Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
2001-05-02
2004-04-13
Graybill, David E. (Department: 2827)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S115000, C438S116000, C438S460000, C438S465000, C257S414000, C257S430000
Reexamination Certificate
active
06720206
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing semiconductor device packages, and more particularly to a method for manufacturing digital micro-mirror device (DMD) packages.
2. Description of the Related Arts
In order to keep pace with the development of personal computers, a display has been developed from a cathode-ray tube type display into a liquid crystal display or a mirror type display. Especially, with the increasing demand for digital broadcasting appliances, a digital light processing (DLP) technology for high resolution becomes more and more important. A DMD, which is an essential component for the DLP technology, requires significant expertise in the manufacturing process for mirrors so that high reliability and low cost in the manufacturing process can be obtained.
The DMD process involves driving the mirrors, and thus the proper driving of mirrors is very important. Further, moisture and dust within the packages affect the picture quality or resolution of the DMD as well as its reliability or durability. Therefore, during the fabrication of the DMD packages, the DMD packages themselves need to be protected from moisture and dust.
FIG. 1
is a plan view showing a conventional semiconductor chip
12
for the DMD, and
FIG. 2
is a cross-sectional view showing a DMD package
100
containing the semiconductor chip
12
of FIG.
1
. With reference to FIG.
1
and
FIG. 2
, the semiconductor chip
12
is attached to an upper surface
21
of a base substrate
20
by interposing an Ag-epoxy adhesive
30
therebetween. The semiconductor chip
12
and the base substrate
20
are electrically interconnected to each other with one or more bonding wires
40
. In order to protect the semiconductor chip
12
from external environmental stresses, a metal sealing ring
24
with a predetermined height is provided at the periphery of the upper surface
21
of the base substrate
20
.
The components, including the semiconductor chip
12
, are hermetically sealed up with a window lid
50
. A heat sink stud
60
is attached to the lower surface
23
of the base substrate
20
. The window lid
50
comprises a metal lid frame
52
contacting the metal sealing ring
24
, and a window
54
. A reflectance coating film
56
is applied to the lower surface of the window
54
along the periphery thereof. The metal sealing ring
24
and the base substrate
20
form a cavity
29
, and a moisture getter (absorbent)
58
is attached to the lower surface of the metal lid frame
52
of the window lid
50
within the cavity
29
. External terminals (not shown) are formed on the lower surface
23
of the base substrate
20
.
A plurality of mirrors
16
(only a typical one of which is depicted in
FIG. 2
) are formed on the active surface of the semiconductor chip
12
at the center thereof, and one or more electrode pads
14
are formed on the active surface at the periphery thereof for interconnection via the one or more bonding wires
40
.
FIG. 3
is a flow chart
90
describing a manufacturing process of the conventional DMD package
100
. Each step of the manufacturing process is described briefly below.
A wafer comprising a plurality of the semiconductor chips
12
is prepared (step
71
). Herein, a photoresist film is formed on the upper surface of the wafer in the predetermined portion. The photoresist film prevents damage to the mirrors
16
from the external environment by covering the mirrors
16
. The photoresist film is not formed on the electrode pads
14
.
Prior to wafer-breaking, the wafer is half-cut (step
72
). The photoresist film on the upper surface of the wafer is removed (step
73
), and to shield the mirrors
16
from dust or moisture, a first anti-sticking film is formed thereon (step
74
). The wafer is broken and separated into individual semiconductor chips
12
(step
75
). A breaking means in a dome shape is brought into contact with to the back surface of the wafer and urged upwardly. As a result, the half-cut wafer is broken into a plurality of individual semiconductor chips
12
.
The silicon particles generated during the wafer-breaking step are then removed (step
76
).
The semiconductor chip
12
is attached to the upper surface
21
of the base substrate
20
by the Ag-epoxy adhesive
30
(step
77
), and the Ag-epoxy adhesive
30
is cured (step
78
). The semiconductor chip
12
is electrically interconnected to the base substrate
20
with the bonding wires
40
(step
79
).
The organic compounds remaining on the upper surface
21
of the base substrate
20
, the semiconductor chip
12
on the surface
21
, and the bonding wires
40
are removed (step
80
). A second anti-sticking film is formed thereon (step
81
).
The metal sealing ring
24
is mounted on the upper surface
21
of the base substrate
20
, and the components are hermetically sealed by the window lid
50
having the moisture getter
58
attached thereon (step
82
).
The heat sink stud
60
is attached to the lower surface
23
of the base substrate
20
(step
83
). The DMD package
100
is thus complete.
The above-described method for manufacturing the conventional DMD packages has several problems as follows;
The manufacturing process is very complicated. The major reason is that the manufacturing process for the conventional DMD package employs the wafer-breaking method for separating the wafer into individual semiconductor chips
12
. Since the wafer-breaking method comprises a first step of half-cutting the wafer and a second step of breaking the wafer, compared to the full-cutting method, which completely cuts the wafer at once, this method further involves an additional step, i.e. the wafer-breaking step.
Even if the fall-cutting method is employed to prevent this drawback, another problem occurs in the step of removing the photoresist after separating the wafer into the semiconductor chips by the full-cutting method. Conventionally, the wafer comprising separated semiconductor chips has the adhesive tape on its back surface. In the photoresist-removing step after the wafer-cutting step, the adhesive from the adhesive tape and the photoresist are unnecessarily removed together. Thus, the individual semiconductor chips can be undesirably detached from the adhesive tape. Therefore, the conventional manufacturing process normally cannot employ the fall-cutting method.
The mirrors within the semiconductor chip
12
can be easily damaged by the silicon particles generated in the wafer-breaking step. The silicon particles positioned between the mirrors
16
cannot be properly removed by the washing step. Since the wafer-breaking step is carried out after the step of removing the photoresist, damage to the mirrors
16
by the silicon particles commonly occurs.
Since the Ag-epoxy adhesive is used to attach the semiconductor chip
12
to the base substrate
20
, moisture enters the package due to the hygroscopicity of the Ag-epoxy. Further, an exhaust gas generated during the curing of the Ag-epoxy adhesive contaminates the mirrors
16
on the active surface of the semiconductor chip
12
. Therefore, it is preferable to use solder as the adhesive means. However, with the use of the solder, damage such as the burning of the first anti-sticking film or the deformation of the mirrors can occur. In other words, to attach the semiconductor chip to the base substrate, the solder must be melted at a temperature of 150° C. or more. Such a high temperature causes the burning of the first anti-sticking film or the deformation of the mirrors
16
in the semiconductor chip
12
.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to simplify the manufacturing process of the DMD packages.
Another object of the present invention is to prevent failures generated in the sequence of steps including first half-cutting and second full-cutting the wafer.
Still another object of the present invention is to prevent failures due to the use of the Ag-epoxy adhesive.
In order to achieve the foregoing and other objects, a method for
Graybill David E.
Marger & Johnson & McCollom, P.C.
Mitchell James M.
Samsung Electronics Co,. Ltd.
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