JP2007047107A - Scanning probe microscope with probe cleaning mechanism and probe cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a contamination of a probe while preventing a sample surface from deteriorating, without removing any cantilever. <P>SOLUTION: A scanning probe microscope is provided, which comprises: a sample measuring chamber; a probe cleaning chamber; and a blocking mechanism for blocking off between the above two chambers, and in which the cantilever can be moved between the two chambers. The probe cleaning chamber is equipped with an ultraviolet light irradiation mechanism and an ozone supplying mechanism, and the sample measuring chamber and the probe cleaning chamber are blocked off from each other when operating above two mechanisms. The cantilever cleans the probe by using ultraviolet light and ozone in the probe cleaning chamber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning probe microscope represented by an AFM (Atomic Force Microscope), and more particularly to a probe cleaning mechanism and a probe cleaning method at the tip of a cantilever.

In a scanning probe microscope typified by AFM, a probe is attached to the tip of a cantilever beam in order to detect the fine structure and structure of the sample surface using the interaction between the sample surface and the probe. A cantilever is used as a scanning probe.
When the probe is scanned on the sample surface, an attractive force or a repulsive force based on an atomic force is generated between the sample surface and the probe, and the cantilever is distorted. At this time, when the cantilever is irradiated with laser light and the position of the reflected light from the cantilever is detected by the optical sensor, the position of the reflected light changes according to the amount of strain. If the sample stage is finely moved in the Z-axis direction so that the strain amount is constant, that is, the gap between the sample surface and the probe is constant, the fine movement signal or the detected strain amount at that time is the sample surface. The high-resolution image at the atomic image level can be obtained at the maximum. Furthermore, if the force acting between the sample and the probe is used, a distribution of nanoscale magnetic force, surface potential, viscoelastic force, and frictional force can be obtained.

For this reason, surface shape evaluation using a scanning microscope probe is currently widely used as a means for evaluating characteristics of microdevices.
JP-A-9-145726 JP 2000-81382 A

In a scanning probe microscope, a sample surface is scanned with a probe at the tip of a cantilever to obtain a shape. For this reason, when there is a contaminant on the sample surface, the probe is contaminated by the transfer of the contaminant, so that the measurement cannot be performed correctly. In addition, even when contaminants are attached to the probe before the sample measurement, the measurement cannot be performed correctly. In this case, most of the contaminants adhering to the probe are caused by organic matter.
Conventionally, when contamination is attached to the probe, the probe is discarded and a new probe is attached, or the cantilever is once removed from the holder, and the contaminant is removed by a cleaning device such as an ultrasonic cleaning device or a hydrophilic treatment device. After removing, the cantilever was attached to the holder again.
However, it is clear that if the cantilever is replaced each time the probe is contaminated, the measurement time and process increase. In addition, when removing contamination of the probe using a cleaning device, wet cleaning methods such as ultrasonic cleaning transfer the adhering moisture, acid or organic cleaning components to the sample side during remeasurement, and alter the sample surface. There is a possibility to bring.

Furthermore, since the cantilever must be once removed from the holder with tweezers and mounted again, it takes time to detach the cantilever and increases the measurement runtime. In addition, since the cantilever is attached by hand, the reproducibility of the measurement position before and after cleaning cannot be guaranteed.
In response to these problems, a method of providing a probe cleaning mechanism in a scanning probe microscope has been proposed, and ultrasonic cleaning of the probe, acid cleaning of the probe, high-pressure gas spraying on the probe, and high probe current A method of removing contaminants by shaking and Ar plasma irradiation of the probe under reduced pressure has been proposed (see, for example, Patent Document 1). However, as pointed out above, when a wet cleaning method such as ultrasonic cleaning is employed, the adhering moisture, acid, and organic cleaning components may migrate to the sample side during re-measurement and cause alteration of the sample surface. is there. Further, according to the present invention, since the sample and the cantilever are subjected to high-pressure gas treatment or plasma treatment in the same atmosphere, the sample may be exposed to the high-pressure gas or plasma, and the sample surface may be altered. Furthermore, it is difficult to remove highly sticky organic contaminants with high current shaking.

Patent Document 2 proposes a cleaning method characterized by forming a photocatalytic film on a scanning microscope probe and irradiating it with ultraviolet rays for cleaning. This is because when the surface of the photocatalyst (titanium dioxide) is irradiated with ultraviolet rays, the holes formed on the surface of the titanium dioxide take electrons from hydroxide ions in the air, resulting in organic substances. It is a technique to decompose. However, the proposed method requires the photocatalyst film to be formed on the probe in advance, which increases the cost for forming the photocatalyst film when compared with a general scanning microscope probe. This will increase the cost.
The present invention has been made in view of the above-mentioned problems. A cleaning device using ultraviolet light and ozone is introduced into a scanning probe microscope, and contamination of the probe is removed without removing the cantilever. By providing a shielding mechanism to the surface, it is possible to reduce the measurement runtime and measurement cost by preventing the surface deterioration of the sample during cleaning, and to contribute to the improvement of measurement efficiency and measurement position reproducibility. The means will be described below.

