JP2962612B2 - Scanning microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning microscope for measuring the three-dimensional shape of a sample surface in minute units.

[0002]

2. Description of the Related Art Atomic Force Microsc
ope (hereinafter abbreviated as AFM) is 1 nm with respect to the sample surface.
A cantilever made of an elastic body that supports the probe approached to the following distance detects the force in reverse from the amount of bending that receives the force applied between the sample and the probe, and adjusts the sample so that this force is constant. By scanning the sample surface while controlling the distance between the probes, the three-dimensional shape of the surface is observed with a resolution of nm or less. (Binig et al., Physics Review Letter 56, 930 (1986)). Unlike the scanning tunneling microscope (STM), the AFM does not require the sample to have conductivity, and can observe an insulating sample, particularly a semiconductor resist surface, a biological macromolecule, and the like in the order of atoms and molecules. Application is expected.

The AFM has a probe facing the sample surface, a cantilever supporting the probe, a system for detecting the amount of bending of the cantilever due to a force from the sample surface, and a three-dimensional control of the relative position of the sample with respect to the probe. Means. The AFM normally performs observation with a single probe, and as a means for detecting the amount of bending of the cantilever supporting the probe, an optical lever method or a tunnel current method is generally used.

FIG. 3 is an explanatory diagram of an AFM for detecting a bending amount of a cantilever by an optical lever method. XYZ drive element 1
A sample 2 is fixed on the top, and a probe 3 is provided on the surface of the sample 2.
Are supported and opposed by the cantilever 4, and the cantilever 4 is supported by the lever holder 5. The light beam emitted from the light source 6 enters the cantilever 4 via the lens 7, and the light reflected by the cantilever 4 enters the two-division photodiode 8. When the cantilever 4 bends,
The position of the reflected light spot is shifted, and the position shift amount is 2
The amount of deflection of the cantilever 4 is obtained by detection by the divided photodiode 8.

FIG. 4 is an explanatory diagram of an AFM for detecting a bending amount of a cantilever by a tunnel current method. The sample 2 is fixed on the XYZ drive element 1. A probe 3 is supported by a cantilever 4 and faces the surface of the sample 2, and the cantilever 4 is supported by a lever holder 5. Behind the cantilever 4, a conductive probe 9 is provided with a piezo element 10.
Is supported by and is approaching. The position of the conductive probe 9 is controlled by the piezo element 10 so as to keep the tunnel current flowing between the cantilever 4 and the conductive probe 9 constant, and the amount of deflection of the cantilever 4 is obtained from the control amount.

[0006]

However, as described in the above-mentioned conventional example, observation by the AFM is one time.
It is done by the tip of a book. For this reason, it is difficult to observe the sample surface in a short time over a large area. As a method of solving this problem, it is conceivable to use a plurality of probes. However, in the case of using a plurality of observation probes in the AFM, the following problems occur.

(1) In detecting the bending of the cantilever,
The conventionally known optical lever method requires an adjustment jig for applying a light beam to the back surface of the cantilever, an optical component such as a lens and a mirror, and a position adjustment tool for a two-division photodiode. Further, in the tunnel current method, a mechanical configuration of a lever deflection amount detection system such as a position adjuster of the conductive probe with respect to the back surface of the cantilever is required for each probe, and the entire system becomes large and complicated.

(2) Each cantilever is warped by a variable amount, and the length of the probe is also different for each cantilever, so that the initial distance of each probe to the sample is not constant.

(3) In order to solve the above (1) and (2), the system for detecting the amount of deflection of the cantilever is simplified and integrated on the cantilever, and the drive system for each cantilever is integrated on the cantilever. At this time, since the detection system of the cantilever deflection amount and the drive system of the cantilever are adjacent to each other, noise due to the control voltage of the cantilever drive system is guided to the electrode of the deflection amount detection system of the cantilever. And correct AFM by superimposing on the detected minute generated voltage.
It is difficult to obtain an image. In addition, the field-back system for keeping the distance between the probe and the sample constant may be disturbed, and the probe may collide with the sample surface and be damaged.

