JPH04359108A - Inclination measuring mechanism - Google Patents

Abstract

PURPOSE:To detect the inclination angle between a probe surface and a sample surface. CONSTITUTION:When an inclination angle is detected, a probe 3 is made to approach a sample 2 by a course driving part 7 for probe, and a certain voltage is applied between the sample 2 and the probe 3 by a voltage controller 4, and a tunnel electric current flows. An electric current detecting circuit 5 detects the tunnel electric current through the vibration in the vertical direction to the probe 3 by a fine driving part 6 for probe. When the probe surface and the sample surface are not in parallel, the tunnel electric current varies during the vibration of the probe 3, therefore the distance between the sample 2 and the probe 3 is calculated by a distance detecting circuit 9, and further the inclination angle is calculated by an inclination angle calculating circuit 11, and the inclination angle is corrected by a driving part control circuit 10 and the course driving part 7 for probe. After the correction, the image information of the sample 2 is read out by using the tunnel electric current.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt measuring mechanism in an apparatus that utilizes, for example, a tunnel current flowing between a sample and a probe.

0002

BACKGROUND OF THE INVENTION In recent years, a scanning tunneling microscope (hereinafter referred to as STM) that can directly observe the electronic structure on and near the surface of a material has been developed [G. Binnig et al. ，
Helvetica Physica Acta, 55
, 726 (1982)], it has become possible to observe real space images with high resolution regardless of whether they are single crystal or amorphous. This STM has the advantage of being able to perform measurements with low power without causing almost any damage to the sample material due to the current.Furthermore, it can operate not only in ultra-high vacuum, but also in the atmosphere and in solutions, and can be applied to a variety of materials. Therefore, wide-ranging applications are expected.

[0003] STM utilizes the phenomenon that a tunnel current is generated when a voltage is applied between a metal probe and a conductive sample and the probe is brought close to a distance of about 1 nm. recently,
For example, JP-A-63-161552, JP-A-16155
As disclosed in Publication No. 3, many proposals have been made to apply this STM principle to configure information processing apparatuses mainly for ultra-high density recording and reproduction. That is, information is recorded by physically deforming the recording medium, which corresponds to the sample, using a probe electrode, which corresponds to the STM probe, or by changing the electronic state of the medium surface to generate a low electrical resistance area. It is said that by using a method of reproducing information from recorded bits using a tunnel current flowing between the two, it is possible to record and reproduce large-scale information at a high density on the order of molecules or atoms.

0004

[Problems to be Solved by the Invention] In the above-mentioned information processing device, the probe is swept close to the sample surface and image information is obtained from changes in tunneling current. The probe surface must be held perpendicular to the sample surface, that is, the probe surface must be held parallel to the sample surface, especially when the probe sweeps over a wide area,
When a large number of probes arranged in parallel are used simultaneously to improve information processing speed, their parallelism is more strictly required.

An object of the present invention is to provide an inclination measurement mechanism that detects the inclination angle between the probe surface and the sample surface, corrects the inclination angle to make them parallel, and allows the probe to approach the sample. It's about doing.

[0006]

[Means for Solving the Problems] A tilt measurement mechanism according to the present invention for achieving the above object includes a probe that detects information from a sample, and a probe that vibrates the probe at one location within the surface of the sample. The apparatus is characterized by comprising: a vibration means; and an inclination angle calculation circuit that calculates an inclination angle between the probe and a sample surface from a signal detected by the probe while vibrating the probe by the probe vibration means. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the illustrated embodiments. FIG. 1 shows a configuration diagram of a first embodiment in which the probe approach mechanism according to the present invention is applied to STM.A probe 3 is placed above a sample 2 placed on a fixed base 1. The sample 2 and the probe 3 are provided with a voltage control device 4,
A current detection circuit 5 is connected, and the probe 3 is connected to a probe fine drive unit 6, which will be described later, and a probe coarse drive unit 7, which is constituted by a stepping motor and performs a wide range operation. On the other hand, a sequence control circuit 8 is provided to control the entire device, the output of the current detection circuit 5 is connected to the sequence control circuit 8, and the output of the sequence control circuit 8 is connected to the voltage control device 4,
The output of the distance detection circuit 9 is connected to the drive control circuit 10 and the tilt angle calculation circuit 11, and the output of the drive control circuit 10 is connected to the probe fine drive unit 6. , the probe drive unit 7, and the tilt angle calculation circuit 11, and the output of the tilt angle calculation circuit 11 is connected to the control circuit 8.
It is connected to the.

