U.S. patent application number 10/062535 was filed with the patent office on 2003-02-13 for semiconductor device and manufacturing method thereof.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Fujimoto, Hiroaki, Kaneko, Hideyuki, Matsumura, Kazuhiko, Nagao, Koichi, Nakaoka, Yukiko.
Application Number | 20030032216 10/062535 |
Document ID | / |
Family ID | 19071395 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030032216 |
Kind Code |
A1 |
Nakaoka, Yukiko ; et
al. |
February 13, 2003 |
Semiconductor device and manufacturing method thereof
Abstract
A semiconductor device includes a first semiconductor chip
provided with a first electrode on a first main surface and a
second semiconductor chip provided with a second electrode on a
second main surface. The first and the second semiconductor chips
are integrated so that the first and second main surfaces are
opposed to one another and the first and second electrodes are
electrically connected. The second semiconductor chip is polished
from the opposite side of the second main surface so that the
second semiconductor chip has a thickness smaller than the
thickness of the first semiconductor chip.
Inventors: |
Nakaoka, Yukiko; (Ikoma-shi,
JP) ; Matsumura, Kazuhiko; (Kitakatsuragi-gun,
JP) ; Kaneko, Hideyuki; (Itami-shi, JP) ;
Nagao, Koichi; (Kyoto-shi, JP) ; Fujimoto,
Hiroaki; (Hirakata-shi, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
8180 GREENSBORO DRIVE
SUITE 800
MCLEAN
VA
22102
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Osaka
JP
|
Family ID: |
19071395 |
Appl. No.: |
10/062535 |
Filed: |
February 5, 2002 |
Current U.S.
Class: |
438/106 ;
257/E21.503; 257/E21.511; 257/E21.705; 257/E23.052; 257/E25.013;
257/E29.022 |
Current CPC
Class: |
H01L 2224/48091
20130101; H01L 2224/13111 20130101; H01L 2924/01029 20130101; H01L
2224/16148 20130101; H01L 2224/45124 20130101; H01L 2224/73204
20130101; H01L 2224/81203 20130101; H01L 2224/97 20130101; H01L
21/563 20130101; H01L 2224/73203 20130101; H01L 2924/01047
20130101; H01L 2924/01013 20130101; H01L 24/32 20130101; H01L
2924/01006 20130101; H01L 2924/0105 20130101; H01L 2224/48247
20130101; H01L 2924/181 20130101; H01L 2224/29109 20130101; H01L
2224/81801 20130101; H01L 2924/01005 20130101; H01L 23/49575
20130101; H01L 2224/29164 20130101; H01L 2224/73265 20130101; H01L
2224/0508 20130101; H01L 2924/01028 20130101; H01L 24/48 20130101;
H01L 2224/05573 20130101; H01L 2225/06513 20130101; H01L 2924/01046
20130101; H01L 24/29 20130101; H01L 2924/01033 20130101; H01L 24/45
20130101; H01L 2224/05023 20130101; H01L 2224/81191 20130101; H01L
2924/01082 20130101; H01L 24/73 20130101; H01L 29/0657 20130101;
H01L 24/05 20130101; H01L 2924/01079 20130101; H01L 2224/16145
20130101; H01L 2224/83192 20130101; H01L 2224/45144 20130101; H01L
2924/01025 20130101; H01L 2924/20752 20130101; H01L 24/81 20130101;
H01L 25/0657 20130101; H01L 2224/05001 20130101; H01L 2924/18161
20130101; H01L 24/94 20130101; H01L 24/97 20130101; H01L 25/50
20130101; H01L 2224/05568 20130101; H01L 2224/29111 20130101; H01L
2224/29139 20130101; H01L 2224/95 20130101; H01L 2224/32245
20130101; H01L 2224/45015 20130101; H01L 2225/0651 20130101; H01L
2224/32145 20130101; H01L 2924/0132 20130101; H01L 2225/06582
20130101; H01L 2924/0103 20130101; H01L 2224/94 20130101; H01L
2224/45124 20130101; H01L 2924/00014 20130101; H01L 2224/45144
20130101; H01L 2924/00014 20130101; H01L 2224/48091 20130101; H01L
2924/00014 20130101; H01L 2224/95 20130101; H01L 2224/81 20130101;
H01L 2224/45015 20130101; H01L 2924/20752 20130101; H01L 2224/83192
20130101; H01L 2224/32245 20130101; H01L 2924/0132 20130101; H01L
2224/83192 20130101; H01L 2224/32245 20130101; H01L 2924/01029
20130101; H01L 2924/0105 20130101; H01L 2224/73265 20130101; H01L
2924/0132 20130101; H01L 2924/01029 20130101; H01L 2224/32145
20130101; H01L 2224/48247 20130101; H01L 2924/0105 20130101; H01L
2924/00 20130101; H01L 2224/73265 20130101; H01L 2924/0132
20130101; H01L 2224/32145 20130101; H01L 2924/0103 20130101; H01L
2224/48247 20130101; H01L 2924/0105 20130101; H01L 2924/00
20130101; H01L 2924/0132 20130101; H01L 2924/01047 20130101; H01L
2924/0103 20130101; H01L 2924/0105 20130101; H01L 2924/0132
20130101; H01L 2924/01049 20130101; H01L 2924/01047 20130101; H01L
2924/0105 20130101; H01L 2924/0132 20130101; H01L 2924/0105
20130101; H01L 2924/01049 20130101; H01L 2924/0105 20130101; H01L
2924/01082 20130101; H01L 2224/29139 20130101; H01L 2924/0132
20130101; H01L 2924/0105 20130101; H01L 2924/00014 20130101; H01L
2924/01082 20130101; H01L 2224/29139 20130101; H01L 2224/29164
20130101; H01L 2924/00014 20130101; H01L 2224/29164 20130101; H01L
2224/94 20130101; H01L 2924/00014 20130101; H01L 2224/81 20130101;
H01L 2224/97 20130101; H01L 2224/94 20130101; H01L 2224/81
20130101; H01L 2224/97 20130101; H01L 2224/81 20130101; H01L
2224/83 20130101; H01L 2224/94 20130101; H01L 2224/97 20130101;
H01L 2224/83 20130101; H01L 2224/94 20130101; H01L 2224/73204
20130101; H01L 2224/83 20130101; H01L 2224/16145 20130101; H01L
2224/32145 20130101; H01L 2924/00012 20130101; H01L 2224/73204
20130101; H01L 2224/73265 20130101; H01L 2224/32245 20130101; H01L
2224/16145 20130101; H01L 2224/32145 20130101; H01L 2224/48247
20130101; H01L 2924/00012 20130101; H01L 2924/3512 20130101; H01L
2224/73265 20130101; H01L 2224/32245 20130101; H01L 2924/00
20130101; H01L 2224/48247 20130101; H01L 2924/00012 20130101; H01L
2924/3512 20130101; H01L 2224/97 20130101; H01L 2924/00 20130101;
H01L 2224/73265 20130101; H01L 2224/32245 20130101; H01L 2224/48247
20130101; H01L 2924/00 20130101; H01L 2224/97 20130101; H01L
2224/73265 20130101; H01L 2224/32245 20130101; H01L 2224/32145
20130101; H01L 2224/48247 20130101; H01L 2924/00 20130101; H01L
2224/97 20130101; H01L 2924/181 20130101; H01L 2224/73265 20130101;
H01L 2924/00012 20130101; H01L 2224/32145 20130101; H01L 2224/48247
20130101; H01L 2924/00 20130101; H01L 2924/181 20130101; H01L
2924/00012 20130101 |
Class at
Publication: |
438/106 |
International
Class: |
H01L 021/48 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2001 |
JP |
2001-240844 |
Claims
What is claimed is:
1. A semiconductor device, comprising a first semiconductor chip
provided with a first electrode on a first main surface, and a
second semiconductor chip provided with a second electrode on a
second main surface, said first and second semiconductor chips
being integrated with one another so that said first and second
main surfaces are opposed to one another and said first and second
electrodes are electrically connected, said second semiconductor
chip having a thickness smaller than a thickness of said first
semiconductor chip.
2. The semiconductor device according to claim 1, wherein said
second semiconductor chip has the thickness equal to or less than
1/2 of the thickness of said first semiconductor chip.
3. The semiconductor device according to claim 1, further
comprising a resin layer between said first and second main
surfaces.
4. The semiconductor device according to claim 1, further
comprising a resin package to encapsulate said first and second
semiconductor chips.
5. The semiconductor device according to claim 1, wherein an area
of said first main surface is larger than an area of said second
main surface, a third electrode is provided outside a region of
said first main surface opposed to said second main surface, a
surface opposite to said first main surface of said first
semiconductor chip is adhered to a die pad, a lead is provided
adjacent to said die pad, said lead and said third electrode being
connected through a bonding wire, and said first semiconductor
chip, said second semiconductor chip and the bonding wire are
encapsulated in a resin package.
6. The semiconductor device according to claim 5, wherein a
distance from said first main surface to a surface opposite to said
second main surface of said second semiconductor chip is smaller
than a distance from said first main surface to the highest
position of said bonding wire on said first main surface.
7. A method of manufacturing a semiconductor device comprising a
first semiconductor chip provided with a first electrode on a first
main surface and a second semiconductor chip provided with a second
electrode on a second main surface, said method comprising: a first
step of integrating said first and second semiconductor chips by
arranging said first and said second main surfaces to be opposed to
one another and electrically connecting said first and second
electrodes; and a second step of polishing said second
semiconductor chip integrated with said first semiconductor chip
from an opposite side of said second main surface, so that a
thickness of said second semiconductor chip is made smaller than a
thickness of said first semiconductor chip.
8. The method of manufacturing a semiconductor device according to
claim 7, wherein said first step comprises the step of forming a
resin layer between said first and second main surfaces.
9. The method of manufacturing a semiconductor device according to
claim 7, wherein said second step comprises the step of reducing
the thickness of said second semiconductor chip to at most 1/2 of
the thickness of said first semiconductor chip.
