U.S. patent application number 10/960534 was filed with the patent office on 2005-02-24 for high-frequency semiconductor device.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Kanazawa, Kunihiko, Nakatani, Seiichi, Takehara, Hideki, Yoshikawa, Noriyuki.
Application Number | 20050040522 10/960534 |
Document ID | / |
Family ID | 19136632 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050040522 |
Kind Code |
A1 |
Takehara, Hideki ; et
al. |
February 24, 2005 |
High-frequency semiconductor device
Abstract
A high-frequency semiconductor device is provided with a ceramic
substrate, an element group including semiconductor elements and
passive components mounted onto a bottom portion of the ceramic
substrate, and a composite resin material layer formed on the
bottom portion of the ceramic substrate so as to bury the element
group. The composite resin material layer is formed by a composite
resin material including an epoxy resin and an inorganic filler
material, and has a flat bottom surface on which electrodes for
connecting to the outside are formed. As packaging of a structure
in which the receiving system and the transmitting system are
formed in a single unit, such as an RF module, the high-frequency
semiconductor device achieves a small size, a high mounting
density, and excellent heat release properties.
Inventors: |
Takehara, Hideki; (Kobe-shi,
JP) ; Yoshikawa, Noriyuki; (Ibaraki-shi, JP) ;
Kanazawa, Kunihiko; (Mukou-shi, JP) ; Nakatani,
Seiichi; (Hirakata-shi, JP) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Kadoma-shi
JP
|
Family ID: |
19136632 |
Appl. No.: |
10/960534 |
Filed: |
October 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10960534 |
Oct 7, 2004 |
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10634281 |
Aug 4, 2003 |
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6818979 |
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10634281 |
Aug 4, 2003 |
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10271863 |
Oct 15, 2002 |
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6815810 |
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Current U.S.
Class: |
257/723 ;
257/728; 257/E23.178; 438/109 |
Current CPC
Class: |
H01L 2224/45144
20130101; H01L 2224/45144 20130101; H01L 2924/12041 20130101; H01L
2924/00014 20130101; H01L 2924/00014 20130101; H01L 24/48 20130101;
H01L 2924/14 20130101; H01L 2924/181 20130101; H01L 2924/12041
20130101; H01L 2924/3011 20130101; H05K 1/112 20130101; H05K 1/183
20130101; H01L 23/66 20130101; H01L 2924/16152 20130101; H01L
2924/01019 20130101; H01L 2924/181 20130101; H01L 2924/19041
20130101; H05K 1/0306 20130101; H05K 1/186 20130101; H01L
2924/09701 20130101; H05K 3/284 20130101; H01L 23/3121 20130101;
H01L 2924/3025 20130101; H01L 2224/16225 20130101; H01L 2924/01078
20130101; H01L 24/45 20130101; H01L 2224/48091 20130101; H01L
23/5389 20130101; H01L 2924/14 20130101; H01L 2224/48227 20130101;
H05K 3/4614 20130101; H01L 2224/48227 20130101; H01L 2224/48091
20130101; H05K 3/4629 20130101; H01L 2924/01057 20130101; H01L
2924/19105 20130101; H01L 2924/01079 20130101; H01L 2924/00014
20130101; H01L 2224/45015 20130101; H01L 2924/00014 20130101; H01L
2924/00 20130101; H01L 2924/00015 20130101; H01L 2924/00 20130101;
H01L 2924/207 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/723 ;
438/109; 257/728 |
International
Class: |
H01L 021/48; H01L
023/34 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2001 |
JP |
2001-319019 |
Claims
1.-7. (CANCELED)
8. A high-frequency semiconductor element comprising: a ceramic
substrate having a cavity portion in its bottom portion; an element
group including semiconductor elements and passive components
mounted to the bottom portion of the cavity portion; a composite
resin material layer formed so as to bury the element group in the
cavity portion; and electrodes for connecting to the outside that
are formed on a bottom portion of the ceramic substrate other than
at the cavity portion; wherein the composite resin material layer
is formed by a composite resin material including an epoxy resin
and an inorganic filler material, and a bottom portion of the
composite resin material layer is flat in shape.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to structures for
high-frequency semiconductor devices on which high-frequency
semiconductor elements, control integrated circuit elements, and
surrounding circuits are mounted, and in particular to packaging
structures thereof.
