U.S. patent application number 14/406997 was filed with the patent office on 2015-06-11 for semiconductor device.
The applicant listed for this patent is Seiko Instruments Inc.. Invention is credited to Shoji Nakanishi, Tomomitsu Risaki, Hitomi Sakurai, Koichi Shimazaki.
Application Number | 20150162296 14/406997 |
Document ID | / |
Family ID | 49758019 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150162296 |
Kind Code |
A1 |
Risaki; Tomomitsu ; et
al. |
June 11, 2015 |
SEMICONDUCTOR DEVICE
Abstract
In order to inhibit a crack under a pad opening without
increasing a chip size, a protective film (6) includes a pad
opening (9) that exposes a part of a topmost layer metal film (3).
The pad opening (9) is rectangular and square, and has an opening
width of d0. A second metal film (2) has an opening under the pad
opening (9). The opening is rectangular and square, and has an
opening width of d4. A distance between an opening edge of the
protective film (6) and an opening edge of the second metal film
(2) is d3. The second metal film (2) has a rectangular donut shape,
and protrudes to an inner side of the pad opening (9) by the
distance d3.
Inventors: |
Risaki; Tomomitsu;
(Chiba-shi, JP) ; Nakanishi; Shoji; (Chiba-shi,
JP) ; Sakurai; Hitomi; (Chiba-shi, JP) ;
Shimazaki; Koichi; (Chiba-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Instruments Inc. |
Chiba-shi, Chiba |
|
JP |
|
|
Family ID: |
49758019 |
Appl. No.: |
14/406997 |
Filed: |
May 21, 2013 |
PCT Filed: |
May 21, 2013 |
PCT NO: |
PCT/JP2013/063999 |
371 Date: |
December 10, 2014 |
Current U.S.
Class: |
257/774 |
Current CPC
Class: |
H01L 23/522 20130101;
H01L 2224/05553 20130101; H01L 24/85 20130101; H01L 2224/05085
20130101; H01L 2224/85205 20130101; H01L 2224/45144 20130101; H01L
2224/85205 20130101; H01L 2924/35 20130101; H01L 2924/00014
20130101; H01L 24/48 20130101; H01L 2224/05011 20130101; H01L
2224/05555 20130101; H01L 2924/00014 20130101; H01L 2924/00014
20130101; H01L 2224/85181 20130101; H01L 2224/78301 20130101; H01L
24/05 20130101; H01L 24/45 20130101; H01L 27/0296 20130101; H01L
2224/78303 20130101; H01L 2224/05554 20130101; H01L 23/5283
20130101; H01L 2224/48451 20130101; H01L 2224/48463 20130101; H01L
2224/05096 20130101; H01L 2224/02166 20130101; H01L 2224/45144
20130101; H01L 2224/04042 20130101; H01L 2224/05014 20130101; H01L
2224/05599 20130101; H01L 23/5226 20130101; H01L 2924/00015
20130101; H01L 2224/05099 20130101; H01L 2924/00014 20130101; H01L
2224/05599 20130101; H01L 2224/05013 20130101; H01L 2224/05095
20130101; H01L 24/78 20130101; H01L 23/60 20130101 |
International
Class: |
H01L 23/00 20060101
H01L023/00; H01L 23/60 20060101 H01L023/60; H01L 23/522 20060101
H01L023/522 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 15, 2012 |
JP |
2012-136288 |
Claims
1. A semiconductor device having a pad structure comprising a
plurality of metal films, the semiconductor device comprising: a
semiconductor substrate; a first insulating film formed on a
surface of the semiconductor substrate; a first metal film formed
on the first insulating film; a second insulating film formed on
the first metal film; a first part of the second metal film formed
on the second insulating film; a first via formed in the second
insulating film to connect the first metal film and the first part
of the second metal film; a third insulating film formed on the
first part of the second metal film; a topmost layer metal film
formed on the third insulating film; a second via formed in the
third insulating film to connect the first part of the second metal
film and the topmost layer metal film; and a protective film formed
on the topmost layer metal film and having a pad opening formed
therein to expose a part of a surface of the topmost layer metal
film, the first part of the second metal film having a rectangular
donut shape and having an opening under the pad opening, the
opening being located outside a beveled corner at a tip of a
capillary for a ball bonder used for ball bonding, the first part
of the second metal film protruding to an inner side of the pad
opening by a predetermined amount of protrusion.
2. A semiconductor device according to claim 1, wherein both the
pad opening and the opening are square.
