JP2008275440A - Carbon nanotube cantilever for scanning probe microscope and method of manufacturing the same, and scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To approach unevenness of sample surface and measure surface state at high resolution by solving such problems as destruction, deformation of a base probe, destruction of a jointed part, caused by distortion and slipping of the CNT probe, which cause problems in observing the sample surface with a scanning probe microscope using a CNT cantilever. <P>SOLUTION: In a cantilever for a scanning probe microscope which measures surface state with a CNT probe joined to a base probe, the tip part of the base probe is non-sharpened. Moreover, when the cantilever is arranged in measuring state, the non-sharpened tip part of the base probe is arranged closer to the sample surface than the tip of the joined part. With this arrangement, when the CNT probe, due to distortion or slipping, collides with the sample surface, destruction and deformation of the tip part of the base probe and tip part of the joined part can be prevented to provide the CNT cantilever having high durability for a scanning probe microscope. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cantilever for a scanning probe microscope using a carbon nanotube as a probe and a manufacturing method thereof. The present invention also relates to a scanning probe microscope equipped with a carbon nanotube probe needle.

  With the recent miniaturization of semiconductors, high-aspect-ratio microstructures have been proposed and their fabrication techniques have been demanded. Accordingly, measurement techniques have been required to develop measurement methods with nanometer accuracy. The current miniaturization of semiconductors has entered the 45 nm node, and along with this, the aspect ratio has increased, making measurement increasingly difficult.

  The current measurement technology uses a scanning electron microscope (SEM), cleaves the sample or processes a focused ion beam (FIB), and observes the cross section of the sample, but the measurement involves destruction. Therefore, a technique capable of non-destructive three-dimensional measurement is required.

  As one of the solutions, three-dimensional measurement of a semiconductor by a scanning probe microscope (SPM) equipped with a high aspect ratio probe has been attracting attention.

  In an atomic force microscope (AFM), which is one of the surface state observation techniques using SPM, which measures the surface shape with the probe in contact or non-contact with the sample, faithful shape measurement In order to obtain high reproducibility, it is required to increase the aspect and strength of the probe attached to the cantilever.

  Furthermore, Kelvin force microscope (KFM) for detecting surface potential, magnetic force microscope (MFM) for detecting surface magnetic field, chemical force microscope (CFM) for detecting surface distribution of chemical functional groups, which are surface property measurements other than AFM. For example, since the aspect ratio of the probe affects the resolution, a high aspect ratio of the probe is required for high resolution in surface physical property measurement.

  Under such circumstances, in recent years, carbon nanotubes (hereinafter referred to as CNT) have come to be used as AFM probes. This is because the radius of curvature of the tip of the CNT is extremely small, the minimum radius of curvature is about 1 nm, and the length is as long as 1 to 10 μm, so that the aspect can be increased as a probe. Furthermore, since it recovers even if buckling or bending due to physical impact occurs due to the excellent elasticity of CNTs, it has a feature that it has high strength as a probe. From the above points, CNTs have characteristics superior to Si cantilevers as AFM probes.

  For fixing the CNT and the base probe, a method of forming a joint by electron beam irradiation is generally used. As an example, Patent Document 1 describes a method of fixing CNT using amorphous carbon as a coating film. Yes.

JP 2000-227435 A (summary, paragraph number 0046)

  However, in the CNT cantilever, there is a problem that the joint portion for fixing the CNT and the probe as a base are vulnerable to physical impact. For example, in the measurement of the surface state, if there is a large projection that was not expected at the time of measurement, an excessive force may be applied to the probe due to the collision. Also, an excessive force may be applied to the tip of the probe during force curve measurement. If the joint and the base probe for fixing the CNT are weak against physical impact, the base probe is broken or deformed and the joint is broken due to the bending and sliding of the CNT. As a result, the CNT probe may be detached from the base probe and the measurement cannot be continued, or the obtained measurement image may be an image having a shape different from the original surface shape of the sample. is there. These lead to a decrease in productivity in an in-line AFM using a CNT cantilever and an AFM for research and development.

  The object of the present invention is to solve the problem of the destruction of the joint due to the bending and sliding of the CNT, which is a problem in the observation of the sample surface by the scanning probe microscope using the CNT cantilever, and further the destruction of the base probe, An object of the present invention is to provide a cantilever for a scanning probe microscope having improved durability without impairing the characteristics of a CNT probe.