[0003] 2. Description of the Related Art
[0004] There is an increasing demand for high-frequency
semiconductor devices employed primarily in mobile communications
equipment, such as portable telephones, as "all-in-one" RF modules
with receiving and transmitting systems formed into a single unit.
According to such situation, a need has arisen for a reduction in
packaging size, under the condition that the number of
semiconductor elements and chip components that are mounted
increases due to the provision of high-frequency semiconductor
elements, control integrated circuit elements and surrounding
circuitry in order to incorporate receiving and transmitting
systems into a single unit.
[0005] A conventional example of a high-frequency semiconductor
device is described with reference to FIG. 10. In FIG. 10, numeral
1 denotes a semiconductor element of a chip form such as a
transistor and 2 denotes a ceramic multilayer substrate. Numeral 3
denotes chip components such as chip resistors, chip capacitors,
and chip inductors. Numeral 4 denotes bottom electrodes, 5 denotes
metal wires, 6 denotes potting resin, and 7 denotes a metal
cap.
[0006] Component mounting lands for mounting the semiconductor
element 1 and the chip components 3 and an electrode wiring pattern
(not shown) are formed on the surface of the ceramic multilayer
substrate 2 through screen printing or metal thin film etching, for
example. The semiconductor element 1 is die bonded to the component
mounting land portion on the ceramic multilayer substrate 2, and
connected to the electrode wiring pattern that is formed on the
surface of the ceramic multilayer substrate 2 by the metal wires 5.
The semiconductor element 1 and the metal wires 5 are covered by
the potting resin 6. The chip components 3 are mounted to
predetermined locations by soldering. The metal cap 7, which forms
the packaging, is attached to the ceramic multilayer substrate 2.
The electrode wiring pattern on the surface of the ceramic
multilayer substrate 2 is connected electrically to the bottom
electrodes 4 via through holes, which are not shown, that pass
through the ceramic multilayer substrate 2.
[0007] However, with structures where semiconductor elements and
chip components are simply mounted onto the ceramic multilayer
substrate 2, as is the case with the conventional high-frequency
semiconductor device described above, the desired reduction in the
packaging size cannot be met sufficiently as the number of
installed components increases.
[0008] Also, the semiconductor chip provided on the ceramic
multilayer substrate is a heat-generating element such as a power
amplifier, and thus all the heat generated from the semiconductor
chip is transferred to the bottom portion via the ceramic
multilayer substrate and released from the bottom portion
electrodes. However, the ceramic multilayer substrate has a high
thermal resistance. This led to the problem of not enough heat
being released from the semiconductor chip, which consumes a large
amount of power, and the semiconductor chip becoming hot.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
high-frequency semiconductor device in which receiving and
transmitting systems including active elements such as
semiconductor elements like power amplifiers and switches or
semiconductor elements for control and passive components such as
resistors, capacitors, inductors, and filters, are mounted as a
single unit in a layered substrate, so as to improve electrical
properties by reducing impedance due to the reduction in the wiring
length, reducing the floating capacity, and improving anti-noise
properties, and to provide a smaller size device with improved heat
release properties.
[0010] A high-frequency semiconductor device of the present
embodiment is provided with a ceramic substrate, an element group
including semiconductor elements and passive components mounted
onto a bottom portion of the ceramic substrate, and a composite
resin material layer formed on the bottom portion of the ceramic
substrate so as to bury the element group. The composite resin
material layer is formed of a composite resin material including an
epoxy resin and an inorganic filler material, and has a flat bottom
surface on which electrodes for connecting to the outside are
formed.
[0011] With this configuration, the semiconductor elements and
passive components are mounted on the bottom portion of the ceramic
substrate, so that the bottom surface of the substrate can be
utilized as the mounting area and the mounting density can be
increased. Also, by burying the element group in the composite
resin material layer, an increase in reliability, such as
mechanical resistance and resistance against moisture, can be
achieved. Moreover, by making the bottom surface of the composite
resin material layer flat and providing the electrodes for
connecting to the outside, the product is easily transported and
handled, and the ability to mount the high-frequency semiconductor
device as a module is improved.
[0012] It is preferable that the semiconductor elements are mounted
by ffip-chip connection. Thus, a drop in impedance due to the
reduction in wiring length, a reduction in the floating capacity,
an increase in the mounting density, and reduction in the height of
the packaging can be achieved.
