Dual-Probe CD-AFM Calibration
National Institute of Standards and Technology, SBIR Phase II
Start Date: September 15, 2004
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Xidex is demonstrating the feasibility of calibrating a critical-dimension
atomic force microscope (CD-AFM) without the use of a reference artifact
in such a way that high-precision critical dimensions can be generated
independently of changes in probe tip shape (including the effects of tip
wear), and in the presence surface force uncertainties, and stage
uncertainties. The calibration method relies on tip-to-tip based
calibration with a dual-probe CD-AFM architecture. The Phase II work is
directed at demonstrating sub-nanometer repeatability for tip-to-tip
calibration, and critical-dimension measurements which verify that
tip-to-tip calibration removes the effects of tip shape variation and tip
wear from linewidth measurements. Phase II will provide critical design
guidance for both controller design and MEMS fabrication of probes and
tips suitable for use with a commercial dual-probe system. This design
guidance will be based on a complete characterization of the calibration
and measurement sequence for a dual probe CD-AFM. These are the next
steps on a path to the commercial NanoCaliperTM
CD-AFM tool.
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Dual-Probe CD-AFM Calibration
Start Date: July 10,
2003
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Xidex demonstrated the feasibility of calibrating a critical-dimension
atomic force microscope (CD-AFM) without the use of a reference artifact
in such a way that high-precision critical dimensions can be generated
independently of changes in probe tip shape (including the effects of tip
wear), presence of the surface force uncertainties, and the stage
uncertainties. The calibration method relies on a tip-to-tip based
calibration with a dual-probe CD-AFM architecture. The method adopts an
alternative approach that rejects model-dependence in favor of an entirely
new dual-scanning-probe NanoCaliperTM
architecture that is virtually model-independent. The prospect of
removing the major sources of uncertainty in scanning probe tools provides
an exciting opportunity to demonstrate a revolutionary new breed of CD-AFM
tool that paves the way for scanning probe measurements that are both
precise (i.e., highly repeatable) and accurate (i.e., traceable to
reference artifacts). Results of the Phase I SBIR research enabled us to
quantify the achievable repeatability of a tip-to-tip calibration
procedure. Once fully demonstrated, this calibration procedure will be
used with the NanoCaliperTM CD-AFM commercial
tool.
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Develop and Demonstrate a Prototype Six Degree of Freedom AFM
Metrology Tool
SEMATECH PROJECT, Start Date: December 1, 1998
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Xidex Corporation successfully demonstrated a prototype Critical Dimension
Atomic Force Microscope (CD AFM) that uses a tilted cantilever system to
access vertical and highly re-entrant sidewalls with standard, sharp 1-D
silicon tips. Complementary product development work at Xidex has resulted
in a proprietary process for scaleable manufacturing of carbon nanotubes
as structural elements of MEMS devices. By using carbon nanotube tips
manufactured for CD metrology applications, the Xidex CD AFM can image all
projected feature sizes and more challenging reentrant geometries. Our CD
AFM also incorporates innovative force sensing technology that enables
true 3-D surface metrology by providing simultaneous control in multiple
directions.
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High-Throughput, Multiple Scanned-Head Critical Dimension Atomic Force
Microscope (CD-AFM)
National Science Foundation, SBIR Phase I
Project, Start Date: July 1, 2001
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Xidex demonstrated the feasibility of developing a multiple scanned-head
Critical Dimension Atomic Force Microscope (CD-AFM) with the throughput
comparable to that of CD Scanning Electron Microscopes (CD-SEMs), the
semiconductor industry's primary CD metrology tool for in-line production
quality control.
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Six Degree-of-Freedom Atomic Force Microscopes, Phase II
National Science Foundation, SBIR Phase II Project, Start Date: July 15,
1999
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This Small Business Innovation Research Phase II Project demonstrated
unique capabilities at Xidex's Six Degree-of-Freedom Atomic Force
microscope (6-DOF AFM) technology for use as a critical dimension (CD)
metrology tool by semiconductor industry. Our CD-AFM design accommodates
tilting of the AFM cantilever through large anqular ranges, thereby
enabling the probe tip to access undercuts and re-entrant features. Our
sensing system tracks the AFM cantilever in up to 6 degrees-of-freedom.
The CD-AFM also allows operating the cantilever and tip in the X, Y, and Z
directions, enabling is to determine 3-D surface slopes. This enables a
scanning strategy where the raster step in Y can be altered for faster AFM
imaging and better inspection of profiles in Y. Another advantage is
elimination of cosine errors due to cantilever bending and tilt, vertical
tip-sample alignment, and X and Y orthogonality error. The semiconductor
industry recognizes that a viable alternative to CD-scanning electronic
microscope (CD-SEM) technology will be required within the next few years.
The shortcomings of CD-SEMs present an opportunity to develop a new
AFM-based CD metrology tool to meet urgent needs of the National
Technology Roadmap for production quality control at exremely small
feature sizes. Commercial applications include critical dimension (CD)
metrology tools for inline production quality control in semiconductor
fabrication facilities and tools for calibration of CD scanning electron
microscopes (SEMs).
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Six Degree-of-Freedom Atomic Force Microscopes, Phase I
National Science Foundation, SBIR Phase I Project, Start Date: January 1,
1998
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This Small Business Innovation Research Phase I project demonstrated the
feasibility of a new generation of Six Degree-of-Freedom (Six-DOF) Atomic
Force Microscope (AFM) tools for use in microelectronics manufacturing
that overcome limitations inherent in the sensing and control system
architectures of existing lower degree-of-freedom AFMs. This Six-DOF
sensing system is capable of measuring all six absolute degrees of freedom
of a body of space, such as a deflecting AFM cantilever. Xides calls the
resulting new generation of tools "6D-AFM" tools. 6D-AFMs will be used for
material characterization, chemical-mechanical planarization monitoring,
precision surface profiling and critical dimension metrology. The sensing
system of a 6D-AFM is completely decoupled from the actuator, enabling it
to measure at even better resolutions than the actuator itself, and do so
while the actuator is in motion. Commercial applications include: material
characterization, critical dimension metrology, and precision surface
profiling and to other attractive market segments and niches such as
lithography, biological sampling, and nanoprobe research instrumentation.
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