JPH06241780A - Scanning tunneling microscope, atomic force microscope, and machining device using them - Google Patents

Abstract

PURPOSE:To provide a scanning microscope having a wide measuring dynamic range and high controllability by providing one or more electrostatic drive electrodes on both sides of a beam-like structure respectively vertically to the scanning plane. CONSTITUTION:The tunnel current between a sample 110 and a probe 109 is detected by a tunnel current detecting unit 112, the probe 109 is moved near to the conducting sample 110 by a Z-direction distance control mechanism, the probe 109 is fixed so that the current of the probe 109 is kept constant at 10 pA and the Z-direction distance between a substrate 101 and the sample 110 is not changed, and the substrate 101 is XY-scanned in parallel with the sample surface. The voltage applied across an electrode 102 and a cantilever 104 or the voltage applied across an electrode 108 and the cantilever 104 is adjusted respectively so that the tunnel current is kept constant at 10 pA by a cantilever drive unit 111. When the sample surface has a projection, voltage is applied, and the probe 109 is displaced to the substrate 101 side. When the sample surface has a recess, the probe 109 is displaced to the sample 110 side respectively, the distance between the sample surface and the probe 109 is kept constant, and the surface shape of the sample 110 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a scanning tunneling microscope (hereinafter abbreviated as STM) and an atomic force microscope (hereinafter AF).
The present invention relates to a scanning probe microscope (hereinafter abbreviated as M) (hereinafter abbreviated as SPM) and a processing apparatus using them.

[0002]

2. Description of the Related Art In recent years, an STM capable of directly observing the electronic structure of surface atoms of a conductor has been developed by Gie Winig et al. (Fervetica Physika Actor, 55, 726 (1
982). ), SPM device that obtains various information by scanning a probe with a sharp tip, and microfabrication using SPM for the purpose of exerting electrical, chemical or physical action on the substrate. Research and development of technology is being conducted. Furthermore, a semiconductor processing technology and a micromechanics technology have been used to develop, for example, a compact SPM device in which a probe is formed on a beam formed of a thin film.

As a method of driving the beam, for example, a piezoelectric type in which the beam has a piezoelectric bimorph structure, or a voltage is applied to the beam itself or an electrode formed on the beam and an electrode formed on a substrate to perform static There is an electrostatic type that displaces a beam by applying an electric attraction force.

[0004]

The above electrostatic type has a characteristic that the structure is simple because the beam is moved by the Coulomb attractive force between the beam and the counter electrode. However, Coulomb attraction can move the beam and the counter electrode only in one direction about the axis (Z axis). That is, only the displacement in the counter electrode direction (for example, + Z direction) can be obtained within the original Z-axis degree of freedom of the beam. Therefore, conventionally, a ± V displacement of the probe is obtained by applying a voltage of V _B ± ΔV volt with reference to a state where a certain bias V _B is applied to the counter electrode to displace the beam to some extent. It was Even in this case, there is a drawback that the dynamic range of the Z-axis displacement cannot be increased because only one of the Z-axis degrees of freedom that the beam originally has can be used.

This dynamic range can be easily increased by increasing the length of the beam.
It is disadvantageous for device integration and speedup.

Further, since the Z-axis displacement amount of the beam is proportional to the square of the voltage applied to the beam and the counter electrode, there is a drawback that it is non-linear with respect to the voltage and the controllability is poor. These drawbacks are, for example, when the STM observation is performed while keeping the tunnel current flowing between the sample and the probe constant, when the sample surface has a deep concave region or a high convex region, the beam displacement is insufficient. It is not possible to observe the exact unevenness,
The probe cannot follow the abrupt surface shape change, which has been a cause of hindering the speeding up of the device.

Further, in the AFM measurement for converting the amount of change in the electric capacity between the counter electrode and the beam into the unevenness, the resolution for the amount of change is reduced particularly in a region having a small electric capacitance (for example, a deep concave region). The exact surface shape could not be obtained.

The present invention has been made in view of the drawbacks of the above-mentioned prior art, and has a wide dynamic range of measurement and improved controllability. A scanning probe microscope such as a scanning tunnel microscope or an atomic force microscope, An object is to provide a processing device using them.

