The device of claim 6, further comprising: a dielectric layer
disposed below the electronic component layer; and a second metal
node layer comprising a second plurality of metal nodes disposed
below the dielectric layer, wherein each of the second plurality of
metal nodes is disposed below an end portion of one of the
plurality of electronic components, and among the second plurality
of metal nodes, any two metal nodes disposed below two adjacent end
portions of two electronic components are thermally coupled to each
other.
12. The device of claim 6, wherein each of the plurality of
electronic components is formed of a high resistance material.
13. A method for forming a semiconductor device, comprising:
forming an electronic component having a top surface, a bottom
surface, and two end portions; forming two end contacts on the top
surface, wherein the two end contacts are disposed at the two end
portions respectively; forming two end metal nodes on the two end
contacts respectively; forming a dielectric layer below the bottom
surface; and forming a first metal layer in contact with the
dielectric layer, wherein the first metal layer has (a) a first
length that is less than or equal to a length of the electronic
component and (b) a first width that is less than or equal to a
width of the electronic component.
14. The method of claim 13, further comprising: forming a second
metal layer disposed over the first metal layer, wherein the second
metal layer has (c) a second length that is greater than or equal
to the first length and (d) a second width that is greater than or
equal to the first width.
15. The method of claim 14, wherein the first and second metal
layers provide first and second intermediate metal nodes,
respectively, wherein the first and second intermediate metal nodes
are each disposed below the dielectric layer and between the two
end portions and are coupled to each other by at least one via that
thermally couples first and second metal layers.
16. The method of claim 15, wherein: each of the first and second
metal layers has a same shape as that of the electronic component;
and an area of each metal layer is smaller than or equal to that of
the electronic component.
17. The method of claim 15, further comprising forming a ground
plane below the first and second intermediate metal nodes, wherein
the first and second intermediate metal nodes thermally couple the
electronic component to the ground plane.
18. The method of claim 15, further comprising forming a power
plane below the first and second intermediate metal nodes, wherein
the at first and second intermediate metal nodes thermally couple
the electronic component to the power plane.
19. The method of claim 13, further comprising: forming an
additional contact on the top surface and between the two end
contacts; and forming an additional metal node on the additional
contact.
20. The method of claim 13, wherein the electronic component is
formed of a high resistance material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of U.S.
patent application Ser. No. 16/681,687, filed Nov. 12, 2019, which
is a divisional application of U.S. patent application Ser. No.
15/883,462, filed Jan. 30, 2018 which claims priority to U.S.
Provisional Patent Application No. 62/552,176, filed on Aug. 30,
2017, each of which are incorporated by reference herein in their
entireties.
BACKGROUND
[0002] An integrated circuit (IC) typically includes a large number
of electronic components, such as resistors, transistors,
capacitors, etc., on a chip of semiconductor material. The
semiconductor IC industry has experienced rapid growth in the past
several decades. Technological advances in semiconductor materials
and design have produced increasingly smaller and more complex
circuits. As the geometry size of an IC decreases, the practical
significance of an electromigration (EM) effect of the IC
increases. EM is the transport of material caused by gradual
movement of ions in a conductor/resistor. A resistor under
operation in an IC generates heat and increases temperature of the
IC, which is known as Joule heating. EM is exacerbated by a high
Joule heating of the resistor, which can lead to eventual failure
of electrical components in the IC.
[0003] The thermal distribution of a resistor under operation is
typically not uniform. According to the physical structure of the
resistor, contacts at two sides of the resistor are connected to
colder devices or metals, to serve as heat dissipation paths. While
lower temperatures can be observed at the two sides of the
resistor, the resistor's center area forms a thermal hot spot. In
this case, the resistor's center area has the highest temperature
and forms the weakest point in terms of EM. Especially, the center
temperature of the resistor becomes higher when the resistor has a
larger length and/or a larger current. While conventional
techniques use edge contacts to relax temperatures at a resistor's
edges by heat dissipation, the resistor's center remains as a hot
spot and an EM critical area. Thus, conventional techniques for
heat dissipation of resistors in an IC are not entirely
satisfactory.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that various features are not necessarily
drawn to scale. In fact, the dimensions and geometries of the
various features may be arbitrarily increased or reduced for
clarity of discussion. Like reference numerals denote like features
throughout specification and drawings.
[0005] FIG. 1 illustrates top views of exemplary semiconductor
devices, in accordance with various embodiments of the present
disclosure.
[0006] FIG. 2 illustrates top views of a first set of exemplary
semiconductor devices, in accordance with some embodiments of the
present disclosure.
[0007] FIG. 3 illustrates temperature distributions of the
exemplary semiconductor devices shown in FIG. 2, in accordance with
some embodiments of the present disclosure.
[0008] FIG. 4 illustrates corresponding cross-sectional views of
some of the exemplary semiconductor devices shown in FIG. 2, in
accordance with some embodiments of the present disclosure.
[0009] FIG. 5 illustrates top views and temperature distributions
of a second set of exemplary semiconductor devices, in accordance
with some embodiments of the present disclosure.
[0010] FIG. 6 illustrates a corresponding cross-sectional view of
one of the exemplary semiconductor devices shown in FIG. 5, in
accordance with some embodiments of the present disclosure.
[0011] FIG. 7 illustrates top views of a third set of exemplary
semiconductor devices, in accordance with some embodiments of the
present disclosure.
[0012] FIG. 8 illustrates temperature distributions of the
exemplary semiconductor devices shown in FIG. 7, in accordance with
some embodiments of the present disclosure.
