JP2006170967A - Probe manufacturing method, probe manufacture device, and probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe, a probe manufacturing method, and a probe manufacturing device capable of removing an impurity on a surface while holding a sharpness of the probe, and capable of manufacturing a property of a probe tip with satisfactory reproducibility. <P>SOLUTION: This probe manufacturing method comprises a process for heating a metal raw material under vacuum or inert gas atmosphere, a process for working the metal raw material into a needle body after the heating, a process for removing the impurity on the needle body surface by heating the needle body under reducing atmosphere, and a process for removing a reducing element adsorbed or diffused in the needle body after removing the impurity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a scanning probe microscope (Scanning Probe Microscopy: SPM), a scanning tunneling microscope (Scanning Tunneling Microscopy: STM), an atomic force microscope (AFM), a field ion microscope (Field Ion Microscopy: FIM), The present invention relates to a method for manufacturing a probe (tip, probe tip) used in a field emission microscope (FEM) or the like, a probe manufacturing apparatus, and a probe.

A scanning tunneling microscope (STM) is a microscope that has a high spatial resolution of several millimeters and can be observed by disassembling each atom depending on conditions. In this method, a probe to which a bias voltage is applied is brought close to the surface of a conductor sample to a distance of several nanometers, and observation is performed using a tunnel current flowing at this time. For this probe, a metal probe having a very sharp tip having a radius of curvature of about several nanometers to several tens of nanometers is used. This material can be of any type as long as it is basically a conductor, but mainly has a high melting point such as tungsten (W), molybdenum (Mo), platinum (Pt), iridium (Ir), rhodium (Rh). Metal is often used. These metal rods are generally processed into a probe shape using an electrolytic polishing method or a mechanical polishing method schematically shown in FIG. In the electropolishing method shown in FIG. 3, a metal rod is immersed in an electrolytic solution and a voltage is applied between the cathode and the portion near the surface of the water melts. It is cut and separated into upper and lower parts to form a probe shape.
TT Tsong, “Atom-probefield ion microscopy”, Cambridge University Press, p.110, (1999) Yasuo Kojima, Masaho Kurahashi, Surface Science, 9,621, (1988) Koshikawa Takanori, Surface Science, 17,553 (1996)).

  The scanning tunneling microscope (STM) has been widely used for research purposes as a powerful technique for surface observation, surface measurement, and nanofabrication taking advantage of its high spatial resolution. However, there are no examples of industrial use as industrial nano-measurement / nano-processing methods. One reason is that there is a problem in the reproducibility of the results obtained by this method.

  In this method, a metal probe having a sharp tip shape is used. In order to obtain reproducible results, it is indispensable to make the surface clean while maintaining the sharpness of the tip of the probe, but this has not been possible with conventional probes. . Here, reproducibility means obtaining the same result again when the same observation / processing process is repeated.

  The reason will be described in detail below. For a scanning tunneling microscope (STM), a metal probe having a very sharp tip having a radius of curvature of about several nanometers to several tens of nanometers is used. This material can be of any type as long as it is basically a conductor, but mainly has a high melting point such as tungsten (W), molybdenum (Mo), platinum (Pt), iridium (Ir), rhodium (Rh). Metal is often used.

In general, these metal rods are processed into a probe shape using an electrolytic polishing method or a mechanical polishing method as schematically shown in FIG. Used as a needle. The surface of the probe immediately after polishing is desirably exposed to a clean metal surface free of impurities in order to obtain good spatial resolution and stability in an observation experiment using a microscope. As shown in FIG. 2, there are many cases where it is contaminated with impurities mainly oxygen (O) and carbon (C). If the probe surface is contaminated with impurities, these impurities move from the root to the tip of the probe during observation or processing, and the state of the tip of the probe changes, which makes the operation of the microscope unstable. To do.
Since the object to be observed and processed by the scanning tunneling microscope (STM) is an atomic size, contamination by an extremely small amount of impurities causes a serious problem.

