Measuring and testing – Surface and cutting edge testing – Roughness
Reexamination Certificate
2000-05-17
2002-10-29
Williams, Hezron (Department: 2856)
Measuring and testing
Surface and cutting edge testing
Roughness
C250S306000, C250S234000, C250S236000
Reexamination Certificate
active
06470738
ABSTRACT:
This application claims the priority of Japanese Patent Application No. 11-143519 filed on May 24, 1999, which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a probe microscope; and, in particular, to a probe microscope capable of attaining highly reliable sample information.
BACKGROUND OF THE INVENTION
For example, for accurately grasping irregularities of a surface of a sample, a scanning tunneling microscope (STM) is used.
According to the principle of measurement in the STM, a probe made of a metal is caused to approach an electrically conductive sample to a distance of about 1 nm, and a minute voltage is applied therebetween, whereby a current flows. This current is known as tunneling current, and is sensitive to changes in the distance therebetween, such that it alters by substantially one digit at most with respect to a change of 0.1 nm.
Therefore, if the metal-made probe is attached to a precision actuator capable of three-dimensional driving, and the measurement sample surface is scanned so as to keep the tunneling current constant, then the distance therebetween will be held constant, and the probe will trace the irregularities of the sample surface on the atomic order.
Here, if the change in the voltage applied to the precision actuator is visualized, then it will correspond to the form of the sample surface.
Insulating samples which could not be observed by the STM can be observed by an atomic force microscope (AFM) derived from the STM.
The AFM detects, instead of the tunneling current used in the STM, the atomic force (attractive force or repulsive force) acting between the measurement sample surface and the probe.
Here, as the probe of the AFM, a metal-made cantilever probe
10
such as the one shown in
FIGS. 1A and 1B
is employed.
FIG. 1A
is a front view thereof, whereas
FIG. 1B
is a top plan view thereof
If the cantilever probe
10
is caused to approach the measurement sample surface
12
while being minutely vibrated up down (in the directions of V
v
) in
FIG. 1A
, then an atomic force will act therebetween, thereby changing the amplitude of vibration of the probe
10
.
Hence, probe light L
1
from a probe irradiating portion
14
irradiates the probe
10
, and the change in intensity of transmitted or reflected probe light L
2
from the probe
10
is detected by a photodetector
16
. From this change in intensity, information about the change in amplitude of vibration of the probe
10
is obtained.
If the distance therebetween is determined from the change in amplitude of vibration, and the stage mounting the measurement sample is driven to scan the measurement sample surface such that the change in amplitude of vibration is kept constant while the probe position is fixed, then the distance therebetween will be held constant, and the probe can accurately trace the irregularities of the measurement sample surface.
If the metal-made cantilever probe
10
is vibrated up and down (in the directions of V
v
) in
FIG. 1A
, on the other hand, then ingredients of the sample at the probe position and the like cannot be analyzed while the irregularities of the measurement sample surface
12
can be grasped accurately.
Therefore, in recent years, near-field optical microscopes, having a spatial resolution smaller than the wavelength of light, capable of spectral analysis and measurement, have been developed with expectation for their applications.
The near-field optical microscopes include two systems, i.e., collection mode in which an optical near-field occurring in the measurement sample surface is scattered at a needle-like probe tip portion and collected so as to be detected, and illumination mode in which the measurement sample surface is illuminated with the near-field light occurring from the needle-like probe tip portion and the light scattered or released by the measurement sample surface is collected and detected by the probe or a light-collecting optical system.
In any case, the optical near field is generated in an area on the order of several tens of nanometers from the measurement sample surface, whereby the distance between the measurement sample surface and the fiber probe must be controlled within a very minute distance not longer than the wavelength of light.
For controlling the distance between the measurement sample surface and the probe, shear force feedback method is employed in general.
In the shear force feedback method, as shown in
FIGS. 2A and 2B
, a needle-like probe
18
is caused to approach the measurement sample surface
12
while being uniaxially vibrated (in the directions of V
H
) on the measurement sample surface
12
.
FIG. 2A
is a front view thereof, whereas
FIG. 2B
is a top plan view thereof When the distance between the measurement sample surface
12
and the probe
18
falls within the reach of the optical near field, then a shear force acts therebetween, thereby changing the amplitude of vibration of the probe
18
.
Hence, probe light L
1
from the probe irradiating portion
14
irradiates the fiber probe
18
, and the change in intensity of transmitted or reflected probe light L
2
from the probe
10
is detected by the photodetector
16
. From this change in intensity, information about the change in amplitude of vibration of the probe
18
is obtained.
If the distance therebetween is determined from the change in amplitude of vibration, and the stage mounting the measurement sample is driven to scan the measurement sample surface such that the change in amplitude of vibration of the needle-like probe
18
is kept constant while the probe position is fixed, then the distance therebetween will be held constant, and the needle-like probe
18
can accurately trace the irregularities of the measurement sample surface on the atomic order.
Thus, when the needle-like probe
18
is used for carrying out the illumination mode or collection mode, not only the irregularities of the measurement sample surface
12
can be grasped, but also ingredients of the sample at the probe position and the like can be analyzed.
However, such a needle-like probe
18
is also uniaxially vibrated on the measurement sample surface, and the lateral shift component of the atomic force acting between the measurement sample surface and the probe is detected, whereby its sensitivity would lower by one digit or more when compared with the case where the vertical component of the atomic force is measured with the cantilever probe
10
.
If a shear force uniaxially vibrating the probe on the measurement sample surface is employed, then there may be a fear of a difference occurring in the obtained image of irregularities of measurement sample surface, depending on the scanning direction of the measurement sample surface, even in the same measurement sample surface.
Hence, the reliability of measurement results with the needle-like probe
18
has still a room for improvement, but no techniques for achieving it have been known yet.
SUMMARY OF THE INVENTION
In view of the above-mentioned background art, it is an object of the present invention to provide a probe microscope capable of attaining sample information with a higher reliability.
For achieving the above-mentioned object, the probe microscope in accordance with the present invention is a probe microscope for causing a measurement sample surface and a tip portion of a probe on the sample side to approach each other, detecting an interaction between the measurement sample surface and the tip portion of the probe on the sample side, and obtaining surface information of the measurement sample from the interaction; the probe microscope comprising vibrating means and detecting means.
Here, the probe is a flexible needle-like probe.
The vibrating means is capable of rotating the probe while flexing the tip portion thereof on the sample side so as to draw a circle having a size corresponding to an increase and decrease in the interaction between the measurement sample surface and the tip portion of the probe on the sample side.
The detecting means detects the in
Akutsu Koji
Hisada Hideho
Miyajima Tatsuya
Narita Yoshihito
Ohtsu Motoichi
Cygan Michael
Jasco Corporation
Snider Ronald R.
Snider & Associates
Williams Hezron
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