We have demonstrated the successful operation of a multi-beam scanning electron microscope with 331 electron beams for the first time. This makes it the world’s fastest SEM. The underlying architecture of the existing multi-beam mSEM technology fully supports the scale-up of the number of electron beams to 331. Scaling beyond this number is feasible.
We use the ZEISS MultiSEM to inspect patterns on separated chips of a semiconductor wafer suited for process window characterization at imec-N10 logic node. We systematically analyze the impact of imaging parameters of the MultiSEM on quantitative metrics extracted from the images, e.g., CD repeatability and relative defect capture, and demonstrate that the MultiSEM is able to image the wafer patterns, track their variations through the process conditions of the lithography scanner, and consistently find patterning defects limiting the lithographic process window.
Electron optics can assist in the fabrication of semiconductor devices in many challenges that arise from the ongoing decrease of structure size. Examples are augmenting optical lithography by electron beam direct write strategies and high-throughput imaging of patterned structures with multiple beam electron microscopes. We use multiple beam electron microscopy to image semiconductor wafers processed by electron beam lithography.
The new device architectures and materials being introduced for sub-10nm manufacturing, combined with the complexity of multiple patterning and the need for improved hotspot detection strategies, have pushed current wafer inspection technologies to their limits. In parallel, gaps in mask inspection capability are growing as new generations of mask technologies are developed to support these sub-10nm wafer manufacturing requirements. In particular, the challenges associated with nanoimprint and extreme ultraviolet (EUV) mask inspection require new strategies that enable fast inspection at high sensitivity. The tradeoffs between sensitivity and throughput for optical and e-beam inspection are well understood. Optical inspection offers the highest throughput and is the current workhorse of the industry for both wafer and mask inspection. E-beam inspection offers the highest sensitivity but has historically lacked the throughput required for widespread adoption in the manufacturing environment. It is unlikely that continued incremental improvements to either technology will meet tomorrow’s requirements, and therefore a new inspection technology approach is required; one that combines the high-throughput performance of optical with the high-sensitivity capabilities of e-beam inspection.
To support the industry in meeting these challenges SUNY Poly SEMATECH has evaluated disruptive technologies that can meet the requirements for high volume manufacturing (HVM), for both the wafer fab [1] and the mask shop. Highspeed massively parallel e-beam defect inspection has been identified as the leading candidate for addressing the key gaps limiting today’s patterned defect inspection techniques. As of late 2014 SUNY Poly SEMATECH completed a review, system analysis, and proof of concept evaluation of multiple e-beam technologies for defect inspection. A champion approach has been identified based on a multibeam technology from Carl Zeiss. This paper includes a discussion on the need for high-speed e-beam inspection and then provides initial imaging results from EUV masks and wafers from 61 and 91 beam demonstration systems. Progress towards high resolution and consistent intentional defect arrays (IDA) is also shown.
E-beam based technologies are widely used for metrology applications in both wafer fabs and mask shops due to their intrinsic high resolution capabilities. However, the throughput requirements for defect inspection are orders of magnitude higher than what is traditionally achievable with electron beam technologies. We have developed a novel multi-electron beam based technology to address the existing need for high speed imaging of nanoscale patterns. This technique enables ultra-high image acquisition rates which scale with the number of electron beams. In this article the technology development status and imaging results will be shown, including first results with the multi-beam SEM on EUV masks.
SEMATECH aims to identify and enable disruptive technologies to meet the ever-increasing demands of semiconductor high volume manufacturing (HVM). As such, a program was initiated in 2012 focused on high-speed e-beam defect inspection as a complement, and eventual successor, to bright field optical patterned defect inspection [1]. The primary goal is to enable a new technology to overcome the key gaps that are limiting modern day inspection in the fab; primarily, throughput and sensitivity to detect ultra-small critical defects. The program specifically targets revolutionary solutions based on massively parallel e-beam technologies, as opposed to incremental improvements to existing e-beam and optical inspection platforms. Wafer inspection is the primary target, but attention is also being paid to next generation mask inspection. During the first phase of the multi-year program multiple technologies were reviewed, a down-selection was made to the top candidates, and evaluations began on proof of concept systems. A champion technology has been selected and as of late 2014 the program has begun to move into the core technology maturation phase in order to enable eventual commercialization of an HVM system. Performance data from early proof of concept systems will be shown along with roadmaps to achieving HVM performance. SEMATECH’s vision for moving from early-stage development to commercialization will be shown, including plans for development with industry leading technology providers.
KEYWORDS: Scanning electron microscopy, Sensors, Electron beams, Signal to noise ratio, Image resolution, Semiconductors, Beam splitters, Brain, Image processing, Microscopy
Multiple electron beam SEMs enable detecting structures of few nanometer in diameter at much higher throughputs than possible with single beam electron microscopes at comparable electron probe parameters. Although recent multiple beam SEM development has already demonstrated a large speed increase1, higher throughputs are still required to match the needs of many semiconductor applications2. We demonstrate the next step in the development of multi-beam SEMs by increasing the number of beams and the current per beam. The modularity of the multi-beam concept ensures that design changes in the multi-beam SEM are minimized.
KEYWORDS: Scanning electron microscopy, Electron beams, Sensors, Data acquisition, Image resolution, Beam splitters, Electron microscopes, Brain, Tissues, Silicon
Conventional scanning electron microscopes are limited in their ultimate data acquisition rate at a given resolution by
statistical electron-electron interaction (so-called Coulomb interaction) as well as band width of detectors and deflection
systems. We increased imaging speed dramatically by using multiple electron beams in a single column and parallel
detection of the secondary electrons. The multi-beam SEM generates multiple overlapping images during a single scan
pass, thereby covering a larger area in shorter time as compared to a single-beam SEM at the same pixel size. This
addresses the upcoming need for high speed imaging at electron microscopic resolution to investigate larger and larger
areas and volumes.
High harmonics produced in aligned molecules contain the structural information of bound-state electronic states. We
have produced high harmonics from N2 molecules aligned to arbitrary directions with 5-degrees steps. From the set of
high harnionic spectra, we have successfully reconstructed tomographic images of the highest occupied molecular
orbital (HOMO) of N2.
High harmonics produced in aligned molecules contain the structural information of the outermost electron orbital that preferentially ionizes in intense laser fields. We show a method to reconstruct a 3-dimensional (3D) structure of the molecular orbital. The method is based on the technologies to align molecules and to produce attosecond XUV pulses, both of which utilize intense ultrashort laser pulses. We measured a set of high harmonic spectra produced in differently aligned N2 molecules, and successfully reconstructed the image of the highest occupied molecular orbital (HOMO) with sub-angstrom resolution.
We have investigated the full three dimensional momentum correlation between the electrons emitted from strong field double ionization of neon when the re-collision energy of the first electron is on the order of the ionization potential of the singly charged neon ion. We find that the momentum correlation in the direction perpendicular to the laser field depends on the time difference of the two electrons leaving the ion. Our results are consistent with double ionization proceeding through transient double excited states that field ionize.
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