Nanoimprint Lithography can be a cost-effective way for fast and accurate replication of nanostructures. Quality and high repeatability are key factors for the technique to be cost effective in the end. In-wafer and wafer-to-wafer variations of the imprinted nanostructures should be minimal while the stamp life should be as long as possible without compromising on quality.
SCIL uses an inorganic sol-gel based resist that is not susceptible to aging and shows low to no haze with only little shrinkage after curing. Furthermore the resist doesn’t require heating or UV light for curing which is very beneficial for quality and repeatability which allows for a superior overlay alignment accuracy. Because of the technique used in combination with the resist and stamp materials it is also possible to directly imprint functional materials without the need of transfer etching into a substrate.
SCIL Nanoimprint solutions not only provides machines and materials but provides a complete solution. With her own application lab and 2 high-volume production machines SCIL helps to optimize the processes from proof of concept up to pilot and high-volume production.
Nanoimprint lithography (NIL) is a technology that can deliver cost effective fabrication of patterns from 10’s of microns, down to sub-micron and nano-patterns (<10 nm) on large areas. Currently two application areas are of great interest for NIL. Accurate wafer scale overlay alignment and the reproducibility in replicating patterns with less than 1nm variation on their absolute size. This is important for nanophotonic applications such as augmented reality and metalenses. . In this contribution, we will show advanced overlay data on 200 and 300 mm wafers. A novel high contrast alignment marker set was developed and used to automatically inspect up to 70.000 cross-in-box overlay markers on a 300 mm wafer. The markers are designed to have a high contrast which enables a robust automatic pattern recognition and a ~100 nm measurement accuracy.A 200mm wafer with metalenses and blazed grating metasurface, designed at 532nm wavelength, is used to validate the sensitivity of scatterometry on the imprint mask. These metalenses are produced by imprinting a silica NanoGlass etch mask and subsequent ICP/RIE transfer etch in a niobium-pentoxide layer of 800 nm thickness.
Nanoimprint lithography (NIL) is a technology that can deliver cost effective fabrication of pattern from 10’s of microns, down to sub-micron and nano-patterns (<10nm) on large areas. Substrate Conformal Imprint Lithography (SCIL) solves the limitations of soft-stamp based NIL techniques (resolution, pattern deformation, overlay) and allows low-pressure wafer scale conformal contact and sub-10 nm resolution in direct patterned optically functional inorganic resist systems (RI up to 2.1).
Using a novel scatterometry method we verify the reproducible patterning of sub-micron gratings to +/- 1nm.
Our latest FabSCIL cluster offers processing of 200 and 300mm wafers, from 300 microns up to 2.5mm thickness, overlay accuracy below 1 micron, even with full automated overlay alignment of patterns directly from the front to the backside of the wafer. In the contribution we will elaborate on the material systems, reproducibility and production solutions.
Nano-photonic applications are on the brink of disrupting the optics we know. Examples are augmented reality glasses based on diffractive waveguide combiners (DWC) using surface relief gratings and meta-lenses consisting of high aspect ratio pillars. The challenge will be fabricating 100’s of millions of these large area devices with high yield and low cost. In this paper we will demonstrate the direct replication of nano-photonic patterns using a nanoimprint method in combination with inorganic functional optical resist materials. SCIL Nanoimprint solutions always developed the materials, processes and nanoimprint hardware as an integral system for optimal results. The same imprint technology scales from 100mm up to 300mm wafers. A unique approach of SCIL is to directly pattern inorganic materials with single-nm precision and keep this accuracy for over the full stamp lifetime. For nanophotonic applications the direct replication of nano-patterning in materials with a high refractive index (1.7 – 2.0) is highly desired. With this slow and expensive process steps such as optical- and hard mask layer deposition and reactive ion etching of these materials after the lithography step can be omitted. As another example augmented reality glasses with a high efficiency require 3 slanted gratings with varying orientations, resulting in 2 additional lithography and etching steps. We will show the direct nanoimprint patterning of slanted gratings in all orientations with a refractive index up to n=1.92 (@550nm). For these nano-photonic devices to work within specification, the absolute size of the patterns needs to be within 1-5nm variation and the refractive index to be controlled to the 3rd decimal (depending on the application). To verify the full nanoimprint production process in a close-coupled manner a fast non-destructive test method based on Fourier imaging scatterometry will be introduced. This method can determine the relevant sub-micron feature sizes with single nmprecision.
