Dielectric structure

Details Dielectric structure Dielectric structure

2002-10-10

2003-12-09

Dinkins, Anthony (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C501S134000, C361S311000, C361S313000

Reexamination Certificate

active

06661642

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to the field of dielectric structures. In particular, the present invention relates to the field of dielectric structures suitable for use in capacitor manufacture.
Laminated printed circuit boards, as well as multichip modules, serve as support substrates for electronic components, such as integrated circuits, capacitors, resistors, inductors, and other components. Conventionally, discrete passive components, e.g. resistors, capacitors and inductors, are surface mounted to the printed circuit boards. Such discrete passive components can occupy up to 60% or greater of the real estate of a printed circuit board, thus limiting the space available for the mounting of active components, such as integrated circuits. The removal of passive components from the printed circuit board surface allows for increased density of active components, further miniaturization of the printed circuit board, increased computing power, reduced system noise and reduced noise sensitivity due to shortened leads.
Such removal of discrete passive components from the printed circuit board surface can be achieved by embedding the passive components within the laminated printed circuit board structure. Embedded capacitance has been discussed in the context of capacitive planes providing non-individual or “shared” capacitance. Capacitive planes consist of two laminated metal sheets insulated by a polymer based dielectric layer. Shared capacitance requires the timed use of the capacitance by other components. Such shared capacitance fails to adequately address the need for embedded capacitors that still function as discrete components.
U.S. Pat. No. 6,068,782 (Brandt et al.) discloses a method of providing individual embedded capacitors including the steps of patterning a photoimageable low dielectric constant material on top of a bottom electrode material, depositing capacitance dielectric material by either filling or partially filling the pattern, and then fabricating a capacitor top electrode. Such capacitor dielectric material typically has a high dielectric constant, such as a ceramic or metal oxide. One problem with using such ceramics or metal oxides is that they may be difficult to metallize, i.e. to fabricate an electrode on, using techniques conventionally used in the printed circuit board industry.
Energy storage devices for semiconductors containing dielectric layers having certain dopants, such as gold, have been disclosed. See, for example, U.S. Pat. No. 6,180,252 B1 (Farrell et al.) which discloses capacitors for semiconductors containing a single dielectric layer including a gold doped barium titanate having increased storage capacity as compared to conventional capacitors. These energy storage devices are not taught for use in embeddable capacitors in the area of printed wiring boards.
There is a need for capacitors, particularly embeddable capacitors, having high dielectric constant capacitance dielectric material that are easier to fabricate electrodes on than conventional high dielectric constant capacitance dielectric material.
SUMMARY OF THE INVENTION
It has been surprisingly found that the adhesion of plated electrode layers to high dielectric constant material can be improved by providing a plating dopant in the dielectric material. Such plating dopant promotes plating of the conductive layer on the high dielectric constant material.
The present invention provides a multilayer dielectric structure having a first dielectric layer and a second dielectric layer, wherein the first dielectric layer includes a plating dopant in an amount sufficient to promote plating of a conductive layer on the first dielectric layer. Dielectric structures having a dielectric layer including a plating dopant in an amount sufficient to promote plating of a conductive layer on the dielectric layer are also contemplated by this invention. Capacitors containing such dielectric structures are further contemplated by this invention.
The present invention also provides a method of improving the adhesion of catalytic and plated electrodes to a dielectric layer including the steps of depositing on a substrate a dielectric layer including a plating dopant in an amount sufficient to promote plating of a conductive layer on the first dielectric layer, and plating a conductive layer on the surface of the dielectric layer. Such method is also used in the manufacture of capacitors. In such capacitors, the substrate is typically, in order, a bottom conductive layer and a bottom dielectric layer, with the dielectric layer being disposed on the bottom dielectric layer.
The present invention provides a printed circuit board including an embedded capacitance material, wherein the embedded capacitance material includes a multilayer dielectric structure including a first dielectric layer and a second dielectric layer, wherein the first dielectric layer includes a plating dopant in an amount sufficient to promote plating of a conductive layer on the first dielectric layer. A method of manufacturing the printed circuit board described above is also contemplated herein.
DETAILED DESCRIPTION OF THE INVENTION
As used throughout this specification, the following abbreviations shall have the following meanings, unless the context clearly indicates otherwise: ° C.=degrees Centigrade; rpm=revolutions per minute; mol=moles; hr=hours; min=minute; sec=second; nm=nanometers; cm=centimeters; in.=inches; and wt %=percent by weight.
The terms “printed wiring board” and “printed circuit board” are used interchangeably throughout this specification. “Depositing” and “plating” are used interchangeably throughout this specification and include both electroless plating and electrolytic plating. “Multilayer” refers to two or more layers. The term “dielectric structure” refers to a layer or layers of dielectric material. “Alkyl” refers to linear, branched and cyclic alkyl.
All percentages are by weight, unless otherwise noted. All numerical ranges are inclusive and combinable in any order, except where it is clear that such numerical ranges are constrained to add up to 100%.
The present invention provides a dielectric structure comprising a dielectric layer comprising a plating dopant in an amount sufficient to promote plating of a conductive layer on the dielectric layer. As used herein, “plating dopant” refers to any conductive element or compound present in the dielectric layer in an amount sufficient to promote plating of the surface of the dielectric layer with a conductive material. Such dielectric structures are particularly suitable for the fabrication of capacitors, and more particularly for the fabrication of capacitors that can be embedded within a laminated printed circuit board. Such capacitors contain a pair of electrodes (conductive layers or metal layers) on opposite sides of and in intimate contact with the capacitor dielectric material. Capacitance density is determined by the electrode surface area, the dielectric constant of the dielectric material and the thickness of the capacitor. The present invention provides an increase in electrode area for a given geometrical area and a decrease in dielectric material thickness without increasing the likelihood of short circuits.
Typically, the dielectric material useful in the present dielectric structures is any that is suitable for use as capacitor dielectric material. A wide variety of dielectric material may be suitably employed, depending upon the design requirements of the capacitor. Suitable dielectric material includes that having a dielectric constant of 2 or greater. Particularly useful dielectric materials are those having a dielectric constant of 3 or greater. In one embodiment, the dielectric material has a high dielectric constant. By “high” dielectric constant it is meant a dielectric constant≧7, and preferably >7. A wide variety of dielectric materials may suitably be used, including, but not limited to, polymers, ceramics, metal o

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