FIG. 2 shows an enlarged view of the probe 3 and the probe fine drive section 6. The probe fine drive section 6 has an electrode 6 on a cylindrical piezoelectric element 6a.
x, 6y, and 6z, a voltage is applied to the electrode 6z to control the position of the probe 3 in the z-axis direction, and a voltage is applied to the electrode 6x and the electrode 6y to control the x of the probe 3. It performs position control in the axial and y-axis directions, and the probe 3 is movable within a range of 0.2 μm in the z direction and 0.1 μm in the x and y axes directions (G. Binnig et al. ，
Rev. Sci. Instrument. ,57(8),Au
gust, 1986, PP1688).

When the probe 3 is brought closer to the sample 2 by the probe fine drive section 6 while applying a constant voltage between the sample 2 and the probe 3 by the voltage controller 4, a tunnel current flows between the two. start. The magnitude of this tunnel current depends on the distance between the two. For example, in Figure 3, HOPG (
Graph showing the relationship between the relative position of the probe 3 in the z-axis direction with respect to the sample 2 and the tunneling current value when using a cut platinum wire with a diameter of 1 mm as the probe 3. The distance between the probe 3 and the sample 2 is 5.
It can be seen that when changing by angstrom, the tunnel current changes by about 4 orders of magnitude. Therefore, if this information is stored in advance in the distance detection circuit 9 for the sample 2 and probe 3 to be used, the distance between them can be calculated based on the tunnel current detected by the current detection circuit 5. can.

When measuring the inclination angle, the output of the probe fine drive unit 6 is applied to the electrode 6y, and the probe 3 is vibrated with a constant amplitude in the y-axis direction as shown in FIG. 4 to measure the tunnel current. When the y-axis of the probe 3 is parallel to the surface of the sample 2, the probe 3
Even during vibration, the distance between the probe 3 and the sample 2 is constant and the tunneling current value does not change, but if they are non-parallel, the tunneling current value will change.

[0011] Figure 5 shows the tunnel current measured by using the same sample 2 and probe 3 as in the measurement of the graph in Figure 3, and by vibrating the probe 3 in the y-axis direction by ±0.05 μm from the reference position. These are the actual measurement results. From this figure, 0 in the y-axis direction of the probe 3
．． The tunnel current changes by about four orders of magnitude with a movement of 10 μm, and it can be seen from FIG. 3 that the amount of change in tunnel current corresponds to a change in the position of the probe 3 in the z-axis direction of 5 angstroms.

Therefore, as shown in FIG. 6, the inclination angle θ between the surface of the sample 2 and the y-axis of the probe 3 in this case is calculated by the following equation. θ=Tan-1 (5 [angstroms]/0.
1 [μm]) = Tan-1 (1/200) =
0.29°

The actual processing within the apparatus is controlled by a control circuit 8. First, a drive unit control circuit 10 causes the probe 3 to approach the sample 2, and a probe fine drive unit 6 moves the probe 3 to y. While vibrating in the axial direction, a constant voltage is applied between the sample 2 and the probe 3 by the voltage control device 4, causing a tunnel current to flow between them. This tunnel current is detected by the current detection circuit 5, the distance between the two is detected by the distance detection circuit 9, and the inclination angle is calculated by the inclination angle calculation circuit 11. This inclination angle is input to the control circuit 8, which drives the drive unit control circuit 10, and the probe fine drive unit 6 and coarse probe drive unit 7 correct the inclination angle of the probe 3. . The method of reading the image information of the sample 2 after correction is the same as in the conventional example.

By performing this inclination angle correction, when the sample 2 was scanned over a wide area after adjusting the parallelism between the sample 2 and the probe 3, it was possible to measure the tunnel current in the entire 1 mm square area. Ta. In the case of no adjustment, it was 40 μm square. In the above description, the tunneling current was measured by vibrating the probe 3 in the y-axis direction, but the probe 3 may also be used in the x-axis direction without any problem, or may be rotated in a circular motion on the xy plane.