Many applications across photonics and semiconductor industries require the fabrication of nanostructures with non-trivial geometries with a precision and reproducibility down to the nanometer scale. Slanted gratings and metamaterials are examples of such designs that have vast applications in Augmented Reality and LiDAR. State-of-the-art lithography techniques, such as nanoimprint lithography or UV lithography, can provide such levels of fabrication precision for high-volume production. However, a rapid in-line quality inspection method for such complex patterns is required to monitor the fabrication process, verify the sample quality, and to ensure reproducibility. Here, we demonstrate a novel technique that allows us to inspect the quality of the samples in a non-destructive and fast manner, and to extract geometrical parameters of the nanostructures over large areas, generating spatial variations maps across wafers.
In optics, the surface determines the function. In classic optics you have material parameters, like refractive index, but the material shape / curvature (and roughness) determines the function. The advancement of nano-technology led to new methods to drastically lower fabrication costs per cm2 (compared to semicon approaches) and new insights in how electro-magnetic waves can be influenced at the fundamental level. That’s how nano-photonics was born. Nano-photonics allows us to control light with much more precision and functions than possible using conventional optics and enables new technologies such as diffractive waveguides and meta-lenses. The demands that these applications place on the patterns are not so easily met. The size and shape needs to be reproducible to an absolute size with variations less than 1 -2nm. Furthermore, the materials used need to have a high refractive index, preferably above n=2.0. The large area devices drive towards 300mm wafer processing to increase output and lower costs. To further decrease costs, directly patterning functional optical materials is needed to save 2 vacuum deposition steps and 3 vacuum dry-etch steps, both using expensive equipment. The industry is converging on nanoimprint lithography as a production technology that can address all these challenges. SCIL nanoimprint solutions is building on 20+ years material-, process- and tool building experience to provide customer specific high volume production solutions. Our approach has always been to start from the process and functional materials which allows us to optimize for stamp lifetime (500+), directly patterning fully inorganic functional materials (refractive index up to n=2.1), binary, blazed or slanted patterns with accuracy (less than 1nm absolute size variation). Our latest FabSCIL cluster tool offers processing of 200 and 300mm wafers, from 300 micron up to 2.5mm thickness, overlay lower than 1 micron even with alignment of patterns from the top to the bottom of the wafer. In the contribution we’ll elaborate on the material systems, reproducibility and production solutions.
Substrate Conformal Imprint Lithography (SCIL) solves the limitations of PDMS soft-stamp NIL techniques (resolution, pattern deformation, overlay) and allows low-pressure wafer scale conformal contact and sub-10 nm resolution using a novel silicone rubber stamp.
SCIL showed direct replication of sub-50nm patterns in silica over 200mm wafers with stamp lifetimes over 500 imprints, for AR, NIL resist with an index of up to n=1.96 and overcoat layers of up to n=2.1. Replication of slanted grating patterns in multiple orientations over the wafer are possible. First results of full 300mm wafer imprints will be shared.
Substrate Conformal Imprint Lithography (SCIL) solves the limitations of PDMS soft-stamp based NIL techniques (resolution, pattern deformation, overlay) and allows low-pressure wafer scale conformal contact and sub-10 nm resolution using a novel silicone rubber stamp. SCIL demonstrated direct replication of sub-50nm patterns in silica over 200mm wafers with stamp lifetimes over 500 imprints. The evaluation of patterns on wafer scale is usually done by SEM or AFM, and not amendable to inline inspection. We will demonstrate a novel compact optical quality inspection method for nanophotonic components, based on Fourier microscopy (imaging the back-focal plane of objective lens). In combination with inverse modeling, we reach few-nanometer precision for periodic structures.
Substrate Conformal Imprint Lithography (SCIL) solves the limitations of PDMS soft-stamp based NIL techniques (resolution, pattern deformation, overlay) and allows low-pressure wafer scale conformal contact and sub-10 nm resolution using a novel silicone rubber stamp.