  The present invention relates to a carbon nanotube cantilever for a scanning probe microscope in which a carbon nanotube probe is joined to a base probe formed on a beam of a cantilever, and the base probe is arranged when the cantilever is placed in a measurement state. The junction is provided such that the distance from the tip of the junction of the carbon nanotube probe tip to the sample surface is longer than the distance from the tip of the sample to the sample surface.

  Further, the present invention provides a carbon nanotube cantilever for a scanning probe microscope in which a carbon nanotube probe is joined to a base probe formed on a beam of a cantilever, and the tip of the base probe has a non-sharp shape And the distance from the tip of the junction of the carbon nanotube probe to the sample surface is longer than the distance from the tip of the base probe to the sample surface when the cantilever is placed in the measurement state. The junction is provided so as to be.

  The CNT cantilever of the present invention is less likely to break the joint due to physical collision with an uneven sample. In addition, the tip of the base probe whose tip is not sharpened has little durability and deformation, and has high durability. As a result, measurement over a long period of time with good reproducibility was possible without impairing the characteristics of the CNT probe.

  In the process leading to the present invention, the cause of the weakness of the CNT junction of the CNT cantilever and the base probe to physical impact is that the tip of the base probe is sharpened (tip radius of curvature is about 3 nm) and has low elasticity. It has been clarified that this is due to the presence of a joint for joining the CNT probe at the tip of the base probe.

  The base probe is usually shaped like a quadrangular pyramid, a triangular pyramid, or a cone, but if its tip is sharpened like the apex of the quadrangular pyramid, the base probe will be caused by physical collision with the sample surface. The probe may be destroyed. Also, if there is a CNT joint at the tip of the base probe, the CNT may be peeled off along with the destruction of the base probe. Even if the base probe is not destroyed, the CNT probe joint may be destroyed by physical impact, and the CNT mounting angle may be bent from the joint tip as the base probe is deformed. In order to determine the change in the CNT mounting angle, it is necessary to take a method of measuring a standard sample having a high aspect ratio or checking the CNT angle at the tip of the probe by observing the probe with an SEM. Extra work is added.

  In other words, when the conventional AFM cantilever is used as it is as the base of the CNT probe, weak durability against physical collision appears.

  In the present invention, in a CNT cantilever for a scanning probe microscope, when the cantilever is placed in a measurement state, the distance from the tip of the joint to the sample surface is made longer than the distance from the tip of the base probe to the tip of the CNT. ing. Thus, when a physical impact is applied to the cantilever, the joint is prevented from directly contacting the sample surface, and the CNT joint is difficult to break.

  In addition to the above, the tip of the base probe has a non-sharp shape to suppress the breakage or deformation of the tip of the base probe and the tip of the joint when the CNT probe collides with the sample surface due to bending or sliding. ing.

  The CNT probe is preferably bonded along the ridgeline or surface of the base probe, which makes it possible to bond the CNT probe to the base probe at the same angle with good reproducibility.

  In the cantilever of the present invention, it is desirable that a taper region is formed between the tip of the CNT joint portion of the base probe and the tip portion that is not sharpened. By doing so, it is possible to secure a space where the CNT probe bends in the tapered region at the time of collision with the sample surface, and the CNTs are not easily broken.

  For the base probe, the tip of the base probe in the shape of a quadrangular pyramid, a triangular pyramid, or a cone is cut out, processed to a flat surface by other methods, or made into a hemispherical surface. Is desirable. By sharpening the tip of the base probe, it is possible to prevent the base probe tip and the joint tip from being broken or deformed when they collide with the sample surface due to bending or sliding. In addition, it is possible to secure a space where the CNT probe bends from the tip of the joint when the base probe collides with the sample surface.

  The base probe material is preferably silicon, silicon nitride, metal-coated silicon, or tungsten.

  In the CNT cantilever, it is desirable to form the joint by decomposing the organometallic gas by electron beam irradiation and depositing metal on the electron beam irradiated portion.

  In the scanning probe microscope of the present invention, since the CNT cantilever has high durability, long-time measurement with good reproducibility is possible without impairing the features of the CNT probe.

  According to the present invention, in the measurement of the surface state, it was possible to eliminate measurement problems caused by the destruction and deformation of the base probe and the destruction of the joint due to physical collision with a sample having large unevenness. For example, when an unexpected large unevenness is traced with a CNT probe, the tip of the base collides with the sample surface due to the CNT slipping or bending, causing the tip of the base probe to break or deform, and the AFM As a measurement result, an image different from the original surface shape may be obtained. According to the present invention, such problems can be solved, the surface of the sample can be reliably approached, and the surface properties can be measured.