[0013] FIG. 9 illustrates a corresponding cross-sectional view of
one of the exemplary semiconductor devices shown in FIG. 7, in
accordance with some embodiments of the present disclosure.
[0014] FIG. 10 illustrates a geometry design for the first set of
exemplary semiconductor devices shown in FIG. 2, in accordance with
some embodiments of the present disclosure.
[0015] FIG. 11 illustrates a geometry design for the second set of
exemplary semiconductor devices shown in FIG. 5, in accordance with
some embodiments of the present disclosure.
[0016] FIG. 12 is a flow chart illustrating an exemplary method for
forming a semiconductor device, in accordance with some embodiments
of the present disclosure.
[0017] FIG. 13 is a flow chart illustrating another exemplary
method for forming a semiconductor device, in accordance with some
embodiments of the present disclosure.
[0018] FIG. 14 is a flow chart illustrating yet another exemplary
method for forming a semiconductor device, in accordance with some
embodiments of the present disclosure.
DETAILED DESCRIPTION
[0019] The following disclosure describes various exemplary
embodiments for implementing different features of the subject
matter. Specific examples of components and arrangements are
described below to simplify the present disclosure. These are, of
course, merely examples and are not intended to be limiting. For
example, the formation of a first feature over or on a second
feature in the description that follows may include embodiments in
which the first and second features are formed in direct contact,
and may also include embodiments in which additional features may
be formed between the first and second features, such that the
first and second features may not be in direct contact. In
addition, the present disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed.
[0020] 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.
[0021] While edge/end contacts have been used to reduce temperature
of a resistor, the resistor's center area remains to be a hot spot.
One way to relax the temperature of the resistor's center area is
dividing the resistor into two resistors in parallel. For example,
a resistor with a width of 1 .mu.m can be divided to two resistors
in parallel, each with a width of 0.5 .mu.m. The increased overall
surface of the two resistors gains benefits to thermal radiation.
But each of the two resistors' center area is still a hot spot,
compared to other areas of the two resistors.
[0022] The present disclosure aims at improving resistors' EM
effect in an IC by relaxing the resistors' Joule heating at the hot
spot area, in order to reduce the temperatures around resistors in
the IC during operation. The present disclosure provides various
embodiments of a semiconductor device (e.g. a semiconductor IC)
that includes a resistor with both two end metal nodes disposed at
two end portions of the resistor and at least one intermediate
metal node disposed between the two end portions, and methods of
forming the semiconductor device. The resistor has a top surface, a
bottom surface, and two end portions. The at least one intermediate
metal node can serve as a heat sink inserted to the resistor for
heat dissipation of the resistor.
[0023] In some embodiments, each of the end metal nodes and the at
least one intermediate metal node is disposed on a contact that is
in direct contact with the top surface. The at least one
intermediate metal node in these embodiments can thermally couple
the resistor to a ground plane or a power plane in the device for
heat dissipation.
[0024] In other embodiments, the device comprises a dielectric
layer disposed below the bottom surface of the resistor, and the at
least one intermediate metal node is disposed below the dielectric
layer such that the at least one intermediate metal node has
indirect contact with the resistor. The at least one intermediate
metal node in these embodiments can thermally couple the resistor
to a substrate in the device for heat dissipation.
[0025] In yet other embodiments, the resistor is a resistor layer
including a plurality of sub-resistors connected in series. In
these embodiments, each sub-resistor has a top surface, a bottom
surface, and two end portions. A metal node is disposed on each end
portion of each sub-resistor; and any two metal nodes disposed over
two adjacent end portions of two adjacent sub-resistors are
thermally coupled to form a pair of coupled metal nodes which may
be treated as an intermediate metal node pair for heat dissipation
of the resistor. An intermediate metal node pair may be disposed on
the top surface via a pair of contacts and thermally couple the
resistor to a ground plane or a power plane in the device for heat
dissipation; or may be disposed below a dielectric layer under the
resistor and thermally couple the resistor to a substrate in the
device for heat dissipation.
[0026] As dimensions of semiconductor devices continue to decrease
and packaging densities continue to increase, parasitic capacitance
becomes more and more important to improve the operating speed of
the devices. To reduce the parasitic capacitance at the area
overlapping between the intermediate metal node and the substrate,
the present disclosure provides a method for designing a geometry
shape and size of the intermediate metal node such that the metal
node is in parallel with the resistor or fully covered by the
resistor area.
[0027] It can be understood that although the description in the
present disclosure focuses on resistor usage in integrated circuits
(ICs), the present disclosure is applicable to all kinds of
electronic components that can produce heat in an electronic
circuit due to passage of an electric current. The disclosed
semiconductor device structure can especially benefit those
resistors, e.g. termination resistors, with high-current usages, by
decreasing temperature in a resistor's center area (EM critical
area) and suppressing the increase of parasitic capacitance brought
by heat sink insertion.
[0028] FIG. 1 illustrates top views of exemplary semiconductor
devices, in accordance with various embodiments of the present
disclosure. FIG. 1 shows three embodiments for inserting a heat
sink, e.g. an upper metal 103 via a contact 102 or a lower metal
105 via an indirect contact 104, in a resistor, e.g. a high
resistance (HiR) resistor 101, for heat dissipation. In accordance
with various embodiments, a HiR resistor is formed of a high
resistance material, e.g. Titanium nitride (TiN) or Tantalum
nitride (TaN).
