Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
1999-03-22
2001-12-11
Williams, Alexander O (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S703000, C257S532000, C257S528000, C257S531000, C257S741000, C257S723000, C257S666000, C257S728000
Reexamination Certificate
active
06329715
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a passive electronic part, and IC part that includes this passive electronic part, and a wafer used for obtaining the passive electronic part. The passive electronic part and the IC part according to the present invention are ideal to be employed as surface mounting high frequency parts utilized in application areas such as radio devices including cellular phones, car phones and the like, and various other types of communication devices.
BACKGROUND ART
IC parts used in the high frequency circuit portion of a cellular phone or the like in the known art include MMICs (monolithic microwave integrated circuits), which are described in “UHF Band High Efficiency FET Amplifier for Mobile Communications” published in Mitsubishi Electric Technical Report, Vol. 67, No. 11, 1993. The MMICs in the known art include three types.
The first type of MMIC is formed by constituting the active circuit portion comprising a plurality of active elements in the form of an IC chip and by forming the circuit portion constituted of a passive element on the surface of the IC chip package through thick film printing or the like. With the first type, since the passive circuit which only occupies the pattern area, is separated from the GaAs (gallium—arsenic) substrate and only the active circuit constituted of active elements such as transistors can be formed on the GaAs substrate which can be miniaturized, thereby achieving a reduction in the production cost of the IC part as a whole.
Next, with the second type of MMIC, the passive circuit portion constituted of passive elements such as filter portions is integrated on the IC chip substrate constituted of active elements into a single chip. With the second type, by forming the passive circuit portion on the GaAs substrate where the active circuit constituted of active elements such as a plurality of transistors is formed, the passive circuit and the active circuit can be manufactured at the same time through the same process, thereby achieving an extremely high degree of mass productivity. Moreover, from the viewpoint of manufacturers of semiconductor parts, the second type provides potential for achieving a reduction in the cost of the entire IC part since it does not require any ceramic chip carrier, which normally must be purchased.
The third type of MMIC is constituted by forming the passive circuit portion and the active circuit portion on separate IC substrates although these IC substrates are of the same type. Normally, in a high frequency band exceeding several GHz to several tens of GHz, the active circuit portion is formed by using a compound semiconductor constituted of GaAs or the like. Furthermore, a GaAs substrate, with its specific resistance at 10
8
&OHgr;cm or more, provides superior insulation compared to Si, whose specific resistance is approximately 2.3×10
5
&OHgr;cm. Thus, a great deal of interest is focused on the advantage that a passive element such as a coil that can be used in the high frequency band may be formed on a GaAs substrate, and currently, development of high frequency MMIC circuits by employing a GaAs substrate is underway.
With the third type, since the active circuit portion and the passive circuit portion can be manufactured through the same process and the passive circuit portion is provided on a separate chip, it is possible to limit the portion that requires changes in design (impedance, etc.) in correspondence to the frequency band that is used. Because of this, by commonly using IC chips for the active circuit portion and by simply changing the IC chip for the passive circuit portion, it becomes possible to produce a series of IC parts in correspondence to various frequency bands. In particular, a GaAs substrate with a special additive included may be employed in order to draw out certain transistor characteristics in the high frequency band, and such a GaAs substrate tends to be a great deal more expensive than a normal GaAs substrate. Thus, by using different GaAs substrates for the active circuit portion, which is constituted of active elements requiring the semiconductor characteristics in the high frequency band and for the passive circuit portion constituted of passive elements that do not require the semiconductor characteristics, IC parts can be manufactured at a lower cost.
However, in the case of the first type of MMIC, the ceramic IC package in which the active electronic parts are mounted, is a component that must be purchased as far as a manufacturer of semiconductor parts is concerned. Thus, IC parts employing ceramic IC packages tend to be more expensive than IC parts with regular resin mold packages.
In addition, in the case of the second type of MMIC, since it is necessary to design the IC by adding an impedance matching circuit for each frequency to be used, its versatility as a part is poor.
Furthermore, with the second and third type of MMIC, while a GaAs substrate required for constituting the MMIC provides superior insulation, it is still extremely expensive, and it is difficult, therefore, to reduce the product cost.
Moreover, while, with the second and third types of MMIC, it is desirable to employ a conductor such as silver, copper or the like with a low specific resistance for the pattern of the passive elements formed on the MMIC, since these conductors react with the GaAs substrate, it is extremely difficult to use them in practice.
In addition, while the pattern of the passive elements is formed on a GaAs substrate in both the second type and the third type of MMIC, it is necessary to implement grounding for the ground electrodes frequently in the passive circuit. Normally, in the structure of the substrate for constituting the passive circuit, the wiring layer on the substrate assumes a multilayer structure, a planar pattern of the ground electrodes is set in the lower layer and a signal line is set at a layer above it. If there is a node that requires grounding in the passive circuit (an electrode pattern within the circuit), the node is grounded to the ground electrode via a through—hole electrode. In order to achieve this substrate structure with a GaAs substrate, a method whereby a ground electrode is formed on the opposite side from the side where the circuit elements on the GaAs substrate are formed may be considered as a first option. Also a method may be considered whereby a ground electrode is first constituted on a surface where the elements are formed, next, an inorganic insulating layer is formed on the ground electrode and then a signal electrode is formed on the inorganic insulating layer as a second option.
However, with the first method, it is necessary to form holes passing through both the front and rear surfaces of the GaAs substrate being used, these holes, which are extremely fine, must be formed in great numbers and the internal surfaces of these holes must be made electrically continuous by conductors, all of which are practically impossible to achieve.
In addition, in the second method, the inorganic insulating layer formed between the ground electrode and the signal electrode is normally formed through vapor phase epitaxy since a high temperature process must be employed in the semiconductor manufacturing process. However, the inorganic insulating layer will achieve a thickness of only several microns through vapor phase epitaxy. This will result in a reduced line impedance in the signal line formed on the inorganic insulating layer, which, in turn, makes the circuit design extremely difficult. The line impedance in the high frequency band, in particular, will be extremely low. As a means for avoiding a reduction in impedance, the width of the signal line may be set at an extremely small value, but since the conductors are constituted of a thin film and, therefore, their thickness is at approximately several microns, if the width of the signal line is set at an extremely small value, the high frequency resistance will further increase, resulting in an increase in signal insertion loss.
Next, for high
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
Williams Alexander O
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