3. A semiconductor device according to claim 2, wherein the
predetermined amount of protrusion satisfies the following
relationship: d3=(d0-d4)/2, where d3 is the predetermined amount of
protrusion, d0 is a length of a side of the pad opening, and d4 is
a length of a side of the opening in the first part of the second
metal film in the same direction as the side of the pad
opening.
4. A semiconductor device according to claim 2, wherein the
following relationship is satisfied: d0>r2 and d4>r1, where
d0 is a length of a side of the pad opening, d4 is a length of a
side of the first part of the second metal film located under a
side of the opening, r2 is a width of a crushed ball, and r1 is a
width of the beveled corner.
5. A semiconductor device according to claim 1, further comprising
a second part of the second metal film formed under the pad
opening, being absent under the beveled corner in the ball bonding,
so as to avoid being held in contact with the first part of the
second metal film having a rectangular donut shape and formed under
the pad opening, the second part of the second metal film being
rectangular or circular in cross section.
6. A semiconductor device according to claim 1, further comprising
a second part of the second metal film formed under the pad
opening, being absent under the beveled corner in the ball bonding,
so as to avoid being held in contact with the first part of the
second metal film having a rectangular donut shape and formed under
the pad opening, the second part of the second metal film
comprising a combination including a group of a plurality of
rectangles or circles in cross section.
7. A semiconductor device according to claim 5, wherein the second
part of the second metal film being rectangular or circular is
electrically connected to the topmost layer metal film through the
second via.
8. A semiconductor device according to claim 1, wherein the first
part of the second metal film has a slit formed therein.
9. A semiconductor device according to claim 1, further comprising
an element formed under the pad opening.
10. A semiconductor device according to claim 9, wherein the
element is an ESD protection element.
Description
TECHNICAL FIELD
[0001] The present invention relates to a semiconductor device
having a pad structure.
BACKGROUND ART
[0002] In a semiconductor device wire bonding is used to connect a
pad of the semiconductor device to an external connection terminal
through a metal wire to exchange electrical signals with the
outside. Since the wire bonding is a mechanical process of bonding
a wire formed of gold or the like to the pad of the semiconductor
device with use of heat, ultrasound, or weight, the semiconductor
device may thereby receive damage. Detail is described with
reference to FIGS. 11(a) and 11(b). A balled wire 15 formed at a
tip of a bonding wire 14 is press-fitted to a topmost layer metal
film 3 in a pad opening formed in the semiconductor device,
becoming a crushed ball 16, and the bonding wire 14 is thus bonded
to the topmost layer metal film 3 in the pad opening. At this time,
a crack 18 may develop in an insulating film 5 formed under the pad
opening, which affects reliability of the semiconductor device.
[0003] Patent Literature 1 describes that, by devising a capillary
structure of a ball bonding apparatus for the purpose of preventing
a crack, bonding damage is inhibited, and development of a crack
can be inhibited.
[0004] In Background Art of Patent Literature 2, it is described
that, in order to keep strength against bonding so as to prevent a
crack, there is formed a thick metal film in the pad opening in
direct contact with the bonding wire. The metal film itself absorbs
the bonding damage, inhibiting a crack and enhancing the crack
resistance of the pad structure itself.
[0005] Further, in Patent Literature 3, as illustrated in FIG. 12,
there is disclosed a pad structure in which an effective thickness
of an insulating film formed under a pad opening 9 that receives
the bonding damage is increased. A second metal film 2 is not
formed under the topmost layer metal film 3 in the pad opening 9. A
thickness of insulating films between a first metal film 1 and the
topmost layer metal film 3 is a sum of a thickness of a second
insulating film 4 and a thickness of a third insulating film 5, and
an effective thickness of the insulating films formed under the pad
opening 9 that receives the bonding damage is increased. The thick
insulating film absorbs the bonding damage, inhibiting a crack.
Arrangement of wiring and the like of the first metal film 1 under
the pad opening 9 can reduce the chip size.
CITATION LIST
Patent Literature
[0006] [PTL 1] JP 04-069942 A
[0007] [PTL 2] JP 2011-055006 A
[0008] [PTL 3] JP 11-186320 A
SUMMARY OF INVENTION
Technical Problem
[0009] In the case of Patent Literature 1, when the strength
against bonding is reduced, a disadvantage in that the wire bonding
is liable to be disconnected may easily occur.
