Currently, micro-components are required to fabricate with great precision owing to the miniaturization of complex
product. In order to assess the dimension, size, and other geometric quantities of such complex micro-components,
technological progress is needed in micro- and nano-coordinate metrology. Therefore, the coordinate metrology have
been attempted thus far. To establish nano-coordinate metrology with a microprobe technique, we have been developing
the optically trapped probe, whose principle is based on the single-beam gradient-force optical trap of a particle in air.
However, the rapidly increasing complexity including micro-fine figures makes it difficult to evaluate geometric
quantities using a microprobe that can barely access a concave surface. An improved microprobe is required to have a
better long working distance, wide measurement range, and high resolution. In this paper, a novel probing technique for
coordinate metrology is discussed. The proposed method is based on optical interference, which is seen as a standing
wave pattern, also called a standing wave scale. The feasibility is examined by the profile measurement of a smooth
surface with high accuracy and the dimensional measurement of a trench structure.
Various products have been miniaturized in recent years. And, the measurement technology for surface profile of micro
components is highly demanded. Then, we proposed a new measurement technique for surface profile using the standing
wave trapping. The high-accuracy scale and the high-sensitive sensor are required in the profile measurement. In our
measurement system, the optical trapping particle is used as the sensor. The standing wave pattern is used as the
measurement scale, which has wavelength-determined intensity pitch of interference field (λ/2). Therefore, this
measurement technique is expected to perform the high-accuracy measurement. It was experimentally found that the
vertical measurement range is about 250 μm. The uncertainty of the sensor is ±λ/100. Thus, this technique is capable of
measuring large objects in height. When measuring the continuous surface, the sensor particle is scanned in the
horizontal direction above the measured surface. The trapped sensor particle in the standing wave field axially moves to
follow the measured surface topography. The particle jumps when the surface profile exceeds the pitch of the standing
wave pattern. Therefore, the surface profile can be calculated based on the measurement of the particle motional
variation. As pre-measurement, the dependency of the scale pitch on measured surface angles was investigated. A microlens
was measured with the angle dependency correction. This shows the improvement of the measurement accuracy.
Laser trapping is a widely used technique such as manipulating cells. Recently the trapping technique is used in air, for
example, a precision probe for sensing the surface of an object. To expand the applications of the trapping technique in
air, more experimental investigations need to be implemented for properties such as trapping forces. We studied the
dynamic properties of a micro-sphere (φ8um) optically trapped in air by using a radially or linearly polarized beam.
Firstly in order to predict the trapping forces working on a micro-sphere, the forces are analyzed by a ray-tracing
method. The results show that an axial force of radial polarization is larger than one of linear polarization. Considering
the radial forces, the force of radial polarization is smaller than one of linear polarization. These results can be
understood by noting forces generated by p- and s-polarization. Secondly, we examine the trapping efficiency in optical
trapping experimentally. Radial trapping efficiency is evaluated by measuring a spring constant. Experimental results
and simulated results are in good agreement that the linear polarized beam achieved a 1.25 times higher spring constant
than radial polarization. Axial trapping efficiency is examined by measuring minimum trapping laser power.
Experimental results are one tenth underestimated although qualitatively they are coincident. Radial polarization is
shown to be approximately 2 times higher than linear polarization. Thus, employing radial polarization, the optical
trapping of the glass microsphere in air is achieved by using an objective lens with NA0.80.
Self-assembly is one of the few practical methods for fabricating nanostructures. Currently, the fabrication of a
nanostructure is determined by the initial conditions such as temperature, concentration of the particle, pH balance, etc.
In order to precisely fabricate nanostructure devices using self-assembly, it is necessary to use real-time controlling,
which is based on in-situ evaluations. In this study, we have proposed an in-situ particle sizing system to visualize
interactions between nanocomponents. The system uses two particle sizing methods to cover a range of particle
diameters. In the first method (for diameters of 1-10 nm), particle sizes are evaluated from the rotational diffusion
coefficient of Brownian motion using fluorescence polarization. In the second method (for diameters of 10-500 nm),
particle sizes are evaluated from the diffusion coefficient of a particle tracking method. The system can be integrated into
a fluorescence microscope with a particle tracking system. We constructed an optical system and a particle sizing system
and evaluated their properties.