An object of the present invention is to solve the above-mentioned problems,
The drive system of the cantilever and the deflection detection system are integrated, and the distance between the probe and the sample surface can be corrected independently.Furthermore, noise induced from the cantilever drive electrode to the electrode of the cantilever displacement detection system It is an object of the present invention to provide a scanning microscope having a plurality of cantilever units with a small number.

[0011]

A scanning microscope according to the present invention for achieving the above object has a structure in which a first piezoelectric layer is sandwiched between piezoelectric driving electrode layers and a second piezoelectric layer is sandwiched between piezoelectric layers. It is necessary to have a plurality of cantilever units that are sandwiched by the displacement detection electrode layers, stacked with an insulating electrode layer interposed therebetween and a shielding electrode layer interposed therebetween, and provided with a probe on the surface via the insulating layer. It is a feature.

[0012]

In the scanning microscope having the above-mentioned structure, the cantilever sandwiches one of two different piezoelectric layers with a piezoelectric drive electrode layer insulated from one another and the other with a piezoelectric displacement detection electrode layer. Since the shield electrode layer is provided between the piezoelectric displacement detection electrode layer and the piezoelectric body displacement detection electrode layer, the drive can be performed and the displacement can be detected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a perspective view of an integrated cantilever unit. The probe 12 on the cantilever unit 11 is provided on the insulating layer 13. Insulation layer 1
The Au electrode 14, the piezoelectric layer 15, and the Au electrode 16 are sequentially laminated on the back surface of the substrate 3. The Au electrode 14, the piezoelectric layer 15, and the Au electrode 16 constitute a Z-axis direction driving element 17. . Also. The insulating layer 1 is formed under the Au electrode 16.
8, a grounded Au electrode 19 and an insulating layer 20 are sequentially laminated. Further, under the insulating layer 20, an Au electrode 21, a piezoelectric layer 22, and an Au electrode 23 are sequentially laminated.
The u-electrode 21, the piezoelectric layer 22, and the Au electrode 23 constitute a Z-axis direction displacement detecting element 24. The Z-axis direction displacement detecting element 24 has a piezoelectric unimorph structure,
Detects a force acting between the sample and a sample 25 (not shown).

When the tip of the integrated cantilever unit 11 bends in the Z direction, a strain is generated in the piezoelectric layer 22 in accordance with the amount of bending dZ, and a potential difference dV is generated between the Au electrodes 21 and 23.
For example, the length of the cantilever unit 11 is set to 100 μm.
m, the width is 20 μm, and the thickness of each layer is Au electrodes 21, 2.
3 is 0.1 μm, and the piezoelectric layer 22 is 1 μm.
When the deflection dZ of the cantilever unit 11 is 1 nm, a potential difference dV of about 1 mV is generated. Therefore, this potential difference
By detecting dV, conversely, cantilever unit 1
The amount of deflection dZ of the first tip can be detected.

Further, by using the reverse of this principle, that is, in the Z-axis direction driving element 17 shown in FIG.
By applying a voltage to the piezoelectric layer 15 from the electrodes 14 and 16, within the elastic limit of the cantilever unit 11,
The cantilever unit 11 can be driven in the Z direction. Z-axis direction drive element 17 and Z-axis direction displacement detection element 2
4, an Au electrode 1 serving as a grounded shield electrode
With the provision of 9, the noise induced from the electrode of the Z-axis direction drive element 17 to the electrode of the Z-axis direction displacement detection element 24 can be reduced, and a displacement amount with a good S / N ratio can be detected. The insulating layer 13 is made of SiO _{2 having a} thickness of 1 μm.
, And ZnO is used for the piezoelectric layers 15 and 22.

The method of forming the cantilever unit 11 will be described. In this embodiment, Au is deposited by evaporation while sequentially patterning the cantilever shape on a Si substrate.
A thin film, a ZnO thin film and a SiO ₂ thin film are laminated by a sputtering method as shown in FIG. The cantilever unit 11 is formed by anisotropic etching.

