KR100745755B1 - Method of manufacturing carbon nanotube probe tip - Google Patents

Abstract

Disclosed is a method for producing a carbon nanotube probe tip. In the method of manufacturing a carbon nanotube probe tip according to the present invention, the method includes preparing a substrate, sequentially forming a catalyst metal layer and an aluminum oxide layer on the substrate, and exposing the catalyst metal layer by anodizing the aluminum oxide layer. Changing to a porous aluminum oxide layer having holes, growing carbon nanotubes on the exposed catalytic metal layer, and selectively masking carbon nanotubes to be used as probe tips by applying a photoresist on the aluminum oxide layer. Exposing the substrate by dry etching a predetermined depth from an upper surface of the aluminum oxide layer not covered by the photoresist, isotropic undercut etching of the substrate surface exposed by the dry etching to form the carbon nanotubes. Forming a supporting tip, such as Etching the catalytic metal layer exposed by sex undercut etching to expose the bottom surface of the aluminum oxide layer surrounding the carbon nanotubes, and wet etching the aluminum oxide layer to remove the aluminum oxide layer and the photoresist thereon. It includes.

Description

Fabrication method of carbon nanotube probe tip

1a to 1n is a process flow diagram showing a method of manufacturing a carbon nanotube tip according to an embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

10: substrate 12: catalyst metal layer

14, 15: aluminum oxide layer 15a: fine holes

20: carbon nanotube 30: photoresist

The present invention relates to a method for manufacturing a probe tip used for Scanning Probe Microscopy (SPM), and more particularly, to a carbon nanotube probe tip capable of increasing information recording / reproducing density and probe uniformity. It relates to a manufacturing method.

Probes can be used in several SPM techniques. For example, STM (Scanning Transmission Microscope) for detecting the surface current by detecting the tunnel current flowing according to the voltage difference applied between the probe and the sample, Atomic Force Microscope (AFM) using the atomic force between the probe and the sample, Magnetic Force Microscope (MFM) using the force between the magnetic field of the sample and the magnetized probe Microscope).

In recent years, recording and reproducing technology based on SPM has also emerged. In recent years, as the recording density increase of hard disks (HDD) has slowed down, thermally assisted recording (HAMR) and probe (Probe Storage) have been proposed as candidates for achieving ultra-high density of 1 Tb / in ² or more. . Among these, in order to record and reproduce information at high speed and high density using the SPM technology, two important challenges are required in the structure of the probe or the manufacturing process thereof. First, the probe tip must be sharp and fine for recording / reproducing small areas of several to tens of nanometers in diameter. Secondly, in order to improve the recording and reproducing speed of information, the manufacturing of the multi-probe array should be easy. In this case, the manufacturing process should be easy and the height uniformity between the probes should be reduced to improve the uniformity of the probe. Therefore, there is a need for improvement of the structure of the probe tip and development of its manufacturing technology capable of meeting these requirements.

The present invention is to improve the above-described problems of the prior art, to provide a method for manufacturing a carbon nanotube probe tip that can increase the recording / reproduction density of the information and the uniformity of the probe.

Carbon nanotube probe tip manufacturing method according to the present invention,

Preparing a substrate;

Sequentially forming a catalyst metal layer and an aluminum oxide layer on the substrate;

Anodizing the aluminum oxide layer to change it into a porous aluminum oxide layer having fine holes exposing the catalyst metal layer;

Growing carbon nanotubes on the exposed catalytic metal layer;

Selectively masking carbon nanotubes to be used as probe tips by applying a photoresist on the aluminum oxide layer;

Exposing the substrate by dry etching a predetermined depth from an upper surface of the aluminum oxide layer not covered by the photoresist;

Forming an end portion for supporting the carbon nanotubes by isotropic undercut etching of the substrate surface exposed by the dry etching;

Etching the catalytic metal layer exposed by the isotropic undercut etching to expose the bottom surface of the aluminum oxide layer surrounding the carbon nanotubes; And

And wet etching the aluminum oxide layer to remove the aluminum oxide layer and the photoresist thereon. Preferably, the method of manufacturing the carbon nanotube probe tip may further include planarizing the top surface of the aluminum oxide layer before applying the photoresist on the aluminum oxide layer. The planarization of the upper surface of the aluminum oxide layer may be performed by a chemical mechanical polishing (CMP) process.