10. The method of manufacturing a semiconductor device according to
claim 7, wherein an area of said first main surface is larger than
an area of said second main surface, a third electrode is provided
outside a region of said first main surface opposed to said second
main surface, and said second step precedes the steps of adhering a
surface opposite to said first main surface of said first
semiconductor chip to a die pad; arranging a lead adjacent to said
die pad and electrically connecting said lead and said third
electrode through a bonding wire; and forming a resin package to
encapsulate said first semiconductor chip, said second
semiconductor chip and the bonding wire.
11. The method of manufacturing a semiconductor device according to
claim 10, wherein said second step comprises the step of allowing a
distance from said first main surface to a surface opposite to said
second main surface of said second semiconductor chip to be smaller
than a distance from said first main surface to the highest
position of said bonding wire on said first main surface.
12. A method of manufacturing a semiconductor device comprising a
first semiconductor chip provided with a first electrode on a first
main surface and a second semiconductor chip provided with a second
electrode on a second main surface, said method comprising: a first
step of integrating a semiconductor wafer to be a plurality of said
first semiconductor chips and a plurality of discrete said second
semiconductor chips by arranging said first main surface of each
said first semiconductor chip in said semiconductor wafer to be
opposed to said second main surface of each said second
semiconductor chip and electrically connecting said first electrode
on each said first semiconductor chip in said semiconductor wafer
and said second electrode on each said second semiconductor chip; a
second step of polishing said second semiconductor chip integrated
with said semiconductor wafer from an opposite side of said second
main surface so that a thickness of each said second semiconductor
chip is made smaller than a thickness of said semiconductor wafer;
and a third step of separating said semiconductor wafer integrated
with said second semiconductor chips into a plurality of discrete
said first semiconductor chips, thereby forming a plurality of
chip-layered bodies each including a discrete said first
semiconductor chip and a discrete said second semiconductor chip
integrated with one another.
13. The method of manufacturing a semiconductor device according to
claim 12, wherein said first step comprises the step of forming a
resin layer between said first main surface of each said first
semiconductor chip in said semiconductor wafer and said second main
surface of each said second semiconductor chip.
14. The method of manufacturing a semiconductor device according to
claim 12, wherein said second step comprises the step of reducing
the thickness of each said second semiconductor chip to at most 1/2
of the thickness of said semiconductor wafer.
15. The method of manufacturing a semiconductor device according to
claim 12, wherein an area of said first main surface is larger than
an area of said second main surface, a third electrode is provided
outside a region of said first main surface opposed to said second
main surface, and after said third step, said chip-layered bodies
are each subjected to the steps of adhering a surface of said first
semiconductor chip opposite to said first main surface to a die
pad; providing a lead adjacent to said die pad and electrically
connecting said lead and said third electrode through a bonding
wire; and forming a resin package to encapsulate said first
semiconductor chip, said second semiconductor chip and the bonding
wire.
16. The method of manufacturing a semiconductor device according to
claim 15, wherein said second step comprises the step of arranging
the distance from said first main surface of each said first
semiconductor chip in said semiconductor wafer to a surface of each
said second semiconductor chip opposite to said second main surface
to be smaller than the distance from said first main surface of
each said first semiconductor chip in said semiconductor wafer to
the highest position of said bonding wire on said first main
surface.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to semiconductor devices
having multiple semiconductor chips layered on one another and
manufacturing methods thereof. The invention more particularly
relates to a semiconductor device including two semiconductor chips
having their circuit forming surfaces opposed to one another, and
electrodes formed on the circuit forming surfaces being
electrically connected with one another, and a manufacturing method
thereof.
[0002] In recent years, with the advent of smaller size electronic
devices capable of high speed processing, a three-dimensional
structure including two or more kinds of semiconductor chips
layered on one another has come to be widely researched and
developed.
[0003] Such a conventional three-dimensional semiconductor device
will be now described.
[0004] FIG. 18 is a sectional view of the conventional
semiconductor device.
[0005] As shown in FIG. 18, the conventional semiconductor device
includes a first semiconductor chip 1 and a second semiconductor
chip 4. The first semiconductor chip 1 has first electrodes 2 and
bonding pads 3 on a first main surface. The second semiconductor
chip 4 is provided with second electrodes 5 on a second main
surface and has a smaller area than the first semiconductor chip 1.
Herein, the first and second semiconductor chips 1 and 4 are
integrated so that their main surfaces (i.e., the circuit forming
surfaces) are opposed to one another and the first and second
electrodes 2 and 5 are electrically connected with one another.
Stated differently, while the first and second electrodes 2 and 5
are registered, the second semiconductor chip 4 is placed facedown
on the first semiconductor chip 1. More specifically, the first and
second electrodes 2 and 5 are connected through a metal bump 7,
while the part of the second electrode 5 in contact with the metal
bump 7 is provided with a barrier metal layer 6. The bonding pads 3
are provided outside the region of the first main surface of the
first semiconductor chip 1 opposed to the second main surface of
the second semiconductor chip 4. There is a resin layer 8 filled
between the first main surface of the first semiconductor chip 1
and the second main surface of the second semiconductor chip 4.
More specifically, the first and second semiconductor chips 1 and 4
are adhered by the resin layer 8 into an integrated form.
[0006] The surface of the first semiconductor chip 1 opposite to
the first main surface is secured to a die pad portion 9a by
conductive paste 10 containing palladium (Pd), silver (Ag) or the
like. The bonding pad 3, and a lead portion 9b provided adjacent to
the die pad portion 9a are electrically connected with one another
through a thin metal bonding wire 11. Note that the die pad portion
9a and the lead portion 9b are cut from a single lead frame 9. The
first and second semiconductor chips 1 and 4, the die pad portion
9a, the lead portions 9b and the bonding wires 11 are encapsulated
in a resin package 12.
[0007] A method of manufacturing the conventional semiconductor
device will be now described.
[0008] FIGS. 19A, 19B, 20A and 20B are sectional views showing
steps in the method of manufacturing the conventional semiconductor
device.
[0009] As shown in FIG. 19A, the first and second semiconductor
chips 1 and 4 are registered. More specifically, a plurality of
first electrodes 2 and a plurality of bonding pads 3 are provided
on a first main surface of the first semiconductor chip 1. The chip
1 is then placed on a packaging jig (not shown) and a resin 8A is
applied on the first main surface of the semiconductor chip 1. The
second semiconductor chip 4 having a plurality of second electrodes
5 on a second main surface is prepared over the first semiconductor
chip 1 so that their main surfaces, i.e., their circuit forming
surfaces are opposed to one another. Then, after a plurality of
metal bumps 7 are formed on the second electrodes 5, the first and
second electrodes 2 and 5 are registered. Note that there is a
barrier metal layer 6 provided on the part of the second electrodes
5 in contact with the metal bumps 7.
[0010] Then, as shown in FIG. 19B, the first and second
semiconductor chips 1 and 4 are joined with one another. More
specifically, the second semiconductor chip 4 is heated and pressed
using a metal tool 13 from the surface opposite to the second main
surface. As a result, the first electrodes 2 on the first
semiconductor chip 1 and the second electrodes 5 on the second
semiconductor chip 4 are joined with one another through the metal
bumps 7 formed on the second electrodes 5 (more precisely on the
barrier metal layers 6) on the second semiconductor chip 4. Then,
the resin 8A filled between the joined first and second
semiconductor chips 1 and 4 is irradiated with ultraviolet rays or
heated for curing and a resin layer 8 results.
[0011] Then, as shown in FIG. 20A, the joined first and second
semiconductor chips 1 and 4 in an integrated form (hereinafter
referred to as a "chip-layered body") is subjected to wire-bonding.
More specifically, a lead frame 9 having a die pad portion 9a and
lead portions 9b is prepared. Then, the surface opposite to the
first main surface of the first semiconductor chip 1 is secured
onto the die pad portion 9a using conductive paste 10 containing
Pd, Ag or the like. The bonding pads 3 on the first semiconductor
chip 1 and the lead portions 9b are then electrically connected
through thin metal bonding wires 11. Thus, the electrical
connection for the semiconductor device is completed.
[0012] As shown in FIG. 20B, the chip-layered body after the
wire-bonding step is encapsulated in a resin. More specifically,
the first and second semiconductor chips 1 and 4, the die pad
portion 9a, the lead portions 9b and the bonding wires 11 are
encapsulated in a resin package 12. Note however that the bottom
surface of the die pad portion 9a and the bottom and outer side
surfaces of the lead portions 9b (the side surfaces opposite to the
side facing the die pad portion 9a) are exposed out of the resin
package 12. Thus, the bottom and outer side surfaces of the lead
portions 9b serve as external terminals.
[0013] However, the conventional semiconductor device and the
manufacturing method thereof described above suffer from the
following disadvantages. The thickness of the semiconductor device
having multiple layers of semiconductor chips increases in
proportion to the number of the semiconductor chips used. For
example, in the conventional semiconductor device shown in FIG. 18,
the thickness of the first and second semiconductor chips 1 and 4
is each about in the range from 200 to 300 .mu.m even after the
back surface (the surface opposite to the circuit forming surface
(main surface)) is polished. The metal bumps 7 used to join the
first and second semiconductor chips 1 and 4 are about as thick as
several tens .mu.m after the joining. In addition, if the
chip-layered body including the first and second semiconductor
chips 1 and 4 is die-bonded to the die pad portion 9a as thick as
several hundreds .mu.m and the die-bonded chip-layered body as a
whole is encapsulated in the resin package 12, the completed
semiconductor device has a thickness about as large as 1 mm. Such a
thickness is about the same as the thickness of the thin type
packages widely used in recent years, which suggests how hard it
could be to reduce the size of semiconductor devices having such a
chip-layered body.
[0014] Meanwhile, semiconductor chips with large thickness in a
semiconductor device could impede thermal radiation from the
semiconductor chips, and therefore the heat radiation property of
the semiconductor device as a whole could be lowered.
SUMMARY OF THE INVENTION
[0015] In view of the foregoing, it is an object of the present
invention to reduce the thickness of a chip-layered body forming a
semiconductor device, and allow the semiconductor device to have a
reduced size and improved heat radiation property.
