Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2001-11-05
2003-04-22
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
Reexamination Certificate
active
06552365
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric converting semiconductor device and, more specifically, to a photoelectric converting semiconductor device in which impedance variation is suppressed when the photoelectric converting semiconductor element is mounted on a board.
2. Description of the Background Art
A conventional photoelectric converting semiconductor device will be described. As can be seen from
FIG. 16
, a photoelectric converting semiconductor device includes a photoelectric converting semiconductor element
101
, a coplanar waveguide board
102
(hereinafter referred to as “coplanar board”) for feeding a modulation signal voltage (hereinafter referred to as “RF signal”) to photoelectric converting semiconductor element
101
, a terminal resistance
103
for impedance matching and a coupling optical system for input/output (not shown).
On coplanar board
102
, a signal line
104
and a ground line
105
are formed. Photoelectric converting semiconductor element
101
is electrically connected to signal line
104
through a bump electrode
106
a
, and electrically connected to ground line
105
through bump electrodes
106
b
to
106
d
. Signal line
104
and ground line
105
are electrically connected through a terminal resistance
103
.
An operation of the photoelectric converting semiconductor device will be described. When the photoelectric converting semiconductor element
101
is an electric field absorbing type semiconductor optical modulator element (hereinafter referred to as “optical modulator element”), a continuous laser beam is introduced with high efficiency from the incident side coupling optical system to the optical modulator element.
In the optical modulator element, the amount of laser beam absorption changes in accordance with the voltage applied through coplanar board
102
. Therefore, by applying a modulation signal voltage to coplanar board
102
, the laser beam emitted from the optical modulator element has its intensity modulated corresponding to the signal voltage, and thus, it is coupled with high efficiency to the emitting side coupling optical system. The conventional photoelectric converting semiconductor device is structured and operates in this manner.
The conventional photoelectric converting semiconductor device, however, has the following problem. First, in the photoelectric converting semiconductor device, in order to have the impedance of the RF signal feeding side (feeding side impedance) matched with characteristic impedance of coplanar board
102
, the width of signal line
104
and the distance between signal line
104
and ground line
105
on coplanar board
102
are set to a prescribed width and a prescribed distance.
Here, the width of the signal line
104
and the distance between signal line
104
and the ground line
105
are designed such that the characteristic impedance matches the feeding side impedance with the coplanar board
102
being in a single body state, that is, when photoelectric converting semiconductor element
101
is not yet mounted on coplanar board
102
.
Therefore, when photoelectric converting semiconductor element
101
is mounted on coplanar board
102
, the characteristic impedance tends to deviate from the value of the feeding side impedance, degrading electrical characteristic of the photoelectric converting semiconductor device.
SUMMARY OF THE INVENTION
The present invention was to made to solve the above described problem, and its object is to provide a photoelectric converting semiconductor device of which variation of characteristic impedance is suppressed when the photoelectric converting semiconductor element is mounted on a coplanar board.
According to the present invention, the photoelectric converting semiconductor device has a board, a signal line, a ground line, a resistance portion and a photoelectric converting semiconductor element. The signal line is formed on and extends over the board. The ground line is formed on the board and extends spaced apart from the signal line. The resistance portion is formed on the board and electrically connects the signal line and the ground line. The photoelectric converting semiconductor element is mounted on the board to cover the signal line and the ground line, electrically connected to the signal line and the ground line to receive a modulation signal transmitted from a power feeding portion for transmitting the modulation signal, and modulates and outputs the received light. The impedance is substantially the same as the impedance of the power feed portion. In order to suppress impedance variation when the photoelectric converting semiconductor element is mounted on the board, an arrangement relation between the signal line and the ground line positioned in an area where the photoelectric converting semiconductor element is mounted is made different from the arrangement relation between the signal line and the ground line positioned in an area where the photoelectric converting semiconductor element is not mounted.
According to this structure, the arrangement relation between the signal line and the ground line positioned in the area where the photoelectric converting semiconductor element is mounted is made different from the arrangement relation between the signal line and the ground line positioned in an area where the photoelectric converting semiconductor element is not mounted, and therefore, variation of the impedance is suppressed when the photoelectric converting semiconductor element is mounted on the board, and the impedance can be set to a value substantially the same as the impedance of the power feed portion. As a result, degradation of electric characteristic of the photoelectric converting semiconductor device can be prevented.
More specifically, the signal line and the ground line positioned in an area where the photoelectric converting element is not mounted extend spaced by a first distance from each other, and the signal line and the ground line positioned in an area where the photoelectric converting semiconductor element is mounted extend spaced by a second distance, which is wider than the first distance.
When the photoelectric converting semiconductor element is brought close to the board, correlation between the characteristic impedance and the distance between the signal line and the ground line shifts from that of the board alone. Here, when the distance between the signal line and the ground line positioned in the area where the photoelectric converting semiconductor element is mounted is made to a second distance wider than the first distance, characteristic impedance variation when the photoelectric converting semiconductor element is mounted on the board can be suppressed, and the value of the characteristic impedance can be set to substantially the same value as the feeding side impedance.
More specifically, the signal line positioned in the area where the photoelectric converting semiconductor element is mounted should preferably have a prescribed width narrower than the width of the signal line positioned in the area where the photoelectric converting semiconductor element is not mounted.
Thus, in the area where the photoelectric converting semiconductor element is mounted, the distance between the signal line and the ground line is substantially made wider than the distance in the area where the photoelectric converting semiconductor element is not mounted. Thus, characteristic impedance variation when the photoelectric converting semiconductor element is mounted on the board can be suppressed, and the value of the characteristic impedance can be set to a value substantially the same as the feeding side impedance.
More specifically, the semiconductor device further includes an additional ground line positioned along the direction of extension of the signal line on the side opposite to the ground line and electrically connected to the ground line, and the distance between the ground line and the additional ground line positioned in the area whe
Gebremariam Samuel A
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
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