Here, the catalyst metal layer is formed of at least one metal selected from the group consisting of Ni, invar, Fe, Co, and Au. The dry etching is performed by reactive ion etching. Preferably, KOH or NaOH may be used as an etchant in the isotropic undercut etching, and a first mixed solution of nitric acid, hydrofluoric acid, distilled water, FeCl ₃ solution or HgCl ₂ solution may be used as an etchant in the etching of the catalyst metal layer. In addition, a second mixed solution of H ₃ PO ₄ , Cr ₂ O _3, and distilled water may be used as an etchant in the wet etching of the aluminum oxide layer, wherein the second mixed solution is 17.5 ml of H ₃ PO ₄ , Cr _2. 50 g of O ₃ and 500 ml of distilled water are prepared. In the manufacturing method, the substrate is preferably a silicon wafer, the growth of the carbon nanotubes may be performed by chemical vapor deposition.

According to the present invention having the above configuration, it is possible to obtain a carbon nanotube probe tip that can increase the recording / reproducing density of information and the uniformity of the probe.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the method for producing a carbon nanotube probe tip according to the present invention will be described in detail. In this process, the thicknesses of the layers or regions shown in the drawings are exaggerated for clarity.

1a to 1n is a process flow diagram showing a method of manufacturing a carbon nanotube tip according to an embodiment of the present invention.

Referring to FIG. 1A, first, a substrate 10 is prepared, and then a catalyst metal layer 12 and aluminum oxide layers Al ₂ O ₃ and 14 are sequentially formed on the substrate 10. Here, each of the layers may be formed by a thin film deposition method commonly used in a semiconductor process, for example, physical vapor deposition (PVD) or chemical vapor deposition (CVD), and these methods are well known and thus described in detail. The description will be omitted.

The catalyst metal layer 12 is generally known as a material that plays an important role in the low temperature growth in the growth of carbon nanotubes (CNT) by CVD, Ni, Invar, Fe, Co and Au It may be formed of at least one metal selected from the group consisting of. The catalytic metal layer 12 may be deposited not only by the above-described CVD and PVD but also by a coating method such as spin coating and dip coating. In addition, although the single crystal substrate of various materials may be used as the substrate 10, it is preferable to select a silicon wafer that is generally used.

1B and 1C, the aluminum oxide layer 14 is anodized to be changed into a porous aluminum oxide layer 15 having fine holes 15a exposing the catalyst metal layer 12. . Since the anodizing process is generally well known, a detailed description thereof will be omitted. In this embodiment, a mixture of hydrogen fluoride (HF) and ethanol was used for the anodizing treatment, and a porous aluminum oxide layer 15 was obtained as a result of the anodizing treatment.

Referring to FIG. 1D, chemical vapor deposition (CVD), such as plasma enhanced chemical vapor deposition or thermal chemical vapor deposition, is performed on the exposed catalyst metal layer 12 in the micro holes 15a. Grow the carbon nanotubes 20). Since the growth technology of the carbon nanotubes 20 by CVD is well known, a detailed description thereof may be omitted. For example, source gases such as C ₂ H ₂ , CH ₄ , C ₂ H ₄ , C ₂ H ₆ and CO may be used to grow the carbon nanotubes 20, and these source gases may be used in a plasma atmosphere. Alternatively, the carbon nanotubes 20 may be synthesized by decomposition in a high temperature atmosphere. In particular, in the present embodiment, since the step coverage is excellent in the case of CVD, the carbon nanotubes 20 are sufficiently grown in the fine holes 15a when using the carbon nanotube growth technology by CVD. Can be.

1E to 1I, the upper surface of the aluminum oxide layer 15 is planarized by a chemical mechanical polishing (CMP) process. Then, the photoresist 30 is applied on the aluminum oxide layer 15 to selectively mask the carbon nanotubes 20 to be used as the probe tip. Next, the substrate 10 is exposed by reactive ion etching (RIE) from a top surface of the aluminum oxide layer not covered by the photoresist 30.

Referring to FIGS. 1J and 1K, the carbon nanotubes 20 are supported by isotropic undercut etching using an etchant such as KOH or NaOH to expose the substrate surface exposed by the reactive ion etching. The tip portion 10a is formed. In this case, as a result of the formation of the tip portion 10a by the isotropic undercut etching, the bottom surface of the catalyst metal layer 12 may be partially exposed as shown in FIG. 1K.

1L to 1N, the exposed portion of the catalyst metal layer 12 is etched to expose the bottom surface of the aluminum oxide layer 15 surrounding the carbon nanotubes 20. In the etching of the catalyst metal layer 12, a first mixed solution of nitric acid, hydrofluoric acid, and distilled water as an etchant, FeCl ₃ solution, or HgCl ₂ solution may be used.