[0016] In order to achieve the object, the semiconductor device
according to the present invention includes a first semiconductor
chip provided with a first electrode on a first main surface, and a
second semiconductor chip provided with a second electrode on a
second main surface. The first and second semiconductor chips are
integrated with one another so that the first and second main
surfaces are opposed to one another and the first and second
electrodes are electrically connected. The second semiconductor
chip has a thickness smaller than a thickness of the first
semiconductor chip.
[0017] In the semiconductor device according to the present
invention, since the second semiconductor chip integrated facedown
with the first semiconductor chip has a thickness smaller than that
of the first semiconductor chip, a chip-layered body including the
first and second semiconductor chips may have a reduced thickness.
The package structure including the chip-layered body encapsulated
in a resin can thus be thinner, which allows the semiconductor
device to have a reduced size and improved heat radiation
property.
[0018] In the semiconductor device according to the present
invention, the second semiconductor chip preferably has the
thickness equal to or smaller than 1/2 of the thickness of the
first semiconductor chip.
[0019] In this way, the package structure for the chip-layered body
can be made thinner, so that the semiconductor device can have a
more reduced size and higher heat radiation property.
[0020] In the semiconductor device according to the present
invention, a resin layer is preferably provided between the first
and second main surfaces. Alternatively, a resin package to
encapsulate the first and second semiconductor chips is preferably
provided.
[0021] In this way, the chip-layered body including the first and
second semiconductor chips can have improved reliability.
[0022] In the semiconductor device according to the present
invention, an area of the first main surface is larger than an area
of the second main surface, and a third electrode is provided
outside a region of the first main surface opposed to the second
main surface. A surface opposite to the first main surface of the
first semiconductor chip is adhered to a die pad, a lead is
provided adjacent to the die pad, and the lead and the third
electrode are connected through a bonding wire. The first
semiconductor chip, the second semiconductor chip and the bonding
wire may be encapsulated in a resin package. In this case, a
distance from the first main surface to a surface opposite to the
second main surface of the second semiconductor chip is preferably
smaller than a distance from the first main surface to the highest
position of the bonding wire on the first main surface. In this
way, a semiconductor device including a chip-layered body of the
first and second semiconductor chips placed on a lead frame can
surely have a reduced size and improved heat radiation
property.
[0023] A semiconductor device manufactured by a first manufacturing
method according to the present invention includes a first
semiconductor chip provided with a first electrode on a first main
surface and a second semiconductor chip provided with a second
electrode on a second main surface. The method includes a first
step of integrating the first and second semiconductor chips by
arranging the first and second main surfaces to be opposed to one
another and electrically connecting the first and second
electrodes, and a second step of polishing the second semiconductor
chip integrated with the first semiconductor chip from the opposite
side of the second main surface, so that the thickness of the
second semiconductor chip is made smaller than the thickness of the
first semiconductor chip.
[0024] According to the first method, after the first and second
semiconductor chips are integrated to be opposed to one another,
the second semiconductor chip is polished from the opposite side of
the main surface (circuit forming surface), so that the second
semiconductor chip has a thickness smaller than the thickness of
the first semiconductor chip. Therefore, the thickness of the
chip-layered body including the first and second semiconductor
chips can be reduced, so that the package structure including the
chip-layered body encapsulated in a resin can have a reduced
thickness, which permits the semiconductor device to have a reduced
size and improved heat radiation property.
[0025] By the first method, the first step preferably includes the
step of forming a resin layer between the first and second main
surfaces.
[0026] In this way, the chip-layered body including the first and
second semiconductor chips may have improved reliability.
[0027] By the first method, the second step preferably includes the
step of reducing the thickness of the second semiconductor chip to
at most 1/2 of the thickness of the first semiconductor chip.
[0028] In this way, the package structure including the
chip-layered body can have a more reduced thickness, so that the
semiconductor device can have a more reduced size and higher heat
radiation property.
[0029] By the first method, an area of the first main surface is
larger than an area of the second main surface, a third electrode
is provided outside a region of the first main surface opposed to
the second main surface. The second step may precede the steps of
adhering a surface of the first semiconductor chip opposite to the
first main surface to a die pad, arranging a lead adjacent to the
die pad and electrically connecting the lead and the third
electrode through a bonding wire, and forming a resin package to
encapsulate the first semiconductor chip, the second semiconductor
chip and the bonding wire. In this case, the second step preferably
includes the step of allowing a distance from the first main
surface to a surface of the second semiconductor chip opposite to
the second main surface to be smaller than a distance from the
first main surface to the highest position of the bonding wire on
the first main surface. In this way, the semiconductor device
provided with the chip-layered body including the first and second
semiconductor chips placed on a lead frame can surely have a
reduced size and improved heat radiation property.
[0030] A semiconductor device manufactured by a second
manufacturing method according to the present invention includes a
first semiconductor chip provided with a first electrode on a first
main surface and a second semiconductor chip provided with a second
electrode on a second main surface. The method includes a first
step of integrating a semiconductor wafer to be a plurality of the
first semiconductor chips and a plurality of discrete second
semiconductor chips by arranging the first main surface of each
first semiconductor chip in the semiconductor wafer to be opposed
to the second main surface of each second semiconductor chip and
electrically connecting the first electrode on each first
semiconductor chip in the semiconductor wafer and the second
electrode on each second semiconductor chip, a second step of
polishing the second semiconductor chip integrated with the
semiconductor wafer from an opposite side of the second main
surface so that a thickness of each second semiconductor chip is
smaller than a thickness of the semiconductor wafer, and a third
step of separating the semiconductor wafer integrated with the
second semiconductor chips into a plurality of discrete first
semiconductor chips, thereby forming a plurality of chip-layered
bodies each including a discrete first semiconductor chips and a
discrete the second semiconductor chips integrated with one
another.
[0031] By the second method, in addition to the effects brought
about by the first method, the following effect results. More
specifically, a plurality of chip-layered bodies, in other words a
plurality of semiconductor devices having a reduced size and
improved heat radiation property can readily be manufactured simply
by separating a semiconductor wafer into a plurality of discrete
first semiconductor chips.
[0032] By the second method, the first step preferably includes the
step of forming a resin layer between the first main surface of
each first semiconductor chip in the semiconductor wafer and the
second main surface of each second semiconductor chip.
[0033] In this way, the chip-layered body including the first and
second semiconductor chips can have improved reliability.
[0034] By the second method, the second step preferably includes
the step of reducing the thickness of each second semiconductor
chip to at most 1/2 of the semiconductor wafer.
[0035] In this way, the package structure including the
chip-layered body can have a more reduced thickness, so that the
semiconductor device can have a more reduced size and improved heat
radiation property.
[0036] By the second method, an area of the first main surface is
larger than an area of the second main surface. A third electrode
is provided outside a region of the first main surface opposed to
the second main surface. After the third step, the chip-layered
bodies may each be subjected to the steps of adhering a surface of
the first semiconductor chip opposite to the first main surface to
a die pad, providing a lead adjacent to the die pad and
electrically connecting the lead and the third electrode through a
bonding wire, and forming a resin package to encapsulate the first
semiconductor chip, the second semiconductor chip and the bonding
wire. In this case, the second step preferably includes the step of
arranging a distance from the first main surface of each first
semiconductor chip in the semiconductor wafer to a surface of each
second semiconductor chip opposite to the second main surface to be
smaller than a distance from the first main surface of each first
semiconductor chip in the semiconductor wafer to the highest
position of the bonding wire on the first main surface. In this
way, the semiconductor device including the chip-layered body of
the first and second semiconductor chips placed on a lead frame can
surely have a reduced size and improved heat radiation
property.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a sectional view of a semiconductor device
according to a first embodiment of the present invention;
[0038] FIG. 2 is a sectional view of a semiconductor device
according to a modification of the first embodiment;
[0039] FIG. 3 is a sectional view of a semiconductor device
according to a second embodiment of the present invention;
[0040] FIGS. 4A and 4B are sectional views showing steps in a
method of manufacturing a semiconductor device according to a third
embodiment of the present invention;
[0041] FIGS. 5A and 5B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
third embodiment of the present invention;
[0042] FIGS. 6A and 6B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
third embodiment of the present invention;
[0043] FIG. 7 is a sectional view showing one step in the method of
manufacturing a semiconductor device according to the third
embodiment;
[0044] FIGS. 8A and 8B are sectional views showing steps in a
method of manufacturing a semiconductor device according to a
modification of the third embodiment of the present invention;
[0045] FIGS. 9A, and 9B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
modification of the third embodiment of the present invention;
[0046] FIG. 10 is a sectional view showing one step in the method
of manufacturing a semiconductor device according to the
modification of the third embodiment;
[0047] FIGS. 11A and 11B are sectional views showing steps in a
method of manufacturing a semiconductor device according to a
fourth embodiment of the present invention;
[0048] FIGS. 12A and 12B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
fourth embodiment of the present invention;
[0049] FIGS. 13A, and 13B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
fourth embodiment of the present invention;
[0050] FIG. 14 is a sectional view showing one step in the method
of manufacturing a semiconductor device according to the fourth
embodiment;
[0051] FIGS. 15A and 15B are sectional views showing steps in a
method of manufacturing a semiconductor device according to a
modification of the fourth embodiment of the present invention;
[0052] FIGS. 16A, and 16B are sectional views showing steps in the
method of manufacturing a semiconductor device according to the
modification of the fourth embodiment of the present invention;
[0053] FIG. 17 is a sectional view showing one step in the method
of manufacturing a semiconductor device according to the
modification of the fourth embodiment;
[0054] FIG. 18 is a sectional view of a conventional semiconductor
device;
[0055] FIGS. 19A and 19B are sectional views showing steps in a
method of manufacturing the conventional semiconductor device;
and
[0056] FIGS. 20A, and 20B are sectional views showing steps in the
method of manufacturing the conventional semiconductor device.
DETAILED DESCRIPTION OF THE INVENTION
[0057] [First Embodiment]
[0058] A semiconductor device according to a first embodiment of
the present invention will be now described in conjunction with the
accompanying drawings.
[0059] FIG. 1 is a sectional view of the semiconductor device
according to the first embodiment.
