Wafer-level nanoimprint lithography (NIL) has increasingly become a key enabling technology to support new devices and applications across a wide range of markets. Leading manufacturers of augmented reality (AR) devices, optical sensors and biomedical chips are already utilizing NIL and realizing the benefits of this technology, including the ability to mass manufacture micro- and nano-scale structures down with a maximum degree of freedom for the device dimensions. Another key advantage of this replication based technology is, given by the fact that even complex structures which require precise and time consuming fabrication methods can be transferred to mass manufacturing in an efficient semiconductor manufacturing line. Additionally, for many devices especially for optical applications the replicated layer can be directly used as functional layer in the product. Today NIL is considered as decisive process step for a number of emerging products, including AR waveguides. With increasing volumes the scaling of the production lines is crucial for most economical implementation of NIL. In particular for scaling to production lines using 200mm or even 300mm wafer sizes, the whole process chain has to be established. This is in particular a focus for AR devices requiring highly complex structures with tight specifications. Thus best efforts for master fabrication are crucial to obtain best performing devices. For smaller substrates, typically full area masters are used to manufactured and used for the NIL process. However, as the masters are mainly fabricated by sequential processes the costs scale with the pattern area. For 200mm and 300mm it has been proven to be viable option to start with single high-quality devices and scale them by step and repeat (SR) NIL to fully populated waferscale masters and subsequently to use those for volume manufacturing on wafer-level. The wafer-level production itself requires then reliable replication of working stamps and wafer level nanoimprinting of these multiple devices on a single wafer. As a result it is key for the high volume manufacturing to have a thorough understanding of all required pattering and replications steps to enable these large area manufacturing lines.
As the designs of future mask nodes become more and more complex the corresponding pattern writing times will rise
significantly when using single beam writing tools. Projection
multi-beam lithography [1] is one promising technology to
enhance the throughput compared to state of the art VSB pattern generators.
One key component of the projection multi-beam tool is an Aperture Plate System (APS) to form and switch thousands
of individual beamlets. In our present setup a highly parallel beam is divided into 43,008 individual beamlets by a Siaperture-
plate. These micrometer sized beams pass through larger openings in a blanking-plate and are individually
switched on and off by applying a voltage to blanking-electrodes which are placed around the blanking-plate openings. A
charged particle 200x reduction optics demagnifies the beamlet array to the substrate. The switched off beams are
filtered out in the projection optics so that only the beams which are unaffected by the blanking-plate are projected to the
substrate with 200x reduction.
The blanking-plate is basically a CMOS device for handling the writing data. In our work the blanking-electrodes are
fabricated using CMOS compatible add on processes like SiO2-etching or metal deposition and structuring. A new
approach is the implementation of buried tungsten electrodes for beam blanking.
A detailed evaluation study has been performed with respect to the suitability of projection electron and ion multi-beam
lithography for the fabrication of leading-edge complex masks. The study includes recent results as obtained with
electron and ion multi-beam proof-of-concept systems with 200x reduction projection optics where patterns are
generated on substrates using a programmable aperture plate system (APS) with integrated CMOS electronics,
generating several thousands of well defined beams in parallel. A comparison of electron and ion projection multi-beam
writing is provided, in particular with respect to the suitability to expose non-chemically amplified resist (non-CAR)
materials. The extendibility of projection multi-beam technologies for 16nm hp, 11nm hp and 8nm hp mask nodes is
discussed as well as for wafer direct write for 22nm hp and below.
Multi-beam lithography is considered a promising fabrication technology for future node mask making. Due to rising
design complexity and therefore increasing pattern writing times the multi-beam approach has distinguished throughput
advantages compared to state of the art variable shaped beam pattern generators.
A key component of a projection multi-beam writing tool is the programmable blanking-plate for generating the desired
pattern geometry on the mask substrate.
In our case a highly parallel charged particle beam illuminates a Si aperture-plate which shapes and generates many
thousand individual spot beams. These beams pass through a blanking-plate with integrated CMOS electronics for demultiplexing
the writing data. The blanking-plate is equipped with blanking and ground electrodes placed around the
apertures switching the beams "on" or "off", dependent on the desired pattern. The beam array is demagnified by a 200x
reduction optics and the exposure of the mask substrate is done in stripes by a continuous moving stage [1,2].
Cross talk between adjacent beams in the blanking-plate has to be avoided to ensure adequate pattern fidelity and line
edge roughness on the mask substrate. One solution is the insertion of a 3D Si aperture-plate in proximity to the
blanking- plate shielding the blanking electrodes from each other during operation.
We developed and characterized a new process flow for the fabrication of these 3D Si aperture-plates for the case of 43
thousand beams in parallel and will present and discuss the cross talk results for blanking-plates combined with standard
2D and new 3D Si aperture-plates.
Two main challenges of future mask making are the decreasing throughput of the pattern generators and the insufficient
line edge roughness of the resist structures. The increasing design complexity with smaller feature sizes combined with
additional pattern elements of the Optical Proximity Correction generates huge data volumes which reduce
correspondingly the throughput of conventional single e-beam pattern generators. On the other hand the achievable line
edge roughness when using sensitive chemically amplified resists does not fulfill the future requirements. The
application of less sensitive resists may provide an improved roughness, however on account of throughput, as well. To
overcome this challenge a proton multi-beam pattern generator is developed [1]. Starting with a highly parallel broad
beam, an aperture-plate is used to generate thousands of separate spot beams. These beams pass through a blanking-plate
unit, based on a CMOS device for de-multiplexing the writing data and equipped with electrodes placed around the
apertures switching the beams "on" or "off", dependent on the desired pattern. The beam array is demagnified by a 200x
reduction optics and the exposure of the entire substrate is done by a continuous moving stage.
One major challenge is the fabrication of the required high aspect deflection electrodes and their connection to the
CMOS device. One approach is to combine a post-processed CMOS chip with a MEMS component containing the
deflection electrodes and to realize the electrical connection of both by vertical integration techniques. For the evaluation
and assessment of this considered scheme and fabrication technique, a proof-of-concept deflection unit has been realized
and tested. Our design is based on the generation of the deflection electrodes in a silicon membrane by etching trenches
and oxide filling afterwards. In a 5mm x 5mm area 43,000 apertures with the corresponding electrodes have been
structured and wired individually or in groups with aluminum lines. The aperture-plate for shaping the beams has been
aligned and mounted on top of the blanking-plate. Afterwards this sandwich has been fixed on a base-plate with a pin
plug as interface. The electrical connection has been performed with a standard chip bonding process to the aluminum
pads on the blanking-plate. Finally, the proof-of-concept deflection unit was evaluated in a test bench. The results of
electrical- and exposure tests are presented and discussed in detail.
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