  FIG. 5 (a) is an Auger electron spectrum obtained by measuring impurities adhering to the surface after electrolytic polishing of a tungsten (W) wire (thickness: 0.3 mm) in a 2N-NaOH aqueous solution for several minutes. Peaks of tungsten (W), carbon (C), calcium (Ca), and oxygen (O) are confirmed on the surface after electrolytic polishing. These impurities are mainly metal oxides and hydrocarbon compounds, which are considered to have adhered to the sample surface during the electropolishing process and subsequent handling.

  These impurities are said to be removable by heating to about 1000 ° C. in a vacuum. Thus, FIG. 5 (b) shows an Auger electron spectrum obtained after heat-treating this sample in an ultrahigh vacuum at 965 ° C. for 60 minutes. In this spectrum, although the peak of carbon (C) was not seen, the peak of oxygen (O) still remained, and the peak of calcum (Ca) became large. On the other hand, a peak attributed to sulfur (S), which was not seen in FIG. 5 (a), was clearly observed. This sulfur (S) is contained as an impurity in the tungsten (W) bulk and segregates on the surface during vacuum heating (J. Vac. Sci. Technol. 7, S91 (1971)). The surface segregated sulfur (S) is considered to form sulfides, but sulfides are extremely stable, and therefore, a high temperature of 1200 ° C. or higher is required to remove them from the surface by heating. From this result, it is clear that impurities cannot be removed only by heating in a temperature range up to 965 ° C. in an ultrahigh vacuum.

  In order to remove impurities on the surface, (a) a method of field evaporation of atoms at the tip of the probe in a high electric field, (b) a method of physically cutting the tip of the probe by a method such as sputtering, (c) in a vacuum Various methods such as heating to a high temperature in an inert gas and evaporating and desorbing are used. However, when using a method such as (a) or (b), as shown in FIG. 4 (b), the radius of curvature of the tip becomes large and sharpness is lost, or FIG. As shown in FIG. 4, the impurities at the pole tip are removed, but the impurities remain at the root portion, causing a problem that the residual impurities adversely affect the observation. On the other hand, when the method (c) is used, an extremely high temperature of 1200 ° C. or higher is necessary to completely remove impurities, but it is often difficult to heat the probe to that temperature. On the other hand, there is a method that can achieve a sufficiently high temperature of 1200 ° C or higher, such as the electron impact heating method, but only the tip part is heated and the impurities at the base cannot be removed, and temperature control is difficult, There is a problem that the probe itself is melted.

  An object of the present invention is to provide a probe manufacturing method, a probe manufacturing apparatus, a probe manufacturing method and a probe manufacturing method capable of removing impurities on the surface while maintaining the sharpness of the probe and manufacturing the probe tip with good reproducibility. To provide a needle.

The present invention employs the following means in order to solve the above problems.
The first means is a step of heating the metal material in vacuum or in an inert gas atmosphere, a step of processing the metal material into a needle-like body after the heating, and the needle-like body in a reducing atmosphere. A step of removing impurities on the surface of the needle-like body by heating, and a reducing element adsorbed or diffused on the needle-like body by heating the needle-like body in vacuum after the removal of the impurities And a step of removing the probe.

  The second means is the first means wherein the step of heating the metal material in a vacuum or in an inert gas atmosphere is to heat the metal material in a vacuum or an inert gas atmosphere at 1200 ° C. or higher. It is a probe manufacturing method characterized by being.

  A third means is the step of heating the metal material in a vacuum or an inert gas atmosphere in the first means, wherein the metal material is heated at 1200 ° C. or higher by direct energization in a vacuum or an inert gas atmosphere. A probe manufacturing method characterized by heating.

  The fourth means, in any one of the first means to the third means, the step of heating the acicular body in a reducing atmosphere to remove impurities on the acicular body surface, In the probe manufacturing method, the needle-like body is heated at 800 ° C. or higher in an atmosphere having a hydrogen partial pressure of 0.01 Torr or higher.