[0013] The high-frequency semiconductor device mentioned above can
be given a structure where interlayer connector structures are
formed in the composite resin material layer, the interlayer
connector structures being filled with a high thermal conductivity
resin material having thermal conductivity higher than that of the
epoxy resin, the electrodes for connecting to the outside include a
ground electrode that functions as a heat release electrode, and
the surface of the semiconductor element is connected to the ground
electrode via the interlayer connector structures. Thus, heat
generated by the semiconductor elements, which are heat-generating
elements such as power amplifiers and mounted by flip-chip
connection, can be adequately released from the electrodes for
connecting to the outside via the interlayer connector structures
provided in a single or a plurality of locations.
[0014] Another high-frequency semiconductor device of the present
invention is provided with a first ceramic substrate having a
circuit pattern, a second ceramic substrate on which semiconductor
elements are mounted, and a composite resin material layer that
buries the semiconductor elements and is provided between the first
ceramic substrate and the second ceramic substrate. The composite
resin material layer is formed by a composite resin material
including an epoxy resin and an inorganic filler material,
interlayer connector structures in which a conducting resin
material has been filled are formed in the composite resin material
layer, and the circuit pattern of the first ceramic substrate and a
circuit pattern of the second ceramic substrate are electrically
connected via the interlayer connector structures.
[0015] According to this configuration, the first ceramic substrate
and the second ceramic substrate are employed according to the
electrical, thermal, and mechanical properties that are required,
and are deposited with the composite resin layer interposed between
them, so that a small size substrate packaging can be formed. Even
if the linear expansion coefficients of the first ceramic substrate
and the second ceramic substrate are different, a highly reliable
packaging that absorbs this difference can be provided, because the
composite resin layer is interposed between the substrates. In
addition to the fact that semiconductor elements and passive
component can be mounted between the first ceramic substrate and
the second ceramic substrate, it is also possible to mount
components on the upper surface of the first substrate, and thus
the overall mounting density of the product can be increased.
Moreover, by burying the semiconductor elements, for example, with
the composite resin, reliability such as mechanical resistance and
resistance against moisture can be increased.
[0016] In this configuration, it is preferable that the
semiconductor elements provided on the second ceramic substrate
have been mounted by flip-chip connection. Thus, the thickness of
the composite resin material layer between the first ceramic
substrate and the second ceramic substrate can be reduced. Also, a
drop in impedance due to the reduction in wiring length, a
reduction in the floating capacity, an increase in the mounting
density, and a reduction in the packaging height can be
achieved.
[0017] Additionally, it is possible to adopt a configuration in
which at least one of the semiconductor elements provided on the
second ceramic substrate is connected by metal wires. Thus, those
elements of the semiconductor elements that are mounted onto the
second ceramic substrate for which the release of heat is required
can be adhered by a high conductivity adhesive agent and connected
to the substrate by the metal wire, so that heat can be dissipated
from those elements directly to the second ceramic substrate. This
configuration is particularly effective when a large amount of heat
is generated by the semiconductor elements.
[0018] In this configuration, the surroundings of the semiconductor
elements provided on the second ceramic substrate and connected by
the metal wire can be sealed by a liquid epoxy resin. Thus, stress
that is applied to the semiconductor elements and the metal wire
when the first ceramic substrate and the second ceramic substrate
are adhered by the composite resin material can be alleviated, so
that defects such as the wire falling over or being disconnected
can be eliminated, and the assembly yield can be increased.
Moreover, the epoxy resin that seals the semiconductor elements can
be employed as a spacer for the first ceramic substrate and the
second ceramic substrate, so that the gap between the two
substrates can be adjusted.
[0019] A further high-frequency semiconductor device according to
the present invention is provided with a ceramic substrate having a
cavity portion in its bottom portion, an element group including
semiconductor elements and passive components mounted to the bottom
portion of the cavity portion, a composite resin material layer
formed so as to bury the element group in the cavity portion, and
electrodes for connecting to the outside that are formed on a
bottom portion of the ceramic substrate other than at the cavity
portion. The composite resin material layer is formed by a
composite resin material including an epoxy resin and an inorganic
filler material, and a bottom portion of the composite resin
material layer is flat in shape.
[0020] As in the configuration mentioned above, this configuration
achieves an increase in the mounting density, an increase in device
reliability such as in the mechanical resistance and in the
resistance against moisture, and an increase in mountability.