With the recent development of microfabrication technology, the measurement technology to evaluate geometric
quantities is demanded to assure their accuracy. In order to measure the 3D shape of these microcomponents, a novel
nano-CMM system has been developed based on an oscillated probing technique, which uses an optically trapped
particle. The particle as a probe is trapped by focused laser light using an objective in the air. The trapped particle is
laterally oscillated or circularly at the focal plane of the objective using AOD (acousto-optical deflector).
The motion of the trapped particle is induced by a trapping force toward a focal spot and damped by the viscosity of
the surrounding atmosphere. The frequency response of the oscillated particle typically agrees with the spring-mass-damper
model. On the other hand the response disagrees with the theoretical curve of the model at high frequency range,
i.e. 4.6% at 4000 Hz. It is considered the difference is caused from the numerical error for the fluid effect, which is given
by the stokes formula 6πηr
In this report, we construct a fluid simulation using SMAC method that calculates fluid resistance against an
oscillating sphere in noninertial frame of reference. The fluid effect is investigated in order to improve the model of the
sphere motion. 2D simulation indicates the same tendency in frequency response of the oscillating sphere with
amplitudes of 500 nm in 100-4000 Hz frequency range. 3D simulation could improve the measurement accuracy of
nano-CMM system as compared with 2D simulation.
As a position sensing probe for Nano-CMM which measures three-dimensional shapes of microparts, we propose a novel probing technique using circular motion of an optically trapped microsphere. In this report, a fundamental principle is described for sensing a coordinate on a work surface using a circular motion probe. The circular motion of the trapped sphere near a work surface becomes an ellipse compressed perpendicularly to the surface due to the change of viscous drag of the sphere. The elliptical orbit of the trapped sphere depends on a distance from the surface and a normal vector direction of the surface. By processing the elliptical orbit, the circular motion probe can detect a position and a plane normal vector of the work surface simultaneously. In order to verify feasibility of this method, fundamental experiments are carried out. The circular motion probe is approached to a vertical silicon cleavage surface. The behavior of the trapped sphere near the surface agrees well with the theory. Based on the elliptical orbit of the trapped sphere near the surface, a position and a plane normal vector of the surface are estimated. It is verified that the circular motion probe can detect a position of a work surface with resolution of better than 50nm and detect a plane normal vector of the surface.
For past decades Micro-System Technology (MST) has been developed and it has enabled fabricating the microcomponents on the micro-systems. In order to measure such microcomponents having micrometer-size shapes, a concept of nano-CMM was proposed. According to the concept, nano-CMM specifications are, for example, a measuring range is (10 mm)3 and accuracy is 50 nm. Then, we have proposed a laser trapping probe as a position detecting probe for nano-CMM. The laser trapping probe can be suitable to nano-CMM because of high sensitivity, an availability of a high spherical probe stylus and changeable properties. On the other hands, there are sources of uncertainties, one of them is the standing wave, and the influence is experimentally investigated.
The results reveal the facts such as following. The standing wave obviously influences the behavior of the laser trapping probe sphere. The positional fluctuations by the standing wave proceed several hundreds nm, and the phenomenon appears with high repeatability. A size of the probe sphere can be a crucial parameter for reducing the influence of a standing wave. As another possibility of reducing the influence, on the inclined substrate the probe tends not to be affected by the standing wave. On the other hands, the standing wave influences the probe sphere beyond 100 mm far from the flat silicon substrate.
We suggest a novel 3-D probing technique for measuring micro parts which have high aspect ratio such as a groove or a
deep-hole. This technique uses the optical force exerted on a dielectric microsphere at the tip of optical fiber so called the
fiber optical trapping. A microsphere is trapped at the tip of an optical fiber which has micrometer size of the diameter
and sub micrometer size of the tapered tip. The optical source is a Nd:YAG laser with the wavelength of 1064 nm. A
fiber optical trapping system is quite similar to a conventional CMM. The roll of a microsphere is the same as the probe
sphere of a conventional CMM and an optical fiber works as a stylus shaft. The micro optical fiber part is thinner than
the diameter of the microsphere and longer than the depth of shapes such as deep holes and grooves, which enable to
make an approach to a steep angle surface of a work piece with high aspect ratio.
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