Q: Can you write as fast as an e-beam?
A: Yes and no. At high resolution, our write speed is similar to that of an e-beam, which has to use high-dose resists like HSQ. E-beam can be faster for low resolutions, if a chemically amplified resist is allowed. In any case, overall production time can be shortened by the NanoFrazor, as resist development and quality inspection is already integrated in the writing process.
Q: How long does it take to write 1 mm2 with the NanoFrazor Explore?
A: The NanoFrazor process is around 1000x faster than common AFM lithography techniques like anodic oxidation or dip pen lithography, because a single pixel can be written in microseconds instead of milliseconds. Depending on the pixel size and the number of lines to write, it can still take a few hours to write 1 mm2.
Q: What are the fundamental limitations for the speed?
A: The maximum speed is determined by the minimal reaction time at tip/sample contact (around 1 µs for PPA) and the maximum controllable vertical frequency of the cantilever (500 kHz demonstrated).
Q: What’s the smallest feature size you can write?
A: So far, the best resolution which has been demonstrated was 8 nm lines and spaces.
Q: What are the fundamental limitations for the resolution?
A: The minimal feature size is determined by the tip radius, the molecular size and mechanical stability of the resist.
Q: Are your cantilevers/tips consumables?
A: Yes. They are easy to replace and can be interchanged in less than a minute.
Q: What’s the tip lifetime?
A: Tips can last up to a few days, depending on usage scenario and the required resolution. The tips durability is affected by hard sample materials or contamination from either impure resists or the environment.
Q: Is resist development required?
A: No. This actually saves a lot of turnover time to discover and fine-tune the right parameters for rapid prototyping.
Q: Will there be any remnants of the polyphthalaldehyde (PPA)?
A: No. The PPA fully decomposes into small monomers which evaporate.
Q: Are there any alternatives to PPA?
A: There are a few possibilities:
Molecular resists: Completely dry process using PVD
There are several positive-tone resists that can be prepared by physical vapor deposition (PVD) instead of spin coating and have been successfully tested for the NanoFrazor process. PVD has the advantage that no solvent is ever in contact with the substrate. Furthermore, very clean films can be deposited on any pre-structured substrates. Such resists are usually based on molecular glasses where small organic molecules form an amorphous film. SwissLitho is testing such molecular resists in collaboration with the University of Bayreuth in Germany within the framework of the EU Project: Single Nanometer Manufacturing.
Heat-induced cross-linking of resists has been demonstrated using thermal cantilevers, making these materials potentially feasible negative-tone resist for patterning. However, there has been very little effort made in this direction as there are doubts if the achievable patterning quality and reliability are sufficient for high-resolution nanolithography. Given the current status of negative-tone resists, we recommend the use of lift-off to create an inverted etch mask from the positive-tone PPA pattern.
Alternative polymer resists
Some conventional polymer-based resists can be patterned with the NanoFrazor. However, most polymers would not be decomposed and evaporated by the hot tip, but softened and plastically deformed which drastically limits the patterning possibilities. There are some other polymers that show a similar unzipping reaction as PPA and a few have been tested, successfully decomposed and evaporated with the NanoFrazor. So far, none of them showed the same capabilities for lithography as PPA.
Without resist: Thermochemical Patterning
A heated probe tip can create the desired local surface properties in many materials, which is exploited for functionalization in Thermochemical Scanning Probe Lithography. Some examples of tc-SPL are summarized here.
Q: What wafer sizes can the NanoFrazor Explore handle?
A: The NanoFrazor Explore typically writes on small samples (about 20 mm × 20 mm). Larger workpieces of up to 4″-wafers are also possible, but at a slightly reduced scanner performance. The tip can reach any location within a 100 mm x 100 mm area.
Q: How big is the write field of the NanoFrazor Explore?
A: The NanoFrazor Explore has a piezo scanner with a scan range of 75 μm x 75 μm.
Q: Do you need a vacuum or a clean-room for the NanoFrazor Explore?
A: No vacuum or even a clean-room is required to create high-resolution 3D structures.
Q: Do you need any proximity corrections in the direct write approach of the NanoFrazor Explore?
A: No. Unlike beam based technologies, there is no exposure of the resist. The resist material is physically removed, and no proximity correction is needed.
Q: What’s the unique selling point of the NanoFrazor Explore?
A: The NanoFrazor Exploreis much faster than any AFM-based lithography method. We aspire to become a viable alternative to e-beam lithography for rapid prototyping.
Q: What is your target market?
A: The NanoFrazor Explore is targeted towards university customers and research centers for rapid prototyping. Small series and custom products, stamps, masks and molds are further target markets.
Q: What’s your technology roadmap?
A: We are currently engaged in several R&D projects with external partners for advancing the technology with several more collaborations planned for the future.
Q: How do factor throughput considerations in your product roadmap?
To write 1 cm2 with 10 nm resolution, 1012 pixels (1 TPixel) are needed. At a write speed of 1 MPixel/s at 10 mm/s scan speed, the writing time would be 106 seconds (11.6 days), neglecting overhead (e.g. positioning, calibration, turnaround). As a single-tip system, the NanoFrazor Explore is only suited for the fabrication of small area, high-resolution templates. Massive parallelization as for the NanoFrazor Industrial will overcome its throughput limitation.
Q: Can I buy just the thermal cantilevers? Will they fit into a standard AFM?
A: No. Also, they are not compatible with standard AFMs.
Q: Is it possible to get a test sample?
A: We are more than happy to demonstrate our capabilities with customized samples.
Q: Can I buy the NanoFrazor Explore in my country?
A: We currently have distributors in the US, China, Japan, Korea, Israel, Dubai, Brazil, Taiwan, India and Australia. Please contact us directly if you are from another country.