The scanning probe microscope of the present invention includes a sample measurement chamber, a probe cleaning chamber, and a blocking mechanism between the two chambers, the cantilever can be moved between the chambers, and the probe cleaning chamber is irradiated with ultraviolet light. A mechanism and an ozone supply mechanism. The sample measurement chamber and the probe cleaning chamber are blocked by the blocking mechanism while the ultraviolet light irradiation mechanism and the ozone supply mechanism are in operation.
The probe cleaning method for a scanning probe microscope according to the present invention includes a sample measurement chamber, a probe cleaning chamber, and a blocking mechanism between the chambers, the cantilever being movable between the chambers, and the probe cleaning. An ultraviolet light irradiation mechanism and an ozone supply mechanism are disposed in the chamber, the cantilever is moved to the probe cleaning chamber, and probe cleaning is performed using ultraviolet light and ozone. The ultraviolet light irradiation mechanism and the ozone supply mechanism are During operation, the sample measuring chamber and the probe cleaning chamber are blocked by the blocking mechanism.

  According to the scanning probe microscope described in the claims relating to the present invention, the residue attached to the probe can be effectively decomposed and removed by using ultraviolet light and ozone in combination. Further, by shielding the sample from the atmosphere in which the probe is being cleaned, contaminants on the probe can be removed without damaging the sample. In addition, it is not necessary to remove the probe and carry it outside the device, and the contamination residue of the probe can be removed easily and in a short time, so the probe can be easily reused and the measurement runtime can be shortened. Yes, the measurement cost can be reduced. In addition, the reproducibility of the measurement position of the probe can be improved and the measurement runtime can be shortened without depending on the skill level of the operator.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 are schematic cross-sectional views for explaining an example of an embodiment of the present invention. FIG. 1 shows a state during sample measurement, and FIG. 2 shows a state during probe cleaning.
In the scanning probe microscope of the present invention, the sample measurement chamber 8 and the probe cleaning chamber 9 can be blocked by the shielding plate 7, and the whole is shielded from the outside by the soundproof shielding cover 6.
At the time of measurement, the cantilever holder 2 is arranged at a position facing the sample stage. Washing is performed when the contamination of the probe is confirmed due to image disturbance during measurement. At the time of cleaning, the cantilever holder 2 is moved along the guide rail 5 from the sample measuring chamber 8 to the probe cleaning chamber 9, and a shielding plate 7 is inserted between the two chambers so that ultraviolet light and ozone are introduced into the sample measuring chamber 8. Wash with the entry blocked. After cleaning, the cantilever holder 2 is moved to the sample measurement chamber 8 along the guide rail 5 again.

The sample measurement chamber 8 includes a sample scanning mechanism 1 and a laser light irradiation unit 4. A sample stage 11 is disposed in the sample scanning mechanism 1, and a sample 12 is placed on the sample stage 11. A cantilever 21 having a probe 22 at the tip is attached to the cantilever holder 2. The cantilever holder 2 is held at a position facing the sample table 11 and the sample 12 by the guide rail 5. A laser irradiation unit 4 having a laser irradiation mechanism for the cantilever 21 and a function of receiving a laser reflected light from the cantilever 21 is disposed at a position opposite to the sample stage 11 and the sample 12.
At the time of measurement, the probe 22 scans the surface of the sample 12 and simultaneously irradiates the cantilever 21 with a laser from the laser irradiation unit 4 to detect the deflection or twist of the cantilever 21 using the laser reflected light.

If it is determined that the probe is contaminated due to abnormal image data during measurement, etc., cleaning is performed.
First, the probe 22 is separated from the sample 12 in the upper direction, the cantilever holder 2 is slid along the guide rail 5 into the probe cleaning chamber 9, and the shielding plate 7 is inserted to clean the sample measurement chamber and the probe. The chamber 9 is shut off. The shielding plate 7 is not particularly limited in its installation method and control mechanism as long as the sample 12 is not exposed to ultraviolet rays and ozone atmosphere.
Thereafter, the ultraviolet lamp 31 is turned on, and the ozone supply mechanism 33 is operated to start cleaning. A general ozonizer mechanism is used as an ozone supply method. That is, dry air or oxygen as a raw material is passed through a discharge tube mounted inside the ozone supply mechanism 33, and ozone is generated by applying a high voltage and supplied as ozone gas. The ozone concentration is about several tens to several hundred ppm, and may be variable depending on the degree of contamination of the probe.
If ozone generation is sufficiently performed by ultraviolet light, the ozone supply mechanism 33 can be omitted. The generated ozone is quickly discharged through the exhaust port 32.