[0009]

Means for Solving the Problems and Actions The present invention, which has been made to achieve the above-mentioned object, firstly, a probe provided on a conductive beam-like structure is made to approach a sample surface for scanning. In the scanning tunneling microscope, at least one electrostatic drive electrode is provided on each side of the beam-shaped structure so as to sandwich the beam-shaped structure in a direction perpendicular to the scanning surface. Second, it is a scanning tunneling microscope that detects the capacitance of a beam-like structure in an atomic force microscope that scans by contacting the probe provided on a conductive beam-like structure with the sample surface. The atomic force microscope is characterized in that at least one electrode is provided on each side of the beam-like structure so as to sandwich the beam-like structure in a direction perpendicular to the scanning plane. Third, a conductive beam-like shape provided with the probe. It is the said 1st or 2nd microscope characterized by having a plurality of structures, and 4thly, among the microscopes in any one of the said 1st-3rd, at least 2 types of microscopes are one apparatus. Fifthly, there is provided a processing apparatus characterized by using the microscope described in any one of the first to fourth above for processing a sample surface.

According to the first aspect of the present invention, it is possible to drive the beam-shaped structure in both ± directions of the axis (Z axis) perpendicular to the scanning surface without applying a bias to the electrostatic drive electrode. That is, + Z displacement is obtained by applying a voltage between the electrode in the + Z direction and the beam-like structure to the conductive beam-like structure, and between the electrode in the −Z direction and the beam-like structure. -Z by applying voltage
The displacement is obtained.

As a result, the Z-axis freedom of the beam-like structure can be fully utilized and the dynamic range of measurement is expanded. Further, by simultaneously applying a voltage to each electrode, the position controllability of the beam-like structure can be improved, which contributes to faster and more reliable surface observation.

According to the second aspect of the present invention, the electrode having a shorter distance from the beam-like structure at the time of AFM measurement, that is, the one having a larger capacitance is selected, and the change in capacitance is observed and Z By making the displacement, it becomes possible to secure high resolution regardless of the unevenness of the sample surface.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples.

Embodiment 1 In this embodiment, an electrostatic drive type STM device of the present invention will be described with reference to FIG.

FIG. 1 is a conceptual diagram schematically showing the device and sample prepared in this example. In this device, the electrostatic drive electrode 102 made of a conductive film, the insulating spacer 103, and the conductive cantilever 10 are provided on the surface of the insulating substrate 101.
4. The thin insulating film 105, the tunnel current wiring 106, the insulating spacer 107, and the electrostatic drive electrode 108 made of a high-rigidity conductor were sequentially formed, and then the probe 109 was formed at the tip of the cantilever 104. At this time, the electrode 102 and the cantilever 1
04 and the electric capacity formed by the electrode 108 and the cantilever 1.
It was manufactured so that the electric capacity formed by 04 is equal to the electric capacity formed by 04.

The surface of the sample 110 is observed by the tunnel current detection unit 112 while detecting the tunnel current flowing between the sample 110 and the probe 109, and the probe 109 is placed on the conductive sample 110 at a distance (not shown) (Z direction). ) It was approached by the control mechanism. When the current flowing through the probe 109 became constant at 10 pA, the distance between the substrate 101 and the sample 110 (Z
(Direction) was fixed so as not to change, and the substrate 101 was scanned in XY parallel to the sample surface. At this time, the voltage applied between the electrode 102 and the cantilever 104 or between the electrode 108 and the cantilever 104 was adjusted by the cantilever driving unit 111 so as to keep the tunnel current constant at 10 pA. That is, when there is a convex portion on the sample surface, a voltage is applied between the electrode 102 and the cantilever 104 to apply the probe 1
09 to the substrate 101 side, and if there is a recess, electrode 1
The voltage between 08 and the cantilever 104 was applied to displace each to the sample 110 side, thereby keeping the distance between the sample surface and the probe constant. The surface shape of the sample was obtained by plotting the voltage value for driving the cantilever beam in accordance with the XY-scanned position.

An electrostatic STM having no electrode 108
At the cantilever drive unit 111,
A bias V _{B is applied} to 2 to displace the cantilever beam to some extent, and the voltage of V _B ± ΔV is applied to displace the cantilever beam. Upon observation, S according to the present invention
In TM observation, relatively large irregularities on the surface of the sample, which had been observed, were hardly observed.

