JP2003279463A - Scanning probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning probe microscope capable of detecting accurately the displacement quantity of a probe, and thereby observing the accurate surface structure of a measuring sample. <P>SOLUTION: In an atomic force microscope wherein an optical lever system is adopted, a light emitting element 8 is provided on the back side of a cantilever 5, and a light receiving device 9 is directly irradiated with light from the light emitting element 8, to thereby suppress decline of light receiving sensitivity of the light receiving device 9 caused by reflection of unintended light. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope, and more particularly to a scanning probe microscope that employs an optical lever method.

[0002]

2. Description of the Related Art A scanning probe microscope (SPM) is a device capable of knowing the surface structure and physical properties of a substance to be measured in a micron-order region with a nano-order spatial resolution. The SPM is a general term including various microscopes and their related technologies, and is classified into many types according to its principle and information to be detected, but they all have a common point of using a probe.

That is, in SPM, a probe whose tip is sharpened to the nano order by fine processing is scanned near the surface of the substance to be measured, and various information about the surface is obtained through this probe. Specifically, various signals due to the interaction between the substance to be measured and the probe, the force received by the probe due to the interaction with the substance to be measured, the displacement of the probe due to receiving the force, etc. There are devices that indirectly obtain information about the surface.

For example, the atomic force generated between the surface of the substance to be measured and the probe when the probe is placed near the surface is utilized to measure the increase or decrease in the atomic force when the probe is scanned. An atomic force microscope (AFM), which obtains a surface structure by converting it into distance information between a substance and a probe, is a device often used in SPM.

As a method for detecting the atomic force generated between the surface of the substance to be measured and the probe in the AFM, the displacement of the probe due to the atomic force being applied to the probe is used. A
Not only FM but also other SPMs, when utilizing the force received by the probe due to the interaction with the substance to be measured, it is necessary to detect the displacement of the probe due to the force received by the probe. . Although there are several methods for detecting the displacement of the probe, the optical lever method, which has a simple device configuration, is most often used in the current SPM.

In the conventional optical lever method, a light emitting element such as a laser diode (semiconductor laser) is used to irradiate the back surface of a cantilever holding a probe with laser light, and a photodetector having a plurality of detection portions is divided. An angle change of the reflected light from the back surface of the cantilever is detected using a light receiving device such as a diode. In an actual device, based on the displacement of the probe thus obtained, the distance between the substance to be measured and the probe should be constant (that is, the atomic force should be constant). Position control is performed, and the surface structure is obtained from the moving distance at this time.

However, in such a conventional optical lever method, when the irradiation of the laser beam on the back surface of the cantilever is not appropriate, the laser light leaks from the cantilever, or even when the irradiation of the laser light on the back surface of the cantilever is appropriate, the probe is not used. The laser light may pass through. The light leaking from or passing through the cantilever reaches the surface of the substance to be measured, and if the surface has a high reflectance, it is reflected and returns to the light receiving device. At this time,
The light reflected on the back surface of the probe may interfere with the light reflected on the surface of the substance to be measured. When such light is detected by the light receiving device, since light intensity is periodically generated due to optical interference, light having different intensity depending on the detection position is detected. When detecting the reflected light from the back surface of the cantilever, the information of the probe displacement may be buried under the influence of optical interference, and as a result, the problem that the surface structure cannot be accurately observed occurs.

[0008]

As described above, in the conventional scanning probe microscope adopting the optical lever method, the light receiving device cannot detect the reflected light accurately, and therefore the displacement of the probe can be accurately measured. It could not be detected.
As a result, the accurate surface structure of the sample to be measured cannot be observed.

The present invention accurately detects the displacement of the probe,
Furthermore, it aims at providing the scanning probe microscope which can observe the exact surface structure of a to-be-measured sample.

[0010]

A scanning probe microscope of the present invention has a fixed end and a free end, and holds a probe arranged in the vicinity of the free end with a gap in a sample to be measured,
It has a cantilever whose free end side is displaced according to the surface state of the sample to be measured, a light emitting element fixed on the cantilever, and a light receiving device for directly receiving light from the light emitting element. .

The scanning probe microscope of the present invention has a fixed end and a free end, holds a probe arranged in the vicinity of the free end with a gap in the sample to be measured, and maintains the surface state of the sample to be measured. The free end side of which is displaced according to, a light emitting element fixed on the cantilever, a reflecting plate for reflecting light emitted from the light emitting element in a predetermined direction, and reflected light from the reflecting plate. And a light receiving device for receiving light.