At this time, contaminants on the probe surface are removed by ultraviolet light irradiation and supplied ozone. Since ozone is quickly exhausted from the exhaust port 32, the influence of the ozone retention on the device and the sample 12 is extremely small. Further, since the cleaning is performed with the soundproof shielding cover 6 installed, the ultraviolet light does not leak outside.
Most of the commercially available probes are made of Si compounds or Si compounds coated with metal. Therefore, the possibility of destroying the probe surface is extremely small even after cleaning with ultraviolet light or ozone, and the probe can be used repeatedly as long as the tip of the probe is not physically worn by unevenness of the sample. .
The cleaning method of the present invention is a method of decomposing and cleaning organic substances adhering to the probe surface with ultraviolet rays and ozone, and the ultraviolet rays and ozone directly act on the organic substances and decompose. For this reason, it is not necessary to form a photocatalyst film, and organic substances can be removed without depending on the probe material. Therefore, the present invention can be applied to a commercially available scanning microscope probe made of silicon nitride or the like, and the measurement cost can be reduced by using a commercially available product.

  After the cleaning of the probe 22 is completed, the shielding plate 7 is removed, the cantilever holder 2 is returned to the sample measurement chamber 8 along the guide rail 5 and measurement is resumed.

Hereinafter, it demonstrates in detail using an Example.
A commercially available SiN probe (model number SI-DF20 manufactured by Seiko Instruments Nanotechnology Co., Ltd.) was exposed to the laboratory atmosphere for a long period (about 3 months), and the probe was intentionally contaminated. Using this probe, the surface of the sample was measured, and the time from when image disturbance occurred during measurement until the probe was cleaned and measurement was started again was measured as the “probe cleaning time”.
First, measurement was performed with a conventional scanning probe microscope, and after confirming that the image was disturbed during measurement, probe contamination was removed by a conventional method. After removing the cantilever from the cantilever holder, the cantilever was installed in a hydrophilic treatment apparatus (HDW-400 manufactured by JEOL Ltd.) and evacuated, and after reaching a predetermined degree of vacuum, the hydrophilic treatment was performed for 60 seconds. Thereafter, the cantilever was again attached to the cantilever holder and installed on the sample scanning mechanism. Thereafter, the measurement was performed again to confirm that there was no image disturbance.

In the case of the conventional method, the probe cleaning time is about 5 minutes. Further, it has been found that when the operator is not familiar with the probe removal operation, the probe cleaning time is increased by about 1 minute.
Next, it measured with the scanning probe microscope by this invention. After confirming that the image was disturbed during the measurement, the cantilever holder 2 was slid into the probe cleaning chamber 9 and the shielding plate 7 was installed. Thereafter, the probe 22 was irradiated with ultraviolet light and ozone for about 60 seconds. The energy of the ultraviolet light at this time was about 2.1 mW / cm ² and the ozone concentration was 90 ppm. Thereafter, the shielding plate 7 was removed, and the cantilever holder 2 was returned to the sample measurement chamber 8 again. Subsequently, measurement was performed again to confirm that there was no image distortion.
In the case of the method according to the present invention, the probe cleaning time was about 1 minute 20 seconds. Even when the operator is not familiar with the probe removal operation, the probe cleaning time is the same as described above.

  Therefore, according to the scanning probe microscope of the present invention, it has been found that the probe cleaning time can be shortened to nearly 1/4 of the conventional one.

FIG. 2 is a schematic cross-sectional view for explaining a configuration example of a scanning probe microscope according to the present invention, and shows a state during sample measurement. FIG. 2 is a schematic cross-sectional view for explaining a configuration example of a scanning probe microscope according to the present invention, and shows a state during probe cleaning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample scanning mechanism 11 Sample stand 12 Sample 2 Cantilever holder 21 Cantilever 22 Probe 31 Ultraviolet lamp 32 Ozone exhaust port 33 Ozone supply mechanism 4 Laser beam irradiation unit 5 Guide rail 6 Soundproof shielding cover 7 Shielding plate 8 Sample measurement chamber 9 Probe Needle washing room

Claims (2)

A sample measurement chamber, a probe cleaning chamber, and a shut-off mechanism between the two chambers, and the cantilever being movable between the two chambers,
The probe cleaning chamber includes an ultraviolet light irradiation mechanism and an ozone supply mechanism, and the sample measurement chamber and the probe cleaning chamber are blocked by the blocking mechanism while the ultraviolet light irradiation mechanism and the ozone supply mechanism are in operation. A scanning probe microscope. A probe cleaning method for a scanning probe microscope,
A sample measurement chamber, a probe cleaning chamber, and a shut-off mechanism between the two chambers, and the cantilever being movable between the two chambers,
An ultraviolet light irradiation mechanism and an ozone supply mechanism are arranged in the probe cleaning chamber, the cantilever is moved to the probe cleaning chamber, and probe cleaning is performed using ultraviolet light and ozone.
A probe cleaning method for a scanning probe microscope, wherein the sample measurement chamber and the probe cleaning chamber are blocked by the blocking mechanism while the ultraviolet light irradiation mechanism and the ozone supply mechanism are in operation.

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