JPH09304410A - Afm cantilever - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of product and the slability of AFM measurement by eliminating warping of a cantilever part caused by change in thickness during the formation of a light reflection film, and thermal change during the measurement in an AFM cantilever having the light reflection film formed on the rear of the cantilever part. SOLUTION: Near the free end of a cantilever part 1 made of silicon nitride, a probe part 2 made of the same silicon nitride is provided while a support part 3 made of glass is provided at the base part of the cantilever part 1 and a light reflection film 4 comprising a multi-layer film having gold laminated on chromium is locally formed on the rear of the side opposite to the direction in which the tip of a probe part 2 extends near the free end of the cantilever part 1 to form an AFM cantilever.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an AFM used in an atomic force microscope (AFM).
About the cantilever.

[0002]

2. Description of the Related Art Conventionally, a scanning tunneling microscope (STM) has been used as a device for observing a conductive sample with a resolution of atomic size order.
Since it was invented by ng and Rohrer et al., it has been used in various fields as a microscope that can observe surface irregularities on the atomic order. However, in STM, observable samples are limited to conductive ones.

Therefore, an atomic force microscope (hereinafter referred to as an atomic force microscope) is used as a microscope capable of observing an insulating sample, which has been difficult to measure by the STM, with an accuracy of the order of the atomic size while utilizing elemental technologies such as a servo technique in the STM. AF
M) was proposed. This AFM is disclosed in, for example,
130302 (IBM, G. Binich, Method and Apparatus for Imaging a Sample Surface).

The structure of the AFM is similar to that of the STM and is positioned as one of scanning probe microscopes. AF
In M, a cantilever having a sharp protrusion (probe) at its free end is brought close to the sample so that the interaction force acts between the atom at the tip of the probe and the sample atom. By measuring the movement of the cantilever which is displaced by the electric or optical, the sample is scanned in the XY directions, and the positional relationship between the cantilever and the probe portion is relatively changed. It is now possible to capture three-dimensional information such as unevenness information of a sample on the order of atomic size.

As a cantilever tip for a scanning probe microscope such as AFM having the above-mentioned structure, T.I. R. A
Since lbrecht et al. proposed a silicon oxide film cantilever that can be manufactured by applying the semiconductor IC manufacturing process [Thomas R. Albrecht and Calvin F. Quate:
Atomic resolution imaging of a nonconductor Atomf
orce Microscopy J. Appl. Phy. 62 (1987) 2599], it has become possible to fabricate with high precision in the micron order and with excellent reproducibility. Further, such a cantilever chip can be manufactured by a batch process, and cost reduction is realized. Therefore, at present, cantilever chips manufactured by applying a semiconductor IC manufacturing process are mainly used.

Next, a generally used cantilever manufacturing method to which the above-described IC manufacturing process is applied will be described with reference to FIGS. First,
As shown in FIG. 7A, a silicon nitride film pattern 102 is formed on a silicon substrate 101 having a plane orientation (100). Next, by using the silicon nitride film pattern 102 as an etching resistant mask, the silicon substrate 101 is subjected to wet anisotropic etching using KOH or the like, as shown in FIG. 7B. A quadrangular pyramid-shaped replica hole 103, which will be the mold for the cantilever probe, is formed in the. After that, the silicon nitride film pattern 102 is once removed, a silicon nitride film which is a new base material of the cantilever portion is newly deposited on the silicon substrate 101, and this silicon nitride film is selectively etched into the shape of the cantilever portion. As a result, as shown in FIG.
A cantilever portion 105 in which 4 is integrally formed is formed.
Then, as shown in FIG. 7D, the cantilever portion is
A cantilever support 106 made of Pyrex glass is anodically bonded to a predetermined region on the surface of the cantilever. Then, the silicon substrate 101 is removed by etching to form a cantilever including a probe portion 104, a cantilever portion 105, and a support portion 106, as shown in FIG. 7E, and finally the tip of the probe portion 104. By vapor-depositing a light reflection film 107 made of, for example, a multilayer film of gold and chromium on the entire surface of the cantilever portion 105 (the back surface of the cantilever portion) on the side opposite to the extending direction of
Obtain 100 AFM cantilevers.