  The fifth means is one of the first means to the fourth means, wherein the needle-like body is adsorbed or diffused by heating the needle-like body in vacuum after removing the impurities. The step of removing the reducing element is a method for manufacturing a probe characterized by heating the needle-like body at 600 ° C. or higher in vacuum after the removal of the impurities.

  Sixth means includes heating means for heating the metal material in a vacuum or in an inert gas atmosphere, needle-like body processing means for processing the metal material into a needle-like body after the heating, and the needle-like body. Impurity removing means for removing impurities on the surface of the needle-like body by heating in a reducing atmosphere, and a reducing element for removing the reducing element adsorbed or diffused on the needle-like body after the removal of the impurities The probe manufacturing apparatus is characterized by comprising a removing means.

  A seventh means is the probe according to the sixth means, wherein the heating means comprises means for heating the metal material in a vacuum or in an inert gas atmosphere at 1200 ° C. or higher. It is a needle manufacturing device.

  An eighth means is the sixth means characterized in that the heating means comprises means for heating the metal material at 1200 ° C. or higher by direct energization in a vacuum or in an inert gas atmosphere. This is a probe manufacturing device.

  The ninth means is any one of the sixth means to the eighth means, wherein the impurity removing means is a method in which the acicular body is not less than 800 ° C. in an atmosphere having a hydrogen partial pressure of 0.01 Torr or more. It is a probe manufacturing apparatus characterized by comprising heating means.

  The tenth means is any one of the sixth means to the ninth means, wherein the reducing element removing means heats the acicular body in a vacuum at 600 ° C. or higher after removing the impurities. This is a probe manufacturing apparatus characterized by comprising means for performing

  The eleventh means is a metal material for producing a probe characterized by removing impurities by heating in a vacuum or in an inert gas atmosphere.

  A twelfth means is the probe according to the eleventh means, wherein the heating in the vacuum or the inert gas atmosphere is heating at 1200 ° C. or higher in the vacuum or the inert gas atmosphere. It is a metal material.

  A thirteenth means is a probe characterized in that a metal material obtained by heating in a vacuum or in an inert gas atmosphere is used as a material.

  The fourteenth means is to heat the metal material in a vacuum or in an inert gas atmosphere, then process it into a needle-like body and heat it in a reducing atmosphere to remove surface impurities, and further vacuum the needle-like body. It is a probe characterized by removing reducing elements adsorbed or diffused by heating in the inside.

  A fifteenth means is characterized in that, in the thirteenth to fourteenth means, the heating in the vacuum or the inert gas atmosphere is heating at 1200 ° C. or higher in the vacuum or the inert gas atmosphere. It is a probe to do.

  The sixteenth means is the heating means according to any one of the fourteenth means to the fifteenth means, wherein the heating of the acicular body in a reducing atmosphere has a hydrogen partial pressure of 0.01 Torr or more. The probe is characterized by heating at 800 ° C. or higher in an atmosphere.

  In the seventeenth means, in any one of the fourteenth means to the sixteenth means, the heating of the needle-like body in a vacuum is performed by heating the needle-like body in a vacuum at 600 ° C. or higher. It is a probe characterized by being.

  According to the invention of claim 1, the surface of the entire probe is extremely clean without exposing the metal as a probe material and without impurities without performing high-temperature heating that impairs the probe tip shape. Can be in a state.

  According to the invention of claim 2, a trace amount of sulfur contained in a metal material used for probe production can be removed, and sulfides can be removed when removing impurities on the surface after processing into a probe shape. Can be prevented from being formed on the surface.

  According to the invention of claim 3, when removing a trace amount of sulfur contained in the metal material, the metal material can be efficiently and simply heated at a low cost.

  According to the invention of claim 4, when processing a metal material into a needle-like body, impurities such as oxides and hydrocarbons adhering to the surface of the needle-like body are heated at a high temperature so as to impair the shape of the probe tip. It can be completely removed without performing.

