JPH1073607A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning probe microscope whose configuration around a sample is hardly limited and which is provided with a cantilever tip whose structure is hardly influenced by humidity or the like. SOLUTION: A reflecting face 1d is formed at the free end part of a cantilever part 1b at a cantilever tip 1, an optical waveguide 2 which reflects light to the reflecting face 1d and which transmits reflected light is formed on a pedestal 1c, and the displacement of a probe 1a is detected by using the reflecting face 1d and the optical waveguide 2. By this constitution, a displacement detector can be arranged in a place at a distance from a sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanning probe microscope.

[0002]

2. Description of the Related Art FIG. 1 shows the configuration of an AFM (atomic force microscope) which is one of the scanning probe microscopes. This A
The FM is composed of a cantilever L having a tip with a small radius of curvature at the tip and an optical system D for detecting the displacement of the cantilever L. This is a microscope that employs a so-called optical lever method that utilizes the point where the cantilever bends due to the force acting between the needle and the optical system D to detect the bending of the cantilever.

In this type of microscope, in addition to the above-described displacement detection method, an attempt has been made to integrate a cantilever and a displacement detection system. For example, there is a type in which a piezoresistive element is formed in a silicon cantilever and the displacement of the cantilever is detected from a change in the resistance value (Inter).
national Conference on Solidstate Sensors and Actu
ators, 1991, Tech.dig.pp448-451).

[0004]

By the way, in the case of the structure shown in FIG. 1, it is necessary to dispose a displacement detector including a semiconductor laser and a photodiode near the cantilever and the sample. In the case of performing measurement in, for example, the detection system also needs to be placed in the vacuum chamber,
There is a problem that the configuration around the sample is limited. In addition, the optical system requires precise optical axis adjustment, and there is a problem that complicated optical axis alignment must be performed every time the cantilever is replaced.

On the other hand, when a cantilever chip in which a piezoresistive element is formed in a cantilever portion is used, the resistance of the piezoresistive element is not limited by the above-described configuration, but the resistance of the piezoresistive element is measured in an environment (eg, humidity). And there is a problem that a measurement error occurs. There is also a problem that the material of the cantilever is limited to a semiconductor such as silicon.

The present invention has been made in view of such circumstances, and provides a scanning probe microscope provided with a cantilever tip having a structure in which the configuration around the sample is hardly limited and hardly affected by humidity or the like. The purpose is to:

[0007]

In order to achieve the above object, a scanning probe microscope according to the present invention employs a cantilever tip used for measurement as shown in FIGS.
It comprises a cantilever portion 1b and a pedestal 1c for supporting the cantilever portion. A free surface of the cantilever portion 1b is provided with a probe 1a and a reflection surface 1d for reflecting light from the pedestal 1c side, and an optical waveguide ( An SiO ₂ waveguide 2 is formed so as to face the reflection surface 1 d, and the displacement of the probe 1 a is detected using the reflection surface 1 d and the optical waveguide 2.

In the above configuration, the light source and the light source
When the detector is connected, the reflecting surface 1 of the cantilever chip 1
d can be irradiated with light, and the amount of reflected light can be detected by a detector.

Here, in the above configuration, when the probe 1a receives an attractive force or a repulsive force from atoms on the sample surface and the cantilever portion 1b bends, the reflecting surface 1d formed on the cantilever portion 1b responds to the stress. The angle changes, and the amount of reflected light incident on the optical waveguide 2 changes. Therefore, when light is emitted from the optical waveguide 2 to the reflecting surface 1d and the reflected light is transmitted to a detector outside the chip by the optical waveguide 2 and the light amount is detected, the deflection of the cantilever portion 1b, that is, the probe is obtained from the detected value. 1a can be known.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, the scanning probe microscope of this embodiment is similar to the known microscope shown in FIG.
It is composed of a cantilever chip 1 having a probe, a stage for scanning the sample S, and the like. The structure of the cantilever chip 1 is characteristic.

That is, the cantilever tip 1 of this example
Is a tip provided with a cantilever portion 1b, a pedestal 1c for supporting the same, and a probe 1a provided at a free end of the cantilever portion 1b, as shown in FIGS. Is formed with a reflection surface 1d for reflecting light from the pedestal 1c side. In addition, the SiO.sub.
₂ waveguide 2 are formed opposite to the reflecting surface 1d, further to the cantilever chip 1, V grooves 1e having the shape shown in FIG. 4 to the rear side SiO ₂ waveguide 2 are machined.