Next, a schematic structure of a general AFM device will be described with reference to FIG. In FIG. 8, 201 is a cantilever, and the cantilever 201 is displaced according to the unevenness of the sample 202. The amount of this displacement is due to the light reflecting film 203 provided on the back surface of the cantilever 201 and the light source 204.
The light from is emitted through the lens 205, and the reflected light is optically processed by the displacement detection system 206 to be detected. Then, in order to obtain a sufficient intensity of the reflected light, the light reflecting film 203 is usually formed on the entire back surface of the cantilever.

[0008]

By the way, in the AFM cantilever, when the cantilever forming film is formed so that the cantilever part does not warp when the cantilever part is formed, the cantilever forming film is formed according to the cantilever design film thickness. ,
The condition is such that the film stress becomes appropriate. When forming the light reflecting film on the cantilever portion, the film forming conditions for forming the cantilever film must be determined in consideration of the influence of the reflecting film. However, if the film thickness of the light reflecting film changes, the cantilever portion warps, and if the designed film thickness of the light reflecting film is changed, the film forming conditions of the cantilever forming film also have to be changed. There is.

Further, since the cantilever portion on which the light reflecting film is formed has a two-layer structure of the light reflecting film and the cantilever forming film, if laser light continues to be radiated to the back surface of the cantilever portion during AFM measurement, its heat Also, there is a problem that the cantilever portion is warped due to the difference in thermal expansion coefficient.

As the material of the probe portion formed on the AFM cantilever, the optimum one should be selected according to the AFM measurement sample and the measurement method. In this case, when the silicon substrate on which the replica hole serving as the mold of the probe part is formed is finally removed by etching, the probe part is exposed to the etching solution, and thus the etching solution is used as a material for forming the probe part. It has to endure. Therefore, there is a problem that the types of materials that can be selected as the material for forming the probe portion are very limited.

Furthermore, in the non-contact AFM measurement in which the probe part and the measurement sample are separated, the cantilever part is brought closer to the sample while vibrating, and the force that the probe part receives from the sample due to the change of its resonance frequency. Are seeking. And
Generally, in order to vibrate the cantilever portion, the cantilever support portion is connected to a piezoelectric oscillator or the like, and the support portion is thereby vibrated to indirectly vibrate the cantilever portion. On the other hand, a method has been developed to increase the measurement sensitivity by providing a magnetic substance near the free end of the cantilever part and directly vibrating the cantilever part by controlling an external magnetic field to perform the above-mentioned measurement. There is.
In order to produce an AFM cantilever used for such a purpose, after producing a conventionally used cantilever,
This is performed by aligning a jig having a minute opening with the vicinity of the free end of the cantilever and then sputtering a magnetic material. However, it is extremely difficult to align the opening of the jig with a specific position on the cantilever, and there is a problem that mass productivity is poor.

The present invention has been made to solve the above problems in the conventional AFM cantilever. The invention according to claim 1 is an AFM cantilever in which a light reflecting film is formed on the back surface of the cantilever portion. An object of the present invention is to provide a configuration in which the cantilever portion does not warp even if the film thickness varies, and the cantilever portion does not warp even when laser light is continuously irradiated during AFM measurement. In addition to the object of the invention described in claim 1, it is another object of the invention to provide a structure capable of widening the range of selection of materials used for the probe part. In addition to the object of the invention according to claim 1, the invention according to claim 3 is an AFM cantilever in which the cantilever portion is directly vibrated by controlling an external magnetic field to enable measurement.
An object of the present invention is to provide a structure that facilitates the disposition of a magnetic body near the free end of the cantilever portion. Further, the invention according to claim 4 aims to easily form a light reflection film having good characteristics in the AFM cantilever according to the inventions according to claims 1 to 3.

[0013]

In order to solve the above problems, the invention according to claim 1 is provided with a probe portion near the free end of the cantilever portion extending from the supporting portion, and the free end of the cantilever portion is provided. A light reflecting film is locally formed in the vicinity and A
It constitutes an FM cantilever. With this configuration, the film stress of the light reflecting film has less influence on the cantilever portion, and therefore even if the film thickness of the light reflecting film changes, the warp of the cantilever portion is not affected. Even if the light reflection film is continuously irradiated with the laser beam during the AFM measurement, the two-layer structure portion of the film forming the cantilever portion and the light reflection film is local, so that the entire cantilever portion is not warped.

