Lithography / Nanoimprinting

Download SUSS MicroTec technical publications, white papers and application notes about mask lithography.

Auto-Alignment Insights

This article is the first part of a short series of articles focusing on pattern recognition and alignment in SUSS mask aligners. It is meant as a guideline especially for beginners in the field of pattern recognition, but even more experienced users might find one or the other aspect about pattern recognition which is new to him or her.

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MPT Coating Service Now Available from Compugraphics Jena GmbH

MPT™ Technology (Mask Protection Technology) was developed by Motorola Labs in the 1990s: In order to reduce the usually high mask cleaning frequency when exposing wafers by contact printing a thin film of a fluorinated hydrocarbon polymer is spin coated onto the photomask. Similar to a Teflon coating this fluorinated polymer reduces the surface energy of the mask making it more difficult for resist residues and particles to stick to it. The trans- parency of the mask for broadband or deep UV wavelength is not compromised and the film thickness of approximately 100 nm is small enough to ensure contact printing results comparable to unprotected photomasks.

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3D Topography Mask Aligner Lithography Simulation

In contrast to IC manufacturing where layers are thin and substrates are planar, MEMS, IC packaging, 3D IC, interposer and display appli- cation exhibit a strong 3D topography, typically requiring thick resists to cover the topography. Major lithography challenges of 3D topography are: • Variation of effective distance of mask (proximity gap) and substrate surface • Resist thickness variations • Reflectivity and absorption variation of layer below resist • Complex reflection and diffraction effects on tapered, shadowing on steep sidewalls Experimental verification and optimization of design (mask layout) and exposure conditions is very time consuming and expensive as it cannot be done on planar test wafers. Lithography simulation is an excellent technique for analyzing and optimizing complex scenarios without the need of experiments, and is a stan- dard for high resolution IC manufacturing using projection lithography. For proximity lithography GenISys introduced the LAB simulation software few years ago. Recently, SUSS MicroTec and GenISys enabled “source-mask- optimization” (SMO) for mask aligner, including illumination shaping provided by the new SUSS MO Exposure Optics.

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50 Years SUSS Mask Aligner

This year we are celebrating the 50th anniversary of the SUSS mask aligner. Hardly anybody ever imagined that this type of photolithography equipment that was introduced many decades ago still has its place in today’s manufacturing and research facilities in the semiconductor and related industry.

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Alignment Accuracy in a MA/BA8 Gen3 Using Substrate Conformal Imprint Lithography (SCIL)

Substrate Conformal Imprint Lithography (SCIL) originally invented by Philips Research is an innovative nanoimprint technology. With this technology substrates up to 200 mm can be patterned with features down to a few nanometer  resolution,  delivering  a  unique uniformity of the imprint and the residual layer. The SCIL process was implemented as an option in a standard SUSS Mask Aligner in 2009 and is available on MA/BA6, MA/BA6 Gen3 and MA/BA8 Gen3

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Simulation for Advanced Mask Aligner Lithography

Lithography simulation has been a key enabler for IC manufacturing to keep track with Moore’s law. 30 years ago, the end of optical lithography had been projected for feature sizes smaller than 1 µm. Just now, Intel announced 1 that they will still use optical lithography for the nodes down to 14 nm. Without lithography simulation and the simulation based source mask optimization technology this would never have been possible.

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Numerical Resolution Enhancement in Mask Aligner Lithography

Simulation-based techniques extend the limits of lithography for applications that benefit from the cost advantage of mask aligners and their capability to print on large and non-planar substrates.

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Ordered Arrays of Nanoporous Gold Nanoparticles

A combination of a “top-down” approach (substrate-conformal imprint lithography) and two “bottom-up” approaches (dewetting and dealloying) enables fabrication of perfectly ordered 2-dimensional arrays of nanoporous gold nanoparticles. The dewetting of Au/Ag bilayers on the periodically prepatterned substrates leads to the interdiffusion of Au and Ag and the formation of an array of Au–Ag alloy nanoparticles. The array of alloy nanoparticles is transformed into an array of nanoporous gold nanoparticles by a following dealloying step. Large areas of this new type of material arrangement can be realized with this technique. In addition, this technique allows for the control of particle size, particle spacing, and ligament size (or pore size) by varying the period of the structure, total metal layer thickness, and the thickness ratio of the as-deposited bilayers.

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Advanced mask aligner lithography: New illumination system

A new illumination system for mask aligner lithography is presented. The illumination system uses two subsequent microlens-based Köhler integrators. The second Köhler integrator is located in the Fourierplane of the first. The new illumination system uncouples the illuminationlight from the light source and provides excellent uniformity of the light irradiance and the angular spectrum. Spatial filtering allows to freely shape the angular spectrum to minimize diffraction effects in contact andproximity lithography.

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Formation of precise 2D Au particle arrays via thermally induced dewetting on pre-patterned substrates

The fabrication of precise 2D Au nanoparticle arrays over a large area is presented. The technique was based on pre-patterning of the substrate before the deposition of a thin Au film, and the creation of periodic particle arrays by subsequent dewetting induced by annealing. Two types of pre-patterned substrates were used: The first comprised an array of pyramidal pits and the second an array of circular holes.

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Techniques for removal of contamination from EUVL mask without surface damage

Mask defectivity is an acknowledged road block for the introduction of EUV lithography (EUVL) for manufacturing. There are significant challenges to extend the conventional methods of cleaning developed for standard 193nm opticalphotomask to meet the specific requirements for EUV mask structure and materials. In this work, the use of UV activated media for EUV mask surface cleaning is evaluated and the effects on Ru capping layer integrity are comparedagainst conventional cleaning methods. Ru layer surface is analyzed using roughness measurements (AFM) and reflectivity changes (EUV-R and optical).