[0029] In embodiment (1) 110, two end nodes (node A 118 and node B
119) are disposed on a HiR resistor 111 via two end contacts 112-1,
112-2 to form heat dissipation paths. As discussed above, if the
resistor only has these two end nodes on the two ends of the
resistor, heat will be clouded and accumulated at center of the
resistor. As such, the HiR resistor 111 also has an intermediate
node (node 1 116) inserted between the two ends to serve as a heat
sink for reducing temperature of the center area of the HiR
resistor 111. The node 1 116 here includes an upper metal 113
disposed on a contact 112 that is in direct contact with a top
surface of the HiR resistor 111, such that heat in the center of
the HiR resistor 111 can be dissipated via the node 1 116 to a
large heat sink pool in the semiconductor device. For example, when
the device in embodiment (1) is a semiconductor IC, the node 1 116
may thermally couple the HiR resistor 111 to a mesh power/ground
plane that can further dissipate heat out of the IC. The size of
the upper metal 113 could be optimized according to electrical and
thermal performance requirement of the device. Compared with a
conventional device that does not include the intermediate node
116, the device in this embodiment has a similar electrical
performance and may have just a minor parasitic capacitance
overhead. To reduce the parasitic capacitance introduced by the
inserted heat sink, one can design heat sink metal shapes to make
the metal 113 run in parallel with the resistor 111 and/or be fully
covered by the area of the resistor 111. Details of geometry design
of the metal node will be discussed later.
[0030] In embodiment (2) 120, two end nodes (node A 128 and node B
129) are disposed on a HiR resistor 121 via two end contacts 122-1,
122-2 to form heat dissipation paths. To reduce heat clouded and
accumulated at center of the resistor 121, the HiR resistor 121
also has an intermediate node (node 1 126) inserted between the two
ends to serve as a heat sink. The node 1 126 here includes a lower
metal 125 disposed below an indirect contact 124 below a bottom
surface of the HiR resistor 121, such that heat in the center of
the HiR resistor 121 can be dissipated via the node 1 126 to a
large heat sink pool in the semiconductor device. For example, when
the device in embodiment (2) is a semiconductor IC, the node 1 126
may thermally couple the HiR resistor 121 to a substrate, e.g. a
bulk complementary metal-oxide-semiconductor (CMOS) or a silicon on
insulator (SOI) CMOS, that can further dissipate heat out of the
IC. The size of the lower metal 125 could be optimized according to
electrical and thermal performance requirement of the device.
Compared with a conventional device that does not include the
intermediate node 126, the device in this embodiment has a similar
electrical performance and may have some parasitic capacitance
overhead. The 120 in FIG. 1 may introduce more parasitic
capacitance to the device, because the underneath heat sink 126 is
not only a thermal conductor but also an "electrical conductor"
that brings more parasitic capacitance to the device due to an
unavoidable larger electrical coupling to the substrate. Details of
geometry design of the metal node will be discussed later.
[0031] In the present disclosure, unless stated otherwise, the
electrical current in a resistor has a flowing direction from node
A to node B.
[0032] In embodiment (3) 130, a HiR resistor 131 includes two
separated resistor units (sub-resistors) connected in series. For
example, one 10 ohm resistor can be divided into two 5 ohms
resistors that are connected in series. Two edge taps or end nodes
(node A 138 and node B 139) are disposed on the resistor 131 via
two end contacts 132-1, 132-2 to form heat dissipation paths. In
addition, there are intermediate nodes (node 1 136 and node 2 137)
inserted between the two ends to serve as a heat sink for reducing
temperature of the center area of the HiR resistor 131. In this
embodiment, the two intermediate nodes are disposed on two adjacent
ends of two adjacent sub-resistors and form a thermally coupled
node pair, e.g. by a single piece of metal covering the two
intermediate nodes. The metal may be either an upper metal 133
disposed on contacts 132 that are in direct contact with a top
surface of the HiR resistor 131 as shown in FIG. 1, or a lower
metal disposed below indirect contacts below a bottom surface of
the HiR resistor 131 (not shown). As such, heat in the center area
of the HiR resistor 131, i.e. in the connected area of the two
sub-resistors in embodiment (3) 130, can be dissipated via the
coupled node pair (136-137) to a large heat sink pool in the
semiconductor device. For example, when the device in embodiment
(3) is a semiconductor IC, the coupled node pair (136-137) may
thermally couple the HiR resistor 131, either up to a mesh
power/ground plane or down to a bulk or SOI CMOS, to further
dissipate the heat out of the IC. To reduce the parasitic
capacitance introduced by the inserted heat sink, one can design
heat sink metal pair shapes to make the metal 133 run in parallel
with the resistor 131 and/or be fully covered by the area of the
resistor 131, in similar manners as that in embodiment (1). In one
example, the intermediate nodes in embodiment (3) are not all
disposed at end portions of the sub-resistors, especially when the
sub-resistors have different lengths or sizes. In another example,
each of the intermediate nodes in embodiment (3) is disposed at an
end portion of a sub-resistor, and any two intermediate nodes at
two adjacent sub-resistor ends form a thermally coupled node pair
as shown in FIG. 1, which can make use of existing heat sink
structure to build up new heat sink insertion for serially
connected resistors.
[0033] FIG. 2 illustrates top views of a first set of exemplary
semiconductor devices, in accordance with some embodiments of the
present disclosure. FIG. 2 illustrates different versions of
embodiment (1) in FIG. 1. For example, the embodiment (1A) 110 in
FIG. 2 is the same as the embodiment (1) 110 in FIG. 1, where one
intermediate node (node 1) is inserted between two ends of the
resistor for heat dissipation.
