Wave transmission lines and networks – Coupling networks – With impedance matching
Reexamination Certificate
1999-03-30
2001-03-13
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Coupling networks
With impedance matching
C333S247000, C257S664000
Reexamination Certificate
active
06201454
ABSTRACT:
FIELD OF THE INVENTION
Embodiments of the present invention relate to impedance compensation structures, and more particularly to a compensated interconnection structure between a semiconductor die or a Monolithic Microwave Integrated Circuit (“MMIC”) chip, and a substrate that improves the insertion loss of the interconnection structure at millimeter wave frequencies.
BACKGROUND
Semiconductors for wireless communication applications operate at radio frequencies (“RF”) and above. As the applications for wireless communication increase, so does the desirability of making use of many frequency bands in the available spectrum. The millimeter wave spectrum is available and desirable for wireless communication purposes. The millimeter spectrum, however, presents certain engineering challenges due to the increased distortion and loss at millimeter wave frequencies. There is also a greater sensitivity to device parasitics at higher frequencies than radio frequencies (“RF”) which are commonly used in wireless communications. Accordingly, the typical parasitics that are tolerated at lower frequencies cannot be ignored at millimeter wave frequencies and still achieve adequate performance for the applications in which they occur.
One of the typical parasitics of all wireless communication systems that include high frequency semiconductors is the complex impedance, primarily inductance, of the bond wire. The bond wire is typically a length of gold wire or ribbon that is connected using ultrasonic energy to a semiconductor device or a MMIC chip contact on one end and an interconnecting contact on an opposite end. The interconnecting contact is typically a conductive pad on a substrate such as a chip on board printed circuit substrate onto which the semiconductor die or MMIC chip is directly attached. With this connection style, there is conventionally a length of wire that has a significant inductive component at millimeter wave frequencies. Conventionally, serial discrete capacitors are used to tune the inductance of the bond wire to a resonant condition. Discrete capacitors, however, are large and take up too much substrate, which is in contravention of the interest in miniaturization. In addition, the normal discrete capacitor tolerances and inherent parasitics render accurate tuning at millimeter wave frequencies impractical from a manufacturing view point. Production errors in certain types of appropriate capacitors can also reduce the total yield of the circuit making the manufacturing process costly. There remains a need, therefore, for a manufacturable and small apparatus for compensating typical bond wire parasitics at millimeter wave frequencies.
SUMMARY
It is an object of an embodiment according to the teachings of the present invention to improve the frequency performance of bond wire interconnects at millimeter wave frequencies.
It is a further object of an embodiment according to the teachings of the present invention to provide a compensation device that is small and simple.
It is a further object of an embodiment according to the teachings of the present invention to provide a compensation device that is reliably manufacturable, repeatable, and low cost.
A semiconductor die or a MMIC chip for attachment to a substrate has a die contact for electrical connection thereto, and an interconnection tuned for operation at an operating frequency. The interconnection is a bond wire connected to the die contact and extends to a substrate contact. The bond wire has a wire length and an associated impedance value. The interconnection further includes a matching element connected to the substrate contact opposite the bond wire. The matching element has a first connecting element, a meander line, and a second connecting element. The matching element is tuned to combine with the bond wire to create a high impedance transmission line which length is substantially equal to half of a guided wavelength of the operating frequency.
A method for making a compensated bond wire comprises the steps of identifying the bond wire to be compensated, and obtaining a predictive model for it. The method further comprises identifying an operating frequency, and calculating an electrical length of a guided half wavelength at the operating frequency. A length of the bond wire is identified, and is subtracted from the length of the guided half wavelength to arrive at the electrical length of a matching element. The method fits a model of the matching element comprising first and second connecting elements and a meander line to the calculated electrical length of the matching element. The method then calls for simulating the electrical behavior of the fitted matching element, and then optimizing a frequency response of the matching element by varying a length of the meander line to combine with the bond wire to achieve an electrical length substantially equal to the guided half wavelength of the operating frequency.
It is a feature of an embodiment according to the teachings of the present invention that a meander line is used for compensating the bond wire impedance to achieve a total electrical length, when combined with the bond wire and the connection elements, equal to a guided half wavelength of the operating frequency.
It is a feature of an embodiment according to the teachings of the present invention that the tuning element is easily and repeatably fabricated with conventional printed transmission line technology.
It is an advantage of an embodiment according to the teachings of the present invention that a wire bond can be used for interconnection at millimeter wave frequencies.
It is an advantage of an embodiment according to the teachings of the present invention that a tuned bond wire is reliably manufacturable.
It is an advantage of an embodiment according to the teachings of the present invention that a tuned bond wire is small and performs according to predictive modeling.
It is a further advantage of an embodiment according to the teachings of the present invention that a compensated bond wire can be manufactured at a low cost.
REFERENCES:
patent: 4353047 (1982-10-01), Noguchi et al.
patent: 6008533 (1999-12-01), Bruce et al.
patent: 0120104 (1987-04-01), None
Jain Nitin
Kinayman Noyan
Bettendorf Justin P.
The Whitaker Corporation
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