As the semiconductor industry continues to strive towards high volume manufacturing for EUV, flatness specifications for photomasks have decreased to below 10nm for 2018 production, however the current champion masks being produced report P-V flatness values of roughly ~50nm. Write compensation presents the promising opportunity to mitigate pattern placement errors through the use of geometrically adjusted target patterns which counteract the reticle’s flatness induced distortions and address the differences in chucking mechanisms between e-beam write and electrostatic clamping during scan. Compensation relies on high accuracy flatness data which provides the critical topographical components of the reticle to the write tool. Any errors included in the flatness data file are translated to the pattern during the write process, which has now driven flatness measurement tools to target a 6σ reproducibility <1nm. Using data collected from a 2011 Sematech study on the Alpha Demo Tool, the proposed methodology for write compensation is validated against printed wafer results.
Topographic features which lack compensation capability must then be held to stringent specifications in order to limit their contributions to the final image placement error (IPE) at wafer. By understanding the capabilities and limitations of write compensation, it is then possible to shift flatness requirements towards the “non-correctable” portion of the reticle’s profile, potentially relieving polishers from having to adhere to the current single digit flatness specifications.
Due to the impact on image placement and overlay errors inherent in all reflective lithography systems, EUV reticles
will need to adhere to flatness specifications below 10nm for 2018 production. These single value metrics are near
impossible to meet using current tooling infrastructure (current state of the art reticles report P-V flatness ~60nm). In
order to focus innovation on areas which lack capability for flatness compensation or correction, this paper redefines
flatness metrics as being “correctable” vs. “non-correctable” based on the surface topography’s contributions to the final
IP budget at wafer, as well as whether data driven corrections (write compensation or at scanner) are available for the
reticle’s specific shape.
To better understand and define the limitations of write compensation and scanner corrections, an error budget for
processes contributing to these two methods is presented. Photomask flatness measurement tools are now targeting 6σ
reproducibility <1nm (previous 3σ reproducibility ~3nm) in order to drive down error contributions and provide more
accurate data for correction techniques. Taking advantage of the high order measurement capabilities of improved
metrology tooling, as well as computational capabilities which enable fast measurements and analysis of sophisticated
shapes, we propose a methodology for the industry to create functional tolerances focused on the flatness errors that are
not correctable with compensation.
We describe a distance-measuring interferometer based on a novel frequency-stepping laser that is tunable
over 30 nm. Conventional tunable lasers provide continuous tuning over a range of wavelengths without any
mode transitions. The new frequency-stepping laser was designed to maximize frequency repeatability by
exploiting the mode-hopping behavior to achieve equal frequency increments. An interferometric image is
collected at consecutive laser mode frequencies making it very easy to perform Fourier transforms. The
modulation frequency of the interference on each pixel is directly proportional to the optical path difference
between the reference and test arms of the interferometer as well as the laser mode spacing. The inherent
stability of the frequency-stepping laser results in a very accurate conversion from the modulation frequency
of the pixel to its OPD. A Fourier transform is performed on each pixel to determine the height difference
between the reference and measurement arms independent of its neighboring pixels.
Our laser mode spacing of 36 GHz results in an unambiguous measurement range of 2.1 mm. Prior
knowledge about the features of the part being measured allows us to measure over 300 mm of range with 10
nm resolution. This can be combined with conventional PMI techniques to achieve sub-nanometer resolution.
This technique is applicable to both rough and smooth parts making it possible to perform metrology on
individual components as well as partial assemblies that require tight tolerances.
We have developed a novel class of projection lithography systems that provide both high-throughput resist patterning and dielectric via formation for production of a variety of electronic modules, including optoelectronic waveguides, flat-panel displays, multichip modules, printed circuit boards, and microelectromechanical systems. The new technology eliminates limitations of current lithography tools, including contact and proximity tools, conventional projection systems, steppers and scanners, and direct-write machines. Further, the new system concept is highly modular, thereby providing equipment upgradability as well as choice of user-specified system configurations. These results are achieved with a novel, hexagonal seamless scanning concept and a single-planar stage system configuration that provide both high optical and scanning efficiencies, and combine high-resolution imaging with very large exposure area capability. We describe the new technology and present experimental results. These lithography systems are highly attractive for cost-effective production of microelectronic devices with feature sizes ranging from 15 micrometers to below 1 micrometers and substrate sizes ranging from 150 X 150 mm to larger than 610 X 660 mm.
We have developed a novel class of projection lithography system that provide both high-throughput resist patterning and dielectric via formation for production of a variety of electronic modules, including flat-panel displays, multichip modules, printed circuit boards, and microelectromechanical systems. The new technology eliminates limitations of current lithography tools, including contact and proximity tools, conventional projection systems, steppers and scanners, and direct-write machines. Further, the new system concept is highly modular, thereby providing equipment upgradability as well as choice of user-specified system configurations. These results are achieved with a novel, hexagonal seamless scanning concept and a single-planar stage system configuration that provide both high optical and scanning efficiencies, and combine high-resolution imaging with very large exposure area capability. We describe the new technology and present experimental results. These lithography systems are highly attractive for cost-effective production of microelectronic products with feature sizes ranging from 15 micrometers to below 1 micrometers and substrate sizes ranging from 150 X 150 mm to larger than 610 X 660 mm.
We describe a novel lithography system that is capable of high-throughput projection imaging on continuous, flexible substrates in a roll-to-roll configuration. The system provides both large-area, high-resolution patterning in photoresists and via formation by photo-ablation in dielectrics, eliminating limitations of lithography tools currently used in the production of flexible circuits. The unique, modular design of the new system also provides equipment upgradability as well as choice of user-specified system configurations. These results are achieved with the combination of three key novel system features: a hexagonal seamless scanning projection imaging technology, a single- planar stage system configuration, and a roll-to-roll substrate handling system. These features provide high optical and scanning efficiencies as well as low overhead times, enabling processing throughputs as high as 4 sq. ft./min. In this paper, we describe the new lithography system concept; present the detailed system design of a recently completed machine; and discuss the key hardware subsystems, both optical and mechanical. This lithography system is highly attractive for cost-effective production of a wide variety of microelectronic products on flexible substrates, including printed circuits, multichip modules, and displays.
Anvik Corporation has developed a class of novel projection systems that provide both high-throughput resist patterning and dielectric photoetching for production of a variety of electronic modules including flat panel displays, multichip modules, microelectromechanical systems, and printed circuit boards. This new technology eliminates the limitations of current lithography tools, including contact and proximity tools, conventional projection systems, steppers and scanners, and direct-write machines. Further, the Anvik system is highly modular, thereby providing equipment upgradability as well as choice of user-specified system configurations. These results are achieved with a novel seamless scanning concept and stage system configurations that provide both high optical and scanning efficiencies, and enable incorporation of a high-speed automatic part loader and an automatic alignment system. We describe the new technology and present results which demonstrate 3 micron resolution in commercial photoresists.
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