Then, an etchant is injected into the bottom surface of the aluminum oxide layer 15 to wet-etch the aluminum oxide layer 15, thereby removing the aluminum oxide layer 15 and the photoresist 30 thereon. In the wet etching of the aluminum oxide layer 15, a second mixed solution of H ₃ PO ₄ , Cr ₂ O _3, and distilled water may be used as an etchant. The second mixed solution is prepared at a mixing ratio of 17.5 ml of H ₃ PO ₄ , 50 g of Cr ₂ O ₃ , and 500 ml of distilled water.

Through the above process, it is possible to obtain a carbon nanotube probe tip that can increase the recording / reproduction density of the information and the uniformity of the probe.

According to the present invention having the above configuration, it is possible to obtain a sharp and fine carbon nanotube probe tip. Such a carbon nanotube probe tip can be manufactured with a smaller size than the conventional one, so that the carbon nanotube probe tip is not only suitable for recording / reproducing information at a high density, but also its manufacturing process is simple and easy. In addition, it is easy to control the height of the carbon nanotubes grown on the substrate at the time of manufacture, when manufacturing a multi-probe array, it is possible to reduce the height deviation between the carbon nanotube probe tips, as a result of the uniformity Can be further improved.

In the above, some exemplary embodiments have been described and illustrated in the accompanying drawings in order to facilitate understanding of the present invention, but these embodiments are merely exemplary and various modifications from the embodiments can be made by those skilled in the art. And it should be understood that other equivalent embodiments are possible. Therefore, the present invention is not limited to the illustrated and described structures and process sequences, but should be protected based on the technical spirit of the invention described in the claims.

Claims (12)

Preparing a substrate; Sequentially forming a catalyst metal layer and an aluminum oxide layer on the substrate; Anodizing the aluminum oxide layer to change it into a porous aluminum oxide layer having fine holes exposing the catalyst metal layer; Growing carbon nanotubes on the exposed catalytic metal layer; Selectively masking carbon nanotubes to be used as probe tips by applying a photoresist on the aluminum oxide layer; Exposing the substrate by dry etching a predetermined depth from an upper surface of the aluminum oxide layer not covered by the photoresist; Forming an end portion for supporting the carbon nanotubes by isotropic undercut etching of the substrate surface exposed by the dry etching; Etching the catalytic metal layer exposed by the isotropic undercut etching to expose the bottom surface of the aluminum oxide layer surrounding the carbon nanotubes; And And wet etching the aluminum oxide layer from a bottom side thereof to remove the aluminum oxide layer and the photoresist thereon. The catalyst metal layer is a method for producing a carbon nanotube probe tip, characterized in that formed of at least one metal selected from the group consisting of Ni, Invar (Fe), Fe, Co and Au. The method of claim 1, Before the photoresist is applied on the aluminum oxide layer, planarizing an upper surface of the aluminum oxide layer. The method of claim 2, Planarizing the top surface of the aluminum oxide layer; the carbon nanotube probe tip manufacturing method characterized in that it is carried out by a chemical mechanical polishing (CMP) process. delete The method of claim 1, The dry etching is a method of producing a carbon nanotube probe tip, characterized in that performed by reactive ion etching. The method of claim 1, Method of producing a carbon nanotube probe tip, characterized in that using KOH or NaOH as an etchant in the isotropic undercut etching. The method of claim 1, Method of producing a carbon nanotube probe tip, characterized in that using the first mixed solution of nitric acid, hydrofluoric acid and distilled water, FeCl ₃ solution or HgCl ₂ solution as an etchant in the etching of the catalyst metal layer. The method of claim 1, Method of producing a carbon nanotube probe tip, characterized in that using a second mixture of H ₃ PO ₄ and Cr ₂ O ₃ and distilled water as an etchant in the wet etching of the aluminum oxide layer. The method of claim 8, The second mixed solution is a method for producing a carbon nanotube probe tip, characterized in that the mixture of H ₃ PO ₄ 17.5ml, Cr ₂ O ₃ 50g, distilled water 500mL is prepared in a mixing ratio. The method of claim 1, The substrate is a method of manufacturing a carbon nanotube probe tip, characterized in that the silicon wafer. The method of claim 1, The growth of the carbon nanotubes is a method for producing a carbon nanotube probe tip, characterized in that carried out by chemical vapor deposition. Carbon nanotube probe tip prepared by the method of any one of claims 1 to 3, and 5 to 11.

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