The invention according to claim 2 is the A according to claim 1.
In the FM cantilever, the locally formed light-reflecting film is provided so as to cover the bottom surface of the probe portion provided near the free end of the cantilever portion. With this configuration, when the substrate is etched and removed to form the cantilever portion, the probe portion can be prevented from being exposed to the etching liquid, and therefore, the material for forming the probe portion can be selected. The width can be increased. Further, since the probe part can be protected by the light reflecting film, it is not necessary to provide an extra protective film forming step prior to the substrate etching removal step, and the AFM cantilever having the probe part formed of a special member at a low cost is provided. Can be realized.

The invention according to claim 3 is the A according to claim 1.
In the FM cantilever, a magnetic film is locally formed near the free end of the cantilever portion, and the light reflection film is formed so as to cover the magnetic film. With this configuration, the magnetic film has a structure protected by the light reflection film, and therefore, the step of forming the magnetic film on the cantilever portion is performed before the etching removal step of the substrate for forming the cantilever portion. This makes it possible to form the magnetic film in the designated region on the cantilever portion with high accuracy and precision by using the photolithography technique.

According to a fourth aspect of the present invention, in the AFM cantilever according to any one of the first to third aspects, the light reflection film is a laminated film in which gold is laminated on chromium formed by a lift-off method. It is what constitutes. By using a laminated film in which gold is laminated on chrome as the light reflecting film, it is possible to withstand a chemical solution such as KOH when etching and removing the substrate for forming the cantilever portion, and chromium is used as the base. Since it is used, adhesion is improved and peeling can be prevented.

[0017]

Next, an embodiment will be described. 1A and 1B are views showing a configuration of a first embodiment of an AFM cantilever according to the present invention, FIG. 1A being a cross-sectional view thereof, and FIG. 1B being a top view thereof. In the figure, 1 is a cantilever portion, 2 is a probe portion provided near the free end of the cantilever portion 1, 3 is a support portion provided at the base of the cantilever portion 1, the cantilever portion 1 and the probe needle. Each of the parts 2 is formed of, for example, a silicon nitride film, and the support part 3 is formed of, for example, glass. Then, in the vicinity of the free end of the cantilever portion 1,
The light reflection film 4 is locally formed on the surface opposite to the extending direction of the tip of the probe portion 2. This light reflection film 4 is
For example, it is formed of a multilayer film in which gold is laminated on chrome.

Next, the manufacturing method of the AFM cantilever according to the first embodiment having the above-described structure will be described with reference to FIG.
This will be described with reference to the manufacturing process diagrams shown in FIGS. First, in the same way as the method described in the prior art, the plane orientation (100)
2 is prepared, and the substrate 11 is subjected to wet anisotropic etching using KOH or the like, so that the silicon substrate 11 becomes a mold of a probe portion as shown in FIG. 2 (A). A quadrangular pyramid-shaped replica hole 12 is formed. Next, as shown in FIG. 2B, a silicon nitride film 13, which is a base material of the cantilever portion, is deposited on the silicon substrate 11 having the replica hole 12, and the silicon nitride film 13 is formed into a cantilever pattern. By etching, as shown in FIG. 2C, a cantilever portion 15 integrally provided with the probe portion 14 at one end is formed.

Next, a light reflection film 16 is formed near the tip of the cantilever portion 15. The light reflecting film 16 has a multilayer film structure in which gold is laminated on chrome, for example. As a method of forming the light reflection film 16, a light reflection film member is formed after forming a sacrifice film such as a photoresist having an opening at a predetermined position where the light reflection film is to be formed, and then forming the light reflection film member. It is formed by using a so-called lift-off method in which the sacrificial film is peeled off and the light reflecting film is selectively formed only at a predetermined portion. Next, as shown in FIG. 2D, a supporting portion 17 made of Pyrex glass is anodically bonded to a predetermined region of the cantilever portion 15 opposite to the probe portion 14. Finally, by removing the silicon substrate 11 by etching, (E) of FIG.
As shown in, the probe portion 14, the cantilever portion 15, the support portion 1
7. The AFM cantilever 10 including the light reflecting film 16 can be obtained.