  According to the invention described in claim 5, the reducing element adsorbed or diffused on the needle-like body when removing impurities such as oxides and hydrocarbons on the surface of the needle-like body may damage the tip shape of the probe. It can be removed easily and completely without heating at high temperature.

  According to the invention described in claim 6, the surface of the metal that is the probe material is exposed on the entire probe, and the probe having an extremely clean surface free of impurities is present at a high temperature that impairs the probe tip shape. It can be manufactured without heating.

  According to the invention of claim 7, after removing the impurities such as oxides and hydrocarbons adhering to the surface after processing into the probe shape, the metal material for the probe is such that no sulfide is formed on the surface. Can be manufactured.

  According to the invention described in claim 8, a probe metal material from which a trace amount of sulfur contained in the metal material is removed can be produced efficiently and simply at low cost.

According to the invention described in claim 9, a probe in which impurities such as oxides and hydrocarbons are not attached to the probe surface is manufactured without performing high-temperature heating that impairs the probe tip shape. Can do.

  According to the invention of claim 10, a probe having a very clean surface from which reducing elements adsorbed on the surface of the needle-like body are removed when removing impurities on the surface of the needle-like body, It can be manufactured without performing high-temperature heating that impairs it.

  According to the invention of claim 11, it is possible to produce a probe in which sulfur does not segregate on the probe surface even when heated.

According to the invention of claim 12, the sulfur component in the metal material can be efficiently removed, and a probe in which sulfur does not segregate on the probe surface even when heated can be produced.

According to the invention of claim 13, since the sulfur does not segregate on the probe surface even when the probe is heated, the tip of the probe is not contaminated with sulfide. Therefore, by using this, stable STM measurement can be performed even after the probe is heated.

According to the invention described in claim 14, since a very clean metal surface can be exposed to the entire probe without performing high temperature heating that impairs the probe tip shape, high spatial resolution and stable STM Measurements can be made.

According to the invention described in claim 15, since the probe does not contain sulfur as an impurity, no sulfide is formed on the surface even when the probe is heated. For this reason, stable STM measurement can be performed even after heating.

  According to the invention of claim 16, since the surface of the probe is not attached with impurities such as oxides and hydrocarbons, and the reducing element is adsorbed, the impurities are newly adsorbed. Hard to do. Therefore, the probe can be cleaned at a relatively low temperature.

  According to the invention of claim 17, since a very clean metal surface can be exposed to the entire probe without performing high temperature heating that impairs the probe tip shape, high spatial resolution and stable STM Measurements can be made.

Furthermore, according to the present invention, it becomes possible to leave the entire probe in a state in which clean metal is exposed. As a result, the state of the tip of the probe is always constant, so that it can be used for good spatial resolution and industrial purposes. Therefore, it is expected to be used stably in sufficient observation, measurement, and processing operations. Furthermore, it has an important effect for elucidating the mechanism of phenomena occurring in these observation, measurement, and processing processes.
Further, the present invention is not only for scanning tunneling microscope (STM), but also for cleaning the tip of a cantilever used in scanning probe microscopes (SPM) including atomic force microscope (AFM), and further, field ion microscope (FIM), The present invention is applicable as a sample cleaning method in a microscope using a needle-shaped sample such as a field emission microscope (FEM).

An embodiment of the present invention will be described with reference to FIGS.
Since impurities adhering to the surface of the metal probe are mainly metal oxides and hydrocarbon compounds, these impurities can be removed by heating to about 1000 ° C. or higher in a vacuum. . However, at this time, sulfur (S), which is an impurity commonly contained in the metals such as tungsten (W), molybdenum (Mo), platinum (Pt), iridium (Ir), rhodium (Rh), pointed out above, Segregate to form sulfide on the surface. Since this sulfide is extremely stable, it is necessary to heat at a high temperature of 1200 ° C. or higher in order to remove it from the surface by heating.