The features of the present invention will be further described with reference to FIGS. 2 and 3. Electrode 10 which is a conventional technique
The operation of the electrostatic drive type cantilever composed of 2 and the cantilever 104 is performed only on the counter electrode side regardless of the polarity of the voltage applied to the electrode and the cantilever as shown in FIG. Displace. It is known that the displacement amount at this time is proportional to the square of the applied voltage. However, with the configuration of the present invention as shown in FIG. 1, as shown in FIG. 3, by applying a voltage to the electrode 102 or the electrode 108 and the cantilever 104, the cantilever 104 is moved to the opposite electrode side. The working range of the beam tip widens due to the displacement to. In FIG. 3, the applied voltage is shown only on the positive side, but the same result can be obtained by applying the negative voltage.

Embodiment 2 An example in which the position controllability of the Z-axis displacement of the cantilever is improved in the electrostatic STM device having the structure of the present invention shown in FIG. 1 will be described.

As in Example 1, the sample surface was scanned in XY while adjusting the voltage applied to the electrodes 102 and 108 by the cantilever drive unit 111 so as to keep the tunnel current constant.

Here, a voltage (V1) is applied to the electrode 102 and the cantilever 104, and at the same time, the electrode 108 and the cantilever 1 are applied.
The displacement of the tip of the beam when a voltage (V2) is applied to 04 will be described.

As can be seen from FIG. 3, the beam is not displaced when V1 = V2. However, since the beam is pulled from both sides by simultaneously applying the voltage of V1 ≠ V2, the beam is less likely to be affected by external force such as vibration, and the position controllability of the beam is improved.

As described above, by simultaneously applying the voltages V1 and V2 (V1 ≠ V2) so as to keep the tunnel current constant, the position controllability of the beam is improved, and the surface is faster and more reliable. Observation becomes possible.

Embodiment 3 In this embodiment, a capacitance type AFM device of the present invention will be described with reference to FIG.

FIG. 4 is a conceptual diagram schematically showing the device and sample prepared in this example. In this device, on the surface of the insulating substrate 201, the capacitance detecting electrode 202 formed of a conductive film, the insulating spacer 203, and the conductive cantilever 2 are provided.
04, the insulating spacer 205, and the capacitance detection electrode 206 made of a high-rigidity conductor in this order, and then the cantilever beam 204.
A probe 207 was formed at the tip of the.

The surface of the sample 208 is observed by the electrostatic capacitance detection unit 209 so that the distance between the substrate 201 and the sample 208 does not change in a state where the sample 208 and the probe 207 are in contact with each other with a constant weak pressure. The substrate 201 is fixed by the illustrated distance (Z direction) control mechanism, and the substrate 201 is made parallel to the sample surface by X
Y-scanned. At this time, since the cantilever 204 moves up and down in the Z direction according to the unevenness of the surface of the sample 208, the change in the capacitance generated between the electrode 202 and the cantilever 204 and between the electrode 206 and the cantilever 204 is electrostatically changed. Capacity detection unit 20
It was detected at 9. The change in the capacitance due to the displacement of the cantilever 204 was plotted in accordance with the XY scanning position to obtain the surface shape of the sample. Where the electrode 2
02 / cantilever 204 and electrode 206 / cantilever 20
Regardless of the unevenness of the sample (plus or minus displacement on the Z axis), the capacitance between 4 can be observed independently, the one with the larger capacitance is selected, and the amount of change is converted to Z displacement at any time. Therefore, it was possible to secure a high resolution as compared with the conventional device which does not have the electrode 206.

Embodiment 4 The electrostatic capacity type STM device of the present invention described in Embodiment 1 is
An example of use as an STM / AFM device will be described. The apparatus may have the configuration shown in FIG. 1 as in the first embodiment. However, 1
A unit 11 has both a cantilever driving function and a capacitance detecting function. Such an apparatus can be used as an STM by the measuring method shown in Example 1 and as an AFM by the measuring method shown in Example 3. Here, by observing the same region of the same sample subjected to the STM measurement or the AFM measurement in the STM mode and the AFM mode, it is possible to investigate without confusing information on both the surface shape and the conductivity distribution. .