In the present embodiment, the probe portion 14
Although the cantilever portion 15 is made of silicon nitride, it can be made of other materials without any problem. Further, as the light reflection film 16, the one using a multilayer film in which gold is laminated on chrome is shown, but it is a material that is resistant to a strong alkaline etching solution generally used for etching a silicon substrate and has a high reflectance. Any material may be used as long as it is a material. For example, in addition to the above-mentioned chromium and gold multilayer film, Ti, Mo, W, Co, Ni, Pt
, Ag, etc. are considered. Further, since an arbitrary material can be selected with high accuracy, an example is shown in which the light reflection film is patterned by the lift-off method, but other formation methods may be used. Further, although the replica hole for forming the probe portion provided on the silicon substrate is formed by using the wet etching method, it may be formed by using another method such as a dry etching method using gas. Absent.

Next, a second embodiment will be described with reference to FIG. In this embodiment, as shown in FIG. 3, the probe portion 21 is made of a material different from that of the cantilever portion 22, and the probe portion 21 is provided on the back surface of the cantilever portion 22 corresponding to the bottom portion of the probe portion 21. A light reflection film 24 is provided so as to cover the bottom surface of the. In addition, in FIG. 3, reference numeral 23 denotes a support portion provided at the base of the cantilever portion 22.

Next, a method of manufacturing the AFM cantilever according to the second embodiment will be described with reference to the manufacturing process drawings shown in FIGS. First, as shown in FIG. 4A, a silicon nitride film 32 forming a cantilever portion is formed on the surface of a silicon substrate 31 having a plane orientation (100), and an opening is formed at a predetermined position where a probe portion is to be formed. A section 33 is provided. Then K
By performing wet anisotropic etching using OH or the like, as shown in FIG. 4B, a quadrangular pyramidal replica hole 34 serving as a mold of the probe portion is formed in the silicon substrate 31, and further silicon By subjecting the substrate 31 to thermal oxidation treatment, the replica hole
An oxide film 35 is formed on the surface of 34. By forming this oxide film 35, it is possible to make the tip of the probe portion sharper and prevent the tip of the probe portion from being exposed to the etching solution when the silicon substrate 31 is removed by etching. It will be possible.

Next, by depositing the base material of the probe portion on the entire surface and performing selective etching, as shown in FIG. 4C, the base material of the probe portion is formed in the replica hole 34 having the oxide film 35 formed on the surface thereof. While leaving the material, the probe portion 36 is formed, and the silicon nitride film 32 is etched into a cantilever pattern to form a cantilever portion 37. Next, as in the first embodiment, as shown in FIG. 4D, a light reflecting film 38 is formed near the tip of the cantilever portion 37 so as to completely cover the bottom portion of the probe portion 36. To do. Then, the support portion 39 made of Pyrex glass is anodically bonded to a predetermined region on the cantilever portion 37. Finally, the silicon substrate 31 is removed by etching, and further the oxide film 35 left around the probe portion 36 is removed by etching, so that the probe portion 36 and the cantilever composed of a material different from the cantilever portion 37 are formed. Part 37, support part 39,
The AFM cantilever 30 including the light reflecting film 38 is obtained.

By using the structure of the second embodiment as described above, since the probe portion 36 is not exposed to the etching solution when the silicon substrate 31 is removed by etching, the material for forming the probe portion 36. It is possible to widen the selection range of, for example, it is possible to use aluminum or the like as the material of the probe portion, which is impossible with the conventional configuration.

Next, a third embodiment will be described with reference to FIG. This embodiment is the AFM having the configuration shown in the first or second embodiment shown in FIG. 1 or 3.
In the cantilever, the magnetic film 44 is locally formed in the vicinity of the free end of the cantilever portion 41, and the light reflection film 45 is formed so as to cover the magnetic film 44. In addition, in FIG. 5, 42 is a probe part and 43 is a support part.

