In this research, we propose the 3D measurement system combining structured light and speckle based pose estimation by introducing two different setting cameras. The proposed system consists of two lasers, spot laser and line laser, and two cameras, with and without lens, which can obtain both focused and defocused images at once. Local shapes are measured using focused images by a structured light method. 3D positions of points projected by laser are calculated by triangulation. Pose changes are estimated from speckle information using defocused images. Displacements of speckle patterns are detected as optical ow by Phase Only Correlation (POC) method. Pose changes are estimated from speckle displacements by solving equations derived from the physical nature of speckle. The target shape as a whole is reconstructed by integrating local shapes into common coordinates using estimated pose changes. In the experiment, the texture-less at board was measured with motion. From the experimental results, it is confirmed that the shape of the board was reconstructed correctly by the proposed 3D measurement system.
To use atomic force microscope to measure narrow vertical features is challenging. Using carbon nanotube (CNT) probes is a possible remedy. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring 100-nm-high vertical sidewalls with a 27-nm-diameter and 265-nm-long CNT probe, the probe deflection at the bottom is estimated as large as 5.8 nm. This phenomenon is inevitable when using long and thin probes. We proposed a method to correct this probe deflection effect. Detecting torsional motion of the base cantilever of the CNT probe makes it possible to estimate the CNT probe deflection. Using this information, we have developed a technique for correcting the probe deformation effect from measured profiles. This technique, in combination with correction of the probe shape effect, enables vertical sidewall profile measurement with AFM.
To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in
providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible
alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends
CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring
100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a
bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is
used. We proposed a method to deconvolve this probe deflection effect. By detecting torsional motion of the base
cantilever for the CNT probe, it is possible to estimate the amount of CNT probe deflection. Using this information, we
have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique, in
combination with deconvolution of the probe shape effect, enables vertical sidewall profile measurement.
We have quantitatively evaluated the performance of the proposed method using an improved version of a "tip
characterizers" developed at the National Institute of Advanced Industrial Science and Technology (AIST), which has a
well-defined high-aspect-ratio line and space structure with a variety of widths ranging from 10 to 60 nm. The critical
dimension (CD) values of the line features measured with the proposed AFM method showed good matches to TEMcalibrated
CD values. The biases were within a range of ±1.7 nm for combinations of three different probes, five
different patterns, and two different threshold heights, which is a remarkable improvement from the bias range of ±4.7
nm with the conventional probe tip shape deconvolution method. The static repeatability was 0.54 nm (3σ), compared to
1.1 nm with the conventional method. Using a 330-nm-deep tip characterizer, we also proved that a 36-nm-narrow
groove could be clearly imaged.
To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in
providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible
alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends
CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring
100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a
bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is
used.
We have developed a method of deconvolving this probe deflection effect that is well suited to our AFM scanning mode,
Advanced Step-inTM mode. In this scanning mode, the probe is not dragged on the sample surface but approaches the
sample surface vertically at each measurement point. The CNT probe deformation is stable because we do not use
cantilever oscillation that can cause instability, but we detect static flexure of the cantilever. Consequently, it is possible
to estimate the amount of CNT probe deflection by detecting the degree of cantilever torsion. Using this information, we
have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique in
combination with deconvolution of the probe shape effect makes vertical sidewall profile measurement possible.
A new inline metrology tool utilizing atomic force microscope (AFM) suited for LSI manufacturing at the 45-nm node
and beyond has been developed. The developed AFM is featuring both of high-speed wafer processing (throughput: 30
WPH) and high-precision measurement (static repeatability: 0.5nm in 3σ). Several types of carbon nanotube (CNT)
probes specially designed for the AFM have also been developed. The combination of Advanced StepInTM mode and
CNT probes realizes high precision measurement for high-aspect-ratio samples such as photoresist patterns. In
Advanced StepInTM mode, a probe tip approaches and contacts a sample surface, and then moves away from the surface
and toward a new measurement position. A series of these actions is performed in a short time (3.8 ms for single
measurement point) full-automatically. Advanced StepInTM mode not only ensures gentle probe tip contact and precise
measurement of high aspect ratio samples, but also minimum tip wear. CNT probes can provide long term performance,
while eliminating the need for probe exchange. The developed AFM also realizes flatness measurement of 10-nm level
in a wide area of 40x40-mm maximum. This performance is sufficient for the evaluation of CMP processes at the 45-nm
node.
KEYWORDS: Sensors, Atomic force microscopy, Digital signal processing, Scanners, Signal processing, Silicon, Carbon, Feedback control, Copper, Nondestructive evaluation
Design rule shrinkage and wider adoption of new device structures such as STI, copper damascene interconnects, and
deep trench structures have made the need for in-line process monitoring of step heights and profiles of device
structures more urgent. To monitor active device patterns, as opposed to test patterns as in OCD, AFM is the only non-destructive 3D monitoring tool. The barriers to using AFM in-line monitoring are its slow throughput and the accuracy degradation associated with probe tip wear and spike noise caused by unwanted oscillation on the steep slopes of high-aspect-ratio patterns. Our proprietary AFM scanning method, StepInTM mode, is the method best suited to measuring high-aspect-ratio pattern profiles. Because the probe is not dragged on the sample surface as in conventional AFM, the
profile trace fidelity across steep slopes is excellent. Because the probe does not oscillate and hit the sample at a high
frequency, as in AC scanning mode, this mode is free from unwanted spurious noises on steep sample slopes and incurs
extremely little probe tip wear. To take full advantage of the above properties, we have developed an AFM sensor that is
optimized for in-line use and produces accurate profile data at high speeds and incurs little probe tip wear. The control
scheme we have developed for the AFM sensor, which we call "Advanced StepInTM", elaborately analyses the contact
force signal, enabling efficient probe tip scanning and a low and stable contact force.