[0034] In embodiment (1B) 220 in FIG. 2, in addition to the two end
nodes (node A 228 and node B 229) disposed on the HiR resistor 221
via two end contacts 222, two intermediate nodes (node 1 226 and
node 2 227) are inserted between two end portions of the resistor
221 for heat dissipation. Each of the two intermediate nodes
includes an upper metal 223 disposed on a contact 222 that is in
direct contact with a top surface of the HiR resistor 221, such
that heat in the center of the HiR resistor 221 can be dissipated
via the two intermediate nodes to a large heat sink pool in the
semiconductor device.
[0035] In embodiment (1C) 230 in FIG. 2, in addition to the two end
nodes (node A 238 and node B 239), three intermediate nodes (node 1
235, node 2 236, and node 3 237) are inserted between two end
portions of the resistor 231 for heat dissipation. Each of the
three intermediate nodes includes an upper metal 233 disposed on a
contact 232 that is in direct contact with a top surface of the HiR
resistor 231, such that heat in the center of the HiR resistor 231
can be dissipated via the two intermediate nodes to a large heat
sink pool in the semiconductor device.
[0036] It can be understood that in some embodiments, the number of
intermediate nodes inserted on the resistor can be larger than
three. It can also be understood that in some embodiments, the
locations of the intermediate nodes disposed on the resistors do
not have to be evenly distributed on the resistor as shown in FIG.
2. For example, when a resistor has one end wider than the other
end, or when a resistor has different material on different
portions of the resistor, the heat sinks (intermediate metal nodes)
can be distributed to correspond to hottest spots on the resistor,
e.g. based on experiments or measurements.
[0037] FIG. 3 illustrates temperature distributions of the
exemplary semiconductor devices shown in FIG. 2, in accordance with
some embodiments of the present disclosure. For the embodiments
(1A) 110, (1B) 220, (1C) 230, FIG. 3 shows corresponding
temperature distributions 310, 320, 330, respectively, along an
axis from node A to node B of the resistor.
[0038] As shown in FIG. 3, the temperature distribution 310 for the
embodiment (1A) 110 has two low points 318, 319 at the two end
nodes and one low point 316 at the intermediate node 1. As the
intermediate node 1 is located at the center of the resistor, there
is no big hot spot at the resistor center in contrast to a
conventional device without intermediate node, but there are two
smaller hot spots 311 in between the nodes. In addition, compared
to a conventional device without intermediate node, the overall
temperature of the resistor in this embodiment is reduced.
[0039] The temperature distribution 320 for the embodiment (1B) 220
has two low points 328, 329 at the two end nodes and two low points
326, 327 at the intermediate nodes 1 and 2. Unlike a conventional
device without intermediate node, there is no big hot spot at the
resistor center here, but there are three smaller hot spots 321 in
between the nodes. In addition, compared to a conventional device
without intermediate node, the overall temperature of the resistor
in this embodiment is reduced.
[0040] Similarly, the temperature distribution 330 for the
embodiment (1C) 230 has two low points 338, 339 at the two end
nodes and three low points 335, 336, 337 at the intermediate nodes
1, 2 and 3. Unlike a conventional device without intermediate node,
there is no big hot spot at the resistor center here, but there are
four smaller hot spots 331 in between the nodes. In addition,
compared to a conventional device without intermediate node, the
overall temperature of the resistor in this embodiment is
reduced.
[0041] As shown in FIG. 3, more intermediate nodes inserted between
two ends of the resistor can bring a lower overall temperature and
a flatter temperature distribution for the resistor. On the other
hand, more intermediate nodes may mean more cost for the device. As
such, one can determine an optimal number of intermediate nodes
based on the tradeoff between temperature reduction and cost
increase, as well as other concerns like resistor and node
geometry, performance requirement, etc.
[0042] FIG. 4 illustrates corresponding cross-sectional views of
some of the exemplary semiconductor devices shown in FIG. 2, in
accordance with some embodiments of the present disclosure.
[0043] FIG. 4 shows a cross-sectional view 110' for the embodiment
(1A). In the cross-sectional view 110', the resistor 111 has a top
surface 410, a bottom surface 420, and two end portions 430-1,
430-2. There are three contacts 112 disposed on the top surface 410
of the resistor 111, including two end contacts disposed at the two
end portions 430-1, 430-2 of the resistor and one intermediate
contact disposed at the center of the resistor 111. In can be
understood that the intermediate contact may be disposed anywhere
between the two end portions according to different embodiments.
There are two end nodes (node A 118 and node B 119) disposed on the
two end contacts 112-1, 112-2 and one intermediate node 116
disposed on the intermediate contact 112-3. The node 116 in this
example includes a plurality of metal layers (heat sink metals N
113-1, N+1 113-2, N+2 113-3, . . . ) and at least one vertical
interconnect access (via) (heat sink vias N 114-1, N+1 114-2, . . .
) that thermally couples adjacent metal layers in the plurality of
metal layers. The heat in the center of the resistor 111 can be
dissipated via the node 116 to a large heat sink pool (e.g. a mesh
power/ground plane) in the semiconductor device.
[0044] FIG. 4 also shows a cross-sectional view 220' for the
embodiment (1B). In the cross-sectional view 220', four contacts
222 are disposed on the resistor 221, including two end contacts
disposed at the two end portions of the resistor and two
intermediate contacts disposed between the two end portions. There
are two end nodes (node A 228 and node B 229) disposed on the two
end contacts 222 and two intermediate nodes 226, 227 disposed on
the two intermediate contacts 222. Each of the two intermediate
nodes 226, 227 in this example includes a plurality of metal layers
and at least one vertical interconnect access (via) that thermally
couples adjacent metal layers in the plurality of metal layers. For
example, the intermediate node 226 in this example includes heat
sink metals N 223-1, N+1 223-2, N+2 223-3, etc. and heat sink vias
N 224-1, N+1 224-2, etc. that thermally couple adjacent heat sink
metals. The heat in the center of the resistor 221 can be
dissipated via the two intermediate nodes 226, 227 to a large heat
sink pool (e.g. a mesh power/ground plane) in the semiconductor
device.
