Proc. SPIE. 8378, Scanning Microscopies 2012: Advanced Microscopy Technologies for Defense, Homeland Security, Forensic, Life, Environmental, and Industrial Sciences
KEYWORDS: Nanotechnology, Microscopes, Microscopy, Electron microscopes, Scanning electron microscopy, Mathematics, Outreach programs, Photomicroscopy, Scanning transmission electron microscopy, Standards development
The future of our nation hinges on our ability to prepare our next generation to be innovators in science, technology,
engineering and math (STEM). Excitement for STEM must begin at the earliest stages of our education process. Yet,
today far too few of our students are prepared for the challenges ahead. Several initiatives are trying to change this
situation. “Microscopy for STEM Educators” was an initiative that demonstrated the value of incorporating microscopy
into STEM education. Several notable invited speakers discussed their successful programs implementing microscopy
in STEM education in order to foster student interest and excitement. A hands-on session with table-top scanning
electron microscopes was held at the end of the presentations and the attendees were encouraged to bring samples
of interest and operate the instruments. This paper outlines some of the accomplishments and goals of this session.
A novel through-focus scanning optical microscopy (TSOM) method that yields nanoscale information from optical
images obtained at multiple focal planes will be used here for nanoparticle dimensional analysis. The TSOM method can
distinguish not only size differences but also shape differences among nanoparticles. Size evaluation based on
simulations will be presented along with experimental data for nanoparticles and nanodots with sizes below 100 nm. Size
determination using an experimentally created library will also be presented.
Proc. SPIE. 5375, Metrology, Inspection, and Process Control for Microlithography XVIII
KEYWORDS: Electron beams, Metrology, Interferometers, Calibration, Control systems, Scanning electron microscopy, Motion measurement, Control systems design, Standards development, Laser systems engineering
The National Institute of Standards and Technology (NIST) has implemented a high bandwidth laser interferometer measurement system in a specialized metrology microscope. The purpose of the system is the certification of SEM magnification calibration samples by moving the sample under a finely focused stationary electron beam in the metrology electron microscope. Using a laser interferometer with displacement measurements traceable to basic wavelength standards, the motion is measured while recording the secondary or backscattered electron output signal. The recent upgrade to the laser measurement system enables a measurement bandwidth of 300 kHz to be achieved in the sampling of the X-Y position of a test sample, along with measuring the intensity of the secondary electron beam output signal. This high bandwidth stage position measurement capability becomes a tool to measure the effects of environmental vibrations on SEM measurements. This paper outlines this ongoing research and presents the current results along with details of the measurement possibilities based on this new technique.
The development of a very fast, very accurate laser stage measurement system facilitates a new method to enhance the image and line scan resolution of scanning electron microscopes (SEMs). This method, allows for fast signal intensity and displacement measurements, and can report hundreds of thousands of measurement points in just a few seconds. It is possible then, to account for the stage position in almost real time with a resolution of 0.2 nm. The extent and direction of the stage motion reveal important characteristics of the stage vibration and drift, and helps to minimize them. The high accuracy and speed also allows for a convenient and effective technique for diminishing these problems by correlating instantaneous position and imaging intensity. The new measurement technique gives a possibility for significantly improving SEM-based dimensional measurement quality.
The National Institute of Standards and Technology (NIST) has provided industry with a scanning electron microscope (SEM) magnification calibration sample Reference Material (RM) 8090. The certified, Standard Reference Material (SRM) version, SRM 2090 is currently being prepared for issuance. This paper describes the design and development of a new, PC-based measurement and control system developed to facilitate the certification of the SRM 2090 artifact samples in a specialized metrology microscope. SRM 2090 is certified by moving the sample under a finely focused stationary electron beam in the metrology electron microscope. Using a laser interferometer with displacement measurements traceable to basic wavelength standards, the motion is measured while recording the secondary or backscattered electron output signal. A computer controls the motion, records the signal and interferometer value, then calculates the accurate spacing of the features, completes the statistical work and generates the NIST certificate. The original measurement system design was developed in the early 1990s. This paper outlines the effort to upgrade the system, including the replacement of the outdated measurement and control system with a new, LabVIEW based measurement and control system. The details of the new measurement and control system will be discussed and results will be presented.
This paper describes the design and implementation of a system for monitoring the performance of several major subsystems of a critical dimension measurement scanning electron microscope (CD-SEM). Experiments were performed for tests involving diagnosis of the vacuum system and column stability by monitoring of the following subsystems and associated functional parameters. These include: 1) Vacuum system with pressure as a function of time being recorded for the electron-optical column (gun chamber), the specimen chamber, and the sample-loading unit. 2) The action of several components of the wafer handling system can be timed. 3) The electron gun emission currents and other signals to monitor the characteristics of the condenser and objective lenses may be used to correlate with image quality. 4) Image sharpness, electron beam current, signal-to-noise ratio, etc. can be evaluated.