  According to the present invention, a scanning probe microscope is realized that makes use of the high aspect shape and excellent elasticity of a CNT probe and enables surface shape measurement with faithful shape measurement and high durability. Become. As a result, not only for research purposes but also for manufacturing processes such as semiconductors and HDDs, it is possible to perform product inspections that require high-precision surface condition measurement (inspection process) for a long period of time, eliminating the need for unnecessary measures. A reduction in productivity can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. Further, some examples of the tip shape of the base probe are shown, but the present invention is not limited thereto.

  An example of an AFM in which the CNT cantilever of the present invention is used is an apparatus that measures a surface state by attaching a cantilever, bringing a sample and a cantilever probe into contact, and scanning the sample. It has a feedback mechanism that raises and lowers the cantilever or the sample so that the state at the time of contact becomes constant. As a result, the surface state (for example, unevenness) of the sample can be measured from the control signal. Other scanning probe microscopes include Kelvin force microscope (KFM) for detecting surface potential, magnetic force microscope (MFM) for detecting surface magnetic field, and chemical force microscope (CFM) for detecting surface distribution of chemical functional groups. By using the cantilever of the present invention for these, it is possible to obtain information on the shape and surface properties of the nano region.

  In the embodiments described below, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view of a cantilever according to an embodiment of the present invention. The CNT cantilever 1 includes a beam portion 2 and a base probe 3. The base probe 3 is installed in a cone shape at the tip of the beam portion 2. In this embodiment, the base probe is a quadrangular pyramid, but a similar result can be obtained by using a triangular pyramid or a cone.

  The base probe material includes Si, SiN, or metal-coated Si, but may be a metal such as tungsten and is not limited to the material. The CNT probe 4 is joined on the ridgeline or surface of the base probe 3.

  CNTs include non-doped single-walled and multi-walled carbon nanotubes, carbon nanotubes doped with boron or nitrogen, etc., but nanotubes containing metal atoms or nanotubes carrying metal atoms or metal fine particles at the tips of the nanotubes may be used. In the invention, such various nanotubes can be selected according to the application of the scanning probe microscope.

  As already described, the joint 5 for joining the CNT probe 4 to the ridge line or the surface of the base probe 3 is formed by a method of depositing a product by decomposing a metal compound gas by electron beam irradiation. . As the deposit, tungsten, gold, platinum, or the like can be used.

  The base probe 3 constitutes two characteristic surfaces, one of which is a non-sharp tip surface 6 at the tip. The feature of this surface is that it is substantially parallel to the average plane of the sample surface 8. The other surface is a tapered region 7. The tapered region 7 is provided from the tip of the joint 5 to the non-sharp tip surface 6, and the tip of the joint 5 is protected at the time of collision with the sample surface 8 so that the CNT probe is peeled off and the base probe 3 is protected. Can be prevented from being broken from the vicinity of the tip of the joint 5.

  The processing of the non-sharp tip surface 6 and the tapered region 7 can be performed by a focused ion beam. For example, processing can be performed by irradiating the tip of the base probe 3 with Ga ions.

  FIG. 2 shows an enlarged view of the base probe. In this base probe, after forming a flat surface at the tip of the base probe 3 by box processing of the focused ion beam 12, the metal compound gas is decomposed by electron beam irradiation to deposit a product, and the CNT probe 3 is Can be joined.

  FIG. 3 is an enlarged side view of the tip of the probe when the CNT cantilever collides. According to this arrangement, the CNT probe 4, the non-sharp tip surface 6, the tapered region 7, and the joint tip 9 are present at a position close to the sample surface 8 in this order. When the CNT probe 5 bends or slips in this arrangement, it is the non-sharp tip surface 6 that comes into contact with the sample surface 8, and when contacting with a flat sample surface, the surfaces collide with each other and the tip of the base probe 3. The destruction and deformation of the part can be prevented. Further, even when colliding with a non-flat sample surface, the tip of the base probe 3 is blunted, so that no destruction or deformation occurs. Furthermore, the joint 5 is not destroyed by the protective space created by the tapered region 7 because it does not contact the sample surface 8, and a space for bending the CNT probe from the joint tip 9 is secured. The That is, by preventing the base probe 3 from being broken or deformed and from destroying the joint 5, the CNT probe 4 can be reliably approached to the unevenness of the sample surface for measurement.

