Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2000-11-02
2001-07-10
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S381000
Reexamination Certificate
active
06258652
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to inductor structures and manufacturing methods and more particularly to spiral inductors adapted for use in monolithic microwave integrated circuits.
As is known in the art, active devices, such as transistors, and passive devices, such as resistors, capacitors and inductors, have been formed on a common single crystal substrate, such as gallium arsenide (GaAs), as a microwave monolithic integrated circuit . One technique used to form the inductor has been to: first form the active devices in the gallium arsenide, deposit a passivation layer of silicon nitride over the processed gallium arsenide, and pattern a layer of photoresist deposited over the silicon nitride layer with a spiral shaped window formed therein. Next, a sequence of titanium followed by gold is deposited over the photoresist layer and through the spiral shaped window onto the exposed portions of the silicon nitride. The photoresist layer is then removed, i.e., “lifted-off”, leaving a spiral shaped inductor on the silicon nitride passivation layer.
While such technique has been useful in many application, the inductor has a relatively low impedance resulting in a relatively narrow bandwidth device.
SUMMARY OF THE INVENTION
In accordance with one feature of the invention, an inductor structure is provided. The inductor has a dielectric body. A spiral shaped pedestal is disposed in one surface of the body. A ground plane conductor is disposed over an opposite surface of the body. A spiral shaped conductor is disposed over the spiral shaped dielectric pedestal.
With such structure, a portion of the electric field in the conductor passes through air having a relatively high dielectric constant thereby increasing the impedance and bandwidth of the inductor.
In accordance with another feature of the invention a method is provided for making an inductor structure. The method includes the steps of: providing a dielectric body; patterning a metalization layer disposed over the dielectric body into a spiral shaped electrical conductor; etching surface portions of the dielectric body exposed by the patterned metalization layer providing a pedestal structure disposed under the patterned metalization layer.
In a preferred embodiment, after the metalization layer has been patterned, a third photoresist layer is deposited over the formed surface. A window is formed in the third photoresist layer over the patterned metalization layer. Exposed portions of the passivation layer are removed. Exposed portions of the dielectric body are removed using a dry, vertically directional etch to produce an inductive structure.
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Daly, Crowley & Mofford LLP
Raytheon Company
Tsai Jey
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