Active solid-state devices (e.g. – transistors – solid-state diode – Physical configuration of semiconductor – Mesa structure
Reexamination Certificate
2000-07-06
2001-12-11
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Physical configuration of semiconductor
Mesa structure
C257S624000
Reexamination Certificate
active
06329702
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an interconnect structure having signal feed-throughs that are effective at microwave and millimeter wave frequencies.
BACKGROUND OF THE INVENTION
There is growing demand for very compact, low-cost, high frequency (i.e., microwave or millimeter wave) communications circuits.
In response to this demand, such circuits frequently employ mixed-technology silicon integrated circuit (IC) and gallium arsenide (GaAs) monolithic microwave integrated circuit devices (MMICs) supported on multi-chip module (MCM) substrate structures. The IC and MMICs usually consist of active devices and integrated passive components.
Since these products operate at high frequencies continuity of the RF ground plane is required for the MCM substrate and its mounted microwave GaAs and high-speed silicon active devices. Moreover, the efficiency of the interconnects in transmitting the signal power is required to be high to achieve a very low insertion loss and return loss
To address these requirements, a ball grid array structure (BGA) has been proposed, which allows feed-throughs at microwave and millimeter wave frequencies from electrical components, integrated circuits or MCM substrates to other circuitry such as circuit boards. See, e.g., U.S. Pat. No. 5,694,300 to Mattei et al., U.S. Pat. No. 5,717,245 to Pedder et al. and U.S. Pat. No. 5,355,283 to Marrs et al.
Ball grid arrays, however, conventionally utilize metal interconnects which are limited in their high frequency performance due to parasitic inductance, capacitance and resistance effects.
SUMMARY OF THE INVENTION
The above and other deficiencies of the prior art are addressed by the carrier of the present invention, which comprises: (a) a planar ceramic substrate having first and second faces and (b) at least one feed-through extending from the first face to the second face. The at least one feed-through comprises a pedestal of doped semiconductor that is at least partially surrounded by a conductive metal layer.
Glass is a preferred ceramic substrate material, preferred semiconductor materials include silicon provided with sufficient doping (e.g., arsenic doping) to reduce its resistivity to 0.02 &OHgr;-cm or less, and a pyramidal section is a preferred form for the pedestal. The conductive metal is preferably selected from silver, gold and copper, and the pedestal may be completely surrounded by metal in some embodiments.
Typically, a metallization layer is also provided on at least one face of the planar ceramic substrate. One exemplary metallization layer comprises copper on nickel. The metallization layer can comprise one or more signal paths, for example, one or more radio frequency transmission lines such as microstrip lines or coplanar line structures.
In many preferred embodiments, one or more solder balls are provided on the metallization, on the feed-throughs, or on both the metallization and the feed-throughs.
According to another embodiment of the invention, an electrical assembly is provided, which comprises the above high frequency carrier and a metallized substrate. The first face of the carrier is attached to the metallized substrate and the at least one feed-through is electrically connected to the metallized substrate.
In many cases, it is also preferred to attach at least one electronic element (such as an electronic component or an electronic circuit) to the second face of the carrier, such that the at least one electronic element is electrically connected to at least one feed-through.
The electronic element can comprise, for example, an active device. Preferred active devices include electronic millimeter wave devices such as field-effect transistors, high electron mobility transistors and a heterojunction bipolar transistors.
According to one particular electrical assembly embodiment of, the metallized substrate is an MCM substrate, and the at least one electronic element comprises a semiconductor device.
Preferred metallized substrates for the electrical assembly include printed circuits (e.g., metallized substrates comprising epoxy and fiberglass) and metallized ceramic substrates. The metallization on the metallized substrate also frequently comprises one or more signal paths such as radio frequency transmission lines.
In constructing the electrical assembly, the metallized substrate can be attached to the first face of the high frequency carrier, and the at least one electronic element can be attached to the second face of the high frequency carrier, via one or more solder balls.
One advantage of the present invention is that the feed-throughs are manufactured using high-definition, well-established semiconductor processing technology, providing significant design flexibility. For example, very small feed-throughs can be provided. As a result, a carrier with a very high feed-through density can be realized. In addition, the small size of the feed-throughs within the carrier results in an advantageous reduction in the magnitude of parasitic impedance components. Moreover, control over the parasitic components is good and predictable.
A further advantage of the present invention is that the carrier can be used to provide a metallized substrate with passive circuitry, such as transmission lines. Alternatively, the carrier of the present invention can be used in connection with pre-existing techniques for mounting active components, such as flip-chip mounting, wire bond mounting, and so forth.
These and other advantages and embodiments of the present invention will become immediately apparent to those of ordinary skill in the art upon reading the description and claims to follow.
REFERENCES:
patent: 4023260 (1977-05-01), Schneider et al.
patent: 4210923 (1980-07-01), North et al.
patent: 5343070 (1994-08-01), Goodrich et al.
patent: 5355283 (1994-10-01), Marrs et al.
patent: 5694300 (1997-12-01), Mattei
patent: 5696466 (1997-12-01), Li
patent: 5717245 (1998-02-01), Pedder
Gresham Robert Ian
Ito Ryosuke
Potter Roy
Tyco Electronics Corporation
LandOfFree
High frequency carrier does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High frequency carrier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High frequency carrier will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571285