FIG. 7 shows a cantilever probe 12 according to a second embodiment. As shown in the cross-sectional view of FIG. 8, the cantilever 12A has two divided electrodes 12a, 12 from the top.
b, piezoelectric body 12c, intermediate electrode 12d, piezoelectric body 12e, 2
It is constituted by a piezoelectric bimorph in which divided electrodes 12f and 12g are laminated. The cantilever 12A is fixed to a portion of the silicon substrate 12B removed by anisotropic etching and is supported in a cantilever manner, and the probe 3 is attached to the upper end of the cantilever 12A. In other words, the silicon substrate 12
On B, there are the probe 3 and the two-part electrodes 12a, 12b, 12f.
, 12g, and lead electrodes 12h to 12n connected to the intermediate electrode 12d are formed. This cantilever type probe 12 is used by being incorporated into the apparatus shown in FIG.

Movement of the probe 3 in the xz-axis directions is performed by controlling the voltages applied to the extraction electrodes 12i to 12m. For example, the right regions of the piezoelectric bodies 12c and 12e are contracted and the left regions are expanded, and the probe 3 is moved in the x-axis direction as shown in FIG. Alternatively, although not shown, it is possible to move the probe 3 in the z-axis direction by, for example, contracting the piezoelectric body 12c and expanding the piezoelectric body 12e. When detecting the inclination angle, the left and right regions of the piezoelectric bodies 12c and 12e are alternately contracted and expanded to vibrate the probe 3 in the x-axis direction, and the tunnel current is measured using the extraction electrode 12h. The laminated structure of the cantilever 12A is, for example, T. R. Albre
cht, Proseedingus of 4th I
international conference o
n STM/STS, '89, S10-2.

[0017] The piezoelectric material has a width of 150 μm and is made using a 0.3 μm thick ZnO electrode and 0.1 μm Au.
For a cantilever 12A with a length of 300 μm, the applied voltage ±
It has been confirmed through experiments that at 5V, the displacement in the x-axis direction is ±130 angstroms, and vibration with a width of 260 angstroms is possible. In addition, HOPG was added to sample 2.
In an experiment using Ag paste for the probe 3, a change of about two orders of magnitude in the tunneling current value was measured, and the inclination angle θ=
0.4° was detected.

FIG. 10 is a block diagram of a third embodiment in which the present invention is applied to an information processing apparatus, and the same reference numerals as in FIG. 1 indicate the same members. In this embodiment, as shown in FIG. 11, a recording/reproducing head 14 is used in which a plurality of cantilever probes 12 described in the second embodiment are arranged side by side on a base 13 in a cantilevered manner. There is. A recording medium 15 used as a sample has a base electrode 1 on the bottom surface for applying a voltage.
6 is attached and held by a recording medium holder 18 fixed to the tilt correction mechanism 17.
4 is, for example, a stepping motor, a differential micrometer,
It is fixedly installed in a coarse movement drive section 19 composed of mechanisms such as a voice coil and an inch form.

Although only one probe 3 is shown in FIG. 10, each probe 3 and recording medium 15 are equipped with a voltage control device 4,
The current detection circuits 5 are connected to each other, the voltage control device 4 is connected to the CPU 21 with or without the data modulation circuit 20, and the current detection circuit 5 is connected to the distance detection circuit 9, and the voltage control device 4 is connected to the CPU 21 via the data demodulation circuit 22. It is connected to the CPU 21. Further, the distance detection circuit 9 is similar to the first embodiment,
CPU 21 with or without inclination angle calculation circuit 11
Further, the tilt angle calculation circuit 11 is connected to the tilt correction mechanism 17 via the tilt angle correction circuit 23, and the drive unit control circuit 10 is connected to the CPU 21 and the plurality of cantilever probes 12 of the recording/reproducing head 14. The extraction electrode is connected to the coarse movement drive section 19.

The method of detecting the inclination angle is exactly the same as that in the second embodiment, and the coarse movement drive unit 19 moves the probe 3 to the recording medium 1.
5, a constant voltage is applied between them, the tunnel current is galvanized by the current detection circuit 5 while the probe 3 is vibrated in the x-axis direction, and the tunnel current is detected by the distance detection circuit 9 and the inclination angle calculation circuit 11. Calculate the tilt angle. This tilt angle is input to the tilt angle correction circuit 23, and the tilt correction mechanism 17 is moved to perform correction. The tilt correction mechanism 17 includes, for example, the cylindrical piezoelectric element or the recording medium holder 1 shown in FIG.
Laminated piezoelectric elements attached to the four corners of 8 are suitable;
Inclination angle detection only needs to be performed for at least one probe 3.
It is not necessary to perform this for all probes 3. Furthermore, if detection is performed multiple times during data recording and reproduction, it is possible to cope with the case where the inclination angle changes over time due to external vibrations, thermal expansion of the sample 2, etc.