[0060] As shown in FIG. 1, the semiconductor device according to
the first embodiment includes first and second semiconductor chips
101 and 104. The first semiconductor chip 101 is provided with
first electrodes 102 and bonding pads 103 on a first main surface.
The second semiconductor chip 104 is provided with second
electrodes 105 on a second main surface and has a smaller area than
the first semiconductor chip 101. Herein, the first and second
semiconductor chips 101 and 104 are integrated so that their main
surfaces (i.e., their circuit forming surfaces) are opposed to one
another and the first and second electrodes 102 and 105 are
electrically connected with one another. Stated differently, the
first and second electrodes 102 and 105 are registered as the
second semiconductor chip 104 is joined facedown on the first
semiconductor chip 101. More specifically, the first and second
electrodes 102 and 105 are connected with one another through metal
bumps 107. The part of the second electrode 105 in contact with the
metal bump 107 is provided with a barrier metal layer 106. Note
that the bonding pad 103 (which corresponds to the third electrode
in the section of "What is claimed is:") is provided outside the
region of the first main surface of the first semiconductor chip
101 opposed to the second main surface of the second semiconductor
chip 104. There is a resin layer 108 filled between the first main
surface of the first semiconductor chip 101 and the second main
surface of the second semiconductor chip 104. More specifically,
the first semiconductor chip 101 and the second semiconductor chip
104 are adhered by the resin layer 108 into an integrated form.
[0061] The surface of the first semiconductor chip 101 opposite to
the first main surface is adhered to a die pad portion 109a by
conductive paste 110 containing Pd, Ag or the like. Lead portions
109b provided adjacent to the die pad portion 109a are used to
exchange electrical signals between elements such as transistors in
the semiconductor chips and external devices. The lead portions
109b and the bonding pads 103 on the first semiconductor chip 101
are electrically connected through thin metal bonding wires 111.
Note that the die pad portion 109a and the lead portion 109b are
cut from a single lead frame 109. The first semiconductor chip 101,
the second semiconductor chip 104, the die pad 109a, the lead
portions 109b, and the bonding wires 111 are encapsulated in a
resin package 112.
[0062] Herein, according to the first embodiment, as shown in FIG.
1, the second semiconductor chip 104 has a thickness T.sub.2
smaller than the thickness of T.sub.1 of the first semiconductor
chip 101 (T.sub.2<T.sub.1).
[0063] According to the first embodiment, the second semiconductor
chip 104 integrated facedown with the first semiconductor chip 101
is thinner than the first semiconductor chip 101. Therefore, the
chip-layered body including the first and second semiconductor
chips 101 and 104 may have a reduced thickness. This allows the
package structure including the chip-layered body encapsulated in
the resin package 112 to be thinner, so that the semiconductor
device can have a reduced size and improved heat radiation
property.
[0064] Also according to the first embodiment, the resin layer 108
is provided between the first main surface of the first
semiconductor chip 101 and the second main surface of the second
semiconductor chip 104, and these semiconductor chips 101 and 104
are encapsulated in the resin package 112. Therefore, the
chip-layered body including the first and second semiconductor
chips 101 and 104 can have improved reliability.
[0065] [Modification of First Embodiment]
[0066] A semiconductor device according to a modification of the
first embodiment of the present invention will be now described in
conjunction with the accompanying drawings.
[0067] FIG. 2 is a sectional view of the semiconductor device
according to the modification of the first embodiment. Note that in
the following description of the modification, the same elements as
those in the first embodiment shown in FIG. 1 will be denoted by
the same reference characters and will not be detailed.
[0068] As shown in FIG. 2, according to the modification of the
first embodiment, the second semiconductor chip 104 has a thickness
T.sub.2 equal to or smaller than 1/2 of the thickness T.sub.1 of
the first semiconductor chip 101 (T.sub.2.times.2 T.sub.1).
[0069] According to the modification of the first embodiment, the
package structure including the layered body of the first and
second semiconductor chips 101 and 104 encapsulated in the resin
package 112 can be made thinner than the first embodiment, and
therefore the semiconductor device can have a more reduced size and
more improved heat radiation property.
[0070] According to the modification of the first embodiment, the
semiconductor chip 101 has, for example, a thickness T.sub.1 about
in the range from 200 to 300 .mu.m, while the second semiconductor
chip 104 has, for example, a thickness T.sub.2 about in the range
from 50 to 100 .mu.m.
[0071] [Second Embodiment]
[0072] A semiconductor device according to a second embodiment of
the present invention will be now described in conjunction with the
accompanying drawings.
[0073] FIG. 3 is a sectional view of the semiconductor device
according to the second embodiment. In the following description of
the second embodiment, the same elements as those in the first
embodiment shown in FIG. 1 will be denoted by the same reference
characters and will not be detailed.
[0074] As shown in FIG. 3, according to the second embodiment, the
distance T.sub.chip from the first main surface of the first
semiconductor chip 101 to the surface of the second semiconductor
chip 104 opposite to the second main surface is smaller than the
distance T.sub.wb from the first main surface of the first
semiconductor chip 101 to the highest position of the bonding wire
111 on the first main surface (i.e., the peak of the loop of the
bonding wire 111) (T.sub.chip<T.sub.wb).
[0075] According to the second embodiment, in addition to the
effects brought about by the first embodiment, the following effect
results. The semiconductor device including the layered body of the
first semiconductor chip 101 and the second semiconductor chip 104
placed on the lead frame 109 can surely have a reduced size and
improved heat radiation property.
[0076] [Third Embodiment]
[0077] A method of manufacturing a semiconductor device according
to a third embodiment of the present invention will be now
described in conjunction with the accompanying drawings.
[0078] FIGS. 4A, 4B, 5A, 5B, 6A, 6B, and 7 are sectional views
showing steps in the method of manufacturing the semiconductor
device according to the third embodiment.
[0079] As shown in FIG. 4A, a semiconductor wafer 201 having a
plurality of chip regions to be first semiconductor chips 201a (see
FIG. 6A) and a second semiconductor chip 204 are registered. The
second semiconductor chip 204 has a smaller area than that of a
chip region in the semiconductor wafer 201 (i.e., the first
semiconductor chip 201a). Note that in FIGS. 4A, 4B, 5A, 5B, and
6A, the boundaries between the chip regions are denoted by broken
lines.
[0080] Here, an element such as a transistor or interconnection is
formed in each chip region in the semiconductor wafer 201. On the
surface of each chip region in the semiconductor wafer 201 (i.e.,
on the first main surface of the semiconductor chip 201a), there
are a plurality of first electrodes 202 (for connection with bumps)
and a plurality of bonding pads 203 (for connection with thin metal
wires). The first electrodes 202 and bonding pads 203 are formed,
for example, of aluminum (Al). The bonding pad 203 corresponds to
the "third electrode" in the section of "What is claimed is."
Meanwhile, a plurality of second electrodes 205 of Al, for example,
are formed on the second main surface of the semiconductor chip
204. A barrier metal layer 206 of a titanium, copper or nickel
metal thin film, for example, is formed on each of the second
electrodes 205.
[0081] More specifically, as shown in FIG. 4A, a metal bump 207 of
an alloy of tin (Sn) and lead (Pb) (Sn--Pb alloy), for example, is
formed on each of the second electrodes 205 on the second
semiconductor chip 204 through the barrier metal layer 206. The
metal bump 207 has a diameter about in the range from 3 to 100
.mu.m and a height about in the range from 3 to 50 .mu.m. The
semiconductor wafer 201 is placed on the packaging jig (not shown)
and a resin 208A such as an epoxy resin is applied on the surface
of one chip region in the semiconductor wafer 201. Then, the second
semiconductor chip 204 is held by a tool 209 over the chip region
in the semiconductor wafer 201, so that the surface of the chip
region and the second main surface of the semiconductor chip 204
are opposed to each other. Then, as shown in FIG. 4B, the chip
region in the semiconductor wafer 201 and the second semiconductor
chip 204 are joined with each other. More specifically, the second
semiconductor chip 204 is lowered as it is held by the tool 209,
and the metal bumps 207 formed on the second electrodes 205 on the
second semiconductor chip 204 and the first electrodes 202 placed
in the chip region in the semiconductor wafer 201 are registered.
Here, the bonding pads 203 in the chip region in the semiconductor
wafer 201 are provided outside the region of the surface of the
chip region opposed to the second main surface of the second
semiconductor chip 204.
[0082] Then, the second semiconductor chip 204 is heated and
pressed from the surface opposite to the second main surface using
the tool 209. Thus, the registered first electrodes 202 and metal
bumps 207 on the second semiconductor chip 204 are joined by
physical or metallurgical effect (such as interdiffusion of atoms).
At the time, the resin 208A applied on the surface of the chip
region in the semiconductor wafer 201 enhances the adhesion between
the semiconductor wafer 201 and the second semiconductor chip 204.
Note that the pressing force (load) by the tool 209 should be about
in the range from 0.98 to 196 mN for each metal bump 207, and the
size of the load is set on the condition that the first electrodes
202 are not damaged. Alternatively, the load may be set on the
condition that the characteristics of elements such as transistors
or interconnections formed under the first electrodes 202 in the
semiconductor wafer 201 are unaffected.
[0083] Then, the resin 208A is cured to form a resin layer 208, so
that the second semiconductor chip 204 and the semiconductor wafer
201 are integrated. At the time, the resin 208A can be cured by
irradiation of ultraviolet rays if it is a photosetting resin. The
resin 208A can be cured by heating if it is a thermosetting resin.
If the resin 208A is to be cured by heating (i.e., if the resin is
a thermosetting resin), the resin 208A is heated using heating
instrument such as an oven after it is released from the pressing
by the tool 209. Alternatively, a heater installed in the tool 209
is used to directly heat the resin during the pressing step by the
tool 209. Although the temperature varies depending on the kind of
the resin, the resin 208A should be cured at a temperature about in
the range from 70 to 300.degree. C.
[0084] The steps shown in FIGS. 4A and 4B are repeated as many
times as the number of chip regions provided in the semiconductor
wafer 201. Then, as shown in FIG. 5A, a joined body 210 including a
plurality of second semiconductor chips 204 each provided in a chip
region in the semiconductor wafer 201 can be formed.