  This CNT cantilever can be used for various measurement methods in a scanning probe microscope. For example, the present invention can be applied to an AFM that uses a contact mode, a dynamic mode, or a step-in mode for measuring a shape. It can also be used for Kelvin force microscope (KFM) for detecting surface potential simultaneously with shape measurement, magnetic force microscope (MFM) for detecting surface magnetic field, chemical force microscope (CFM) for detecting surface distribution of chemical functional groups, etc. It is possible to obtain information on the shape and surface properties of the nano region. In addition, it enables the manufacture of products that require highly accurate surface state measurement (inspection process) in the manufacturing process of semiconductors, HDDs and the like as well as research applications.

  FIG. 10 is a configuration diagram of a CNT cantilever in which CNTs are fixed to a commercially available base probe made of Si, and is shown as a comparative example. In this comparative example, the CNT probe 4 and the base probe 3 are fixed by coating the metal by electron beam irradiation and providing the joint 5, but the tip of the base probe 3 and the joint 5 are fixed. When a strong impact is applied by contact with the sample surface 8, the CNT probe 4 is peeled off or the attachment angle of the CNT probe 4 from the joint tip 9 changes.

  FIG. 4 is a perspective view of a CNT cantilever according to another embodiment.

  In this embodiment, the notch 10 is formed at the tip of the base probe 3. The notch 10 can be processed by mechanical shearing or a focused ion beam. In particular, a processing method using mechanical shearing is preferable, and the processing can be performed by a method of shearing the tip of the base probe 3 by scratching the tip of the base probe 3 to the edge of a metal or the like by manipulation in an electron microscope.

  FIG. 5 is an enlarged view showing a process when the tip of the base probe 3 is notched by mechanical shearing. The tip of the base probe 3 is scratched by the metal edge portion 13 to form a plane by mechanical shearing, and then the metal compound gas is decomposed by electron beam irradiation to deposit the product and join the CNT probe 3. be able to. By adopting this method, it is possible to simultaneously process the tip of the base probe 3 and join the CNT probe in the electron microscope.

  FIG. 6 is an enlarged side view of the tip of the probe when the CNT cantilever manufactured through the notch processing step shown in FIG. 5 collides with the sample surface. According to this arrangement, the CNT probe 4, the notch 10, and the tip of the joint 5 are present at positions close to the sample surface 8 in this order. If the CNT probe 5 bends or slips in this arrangement, it is the edge of the notch 10 that comes into contact with the sample surface 10, but the tip of the base probe is blunted and is hardly destroyed. Even if it is broken, the joint 5 is not broken. Furthermore, the joint 5 is not destroyed because it does not contact the sample surface 8 by the protective space formed by the notch 10, and a space for bending the CNT probe from the joint tip 9 can be secured.

  That is, by preventing destruction and deformation of the base probe 3 and destruction of the joint 5, the CNT probe 4 can be reliably approached to the unevenness of the sample surface for measurement.

  FIG. 7 is a perspective view of a CNT cantilever according to another embodiment. In the CNT cantilever of this embodiment, the tip of the base probe 3 is a hemispherical surface 11. The joint portion 5 is formed so as to be disposed immediately above the hemispherical surface 11.

  As a method of processing the tip into a hemispherical surface, dry etching by ion irradiation is desirable as used in a semiconductor process. The tip shape of the base probe need not be a hemisphere having a radius of curvature, and can be formed into various spherical shapes.

  FIG. 8 is an enlarged view showing a processing method of the base probe 3 having the tip of the hemispherical surface 11 and a joint portion of the CNT probe. In this base probe 3, a hemispherical surface is formed at the tip of the base probe 3 by dry etching with an ion shower 14 from the tip direction, and a metal compound gas is decomposed by electron beam irradiation to deposit a product and deposit a product. The needle 3 can be joined.

  FIG. 9 is an enlarged side view of the tip of the probe portion when the CNT cantilever of this embodiment collides with the sample surface 8. According to this arrangement, the CNT probe 4, the hemispherical surface 11, and the tip of the joint portion 5 are present at positions close to the sample surface 8. When the CNT probe 4 is bent or slips in this arrangement, the base probe 3 can be efficiently prevented from being broken because the sample surface 8 collides with the hemispherical surface 11.

