Plastic and nonmetallic article shaping or treating: processes – Forming electrical articles by shaping electroconductive... – Conductive carbon containing
Reexamination Certificate
1999-09-09
2001-11-27
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming electrical articles by shaping electroconductive...
Conductive carbon containing
C264S251000, C264S328400, C264S337000, C264S250000
Reexamination Certificate
active
06322736
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to non-photolithographic fabrication of microstructures, and in particular, to an improved mold for fabricating microstructures on one or more substrates using micromolding in capillaries (MIMIC). The mold is especially useful for fabricating plastic microelectronic devices.
BACKGROUND OF THE INVENTION
The demand for inexpensive microelectronic devices has resulted in the development of organic materials potentially useful in electronic and optoelectronic systems. This has led to advances in microelectronic devices that make it possible to inexpensively produce microelectronic devices that occupy large areas and are easily fabricated on rigid or flexible plastic supports. These advances include the development of conducting, semiconducting, and dielectric organic materials.
Unfortunately, present methods for patterning these organic materials are less than adequate. One such method is screen printing. See, Z. Bao, Y. Feng, A. Dodabalapur, V. R. Raju, A. J. Lovinger, “High-performance Plastic Transistors Fabricated by Printing Techniques,” CHEM. MATER. 9 (1997) at 1299-1301. But the use of screen printing in making microelectronic devices such as FETs is limited by relatively poor resolution (~100 &mgr;m) of the screen printing method.
Another method which is capable of generating microstructures in a wide range of materials with feature sizes between one and several hundred microns is micromolding in capillaries (MIMIC). MIMIC involves forming capillary channels between a support and an elastomeric mold that contains recessed channels that emerge from the edges of the mold. A solution containing a solvent and a material (MIMIC solution) which forms the microstructure is applied to the channels at the edges of the mold. Once the solvent in the MIMIC solution evaporates, the mold is lifted from the substrate leaving a microstructure composed of the material. GaAs/AlGaAs heterostructure FETs with dimensions as small as ~20 &mgr;m have been fabricated using MIMIC defined sacrificial polymer layers. The MIMIC defined polymer layers were used in “lift-off” procedures to form the gates and the electrodes of the FETs.
The conventional MIMIC technique, however, has several serious disadvantages. First, the conventional molds used in MIMIC may only be filled by repeatedly applying the MIMIC solution to the recessed channels at the edges of the mold as the solvent in the solution evaporates. Second, when a conventional MIMIC mold is removed, excess unusable material remains on the substrate where the edges of the mold were located. This material must then be removed by cutting it away from the substrate. Third, the MIMIC solution may have to travel a greater distance in an edge filled MIMIC mold which leads to very long filling times. Fourth, patterns made from more than one type of material are not possible with conventional MIMIC molds. Fifth, MIMIC molds can not be easily integrated with conventional printing methods such ink jet printing or screen printing. Sixth, the MIMIC solution can not be forced or drawn into a conventional MIMIC mold with a pressure or a vacuum.
Accordingly, there is a need for an improved mold for use in MIMIC that overcomes the deficiencies of conventional MIMIC molds.
SUMMARY
In accordance with the present invention, an improved mold for use in fabricating microstructures comprises a body of elastomeric material having first and second surfaces, the first surface including at least one recessed microchannel and the second surface including at least one mold filling member that extends through the mold to the first surface and communicates with the recessed microchannel. The mold is used by placing it onto a substrate with the recessed microchannel facing the substrate. The mold filling member of the mold is filled with a liquid material capable of solidifying. The filling member continuously introduces the liquid material into the space defined between the microchannel and the substrate. After the liquid material solidifies, the mold is removed from the substrate thereby leaving a microstructure formed from the solidified liquid material on the substrate.
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Bao Zhenan
Rogers John A.
Agere Systems Inc.
Lowenstein & Sandler PC
Ortiz Angela
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