Etching a substrate: processes – Forming or treating an article whose final configuration has...
Reexamination Certificate
1999-03-26
2001-10-30
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Forming or treating an article whose final configuration has...
C216S041000, C216S057000
Reexamination Certificate
active
06309554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a needle diamond-type structure.
2. Description of the Related Art
Needle diamond-type structures, especially those which have been subjected to doping to attain electrical conductivity are used in electron-emitting sources for display, gas sensors, electrode materials and the like. To be used for such purposes, it is generally important for the needle diamond-type structure to have a minute and regular structure in order to improve the performance of the end-product. A conventional method of forming such a minute and regular structure involves steps in which a mask having a etching-resistant property is applied on a diamond substrate; patterning is performed using a photomask; and then selective etching is performed using a dry etching method.
In addition to the above conventional method, a method for producing a regularly-arranged, minute needle-type structure is also known, in which a casting-structure having minute and regularly arranged dents (cavities) is made of materials like Si in advance using conventional lithography; a diamond is grown by a vapor growth method while using the casting-structure as a mold; and then the casting structure used as a mold is selectively removed by dissolving.
However, the conventional methods employing a resist and exposure technique are limited with regard to minuteness of structures that can be fabricated, due to the diffraction limit of light. Further, if electric beam depiction is used, which can draw more minute patterns, drawing of a pattern requires a longer time, thereby causing a significant increase in the total cost. Moreover, all conventional patterning methods wherein a resist is used commonly require rather complicated steps of application of a resist, exposure to light, and removal of the resist.
With respect to the other type of conventional method, in which a casting structure is made using conventional lithography and a diamond film is formed thereon by a vapor growth method, the limit of fineness depends on the uniformity of the vapor-grown diamond film. Accordingly, since nucleation density of diamond in a vapor growth method is low, there is a certain limit to the fineness of processing.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a method for producing a needle diamond-type structure, in which fine needle-type structures are regularly arranged in a large area at relatively low cost, without including such complicated steps that have been necessary for the above-mentioned conventional methods.
To accomplish the above-mentioned object, there is provided according to the present invention, a method for producing a needle diamond-type structure comprising steps of forming an anodized alumina layer on a diamond substrate, which anodized alumina layer has a plurality of through holes and functions as a mask; vapor-depositing a substance resistant to plasma etching by a vacuum vapor-depositing method to form vacuum vapor-deposited dots on the diamond substrate; removing the anodized alumina layer; and performing a plasma etching treatment while using the vacuum vapor-deposited dots as a mask, thereby forming regularly arranged needle-type diamond columns. The term “through holes” is used herein to refer to holes that go all the way through a substance, for example, an anodized alumina layer. More specifically, in the method according to the present invention, a mask of anodized alumina having a number of minute through holes which are orthogonal to the surface thereof is formed on a diamond substrate; a substance such as a metal, metal oxide or the like is deposited thereon by a vacuum vapor-depositing method; and then the anodized alumina is selectively dissolved by sodium hydroxide or the like, thereby resulting in an arrangement of dots of the deposited substance which corresponds to the pore (i.e., through hole) arrangement of the anodized alumina on a surface of the diamond substrate. The diameters of the pores and the distances therebetween can be regulated by controlling the conditions for anodic oxidation (anodization) and a post-treatment. For the purpose of using an anodized alumina as a mask for vacuum deposition, the aluminum base metal is removed from such anodized alumina and then, the bottom portion of the anodized alumina film is removed by dissolution with use of a solution of, for example, phosphoric acid or the like [Japanese Journal of Applied Physics, vol. 35 P.L126 (1996)]. Various substances may be used to form the minute dots in the vacuum vapor-deposition method, as long as they can be deposited by such a method and are resistant to the plasma etching conducted afterward; such substances include metals, such as Au, Ag, Ni and Cr, metal oxides and metal nitrides.
By conducting a plasma etching treatment while using the vapor deposited dots formed on the diamond substrate as an etching mask and then selectively removing the mask of dots by dissolution, one obtains a needle diamond-type structure having a regular arrangement of minute needle-type columns that corresponds to the arrangement of the dots. The diameters of the needle-type columns and the distances therebetween are identical to those of the dots that were formed using the mask of anodized alumina. Therefore, configuration of the needle diamond-type structure can be regulated by adjusting the geometrical pattern of the through holes in the anodized alumina.
An inert gas, like argon, as well as a gas including oxygen can be effectively used as a gas for etching in the method according to the present invention. The needle-type structure which is formed on a diamond substrate by a method according to the present invention depends on the form of anodized alumina which is used as a mask. It is known that anodized alumina has pores of a uniform diameter which is within a range between 10 nm to 400 nm, and such diameter can be controlled by controlling conditions for anodic oxidation (anodization) and a process of post-treatment.
REFERENCES:
patent: 4957591 (1990-09-01), Sato et al.
patent: 5344526 (1994-09-01), Nishibayashi et al.
patent: 5399238 (1995-03-01), Kumar
patent: 5844252 (1998-12-01), Shiomi et al.
patent: 6139713 (2000-10-01), Masuda
patent: A-63-34927 (1988-02-01), None
patent: A-7-202164 (1995-08-01), None
patent: 2000001393A (2000-01-01), None
Field Emitter Arrays Based on Natural Selforganized Porous Anodic Alumina, Govyadinov et al., Dec., 1997, Technical Digest of IVMC'97 Kyongju, Korea.
Fujishima Akira
Masuda Hideki
Frank Robert J.
Gulakowski Randy
Olsen Allan
The University of Tokyo
Venable
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