Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
2002-06-14
2004-08-17
Elms, Richard (Department: 2824)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S657000, C257S777000, C257S781000, C257S782000, C257S783000
Reexamination Certificate
active
06777814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, and particularly to a semiconductor device in which a semiconductor chip and a substrate are bonded together through a connection conductor by means of ultrasonic thermal compression bonding.
2. Background Art
Conventionally, when mounting a SAW (Surface Acoustic Wave) device, etc., Au bumps are formed on electrode pads on the device, and bonded to Au-plated terminal electrodes on a mounting substrate by means of thermal compression bonding and application of ultrasonic waves, which is referred to as “FCB”. The SAW device has a size of 3 mm×3 mm or smaller with a few I/O electrodes. Accordingly, it employs only a few bumps.
When applying ultrasonic thermal compression bonding to a large-size multipin device such as a memory device, on the other hand, nonconductive resin must be injected between the chip and the mounting substrate to enhance the reliability.
FIG. 10
includes schematic cross-sectional views sequentially showing process steps constituting a method for bonding a large-size multipin device and a circuit substrate together by the use of ultrasonic thermal compression bonding. First of all, connection conductors (bumps)
104
are formed on electrode pads
102
on a semiconductor chip
101
by the use of a wire bonding technique. Next, as shown in
FIG. 10A
, the semiconductor chip
101
is held by a holding tool such that the electrode pads
102
on the semiconductor chip
101
are aligned with terminal electrodes
106
on a circuit substrate
105
.
Then, a load is imposed on the semiconductor chip
101
in such a way that the connection conductors
104
come into close contact with the terminal electrodes
106
. In this state, ultrasonic vibration is applied to the semiconductor chip
101
to bond the connection conductors
104
and the terminal electrodes
106
together.
After that, as shown in
FIG. 10B
, nonconductive resin
107
is injected between the semiconductor chip
101
and the circuit substrate
105
.
FIG. 10C
shows a state in which the nonconductive resin
107
has filled the space between the semiconductor chip
101
and the circuit substrate
105
, indicating completion of the injection.
Since the applied ultrasonic vibration is attenuated after the resin has been injected, it is necessary to mount and bond the semiconductor chip
101
by means of ultrasonic thermal compression bonding before injecting the resin, as shown in FIG.
10
.
If ultrasonic thermal compression bonding is applied to a large-size multipin memory device, however, the nonconductive resin cannot reach the center portion of the semiconductor chip
101
leaving the center portion unfilled as a void, since the area of the semiconductor chip
101
is too large. Therefore, conventionally, the resin sealing as shown in
FIG. 10
has been difficult to accomplish after the compression bonding. Furthermore, the resin sealing after the compression bonding complicates the process.
To solve the above problems, a method has been adopted in which the nonconductive resin is spread over the circuit substrate beforehand, and the resin sealing is carried out at the same time with the bonding of the connection conductors
104
to the terminal electrodes
106
. This method can omit the resin injection process after the ultrasonic thermal compression bonding.
To successfully apply this method, however, the viscosity of the resin at the time of the bonding is important. Specifically, a conventional problem occurs when the nonconductive resin is melted to seal the space between the semiconductor chip and the circuit substrate in the ultrasonic thermal compression bonding. Since the viscosity of the nonconductive resin is not uniform and differs from one area to another, the ultrasonic vibration is attenuated, resulting in insufficient bonding.
The temperature of the semiconductor chip is different from that of the circuit substrate before the semiconductor chip comes into contact with the circuit substrate, that is, before the semiconductor chip is contacted with the nonconductive resin on the circuit substrate. Because of this temperature difference, the temperature of the nonconductive resin is not uniform after the semiconductor chip
1
is brought into contact with the nonconductive resin. Furthermore, the heat conductivity of the semiconductor chip is also different from that of the circuit substrate, and each portion of the semiconductor chip and the circuit substrate includes a different component, also causing the nonconductive resin
7
not to be uniform.
Especially, consider the use of a glass epoxy substrate as the circuit substrate (a glass epoxy substrate uses epoxy resin, which is nonconductive). Its terminal electrodes are made of conductive materials and the other portions are made of nonconductive materials. Therefore, the temperature of the neighborhoods of the terminal electrodes is different from the temperature of the portions surrounding the neighborhoods due to the difference between the heat capacities of those materials. This nonuniform temperature distribution leads to a nonuniform viscosity distribution of the nonconductive resin. Since ultrasonic vibration does not propagate as well in the high-viscosity portion as in the low-viscosity portion due to the drag of the nonconductive resin, the applied ultrasonic vibration is attenuated after it is affected by the high-viscosity portion, resulting in insufficient bonding of the connection conductors to the terminal electrodes.
Furthermore, the glass epoxy substrate is made of materials which have a heat conductivity relatively lower than that of metals. Therefore, in the semiconductor chip
1
, the temperature of its center is considerably different from that of its edges in the plane direction (the horizontal direction in the figure), producing a significantly-varying temperature distribution. As a result, the applied ultrasonic vibration and load are affected by the drag of the low-temperature, that is, high-viscosity portion of the nonconductive resin.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been made, and it is an object of the present invention to reliably carry out ultrasonic thermal compression bonding when mounting a large-size semiconductor device to enhance the reliability of the semiconductor device.
According to one aspect of the present invention, a semiconductor device comprises a semiconductor chip, an electronic component, electrodes, nonconductive resin, and a conductive dummy pattern. The electronic component is disposed such that the electronic component faces the semiconductor chip. The electronic component is electrically connected to the semiconductor chip through a connection conductor. The electrodes are each formed on a surface of the semiconductor chip and a surface of the electronic component. The electrodes has the connection conductor connected the electrodes. The surface of the semiconductor chip and the surface of the electronic component faces each other. The nonconductive resin is formed such that the nonconductive resin fills a space between the facing surfaces. The conductive dummy pattern is formed on the facing surface of the semiconductor chip or the electronic component.
Since a conductive dummy pattern is formed on a surface of a semiconductor chip facing an electronic component or a surface of an electronic component facing a semiconductor device, it is possible to make uniform the temperature distribution between the facing surfaces when the semiconductor chip and the electronic component are bonded together by means of ultrasonic thermal compression bonding, making the viscosity of the nonconductive resin uniform. With this arrangement, it is possible to reduce attenuation of the applied ultrasonic waves and thereby enhance the reliability of the electrical connection between the semiconductor chip and the electronic component.
Other and further objects, features and advantages of the invention will appear more fully from the follo
Hatanaka Yasumichi
Iwasaki Toshihiro
Kimura Michitaka
Wakamiya Keiichiro
Elms Richard
McDermott Will & Emery LLP
Menz Douglas
Renesas Technology Corp.
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