[0045] In accordance with some embodiments, the contacts on top of
a resistor may be formed of Tungsten. In accordance with some
embodiments, each metal layer or each heat sink metal may be formed
of an aluminum alloy.
[0046] In accordance with some embodiments, one can optimize the
number of metal layers in an intermediate node, based on size of
the device, cost of the device, material of the metal layers, and
material of other portions of the device, etc. It can be understood
that, when there are multiple intermediate nodes on the resistor,
the numbers and/or material of metal layers in different
intermediate nodes can be different.
[0047] FIG. 5 illustrates top views and temperature distributions
of a second set of exemplary semiconductor devices, in accordance
with some embodiments of the present disclosure. FIG. 5 illustrates
different versions of embodiment (2) in FIG. 1. For example, the
embodiment (2A) 120 in FIG. 5 is the same as the embodiment (2) 120
in FIG. 1, where one intermediate node (node 1) is inserted between
two ends of the resistor and below the resistor for heat
dissipation.
[0048] In embodiment (2B) 520 in FIG. 5, in addition to the two end
nodes (node A 528 and node B 529) disposed on the resistor 521 via
two end contacts 522, two intermediate nodes (node 1 526 and node 2
527) are inserted between two end portions of the resistor 521 and
below the resistor 521 for heat dissipation. Each of the two
intermediate nodes includes a lower metal 525 disposed below an
indirect contact 524 below a bottom surface of the resistor 521,
such that heat in the center of the resistor 521 can be dissipated
via the two intermediate nodes to a large heat sink pool (e.g. a
bulk or SOI CMOS) in the semiconductor device.
[0049] It can be understood that in some embodiments, the number of
intermediate nodes inserted below the resistor can be larger than
two. It can also be understood that in some embodiments, the
locations of the intermediate nodes disposed below the resistors do
not have to be evenly distributed on the resistor as shown in FIG.
5.
[0050] For the embodiments (2A) 120 and (2B) 520, FIG. 5 shows
corresponding temperature distributions 540 and 550, respectively,
along an axis from node A to node B of the resistor. As shown in
FIG. 5, the temperature distribution 540 for the embodiment (2A)
120 has two lowest points 548, 549 at the two end nodes and one low
point 546 at the intermediate node 1. As the intermediate node 1 is
located at the center of the resistor, there is no big hot spot at
the resistor center in contrast to a conventional device without
intermediate node, but there are two smaller hot spots 541 in
between the nodes. In addition, compared to a conventional device
without intermediate node, the overall temperature of the resistor
in this embodiment is reduced.
[0051] It is observed that, in this example, the temperature at
node 1 is higher than that at nodes A and B. It can also be
observed that, compared to the temperature distribution 310 in FIG.
3, the temperature at node 1 546 in FIG. 5 is higher than that at
node 1 316 in FIG. 3. These observations may indicate that a direct
contact heat sink works better than an indirect contact heat sink,
when other parameters of the heat sinks are comparable.
[0052] Similarly, the temperature distribution 550 for the
embodiment (2B) 520 has two low points 558, 559 at the two end
nodes and two low points 556, 557 at the intermediate nodes 1 and
2. Unlike a conventional device without intermediate node, there is
no big hot spot at the resistor center here, but there are three
smaller hot spots 551 in between the nodes. In addition, compared
to a conventional device without intermediate node, the overall
temperature of the resistor in this embodiment is reduced.
[0053] As shown in FIG. 5, more intermediate nodes inserted between
two ends of the resistor can bring a lower overall temperature and
a flatter temperature distribution for the resistor. On the other
hand, more intermediate nodes may mean more cost for the device. As
such, one can determine an optimal number of intermediate nodes
based on the tradeoff between temperature reduction and cost
increase, as well as other concerns like resistor and node
geometry, performance requirement, etc.
[0054] FIG. 6 illustrates a corresponding cross-sectional view of
one of the exemplary semiconductor devices shown in FIG. 5, in
accordance with some embodiments of the present disclosure. FIG. 6
shows a cross-sectional view 120' for the embodiment (2A). As shown
in the cross-sectional view 120', the resistor 121 has a top
surface 610, a bottom surface 620, and two end portions 630-1,
630-2. There are two end contacts 122-1, 122-2 disposed on the top
surface 610 at the two end portions 630-1, 630-2 of the resistor
121; and two end nodes (node A 128 and node B 129) disposed on the
two end contacts 122-1, 122-2. In addition, the resistor 121 is
covered by a dielectric layer 123 as shown in FIG. 6. An
intermediate node 126 is disposed below the dielectric layer 123
and between the two end portions of the resistor 121. The node 126
in this example includes a plurality of metal layers (heat sink
metals N-1 125-1, N-2 125-2, N-3 125-3, . . . ) and at least one
via (heat sink vias N-1 124-1, N-2 124-2, . . . ) that thermally
couples adjacent metal layers in the plurality of metal layers. The
heat in the center of the resistor 121 can be dissipated via the
node 126 to a large heat sink pool (e.g. a substrate like a bulk or
SOI CMOS) in the semiconductor device. In accordance with some
embodiments, each metal layer or each heat sink metal may be formed
of an aluminum alloy.
