Interferometric Analysis Assures Precise Lithographic Imprint Registration in Nano-Scale Device Production

An interferometric analysis tool (iMAT®) for imprint nanolithography that achieves precise registration and mold curing is disclosed in U.S. Patent 7,630,067.  Molecular Imprints, Inc. (Austin, TX) inventors Pawan Kumar Nimmakayala,  Tom H. Rafferty, Alireza Aghili, Byung-Jin Choi, Philip D. Schumaker, Daniel A. Babbs, and Van N. Truskett developed an interferometric analysis method that determines relative spatial parameters between two coordinate systems, which may be an imprint mold and a region of a substrate in which mold is employed to generate a nanoscale pattern. The method includes sensing relative alignment between the two coordinate systems at multiple points and determines relative spatial parameters there between. The relative spatial parameters include a relative area and a relative shape. 

Nano-scale fabrication involves the fabrication of very small structures, e.g., having features on the order of one nano-meter or more. A promising process for use in nano-scale fabrication is known as imprint lithography. 

Specifically, interferometric analysis determines the relative spatial parameters between mold and substrate region, the processor then generates control signals to regulate the operation so that desired registration between mold and substrate region is achieved. Registration is demonstrated by detectors and sensing images as having a desired offset and as having no offset. 

In a typical alignment process the measurements are taken as the distance between mold and region varies, e.g. becoming closer in proximity along the Z-direction. For example, the measurements and control signals may be generated when mold and substrate are spaced-apart a distance of 4 microns, 1 micron or a final distance in which a volume is defined therebetween that is substantially filled with polymeric material. As a result, the spatial parameters may be determined and control signals generated in real time during the imprinting process so as to minimize relative spatial parameters between mold and imprint region that are undesirable in forming nano-scale electronic circuitry.   

During curing of imprinting material by hardening or cross-linking, the very photons that are needed for curing may also cause heating of mold and imprint region. If the intensity of curing light is maintained reasonably uniform, mold and substrate may heat up uniformly. The differential heating and/or the differential coefficient of thermal expansion (CTE) can cause alignment mismatches during exposure up to the point where the imprinting material has not jelled to behave like a solid that adheres to the substrate. However, the average misalignment may either be estimated by simulations or by using the alignment measurement systems described here, and the size of the mold or substrate can be pre-corrected in such a way that a desired scaling (magnification) mismatch is achieved using the iMAT  just prior to curing. It is desirable that the wavelengths used for alignment metrology need to be substantially different from the curing light. 

Referring to FIG. 3, the present invention includes an imprint lithography system 50 that has a template 52, retained within a template stage 54, a substrate 56 supported upon a substrate stage 60 and an interferometric analysis tool (iMAT.TM.) 62 is in optical communication with both template 52 and substrate 56. Also present are a polymeric fluid dispensing system and a source of actinic radiation, both of which are typically included in imprint lithography systems, but are not shown for clarity. An exemplary template stage includes a chucking system (not shown) and an actuator sub-assembly (not shown) coupled to imprint head 20 through a flexure system.

iMAT.TM. 62 is coupled with both stages 54 and 60 to communicate therewith over feedback loop 64 to facilitate proper spatial arrangement between two coordinate systems, one defined by template 52 and one defined by substrate 56 to obtain a desired spatial arrangement therebetween. To that end, iMAT.TM. 62 produces data concerning multiple spatial parameters of both template 52 and substrate 56 and determines signals in response thereto to ensure differences between the spatial parameters are within desired tolerances. To that end, iMAT.TM. 62 is coupled to sense one or more of alignment marks on template 52, referred to as template alignment marks 65, as well as one or more of the alignment marks on substrate 56, referred to as substrate alignment marks 66. iMAT.TM. 62 can determine multiple relative spatial parameters of template 52 and substrate 56 based upon information obtained from sensing alignment marks 65 and 66. The spatial parameters includes misalignment therebetween, along X and Y directions, as well as relative size difference between substrate 56 and template 52 in the X and Y directions, referred to as a relative magnification/run out measurement, and relative non-orthogonality of two adjacent transversely extending edges on either template 52 and/or substrate 56, referred to as a skew measurement. Additionally, iMAT.TM. 62 can determine relative rotational orientation about the Z direction,