SCIL demonstrated direct replication of sub-50nm patterns in silica over 200mm wafers with stamp lifetimes over 500 imprints. (Moxtek, NNT 2019) The evaluation of patterns on wafer scale is usually done by SEM or AFM, and not amendable to inline inspection. We will demonstrate a novel compact optical quality inspection method for nanophotonic components, based on Fourier microscopy (imaging the back-focal plane of objective lens). In combination with inverse modeling, we reach few-nanometer precision for periodic structures.
The Water Recovery X-Ray Rocket (WRXR) was a suborbital rocket payload that was launched and recovered in April 2018. The WRXR flew two technologies being developed for future large x-ray missions: x-ray reflection gratings and a hybrid CMOS detector (HCD). The large-format replicated gratings on the WRXR were measured in ground calibrations to have absolute single-order diffraction efficiency of ∼60 % , ∼50 % , and ∼35 % at CVI, OVII, and OVIII emission energies, respectively. The HCD was operated with ∼6 e − read noise and ∼88 eV energy resolution at 0.5 keV. The WRXR was also part of a two-payload campaign that successfully demonstrated NASA sounding rocket water recovery technology for science payloads. The primary instrument, a soft x-ray grating spectrometer, targeted diffuse emission from the Vela supernova remnant over a field-of-view >10 deg2. The flight data show that the detector was operational during flight and detected x-ray events from an on-board calibration source, but there was no definitive detection of x-ray events from Vela. Flight results are presented along with a discussion of factors that could have contributed to the null detection.
We will introduce SCIL as a full-wafer soft-stamp base nanoimprint technique with the advantages of being able to replicate sub-10nm features and perform micron accurate overlay alignment over 200mm wafers. The combination of PDMS based soft stamps and an inorganic crosslinking imprint resist leads to a very long stamp lifetime and the direct patterning of complex deep sub-micron patterns, such as slanted gratings with an index up to n=2.1. These complex patterns are of high interest for nano-photonic enabled applications such AR/VR and metasurfaces with applications such as “perfect” flat lenses. A new analytical model based on hyper-elastic deformation of silicon rubber nano-patterns was developed and is able to accurately predict pattern stability from sub-micron to less than 20nm patterns.
We will introduce SCIL as a full-wafer soft-stamp base nanoimprint technique with the advantages of being able to replicate sub-10nm features and perform overlay alignment with sub-micron precision over 200mm wafers. The combination of PDMS based soft stamps and an inorganic crosslinking imprint resist leads to a very long stamp lifetime of over 700 imprints, as demonstrated in the AutoSCIL 200 high volume production tool. Initial applications for wafer based NIL mainly required only a single, first mask, patterning step. For optical applications high refractive index material which can be directly patterned with high fidelity and low shrinkage are desired and initial results of inorganic resists that reach a refractive index of n=1.8 are demonstrated. As NIL and the applications develop, overlay alignment is the next step. Here we will discuss the developments ongoing to integrate wafer scale overlay alignment in the AutoSCIL production platform and which would achieve ~1 micrometer overlay alignment over 200mm wafers. Two applications that make use of the ability of NIL to replicate large area nano-patterns (X-ray mirrors) and the combination of micro- and sub-20nm patterns in one layer / pattern (cell proliferation templates) are discussed.
Nano-patterning materials and surfaces can add unique functionalities and properties which cannot be obtained in bulk or micro-structured materials. Examples range from hetro-epitaxy of semiconductor nano-wires to guiding cell expression and growth on medical implants. [1]
Due to the cost and throughput requirements conventional nano-patterning techniques such as deep UV lithography (cost and flat substrate demands) and electron-beam lithography (cost, throughput) are not an option. Self-assembly techniques are being considered for IC manufacturing, but require nano-sized guiding patterns, which have to be fabricated in any case.[2] Additionally, the self-assembly process is highly sensitive to the environment and layer thickness, which is difficult to control on non-flat surfaces such as PV silicon wafers or III/V substrates. Laser interference lithography can achieve wafer scale periodic patterns, but is limited by the throughput due to intensity of the laser at the pinhole and only regular patterns are possible where the pattern fill fraction cannot be chosen freely due to the interference condition.[3]
Nanoimprint lithography (NIL) is a promising technology for the cost effective fabrication of sub-micron and nano-patterns on large areas. The challenges for NIL are related to the technique being a contact method where a stamp which holds the patterns is required to be brought into intimate contact with the surface of the product. In NIL a strong distinction is made between the type of stamp used, either rigid or soft. Rigid stamps are made from patterned silicon, silica or plastic foils and are capable of sub-10nm resolution and wafer scale patterning. All these materials behave similar at the micro- to nm scale and require high pressures (5 – 50 Bar) to enable conformal contact to be made on wafer scales. Real world conditions such as substrate bow and particle contaminants complicate the use of rigid stamps for wafer scale areas, reducing stamp lifetime and yield.