The scanning probe microscope of the present invention has a surface on which a sample to be measured is placed, a sample stage for moving the sample to be measured in the direction of the measuring surface, and a sample stand arranged close to the sample to be measured with a predetermined gap. , A probe that receives a force according to the surface state of the sample to be measured, and a fixed end and a free end, and holds the probe on the surface of the sample to be measured side near the free end, A cantilever whose free end side is displaced according to the amount of change, a light emitting element fixed on the cantilever, a light receiving device for directly receiving light from the light emitting element, and the free end side being displaced so that the light receiving A detection device that detects a change in the light receiving state of the device, and the sample that adjusts the distance between the sample to be measured and the probe so that the light receiving state of the light receiving device is the light receiving state before the displacement of the free end. With the controller of the platform Wherein in correspondence with measurement position of the measured sample, and having a storage unit for storing an adjusted travel distance of the sample stage by the control unit.

A scanning probe microscope according to the present invention has a surface on which a sample to be measured is placed, a sample stage for moving the sample to be measured in the direction of the measuring surface, and a sample stand arranged close to the sample to be measured with a predetermined gap. , A probe that receives a force according to the surface state of the sample to be measured, and a fixed end and a free end, and holds the probe on the surface of the sample to be measured side near the free end, A cantilever whose free end side is displaced according to the amount of change, a light emitting element fixed on the cantilever, a reflector for reflecting the light emitted from the light emitting element in a predetermined direction, and a reflection from the reflector. A light receiving device for receiving light and a detecting device for detecting a change in the light receiving state of the light receiving device by displacing the free end side, and a light receiving state of the light receiving device becomes a light receiving state before the displacement of the free end. As above A control unit of the sample stage that adjusts the distance between the measurement sample and the probe, and a storage unit that stores the moving distance of the sample stage adjusted by the control unit in association with the measurement position of the sample to be measured. And having.

It is preferable that the light emitting element is fixed on the back surface side of the surface on which the probe of the cantilever fixes the light emitting element.

It is preferable to have a condenser for condensing the light from the light emitting element toward the detector.

That is, in the conventional scanning probe microscope adopting the conventional optical lever method, the light emitted from the light emitting element is applied to the cantilever and the reflected light from the cantilever is detected by the light receiving device. Is
Since the reflected light from the cantilever interferes with the reflected light reflected at a place other than the cantilever, the position of the cantilever (reflected position) cannot be accurately detected.

On the other hand, according to the present invention, since the cantilever is provided with the light emitting element, the light receiving device directly receives the irradiation light from the light emitting element, or receives the light reflected by the reflecting plate of an arbitrary size, so that it is not intended. The interference with the generated reflected light disappears, and the position of the cantilever (the position of the light emitting element) can be accurately detected.

[0018]

FIG. 1 is a conceptual diagram of an atomic force microscope, and the first embodiment of the present invention will be described below with reference to this drawing.

The sample table 1 has a horizontal upper surface, and on the horizontal upper surface, a thin plate-shaped sample to be measured 2 such as a semiconductor wafer or a hard disk recording medium is to be observed on the upper surface. It is placed so that. Further, the sample table 1 can be moved in a horizontal plane (XY plane) or in a vertical direction (Z-axis direction) by the drive device 3 that is driven according to a drive signal from the CPU 3, and thus the measured object can be measured. The sample can be moved to the desired position.

A probe for observing the upper surface of the sample 2 to be measured is arranged above the probe. The probe includes a cantilever 5, a probe 6, and a cantilever support member 12.

The cantilever 5 is an elastic plate having a predetermined spring coefficient, and one end thereof is fixed by a cantilever support member 12. The other end of the cantilever 5 is a free end, and a probe 6 is provided near the free end.

The probe 6 is arranged so that its tip faces the sample to be measured 2 and a predetermined gap is formed between the tip of the probe 6 and the sample to be measured 2. Hereinafter, the state of the cantilever at this time will be referred to as the “initial state of the cantilever”.

As the cantilever, for example, silicon (length from free end to fixed end) 100 μm to 500 μm, width (width of surface on which the probe is formed) 20 μm to 100 μm, thickness 1 μm to 10 μm, etc. Can be used.
The tip usually has a tip polarity of about 1 nm to 10 nm and a length of 1
Needles or cones having a shape of about 0 μm to 20 μm are used. For example, silicon or a silicon surface coated with diamond for abrasion resistance can be used.

Further, the cantilever 5, the probe 6 and the cantilever support member 12 may be joined to each other or integrally molded.