Next, an atomic force microscope constituted by using a plurality of integrated cantilever units 11 will be described with reference to FIG. Each integrated cantilever unit 11 has one sample 26 fixed on the stage 25.
Are installed facing each other. A in the Z-axis direction displacement detecting element 24 of each cantilever unit 11
The outputs of the u-electrodes 21 and 23 are connected to a Z-axis direction displacement detection circuit 27, and the output of the Z-axis direction displacement detection circuit 27 is connected to a computer 28. The output of the computer 28 is a Z-axis direction drive circuit 29 and an X-axis direction scan signal circuit 3.
0, it is connected to the Y-axis direction scanning signal circuit 31 and the display device 32, and the output of the Z-axis direction drive circuit 29 is connected to the Au electrodes 14 and 16 in the Z-axis direction drive element 17, respectively. The outputs of the X-axis direction scanning signal circuit 30 and the Y-axis direction scanning signal circuit 31 are the X-axis direction driving element 33,
The X-axis direction drive element 33 and the Y-axis direction drive element 34 are connected to the Y-axis direction drive element 34, and are attached to the stage 25.

First, as an initial setting, the Z-axis direction driving element 1
7, the sample 26 and the probe 12 on each cantilever unit 11 are brought closer to each other in the Z direction to a distance of 1 nm or less. By the atomic force according to the initial distance between the probe 12 of each cantilever unit 11 and the sample 26,
A certain amount of bending occurs in each cantilever unit 11, but a Z-axis direction drive signal is applied to the Z-axis direction drive element 17 so that the distance between each probe 12 and the surface of the sample 26 is all 1 nm. The adjustment is performed by controlling the amount of deflection of the cantilever unit 11.

Thereafter, based on the scanning signal from the computer 28, the X-axis scanning signal circuit 30 and the Y-axis scanning signal circuit 31 convert the X-axis scanning signal into an X-axis driving element 33 and a Y-axis scanning signal, respectively. To the Y-axis driving element 3
4 and the sample 26 is moved in XY relative to each probe 12.
Scan in two dimensions. At this time, the depth and height of the unevenness can be detected by the Z-axis direction displacement signal output from the Z-axis direction displacement detecting element 24 of each integrated cantilever unit 11 according to the unevenness on the sample surface. The computer 28 acquires the two-dimensional distribution data of the unevenness of the sample surface in a short time and displays it on the display device 32.

The material of the probe 12 is Fe, C
If a magnetic material such as o or Ni is used, the cantilever unit 11 of the present invention can be applied to a magnetic force microscope, and the surface magnetic domain structure in a magnetic sample can be observed.

[0021]

As described above, the scanning microscope according to the present invention has the following advantages.

(1) Since a plurality of probes for observation and a plurality of cantilevers corresponding to each probe are provided, short-time observation over a large area becomes possible.

(2) The integrated configuration of the cantilever unit makes the configuration simpler than that of the optical lever method or the tunnel current method.

(3) Since the cantilever unit can be independently driven in the Z direction, it is possible to correct the variation in the distance between the probe and the sample surface due to the initial warpage of the cantilever.

(4) By providing a shield electrode between the cantilever drive system and the cantilever deflection amount detection system,
The noise induced from the cantilever drive electrode to the electrode of the cantilever displacement detecting element can be reduced, and the measurement accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an integrated cantilever unit.

FIG. 2 is a configuration diagram of an AFM.

FIG. 3 is an explanatory diagram of a conventional example.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 11 Cantilever unit 12 Probe 13, 18, 20 Insulating layer 14, 16, 19, 21, 23 Au electrode 15, 22 Piezoelectric layer 17 Z-axis direction drive element 24 Z-axis direction displacement detection element 26 Sample

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Matsuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Haruki Kawasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Ryo Kuroda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-4-350510 (JP, A) JP-A-4-320918 (JP) JP-A-63-309802 (JP, A) JP-A-3-503463 (JP, A) JP-A-3-503586 (JP, A) JP-A-3-504762 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01B 21/00-21/32 G01B 7/00-7/34

Claims (1)

(57) [Claims] 1. A first piezoelectric layer is sandwiched by a piezoelectric drive electrode layer, a second piezoelectric layer is sandwiched by a piezoelectric displacement detection electrode layer, and a shield electrode is interposed therebetween through an insulating layer. A scanning microscope comprising: a plurality of cantilever units that are stacked with layers interposed therebetween and provided with a probe on the surface via an insulating layer.