Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-11-02
2003-02-11
Chaudhuri, Olik (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S624000, C438S778000
Reexamination Certificate
active
06518168
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the derivatization of surfaces with self-assembled monolayers using microcontact printing, and more particularly to selective derivatization of raised portions of substrates, selective derivatization of indentations in substrates, and chemical vapor deposition and sol-gel deposition on substrates in patterns dictated by patterns of self-assembled monolayers.
BACKGROUND OF THE INVENTION
In the fields of microfabrication for microelectronic devices, microoptical devices, and microbiological devices, precision, reproducibility, and small feature size is important. The development of devices that are small relative to the state of the art and conveniently and relatively inexpensively reproduced is a goal. A well-known method of production of such devices is photolithography. In this technique a negative or positive resist (photoresist) is coated onto an exposed surface of a material. The resist then is irradiated in a predetermined pattern, and irradiated (positive resist) or nonirradiated (negative resist) portions of the resist are removed from the surface to produce a predetermined resist pattern on the surface. This can be followed by one or more procedures such as etching, plating, and the like. X-ray and electron-beam lithography have found similar use.
While irradiative lithographic methods may be advantageous in many circumstances, all require relatively sophisticated and expensive apparatus to reproduce a particular pattern, and are relatively time-consuming. Additionally, these techniques are not easily employed with nonplanar surfaces. In the field of electronic circuitry, an attempt is often made to save space by stacking planar circuit boards or chips, the boards or chips interconnected with auxiliary contacts. Alternately, a board or chip may be bent or otherwise formed in a nonplanar manner so as to save space, auxiliary contacts connecting components on different sides of the bend. All too often these auxiliary contacts are the cause of circuitry failure, and the attempt to move from the two-dimensional domain to a three-dimensional domain fails. Irradiative lithography provides no remedy to this complication, nor does it provide a method of conveniently and inexpensively reproducing an existing microelectronic circuit pattern, or the surface morphological features of other objects of interest.
U.S. Pat. No. 5,512,131 (Kumar and Whitesides) entitled “Formation of Microstamped Patterns on Surfaces and Derivative Articles”, issued Oct. 4, 1993, describes a technique for patterning a material surface with an elastomeric stamp. The stamping surface of the stamp is coated with a self-assembled monolayer-forming species having a functional group selected to bind to a particular material. The stamping surface is placed against a surface of the material and, when removed, a self-assembled monolayer of the species is created on the surface according to the stamping surface pattern. Etching and plating can follow.
Microfabrication of patterned materials such as metals and oxides is a very important area of current research and development. Integration of oxide thin films with semiconductor substrates is a critical technology for a variety of microelectronic memory and circuit applications. Current technology of patterning oxides typically involves uniform deposition followed by post-deposition etching. This processing can present difficulties with respect to nonuniform etch rates and ill-defined typography and large index gradients. In particular, LiNbO
3
is especially inert and etch-resistant and these obstacles have led to the use of in-diffusion and ion-exchange techniques to fabricate waveguides.
Copper, prized for its high conductivity and resistance to electromigration, is difficult to pattern as fine lines using conventional techniques such as reactive ion etching. Low throughout of ion-milling processes further complicates the design of a practical commercial process. Chemical vapor deposition is widely used for deposition of metals and ceramics on surfaces, but a simple, convenient technique for patterning a surface using chemical vapor deposition is lacking.
Accordingly, it is an object of the present invention to provide a convenient technique for creating patterned features of metals, oxides, and other materials on surfaces in a manner that minimizes process steps, reduces fabrication costs, and eases environmental concerns by reducing the quantity of chemical process waste. It is another object to provide a technique for selective deposition of such materials in indentations of articles having contoured surfaces.
SUMMARY OF THE INVENTION
The present invention provides techniques for depositing material, in a pattern, on a substrate surface while leaving regions contiguous with the patterned region free of the material or removing material from regions to leave the material in the pattern. A blocking agent is applied to the surface in a pattern and material is deposited in a pattern complementary to the blocking agent pattern, or material is deposited at all regions but removed from the blocking agent pattern. According to one aspect, the method involves effecting chemical vapor deposition on a substrate in a predetermined pattern. The method involves forming on a substrate a blocking agent such as a polymeric agent or a self-assembled monolayer (SAM) of a molecular species in a pattern which acts to block chemical vapor deposition (CVD) where the self-assembled monolayer is formed, and exposing the surface to chemical vapor deposition conditions. Chemical vapor deposition is thereby allowed to occur selectively at regions not covered by the blocking agent. Thus, the method involves allowing a SAM to dictate a pattern in which CVD occurs at a surface. In one embodiment, the method involves transferring a SAM-forming molecular species from an applicator to the surface in a pattern so as to transfer a SAM to a first portion of the surface, while leaving a second portion contiguous with the first portion free of SAM, effecting chemical vapor deposition at the portion of the substrate not covered by the SAM, and removing the SAM. In this and/or other techniques of the invention, the applicator can be a stamp having a conformable surface that is used to transfer the SAM-forming species to the substrate surface. The stamp can have a patterned surface with protrusions and indentations, the outward-facing surfaces of the protrusions defining a stamping surface, or can be essentially flat. The applicator can be an elastomeric polymer.
The present invention provides, according to another aspect, a method involving depositing a pattern of a material such as a metal or metal oxide on a substrate. According to one embodiment, the method involves forming a blocking agent such in a pattern on a substrate and exposing the substrate to a sol-gel precursor of the material and allowing the material to form on the substrate in a pattern dictated by the pattern of the blocking agent. The technique can involve applying a SAM-forming molecular species to a surface of an applicator such as a stamping surface of stamp, contacting a first portion of a substrate with the applicator surface to transfer a SAM to the first portion while leaving a second portion of the substrate contiguous with the first portion free of SAM, applying a sol-gel precursor to the substrate and depositing the material at the second region of the substrate, and removing the oxide from the first portion of the substrate leaving the deposited material at the second portion. In one embodiment, the sol-gel precursor is a precursor of a metal oxide, including a metal or metals selected from the group consisting of Bi, Zr, Sr, Sc, Ta, Li, Nb, Pb, Ti, Ba, and combination thereof. For example, the sol-gel precursor can be a precursor of lead zirconium titanate, barium strontium titanate, lead scandium tantalate, lithium niobate, lead lanthanum titanate, lead zirconium titanate, barium strontium titanate, barium titanate, tantalum oxide, or a combination of
Clem Paul G.
Jeon Noo-Li
Mrksich Milan
Nuzzo Ralph G.
Payne David A.
Chaudhuri Olik
President and Fellows of Harvard College
Schillinger Laura M
Wolf Greenfield & Sacks P.C.
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