[0010] In the case of Patent Literature 2, the topmost layer metal
film in the pad structure becomes thick, and processing of the
metal film becomes difficult. As a result, the wiring width of the
metal film cannot be sufficiently reduced, and the chip size
increases.
[0011] In the structure of Patent Literature 3 illustrated in FIG.
12, in order to reduce a parasitic resistance to an element in a
semiconductor device of the pad structure so as not to affect
electrical characteristics of an IC, as illustrated in FIG. 13(a),
a distance d1 from an opening edge of the pad opening 9 to an edge
of the topmost layer metal film 3 of the pad structure is
increased, or alternatively, as illustrated in FIG. 13(b), a
distance d2 from an edge of the topmost layer metal film 3 of the
pad structure to an edge of the second metal film 2 is increased,
to thereby enable a large number of vias to be arranged. However,
the larger pad structure as illustrated in sectional views of FIG.
13 accordingly increases the chip size.
[0012] The present invention has been made in view of the drawback
that the chip size increases as described above, and an object of
the present invention is to provide a semiconductor device that
inhibits a crack under a pad opening without increasing a chip
size.
Solution to Problem
[0013] According to one embodiment of the present invention, in
order to solve the problem described above, there is provided a
semiconductor device having a pad structure, the semiconductor
device including: a metal film having a rectangular opening under a
pad opening, the metal film having a rectangular donut shape, the
metal film protruding to an inner side of the pad opening by a
predetermined distance, being absent under a beveled corner at a
tip of a capillary for a ball bonder in ball bonding; an insulating
film formed on the metal film; a topmost layer metal film formed on
the insulating film; a via for electrically connecting the metal
film and the topmost layer metal film, being absent under the pad
opening; and a protective film formed on the topmost layer metal
film, the protective film having a rectangular pad opening that
exposes a part of the topmost layer metal film.
Advantageous Effects of Invention
[0014] In the pad structure according to one embodiment of the
present invention, the metal film under the topmost layer metal
film in the pad opening exists not only on an outer side of the pad
opening but also on the inner side of the pad opening except for a
portion under the beveled corner at the tip of the capillary for
the ball bonder in ball bonding. The area of the metal film under
the topmost layer metal film in the pad opening accordingly becomes
larger, reducing the parasitic resistance to the element in the
semiconductor device without enlarging the pad structure.
[0015] Further, in the pad structure according to one embodiment of
the present invention, absence of the metal film under the topmost
layer metal film in the pad opening inside the pad opening under
the beveled corner at the tip of the capillary for the ball bonder
in ball bonding increases an effective thickness of the insulating
film formed under the pad opening that receives bonding damage
under the beveled corner. The thick insulating film absorbs the
bonding damage, thus inhibiting a crack.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 are views illustrating a pad structure of the present
invention.
[0017] FIG. 2 is a view when ball bonding to the pad structure is
performed.
[0018] FIG. 3 are views illustrating a pad structure of the present
invention.
[0019] FIG. 4 is a view when ball bonding to the pad structure is
performed.
[0020] FIG. 5 is a view illustrating a pad structure of the present
invention.
[0021] FIG. 6 is a view illustrating a pad structure of the present
invention.
[0022] FIG. 7 are views illustrating a pad structure of the present
invention.
[0023] FIG. 8 is a view illustrating a pad structure of the present
invention.
[0024] FIG. 9 is a view illustrating a pad structure of the present
invention.
[0025] FIG. 10 is a view illustrating a pad structure of the
present invention.
[0026] FIG. 11 are views illustrating bonding damage in ball
bonding.
[0027] FIG. 12 is a view illustrating a related-art pad
structure.
[0028] FIG. 13 are views illustrating a related-art pad
structure.
DESCRIPTION OF EMBODIMENT
[0029] Embodiments of the present invention are described in the
following with reference to the drawings.
[0030] First, a pad structure of a semiconductor device of the
present invention is described with reference to FIG. 1. FIG. 1(a)
is a perspective view, FIG. 1(b) is a sectional view, and FIG. 1(c)
is a plan view for illustrating a relationship between a second
metal film and a pad opening, and a topmost layer metal film 3 is
omitted in FIG. 1(c).