 

Bruker Improves N8 TITANOS Atomic Force Microscope for Metrology and Nanofabrication

Bruker's N8 TITANOS Atomic Force Microscope (AFM) is capable of inspecting large wafers, for metrology on solar panels, photolithography masks, flat panel displays, etc.

Bruker Nano (Aachen, Germany) reports its N8 TITANOS™ large-sample inspection AFM has been further improved to provide highest spatial resolving power. Due to its unique AFM technology and outstanding mechanical stability, the TITANOS has now been demonstrated with atomic-scale resolution on HOPG (highly oriented pyrolythic graphite) on a production instrument in standard configuration. The TITANOS has proven itself once again as the most precise and stable AFM platform for large samples up to 300 mm diameter.

The N8 TITANOS has been developed for the inspection of 300 mm wafers, and it is also in use for metrology on solar panels, photolithography masks, flat panel displays, etc. The TITANOS’ ultra-precise xy-positioning stage employs contact-less linear motors, high-resolution glass encoders and an air bearing for fast, reproducible sample movement. The TITANOS AFM is mounted on a solid granite bridge above the platform.

All AFM systems offered by Bruker Nano employ Fiber Optic Interferometry (FOI) detection as a unique feature to achieve outstanding resolution even on large samples. “FOI provides superior sensitivity as well as a calibrated deflection,” explains Dr. Hans Achim Fuss, Bruker Nano’s AFM Chief Technology Officer. “The results obtained with our AFMs are highly reproducible due to the exact knowledge of all crucial parameters.”

Dr. Frank Saurenbach, Vice President for AFM at Bruker Nano commented further: “It is incredible to see the TITANOS’ stage move hundreds of millimeters in seconds, and then operate with such stability and record resolution at each new measuring position. We are excited to supply the large sample AFM tool with the highest resolving power available on the market”.

The N8 TITANOS can be used as a stand-alone, automated system or combined with a high-performance optical microscope. It comes as a fully accessible R&D tool, or can be upgraded to an at-line production inspection system.

Buker Nano is a business unit of the Bruker AXS division. For more information about Bruker Nano and Bruker Corporation (NASDAQ: BRKR), please visit www.bruker.com

Bruker Nano Business Marketing Communications Manager Stefan Langner, +49 (30) 670990-802 stefan.langner@bruker-axs.de

Microscopic Snowman Made with Nanofabrication Tools

David Cox, a scientist in the Quantum Detection group at the National Physical Laboratory in the UK, built the world's tiniest snowman using nanofabrication techniques.  The NPL snowman is 10 microns across, 1/5th the width of a human hair. 

The snowman was made from two tin beads used to calibrate electron microscope astigmatism. The eyes and smile were milled using a focused ion beam, and the nose, which is under 1 µm wide (or 0.001 mm), is ion beam deposited platinum. A nanomanipulation system was used to assemble the parts 'by hand' and platinum deposition was used to weld all elements together. The snowman is mounted on a silicon cantilever from an atomic force microscope whose sharp tip 'feels' surfaces creating topographic surveys at almost atomic

The techniques used to create the Nano scale snowman are employed by NPL:

To make and fine tune Atomic Force Microscope cantilevers for measuring surface topography.

To manufacture nano scale SQUIDs (Superconducting Quantum Interference Devices) for a wide range of future metrological applications including spintronics, single particle detection, NEMS and quantum information processing.

To measure magnetic properties of very small magnetic systems using quantum hall probes.

A video of how the snowman was made is can be found at the NPL site and on YouTube at: http://www.youtube.com/watch?v=LmK8ec9MruM&feature=related