[0085] Then, as shown in FIG. 5B, the back surface of each of the
semiconductor chips 204 (the surface opposite to the second main
surface) in the joined body 210 is polished. More specifically, the
resin 208A is sufficiently cured to form the resin layer 208, and
then the joined body 210 is placed on a polishing machine 211 so
that the back surfaces of the second semiconductor chips 204 placed
in the chip regions in the semiconductor wafer 201 are opposed to
the upper surface (polishing surface) of the polishing machine 211.
A protection resin 212 is provided between the second semiconductor
chips 204 placed in the chip regions in the semiconductor wafer
201. After the polishing surface of the polishing machine 211 is
supplied with abrasive grains 213, the polishing machine 211 is
rotated as the joined body 210 is loaded with weight. In this
manner, the back surfaces of the second semiconductor chips 204 are
polished. At the time, in the joined body 210 removed from the
polishing machine 211, the thickness of the second semiconductor
chip 204 on the semiconductor wafer 201 decreases in inverse
proportion to the duration of the polishing time. Note that for the
abrasive grains 213, diamond grains having a grain size in the
range from #1200 to #2000 are preferably used, and the polishing
machine 211 is preferably rotated at about 5 to 50 rpm.
[0086] According to the third embodiment, the back surfaces of the
second semiconductor chips 204 can be polished so that the
thickness of the second semiconductor chips 204 is at least smaller
than the thickness of the semiconductor wafer 201 (i.e., the
thickness of the first semiconductor chips 201a). More
specifically, the polished second semiconductor chip 204 preferably
has a thickness about in the range from 50 to 100 .mu.m. Note that
the semiconductor wafer 201 has a thickness about in the range from
200 to 300 .mu.m, and the semiconductor chip 204 before polishing
is about as thick as the semiconductor wafer 201.
[0087] Then, as shown in FIG. 6A, the semiconductor wafer 201 is
subjected to dicing. More specifically, the chip regions in the
semiconductor wafer 201 in the joined body 210 are separated as a
plurality of discrete first semiconductor chips 201a by dicing.
Thus, a plurality of chip-layered bodies 214 each including one
first semiconductor chip 201a and one second semiconductor chip 204
joined with one another result. For the ease of illustration, only
a single chip-layered body 214 will be described.
[0088] As shown in FIG. 6B, the chip-layered body 214 is subjected
to die-bonding and wire-bonding. More specifically, a lead frame
215 having a die pad portion 215a and lead portions 215b is
prepared. The back surface of the first semiconductor chip 201a
forming the chip-layered body 214 (the surface opposite to the
first main surface) is secured on the die pad portion 215a using
conductive paste 216 containing Pd, Ag or the like. Then, the
bonding pad 203 on the first semiconductor chip 201a and the lead
portion 215b are electrically connected through a thin metal
bonding wire 217. Here, the thin metal wire has a diameter of about
25 .mu.m. Gold (Au), Al or the like can be used for the thin metal
wire.
[0089] As shown in FIG. 7, after the wire-bonding step, the
chip-layered body 214 is encapsulated in a resin. More
specifically, the first semiconductor chip 201a, the second
semiconductor chip 204, the die pad portion 215a and lead portions
215b of the lead frame 215, and the bonding wires 217 are
encapsulated in a resin package 218 of an epoxy-based resin, a
polyimide-based resin or the like. Note, however, that the bottom
surface of the die pad portion 215a and the bottom and outer side
surfaces of the lead portions 215b are exposed out of the resin
package 218. Thus, the bottom and outer side surfaces of the lead
portions 215b serve as external terminals.
[0090] As in the foregoing, according to the third embodiment, the
plurality of first semiconductor chips 201a in the semiconductor
wafer 201 and the plurality of discrete second semiconductor chips
204 are integrated to face to one another. Then, the second
semiconductor chips 204 are polished from the side opposite to
their main surfaces (circuit forming surfaces), so that the second
semiconductor chips 204 have a thickness smaller than the thickness
of the semiconductor wafer 201 or the first semiconductor chip
201a. Then, the semiconductor wafer 201 is separated into a
plurality of discrete first semiconductor chips 201a, so that a
plurality of chip-layered bodies 214 each including a discrete
first semiconductor chip 201a and a discrete second semiconductor
chip 204 joined with one another are formed. Therefore, the
chip-layered body 214 may have a reduced thickness, and the package
structure including the chip-layered body 214 encapsulated in the
resin package 218 can be made thinner. This permits the
semiconductor device to have a reduced size and improved heat
radiation property. A plurality of chip-layered bodies 214, in
other words a plurality of semiconductor devices having a reduced
size and improved heat radiation property can easily be produced
simply by separating the semiconductor wafer 201 into a plurality
of discrete semiconductor chips 201a.
[0091] Meanwhile, according to the third embodiment, the
semiconductor wafer 201 to be separated into the plurality of
semiconductor chips 201a is not polished for the purpose of
reducing the thickness of the chip-layered body 214. This is
because the area of the semiconductor wafer 201 is larger than the
area of the second semiconductor chip 204, and if therefore the
semiconductor wafer 201 is polished, mechanical defects such as
cracking or chipping are likely to result. In contrast, the second
semiconductor chips 204 are prepared as they are separated as
discrete chips and have a smaller area, and therefore such
mechanical defects are much less likely if the second semiconductor
chips 204 are polished.
[0092] Note that according to the third embodiment, after the step
of polishing the second semiconductor chip 204 from the back
surface (see FIG. 5B), the second semiconductor chip 204 preferably
has a thickness about 1/2 or less of the thickness of the
semiconductor wafer 201 (i.e., the thickness of the first
semiconductor chip 201a). Thus, the package structure including the
chip-layered body 214 encapsulated in the resin package 218 can be
made thinner, so that the semiconductor device can have a more
reduced size and more improved heat radiation property.
[0093] According to the third embodiment, the Sn--Pb alloy is used
as the material of the metal bumps 207, while one selected from Au,
In, Cu, Ni, an In--Sn alloy, a Sn--Ag alloy, a Sn--Cu alloy and a
Sn--Zn alloy may be used. For electrical connection between the
first and second electrodes 202 and 205, a resin having a metallic
filler dispersed therein may be used instead of the metal bumps
207.
[0094] According to the third embodiment, the metal bumps 207 are
formed on the second electrodes 205 on the second semiconductor
chip 204, while the metal bumps 207 may be formed on the first
electrodes 202 provided in each chip region in the semiconductor
wafer 201.
[0095] According to the third embodiment, the resin 208A is the
epoxy resin, while an acrylic resin, a polyimide resin, a urethane
resin or the like can be used. The resin 208A may be any of
thermosetting resin, autopolymer resin, and photosetting resin. The
resin 208A may be preferably applied according to any suitable
method among dispensing, printing and stamping methods and the like
in consideration of the chip size and other conditions.
[0096] According to the third embodiment, the resin 208A is applied
on the surface of each chip region in the semiconductor wafer 201
(the first main surface of each first semiconductor chip 201a),
while the resin 208A may be applied on the second main surface of
the second semiconductor chip 204.
[0097] According to the third embodiment, the resin 208A is applied
before joining the first electrodes 202 and the second electrodes
205 through the metal bumps 207. The resin 208A may be applied in a
different timing such as after joining these electrodes through the
metal bumps 207.
[0098] According to the third embodiment, the resin 208A or resin
layer 208 is interposed between the surfaces of the chip regions in
the semiconductor wafer 201 (i.e., the first main surfaces of the
first semiconductor chips 201a) and the second main surfaces of the
second semiconductor chips 204. Meanwhile, an anisotropic
conductive sheet, an anisotropic conductive resin or the like may
be interposed therebetween.
[0099] [Modification of Third Embodiment]
[0100] A method of manufacturing a semiconductor device according
to a modification of the third embodiment of the invention will be
now descried in conjunction with the accompanying drawings.
[0101] FIGS. 8A, 8B, 9A, 9B and 10 are sectional views showing
steps in the method of manufacturing a semiconductor device
according to the modification of the third embodiment. Note that
according to the modification, the same elements as those in the
third embodiment shown in FIGS. 4A, 4B, 5A, 5B, 6A, 6B and 7 will
be denoted by the same reference characters and will not be
described in some cases.
[0102] Unlike the third embodiment, according to the modification
of the third embodiment, discrete first semiconductor chips 201a
formed by dicing the semiconductor wafer are prepared and then the
first and second semiconductor chips 201a and 204 are
integrated.
[0103] As shown in FIG. 8A, the first semiconductor chip 201a and
the second semiconductor chip 204 having a smaller area than the
first semiconductor chip 201a are registered. Note that there are a
plurality of first electrodes 202 (for connection with bumps) of
Al, for example, and a plurality of bonding pads 203 (for
connection with thin metal wires) of Al, for example, on the first
main surface of the first semiconductor chip 201a. Meanwhile, there
are a plurality of second electrodes 205 of Al, for example, on the
second main surface of the second semiconductor chip 204. The
second electrodes 205 each have a barrier metal layer 206 thereon.
The layer is of a metal thin film such as titanium, copper and
nickel films.
[0104] More specifically, as shown in FIG. 8A, metal bumps 207 of a
Sn--Pb alloy, for example, are formed on the second electrodes 205
on the second semiconductor chip 204 through the barrier metal
layers 206. The metal bump 207 has, for example, a diameter about
in the range from 3 to 100 .mu.m, and a height about in the range
from 3 to 50 .mu.m. The first semiconductor chip 201a is placed on
the packaging jig (not shown) and a resin 208A such as an epoxy
resin is applied on the first main surface of the first
semiconductor chip 201a. Then, the second semiconductor chip 204 is
held over the first semiconductor chip 201a using the tool 209 so
that the main surfaces of the semiconductor chips, i.e., the
circuit forming surfaces are opposed to each other.
[0105] Then, as shown in FIG. 8B, the first semiconductor chip 201a
and the second semiconductor chip 204 are joined with each other.
