Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For high frequency device
Reexamination Certificate
1999-03-08
2001-05-15
Tran, Minh Loan (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For high frequency device
C257S691000, C257S778000, C257S773000, C257S780000, C257S774000
Reexamination Certificate
active
06232660
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high-frequency semiconductor devices used in the range of high-frequency waves such as microwave and millimetric wave, and particularly to a high-frequency semiconductor device having a superior high-frequency characteristic.
2. Description of the Background Art
As the processing speed of information processors improves and the resolution of image processing devices is enhanced, high-speed and large-capacity personal communication in the high-frequency range such as the millimetric wave band of 30 G-300 GHz, or the centimetric wave band and submillimetric wave band of frequencies higher or lower than that is attracting attention recently. In such communication, not only making use of the high-frequency characteristic but development of a high-frequency package with small size, low cost, and short development period is required.
Generally, the high-frequency package often requires sealing in terms of three aspects, that is, electromagnetic wave, hermetic concern, and mechanical concern. In terms of the mechanical aspect, the reason for sealing is similar to that of the ordinary semiconductor package. In terms of the hermetic aspect, the reason for sealing is that variation of moisture and temperature often influences the high-frequency characteristic of the high-frequency semiconductor chip.
With regard to the sealing in terms of electromagnetic wave, in a high-frequency package for frequencies in the millimetric wave band and the band of frequencies higher and lower than that, the factor which is negligible in the high-frequency package of the mobile telephone or PHS (Personal Handy-phone System) with relatively lower frequency in the millimetric wave band is important in designing the high-frequency semiconductor device. Specifically, in the range of the millimetric wave band, the wavelength is 1-10 mm in the atmosphere, and the effective wavelength is approximately from 100 microns to several millimeters considering the dielectric constant of the material constituting the package. This length corresponds to the size of the high-frequency semiconductor chip, package or high-frequency circuit, so that the three-dimensional shape thereof as well as the material characteristics such as the dielectric constant and the dielectric loss have a significant influence on the high-frequency characteristic of the high-frequency package. In view of this, the design of the three-dimensional shape in the package becomes an important factor.
FIG. 1
shows a cross section of a conventional high-frequency package as the first example. The high-frequency package includes an interconnection substrate
10
, a high-frequency semiconductor chip
30
where a high-frequency circuit
32
is formed, a plurality of bumps
40
, and a cap
50
. On interconnection substrate
10
, high-frequency semiconductor chip
30
is connected by chip-bonding. Bumps
40
of high-frequency semiconductor chip
30
include signal bumps for input, output, power supply, bias and the like as well as several ground bumps. These bumps are used only for connection of high-frequency semiconductor chip
30
. Cap
50
is formed of metal, for example, in order to provide not only hermetic and mechanical sealing but sealing in terms of electromagnetic wave.
FIG. 2
shows a cross section of a conventional high-frequency package as the second example. The high-frequency package is the invention disclosed in Japanese Patent Laying-Open No. 4-79255. The difference between the invention and the conventional art shown in
FIG. 1
is that an electromagnetic wave absorption block
70
is provided within a cap
50
for absorbing electromagnetic waves emitted from a gap between a high-frequency semiconductor chip
30
and an interconnection substrate
10
to prevent unnecessary interference and reflection.
FIG. 3
shows a cross section of a conventional high-frequency package as the third example. The difference between this package and the conventional art shown in
FIG. 1
is that a plurality of high-frequency semiconductor chips
30
a
and
30
b
are provided inside a package formed of an interconnection substrate
10
and a cap
50
in order to provide the high-frequency semiconductor with multifunction or an improved high-frequency characteristic.
FIGS. 4A and 4B
respectively illustrate a cross section of a conventional high-frequency package as the fourth example and a manufacturing procedure thereof. The high-frequency package includes an interconnection substrate
10
, separate packages
52
a
and
52
b
, and a guard cap
56
. As shown in
FIG. 4B
, high-frequency semiconductor chips
30
a
and
30
b
are respectively housed in separate packages
52
a
and
52
b
, and separate packages
52
a
and
52
b
are reversed to be placed in package insert holes
28
of interconnection substrate
10
. In the high-frequency package accordingly produced, a high-frequency signal line
58
at separate package
52
b
and a high-frequency signal line
59
at interconnection substrate
10
are connected, and the exposed portion of high-frequency signal line
59
at interconnection substrate
10
is covered with guard cap
56
as shown in FIG.
4
A.
Regarding the conventional art illustrated in
FIG. 1
, bumps
40
connected to the periphery of high-frequency semiconductor chip
30
are used for electrical connection of high-frequency semiconductor chip
30
only. Therefore, electromagnetic waves emitted from chip high-frequency circuit
32
inside high-frequency semiconductor chip
30
leak from the gap between high-frequency semiconductor chip
30
and interconnection substrate
10
. This leakage causes reflection and interference of the electromagnetic waves on the inner surface of cap
50
formed of metal, increase of noise level, generation of ripple and the like, leading to difficulty in implementation of a high performance high-frequency package having a superior characteristic such as low noise and wideband.
Regarding the second conventional art illustrated in
FIG. 2
, electromagnetic wave absorption block
70
having an appropriate shape is arranged at any suitable location in order to prevent deterioration of the high-frequency characteristic caused by the electromagnetic waves leaking from the gap between high-frequency semiconductor chip
30
and interconnection substrate
10
. However, design of the shape and arrangement of electromagnetic wave absorption block
70
is difficult, and a series of processes of simulation, trial manufacture, and measurement evaluation should be repeatedly carried out for optimization. Consequently, the development period increases and the design cost becomes enormous. Further, a high-frequency package housing a high-frequency semiconductor chip having various functions, various sizes, and various ways of emission of the electromagnetic waves in order to meet the needs for various types of products is required, and corresponding design should be made individually. Generally, it is desirable to proceed development and design of a high-frequency package while a high-frequency semiconductor chip is developed and designed. However, manufacturing of the high-frequency package as a trial for measurement evaluation of electromagnetic wave emission is impossible unless the high-frequency semiconductor chip is available. In addition, if the number of chips obtained from a wafer is increased to reduce the cost and accordingly the size of the chip itself is reduced, or if one chip and one package are realized by assembling different chips and different packages, the chip size and the interconnection substrate should be changed. A problem in this case is that the three dimensional shape of the package should be designed again.
Regarding the third conventional art illustrated in
FIG. 3
, electromagnetic waves leak from the gap between high-frequency semiconductor chip
30
a
or
30
b
and interconnection substrate
10
, and the electromagnetic wave from high-frequency semiconductor chip
30
a
and the electromagnetic wave from high-f
Kakimoto Noriko
Suematsu Eiji
Sharp Kabushiki Kaisha
Thai Luan
Tran Minh Loan
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