Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2003-07-15
2004-08-24
Dang, Phuc T. (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S612000, C438S637000
Reexamination Certificate
active
06780744
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to conductive elements for electrically connecting different semiconductor device components to one another. Particularly, the present invention relates to conductive elements that are carried by semiconductor devices. More particularly, the present invention relates to stereolithographically fabricated conductive elements. The present invention also relates to the conductive lines of carrier substrates, such as circuit boards, and to methods of fabricating such carrier substrates.
Intermediate Conductive Elements
2. Background of Related Art
An electronic device typically includes one or more semiconductor devices. The semiconductor devices of an electronic device are electrically connected to a carrier substrate, which, in turn, electrically connects each semiconductor device to other components of the electronic device. In order to fulfill the demands for electronic devices of ever-decreasing size and ever-increasing capability, much of the large, space-consuming circuitry components of conventional electronic devices have been incorporated into semiconductor devices. As a result, many state of the art electronic devices include semiconductor devices that are directly connected to one another.
Conventionally, electrical connections between a semiconductor device and a carrier substrate or another semiconductor device are made by way of wire bonds between bond pads of the semiconductor device and contact pads of the carrier substrate. Wire bonding is somewhat undesirable, however, in that the wire bonds are separately and sequentially formed. As state of the art semiconductor devices typically include large numbers of bond pads positioned closely to one another, wire bonding these semiconductor devices to carrier substrates or other semiconductor devices can be a very time-consuming process.
The semiconductor devices of many state of the art electronic devices are connected to carrier substrates or other semiconductor devices with alternative types of intermediate conductive elements. For example, semiconductor devices can be flip-chip bonded, or bonded by way of a controlled collapse chip connection (C-4) to a substrate or another semiconductor device with conductive structures, such as solder balls. When flip-chip type bonds are used, a minimal amount of the real estate on a carrier substrate or other semiconductor device component is consumed.
Tape automated bonding (TAB) processes, which employ a tape including a dielectric film with conductive traces extending thereacross, have also been used to electrically connect semiconductor devices to other semiconductor device components. Tape automated bonding is useful for forming very thin assemblies of semiconductor devices and substrates.
While all of the bond pads of a semiconductor device may be simultaneously connected with a carrier substrate or another semiconductor device when both flip-chip type bonding and TAB are used, neither of these techniques addresses the need for assemblies of both minimal lateral dimensions and minimal thickness.
Circuit Boards
Circuit boards are often assembled with semiconductor devices to electrically connect different semiconductor devices to one another or to other components of an electronic device. Typically, circuit boards have one or more layers of metal circuitry carried by the insulating, or dielectric, substrates thereof. When circuit boards have conductive circuits extending across more than one plane thereof, the circuits may be electrically connected by way of through holes that are metal plated or filled.
Typically, reinforced polymeric materials are employed as the dielectric substrates of rigid circuit boards. The most commonly used dielectric substrate material is glass-reinforced epoxy. Some circuit boards are made from polyimide resins so as to withstand higher temperatures. Other dielectric materials have also been developed and used to fabricate the dielectric substrates of circuit boards.
Some applications require that the dielectric substrate of the circuit board bend or flex during assembly of the circuit board with semiconductor or other electronic devices or while a device including the circuit board is being used. While some flexible circuit boards have substrates fabricated from flexible dielectric materials that are reinforced with woven or random fibers, unsupported polymeric films may also be used to form the substrates of flexible circuit boards.
Conventional printed circuit boards having a single-layered substrate are machined to define the edges thereof, to bevel the edges thereof, and to form through holes at desired locations. Metal conductive circuits are then formed on one or both surfaces of the printed circuit boards, in communication with metal plating or vias located in the through holes. Originally, conductive materials, such as silver, were printed onto the substrate to form the metal conductive circuits and to plate the through holes or to form vias therein.
Copper-clad laminates, which include a layer of copper secured to a dielectric substrate, can also be used to fabricate circuit boards. Copper is removed from regions of the surface of the substrate where conductive circuits are not desired. Accordingly, the process is referred to as a “subtractive” technique.
Other conventional techniques for forming metal conductive circuits and plating or filling the through holes include electroless plating, electrolytic plating, and plasma-assisted chemical vapor deposition (“CVD”) processes. Etching processes may also be used to pattern the conductive circuits of printed circuit boards. As the metal circuits, plating, or vias are formed on the substrate, these processes are referred to as “additive” techniques.
The substrates of state of the art circuit boards have multiple, laminated layers. The conductive circuits of these circuit boards laterally traverse the surfaces of the boards, as well as several different planes through the interior of the substrate to accommodate the increasingly complex semiconductor devices connected to the substrate while maintaining or decreasing the size of the circuit board. In manufacturing such boards, circuit traces are fabricated, as noted above, on one layer of the substrate prior to laminating the next layer of the substrate thereto. Thus, laminated circuit boards are built up, layer by layer. The use of conventional processes to fabricate multilayer circuit boards is, however, somewhat undesirable since each new layer must be aligned with every previously formed layer of the circuit board to provide the desired functionality.
Completed circuit boards may then be tested. Optical or electrical testing may be conducted to determine whether the circuit boards will function properly.
Circuit boards are typically fabricated on a very large scale, with sheets of several circuit boards typically being supplied to semiconductor device manufacturers or electronic device manufacturers for assembly with semiconductor devices and other electronic components. Conventional, large scale circuit board fabrication processes are typically not useful for fabricating prototype circuit boards.
When a new circuit board design is needed, a prototype circuit board is usually fabricated. Due to the complexity of state of the art semiconductor devices and electronic devices, the fabrication of prototype circuit boards is a very time-consuming process. Moreover, production scale circuit boards based on a certain prototype circuit board design may not provide the same electrical performance as intended.
Accordingly, there is a need for a method that can be employed to quickly fabricate simple and multilayered circuit boards in either very small numbers or very large numbers. There is also a need for a process for fabricating multilayered circuit boards that does not require repeated alignment of each of the new layers of the circuit board with the previously fabricated layers thereof.
Stereolithography
In the past decade, a manufacturing technique termed “ste
Dang Phuc T.
Micro)n Technology, Inc.
TraskBritt
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