Radiant energy – Inspection of solids or liquids by charged particles
Reexamination Certificate
2002-07-26
2004-07-06
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
C073S105000
Reexamination Certificate
active
06759653
ABSTRACT:
TECHNICAL FIELD
The invention is related to a probe for a scanning type microscope which images a surface structure of a specimen, wherein nanotubes such as a carbon nanotube, BCN (boron carbon nitride) series nanotube, BN (boron nitride) series nanotube, etc. are used for the probe needle, in more detail, related to a probe for a scanning type microscope produced by focused ion beam machining which is manufactured by means of processes such as the nanotube of fastening, purifying and cutting using a focused ion beam apparatus.
BACKGROUND ART
In order to image a surface structure of a specimen by an atomic force microscope abbreviated as AFM, a scanning needle is needed which is caused to approach to the surface of the specimen for getting information from it. As the scanning needle, a cantilever made of silicon or silicon-nitride, on the tip of which a protruding portion (or pyramid portion) is formed, has been known in the past.
A conventional cantilever is formed by means of the micro-fabrication technique such as lithography, etching, etc. Since the cantilever detects atomic force from the surface of specimen by the tip of protruding portion, the degree of cleanness of an image is determined by the degree of sharpness of the tip portion. Then, in the sharpening treatment of the tip end of the protruding portion serving as a probe needle, an oxide process and an etching process for an oxide film which are sort of semi-conductor process technique are utilized. However, there is a lower limit in a reduction of size even in the semi-conductor process technique, so that the degree of sharpness of the tip end of the protruding portion described above is also physically limited.
On the other hand, a carbon nanotube was discovered as a carbon matter having a new structure. The carbon nanotube is from about 1 nm to several 10 nm in diameter and several &mgr;m in length, and its aspect ratio is around 100~1000. It is difficult to form a probe needle of 1 nm diameter by means of the present technique of semiconductor. Therefore, in this respect, the carbon nanotube provides best condition for the probe needle of an AFM.
In such a situation, H. Dai and others published, in Nature (Vol.384, Nov. 14, 1996), a report with respect to an AMF probe in which a carbon nanotube is stuck on the tip of the protruding portion of a cantilever. Though the probe proposed by them was of epoch-making, the carbon nanotube fell off from the protruding portion during repeatedly scanning surfaces of specimens, since the carbon nanotube was simply stuck on the protruding portion
In order to solve this weak point, the present inventors have achieved to develop a method fastening firmly the carbon nanotube to the protruding portion of the cantilever. Results of this invention have been published as the Japanese patent application laid-open (Kokai) Nos. 2000-227435 and 2000-249712.
The first fastening method above-mentioned is that a coating film is formed in an electron microscope by irradiating an electron beam to the base end portion of a nanotube, and next the nanotube is fastened to the cantilever by means of covering the nanotube with the coating film. The second method is that the base end portion of the nanotube is fusion-fastened to the protruding portion of the cantilever by irradiating an electron beam on the base end portion of the nanotube or by causing to flow current, in an electron microscope.
It is a quite skilful method to fasten by coating or fusion-welding a nanotube base end portion using an electron beam, while enlarging an object image by means of an electron microscope. However, there is a limit in energy intensity of an electron beam of the electron microscope, so that this fact causes to yield a limit for coating-strength or fusion-welding-strength, and as the result, it was difficult to obtain fastening-strength beyond a certain degree.
Besides, lengths of nanotubes produced by an arc-discharge are inhomogeneous, so that it is necessary finally to homogenize quality of the nanotube products by unifying the lengths of the nanotubes. However, due to the above limit in the electron microscope, the cutting process of the nanotube has difficult points, so that the control of the nanotube length was not enough well done.
Furthermore, since an electron microscope is a device for treating electron beams, though it is possible to irradiate an electron beam, but being impossible to diffuse atoms of another element, or to implant ions into a probe needle nanotube, therefore, the improvement of the quality of nanotubes has not been progressed
The essential aim of the electron microscope is to obtain enlarged images of specimens in a clean imaging room being in the vacuum state. However, when an organic gas flows into this electron microscope and decomposes, a body-tube and the imaging room, which should be clean, are polluted with the organic gas or the decomposed matter. If this pollution gas is absorbed in and re-emitted from a wall-surface, the gas adheres to a surface of a cantilever. But, since it is difficult to remove the adhered pollution matter by an electron beam, this fact shows that there is a technical limit of the electron microscope, in manufacture of the nanotube probe needle.
Accordingly, an object of the present invention is to find an apparatus other than the electron microscope as a device in which the nanotube is fastened to a protruding portion of a cantilever, and to provide a probe for a scanning type microscope which can fasten and cut a nanotube probe needle and furthermore can improve the quality of the nanotube probe needle by implanting another element atoms, etc.
DISCLOSURE OF INVENTION
The present invention provides, in a probe for a scanning type microscope, by which substance information of a specimen is obtained by means of a tip end of a nanotube probe needle fastened to a cantilever; a probe for a scanning type microscope produced by focused ion beam machining, which is characterized in that the nanotube is fastened to a cantilever with a decomposed deposit produced by decomposing an organic gas by means of a focused ion beam in a focused ion beam apparatus.
The present invention provides a probe for a scanning type microscope described in the first part of the present invention, wherein a hydrocarbon is used for the above described organic gas.
The present invention provides a probe for a scanning type microscope described in the first part of the present invention, wherein an organic-metallic gas is used for the above described organic gas.
The present invention provides a probe for a scanning type microscope described in the first part of the present invention, wherein a silicon cantilever, a silicon-nitride cantilever or a cantilever coated with a conductive substance are utilized as the above described cantilever.
The present invention provides a probe for the scanning microscope produced by focused ion beam machining which is characterized in that unnecessary matter existing in a predetermined region is removed by irradiating an ion beam to the predetermined region of a nanotube probe needle fastened to the cantilever.
The present invention provides a probe for a scanning type microscope described in the fifth part of the present invention, wherein the above described unnecessary matter is a unnecessary deposit heaping up at a tip end portion of the nanotube probe needle or a unnecessary deposit heaping up near a base end portion of the nanotube.
The present invention provides a probe for the scanning microscope produced by focused ion beam machining which is characterized in that an unnecessary part of the nanotube probe needle is cut off and the length of tip end portion of the nanotube probe needle is controlled by irradiating an ion beam to the tip end portion of the nanotube probe needle fastened to the cantilever.
The present invention provides a probe for a scanning type microscope described in the seventh part of the present invention, wherein the nanotube is cut in a perpendicular or an oblique direction, in the cutting of the unnecessary part
Akita Seiji
Harada Akio
Nakayama Yoshikazu
Okawa Takashi
Shirakawabe Yoshiharu
Koda & Androlia
Lee John R.
Leybourne James J.
Yoshikazu Nakayama
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