Hereinafter, a probe manufacturing method and a probe manufacturing apparatus according to the present invention capable of removing impurities such as metal oxides, hydrocarbon compounds, and sulfides will be described.
First, as the first step (or in the heating means), as shown in Fig. 1 (a), before processing the metal material into a probe shape, the temperature is set to 1200 ° C or higher in a vacuum or in an inert gas atmosphere in advance. Heat to remove the sulfur component in the metal material. In order to heat to 1200 ° C. or higher, as shown in the figure, a method of heating by directly passing a current through a metal material is the simplest and most effective. At this time, the metal oxide and hydrocarbon compound on the surface are also removed at the same time, but these impurities are reattached in the subsequent formation process of the probe shape.

  Next, as a second step (or in the acicular body processing means), as shown in FIG. 1 (b), the metal material is processed into a probe shape by electrolytic polishing.

  Next, as the third step (or in the impurity removing means), as shown in FIG. 1 (c), after processing into the probe shape, the metal needle is heated in a reducing atmosphere, and the surface oxide and Carbide is reduced and removed. For example, heating is performed at a temperature of 800 ° C. or higher in an atmosphere having a hydrogen partial pressure of 0.01 Torr or higher. By heating the probe in a hydrogen atmosphere, an oxide / carbide reduction reaction occurs, and these impurities can be removed at a lower temperature than when there is no hydrogen.

  Next, as the fourth step (or in the reducing element removing means), as shown in FIG. 1 (d), after removing the impurities, the hydrogen partial pressure is maintained with the probe held at 600 ° C. or higher in vacuum. Is sufficiently reduced to remove reducing elements adsorbed on the metal surface or diffused in the metal, for example, hydrogen.

  After the above steps (or by using each of the above means), the tip of the probe can be cleaned at a heating temperature of 1000 ° C or less, so a sharp probe with a clean metal surface can be produced without melting the tip. I can do it.

Here, it will be described in detail that a probe having a clean surface can be obtained according to the probe manufacturing method and the probe manufacturing apparatus of the present invention compared to the case of manufacturing a conventional probe.
Any material can be used as the probe metal material as long as it has a melting point of 1200 ° C. or higher and does not cause brittle fracture when heated in a hydrogen atmosphere. The sample used was tungsten (W), which is most often used as a probe.

  In the present invention, as shown in FIG. 1 (a), a tungsten (W) wire (thickness 0.3 mm) was heated to 1500 ° C. in an ultra vacuum and set in a stainless steel holder. FIG. 2 (a) shows an Auger electron spectrum when this is introduced into a vacuum and impurities adhering to the surface are evaluated by Auger electron spectroscopy.

As shown in FIG. 2 (a), a small amount of oxygen (O) is present on the sample surface heated to about 1500 ° C., but no other impurities are detected. That is, it can be seen that sulfur (S) in tungsten (W) is completely removed.
Furthermore, as shown in FIG. 2 (b), this sample was once taken out into the atmosphere, subjected to electrolytic polishing, and then introduced again into a vacuum, and Auger electron measurement was performed. As a result, oxygen (O) was used as an impurity. It can be seen that oxygen (O) was attached to the surface by electropolishing.
Furthermore, as shown in FIG. 2 (c), when this chamber is filled with 0.3 Torr of hydrogen and subjected to heat treatment at 830 ° C. for 60 minutes, peaks other than tungsten (W) show sulfur (S). It can be seen that a sufficiently clean tungsten (W) surface is obtained. That is, it is possible to remove sulfur (S) in tungsten (W) by heating to about 1500 ° C. before electropolishing, and that sulfur (S) is segregated on the surface during the subsequent heating in hydrogen. As a result, a clean tungsten (W) surface can be obtained.

It is a figure which shows the probe preparation process based on this invention. It is a figure which shows the Auger electron spectrum which measured the impurity adhering to the surface of the probe which concerns on this invention. It is a figure which shows the preparation process of the probe shape by electropolishing. It is a figure which shows the shape of the probe tip which concerns on a prior art. It is a figure which shows the Auger electron spectrum which measured the impurity adhering to the surface of the probe which concerns on a prior art.