[0055] In accordance with some embodiments, one can optimize the
number of metal layers in an intermediate node, based on size of
the device, cost of the device, material of the metal layers, and
material of other portions of the device, etc. It can be understood
that, when there are multiple intermediate nodes disposed below the
resistor, the numbers and/or material of metal layers in different
intermediate nodes can be different. It can also be understood
that, in some embodiments, one resistor may have both an
intermediate metal node disposed on top of the resistor and an
intermediate metal node disposed below the resistor.
[0056] FIG. 7 illustrates top views of a third set of exemplary
semiconductor devices, in accordance with some embodiments of the
present disclosure. FIG. 7 illustrates different versions of
embodiment (3) in FIG. 1. For example, the embodiment (3A) 130 in
FIG. 7 is the same as the embodiment (3) 130 in FIG. 1, where the
resistor includes two sub-resistors connected in series, an
intermediate node is disposed at each end portion of each
sub-resistor, and any two intermediate nodes at two adjacent
sub-resistor ends form a thermally coupled node pair for heat
dissipation of the resistor.
[0057] In embodiment (3B) 720 in FIG. 7, the resistor 721 includes
three sub-resistors connected in series. Two edge taps or end nodes
(node A 728 and node B 729) are disposed on the resistor 721 via
two end contacts 722 to form heat dissipation paths. In addition,
there are intermediate nodes (nodes 1-4, 724, 725, 726, 727)
inserted between the two ends to serve as heat sinks for reducing
temperature of the center area of the resistor 721. In this
embodiment, any two intermediate nodes disposed on two adjacent
ends of two adjacent sub-resistors form a thermally coupled node
pair, e.g. by a single piece of metal covering the two intermediate
nodes. The metal may be either an upper metal 723 disposed on
contacts 722 that are in direct contact with a top surface of the
resistor 721 as shown in FIG. 7, or a lower metal disposed below
indirect contacts below a bottom surface of the resistor 721 (not
shown). As such, heat between the two end portions of the resistor
721 can be dissipated via the coupled node pairs (724-725, 726-727)
to a large heat sink pool, e.g. either up to a mesh power/ground
plane or down to a bulk or SOI CMOS, to further dissipate the heat
out of the semiconductor device. In one example, the intermediate
nodes in embodiment (3B) are not all disposed at end portions of
the sub-resistors, especially when the sub-resistors have different
lengths or sizes. In another example, each of the intermediate
nodes in embodiment (3B) is disposed at an end portion of a
sub-resistor, and any two intermediate nodes at two adjacent
sub-resistor ends form a thermally coupled node pair as shown in
FIG. 7, which can make use of existing heat sink structure to build
up new heat sink insertion for serially connected resistors.
[0058] It can be understood that in some embodiments, the number of
sub-resistors in the resistor can be larger than three. It can also
be understood that in some embodiments, the shapes and/or sizes of
the sub-resistors are different from each other. In some
embodiment, one sub-resistor is wider than another sub-resistor, or
has different material than another sub-resistor. In this case, the
heat sinks (intermediate metal nodes) can be distributed to
correspond to hottest spots on the sub-resistors, e.g. based on
experiments or measurements.
[0059] FIG. 8 illustrates temperature distributions of the
exemplary semiconductor devices shown in FIG. 7, in accordance with
some embodiments of the present disclosure. For the embodiments
(3A) 130 and (3B) 720, FIG. 8 shows corresponding temperature
distributions 810 and 820, respectively, along an axis from node A
to node B of the resistor.
[0060] As shown in FIG. 8, the temperature distribution 810 for the
embodiment (3A) 130 has two low points 818, 819 at the two end
nodes and one low flat region 816 at the intermediate node pair
(nodes 1-2). As the intermediate node pair is located at the center
of the resistor, there is no big hot spot at the resistor center in
contrast to a conventional device without intermediate node pair,
but there are two smaller hot spots 811 in between the nodes. In
addition, compared to a conventional device without intermediate
node pair, the overall temperature of the resistor in this
embodiment is reduced.
[0061] Similarly, the temperature distribution 820 for the
embodiment (3B) 720 has two low points 828, 829 at the two end
nodes and two low flat regions 824, 826 at the intermediate node
pairs (nodes 1-2 and nodes 3-4). Unlike a conventional device
without intermediate node pair, there is no big hot spot at the
resistor center here, but there are three smaller hot spots 821 in
between the nodes. In addition, compared to a conventional device
without intermediate node pair, the overall temperature of the
resistor in this embodiment is reduced.
[0062] As shown in FIG. 8, more intermediate node pairs inserted
between two ends of the resistor can bring a lower overall
temperature and a flatter temperature distribution for the resistor
including multiple sub-resistors connected in series. On the other
hand, more intermediate node pairs may mean more cost for the
device. As such, one can determine an optimal number of
intermediate node pairs as well as an optimal number for the
sub-resistors in the resistor, based on the tradeoff between
temperature reduction and cost increase, as well as other concerns
like sub-resistor and node geometry, performance requirement,
etc.
[0063] FIG. 9 illustrates a corresponding cross-sectional view of
one of the exemplary semiconductor devices shown in FIG. 7, in
accordance with some embodiments of the present disclosure. FIG. 9
shows a cross-sectional view 130' for the embodiment (3A). In the
cross-sectional view 130', each resistor 131 has a top surface 910,
a bottom surface 920, and two end portions 930-1, 930-2. There are
four contacts 132 disposed on the resistors 131, including two end
contacts disposed at the two end portions of each resistor. There
are two end nodes (node A 138 and node B 139) disposed on the two
end contacts 132-1, 132-2 and one intermediate node pair 136-137
disposed on the intermediate contacts 132-3, 132-4. The node pair
136-137 in this example includes a plurality of metal layers (heat
sink metals N 133-1, N+1 133-2, N+2 133-3, . . . ) and at least one
via (heat sink vias N 134-1, 134-2, N+1 134-3, 134-4 . . . ) that
thermally couples adjacent metal layers in the plurality of metal
layers. The heat at the center of the resistor 131, i.e. at the
connected area of the two sub-resistors connected in series in the
resistor 131, can be dissipated via the node pair 136-137 to a
large heat sink pool (e.g. a mesh power/ground plane) in the
semiconductor device.
