KEYWORDS: Semiconducting wafers, Photomasks, Line width roughness, Inspection, Wafer inspection, Scanning electron microscopy, Defect detection, Signal to noise ratio, Extreme ultraviolet lithography, Line edge roughness
EUVL is the strongest candidate for a sub-20nm lithography solution after immersion double-patterning. There are still
critical challenges for EUVL to address to become a mature technology like today's litho workhorse, ArF immersion.
Source power and stability, resist resolution and LWR (Line Width Roughness), mask defect control and infrastructure
are listed as top issues. Source power has shown reasonably good progress during the last two years. Resist resolution
was proven to resolve 32nm HP (Half Pitch) lines and spaces with good process windows even though there are still
concerns with LWR. However, the defectivity level of blank masks is still three orders of magnitude higher than the
requirement as of today.
In this paper, mask defect control using wafer inspection is studied as an alternative solution to mask inspection for
detection of phase defects on the mask. A previous study suggested that EUVL requires better defect inspection
sensitivity than optical lithography because EUVL will print smaller defects. Improving the defect detection capability
involves not only inspection system but also wafer preparation. A few parameters on the wafer, including LWR and
wafer stack material and thickness are investigated, with a goal of enhancing the defect capture rate for after
development inspection (ADI) and after cleaning inspection (ACI). In addition to defect sensitivity an overall defect
control methodology will be suggested, involving mask, mask inspection, wafer print and wafer inspection.
The process of drug discovery can be accelerated by increasing the information content of bioassays and by employing assay platforms that are amenable to high throughput screening techniques. In this paper, we demonstrate how the combination of soft lithography with controlled surface chemistry achieves these goals in a wide spectrum of bioassays. A number of soft lithographic methods can be used to generate micro-structures for the purposes of increasing assay density, diversity of test conditions and improving assay detection qualities. In addition, soft lithography, combined with specific surface chemistry modification procedures and protein engineering, may be used to control the localized molecular and biological properties of substrates, thereby enabling the development of new types of bioassays. The developed methodologies are simple, easily implemented, and lend themselves well to automation. Experimental results and prototypes are presented to illustrate the capabilities of these new techniques. For example, soft lithography and surface chemistry are employed for chemically patterning substrates, stenciling biological entities onto substrates and confining solutions. As a result, information-rich, highdensity bioassays can be obtained where biological targets, surface properties and medium solutions are carefully determined and controlled.
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