Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2000-09-13
2002-11-05
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S321100, C361S305000, C361S310000, C257S530000, C257S755000, C438S381000, C438S394000
Reexamination Certificate
active
06477031
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronic component for processing high frequency signals and a method for fabricating the same and, particularly, an electronic component which can be utilized in various communication devices such as portable telephones, automobile telephones and the like and a method for fabricating the same.
DESCRIPTION OF THE PRIOR ART
Conventional high frequency circuits for processing high frequency signals above 100 MHz, for example, are formed by forming a conductive layer on a substrate using a conductive paste and then patterning the conductive layer into a predetermined circuit pattern by etching, as described in, for example, Japanese Patent Application Laid Open No. 9-199365.
Japanese Patent Publication No.
35-3723
further discloses a method for forming a conductive pattern by printing a copper paste on a substrate made of resin, drying it, and plating the copper paste with copper by electroplating.
Moreover, Japanese Patent Application Laid Open No. 4-323887 discloses a method for forming a conductive pattern by forming a copper oxide film on a substrate made of ceramic, and plating the copper oxide film with copper by PVD (physical vapor deposition).
The conductive patterns obtained by the above-mentioned prior art methods have an almost trapezoidal or rectangular cross section. High frequency characteristics (Q value) of the conductive pattern having such a cross section depends on the sectional area. To increase the cross-sectional area of the conductive pattern, it is necessary to increase the thickness or width thereof In this kind of electronic component used with high frequency signals, the conductive pattern lines have to be formed with high accuracy and narrow width. Therefore, in order to increase the cross-sectional area of the conductive pattern, it is preferable to increase the thickness thereof while keeping its width narrow. However, when the thickness of the film is increased, the following various problems arise.
When an electronic component for high frequency signals is fabricated, a number of elements for the electronic component are simultaneously formed on a single wafer. In the wafer process, however, when the thickness of the conductive paste formed on the wafer is increased, the fluctuation in the thickness thereof also increases. When the thickness of the conductive layer is set more than 10 &mgr;m, 5 &mgr;m fluctuation in the thickness of the conductive layer may occur in the plane of the wafer, although the fluctuation in thickness depends on various condition of forming the conductive layer. When such a fluctuation in the thickness of the conductive paste occurs, the width of the conductive pattern made of the conductive paste becomes too narrow at the portion where the thickness of the conductive layer is relatively thin, because the conductive paste is excessively etched. On the other hand short circuiting may occur due to the remaining conductive film at portions where the thickness of the conductive layer is relatively thick, because the conductive film is etched insufficiently. Product yield decreases as a result.
Further, since the conductive layer is subjected to isotropic etching, side-etching (under-etching) of the conductive layer under a resist film formed on the conductive layer is easily occurred at portions where the thickness thereof is relatively thick, thereby making it difficult to obtain conductive pattern lines of the desired width.
The probability of the wafer warping after the conductive paste is sintered because the physical stress at the interface between the conductive layer and the wafer increases as the conductive layer becomes thicker. Such warp degrades the precision of the conductive pattern made from the conductive paste because the warp weakens the contact between a mask and the main surface of the wafer.
To solve these problems, it is required to reduce the thickness of the conductive layer to less than a certain degree. This limits the high-frequency characteristics. Particularly, it is difficult to restrain signal loss caused by the skin effect occurring in the high frequency range.
Furthermore, because of the cross section of the conductive pattern is almost rectangle or trapezoid, localization of electric current cannot be avoided. Such localization of electric current causes a localization of the high frequency magnetic field, so that a conductor loss can not be improved.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved electronic component for high frequency signals and a method for fabricating the same.
Another object of the present invention is to provide an electronic component for a high frequency signal with good high frequency characteristics and a method for fabricating the same.
Another object of the present invention is to provide an electronic component for a high frequency signals and a method for fabricating the same in which a signal loss caused by the skin effect can be lowered.
Another object of the present invention is to provide an electronic component for high frequency signals and a method for fabricating the same in which local concentration of the high frequency magnetic field can be reduced so that characteristic degradation due to local concentration of the high frequency magnetic field can be prevented.
Another object of the present invention is to provide a method for fabricating an electronic component for high frequency signals that enables improved production yield.
Another object of the present invention is to provide a method for fabricating an electronic component for high frequency signals that enables improved production yield by preventing over-etching and short-etching.
Another object of the present invention is to provide a method for fabricating an electronic component for high frequency signals that improves contact between a mask and a main surface of a wafer and thus improves accuracy of the conductive pattern.
The above and other objects of the present invention can be accomplished by an electronic component for high frequency signals comprising an insulating substrate and a conductive pattern formed on the insulating substrate, the conductive pattern having a dual structure including a first element and a second element, the second element of the conductive pattern covering the first element of the conductive pattern substantially entirely.
According to the present invention, the cross-sectional area of the conductive pattern can be increased easily because the conductive pattern has a dual structure. Therefore, an electronic component having good high frequency characteristics can be obtained.
In a preferred aspect of the present invention, the first element of the conductive pattern has a side wall and the second element of the conductive pattern has a dilated portion expanded outward from the side wall of the first element.
According to this preferred aspect of the present invention, because second element of the conductive pattern has the dilated portion, signal loss caused by the skin effect can be reduced, thereby improving the high frequency characteristic.
In a further preferred aspect of the present invention, the dilated portion is approximately arc-shaped.
According to this preferred aspect of the present invention, signal loss caused by the skin effect can be more effectively reduced.
In a further preferred aspect of the present invention, the first element of the conductive pattern has a contact portion contacting with the insulating substrate, an edge of the contact portion of the first element and an edge of the dilated portion of the second element being substantially coincident.
According to this preferred aspect of the present invention, even if over-etching or side-etching of first element occurs, the over-etched portion or the side-etched portion of first element can be effectively repaired. Moreover, signal loss caused by the skin effect can be more effectively reduced. Furthermore, local concentration of the high frequency magnetic fi
Dinkins Anthony
Fulwider Patton Lee & Utecht LLP
Ha Nguyen T
TDK Corporation
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