Coating processes – Nonuniform coating – Applying superposed diverse coatings or coating a coated base
Reexamination Certificate
2000-03-20
2001-12-04
Parker, Fred J. (Department: 1762)
Coating processes
Nonuniform coating
Applying superposed diverse coatings or coating a coated base
C427S096400, C427S265000, C427S286000
Reexamination Certificate
active
06326058
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed towards patterning of a substrate. It aims in particular at, but is not restricted to, the creation of microscopically small patterns of the type used in micro-electronics e.g. semiconductor chips and micro-technology. More specifically, the invention relates to the patterning of a substrate by using a patterning device, the pattern being materialized in the form of openings in a transfer region of the patterning device surface.
The invention relates also to the modification of the contacted substrate surface under the influence of fluids filled into or rinsed through the cavity.
The invention relates also to the controlled deposition of one or different types of chemically defined bodies on predetermined areas of the contacted substrate surface.
The term “conformal contact” implies that the surface shapes of two media put on top of each other are similar to such an extent that fluids can essentially not penetrate into the plane where the surfaces meet each other. The term “fluid” refers to both liquids and gases. The fluid may consist of several components such as a solution and of more than one phase such as an emulsion or a suspension (slurry) of bodies in a carrier fluid.
With regard to the potential applications of the invention, the structuring of materials used in microelectronics, in particular silicon wafers, is of central importance. Here, it may be possible to replace certain lithographic processing steps by the patterning with a patterning device. In biotechnology, the controlled deposition of chemically defined bodies (CDBs) may greatly profit from the present invention. As a CDB shall be understood as any object which consists of one or more molecules whose chemical composition is at least partially known at the external region of the body such that a preferential orientation is chemically determinable. In particular, such CDBs may be ligands or receptors which are chemically attractive to specific complementary receptors or ligands like keys that fit into specific locks. In case of such single-molecular particles, the distinction between solution and suspension becomes meaningless.
The fluids can react with the contacted substrate surface in various ways, resulting in dissolution or chemical modification of substrate material, or in precipitation of a new material. The resulting structures are restricted to the exposed areas of the contacted substrate surface, hence replicate the original pattern. After separation from the patterning device, the substrates can be further processed, e.g. by lithographic methods, using deposited layers as masks, or be employed as secondary stamps.
BACKGROUND OF THE INVENTION
The structuring of surfaces according to predetermined patterns is an elementary step in any device-manufacturing process. Precision, speed and cost of the structuring processes frequently are decisive factors for success or failure of a product. The development of microelectronics, microbiology, and microtechnology in general raised these needs enormously, generating ever increasing requirements for smaller structures, larger scale integration, and lower cost.
The classical patterning techniques used in microtechnology are photo- and electron beam lithography. Photolithography is a fast, efficient parallel process. Its principal problem is the diffraction limit which restricts the minimum structural dimensions to about one half to one quarter of the light wavelength. To cope with the shrinking dimensions of microtechnical structures, imaging systems for shorter and shorter wavelengths were developed in recent years. Due to a number of basic limitations, the ultimate limits of conventional optical lithography will be of the order of 100 nm. These dimensions will be reached soon. Near-field optical lithography is not bound to the diffraction limit and therefore suitable for the generation of even smaller structures. This method however, still is in a very early state; its potential for industrial application cannot be estimated yet.
Electron beam lithography is the present day's preferred solution for the generation of structures with very small dimensions. As a serial, direct writing process, however, it becomes slower and slower with increasing complexity of the patterns to be transferred. For this reason, electron beam lithography has been used mainly in mask fabrication so far and not in the mass production of semiconductor chips. Ion beam lithography operates on similar principles as electron beam lithography but is far less established because of ion implantation and other disadvantageous effects.
A basic feature of optical and electron lithography is the use of an overlay, typically an organic polymer, that serves as the base for pattern formation on an underlying substrate. The overlay is formed on the substrate by homogenous deposition. Evaporation or spin-coating from an organic solvent provides a continuous film on the substrate. Exposure of the overlay to radiation (optical, electron or ion) causes localized changes in its chemistry permitting differential dissolution of the overlay and opening up windows in the film onto the underlying substrate. Patterning can then be affected by wet chemical or dry etching processes where the presence of the overlay provides a local, externally controlled physical mask to chemical reaction. Alternatively, material can be deposited onto the substrate through the windows in the overlay by various methods such as evaporation, chemical vapor or sputter deposition, or galvanic techniques.
These methods of pattern formation are tremendously useful; nevertheless they have certain shortcomings: Several steps are required before pattern transfer is complete; dissolution of the overlay requires a development step that exposes the whole system to organic solvents, plasmas or otherwise chemically harsh conditions. Here, bulk quantities of chemicals are consumed even though only quite localized chemical reactions are needed, steps that are generally wasteful of the reagents. The use of physical masks means that when material is deposited through the mask much of it will be unproductively directed onto the tops of the physical mask. Afterwards, where elimination of the externally controlled physical mask is needed, the conditions for this removal can be injurious to the newly formed substrate, especially where fragile organic materials have been deposited. Furthermore, the masking layer provided by the overlay is not reusable so that specialized equipment is required to form a new pattern on an existing or subsequent substrate. Finally, irradiation used to form the pattern can damage the underlying substrate by the introduction of chemical or electronic disturbances in the region near the overlay.
In view of the increasing gap between the needs of industry and the existence of foreseeable limitations of the established techniques, the development of alternatives is highly desirable. Stamping techniques, including embossing and gravure (intaglio printing) are promising candidates in this context. Ignored for many years in micro-technology, they recently began to attract renewed attention: It was demonstrated that structures with very small dimensions, in some cases of less than 100 nm in size, can be replicated by means of stamping techniques as described, with regard to the use of self-assembled monolayers e.g. in the article by A. Kumar, H. Biebuyck and G. M. Whitesides “Patterning SAMs: Applications in Materials Science”, Langmuir 10, 1498 (1994) or by H. Biebuyck, N. B. Larsen, E. Delamarche and B. Michel in “Lithography Beyond Light”, IBM Journal of Research and Development 41, 159-170 (
1997)
, with regard to embossing e.g. by Y. Chou, P.R. Krauss and P.J. Renstrom “Imprint of Sub-25 nm Vias and Trenches in Polymers”, Appl. Phys. Lett. 67, 3114-3116 (1995), and with regard to intaglio techniques e.g. by E. Kim, Y. Xia and G. M. Whitesides “Polymer Microstructures Formed by Molding in Capillaries”, Nature, 376, 581-583 (1995) and by E. Delamarche, A. Bernard, H
Biebuyck Hans
Bruno Michel
Delamarche Emmanuel
Schmid Heinz
International Business Machines - Corporation
Parker Fred J.
Trepp Robert M.
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