Embodiment 5 In this embodiment, a multi STM apparatus of the present invention having a plurality of conductive beam-like structures provided with a probe will be described. FIG. 5 basically shows an example in which three STM configurations (see FIG. 1) shown in the first embodiment are formed in the same substrate. By using a silicon wafer as a substrate and manufacturing it by a semiconductor process technique, a plurality of STM structures can be easily formed without variation. In addition to the linear arrangement, it is easy to arrange in a two-dimensional array such as a matrix. In this embodiment, each cantilever can be driven independently, that is, a plurality of STM observations can be performed at the same time. Even in this configuration,
It is also possible to use it as an STM / AFM composite machine as in the fourth embodiment.

Embodiment 6 The electrostatically driven STM device shown in Embodiment 1 (see FIG. 1)
And a silicon wafer having gold (Au) deposited on its surface as a sample are placed in a vacuum-evacuated chamber, and tungsten hexafluoride (WF) is provided so that the degree of vacuum in the chamber is about 1 × 10 ⁻⁴ Torr. ₆ ) Gas was introduced. When STM observation of the sample surface was performed in this state, it was deposited on the tungsten gold surface corresponding to the probe scanning portion. Even in the processing such as selective deposition or etching on the sample surface by such an STM structure, the device of the present invention has a large Z-axis displacement amount, so that deeper etching and thick deposition are possible and effective.

[0030]

As described below, the present invention has the following effects. (1) The electrostatic drive type STM device can fully utilize the Z-axis degree of freedom originally possessed by the beam-like structure, expands the dynamic range of measurement, and enables more accurate observation of surface irregularities. it can. Further, by simultaneously applying a voltage to the electrodes provided on both sides of the beam-shaped structure in the Z direction,
Since the position controllability of the beam can be improved and the probe can follow the steep surface shape change, faster and more reliable surface observation becomes possible. (2) The capacitance type AFM device can independently detect the capacitance between the beam-like structure and the electrodes provided on both sides of the beam-like structure in the Z direction, and the change on the side where the capacitance is large. By converting the amount into Z displacement and observing the uneven shape of the sample surface,
High resolution can be secured. (3) A compact and high-performance electrostatic STM / AFM multifunction machine is obtained because the apparatus can be downsized and integrated easily.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an electrostatic drive type STM of the present invention.

FIG. 2 is a diagram for explaining displacement characteristics of an electrostatic displacement type cantilever in a conventional device.

FIG. 3 is a diagram for explaining displacement characteristics of the electrostatic displacement type cantilever in the present invention.

FIG. 4 is a conceptual diagram showing an embodiment of a capacitance detection type AFM of the present invention.

FIG. 5 is a conceptual diagram showing an example of an electrostatically driven multi-STM of the present invention.

[Explanation of symbols]

 101 Insulating Substrate 102 First Electrostatic Driving Electrode 103 Insulating Spacer 104 Conductive Cantilever Beam 105 Insulating Film 106 Tunnel Current Wiring 107 Insulating Spacer 108 Second Electrostatic Driving Electrode 109 Probe 110 Sample 111 Cantilever Beam drive unit 112 Tunnel current detection unit 201 Insulating substrate 202 First capacitance detection electrode 203 Insulation spacer 204 Conductive cantilever 205 Insulation spacer 206 Second capacitance detection electrode K 207 Probe 208 Sample 209 Capacitance detection unit

Front page continuation (72) Inventor Yoshihiro Yanagisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasuhiro Shimada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A scanning tunneling microscope in which a probe provided on a conductive beam-shaped structure is moved closer to the sample surface for scanning, and the electrostatic drive electrode has a beam-shaped structure in a direction perpendicular to the scanning surface. A scanning tunneling microscope, characterized in that at least one is provided on each side of a beam-like structure so as to sandwich an object. 2. In an atomic force microscope in which a probe provided on a conductive beam-like structure is brought into contact with a sample surface for scanning, an electrode for detecting an electric capacitance with the beam-like structure is
An atomic force microscope characterized in that at least one or more are provided on both sides of the beam-like structure so as to sandwich the beam-like structure in a direction perpendicular to the scanning plane. 3. The microscope according to claim 1, further comprising a plurality of conductive beam-shaped structures provided with the probe. 4. A compound microscope according to claim 1, wherein at least two types of microscopes are used as a single device. 5. A processing apparatus, wherein the microscope according to any one of claims 1 to 4 is used for processing a sample surface.