[0031] An element (not shown) is formed in a semiconductor
substrate 11. A first insulating film 10 is formed on the
semiconductor substrate 11, and a first metal film 1 is formed on
the first insulating film 10. The element and the first metal film
1 are electrically connected to each other through contacts 12. A
second insulating film 4 is formed on the first metal film 1, and a
second metal film 2 is formed on the second insulating film 4. The
first metal film 1 and the second metal film 2 are electrically
connected to each other through first vias 7 formed in the second
insulating film 4. A third insulating film 5 is formed on the
second metal film 2, and the topmost layer metal film 3 is formed
on the third insulating film 5. The second metal film 2 and the
topmost layer metal film 3 are electrically connected to each other
through second vias 8 that are not arranged under a pad opening 9.
A protective film 6 is formed on the topmost layer metal film
3.
[0032] The protective film 6 includes the pad opening 9 that
exposes a part of the topmost layer metal film 3. The pad opening 9
is rectangular, and further, in this case, square, having an
opening width of d0. The second metal film 2 has an opening under
the pad opening 9. This opening is also rectangular, in this case,
square, having an opening width of d4. A distance between an
opening edge of the protective film 6 and an opening edge of the
second metal film 2 is d3. The second metal film 2 has a square
donut shape, and protrudes to an inner side of the pad opening 9 by
the distance d3. The distance d3 is an amount of the protrusion of
the second metal film 2. There is a relationship among the lengths:
d0=d3.times.2+d4, or d3=(d0-d4)/2. In general, the second metal
film 2 only needs to have a donut shape. Absence of the second
metal film 2 at a place immediately below the pad opening 9 to the
topmost layer metal film 3 increases the effective thickness of the
insulating film under the pad opening 9.
[0033] As already described, FIG. 11 are views illustrating bonding
damage in ball bonding. When cracks 18 develop due to the bonding
damage, the cracks 18 do not develop under edges of a crushed ball
16 but develop under a beveled corner 13 at a tip of a capillary
for a ball bonder. Specifically, with reference to FIG. 11(b), the
cracks 18 develop so as to have a width r1 of the beveled corners
illustrated in FIG. 11(a), not a width r2 of the crushed ball
16.
[0034] As illustrated in FIG. 2, since the crushed ball 16 extends
to have the width r2, the opening width d0 of the pad opening 9 is
set to be larger than the width r2 (d0>r2). Further, the opening
width d4 of the second metal film 2 under the pad opening 9 is set
to be larger than the width r1 of the beveled corners (d4>r1).
Developed bonding damage 17 travels from the beveled corner 13 at
the tip of the capillary for the ball bonder to the topmost layer
metal film 3 in the pad opening 9. Since the second metal film 2
does not exist under the beveled corner 13 at the tip of the
capillary for the ball bonder in the ball bonding, a sum of the
thickness of the second insulating film 4 and the thickness of the
third insulating film 5 becomes the thickness of insulating films
between the first metal film 1 and the topmost layer metal film 3,
which receives the bonding damage 17.
[0035] <Effect> As described above, in the pad structure, the
second metal film 2 under the topmost layer metal film 3 in the pad
opening 9 exists not only on an outer side of the pad opening 9 but
also on the inner side of the pad opening 9 except for a portion
under the beveled corner 13 at the tip of the capillary for the
ball bonder in the ball bonding. The area of the metal film 2 under
the topmost layer metal film 3 in the pad opening 9 becomes larger
accordingly. The number of the vias between the second metal film
and the topmost layer metal film and the number of the vias between
the first metal film and the second metal film can thus be
increased without enlarging the pad structure, which reduces a
parasitic resistance to the element in the semiconductor device due
to the pad structure. Alternatively, keeping the value of the
parasitic resistance to the same value as that of the related art
by keeping the number of the vias, the respective metal films can
be reduced in size by the protrusion of the second metal film to
the inner side.
[0036] Further, in the pad structure, absence of the second metal
film 2 under the topmost layer metal film 3 in the pad opening 9
under the beveled corner 13 at the tip of the capillary for the
ball bonder in the ball bonding inside the pad opening 9 under the
beveled corner 13 increases the effective thickness of the
insulating film formed under the pad opening 9 that receives the
bonding damage 17. The thick insulating film absorbs the bonding
damage 17, inhibiting a crack.
[0037] Further, when the element under the pad opening 9 is an ESD
protection element, increase in an area of the second metal film 2
accordingly permits arrangement of a larger number of the first
vias 7 on the second metal film 2, reducing the parasitic
resistance between the pad structure and the ESD protection
element. Thus concentration of current reduces and an ESD tolerance
of the ESD protection element becomes higher.