Additionally, the composite resin material layer can easily be
formed by filling a composite resin material into the cavity
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 1 of the invention
[0022] FIG. 2 is a perspective view of the high-frequency
semiconductor device of FIG. 1 seen from its rear side.
[0023] FIG. 3 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 2 of the
invention.
[0024] FIG. 4 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 3 of the
invention.
[0025] FIG. 5 is a perspective view of the high-frequency
semiconductor device of FIG. 4 seen from its rear side.
[0026] FIG. 6 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 4 of the
invention.
[0027] FIG. 7 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 5 of the
invention.
[0028] FIG. 8 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 6 of the
invention.
[0029] FIG. 9 is a cross-sectional view showing a high-frequency
semiconductor device according to Embodiment 7 of the
invention.
[0030] FIG. 10 is a cross-sectional view showing a conventional
example of a high-frequency semiconductor device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] First Embodiment
[0032] FIG. 1 is a cross-sectional view of a high-frequency
semiconductor device according to Embodiment 1 of the present
invention. FIG. 2 is a perspective view of the high-frequency
semiconductor device of FIG. 1 seen from its rear side.
[0033] In FIG. 1, the numeral 1a denotes a gallium-arsenide power
semiconductor element serving as a power amplifier, 1b denotes a
gallium-arsenide semiconductor element serving as a switching
element, and 1c denotes a silicon semiconductor element for circuit
control. Numeral 2 denotes a non-shrinkage ceramic multilayer
substrate, which incorporates in its inner layers printed resistors
8 and printed capacitors 9 formed by printing a paste material that
includes metal, and which may be formed by baking at a low
temperature. Numeral 3 denotes a chip component such as, for
example, a chip capacitor for fine-tuning the high-frequency
circuit constants. Numeral 5 denotes metal wires, and 10 denotes a
composite resin material layer including an epoxy resin and an
inorganic filler such as silica. Numeral 4 denotes electrodes for
connecting to the outside which may be made of a conductor formed
on the bottom surface of the composite resin material layer 10.
Numeral 11 denotes a plurality of interlayer connector via holes
formed in the composite resin material layer 10 and functioning as
an interlayer connector structure, and numeral 12 denotes a
conducting resin buried in each interlayer connector via hole
11.
[0034] Although not shown in the drawings, an electrode wiring
pattern and a component mounting land for mounting the chips of the
semiconductor elements 1a, 1b, and 1c and the chip component are
formed on the bottom surface of the ceramic multilayer substrate 2
by screen printing or metal thin film etching. The gallium-arsenide
power semiconductor element 1a, the gallium-arsenide semiconductor
element 1b, and the silicon semiconductor element 1c may be die
bonded to the component mounting land portion on the bottom surface
of the ceramic multilayer substrate 2 by soldering, for example,
and are connected with the metal wires 5 to the electrode wiring
pattern that is formed on the bottom surface of the ceramic
multilayer substrate 2. In addition, although not shown in the
drawings, a plurality of passive components such as chip resistors,
chip capacitors, and chip inductors may be fastened and connected
by soldering or the like to the circuit pattern that is formed on
the bottom surface of the ceramic multilayer substrate 2.
[0035] The chip dimensions of the semiconductor elements 1a, 1b,
and 1c are ordinarily 1.6 mm.times.0.6 mm and 100 .mu.m thickness
for the power amplifier element; 0.8 mm.times.0.6 mm and 150 .mu.m
thickness for the switching element; and 1.0 mm.times.0.7 mm and
300 .mu.m thickness for the control element.
[0036] The semiconductor elements 1a, 1b, 1c and the passive
elements are buried by the composite resin material layer 10. As
shown in FIG. 2, the bottom portion of the composite resin material
layer 10 is flat and serves as a flat electrode surface. Moreover,
as shown in FIG. 1, the plurality of the interlayer connector via
holes 11 are formed in the composite resin material layer 10, and
conducting resin 12 is filled into the interlayer connector via
holes 11. The interlayer connector via holes 11 match the position
of the electrodes 4 for connecting to the outside.
[0037] The interlayer connector via holes 11 act both to contact
the circuit pattern that is formed on the bottom surface of the
ceramic multilayer substrate 2 with the electrodes 4 for connecting
to the outside, and to release heat that is generated by the
semiconductor elements 1a, 1b, and 1c via the ceramic multilayer
substrate 2. The via holes may have a diameter of 200 .mu.m.phi.
and are filled with a copper-based paste serving as the conducting
resin 12. An electrode wiring pattern may be formed on the upper
surface of the ceramic multilayer substrate 2, and a plurality of
chip components 3, such as chip resistors, chip capacitors, and
chip inductors, may be fastened and connected to the electrode
pattern on the upper surface by soldering or the like.
