Active solid-state devices (e.g. – transistors – solid-state diode – Gate arrays – With particular signal path connections
Reexamination Certificate
1998-12-28
2001-06-19
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Gate arrays
With particular signal path connections
C257S209000, C257S211000, C257S347000, C257S664000, C257S734000, C257S775000
Reexamination Certificate
active
06249013
ABSTRACT:
This application is based on Japanese patent application Hei 10-72516 filed on Mar. 20, 1998, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a microwave-millimeter wave circuit device and a method for manufacturing the same, and more particularly to a microwave-millimeter wave circuit device having a coplanar wiring and a method for manufacturing the circuit device.
b) Description of the Related Art
A monolithic microwave-millimeter wave integrated circuit device (MMIC) is known as a semiconductor IC device used in a high frequency band associated with microwaves, millimeter waves, etc. The use of a high frequency is required for transmission, reception and the like. In signal processing, however, operations at such a high frequency are not required. In view of this, the method of forming circuits which operate at a particularly high frequency on IC chips and bonding the IC chips onto a circuit board is adopted. In most cases, an MMIC is formed as such an IC chip.
The mobility of charge carriers in a semiconductor is restricted by the material of the semiconductor. Generally speaking, the mobility of carriers in a compound semiconductor like GaAs and InP is higher than that of carriers in Si. The compound semiconductor, therefore, is more suitable than Si in forming a high frequency IC.
A semiconductor element whose parasitic capacitance is small is preferred as one which operates in a high frequency band. In the case of the compound semiconductor, since a semi-insulating region can be formed therein by Cr doping, oxygen ion implantation, etc., a semiconductor element employing dielectric isolation, not pn isolation, can be provided. By adopting the chemical compound and conducting the dielectric isolation, a semiconductor device whose attendant capacitance is considerably small can be realized.
A 77 GHz radar, for example, is available as a millimeter wave circuit device. When forming the entirety of the radar on the compound semiconductor, a compound semiconductor substrate having a large area is required, because its transmission/reception antenna occupies a large area. This results in the cost of the entire device being extremely high. In order to reduce the manufacturing cost, it is preferable to form an antenna on a dielectric substrate made of an inexpensive material and to form only a circuit section, which needs to operate at a high frequency, as an MMIC made of the compound semiconductor, and to bond the MMIC onto the substrate on which the antenna has been formed.
In general, the compound semiconductor substrate has a dielectric constant of 10 or greater. Signals, transmitted through a wiring formed on the substrate with such a high dielectric constant, have a short wavelength. In the case of a frequency of 77 GHz, signals transmitted through coplanar lines, for example, have a wavelength of approximately 1.6 mm.
The geometric dimensions of a semiconductor active element formed on the compound semiconductor substrate tend to decrease as its performance is improved. A minor variation in the shape of the semiconductor element results in a considerable variation in the input/output impedance of the semiconductor active element.
When the input/output impedance of the semiconductor active element as formed differs from the design value, the dimensions of a peripheral circuit element, in particular, a matching circuit, need to be changed. Any design change will be possible if a semiconductor IC device is remanufactured from the beginning. However, the semiconductor substrate on which the semiconductor element, etc. have been formed has to be abandoned. This makes the manufacturing cost high.
In the case of a coplanar wiring, a ground conductor and a signal wiring are arranged in the same plane. The signal wiring separates the ground conductor into parts. Under this condition, it is difficult to keep the potential of the ground conductor uniform. The potential of the ground conductor is unstable especially when the ground conductor has such a width and a length that the conductor itself has impedance.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a microwave-millimeter wave circuit device having a coplanar wiring, capable of performing a stable operation while reducing the manufacturing cost.
It is another object of the present invention to provide a method for manufacturing such a microwave-millimeter wave circuit device having a coplanar wiring.
According to one aspect of the present invention, there is provided a microwave-millimeter wave circuit device comprising: a dielectric substrate having a dielectric region; a ground conductor connecting wiring and circuit elements which are formed on the dielectric substrate; a wiring electrically connected to the circuit elements and crossing over a part of the ground conductor connecting wiring on the dielectric substrate; and ground conductor patterns separated from each other by the wiring, being electrically connected to each other via a part of the ground conductor connecting wiring, and forming a coplanar wiring on the dielectric substrate, together with the wiring. At least one end of that part of the ground conductor connecting wiring via which the ground conductor patterns are electrically connected to each other is provided with an extended portion which is at least 10 &mgr;m long, in order to permit the coplanar wiring to be redesigned in compensation for variations in characteristics of the circuit elements.
By electrically connecting the ground conductor patterns to each other via the ground conductor connecting wiring, the potentials of the ground conductor patterns can be stabilized. The ground conductor connecting wiring has extra parts in addition to the required parts. The ground conductor patterns are connected to each other via the aforementioned required parts. When an unintended variation occurs in a circuit parameter, the wiring and the ground conductor patterns once formed are removed, and a new wiring and new ground conductor patterns are formed, thus redesigning the circuit device. The aforementioned extra parts have been formed long enough to electrically connect the new ground conductor patterns to each other. By virtue of the presence of the extra parts, the circuits elements once formed on the dielectric substrate, such as semiconductor elements and capacitor elements, etc. can be reused.
As described above, the ground conductor connecting wiring is formed in advance so as to be longer than required. Due to this, when any design change becomes necessary after the formation of the coplanar wiring, the coplanar wiring can be removed and a new coplanar wiring can be formed in a position different from that previously formed. Since the circuit elements formed on the substrate in advance can be reused, the manufacturing cost can be reduced.
REFERENCES:
patent: 4619001 (1986-10-01), Kane
patent: 5343176 (1994-08-01), Hasler
patent: 5654676 (1997-08-01), Avanic et al.
Armstrong, Westerman Hattori, McLeland & Naughton
Crane Sara
Fujitsu Limited
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