Claims (17)

  Heating the metal material in a vacuum or in an inert gas atmosphere; processing the metal material into a needle-like body after the heating; heating the needle-like body in a reducing atmosphere; A step of removing impurities on the surface of the needle-like body, and a step of removing the reducing element adsorbed or diffused on the needle-like body by heating the needle-like body in vacuum after the removal of the impurities. A probe manufacturing method characterized by comprising:   2. The step of heating the metal material in a vacuum or in an inert gas atmosphere is characterized in that the metal material is heated at 1200 ° C. or higher in a vacuum or in an inert gas atmosphere. Probe manufacturing method.   The step of heating the metal material in a vacuum or in an inert gas atmosphere is characterized in that the metal material is heated at 1200 ° C. or higher by direct energization in a vacuum or in an inert gas atmosphere. The probe manufacturing method according to 1.   The step of removing the impurities on the surface of the acicular body by heating the acicular body in a reducing atmosphere heats the acicular body at 800 ° C. or higher in an atmosphere having a hydrogen partial pressure of 0.01 Torr or higher. The probe manufacturing method according to any one of claims 1 to 3, wherein the probe manufacturing method is characterized.   After the removal of the impurities, the step of removing the reducing element adsorbed or diffused on the needle-like body by heating the needle-like body in a vacuum includes the step of removing the needle-like body after the removal of the impurities. 5. The probe manufacturing method according to claim 1, wherein heating is performed at 600 ° C. or higher in a vacuum.   Heating means for heating a metal material in a vacuum or in an inert gas atmosphere, needle-like body processing means for processing the metal material into a needle-like body after the heating, and heating the needle-like body in a reducing atmosphere An impurity removing means for removing impurities on the surface of the needle-like body, and a reducing element removing means for removing the reducing element adsorbed or diffused on the needle-like body after the removal of the impurities. The probe manufacturing apparatus characterized by the above-mentioned.   The probe manufacturing apparatus according to claim 6, wherein the heating unit includes a unit that heats the metal material at 1200 ° C. or higher in a vacuum or in an inert gas atmosphere.   7. The probe manufacturing apparatus according to claim 6, wherein the heating means includes means for heating the metal material at 1200 ° C. or higher by direct energization in a vacuum or in an inert gas atmosphere. 9. The impurity removing unit according to claim 6, wherein the impurity removing unit comprises a unit that heats the needle-like body at 800 ° C. or higher in an atmosphere having a hydrogen partial pressure of 0.01 Torr or higher. The probe manufacturing apparatus according to one claim.   10. The reducing element removing means is constituted by means for heating the needle-shaped body in a vacuum at 600 ° C. or higher after removing the impurities. The probe manufacturing apparatus according to claim 1.   A metal material for preparing a probe obtained by heating in a vacuum or in an inert gas atmosphere.   12. The metal material according to claim 11, wherein the heating in the vacuum or in the inert gas atmosphere is heating at 1200 ° C. or higher in the vacuum or in the inert gas atmosphere.   A probe using a metal material obtained by heating in a vacuum or in an inert gas atmosphere as a material.   After heating the metal material in vacuum or in an inert gas atmosphere, processing it into a needle-like body, heating it in a reducing atmosphere to remove surface impurities, and further heating the needle-like body in vacuum A probe characterized by removing reducing elements adsorbed or diffused.   15. The probe according to claim 13, wherein the heating in the vacuum or the inert gas atmosphere is heating at 1200 ° C. or higher in the vacuum or the inert gas atmosphere.   The heating of the acicular body in a reducing atmosphere is heating the acicular body at 800 ° C or higher in an atmosphere having a hydrogen partial pressure of 0.01 Torr or higher. The probe according to any one of claims 15. 17. The heating of the needle-like body in a vacuum is heating the needle-like body at 600 ° C. or higher in a vacuum, according to any one of claims 14 to 16. Probe.

Images