In the above chip structure, the reflecting surface 1d and the SiO 2
_Second waveguide end face 2 (light emitting-incident end face) 2a and is substantially parallel to each other, the optical axes of the SiO ₂ waveguide 2 matches the center of the reflecting surface 1d. V-groove 1e of cantilever tip 1
Is processed so that the optical axis of the optical fiber F coincides with the optical axis of the SiO ₂ waveguide 2 with the optical fiber F placed.

In this embodiment, one end of an optical fiber F is disposed in a V groove 1e formed in the cantilever chip 1, and a light source / detector (not shown) is connected to the other end of the optical fiber F. Then, the light from the light source is
Through the optical fiber F to the reflecting surface 1d.
It is configured to lead to the detector through

The output of light from the light source to the waveguide and the separation of reflected light from the waveguide to the detector are performed using a half mirror or an optical switch. In the above configuration, when the cantilever portion 1b is not bent, the reflecting surface 1d
All the light reflected by the light enters the SiO ₂ waveguide 2, but when the cantilever portion 1b is bent, the light incident on the SiO ₂ waveguide 2 changes due to a change in the angle of the reflection surface 1d. The amount of light transmitted to the detector via F changes according to the amount of bending of the cantilever portion 1b.

Therefore, if the amount of light transmitted to the detector is measured, the measured value becomes information indicating the deflection of the cantilever portion 1b, that is, the displacement of the probe 1a, and the irregularities on the sample surface can be known from the measured value.

Here, in the above embodiment, the optical adjustment of the detection system can be easily performed only by aligning the optical fiber F bonded to the detector with the V groove 1e formed in the cantilever chip 1. This eliminates the need for complicated optical axis alignment, which is conventionally required every time the cantilever chip 1 is replaced.

Further, since the cantilever chip 1 is connected to the light source / detector provided outside using the optical fiber F, it is not necessary to dispose the light source / detector near the cantilever chip 1. As a result, the structure around the sample is not restricted, and a large area sample can be easily measured.

Next, the procedure for manufacturing the cantilever chip 1 having the structure shown in FIGS. 2 and 3 will be described below with reference to the steps shown in FIG.
This will be described with reference to (6). (1) First, SOI wafer 11 (Silicon on Insulator;
A wafer having an oxide film layer 11a in silicon) is used as a material.

(2) An oxide film is formed on the surface of the wafer 11,
This is patterned using a photolithography technique, and the wafer 11 is etched using the patterned oxide film 12 as a mask to form a probe 1a. Here, dry etching (RIE; reactive ion etching) is used, but wet etching using KOH or the like may be used, or a combination thereof.

(3) An oxide film is formed on the surface of the wafer 11,
This is patterned using a photolithography technique at a portion where the reflection surface is to be formed.
The wafer 11 is etched using the mask 3 as a mask to form the reflection surface 1d. Here, dry etching (RI
E) is used.

(4) An oxide film is formed on the surface of the wafer 11,
After patterning the V-groove formation portion using photolithography, the silicon film is anisotropically etched using the oxide film 14 as a mask, thereby forming the V-groove 1e.
To form

(5) A portion to be used for the waveguide is patterned by photolithography, and the oxide film 14 is etched to form the SiO ₂ waveguide 2. Here, wet etching using BHF (buffered hydrofluoric acid) or the like is used for etching the oxide film, but dry etching may be used.

(6) After patterning into a cantilever shape using the photolithography technique, only the portion to be the pedestal 1c of the cantilever chip 1 on the back side of the wafer 11 is covered with an oxide film (not shown). Etching is performed from the back surface of the wafer 11 to form the cantilever portion 1b.

In the above steps, a reflecting surface 1d is formed on the free end of the chip having the structure shown in FIGS. 2 and 3, ie, the cantilever portion 1b, and light is transmitted to the reflecting surface 1d and reflected light is transmitted. The cantilever chip 1 having the structure in which the SiO ₂ waveguide 2 is formed on the base 2 is completed.

In the above embodiment, the SOI wafer is used as a material. However, the present invention is not limited to this. For example, a wafer in which an n-type layer is epitaxially grown on a p-type silicon substrate or a surface layer of a p-type silicon substrate may be used. A wafer in which an n-type layer is formed by diffusion may be used as a material for producing a chip. In this case, an electrochemical etching stop technique (IEEE, Transactionson Electron Devices vol. 36, N
o.4, 1989) to form a cantilever portion.