The well-known method described in the conventional example can be used for recording and reproducing data. During recording, the probe 3 is brought close to the recording medium 15 at a predetermined interval by the coarse movement drive unit 19 to scan the xy plane, and the pulse voltage modulated by the data modulation circuit 20 is applied to the probe 3 by the voltage control device 4.
When applied between the recording medium 15, a tunnel current flows between the two. This tunneling current applies local physical deformation to the recording medium 15 or changes the electronic state on the surface, forming a portion with low electrical resistance and recording a data string. During playback, when an xy plane scan is performed along the data string while applying a constant voltage between the probe 3 and the recording medium 15 that are close to each other, the pulse voltage changes the resistance at the recorded location. A tunnel current is detected, which is demodulated by the data demodulation circuit 22 and transmitted to the CPU 21.

It should be noted that the surface of the recording medium 15 is not necessarily flat within the sweep range of the probe 3, and generally has minute irregularities unrelated to the data. Therefore, the distance detection circuit 9 calculates a signal from which the high frequency vibration component due to the presence or absence of information bits is removed from the signal of the current detection circuit 5, and maintains the signal value constant. The cantilever is controlled to move in the z-axis direction via the CPU 21 and the distance detection circuit 9 so as to keep the distance constant.

The material of the recording medium 15 has a surface shape that is deformed into a convex shape by a tunnel current (Staufen, A.
ppl. Phys. Letters, 51(4), 27
, July, 1987, pp244) or concavely deformed (Heinzelmann, Appl. Phys.
．． Letters, Vol. 53, No. 24, Dec
．． , 1988, pp. 2447) are known as metals, semiconductors, oxides, thin films of materials, etc. In addition, as a device for recording by changing the electrical characteristics, there is
-Langmuir-Blodgett method (LB method) as disclosed in Publications No. 161552 and No. 161553
For example, on a quartz glass substrate, 50 angstroms of Cr is deposited as the base electrode 16 by a vacuum mounting method, 300 angstroms of Au is deposited thereon by the same method, and then SOAZ is deposited by the LB method. (Squarylium-bis-6-
For example, a four-layer stack of octyl azulene) may be used. The pulse voltage applied during recording depends on the recording medium 15 used.
For example, a rectangular pulse voltage with a voltage of 3 V and a width of 50 nS is appropriate, although the voltage applied during reproduction is lower than the recording voltage, such as a DC voltage of 200 mV, although it varies depending on the voltage.

Although all of the embodiments described above use tunnel current, they can also be applied to devices using other physical quantities such as atomic force, capacitance, magnetic flux, and magnetic force.

[0025]

As explained above, the inclination measurement mechanism according to the present invention measures the inclination of the probe surface and the sample surface from the tunnel current detected while vibrating the probe in a plane parallel to the plane orthogonal to the probe. Since the angle is calculated, image information on the sample can be accurately obtained by, for example, approaching the probe to the sample after correcting this inclination angle.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a perspective view of a probe fine drive unit and a probe.

FIG. 3 is a graph of the relationship between the probe z-axis relative position and tunnel current.

FIG. 4 is an explanatory diagram of a method of vibrating the probe.

FIG. 5 is a graph of the relationship between the probe y-axis position and tunneling current.

FIG. 6 is an explanatory diagram of an inclination angle calculation method.

FIG. 7 is a perspective view of a cantilever probe according to a second embodiment.

FIG. 8 is a cross-sectional view.

FIG. 9 is an explanatory diagram of the moving direction of the probe.

FIG. 10 is a configuration diagram of a third embodiment.

FIG. 11 is a perspective view of a recording/reproducing head.

[Explanation of symbols]

2 Sample 3 Probe 4 Voltage control device 5 Current detection circuit 6 Probe fine drive section 7 Probe rough drive section 9 Distance detection circuit 10 Drive unit control circuit 11 Inclination angle calculation circuit 12 Cantilever probe 14 Recording/playback head 15 Recording medium 17 Tilt correction mechanism 19 Coarse movement drive section 23　Tilt angle correction circuit

Claims (1)

[Claims] [Claim 1] A probe that detects information from a sample;
A probe vibrating means vibrates the probe at one location within the sample surface, and an inclination angle between the probe and the sample surface is calculated from a signal detected by the probe while the probe is vibrated by the probe vibrating means. An inclination measuring mechanism characterized by having an inclination angle calculation circuit.