[0064] It can be understood that, in some embodiments, while the
resistor is divided into multiple sub-resistors, one or more
intermediate metal node pairs can be inserted below the resistor,
and the heat in the center of the resistor can be dissipated via
the one or more intermediate metal node pairs to the substrate of
the device. It can also be understood that, in some embodiments,
one resistor may have both an intermediate metal node pair disposed
on top of the resistor and an intermediate metal node pair disposed
below the resistor.
[0065] In accordance with some embodiments, the contacts on top of
a resistor may be formed of Tungsten. In accordance with some
embodiments, each metal layer or each heat sink metal may be formed
of an aluminum alloy. In accordance with some embodiments, one can
optimize the number of metal layers in an intermediate node pair,
based on size of the device, cost of the device, material of the
metal layers, and material of other portions of the device, etc. It
can be understood that, when there are multiple intermediate node
pairs on the resistor, the numbers and/or material of metal layers
in different intermediate node pairs can be different.
[0066] FIG. 10 illustrates a geometry design for the first set of
exemplary semiconductor devices shown in FIG. 2, in accordance with
some embodiments of the present disclosure. In embodiment (1) 110,
the resistor 111 has a resistor length L 1001 that is equal to a
distance between the two end nodes, and has a resistor width W 1002
as shown in FIG. 10. The inserted intermediate heat sink metal has
a metal length 1003 and a metal width 1004. To be more specific,
when the heat sink node includes multiple metal layers, each heat
sink metal layer may have a different metal length or width.
[0067] A goal of the geometry design for the heat sink node here is
to reduce the parasitic capacitance in the semiconductor device.
Before inserting the node, there is a parasitic capacitance between
the resistor and the substrate of the device. The parasitic
capacitance is proportional to a common area between the two plates
forming the capacitance. In embodiment (1) as shown in FIG. 10,
because the node is disposed on top of the resistor and is
electrically connected to the resistor via a contact, the heat sink
metal node insertion will not introduce much additional parasitic
capacitance, especially when the node is fully covered or blocked
by the resistor from the substrate, i.e. when there is no vertical
straight line that can connect the node and the substrate without
penetrating the resistor.
[0068] In some embodiments, the intermediate metal has a same
geometry shape as the resistor and is placed in parallel with the
resistor. As shown in FIG. 10, both the heat sink metal and the
resistor have a rectangular shape in the top view of the
device.
[0069] When the metal nodes include multiple metal layers, the
metal layers include: a first metal layer (heat sink metal N) in
contact with the corresponding contact on the resistor, and other
metal layers (heat sink metal N+i, i=1, 2 . . . ) disposed over the
first metal layer. In some embodiments, each of the plurality of
metal layers has a same shape as that of the resistor. In some
embodiments, an area of each metal layer is smaller than or equal
to that of the resistor.
[0070] In some embodiments, the first layer (heat sink metal N)
has: (a) a first metal length 1003 that is less than or equal to
the resistor length L 1001, and (b) a first metal width 1004 that
is less than or equal to the resistor width W 1002; and each of the
other layers (heat sink metal N+i) has: (c) a metal length 1003-i
that is greater than or equal to the first metal length 1003, and
(d) a metal width 1004-i that is greater than or equal to the first
metal width 1004. In some embodiments, the first layer (heat sink
metal N) has: (a) a first metal length 1003 that is selected from a
range between 0.1*L and 1 L, and (b) a first metal width 1004 that
is selected from a range between 0.1*W and 40 W; and each of the
other layers (heat sink metal N+i) has: (c) a metal length 1003-i
that is selected from a range between 0.1*L and 40 L, and (d) a
metal width 1004-i that is selected from a range between 0.1*W and
40 W.
[0071] FIG. 11 illustrates a geometry design for the second set of
exemplary semiconductor devices shown in FIG. 5, in accordance with
some embodiments of the present disclosure. In embodiment (2) 120,
the resistor 121 has a resistor length L 1101 that is equal to a
distance between the two end nodes, and has a resistor width W 1102
as shown in FIG. 11. The inserted intermediate heat sink metal has
a metal length 1103 and a metal width 1104. To be more specific,
when the heat sink node includes multiple metal layers, each heat
sink metal layer may have a different metal length or width.
[0072] In embodiment (2) as shown in FIG. 11, because the node is
disposed between the resistor and the substrate, and is not
directly electrically connected to the resistor, the heat sink
metal node insertion may introduce some additional parasitic
capacitance to the device.
[0073] In some embodiments, the intermediate metal has a same
geometry shape as the resistor and is placed in parallel with the
resistor. As shown in FIG. 11, both the heat sink metal and the
resistor have a rectangular shape in the top view of the
device.
[0074] When the metal nodes include multiple metal layers, the
metal layers include: a first metal layer (heat sink metal N-1) in
contact with the dielectric layer under the resistor, and other
metal layers (heat sink metal N-i, i=2, 3 . . . ) disposed below
the first metal layer. In some embodiments, each of the plurality
of metal layers has a same shape as that of the resistor. In some
embodiments, an area of each metal layer is smaller than or equal
to that of the resistor.