The material of the cantilever chip is not limited to silicon, but may be another semiconductor material, an insulating material such as a silicon nitride film or a silicon oxide film, or various materials such as a metal.

In the above embodiment, the reflecting surface 1d is formed independently of the probe 1a of the cantilever tip 1. However, for example, as shown in FIG. ) May be formed thereon.

In the above embodiment, the reflection surface 1d is formed by utilizing the mirror surface of silicon. However, a film having a high reflectance is formed on the end face of the projection or the like by a technique such as sputtering film formation. A reflective surface may be formed.

In the above embodiment, the same waveguide is used for the light incident on the reflection surface 1d and the transmission of the reflected light. However, as illustrated in FIG. 7, the light incident on the reflection surface 1d is used. And the reflected light from the waveguides 102a and 102b, respectively.
May be configured to be transmitted. When such a configuration is employed, the degree of freedom in the arrangement of the light source and the detector is increased, and each of the arrangements is facilitated. Also, a half mirror or a half mirror for separating the output of light from the light source to the waveguide and the reflected light Since an optical switch or the like is not required, there is an advantage that the configuration of the optical system is simplified.

In the above embodiment, the waveguide formed by the oxide film and the light source or the detector are connected by the optical fiber using the V groove, but the present invention is not limited to this. It is also possible to adopt a form in which the waveguide formed by the above is extended to the end face of the chip and an optical fiber is directly bonded to the end face of the waveguide.

In the present invention, the material of the waveguide formed on the cantilever chip is not limited to an oxide film (SiO ₂ ), but may be another material generally used in the field of optical transmission.

As another method of forming the waveguide, for example, techniques such as PVD and CVD can be mentioned.

[0033]

As described above, according to the scanning probe microscope of the present invention, a reflecting surface is formed at the free end of the cantilever portion of the cantilever tip, and light irradiation to the reflecting surface and transmission of reflected light are performed. An optical waveguide for performing the measurement is formed on the pedestal, and the displacement of the probe is detected by using the reflection surface and the optical waveguide. Since it is only necessary to position the optical axis with respect to the wave path, the optical axis alignment is simplified. Compared to using a cantilever tip with a piezoresistor in the cantilever part, it is less susceptible to the effects of humidity, etc., and allows stable sample observation.Moreover, the probe, reflective surface, and conductive material are formed on the cantilever tip. Since only the waveguide is used and the formation of the piezoresistive layer and the like are unnecessary, there is an advantage that the material of the cantilever portion is not limited to a semiconductor such as silicon and another material such as an insulator or a metal can be used.

In the scanning probe microscope of the present invention, if an optical fiber is used to connect the optical waveguide formed on the cantilever chip to a light source / detector provided outside, the light source / detector can be separated from the cantilever chip. Can be arranged at different positions, thereby further increasing the degree of freedom of the configuration around the sample, so that a large area sample can be easily measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of the structure of a scanning probe microscope (AFM).

FIG. 2 is a longitudinal sectional view schematically showing a structure of a cantilever tip used in the embodiment of the present invention.

FIG. 3 is a plan view of the cantilever chip.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a view for explaining a method of manufacturing the cantilever chip 1 shown in FIG. 2;

FIG. 6 is a diagram showing a modification of the cantilever tip used in the embodiment of the present invention.

FIG. 7 is a view showing still another modified example of the cantilever tip used in the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 cantilever tip 1a probe 1b cantilever part 1c pedestal 1d reflecting surface 2 SiO ₂ waveguide F optical fiber

Claims (1)

[Claims] 1. A cantilever tip having a probe, and a mechanism for relatively moving a probe of the tip and the sample in a two-dimensional direction, and detecting a displacement of the probe during the moving process to detect a sample surface. In the microscope for obtaining measurement information of the microstructure of the above, the cantilever tip is composed of a cantilever portion and a pedestal supporting the cantilever portion, and the free end of the cantilever portion is formed with the probe and a reflection surface for reflecting light from the pedestal side. And a light guide is formed on the pedestal so as to face the reflection surface, and the displacement of the probe is detected by using the reflection surface and the light guide. Probe microscope.