[0038] The high-frequency circuit constant is determined by the
passive elements that are buried by the composite resin material 10
and the printed resistors 8 and the printed capacitors 9, which are
formed between the layers of the ceramic multilayer substrate 2,
and the high-frequency circuit constant is fine-tuned at each
high-frequency semiconductor device with the chip components 3 that
are connected to the upper surface of the ceramic multilayer
substrate 2. Also, although not shown in the drawings, the
electrode pattern formed on the upper surface of the ceramic
multilayer substrate 2, the printed resistors 8, the printed
capacitors 9, the electrode pattern formed between the layers of
the ceramic multilayer substrate 2, and the electrode pattern
formed on the bottom surface of the ceramic multilayer substrate 2
are electrically connected to one another via through holes that
pass through the ceramic multilayer substrate 2, as
appropriate.
[0039] The thickness of the composite resin material layer 10 is
determined by the height of the semiconductor elements and the
passive components that are mounted. Here, this value can be
slightly above or below the standard for the thickness at the
semiconductor elements 1a, 1b, and 1c, which is the wire loop
height of the metal wire 5 plus 300 .mu.m, or the standard for the
thickness at the passive components, which is the component height
plus 300 .mu.m.
[0040] The ceramic multilayer substrate 2 can be formed by using an
alumina substrate (high temperature cofired ceramics (HTCC)
substrate), a low temperature cofired ceramics (LTCC) substrate,
and so on. Generally, the "alumina substrate" means the HTCC
substrate. Both of them contain alumina as a main component and the
content thereof is higher in HTCC than in LTCC. Cofiring
temperature is 1300.degree. C. to 1500.degree. C. for HTCC and
800.degree. C. to 900.degree. C. for LTCC.
[0041] The composite resin material layer 10 may be formed by
using, for example, a sheet obtained by mixing epoxy resin with 70
to 80% by weight of an inorganic filler material (mainly silica),
coupling agent, pigment, solvent, etc., kneading them, and forming
into a sheet with uniform thickness. The coupling agent adheres to
the inorganic filler material and increases wettability of the
inorganic filler material with respect to the epoxy resin. In order
to couple the composite resin material layer 10 to the ceramic
multilayer substrate 2 as shown in FIGS. 1 and 2, the composite
resin material layer 10 is superposed on the ceramic multilayer
substrate 2 with chips mounted and they are subjected to
hot-pressing to be formed.
[0042] The composite resin material layer 10 may be formed also by
using a solventless sheet in which a solvent is not added. In such
case the sheet is made of a liquid epoxy resin with an inorganic
filler material (mainly silica) added.
[0043] As the conducting resin 12, Ag paste (adhesive resin with
silver added as a filler) may be used generally. The composite
resin material layer 10 is subjected to punching to form holes and
then Ag paste is filled into the holes by a printing method. When
the composite resin material layer 10 and the ceramic multilayer
substrate 2 with chips mounted are superposed with each other and
subjected to hot-pressing to be formed, Ag paste is cured together
with the composite resin material layer 10. Also Cu paste may be
used as the conducting resin 12. However it is oxidized easily
compared to Ag paste.
[0044] In the foregoing description, silica was used as an example
of the inorganic filler for the composite resin material layer 10,
but the filler material can be chosen according to properties that
are required. For example, if high heat-release properties are
required, then alumina can be used as the filler material, which
would permit adequate heat release.
[0045] The electrodes 4 for connecting to the outside that are
formed on the rear surface of the composite resin material layer 10
have a flat rear surface, and thus as a module, the high-frequency
semiconductor device easily can be transported and handled during
manufacturing and installed by the user.
[0046] Embodiment 2
[0047] Embodiment 2 of the present invention is described with
reference to the cross-sectional view of the high-frequency
semiconductor device shown in FIG. 3.
[0048] The device of FIG. 3 differs from that according to
Embodiment 1 shown in FIG. 1 in that the gallium-arsenide power
semiconductor element 1a, the gallium-arsenide semiconductor
element 1b, and the silicon semiconductor element 1c are flip-chip
connected on the circuit pattern on the bottom surface of the
ceramic multilayer substrate 2 via bumps 13 having a metal
core.