Soft stamps, usually based on silicone rubber, behave fundamentally different compared to rigid stamps on the macro-, micro- and nanometer level. The main limitation of traditional silicones is that they are too soft to support sub-micron features against surface tension based stamp deformation and collapse [4] and handling a soft stamp to achieve accurate feature placement on wafer scales to allow overlay alignment with sub-100nm overlay accuracy.
Plasmonic nanostructures are known to influence the emission of near-by emitters. They can enhance the absorption and modify the external quantum efficiency of the coupled system. To evaluate the possibility of using plasmonics to enhance the light emission of a phosphor-converted LED device and create an efficient directional light source, regular arrays of aluminium nanoparticles covered with a red dye layer are investigated. In arrays of aluminum nanocylinders with a diameter of ca 140 nm combined with a thin (650 nm) layer of luminescent material, very narrow resonances have been observed, which lead to large enhancement factors of up to 70 and 20 for excitation with a directional blue laser source and a lambertian LED respectively, in a small spectral range for particular angles. The measured resonances agree very well with finite-difference time-domain numerical simulations. These changes in the angular emission profile of the red dye as well as the spectral shape of its emission can help to optimize the efficacy of phosphor-converted LED modules and increase the amount of useable light in a certain angular cone. Using Fourier microscopy, large modifications of the angular emission profile as well as spectral shaping are observed for these plasmonic LED devices if compared to reference samples without plasmonic nanostructures.
Substrate Conformal Imprint Lithography (SCIL™), developed within Philips Research, is a large area
replication technology, which allows flexible nano-imprinting, even around defects. It uses templates (stamps) with a
high modulus poly(dimethyl)siloxane (PDMS) pattern layer bonded onto a glass sheet with a low modulus PDMS
intermediary layer. This template sheet is attached to a grooved vacuum plate. By sequentially pressurizing and
evacuating the grooves, controlled contact with the resist layer and smooth release after resist curing can be established.
The PDMS stamps are cast from a nanostructured silicon wafer, which serves as the template master.
Charged Particle Nanopatterning (CHARPAN) techniques based on ion multi-beam projection techniques,
establish a promising route for generating such nanometer resolution template masters. 2D structures have been written
in the CHARPAN tool using Hydrogen (H3+) ions in a high resolution negative tone e-beam resist, Hydrogen
Silsesquioxane (HSQ). The CHARPAN tool can also be operated with heavier sputter ions (Ar+, Xe+ etc.) enabling
maskless and resistless 3D direct nanopatterning of a silicon template master.
CHARPAN generated 2D and 3D template masters, the PDMS stamps cast from these masters and the resulting
SCIL imprinted structures, show that at least a 20 nm resolution is feasible for this particular combination of
technologies. The combination of CHARPAN and SCIL opens up new possibilities for low cost, fast and flexible 2D and
3D manufacturing of nano-devices in several application fields, e.g. in life sciences related test structures and devices.
We have measured the angle and wavelength dependent transmission of index matched metal hole arrays, and
of arrays with a dielectric pillar in each hole. Index matching enhances the transmission, but also broadens the
resonances due to an enhanced coupling between plasmon and radiation modes. Hole arrays that are covered
with glass or have a glass pillar in each hole are created using an imprinting technique. We observe additional
waveguide modes in the transmission spectra of these arrays and discuss the avoided crossing that we observe
for the hybrid structure with dielectric pillars in the holes.
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