[0038] It is noted that, in the above description, a case in which
an element such as an ESD protection element exists under the pad
opening 9 is described, the present invention is not limited
thereto. The element such as an ESD protection element may be
formed away from the pad, in which the element and the pad are
electrically connected to each other through the first metal film,
the second metal film, and the like.
[0039] Further, in the above description, the semiconductor device
is manufactured using a three-layer metal process, but the present
invention is not limited thereto. The semiconductor device may be
manufactured using a two-layer metal process.
[0040] Further, in the above description, both the pad opening 9
formed in the protective film 6 and the opening formed in the
second metal film 2 are square, but the present invention is not
limited thereto. Insofar as the relationship between the lengths
expressed by the inequality used in the description is satisfied,
the two openings may be rectangular or circular. Various kinds of
combinations are possible.
Modified Example 1
[0041] FIG. 3 illustrate another pad structure of the present
invention. FIG. 3(a) is a sectional view, and FIG. 3 (b) is a plan
view mainly for illustrating a relationship between the second
metal film and the pad opening. FIG. 4 is a view illustrating a
case in which ball bonding to the pad structure is performed.
[0042] As compared with the embodiment described above, this case
is different in that the second part of the second metal film 19 is
formed rectangular under the pad opening 9 so as not to be held in
contact with the first part of the second metal film 2 having a
rectangular donut shape and formed under the pad opening 9. It is
necessary that, as illustrated in FIG. 4, a width d5 of the second
part of the second electrode film 19 be smaller than the width r1
of the beveled corners (d5<r1).
[0043] As illustrated in FIG. 4, since the bonding damage 17
develops from the beveled corner 13 at the tip of the capillary for
the ball bonder to the topmost layer metal film 3 in the pad
opening 9, the second part of the second metal film 19 is formed so
as not to be directly below the beveled corner 13 and so as to be
completely within the width r1 of the beveled corners. Thus the
effective thickness of the insulating film formed under the pad
opening 9 that receives the bonding damage 17 remains large. The
thick insulating film absorbs the bonding damage 17, inhibiting a
crack.
[0044] It is noted that the second part of the second metal film 19
may be circular as illustrated in FIG. 5. Further, the second part
of the second metal film 19 may be a combination including a
plurality of rectangles as illustrated in FIG. 6. Further, the
second part of the second metal film 19 may be a combination
including a plurality of circles (not shown).
Modified Example 2
[0045] FIG. 7 are views illustrating a pad structure of the present
invention. FIG. 7(a) is a sectional view, and FIG. 7(b) is a plan
view mainly for illustrating a relationship between the second
metal film and the pad opening.
[0046] As compared with Modified Example 1, this case is different
in that the second part of the second metal film 19 is electrically
connected to the topmost layer metal film 3 through the second vias
8. Further, the second part of the second metal film 19 is also
electrically connected to the first metal film 1 through the first
vias 7.
[0047] In the pad structure, new contribution of the first vias 7,
the second vias 8, and the second metal film 19 to electrical
conduction reduces the parasitic resistance included in the pad
structure.
[0048] It is noted that, as illustrated in FIG. 8, similarly to
FIG. 5, the second part of the second metal film 19 may be circular
and the second vias 8 may be arranged therein. Further, as
illustrated in FIG. 9, similarly to FIG. 6, the second part of the
second metal film 19 may be a pattern including rectangles and the
second vias 8 may be arranged therein.
Modified Example 3
[0049] FIG. 10 is a view illustrating a pad structure of the
present invention.
[0050] As compared with the embodiment described above, this case
is different in that the second metal film 2 having a rectangular
donut shape, which is formed under the pad opening 9, includes a
slit 30 as illustrated in FIG. 10.
[0051] It is noted that the second metal film 2 may be U-shaped,
L-shaped, or other shape (not shown) under constraints of a layout
pattern.
REFERENCE SIGNS LIST
[0052] 1 first metal film [0053] 2 second metal film [0054] 3
topmost layer metal film [0055] 4 second insulating film [0056] 5
third insulating film [0057] 6 protective film [0058] 7 first via
[0059] 8 second via [0060] 9 pad opening [0061] 10 first insulating
film [0062] 11 semiconductor substrate [0063] 12 contact [0064] 13
beveled corner at tip of capillary for ball bonder [0065] 14
bonding wire [0066] 15 balled wire [0067] 16 crushed ball [0068] 17
bonding damage [0069] 18 crack [0070] 19 second metal film
* * * * *