[0075] In some embodiments, the first layer (heat sink metal N-1)
has: (a) a first metal length 1103-1 that is less than or equal to
the resistor length L 1101, and (b) a first metal width 1104 that
is less than or equal to the resistor width W 1102; and each of the
other layers (heat sink metal N-i) has: (c) a metal length 1103-i
(i=2, 3 . . . ) that is greater than or equal to the first metal
length 1103, and (d) a metal width 1104-i (i=2, 3 . . . ) that is
greater than or equal to the first metal width 1104. In some
embodiments, the first layer (heat sink metal N-1) has: (a) a first
metal length 1103 that is selected from a range between 0.1*L and
IL, and (b) a first metal width 1104 that is selected from a range
between 0.1*W and 40 W; and each of the other layers (heat sink
metal N-i) has: (c) a metal length 1103-i (i=2, 3 . . . ) that is
selected from a range between 0.1*L and 40L, and (d) a metal width
1104-i (i=2, 3 . . . ) that is selected from a range between 0.1*W
and 40 W.
[0076] It can be understood that a geometry design for exemplary
semiconductor devices in embodiment (3) can follow a similar manner
to the geometry design for embodiments (1) and (2) shown in FIG. 10
and FIG. 11, respectively.
[0077] FIG. 12 is a flow chart illustrating an exemplary method
1200 for forming a semiconductor device, in accordance with some
embodiments of the present disclosure. As shown in FIG. 12, a
resistor is formed at 1202, where the resistor has a top surface, a
bottom surface, and two end portions. Two end contacts are formed
at 1204 on the top surface at the two end portions respectively. At
1206, at least one intermediate contact is formed on the top
surface between the two end contacts. Two end metal nodes are
formed at 1208 on the two end contacts respectively. At 1210, at
least one intermediate metal node is formed on the at least one
intermediate contact.
[0078] FIG. 13 is a flow chart illustrating another exemplary
method 1300 for forming a semiconductor device, in accordance with
some embodiments of the present disclosure. As shown in FIG. 13, a
resistor is formed at 1302, where the resistor has a top surface, a
bottom surface, and two end portions. Two end contacts are formed
at 1304 on the top surface at the two end portions respectively.
Two end metal nodes are formed at 1306 on the two end contacts
respectively. A dielectric layer is formed at 1308 below the bottom
surface. At 1310, at least one intermediate metal node is formed
below the dielectric layer and between the two end portions.
[0079] FIG. 14 is a flow chart illustrating yet another exemplary
method 1400 for forming a semiconductor device, in accordance with
some embodiments of the present disclosure. As shown in FIG. 14, a
resistor layer comprising a plurality of resistors connected in
series is formed at 1402, where each of the plurality of resistors
has a top surface, a bottom surface, and two end portions. Two end
contacts are formed at 1404 on the top surface of each resistor at
the two end portions of the resistor respectively. A metal node is
formed at 1406 on each contact. At 1408, any two metal nodes
disposed over two adjacent end portions of two resistors are
thermally coupled, to form a pair of coupled metal nodes.
[0080] It can be understood that the order of the steps shown in
each of FIG. 12, FIG. 13, and FIG. 14 may be changed according to
different embodiments of the present disclosure.
[0081] In an embodiment, a semiconductor device is disclosed. The
semiconductor device includes: an electronic component having a top
surface, a bottom surface, and two end portions; a plurality of
contacts disposed on the top surface; and a plurality of metal
nodes disposed on the plurality of contacts. The plurality of
contacts includes two end contacts disposed at the two end portions
respectively and at least one intermediate contact disposed between
the two end contacts. The plurality of metal nodes includes two end
metal nodes disposed on the two end contacts respectively and at
least one intermediate metal node disposed on the at least one
intermediate contact.
[0082] In another embodiment, a semiconductor device is disclosed.
The semiconductor device includes: an electronic component having a
top surface, a bottom surface, and two end portions; two end
contacts disposed on the top surface and at the two end portions
respectively; two end metal nodes disposed on the two end contacts
respectively; a dielectric layer disposed below the bottom surface;
and at least one intermediate metal node disposed below the
dielectric layer and between the two end portions.
[0083] In yet another embodiment, a semiconductor device is
disclosed. The semiconductor device includes: an electronic
component layer including a plurality of electronic components
connected in series; a contact layer including a plurality of end
contacts disposed on the electronic component layer; and a first
metal node layer including a first plurality of metal nodes
disposed on the contact layer. Each of the plurality of electronic
components has a top surface, a bottom surface, and two end
portions. The plurality of end contacts includes two end contacts
disposed on the top surface of each of the plurality of electronic
components. The two end contacts are disposed at the two end
portions of the electronic component, respectively. Each of the
first plurality of metal nodes is disposed on a corresponding one
of the plurality of end contacts. Among the first plurality of
metal nodes, any two metal nodes disposed over two adjacent end
portions of two electronic components are thermally coupled to form
a pair of coupled metal nodes.
[0084] The foregoing outlines features of several embodiments so
that those ordinary skilled in the art may better understand the
aspects of the present disclosure. Those skilled in the art should
appreciate that they may readily use the present disclosure as a
basis for designing or modifying other processes and structures for
carrying out the same purposes and/or achieving the same advantages
of the embodiments introduced herein. Those skilled in the art
should also realize that such equivalent constructions do not
depart from the spirit and scope of the present disclosure, and
that they may make various changes, substitutions, and alterations
herein without departing from the spirit and scope of the present
disclosure.
* * * * *