[0049] The bumps 13 are formed through SBB (stud ball bonding)
using gold wire, and maintain a gap of approximately 40 .mu.m
between the semiconductor elements 1a, 1b, and 1c and the ceramic
multilayer substrate 2. Other techniques that can be employed to
provide the bumps 13 include a technique employing plating around a
copper core material serving as the core and adhering with a
conductive resin, a technique employing an ACF (anisotropic
conductive film), and a technique employing a soldering material.
Any of these techniques can be employed to achieve the same effect.
Compared to the case in which the semiconductor elements 1a, 1b,
and 1c are fastened to the substrate and they are connected by the
metal wire, the height after installation can be reduced by
approximately one half. In this embodiment, the standard for the
thickness of the composite resin material layer 10 after sealing is
the chip height plus 300 .mu.m.
[0050] When the semiconductor elements are flip-chip mounted onto
the bottom surface of the ceramic substrate in this way, they can
be disposed in closer proximity to one another than when connected
on the substrate via metal wiring, and components can be installed
on the upper surface of the substrate as well, so that the
installation density of the entire product is increased.
[0051] Moreover, electrical property effects such as a lower
impedance due to the reduced wiring length and a reduction in the
floating capacity also may be achieved.
[0052] Embodiment 3
[0053] Embodiment 3 of the invention is described in reference to
the cross-sectional view of the high-frequency semiconductor device
shown in FIG. 4 and the perspective view of the device of FIG. 4
seen from its rear side shown in FIG. 5.
[0054] The device of FIG. 4 differs from that according to
Embodiment 2 shown in FIG. 3 in that interlayer connector via holes
21 are formed directly below the gallium-arsenide power
semiconductor element 1a, which is a power amplifier, and a
heat-release electrode 14 is formed on the bottom surface of the
composite resin material layer 10 in alignment with the positions
of the interlayer connector via holes 21. As shown in FIG. 5, a
plurality of electrodes 4 for connecting to the outside and the
heat release electrode 14, which has a larger area than the
electrodes 4 for connecting to the outside, are formed on the
bottom surface of the composite resin material layer 10.
Accordingly, heat can be released effectively from the electrode of
the gallium-arsenide power semiconductor element 1a via the
interlayer connector via holes 21. The heat release electrode 14
also serves as a ground electrode, and suitably grounds the
high-frequency semiconductor element to the ground potential.
[0055] The diameter of the interlayer connector via holes 21 can be
suitably chosen within a range of 150 .mu.m.phi. to 500 .mu.m.phi..
A single or a plurality of via holes 21 can be formed in
correspondence with the chip size of the gallium-arsenide power
semiconductor element 1a. In one example, a high thermal
conductivity resin 22 is filled into the via holes 21. The high
thermal conductivity resin 22 has thermal conductivity higher than
that of epoxy resin. Similar effects can also be achieved by
filling into the via holes 21 the conductive resin 12 that is used
in the interlayer connector via holes 11.
[0056] One example of the high thermal conductivity resin 22 is
composed of epoxy resin with 80 to 90% by weight of alumina added
as a filler. Thermal conductivity thereof is more than 3
W/m.multidot.K. It may be filled into the via holes 21 formed in
the composite resin material layer 10 by a printing method.
[0057] According to this embodiment, when the semiconductor element
is a flip-chip mounted power device that generates a large amount
of heat, the heat from the semiconductor can be suitably
dissipated.
[0058] Embodiment 4
[0059] Embodiment 4 of the present invention is described with
reference to the cross-sectional view of the high-frequency
semiconductor device shown in FIG. 6. The high-frequency
semiconductor device according to this embodiment has a structure
in which the ceramic multilayer substrate 2 (first substrate) and
an alumina substrate 32 (second substrate) sandwich the composite
resin material layer 10, and in this state are adhered to one
another to form a single unit.
[0060] The ceramic multilayer substrate 2 may be a non-shrinkage
substrate formed through baking at low temperatures, and
incorporates in its inner layers a printed resistor 8 and printed
capacitors 9 formed by printing a paste material that includes
metal. The alumina substrate 32 is a substrate on which
gallium-arsenide semiconductor elements 1a and 1b, such as power
amplifiers and switches, and a silicon semiconductor element 1c for
circuit control have been flip-chip mounted.