More specifically, the second semiconductor chip 204 is lowered as
it is held by the tool 209, and the metal bumps 207 formed on the
second electrodes 205 on the second semiconductor chip 204 and the
first electrodes 202 on the first semiconductor chip 201a are
registered. Here, the bonding pads 203 on the first semiconductor
chip 201a are provided outside the region of the first main surface
of the first semiconductor chip 201a opposed to the second main
surface of the second semiconductor chip 204. Then, the second
semiconductor chip 204 is heated and pressed using the tool 209
from the surface opposite to the second main surface. Thus, the
registered first electrodes 202 and metal bumps 207 on the second
semiconductor chip 204 are joined. At the time, the resin 208A
applied on the first main surface of the first semiconductor chip
201a enhances the adhesion between the first and second
semiconductor chips 201a and 204. Note that the pressing force
(load) applied by the tool 209 is suitably about in the range from
0.98 to 196 mN for each metal bump 207, and the load is set on the
condition that the first electrodes 202 are not damaged.
Alternatively, the load could be set on the condition that the
characteristics of elements such as transistors, interconnections
or the like formed under the first electrodes 202 on the first
semiconductor chip 201a are unaffected. Then, the resin 208A is
cured to form the resin layer 208, so that the second and first
semiconductor chips 204 and 201a are integrated.
[0106] Then, as shown in FIG. 9A, in the joined body 210 having the
first semiconductor chip 201a and the second semiconductor chip 204
placed thereon, the back surface of the second semiconductor chip
204 (the surface opposite to the second main surface) is polished.
More specifically, the resin 208A is sufficiently cured to form the
resin layer 208 and then the joined body 210 is placed on the
polishing machine 211 so that the back surface of the second
semiconductor chip 204 is opposed to the upper surface (polishing
surface) of the polishing machine 211. Abrasive grains 213 are
supplied to the polishing surface of the polishing machine 211, and
then the joined body 210 is loaded with weight as the polishing
machine 211 is rotated to polish the back surface of the second
semiconductor chip 204. At the time, in the joined body 210 removed
from the polishing machine 211, the thickness of the second
semiconductor chip 204 decreases in inverse proportion to the
duration of the polishing time period. Note that for the abrasive
grains 213, diamond grains having a grain size in the range from
#1200 to #2000 are preferably used, and the polishing machine 211
is preferably rotated at about 5 to 50 rpm.
[0107] According to the modification of the third embodiment, the
back surface of the second semiconductor chip 204 is polished so
that the thickness of the second semiconductor chip 204 is at least
smaller than that of the first semiconductor chip 201a. More
specifically, the thickness of the polished semiconductor chip 204
preferably has a thickness about in the range from 50 to 100 .mu.m.
Note that the second semiconductor chip 204 before the polishing
has a thickness about in the range from 200 to 300 .mu.m which is
about as large as the thickness of the first semiconductor chip
201a.
[0108] As shown in FIGS. 9B and 10, the chip-layered body 214
including the first semiconductor chip 201a and the second
semiconductor chip 204 having a polished back surface joined with
one another is subjected to die-bonding and wire-bonding, and resin
encapsulation. More specifically, a lead frame 215 having a die pad
portion 215a and lead portions 215b is prepared. The back surface
of the first semiconductor chip 201a of the chip-layered body 214
(the surface opposite to the first main surface) is secured on the
die pad portion 215a with conductive paste 216 containing Pd, Ag or
the like. Then, the bonding pads 203 on the first semiconductor
chip 201a and the lead portions 215b are electrically connected
with one another through the thin metal bonding wires 217. The thin
metal wires have a diameter of about 25 .mu.m. The material of the
thin metal wires can be for example Au or Al. Finally, the first
semiconductor chip 201a, the second semiconductor chip 204, the die
pad portion 215a and lead portions 215b of the lead frame 215 and
the bonding wires 217 are encapsulated in a resin package 218 of an
epoxy-based resin or a polyimide-based resin. Note, however, that
the bottom surface of the die pad portion 215a and the bottom and
outer side surfaces of the lead portions 215b are exposed out of
the resin package 218, so that the bottom and outer side surfaces
of the lead portions 215b can serve as external terminals.
[0109] As in the foregoing, according to the modification of the
third embodiment, the first and second semiconductor chips 201a and
204 are integrated to face to one another, and then the second
semiconductor chip 204 is polished from the opposite side to the
main surface (i.e., the circuit forming surface) so that the second
semiconductor chip 204 is made thinner than the first semiconductor
chip 201a. Therefore, the layered-body (chip-layered body 214)
including the first and second semiconductor chips 201a and 204 can
have a reduced thickness. As a result, the package structure
including the chip-layered body 214 encapsulated in the resin
package 218 can be made thinner, which allows the semiconductor
device to have a reduced size and improved heat radiation
property.
[0110] According to the modification of the third embodiment, after
the step of polishing the second semiconductor chip 204 from the
back surface (see FIG. 9A), the thickness of the second
semiconductor chip 204 is preferably reduced to 1/2 or less of the
thickness of the first semiconductor chip 201a. Thus, the package
structure including the chip-layered body 214 encapsulated in the
resin package 218 can be made thinner, and therefore the
semiconductor device can have a more reduced size and higher heat
radiation property.
[0111] According to the modification of the third embodiment, the
Sn--Pb alloy is used for the material of the metal bumps 207, while
any one of Au, In, Cu, Ni, an In--Sn alloy, a Sn--Ag alloy, a
Sn--Cu alloy, and a Sn--Zn alloy may be used. As the material for
electrical connection between the first and second electrodes 202
and 205, conductive paste, an anisotropic conductive resin or a
resin having a metallic filler dispersed therein may be used
instead of the metal bumps 207.
[0112] According to the modification of the third embodiment, the
metal bumps 207 are formed on the second electrodes 205 on the
second semiconductor chip 204, while the metal bumps 207 may be
formed on the first electrodes 202 on the first semiconductor chip
201a.
[0113] According to the modification of the third embodiment, the
resin 208A is the epoxy resin, while an acrylic resin, a polyimide
resin, a urethane resin or like may be used. The resin 208A may be
any of thermosetting resin, autopolymer resin and photosetting
resin. The resin 208A is preferably applied by any suitable method
among dispensing, printing and stamping methods and the like in
consideration of the chip size and other conditions.
[0114] According to the modification of the third embodiment, the
resin 208A is applied on the first main surface of the first
semiconductor chip 201a, while the resin 208A may be applied on the
second main surface of the second semiconductor chip 204.
[0115] According to the modification of the third embodiment, the
resin 208A is applied before joining the first and second
electrodes 202 and 205 through the metal bumps 207, while the resin
208A may be applied in a different timing such as after joining
these electrodes through the metal bumps 207.
[0116] According to the modification of the third embodiment, the
resin 208A or resin layer 208 is interposed between the first main
surface of the first semiconductor chip 201a and the second main
surface of the second semiconductor chip 204, while an anisotropic
conductive sheet or an anisotropic conductive resin may be
interposed.
[0117] [Fourth Embodiment]
[0118] A method of manufacturing a semiconductor device according
to a fourth embodiment of the present invention will be now
described.
[0119] FIGS. 11A, 11B, 12A, 12B, 13A, 13B and 14 are sectional
views showing steps in the method of manufacturing a semiconductor
device according to the fourth embodiment.
[0120] As shown in FIG. 11A, similarly to the step shown in FIG. 4A
according to the third embodiment, a semiconductor wafer 201 and a
second semiconductor chip 204 are registered. The wafer 201 has a
plurality of chip regions to be a plurality of semiconductor chips
201a (see FIG. 13A). The second semiconductor chip 204 has a
smaller area than a chip region (i.e., the first semiconductor chip
201a). Note that FIGS. 11A, 11B, 12A, 12B, and 13A show the
boundaries between the chip regions by the dotted lines.
[0121] Here, elements such as transistors or interconnections are
formed in the chip regions in the semiconductor wafer 201. A
plurality of first electrodes 202 (for connection with bumps) of
Al, for example, and a plurality of bonding pads 203 (for
connection with thin metal wires) of Al, for example, are formed on
the surface of each of the chip regions (i.e., the first main
surface of the semiconductor chips 201a) in the semiconductor wafer
201. The bonding pad 203 corresponds to the "third electrode" in
the section of "What is claimed is." Meanwhile, a plurality of
second electrodes 205 of Al, for example, are provided on the
second main surface of the second semiconductor chip 204. Barrier
metal layers 206 of a thin metal film of titanium, copper, nickel
or the like is provided on the second electrodes 205.
[0122] More specifically, as shown in FIG. 11A, metal bumps 207 of
a Sn--Pb alloy, for example, are formed on the second electrodes
205 on the second semiconductor chip 204 through the barrier metal
layers 206. The metal bump 207 has a diameter of about 3 to 100
.mu.m and a height of about 3 to 50 .mu.m. The semiconductor wafer
201 is placed on a packaging jig (not shown) and a resin 208A such
as an epoxy resin is applied on the surface of one chip region in
the semiconductor wafer 201. The second semiconductor chip 204 is
held using the tool 209 over the chip region in the semiconductor
wafer 201 so that the surface of the chip region and the second
main surface of the second semiconductor chip 204 are opposed to
each other.
[0123] As shown in FIG. 11B, similarly to the step shown in FIG. 4B
according to the third embodiment, the chip region in the
semiconductor wafer 201 and the second semiconductor chip 204 are
joined with one another. More specifically, the second
semiconductor chip 204 is lowered as it is held by the tool 209.
Thus, the metal bumps 207 formed on the second electrodes 205 on
the second semiconductor chip 204 and the first electrodes 202
provided in the chip region in the semiconductor wafer 201 are
registered. Here, the bonding pads 203 in the chip region in the
semiconductor wafer 201 are formed outside the region of the
surface of the chip region opposed to the second main surface of
the second semiconductor chip 204.
[0124] Then, the second semiconductor chip 204 is heated and
pressed using the tool 209 from the surface opposite to the second
main surface. As a result, the registered first electrodes 202 and
the metal bumps 207 on the second semiconductor chip 204 are joined
by physical or metallurgical effect. At the time, the resin 208A
previously applied on the surface of the chip region in the
semiconductor wafer 201 enhances the adhesion between the
semiconductor wafer 201 and the second semiconductor chip 204. Note
that the pressing force (load) by the tool 209 is suitably about in
the range from 0.98 to 196 mN for each metal bump 207, and the load
is set on the condition that the first electrodes 202 are not
damaged. Alternatively, the load may be set on the condition that
the characteristics of elements such as transistors or
interconnections formed under the first electrodes 202 in the
semiconductor wafer 201 are unaffected.