  Further, the joint 5 is not destroyed because it does not come into contact with the sample surface 8 by the protective space formed by the tip of the base probe 3 being hemispherical, and there is a space for the CNT probe to bend. It can be secured. That is, by preventing destruction and deformation of the base probe 3 and destruction of the joint 5, the CNT probe 4 can be reliably approached to the unevenness of the sample surface for measurement.

The perspective view of the CNT cantilever by a 1st Example. The enlarged view of the base probe front-end | tip in a 1st Example. The enlarged view when the cantilever by a 1st Example collides with the sample surface. The perspective view of the CNT cantilever by the 2nd Example of this invention. The figure which shows the manufacturing process of the front-end | tip part of the base probe in a 2nd Example. The enlarged view when the CNT cantilever by a 2nd Example collides with the sample surface. The perspective view of the CNT cantilever by a 3rd Example. The enlarged view which showed the processing method of the base probe front-end | tip in 3rd Example, and the joining position of a CNT probe. The enlarged view when the cantilever by a 3rd Example collides with the sample surface. The figure which showed the state when the conventional cantilever collided with the sample surface.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CNT cantilever, 2 ... Beam part, 3 ... Base probe, 4 ... CNT probe, 5 ... Joint part, 6 ... Non-sharp tip surface, 7 ... Taper region, 8 ... Sample surface, 9 ... Joint tip, DESCRIPTION OF SYMBOLS 10 ... Notch part, 11 ... Hemisphere, 12 ... Focused ion beam, 13 ... Metal edge, 14 ... Ion shower.

Claims (12)

  A carbon nanotube cantilever for a scanning probe microscope in which a carbon nanotube probe is bonded to a base probe formed on a beam of a cantilever. When the cantilever is placed in a measurement state, a sample is taken from the tip of the base probe. The carbon for a scanning probe microscope, characterized in that the junction is provided so that the distance from the tip of the junction of the carbon nanotube probe to the sample surface is longer than the distance to the surface Nanotube cantilever.   In a carbon nanotube cantilever for a scanning probe microscope in which a carbon nanotube probe is joined to a base probe formed on a beam of a cantilever, the shape of the tip of the base probe is a non-sharp shape, and When the cantilever is placed in a measurement state, the distance from the tip of the base probe to the sample surface is longer than the distance from the tip of the carbon nanotube probe to the sample surface. A carbon nanotube cantilever for a scanning probe microscope.   3. The carbon nanotube cantilever for a scanning probe microscope according to claim 2, wherein the base probe has a tapered region from the tip of the joint to the tip of the non-sharp shape.   3. The carbon nanotube cantilever for a scanning probe microscope according to claim 2, wherein a tip portion of the base probe having a non-sharp shape is a flat surface.   3. The carbon nanotube cantilever for a scanning probe microscope according to claim 2, wherein the tip of the base probe having a non-sharp shape is a hemispherical surface.   3. The scanning probe according to claim 2, wherein the base probe has a shape of any one of a quadrangular pyramid, a triangular pyramid, and a conical shape, and a tip portion thereof is not sharpened by a notch. Carbon nanotube cantilever for microscope.   3. The carbon nanotube cantilever for a scanning probe microscope according to claim 1, wherein the material of the base probe is made of silicon, silicon nitride metal-coated silicon, or tungsten.   3. The carbon nanotube cantilever for a scanning probe microscope according to claim 1, wherein the carbon nanotube probe is joined along a ridge line or a surface of the base probe.   In a method of manufacturing a carbon nanotube cantilever for a scanning probe microscope, in which a base probe is provided on a beam of a cantilever and a carbon nanotube probe is joined to the base probe, the base is disposed when the cantilever is placed in a measurement state. For the scanning probe microscope, characterized in that the junction is installed such that the distance from the tip of the junction of the carbon nanotube probe to the sample surface is longer than the distance from the tip of the probe to the sample surface A method for producing a carbon nanotube cantilever.   10. The method of manufacturing a carbon nanotube cantilever for a scanning probe microscope according to claim 9, wherein the junction is formed by decomposing an organometallic gas by electron beam irradiation and depositing metal on the electron beam irradiated portion. .   2. A scanning probe microscope comprising a cantilever having a carbon nanotube probe, comprising the cantilever according to claim 1.   A scanning probe microscope comprising a cantilever having a carbon nanotube probe needle, wherein the cantilever according to claim 2 is provided.

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