Semiconductor device manufacturing: process – Having organic semiconductive component
Reexamination Certificate
1999-06-17
2001-09-25
Bowers, Charles (Department: 2823)
Semiconductor device manufacturing: process
Having organic semiconductive component
Reexamination Certificate
active
06294401
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fabrication of electronic, chemical, and mechanical devices by deposition techniques such as printing.
BACKGROUND OF THE INVENTION
Electronic and electromechanical components are presently fabricated in large, immobile manufacturing facilities that are tremendously expensive to build and operate. For example, semiconductor device fabrication generally requires specialized microlithography and chemical etching equipment, as well as extensive measures to avoid process contamination.
The large up-front investment required for manufacturing capacity not only limits its general availability, but also increases the cost of custom fabrication. For a small custom order to be financially competitive with mass production of an established device, the per-unit cost will necessarily be quite high—often out of reach for many designers. Currently, the economics of device fabrication disfavors sophistication and small batch sizes.
In addition to their expense, the fabrication processes ordinarily employed to create electronic and electromechanical components involve harsh conditions such as high temperatures and/or caustic chemicals, limiting the ability to integrate their manufacture with that of functionally related but environmentally sensitive elements. For example, the high temperatures used in silicon processing may prevent three-dimensional fabrication and large-area fabrication; these temperatures are also incompatible with heat-sensitive materials such as organic and biological molecules. High temperatures also preclude fabrication on substrates such as conventional flexible plastics, which offer widespread availability and low cost.
These fabrication processes are also subtractive, depositing a desired material over an entire substrate before removing it from undesired locations through techniques such as etching and lift-off. Subtractive processes are wasteful; introduce dangerous, costly, and environmentally unfriendly chemicals to the fabrication process; and limit the range of manufacturable devices since the etch chemistry can interact with previously deposited layers.
Approaches toward reducing the cost of custom manufacture are described in copending application Ser. No. 08/958,098 and published PCT Application WO 98/03896. In accordance with these publications, semiconductor devices are fabricated by successive deposition of electrically active layers in a manner analogous to conventional printing. The described processes facilitate manufacture outside of vacuum, in an artibrary pattern and on a wide range of substrates, without the need for specialized techniques such as chemical etching. They are also additive, confining material deposition to appropriate areas.
These processes, while highly advantageous in some applications, are nonetheless limited in terms of the properties achievable by the resulting devices. In particular, devices based on electrically active particles dispersed in an inert binder tend to be limited in terms of clock speed owing to the permanent spacing between particles. While it is possible to increase clock speed by fusing the particles into a continuous layer, this requires high-temperature processing which is costly and, as noted above, may damage the substrate or other electrically active layers.
DESCRIPTION OF THE INVENTION
Brief Summary of the Invention
The present invention overcomes the limitations of the prior art through the innovative use of nanoparticles to create, through deposition and patterning, functional electronic, electromechanical, chemical, and mechanical systems. The invention exploits the fact that many physical, electrical, and optical properties that appear constant in the bulk of organic and inorganic materials are size-dependent at the very small scales characteristic of nanoparticles. At these sizes—ranging from nearly 1 to 999 nm—the ratio of surface atoms to interior atoms becomes nonnegligible, and particle properties therefore lie between those of the bulk and atomic materials. Monodisperse (i.e., uniformly sized) or polydisperse nanoparticles can form stable colloids in appropriate dispersing media, facilitating their deposition and processing in a liquid state. As a result, additive printing technology can be utilized to deposit and pattern nanoparticles for mass production or for personal desktop manufacturing.
Furthermore, a key property that changes at small sizes is melting point. The effect is substantial; in some semiconductors, melting points have been observed to drop more than 1000° C. from the bulk material. The melting point depression observed in nanoparticle systems faciliates the low-temperature sintering, annealing, and melting of nanoparticles into crystalline films. As a result, nanoparticles can be printed and heated at low temperatures to form films of the bulk material, or can instead be printed and left in dispersed form to retain the size-dependent properties characteristic of the nanoparticles.
Unlike conventional electrically active particles, nanoparticles are formed not by grinding, but instead via chemical methods (such as pyrolysis) or physical methods (such as physical vapor synthesis). Nanoparticles useful in accordance with the present invention may be pristine or surrounded by a “capping” group to passivate the surface, alter surface chemistry, facilitate dispersion in a liquid, or modify some other aspect of the particle's morphology or behavior. Following their deposition, nanoparticles can self-assemble to form highly ordered thin films and superlattices that may exhibit multiple phases.
Accordingly, in a preferred embodiment, the invention comprises a method of fabricating an active component comprised of portions consisting of different materials, at least one of the starting materials being in the form of nanoparticles dispersed in a carrier. The nanoparticles differ from a bulk material of identical composition in at least one physical property, thereby conferring a desired functionality or processing advantage. In accordance with the method, the materials are deposited onto a substrate in a succession of layers which, in sum, define a selected electrical, mechanical, chemical, and/or electromechanical activity of the component. The nanoparticles within each deposited layer are immobilized (by fusing, melting, or annealing the particles into a continuous material, by curing the carrier into a permanent matrix, by surrounding the nanoparticles with bifunctional surface groups that link adjacent nanoparticles, or merely by evaporating the carrier using heat or low pressure) in order to facilitate performance of the intended function. Also within the scope of the invention are components fabricated in accordance with the methods hereof.
REFERENCES:
patent: 5262357 (1993-11-01), Alvisatos et al.
patent: 5470910 (1995-11-01), Spanhel et al.
patent: 5559057 (1996-09-01), Goldstein
patent: 5576248 (1996-11-01), Goldstein
patent: 5711803 (1998-01-01), Pehnt et al.
patent: 5751018 (1998-05-01), Alivisatos et al.
patent: 5892230 (1999-04-01), Goodberlet et al.
patent: WO93/10564 (1993-05-01), None
patent: WO98/03896 (1998-01-01), None
Kotov et al., “Layer-by-Layer Self-Assembly of Polyelectrolyte—Semiconductor Nanoparticle Composite Films,” J. Phys. Chem., pp. 13065-13069, (1995).
Schlamp et al., “Improved efficiencies in light emitting diodes made with CdSe(CdS) core/shell type nanocrystals and a semiconducting polymer,” J. Appl. Phys. 82 (11), pp. 5837-5842, (Dec. 1, 1997).
Schultz et al., “Spray Deposition of CdTe Thin Films Using Nanoparticle Precur-sors,” Materials of Science Forum, vol. 225-227, pp. 169-174, (1996).
Greenham et al., “Charge separation and transport in conjugated poly-mer/cadmium selenide nanocrystal composited studied by photoluminescence quenching and photoconductivity,” Synthetic Metals 84, pp. 545-546, (1997).
Cassagneau et al., “Layer-by-Layer Assembly of Thin Film Zener Diodes from Conducting Polymers and CdSe Nanoparticles,” J. Am. Chem. Soc., 120, pp. 7848-7859, (1998).
Alivisatos, A.P., MRS Bu
Fuller Sawyer
Hubert Brian N.
Jacobson Joseph M.
Nivi Babak
Ridley Brent
Bowers Charles
Brewster William M.
Massachusetts Institute of Technology
Testa Hurwitz & Thibeault LLP
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