[0061] Via holes 11 for electrically connecting the ceramic
multilayer substrate 2 and the alumina substrate 32 are formed in
the composite resin material layer 10, and the conducting resin 12
is filled into the via holes 11. The via holes 11 may have a
diameter of 200 .mu.m and are filled with a copper-based paste.
Although not shown, through holes are provided in the alumina
substrate 32 so as to electrically connect the electrodes 4 for
connecting to the outside and the heat release electrode 14 to the
electrode pattern on the surface of the alumina substrate 32.
[0062] Thus, by using the composite resin material layer 10 to
adhere the plurality of substrates 2 and 32, the problem of
peeling, for example, due to differences in the linear expansion
coefficient is eliminated, and because the semiconductor elements
1a, 1b, and 1c are included in the adhesion layer, the component
mounting density, the mechanical resistance, and the resistance
against moisture are improved.
[0063] Embodiment 5
[0064] Embodiment 5 of the present invention is described in
reference to the cross-sectional view of the high-frequency
semiconductor device shown in FIG. 7.
[0065] The device in FIG. 7 differs from that according to
Embodiment 4 shown in FIG. 6 in that, of the semiconductor elements
that are provided on the alumina substrate 32, the gallium-arsenide
power semiconductor element 1a, which is for example a power
amplifier and requires the release of heat, is adhered by a high
thermal conductivity adhesive agent (not shown), and is connected
to the alumina substrate 32 by the metal wire 5. Thus, heat can be
released from the gallium-arsenide power semiconductor element 1a
directly to the alumina substrate 32. Adhering the element directly
onto the alumina substrate 32 results in a large heat transfer
effect, and the further effect of releasing heat via the metal wire
5 can be observed. This embodiment is particularly effective when a
large amount of heat is generated by an element.
[0066] Embodiment 6
[0067] Embodiment 6 of the present invention is described in
reference to the cross-sectional view of a high-frequency
semiconductor device shown in FIG. 8. The device of FIG. 8 differs
from that according to Embodiment 5 shown in FIG. 7 in that before
the ceramic multilayer substrate 2 and the alumina substrate 32 are
adhered via the composite resin material layer 10, the
circumference of the gallium-arsenide power semiconductor element
1a and the metal wire 5 for connection that are disposed on the
alumina substrate 32 is sealed by a liquid epoxy resin 6.
[0068] The amount of epoxy resin 6 can be enough to entirely cover
the power semiconductor element 1a and the metal wire 5, and
considering the resin spread when the epoxy resin 6 is cured, a
highly thixotropic resin can be chosen as the epoxy resin 6. Thus,
when the ceramic multilayer substrate 2 and the alumina substrate
32 are adhered via the composite resin material layer 10, the
stress to the semiconductor element 1a and the metal wire 5 can be
alleviated, so that defects such as the metal wire falling down or
being disconnected are avoided and the assembly yield can be
increased. Also, the epoxy resin 6 for sealing the semiconductor
element 1a can be utilized as a spacer between the ceramic
multilayer substrate 2 and the alumina substrate 32, so that the
gap between these substrates can be adjusted.
[0069] Embodiment 7
[0070] Embodiment 7 of the present embodiment is described in
reference to the cross-sectional view of the high-frequency
semiconductor element shown in FIG. 9. The device of FIG. 9 differs
from that according to Embodiment 2 shown in FIG. 3 in that the
ceramic multilayer substrate 2 has a cavity portion 2a in its
bottom surface, in which the semiconductor elements 1a, 1b, and 1c
and the passive components are provided, and the electrodes 4 for
connecting to the outside are formed on the ceramic multilayer
substrate 2 at portions peripheral to the cavity portion 2a. The
composite resin material layer 10 is formed in the cavity portion
2a, and the semiconductor elements 1a, 1b, and 1c and the passive
components are buried in the composite resin material layer 10.
[0071] It should be noted that a metal wire can be employed to
connect the semiconductor elements to the electrode pattern of the
ceramic multilayer substrate 2. Also, the device of this embodiment
can be structured without the heat release electrode 14 and the
interlayer connector via holes 21. By adopting the cavity portion
2a as the portion in which the semiconductor elements and the
passive components are provided, the composite resin material layer
10 is formed easily.
[0072] The invention may be embodied in other forms without
departing from the spirit or essential characteristics thereof. The
embodiments disclosed in this application are to be considered in
all respects as illustrative and not limiting. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
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