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Study on surface integrity in photomask resist strip and final cleaning processes

In this paper SUSS MicroTec demonstrates the use of an alternative acid-free resist strip and cleaning process, which not only overcomes the named drawbacks of conventional ozone water use, but reduces resist strip time by 50% to 75%. The surface materials investigated during this study are; chrome absorber layers on binary masks, MoSi based shifters, chrome hard mask layers on EPSM, and ruthenium capping layers on EUV masks. Surface material integrity and CDstability results using this new, acid-free approach are presented in the following pages.

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Automated imprint mask cleaning for Step-and-Flash Imprint Lithography

Preservation of mask cleanliness is essential to avoid risk of repeated printing of defects. The development of mask cleaning processes capable of removing particles adhered to the mask surface without damaging the mask is critical to meet high volume manufacturing requirements. In this paper we have presented various methods of residual (crosslinked) resist removal and final imprint mask cleaning demonstrated on the SUSS MicroTec MaskTrack automated mask cleaning system. Conventional and non-conventional (acid free) methods of particle removal have been compared and the effect of mask cleaning on pattern damage and CD integrity is also studied.

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Reduction of Local CD-Linewidth Variations in Resist Develop through Acoustic Streaming

The ASonic® nozzle developed by SUSS MicroTec combines the very favorable dark loss, defect and global CD-linewidth control benefits of a fast and uniform low impact initial develop dispense (surface wetting), with an enhanced developer agitation through acoustic streaming, which provides improved local CD-control independent of pattern size and loading.

The principle functionality of the ASonic® nozzle is described. Developing loading effect is examined with various conditions and CD linearity, proximity and CD uniformity are also verified.

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Full Field Nano Imprint on Mask Aligners Using Substrate Conformal Imprint Lithography Technique

Nowadays, the development of inte-grated circuit (IC) industry and scien-tific researches rely more and more on the nanofabrication technologies. The resolution limits of optical lithog-raphy are very real even with a number of “optical tricks” at work. E-beam lithography (EBL) provides excellent resolution down to several nanometers. However, the throughput of EBL is too low for mass production due to its scanning exposure principle. Nano imprint lithography (NIL) has been included on the ITRS lithography roadmap for 32 nm, 22 nm and 16 nm nodes. This parallel patterning technique shows great potentials in fabrication of nanostructures with high resolution at low costs.

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Half-Tone Proximity Lithography

We show that a wide range of different micro-optical structures can be optimized by controlling the light diffraction in proximity lithography. Parameter settings were found for submicron binary pattern up to continuous profile structures with extensions up to several tens of microns. An additional interesting application of this approach is the combination of binary and continuous profiles in single elements, e.g. micro lenses with diffractive correction or AR structures. Experimental results achieved for blazed gratings with a period of 2 microns are presented

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Imprintlithografie stempelt nanostructuren in grote oppervlakken

Substrate conformal imprint lithography (Scil) is een ontwikkeling van Philips Research. Süss Microtec Lithography produceert in licentie de benodigde tooling. Het innovatieve aan de techniek is dat met zeer nauwkeurige semiflexibele stempels nanostructuren in substraten kunnen worden aangebracht. Dit gaat niet alleen veel sneller maar ook een stuk goedkoper dan met welke andere bestaande techniek ook. Toepassing is de productie van kleinere en krachtigere ledlampen, maar ook lasers en RFID-chips kunnen hiermee goedkoper worden gemaakt.

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Application of the SUSS Angular Exposure System to Fabricate True-Chip-Size Packages for SAW Devices

SAW filters are key components for mobile communication. Size reduction of SAW filters allows for further miniaturisation of mobile phones and an extension of their functionality. The miniaturisation of the devices demands also a reduction of the package size. To address the packaging requirements EPCOS has developed the Die Sized SAW Package (DSSP), a true chip-size wafer level package for SAW filters. The key for the realization of this package are the 3D-interconnects.

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Reduction of Proximity Induced Corner Artifacts by Simulation Supported Process Optimization

Reducing proximity artifacts is the most common challenge occurring in mask aligner lithography especially when exposing substrates at larger proximity gaps. Typically, proximity artifacts are most prominent at positions where the symmetry of the structures that should be produced is broken, i.e. line ends or corners. The tests presented here focused on various process parameters expected to influence the occurrence of proximity induced corner artifacts, including geometrical design of the mask structures, as well as exposure optics, gap and dose. It could be shown, that the artifacts can greatly be reduced by a combined optimization of the parameters stated before.

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Substrate Conformal Imprint Lithography of Functional Materials - Review of a BFS-Project

Substrate conformal imprint lithography (SCIL) is an innovative full wafer scale nanoimprint technology [1] . This sub-micrometer patterning method uses flexible PDMS stamps for the structure transfer. Originally, SCIL technology was developed for the transfer of structures into sol gel materials which hardened via diffusion of solvents into the PDMS stamp material. The work of Ji et al. [2] showed the extension of SCIL to UV-enhanced SCIL (UV-SCIL). With this new option, UV curable materials can be used as resists for the SCIL-method.

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Spray Coating Negative Tone Resists

Spray coating is an essential coating technology for depositing resists across deeply etched structures, such as a MEMS device etched deeper than 100 µm. Conventional spin coating has limitations when processing structured wafers with severe topography. Spin coated resist often fills the entire structure. This leads to difficulties in the following lithography steps. Thus, industry requires a method to apply resist conformally. Spray coating technology is an effective method for performing conformal coating over deep etched structures.

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