When the sample table 1 is moved in the XY plane and the upper surface of the sample 2 to be measured is scanned by the probe 6, the probe 6 receives a force corresponding to the surface state of the sample 2 to be measured.

For example, in the atomic force microscope, the measured sample 2
If the surface has irregularities, the distance between the probe 6 and the sample 2 to be measured changes, the atomic force between the two changes, and the probe 6 receives the force. Then, according to the force received by the probe 6, the free end of the cantilever 5 is vertically displaced in the Z-axis direction. As a result, the tilt angle of the cantilever 5 changes from the initial state of the cantilever near the free end. Specifically, when the height of the sample surface to be measured becomes large, the interatomic force between the probe and the sample to be measured becomes large, and the tilt angle of the cantilever 5 becomes large. And the interatomic force between the sample to be measured and the cantilever 5 becomes smaller.

Here, the sample surface irregularities suitable for measurement with an atomic force microscope are about 1 nm to 10 μm.

The term "near the free end" refers to a range in which a change in the tilt angle of the cantilever 5 can be recognized by a light receiving device described later. The closer the free end is, the smaller the change amount of the tilt angle due to the force. Since it becomes large, it is preferable to set it as a region closer to the free end side.

On the other hand, a light emitting element 8 such as a laser diode is fixed to the upper surface near the free end of the cantilever 5, and the light emitted from the light emitting element 8 is received by a light receiving device 9 fixed to the housing 7. Received directly.

At this time, when the light emitted from the light emitting element 8 is applied to a plurality of light receiving elements, as shown in the figure, a condensing means such as an optical lens is provided in the optical path from the light emitting element 8 to the light receiving device 9. A more accurate tilt angle of the cantilever 5 can be obtained by disposing 10 and irradiating light in a desired range. Here, “directly receive light” means to receive light without reflection, and simply receiving light that has passed through the optical lens is included in the expression “directly receive light”.

If the light emitting element 8 is fixed so that the angle formed by the length direction of the cantilever 5 and the light emitting direction of the light emitting element 8 is fixed, even if built in the cantilever 5. Alternatively, it may be separately arranged on the surface of the cantilever 5.

The light receiving device 9 is formed by arranging a plurality of light receiving elements such as photodiodes, and the light emitted from the light emitting element 8 is detected by each light receiving element according to the tilt angle of the cantilever 5. Are arranged to change. In addition, the detection results of multiple light receiving elements are
Sent to U3.

The CPU 3 determines from the light receiving state of the light receiving device whether the cantilever 5 is closer to or far from the sample to be measured with respect to the initial state of the cantilever.
Then, the sample stage 1 is moved in the Z-axis direction so that it approaches the initial state of the cantilever, that is, the distance between the probe 6 and the cantilever 5 becomes the above-mentioned initial distance.

Further, the CPU observes the light receiving state of the light receiving device 8 even during the movement, and when the light receiving state becomes the same as the light receiving state in the initial state of the cantilever, the movement in the Z-axis direction is stopped. That is, the distance between the probe 6 and the surface of the measured sample 2 becomes the above-mentioned “predetermined gap”.

This amount of movement in the Z-axis direction is the height variation of the surface of the sample 2 to be measured, and in the CPU 3, the amount of variation in the Z-axis direction when moving to the position (x, y) on the surface of the sample to be measured. z
It is possible to represent the unevenness state of the surface of the sample to be measured 2 by storing in correspondence with.

As described above, in the first embodiment, the reflected light from the cantilever is not received, and the light emitted from the light emitting element is directly received by the light receiving device. It is possible to measure the unevenness of the surface of the sample to be measured without adversely affecting the light reception due to the reflected light at.

Next, a second embodiment will be described with reference to FIG.

FIG. 2 is a conceptual diagram of an atomic force microscope,
The same components as those described in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the light emitted from the light emitting element 8 is not directly received by the light receiving device 9, but the reflected light once reflected by the reflecting plate 11 such as a mirror is received by the light receiving device 9. 1 embodiment. By providing the reflection plate in this way, it is possible to set the location of the light receiving device 9 to an arbitrary position.

In the conventional optical lever type scanning probe microscope, the light is reflected by the cantilever 5 whose weight and shape are limited. However, since the reflector 11 has no such limitation, the light emitting element 8 emits the light. Since the size and thickness can be set so that the reflected light can be reliably reflected, reflected light generated at an unintended place can be prevented from entering the light receiving device 9.

A modified example of the light collecting device in the first and second embodiments will be described with reference to FIG.

