Defect inspection for imprint lithography using a die-to-database electron beam verification system

Abstract

Imprint lithography has been included on the ITRS Lithography Roadmap at the 32 and 22 nm nodes.Step and Flash Imprint Lithography (S-FIL TM ) is a unique method for printing sub-100 nm geometries. Relative to other imprinting processes S-FIL has the advantage that the template is transparent, thereby facilitating conventional overlay techniques. Further, S-FIL provides sub-100 nm feature resolution without the significant expense of multielement, high quality projection optics or advanced illumination sources. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates.With respect to inspection, although defects as small as 70 nm have been detected using optical techniques, it is clear that it will be necessary to take advantage of the resolution capabilities of electron beam inspection techniques. This paper reports the first systematic study of die-to-database electron beam inspection of patterns that were imprinted using an Imprio 250 system. The die-to-database inspection of the wafers was performed on an NGR2100 inspection system. Ultimately, the most desirable solution is to directly inspect the fused silica template. This paper also reports the results on the first initial experiments of direct inspection fused silica substrates at data rates of 200 MHz.Three different experiments were performed. In the first study, large (350 -400 nm) Metal 1 and contact features were imprinted and inspected as described above. Using a 12 nm pixel address grid, 24 nm defects were readily detected. The second experiment examined imprinted Metal 1 and Logic patterns with dimensions as small as 70 nm. Using a pixel address of 3 nm, and a defect threshold of 20 nm, a systematic study of the patterned arrays identified problem areas in the design of the pattern layout. Finally, initial inspection of 200 mm fused silica patterned substrates has established proof of concept for direct inspection of imprint templates.

An effective image segmentation technique for the SEM image

“…Human eye inspection is however very exhaustive and unreliable to test all images so that there have been many efforts to replace the human eye inspection by automatic inspection [1,4,5,8,9]. For automatic inspection, the two types of comparison methods, direct and indirect method, have been introduced.…”

“…2D image can be segmented by the watershed segmentation algorithm [4], especially the flood background method. If the watershed segmentation is used directly, each basin's boundary is located at the middle of edge component and its shape is different with the source image.…”

Front Matter: Volume 6521

“…The KLA ES-32 tool has proved to be effective (12) in detecting sub 50nm defects using a die to die approach as shown in Figure 6a. For die to data base results, NGR (13) has been able to detect 20nm defects using its 2100 tool, as shown in Figure 6b. Repair of template defects can either be completed by mechanical removal of excess material (14) using a Rave 650NM tool, or by replacing missing material using a Nowatech MeRiTMG ebeam (15) enhanced deposition system.…”

Net tracing and classification analysis on E-beam die-to-database inspection

“…One of the most effective ways of detecting systematic inter-layer defects is by E-Beam Voltage Contrast (VC) Die-to-Database (D2DB) inspection [1]. E-Beam D2DB can effectively detect an open via and critical dimension (CD) shrinkage by comparing the voltage contrast images of vias to the design layout [2] . However, the reported DVC defects cannot be used directly, since they contain a mix of false alarm defects and real DVC defects.…”