Active solid-state devices (e.g. – transistors – solid-state diode – Bipolar transistor structure – With specified electrode means
Reexamination Certificate
1998-06-01
2001-08-07
Picardat, Kevin M. (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Bipolar transistor structure
With specified electrode means
C257S049000, C257S077000
Reexamination Certificate
active
06271576
ABSTRACT:
The present invention relates to and is concerned with the creation of electronic devices and circuits as integral electronic circuitry such as sensors that are synthesized on the surfaces and within the body of bulk and thin films of selected ceramic materials by means of laser writing and processing thereon with selected laser devices in an air and/or selected atmosphere.
BACKGROUND
Certain ceramics, such as Silicon carbide (SiC) Boron Nitride (BN) and Aluminum Nitride (AlN), are known to exhibit electrical properties ranging from insulating to semiconducting to conducting, as discussed in U.S. Pat. No. 5,145,741, issued Sept. 8, 1992, entitled “Converting Ceramic Materials to Electrical Conductors and Semiconductors”, and U.S. Pat. No. 5,391,841, issued Feb. 21, 1995, entitled “Laser Processed Coatings on Electronic Circuit Substrates”, both issued to Nathaniel R. Quick. The ceramics under consideration herein, are used to create devices such as conductive tabs, interconnects, vias, wiring patterns, resistors, capacitors, semiconductor devices, sensors and the like electronic components by laser synthesis on the surfaces and within the body of such ceramics to thereby eliminate photolithography processes which require numerous steps and generate undesirable chemical pollutants when processing such traditional electronic devices, components and circuitry.
As is well known Alumina (Al
2
O
3
) dominates the dielectric market as an integrating substrate or device carrier in electronics packaging. AlN, BN and SiC are also of interest, due to their Thermal Coefficient of Expansion (TCE) and for their dielectric constant and higher thermal conductivity than that of Al
2
O
3
. These properties are of substantial interest for new high temperature and aggressive environment applications, particularly where high integrated circuit packing densities are required In the prior art, metallization methods, including dry-film imaging and screen printing have been used for the production of conductive patterns on Alumina, however, metal compatibility with the newer high thermal conductivity ceramic materials such as AlN, BN and SiC, have not been completely solved. Copper and silver paste exhibit a TCE mismatch aggravated by high temperatures and are subject to oxidation which increases their resistivity. In particular, bonding of copper to AlN has proved to be nontrivial. Alumina or stoichiometric aluminum oxynitride (AlON) coatings must be developed on the AlN surface through passivation processes. These passivation processes have poor reproducibility, especially when hot pressed AlN substrates are used. Thus, the direct laser synthesis of conductors in AlN, BN and SiC substrates appears to provide solutions to this long standing prior art problem with regard to metallization and for more simple processing techniques for creating devices and circuitry such as sensors that are compatible with selected ceramic substrates, while satisfying the need for higher temperature, aggressive environment, and higher density integrated circuit packaging applications.
SUMMARY OF THE INVENTION
The present invention provides for the use of selected ceramic materials, chemical doping of the ceramic materials, and use of laser synthesis processing techniques applied to selected areas of the ceramic body for creating electronic component devices such as sensors individually and in an interconnected circuit arrangement on the surface of and/or within a substrate body of the ceramic material, such as for examples AlN, BN and SiC, whether the ceramic is thin film or bulk material. The invention uniquely utilizes the properties of the doped ceramic in combination with selected laser synthesis techniques to create a variety of electronic devices and components, such as capacitors; resistors; diodes; transistors; logic and digital devices; electrical conductors, connection tabs, conductive holes or vias through substrates; and various types of sensors. More specifically, by selective chemical doping designated surface areas and layers of the ceramic substrate body or film with chemical elements, a ceramic is produced that may be readily converted in designated areas thereof by laser synthesis, using one of several laser devices, to create discrete electronic devices and electronic circuit including sensors arrangements. The creation of these various electronic devices and circuits takes place incrementally, such as making a (p-n)-type carrier semiconducting device by laser synthesizing two adjacent areas, one for the (p) and the other for the (n) portion. The required electrical conductive tab connections are laser synthesized on either side of the p-n junction, to thereby form a p-n junction diode. The formation of a simple (p-n-p) or (n-p-n) arrangement is accomplished by an added step in the above diode process by adding an additional (p) or (n) laser synthesized component, with the appropriate electrical conductor connections as noted above with respect to the diode example. Such elemental electronic devices including sensors are readily produced by simple laser synthesis without the traditional multiple step processing and attendant pollution and environmental contamination problems of the prior art processes.
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Laser Transformed SiC Thin Films (K.G. Kreider, D.R.F; Burgess, Jr., M.J. Tarlov, G. Gillen, S. Wright)(R. Lareau and L.M. Casas)
Collins D. M.
Frijouf Rust & Pyle P.A.
Picardat Kevin M.
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