FIG. 3 is a schematic perspective view of the free end side of the cantilever. As described above, the probe 6 is arranged on one surface of the cantilever 5 and the light emitting element 8 is arranged on the back surface thereof. Further, on the back surface of the cantilever 5, a hemispherical shell 10 ′ is fixed so as to cover the light emitting element 8, and a lens 10 is formed on the ceiling of the shell 10 ′.

If the lens 10 is fixed to a housing or the like, the relative position between the light emitting element 8 and the lens 10 changes when the cantilever 5 is displaced, so that the focal point of the light emitted from the light emitting element 8 deviates from the optical axis. By fixing the lens 10 to the cantilever 5 in this way, the focus point of the light always coincides with the optical axis, so that the light receiving state by the light receiving device 9 can be accurately detected. become.

As described above, in each embodiment,
Since the light emitted from the light emitting element is received directly by the light receiving device without receiving the reflected light from the cantilever, there is no adverse effect on the light reception due to the reflected light in an unintended place, and the unevenness of the measured sample surface It becomes possible to measure the condition.

The present invention is not limited to the atomic force microscope, but can be applied to a magnetic force microscope, an electric force microscope, a horizontal force microscope, etc. as long as it is a scanning probe microscope adopting an optical lever method. it can.

[0046]

As described above, the scanning probe microscope of the present invention can accurately detect the displacement amount of the probe and, by extension, observe the accurate surface structure of the sample to be measured.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an atomic force microscope according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an atomic force microscope according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a modified example of the light collecting device.

[Explanation of symbols]

1… Sample stand 2 ... Measured sample 3 ... CPU 4 ... Drive device 5 ... cantilever 6 ... Tip 7 ... Case 8 ... Light emitting element 9 ... Light receiving device 10 ... Lens 11 ... Mirror

Claims (6)

[Claims] 1. A probe having a fixed end and a free end, which is arranged near the free end and is arranged in the sample to be measured with a gap, and the free end side is arranged in accordance with the surface state of the sample to be measured. A scanning probe microscope comprising: a cantilever that is displaced, a light-emitting element fixed on the cantilever, and a light-receiving device that directly receives light from the light-emitting element. 2. A probe having a fixed end and a free end, the probe being arranged in the vicinity of the free end and having a gap in the sample to be measured is held, and the free end side is arranged in accordance with the surface state of the sample to be measured. It has a cantilever that is displaced, a light emitting element fixed on the cantilever, a reflector that reflects the light emitted from the light emitting element in a predetermined direction, and a light receiving device that receives the reflected light from the reflector. A scanning probe microscope characterized by the above. 3. The scanning probe microscope according to claim 1, wherein the light emitting element is fixed to a back surface side of a surface of the cantilever on which the probe is fixed. 4. A light condensing device for condensing light from the light emitting element toward the detector.
Alternatively, the scanning probe microscope according to claim 2. 5. A surface of the sample to be measured, the sample table having a surface on which the sample to be measured is placed, and a sample table for moving the sample to be measured in a measurement surface direction, the sample table being arranged in proximity to the sample to be measured with a predetermined gap. It has a probe that receives a force according to the state, a fixed end and a free end, and holds the probe on the surface of the sample to be measured side near the free end. A cantilever whose end side is displaced, a light emitting element fixed on the cantilever, a light receiving device for directly receiving light from the light emitting element, and a change in the light receiving state of the light receiving device by displacing the free end side. A detection device for detecting, a light receiving state of the light receiving device is a light receiving state before the displacement of the free end, a control unit of the sample table that adjusts a distance between the sample to be measured and the probe, At the measurement position of the sample to be measured A scanning probe microscope according to claim 1, further comprising: a storage unit that stores a movement distance of the sample stage adjusted by the control unit. 6. A surface of the sample to be measured, the sample table having a surface on which the sample to be measured is arranged, and a sample table for moving the sample to be measured in a measurement surface direction, the sample table being arranged in proximity to the sample to be measured with a predetermined gap. It has a probe that receives a force according to the state, a fixed end and a free end, and holds the probe on the surface of the sample to be measured side near the free end. A cantilever whose end side is displaced, a light emitting element fixed on the cantilever, a reflecting plate for reflecting light emitted from the light emitting element in a predetermined direction, and a light receiving device for receiving reflected light from the reflecting plate. A measuring device that detects a change in the light receiving state of the light receiving device by displacing the free end side, and the light receiving state of the light receiving device becomes the light receiving state before the displacement of the free end, And the distance between the probe and And a storage unit for storing the moving distance of the sample stage adjusted by the control unit in association with the measurement position of the sample to be measured. Type probe microscope.