[0125] Then, the resin 208A is cured to form the resin layer 208,
so that the second semiconductor chip 204 and the semiconductor
wafer 201 are integrated. At the time, if the resin 208A which is a
photosetting resin, it is cured by irradiation of ultraviolet rays.
If the resin 208A is a thermosetting resin, it is cured by heating.
In this case, the resin 208A is heated using heating instrument
such as an oven after it is released from the pressing by the tool
209 or directly heated during the pressing step by the tool 209
using a heater installed in the tool 209. The resin is
appropriately heated for curing at a temperature of about 70 to
300.degree. C. though the temperature depends on the material of
the resin 208A.
[0126] The steps shown in FIGS. 11A and 11B are repeated as many
times as the number of chip regions provided in the semiconductor
wafer 201, so that the joined body 210 as shown in FIG. 12(a)
results. As shown, a plurality of second semiconductor chips 204
are provided in the chip regions in the semiconductor wafer
201.
[0127] As shown in FIG. 12B, similarly to the step shown in FIG. 5B
according to the third embodiment, the back surface of the second
semiconductor chip 204 (the surface opposite to the second main
surface) in the joined body 210 is polished. More specifically, the
resin 208A is sufficiently cured to form the resin layer 208. The
joined body 210 is then placed on the polishing machine 211 so that
the back surfaces of the second semiconductor chips 204 in the chip
regions in the semiconductor wafer 201 are opposed to the upper
surface (polishing surface) of the polishing machine 211. There is
a protection resin 212 between the second semiconductor chips 204
placed in the chip regions in the semiconductor wafer 201.
[0128] According to the fourth embodiment, the protection resin 212
is a thermosetting liquid resin, and supplied between the second
semiconductor chips 204 on the surface of the semiconductor wafer
201 by spraying, centrifugal spin coating, attaching resin taping
or the like.
[0129] Abrasive grains 213 are supplied to the polishing surface of
the polishing machine 211, and then the polishing machine 211 is
rotated as the joined body 210 is loaded with weight, so that the
back surfaces of the second semiconductor chips 204 are polished.
At the time, in the joined body 210 removed from the polishing
machine 211, the thickness of the second semiconductor chip 204 on
the semiconductor wafer 201 decreases in inverse proportion to the
duration of the polishing time. More specifically, the polished
second semiconductor chip 204 may have a thickness about in the
range from 50 to 100 .mu.m. The semiconductor wafer 201 has a
thickness about in the range from 200 to 300 .mu.m (which is
substantially equal to the thickness of the second semiconductor
chip 204 before polishing). The thickness of the second
semiconductor chip 204 is at least smaller than that of the
semiconductor wafer 201 (i.e., the thickness of the first
semiconductor chip 201a). Note that the abrasive grains 213 are
preferably diamond grains having a grain size in the range from
#1200 to #2000, and the polishing machine 211 is preferably rotated
at about 5 to 50 rpm.
[0130] As shown in FIG. 13A, similarly to the step shown in FIG. 6A
according to the third embodiment, the semiconductor wafer 201 is
separated by dicing. More specifically, the chip regions in the
semiconductor wafer 201 in the joined body 210 are separated as a
plurality of discrete first semiconductor chips 201a by dicing.
Thus, a plurality of chip-layered bodies 214 each including one
first semiconductor chip 201a and one second semiconductor chip 204
joined with each other result. For the ease of illustration, only a
single chip-layered body 214 will be described.
[0131] As shown in FIG. 13B, the chip-layered body 214 is subjected
to die-bonding and wire-bonding. More specifically, a lead frame
215 having a die pad portion 215a and lead portions 215b is
prepared, and the back surface of the first semiconductor chip 201a
(the surface opposite to the first main surface) of the
chip-layered body 214 is secured on the die pad portion 215a with
conductive paste 216 containing Pd, Ag or the like. Then, the
bonding pads 203 on the first semiconductor chip 201a and the lead
portions 215b are electrically connected through thin metal bonding
wires 217. Here, the thin metal wire has a diameter of about 25
.mu.m. The material of the thin metal wire can be Au, Al or the
like.
[0132] According to the fourth embodiment, as shown in FIG. 13B,
the back surface of the second semiconductor chip 204 is polished
so that the distance T.sub.chip from the first main surface of the
first semiconductor chip 201a to the back surface of the second
semiconductor chip 204 (the surface opposite to the second main
surface) is smaller than the distance T.sub.wb from the first main
surface of the first semiconductor chip 201a to the highest
position of the bonding wire 217 on the first main surface (the
peak of the loop of the bonding wire 217). More specifically, the
distance T.sub.chip is about 100 to 150 .mu.m and T.sub.wb is about
150 to 400 .mu.m though they vary depending on the kind of the
semiconductor device.
[0133] Then, as shown in FIG. 14, similarly to the step shown in
FIG. 7 according to the third embodiment, the chip-layered body 214
after the wire-bonding step is encapsulated in a resin. More
specifically, the first semiconductor chip 201a, the second
semiconductor chip 204, the die pad portion 215a and the lead
portions 215b of the lead frame 215, and the bonding wires 217 are
encapsulated in a resin package 218 of an epoxy-based resin, a
polyimide-based resin or the like. Note however that the bottom
surface of the die pad portion 215a and the bottom and outer side
surfaces of the lead portions 215b are exposed out of the resin
package 218. Thus, the bottom and outer side surfaces of the lead
portions 215b can serve as external terminals.
[0134] As in the foregoing, according to the fourth embodiment, the
plurality of first semiconductor chips 201a in the semiconductor
wafer 201 and a plurality of discrete second semiconductor chips
204 are integrated to face to one another. Then, the semiconductor
chips 204 are polished from the opposite side of their main
surfaces (circuit forming surfaces). Therefore, the second
semiconductor chips 204 have a thickness smaller than that of the
semiconductor wafer 201, i.e., the thickness of the first
semiconductor chips 201a. The semiconductor wafer 201 is then
separated into a plurality of discrete semiconductor chips 201a, so
that a plurality of chip-layered bodies 214 each including a
discrete first semiconductor chip 201a and a discrete second
semiconductor chip 204 joined with one another result. As a result,
the chip-layered body 214 may have a reduced thickness so that the
package structure including the chip-layered body 214 encapsulated
in the resin package 218 can be thinner. As a result, the
semiconductor device may have a reduced size and improved heat
radiation property. Thus, the plurality of chip-layered bodies 214,
in other words the plurality of semiconductor devices having a
reduced size and improved heat radiation property can readily be
manufactured simply by separating the semiconductor wafer 201 into
the plurality of discrete first semiconductor chips 201a.
[0135] According to the fourth embodiment, the back surface of the
second semiconductor chip 204 is polished so that the distance from
the first main surface of the first semiconductor chip 201a to the
back surface of the second semiconductor chip 204 is smaller than
the distance from the first main surface of the first semiconductor
chip 201a to the peak of the loop of the bonding wire 217. As a
result, if the chip-layered body 214 is placed on the lead frame
215 in the semiconductor device, the device can surely have a
reduced size and improved heat radiation property.
[0136] Note that according to the fourth embodiment, after the step
of polishing the second semiconductor chip 204 from the back
surface (see FIG. 12B), the second semiconductor chips 204
preferably have a thickness equal to or less than 1/2 of the
thickness of the semiconductor wafer 201 (i.e., the first
semiconductor chips 201a). In this way, the package structure
including the chip-layered body 214 encapsulated in the resin
package 218 can be made thinner. Therefore, the semiconductor
device can have a more reduced size and more improved heat
radiation property.
[0137] Also according to the fourth embodiment, the Sn--Pb alloy is
used for the material of the metal bumps 207, while any one of Au,
In, Cu, Ni, an In--Sn alloy, a Sn--Ag alloy, a Sn--Cu alloy, a
Sn--Zn alloy and the like can be used. For the material used for
electrical connection between the first electrodes 202 and the
second electrodes 205, a resin having a metallic filler dispersed
therein may be used instead of the metal bumps 207.
[0138] According to the fourth embodiment, the metal bumps 207 are
formed on the second electrodes 205 on the second semiconductor
chip 204, while the metal bumps 207 may be formed on the first
electrodes 202 provided in the chip regions in the semiconductor
wafer 201.
[0139] According to the fourth embodiment, the resin 208A is the
epoxy resin, while an acrylic resin, a polyimide resin, a urethane
resin or the like may be used. The resin 208A may be any of
thermosetting resin, autopolymer resin, photosetting resin and the
like. The resin 208A may preferably be applied by any suitable
method among dispensing, printing, and stamping methods and the
like in consideration of the chip size and other conditions.
[0140] According to the fourth embodiment, the resin 208A is
applied on the surface of the chip region in the semiconductor
wafer 201 (i.e., the first main surface of the first semiconductor
chip 201a), while the resin 208A may be applied on the second main
surface of the second semiconductor chip 204.
[0141] According to the fourth embodiment, the resin 208A is
applied before joining the first and second electrodes 202 and 205
through the metal bumps 207, while the resin 208A may be applied in
a different timing such as after joining the first and second
electrodes 202 and 205 through the metal bumps 207.
[0142] According to the fourth embodiment, the resin 208A or resin
layer 208 is interposed between the surface of each chip region in
the semiconductor wafer 201 (i.e., the first main surface of each
of the first semiconductor chips 201a) and the second main surface
of each of the second semiconductor chips 204. Meanwhile, an
anisotropic conductive sheet, an anisotropic conductive resin or
the like may be interposed therebetween.
[0143] [Modification of Fourth Embodiment]
[0144] A method of manufacturing a semiconductor device according
to a modification of the fourth embodiment of the present invention
will be now described.
