Image displacement sensing (NDSE) for achieving overlay alignment

Picciotto, Carl; Gao, Jun; Hoarau, Eric; Wu, Wei

doi:10.1007/s00339-004-3152-6

Cited by 7 publications

(6 citation statements)

References 20 publications

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“…We feel that the previously demonstrated sub-nanometer precision of nDSE [2,3], coupled with our demonstration of a feasible shallow-mark mold which allows for near-zero displacement measurements and the other advantages outlined at the end of section 2.2, along with the SM-DMA application construct which constructs absolute alignment measurements from relative measurements, indicate the feasibility of low-cost overlay alignment measurements with a precision approaching that of nDSE itself.…”

Section: Discussionmentioning

confidence: 76%

“…Interpolation brings the precision of the displacement estimation to sub-pixel resolution. We discuss nDSE in depth in [2,3]. In those papers we present experimental data demonstrating the precision achievable using nDSE.…”

Section: Review Of Ndsementioning

confidence: 99%

“…First innovation: nDSE nDSE (nanoscale displacement sensing and estimation) is a technique which compares sequential microscopic images of arbitrary micron-scale features to deduce relative displacements at the nanoscale. As we reported in [2,3], nDSE detects displacements using any of a variety of image analysis methods, including cross-correlations and PDD (phase delay detection).…”

Section: Introductionmentioning

confidence: 99%

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Alignment for imprint lithography using nDSE and shallow molds

Picciotto

Gao²,

Yu³

et al. 2009

Nanotechnology

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We present a low-cost overlay alignment metrology solution for nanoimprint lithography that uses optical microscopy, displacement-sensing algorithms, and specially-designed imprint molds that include shallow alignment marks that are visible to the optical system but do not pattern the wafer. This innovation reduces measurement distances to near zero, the optimal distance for displacement-sensing algorithms, and allows for alignment marks to occupy the same piece of wafer real estate without interfering in any way, thus saving silicon area. Additionally, the method we present does not require the comparison of alignment marks between the wafer and the mold, thus removing process variations as a variable. We fabricate the shallow-mark molds, show that the shallow alignment marks indeed do not leave a mark on the wafer, and, implementing our nDSE (nanoscale displacement sensing and estimation) techniques, we demonstrate nanoscale alignment to a precision of 35 nm, 1-sigma. Given sufficient engineering refinement, we would fully anticipate achieving alignment errors down to the 1 nm range using these methods.

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Section: Discussionmentioning

confidence: 76%

Section: Review Of Ndsementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alignment for imprint lithography using nDSE and shallow molds

Picciotto

Gao²,

Yu³

et al. 2009

Nanotechnology

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“…We first reported our findings here. 10 We used broadband white light, so the optical resolving power was clearly less than the pixel resolution. Under the microscope we placed a piezoelectric actuator stage.…”

Section: Ndse Experimental Resultsmentioning

confidence: 99%

From nanoscale displacement sensing and estimation to nanoscale alignment

Gao

Picciotto

et al. 2006

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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In this article, the authors present theoretical background and practical procedures for linking displacement sensing and estimation to nanoscale alignment. The authors discuss the application of nanoscale displacement sensing and estimation (nDSE)-based overlay metrology tool. The authors propose a new look at what constitutes displacement and alignment. From there, the authors develop several frameworks to bridge these two concepts based on a set of new pseudodisplacement concepts and on the careful selection of references. Direct displacement-measurement-based alignment (DDMA) is the first method the authors have used to generate reliable alignment results. The authors achieved sub-100-nm (down to 21nm) alignment accuracy. Indirect displacement-measurement-based alignment (IDMA) is the most accurate method in theory. IDMA truly utilizes nDSE to achieve precision coplacement between different layers and processes. IDMA and DDMA, along with a group of other nDSE-based algorithms/procedures, are vibration tolerant, making them ideal as overlay alignment tools for nanoimprint lithography.

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“…64,65 After the pioneering work on nanoimprint lithography (NIL) by Chou et al demonstrating patterns of 25 nm diameter holes in a PMMA film and the subsequent fabrication of metal pillars by metal deposition and lift-off, 64,65 considerable efforts have been devoted to overcome many challenges associated with NIL. Such efforts include understanding fundamentals related to the process, such as polymer flow behavior during molding and stress and deformation of molded polymers during demolding, [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] developing optimal materials applicable to the NIL process, [84][85][86][87][88][89][90][91][92][93][94][95] overcoming the overlay issue, [96][97][98][99][100][101][102][103][104] fabricating reliable stamps with sub-100 nm features, [105][106]…”

Section: Introduction To Nanomoldingmentioning

confidence: 99%

Flexible fabrication and applications of polymer nanochannels and nanoslits

et al. 2011

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Fluidic devices that employ nanoscale structures (<100 nm in one or two dimensions, slits or channels, respectively) are generating great interest due to the unique properties afforded by this size domain compared to their micro-scale counterparts. Examples of interesting nanoscale phenomena include the ability to preconcentrate ionic species at extremely high levels due to ion selective migration, unique molecular separation modalities, confined environments to allow biopolymer stretching and elongation and solid-phase bioreactions that are not constrained by mass transport artifacts. Indeed, many examples in the literature have demonstrated these unique opportunities, although predominately using glass, fused silica or silicon as the substrate material. Polymer microfluidics has established itself as an alternative to glass, fused silica, or silicon-based fluidic devices. The primary advantages arising from the use of polymers are the diverse fabrication protocols that can be used to produce the desired structures, the extensive array of physiochemical properties associated with different polymeric materials, and the simple and robust modification strategies that can be employed to alter the substrate's surface chemistry. However, while the strengths of polymer microfluidics is currently being realized, the evolution of polymer-based nanofluidics has only recently been reported. In this critical review, the opportunities afforded by polymer-based nanofluidics will be discussed using both elastomeric and thermoplastic materials. In particular, various fabrication modalities will be discussed along with the nanometre size domains that they can achieve for both elastomer and thermoplastic materials. Different polymer substrates that can be used for nanofluidics will be presented along with comparisons to inorganic nanodevices and the consequences of material differences on the fabrication and operation of nanofluidic devices (257 references).

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Image displacement sensing (NDSE) for achieving overlay alignment

Cited by 7 publications

References 20 publications

Alignment for imprint lithography using nDSE and shallow molds

Alignment for imprint lithography using nDSE and shallow molds

From nanoscale displacement sensing and estimation to nanoscale alignment

Flexible fabrication and applications of polymer nanochannels and nanoslits

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