Next, a method of manufacturing the AFM cantilever according to the third embodiment will be described with reference to the manufacturing process drawings shown in FIGS. First, as shown in FIG. 6A, in the same manner as in the first embodiment, the probe is formed on the silicon substrate 51 in which the quadrangular pyramidal replica hole 52 serving as the mold of the probe is formed. A silicon nitride film, which is a base material of the needle portion and the cantilever portion, is deposited and is etched in a cantilever pattern shape to form a cantilever portion 54 integrally formed with a probe portion 53 at one end. Next, as shown in FIG. 6B, a magnetic film 55 is selectively formed at a predetermined position in the vicinity of the free end of the cantilever portion 54, and the optical film 55 is covered with light so as to completely cover the magnetic film 55. The reflective film 56 is formed. Next, as shown in FIG. 6C, a supporting portion 57 made of Pyrex glass is anodically bonded to a predetermined region on the cantilever portion 54, and the silicon substrate 51 is removed by etching to remove the free end of the cantilever portion 54. Magnetic film 55 near
And an AFM cantilever 50 whose surface is covered with a light reflecting film 56 is obtained.

[0027]

As described above based on the embodiments, according to the present invention, the light reflecting film is locally disposed near the free end of the cantilever portion, so that the light reflecting film is formed. Warping of the cantilever part due to film thickness fluctuations and heat fluctuations during measurement is eliminated, and AFM cantilever product stability and AFM
The measurement stability can be improved. In addition, by covering the bottom surface of the probe and the magnetic film with a light-reflecting film, the range of choice of material for the probe can be expanded to enable versatile measurement, and the magnetic film can be easily and accurately prepared. Can be formed.

[Brief description of drawings]

FIG. 1 is a cross sectional view and a top view showing a first embodiment of an AFM cantilever according to the present invention.

FIG. 2 is a manufacturing process diagram for describing the manufacturing method of the AFM cantilever according to the first embodiment shown in FIG.

FIG. 3 is a cross-sectional view showing a second embodiment of the present invention.

FIG. 4 is a manufacturing process diagram for describing the manufacturing method for the AFM cantilever according to the second embodiment shown in FIG.

FIG. 5 is a transverse cross-sectional view showing a third embodiment of the present invention.

FIG. 6 is a manufacturing process diagram for describing the manufacturing method for the AFM cantilever according to the third embodiment shown in FIG.

FIG. 7 is a manufacturing process diagram for explaining a conventional method for manufacturing an AFM cantilever.

FIG. 8 is a diagram showing a schematic configuration of a general AFM device.

[Explanation of symbols]

 1 cantilever part 2 probe part 3 support part 4 light reflection film 10 AFM cantilever 11 silicon substrate 12 replica hole 13 silicon nitride film 14 probe part 15 cantilever part 16 light reflection film 17 support part 21 probe part 22 cantilever part 23 support Part 24 Light-reflecting film 30 AFM cantilever 31 Silicon substrate 32 Silicon nitride film 33 Opening 34 Replica hole 35 Oxide film 36 Probe part 37 Cantilever part 38 Light-reflecting film 39 Support part 41 Cantilever part 42 Probe part 43 Support part 44 Magnetic Body film 45 Light reflection film 50 AFM cantilever 51 Silicon substrate 52 Replica hole 53 Probe part 54 Cantilever part 55 Magnetic film 56 Light reflection film 57 Support part

Claims (4)

[Claims] 1. An AFM cantilever characterized in that a probe portion is provided near a free end of a cantilever portion extending from a supporting portion, and a light reflecting film is locally formed near a free end of the cantilever portion. 2. The locally formed light reflecting film is provided so as to cover the bottom surface of the probe portion provided near the free end of the cantilever portion. The AFM cantilever according to item 1. 3. The magnetic film is locally formed in the vicinity of the free end of the cantilever portion, and the light reflecting film is formed so as to cover the magnetic film. AFM cantilever. 4. The AFM according to claim 1, wherein the light-reflecting film is formed of a laminated film in which gold is laminated on chromium formed by a lift-off method. Cantilever.