[0145] FIGS. 15A, 15B, 16A, 16B and 17 are sectional views showing
steps in the method of manufacturing a semiconductor device
according to the modification of the fourth embodiment. The same
elements as those in the fourth embodiment shown in FIGS. 11A, 11B,
12A, 12B, 13A, 13B and 14 will be denoted by the same reference
characters and will not be detailed in some cases.
[0146] Unlike the fourth embodiment, according to the modification
of the fourth embodiment, discrete first semiconductor chips 201a
formed by dicing a semiconductor wafer are prepared, and then the
first and second semiconductor chips 201a and 204 are
integrated.
[0147] As shown in FIG. 15A, similarly to the step shown in FIG. 8A
according to the modification of the third embodiment, the first
semiconductor chip 201a and the second semiconductor chip 204
having a smaller area than the first semiconductor chip 201a are
registered. Note that on the first main surface of the first
semiconductor chip 201a, there are a plurality of first electrodes
202 of Al, for example, (for connection with bumps) and a plurality
of bonding pads 203 of Al, for example (for connection with thin
metal wires). Meanwhile, there are a plurality of second electrodes
205 of Al, for example, on the second main surface of the second
semiconductor chip 204. There is a barrier metal layer 206 of a
thin metal film such as titanium, copper and nickel films is formed
on each of the second electrodes 205.
[0148] More specifically, as shown in FIG. 15A, metal bumps 207 of
a Sn--Pb alloy, for example, are formed on the second electrodes
205 on the second semiconductor chip 204 through the barrier metal
layers 206. The metal bumps 207 have, for example, a diameter about
in the range from 3 to 100 .mu.m and a height about in the range
from 3 to 50 .mu.m. The first semiconductor chip 201a is placed on
a packaging jig (not shown) and a resin 208A such as an epoxy resin
is applied on the first main surface of the first semiconductor
chip 201a. Then, the second semiconductor chip 204 is held over the
first semiconductor chip 201a using a tool 209 so that their main
surfaces i.e., the circuit forming surfaces are opposed to one
another.
[0149] As shown in FIG. 15B, similarly to the step shown in FIG. 8B
according to the modification of the third embodiment, the first
and second semiconductor chips 201a and 204 are joined with one
another. More specifically, the second semiconductor chip 204 is
lowered as it is held by the tool 209. Then, the metal bumps 207
formed on the second electrodes 205 on the second semiconductor
chip 204 and the first electrodes 202 on the first semiconductor
chip 201a are registered. Here, the bonding pads 203 on the first
semiconductor chip 201a are provided outside the region of the
first main surface of the first semiconductor chip 201a opposed to
the second main surface of the second semiconductor chip 204. Then,
the second semiconductor chip 204 is heated and pressed using the
tool 209 from the surface opposite to the second main surface.
Thus, the registered first electrodes 202 and metal bumps 207 on
the second semiconductor chip 204 are joined with one another. The
resin 208A applied on the first main surface of the first
semiconductor chip 201a enhances the adhesion between the first and
second semiconductor chips 201a and 204. Note that the pressing
force (load) by the tool 209 is suitably about 0.98 to 196 mN for
each metal bump 207, while the load is set on the condition that
the first electrodes 202 are not damaged. Alternatively, the load
may be set on the condition that the characteristics of elements
such as transistors and interconnections and the like formed under
the first electrodes 202 are unaffected. Then, the resin 208A is
cured to form a resin layer 208, so that the second semiconductor
chip 204 and the first semiconductor chip 201a are integrated.
[0150] As shown in FIG. 16A, similarly to the step shown in FIG. 9A
according to the modification of the third embodiment, the back
surface of the second semiconductor chip 204 (the surface opposite
to the second main surface) in the joined body 210 having the
second semiconductor chips 204 placed on the first semiconductor
chip 201a is polished. More specifically, the resin 208A is
sufficiently cured to form the resin layer 208, and then the joined
body 210 is placed on a polishing machine 211 so that the back
surface of the second semiconductor chip 204 is opposed to the
upper surface (polishing surface) of the polishing machine 211. The
polishing surface of the polishing machine 211 is supplied with
abrasive grains 213, and then the polishing machine 211 is rotated
as the joined body 210 is pressed, so that the back surface of the
second semiconductor chip 204 is polished. At the time, in the
joined body 210 removed from the polishing machine 211, the
thickness of the second semiconductor chip 204 decreases in inverse
proportion to the duration of the polishing time. More
specifically, the polished second semiconductor chip 204 can have a
thickness about in the range from 50 to 100 .mu.m. The first
semiconductor chip 201a has a thickness of about 200 to 300 .mu.m
(which is substantially equal to the thickness of the second
semiconductor chip 204 before the polishing step). Therefore, the
second semiconductor chip 204 has a thickness at least smaller than
the thickness of the first semiconductor chip 201a. Note that the
abrasive grains 213 may preferably be diamond grains having a grain
size in the range from #1200 to #2000, and the polishing machine
211 is preferably rotated at about 5 to 50 rpm.
[0151] As shown in FIGS. 16B and 17, the chip-layered body 214
including the first semiconductor chip 201a and the second
semiconductor chip 204 having a polished back surface joined with
one another is subjected to die-bonding and wire-bonding and resin
encapsulation. More specifically, a lead frame 215 having a die pad
portion 215a and lead portions 215b is prepared. The back surface
of the first semiconductor chip 201a of the chip-layered body 214
(the surface opposite to the first main surface) is secured on the
die pad portion 215a, for example, with conductive paste 216
containing Pd, Ag or the like. Then, the bonding pads 203 on the
first semiconductor chip 201a and the lead portions 215b are
electrically connected through thin metal bonding wires 217. Here,
the thin metal wire has a diameter of about 25 .mu.m. The material
of the thin metal wire may be Au, Al or the like.
[0152] According to the modification of the fourth embodiment, as
shown in FIG. 17, the back surface of the second semiconductor chip
204 is polished so that the distance T.sub.chip from the first main
surface of the first semiconductor chip 201a to the back surface of
the second semiconductor chip 204 (the surface opposite to the
second main surface) is smaller than the distance T.sub.wb from the
first main surface of the first semiconductor chip 201a to the
highest position of the bonding wire 217 (i.e., the peak of the
loop of the bonding wire 217) on the first main surface. More
specifically, the distance T.sub.chip is about in the range from
100 to 150 .mu.m, and T.sub.wb is about in the range from 150 to
400 .mu.m.
[0153] Finally, the first semiconductor chip 201a, the second
semiconductor chip 204, the die pad portion 215a and lead portions
215b of the lead frame 215, and the bonding wires 217 are
encapsulated in a resin package 218 of, for example, an epoxy-based
resin or a polyimide-based resin. However, the bottom surface of
the die pad portion 215a, and the bottom and outer side surfaces of
the lead portions 215b are exposed out of the resin package 218, so
that the bottom and outer side surfaces of the lead portions 215b
serve as external terminals.
[0154] As in the foregoing, according to the modification of the
fourth embodiment, the first and second semiconductor chips 201a
and 204 are integrated to face to one another, and then the second
semiconductor chip 204 is polished from the side opposite to the
main surface (i.e., circuit forming surface), so that the second
semiconductor chip 204 has a thickness smaller than the thickness
of the first semiconductor chip 201a. As a result, the layered body
(chip-layered body 214) of the first and second semiconductor chips
201a and 204 can have a reduced thickness. Therefore, the package
structure including the chip-layered body 214 encapsulated in the
resin package 218 can be made thinner, and the semiconductor device
can have a reduced size and improved heat radiation property.
[0155] According to the modification of the fourth embodiment, the
back surface of the second semiconductor chip 204 is polished so
that the distance from the first main surface of the first
semiconductor chip 201a to the back surface of the second
semiconductor chip 204 is smaller than the distance from the first
main surface of the first semiconductor chip 201a to the peak of
the loop of the bonding wire 217. Therefore, if the chip-layered
body 214 is placed on the lead frame 215 in the semiconductor
device, the device may surely have a reduced size and improved heat
radiation property.
[0156] According to the modification of the fourth embodiment,
after the step of polishing the second semiconductor chip 204 from
the back surface (see FIG. 16A), the second semiconductor chip 204
preferably has a thickness about 1/2 or less of the thickness of
the first semiconductor chip 201a. In this way, the package
structure including the chip-layered body 214 encapsulated in the
resin package 218 can be made thinner, so that the semiconductor
device can have a more reduced size and higher heat radiation
property.
[0157] According to the modification of the fourth embodiment, the
Sn--Pb alloy is used for the material of the metal bumps 207, while
any one of Au, In, Cu, Ni, an In--Sn alloy, a Sn--Ag alloy, a
Sn--Cu alloy and a Sn--Zn alloy may be used. The material used for
electrical connection between the first and second electrodes 202
and 205 may be conductive paste, an anisotropic conductive resin or
a resin having a metallic filler dispersed therein instead of the
metal bumps 207.
[0158] According to the modification of the fourth embodiment, the
metal bumps 207 are formed on the second electrodes 205 on the
second semiconductor chip 204, while the metal bumps 207 may be
formed on the first electrodes 202 on the first semiconductor chip
201a.
[0159] According to the modification of the fourth embodiment, the
resin 208A is the epoxy resin, while an acrylic resin, a polyimide
resin, a urethane resin or the like can be used. The resin 208A may
be any of thermosetting, autopolymer, photosetting resin and the
like. The resin 208A may preferably be applied by any of
dispensing, printing and stamping methods and the like in
consideration of the chip size and other conditions.
[0160] According to the modification of the fourth embodiment, the
resin 208A is applied on the first main surface of the first
semiconductor chip 201a, while the resin 208A may be applied on the
second main surface of the semiconductor chip 204.
[0161] According to the modification of the fourth embodiment, the
resin 208A is applied before joining the first and second
electrodes 202 and 205 through the metal bumps 207, while the resin
208A may be applied in a different timing such as after joining
these electrodes through the metal bumps 207.
[0162] According to the modification of the fourth embodiment, the
resin 208A or resin layer 208 is interposed between the first main
surface of the first semiconductor chip 201a and the second main
surface of the second semiconductor chip 204, while an anisotropic
conductive sheet, anisotropic conductive resin or the like may be
interposed.
* * * * *