With a developed AFM sensor that realizes this concept, we conducted an intensive evaluation on the effect of low and
stable contact force scan. Probes with HDC (high density carbon) tips were used for the evaluation. The experiment
proves that low contact force enhances the measured profile fidelity by preventing probe tip slip on steep slopes.
Dynamics simulation of these phenomena was also conducted, and its results agreed well with the experimental results.
The low contact force scan also incurs extremely little probe tip wear, which is essential to assure high measurement
repeatability. An inherent property of StepInTM is that it causes little probe tip wear because of the minimal contact
between tip and sample. The effects of this property have been enhanced by adding low contact force scanning.
KEYWORDS: Sensors, Atomic force microscopy, Scanners, Digital signal processing, Signal processing, Silicon, Prototyping, Error analysis, Radium, Copper
Design rule shrinkage and the wider adoption of new device structures such as STI, copper damascene interconnects, and deep trench structures have increased the necessity of in-line process monitoring of step heights and profiles of device structures. For monitoring active device patterns, not test patterns as in OCD, AFM is the only non-destructive 3D monitoring tool. The barriers to using AFM in-line monitoring are its slow throughput and the accuracy degradation associated with probe tip wear and spike noise caused by unwanted oscillation on the steep slopes of high-aspect-ratio patterns. Our proprietary AFM scanning method, Step in mode®, is the method best suited to measuring high-aspect-ratio pattern profiles. Because the probe is not dragged on the sample surface as in conventional AFM, the profile trace fidelity across steep slopes is excellent. Because the probe does not oscillate and hit the sample at a high frequency as in AC scanning mode, this mode is free from unwanted spurious noises on steep sample slopes and incurs extremely little probe tip wear. To fully take advantage of the above properties, we have developed an AFM sensor optimized for in-line use, which produces accurate profile data at high speeds.
The control scheme we have developed for the AFM sensor, which we call "Smart Step-in", elaborately analyses the contact force signal, enabling efficient probe tip scanning and a low and stable contact force. The mechanism of the AFM sensor has been optimized for the higher scanning rate and has improved the accuracy, such as the scanning planarity, position and height accuracy, and slope angle accuracy. Our prototype AFM sensor can scan high-aspect-ratio patterns while stabilizing the contact force at 3 nN. The step height measurement repeatability was 0.8 nm (3σ). A STI-like test pattern was scanned, and the steep sidewalls with angles of 84° were measured with high fidelity and without spurious noises.
Convectively coupled, tropical low-frequency distrubances are examined by means of eigenanalysis to the linear dynamical operator based on a T21 multilevel primitive model that involves cumulus convetions and surface heat fluxes. With relevant dissipation terms and an adjustment scheme employed to parameterize the convections, no unstable mode emerges while some of the eigenmodes show decay timescale longer than the intrinsic dissipative timescale. Under the zonally unfiorm basic state, one of these less damped modes has a zonal wavenumber 1 structure with the period of 34dy, which may be considered as a prototype of the Madden-Julian Oscillation (MJO). While a forced Kelvin wave prevails on the equator in this mode, frictional convergence in the boundary layer to the east of heating appears crucial in generating the successive convective heating anomally hence slow eastward propagation of the mode. When we incorporate an idealized Walker circulation into the basic state, a similar mode is obtained with longer period and decay timescale but the structure localized over the Indian Ocean to the western Pacific. It is noteworthy that, however, the 2nd MJ mode is traced back, in the eigenspectrum, to a zonally uniform least damped mode but not to the 1st MJ mode identified under the zonal mean basic state. These results may indicate that the origin of the observed MJO resides in a zonally uniform convective mode which is modified by interacting with the mean Walker circulation, but not in zonal wavenumber 1 modes which have been discusssed in previous studies.
A new range sensing method based on depth from defocus is described. It uses illumination pattern projection to give texture to the object surface. Then the image of the scene is split into two images with different focus settings and sensed simultaneously. The contrast map of the two images are computed and compared pixel by pixel to produce a dense depth map. The illumination pattern and the focus operator to extract the contrast map are designed to achieve finest spatial resolution of the computed depth map and to maximize response of the focus operator. As the algorithm uses only local operations such as convolution and lookup table, the depth map can be computed rapidly on a data-flow image processing hardware. As this projects an illumination pattern and detects the two images with different focus setting from exactly the same direction, it does not share the problem of shadowing and occlusion with triangulation based method and stereo. Its speed and accuracy are demonstrated using a prototype system. The prototype generates 512 by 480 range maps at 30 frame/sec with a depth resolution of 0.3% relative to the object distance. The proposed sensor is composed of off-the-shelf components and outperforms commercial range sensors through its ability to produce complete three-dimensional shape information at video rate.
A new concept of shot-by-shot leveling for high resolution stepper systems, profile-based- leveling, is presented. This detects the wafer surface profile using laser interferometry. From the detected profile, this system determines where on the LSI chip to focus, and controls the wafer stage for focusing and leveling. With an experimental setup, a profile detection repeatability of +/- 0.02 micrometers , a tilt measurement repeatability of +/- 0.24 (mu) rad and a tilt measurement linearity of +/- 1.4 (mu) rad were obtained.
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