Directed Self-Assembly (DSA) is considered as a potential patterning solution for future generation devices. One of the
most critical challenges for translating DSA into high volume manufacturing is to achieve low defect density in the DSA
patterning process. The defect inspection capability is fundamental to defect reduction in any process, particularly the
DSA process, as it provides engineers with information on the numbers and types of defects. While the challenges of
other candidates of new generation lithography are well known (for example, smaller size, noise level due to LER etc.),
the DSA process causes certain defects that are unique. These defects are nearly planar and in a material which produces
very little defect scattering signal. These defects, termed as “dislocation” and “disclination” have unique shapes and have
very little material contrast. While large clusters of these unique defects are easy to detect, single dislocation and
disclination defects offer considerable challenge during inspection. In this investigation, etching the DSA pattern into a
silicon (Si) substrate structure to enhance defect signal and Signal-to-Noise Ratio (SNR) is studied. We used a Rigorous
Coupled-Wave Analysis (RCWA) method for solving Maxwell’s equations to simulate the DSA unique defects and
calculate inspection parameters. Controllable inspection parameters include various illumination and collection
apertures, wavelength band, polarization, noise filtering, focus, pixel size, and signal processing. From the RCWA
simulation, we compared SNR between “Post-SiN etch” and “Post-SiN+Si-substrate etch” steps. The study is also
extended to investigate wafer-level data at post etch inspection. Both the simulations and inspection tool results showed
dramatic signal and SNR improvements when the pattern was etched into the SiN+Si substrate allowing capture of DSA
unique defect types.
As design rule shrinks, it is essential that the capability to detect smaller and smaller defects should improve. There is considerable effort going on in the industry to enhance immersion lithography using directed self-assembly (DSA) for the 14-nm design node and below. While the process feasibility is demonstrated with DSA, material issues as well as process control requirements are not fully characterized. The chemical epitaxy process is currently the most-preferred process option for frequency multiplication, and it involves new materials at extremely small thicknesses. The image contrast of the lamellar line/space pattern at such small layer thicknesses is a new challenge for optical inspection tools. The study focuses on capability of optical inspection systems to capture DSA unique defects such as dislocations and disclination clusters over the system and wafer noise. The study is also extended to investigate wafer-level data at multiple process steps and to determine the contribution from each process step and materials using defect source analysis methodology. The added defect pareto and spatial distributions of added defects at each process step are discussed.
As design rule shrinks, it is essential that the capability to detect smaller and smaller defects should improve. There is
considerable effort going on in the industry to enhance Immersion Lithography using DSA for 14 nm design node and
below. While the process feasibility is demonstrated with DSA, material issues as well as process control requirements
are not fully characterized. The chemical epitaxy process is currently the most-preferred process option for frequency
multiplication and it involves new materials at extremely small thickness. The image contrast of the lamellar Line/Space
pattern at such small layer thickness is a new challenge for optical inspection tools. In this investigation, the focus is on the capability for optical inspection systems to capture DSA unique defects such as dislocations and disclination clusters over the system and wafer noise. The study is also extended to investigate wafer level data at multiple process steps and determining contribution from each process step and materials using ‘Defect Source Analysis’ methodology. The added defect pareto and spatial distributions of added defects at each process step are discussed.
KEYWORDS: Diffraction, Near field, Wave propagation, Diffraction gratings, Image resolution, Near field optics, Electromagnetism, Radio propagation, Near field scanning optical microscopy, Silver
Recent theoretical and experimental studies have shown that imaging with resolution well beyond the diffraction
limit can be obtained with so-called superlenses. Images formed by such superlenses are, however, in the near
field only, or a fraction of wavelength away from the lens. In this paper, we propose a far-field superlens (FSL)
device which is composed of a planar superlens with periodical corrugation. We show in theory that when an
object is placed in close proximity of such a FSL, a unique image can be formed in far-field. As an example, we
demonstrate numerically that images of 40 nm lines with a 30 nm gap can be obtained from far-field data with
properly designed FSL working at 376nm wavelength.
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