Semiconductor device manufacturing: process – Semiconductor substrate dicing – With attachment to temporary support or carrier
Reexamination Certificate
1999-07-20
2001-10-02
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Semiconductor substrate dicing
With attachment to temporary support or carrier
C438S118000
Reexamination Certificate
active
06297131
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for manufacturing a semiconductor device and, more particularly, to a method for grinding and dicing a large-diameter wafer to produce a semiconductor device having a reduced thickness.
In a manufacturing process of a semiconductor device, a wafer on which circuit patterns are formed is subjected to a grinding process so as to reduce a thickness of the wafer. The grinding is applied to a surface (back surface) on which no circuit pattern is formed.
In recent years, large-diameter wafers have been used to improve productivity of semiconductor devices. Additionally, since semiconductor devices having a small thickness have been required for use in an IC card, it is required to reduce a thickness of a wafer. Further, use of a wafer having bumps, which bumps are formed before the wafer is subjected to dicing, has been increased. However, an increase in a diameter of the wafer, reduction in a thickness of the wafer and the wafer having bumps may increase a possibility of wafer cracking during a manufacturing process.
For example, when a large-diameter wafer is ground, a thickness of the wafer is limited to about 200 &mgr;m. That is, if the wafer is ground to a thickness of less than 200 &mgr;m, the wafer may frequently crack during the grinding process and a handling process.
Additionally, in the wafer having bumps, a possibility of wafer cracking during the grinding process is increased since the bumps act as protrusions.
Accordingly, it is desired to establish a technique for grinding and dicing a large-diameter wafer at a high throughput without damaging the wafer.
2. Description of the Related Art
A description will now be given, with reference to
FIGS. 1
to
6
, of a conventional manufacturing method of a semiconductor device. The manufacturing method of a semiconductor device includes a grinding process and a dicing process. In the grinding process, grinding (referred to as back grinding) is applied to a back surface of a wafer so that a thickness of the wafer is reduced to a predetermined thickness. In the dicing process, dicing is applied to the wafer so that the wafer is divided into a plurality of individual semiconductor chips.
FIG. 1
is a flowchart of a conventional manufacturing method of a semiconductor device in which method a dicing process and a grinding process are performed. The conventional method shown in
FIG. 1
comprises the steps of: applying a protective tape to a wafer having a front surface on which circuits are formed (step S
10
); grinding a back surface of the wafer (step S
20
); applying a dicing tape to the wafer after turning over the wafer (step S
14
); and dicing the wafer from the side of the front surface (step S
16
).
FIG. 2
is an illustration for explaining the protective tape applying process (step S
10
) shown in FIG.
1
.
FIG. 3
is an illustration for explaining the grinding process (step S
12
) shown in FIG.
1
.
FIG. 4
is an illustration for explaining the dicing tape applying process (step S
14
) shown in FIG.
1
.
FIG. 5
is an illustration for explaining the dicing process (step S
16
) shown in FIG.
1
.
Semiconductor circuits are previously formed on a front surface of a wafer
10
to be ground. First, as shown in
FIG. 2
, a protective tape
12
is applied to the front surface of the wafer
10
so as to protect the semiconductor circuits formed on the front surface of the wafer
10
. Then, the wafer
10
is fixed by suction on a vacuum chuck table via the protective tape
12
. The protective tape
12
is formed of a resin, and an ultraviolet cure pressure-sensitive adhesive is applied to a surface thereof. The wafer
10
is ground in a state in which the wafer
10
is fixed on the vacuum chuck table via the protective tape
12
.
In the grinding process, the back surface of the wafer
10
is ground by using a grinding tool
18
as shown in
FIG. 3
so as to reduce a thickness of the wafer
10
to a predetermined thickness. Specifically, the grinding is performed by moving the rotating grinding tool
18
in directions indicated by arrows X
1
and X
2
while supplying a grinding liquid. Thereby, the wafer
10
having the predetermined thickness is formed.
After the grinding process is completed, the wafer
10
is removed from the protective tape
12
. Then, the wafer
10
is applied to a dicing tape
20
which is spread on a wafer frame
14
so that the front surface of the wafer
10
on which front surface the circuits are formed faces upwardly as shown in FIG.
4
. The dicing tape
20
is formed of a resin, and the pressure-sensitive adhesive is applied to a surface of the dicing tape
20
. The wafer
10
is diced in a state in which the wafer
10
is secured on the dicing tape
20
by the pressure-sensitive adhesive.
In the dicing process, the wafer
10
is diced by using a dicing saw
22
as shown in FIG.
5
. The dicing is performed while monitoring an image of a scribe line formed on the front surface of the wafer
10
. Thereby, the wafer
10
is divided into a plurality of semiconductor chips
11
.
According to the above-mentioned conventional method, a pressing force is applied to a part of the wafer
10
by the grinding tool
18
since the grinding process is performed prior to the dicing process. When the thickness of the wafer
10
is reduced to less than 200 &mgr;m by grinding, the strength of the wafer
10
is reduced. Accordingly, the wafer may crack during the grinding process. Particularly, when the thickness of the wafer
10
is reduced to 50 &mgr;m by grinding, there is a problem in that wafer cracks may frequently occur. Additionally, when the wafer
10
is provided with bumps, the bumps may act as protrusions and the grinding is performed in a state in which the wafer
10
is placed on the protrusions. Thus, a possibility of occurrence of cracking in the wafer
10
is further increased.
Additionally, in the above-mentioned conventional method, after the wafer
10
is ground to the predetermined thickness, the protective tape
12
is removed and the wafer
10
is turned over. That is, the back surface of the wafer
10
faces upwardly when the grinding process is completed. Accordingly, in order to perform the dicing from the side of the front surface, the wafer
10
is applied on the dicing tape
20
with the front surface of the wafer
10
facing upwardly.
However, since the thickness of the wafer
10
is reduced by grinding, the wafer
10
warps as shown in
FIG. 6
after the protective tape
12
is removed. A degree of warpage of the wafer
10
can be represented by a maximum distance (indicated by an arrow H in
FIG. 6
) between the dicing tape
20
and the wafer
10
. If a 6-inch wafer is ground to a thickness of 200 &mgr;m, a warpage of about 2 cm (H=2 cm) is generated. Additionally, if an 8-inch wafer is ground to a thickness of 200 &mgr;m, a warpage of about 3 cm (H=3 cm) is generated.
If a warpage is generated in the wafer
10
as mentioned above, there is a problem in that the wafer
10
cannot be properly handled. In a worst case, the wafer may crack during the handling.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful method for manufacturing a semiconductor device in which method the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a method for manufacturing a semiconductor device which method can increase a yield rate and a throughput of the semiconductor device when a large-diameter wafer having a reduced thickness is used to produce the semiconductor device.
In order to achieve the above-mentioned objects, there is provided according to the present invention a method for manufacturing a semiconductor device by using a wafer having a front surface on which circuits are formed and a back surface opposite to the front surface, the method comprising the steps of:
applying a protective tape to the front surface of the wafer;
mounting the wafer to a dicing tape via the
Muramoto Takanori
Yamada Yutaka
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Nelms David
Vu David
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