Technology

Q: Is a development step really not needed? 
A: Yes, you always see the pattern written in-situ line by line. And this also saves you a lot of turnover time to find out the right parameters when you start a new structure.

Q: What does closed-loop mean in your context? 
A: It means that (unlike other lithographic technologies) we measure the structures already during the patterning process and use the information to optimize parameters for writing the next line. Drifts can therefore be compensated in real-time resulting in a high reproducibility of about 1 nm in the Z-axis.

Q: Do you need any proximity corrections in the direct write approach of the NanoFrazor?
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: Can you write as fast as an e-beam?
A: Yes and no. At high resolution, our write speed is like that of an e-beam, which must 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: Why do you say you are faster than E-Beam?
A: With the in-situ inspection of the NanoFrazor, you can always see and inspect the patterned structures immediately. There is no development step necessary. With an e-beam on the other hand, it takes time until you have the structures which can be inspected by SEM. In this sense, the NanoFrazor is a tool for rapid prototyping.

Q: What’s your linear writing speed? 
A: Usually a few mm/s. A maximum speed of 20 mm/s was demonstrated in 2011 (2D mode).

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: Do you have any plan to further improve the patterning speed? 
A: Yes, the laser writing add-on is under development. The plan is to write features larger than 1 μm with laser writing, thereby increasing the patterning speed for large low-resolution patterns.

Q: What’s the tip lifetime? 
A: The advantage of our patterning process is that there is no mechanical force. So tips can last up to a few days, of course depending on the usage. Contamination can happen if the sample surface is contaminated with dust or other particles. For example, the 3×3 mm fractal pattern is written in one day and with one cantilever.

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: Can you write adjacent to fields? (And how do you guarantee a good stitching?) 
A: The NF explore has a coarse positioning stage with a range of 10 cm in XY and 2 cm in Z. The accurate stitching with sub-10nm accuracy between neighboring fields is performed using a surface roughness correlation function.

Q: Can you overlay nanostructures in several fabrication steps? What’s the accuracy of your overlay?

A: It’s very easy to overlay nanostructures in several fabrication steps due to the in-situ image function of the NanoFrazor. Better than 10 nm accuracy can be achieved as published here.

Resolution

Q: What’s the best resolution in X, Y, Z of the NanoFrazor? 
A: 8.7nm Half-Pitch lines in resist were demonstrate in 2013 and planes with 1.5 nm height difference were demonstrated in 2016. You can find many nice images of high resolution samples here.

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: What’s the best resolution you have transferred into Si? (What was the LER – line edge roughness?) 
A: The best was recently done by IBM with 13.5 nm half-pitch in silicon. LER was below 3 nm (3 σ). Both numbers are very good in lithography field. We don’t often see EBL showing similar results.

NanoFrazor Cantilevers

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: How high is the temperature at the tip? Can you adjust the temperature of the tip easily? 
A: The heater can be heated up to 1100 °C. The temperature is measured using the IV characteristics of doped Si. By changing the applied voltage, one can easily change the temperature.

NanoFrazor Resists

Q: Is resist development required?
A: No. This 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: Is the PPA commercially available?
A: Yes, you can order them online.

Q: What’s so special about your PPA? Does your technology work only with this polymer (and only on special substrates?) 
A: The key enabling feature of the PPA is that it unzips into smaller volatile molecules that evaporate completely when locally heated by the tip, leaving no pile-up or other traces elsewhere. Another complimentary possibility are molecular glass resists. Films consisting of such small molecules can also be made by evaporation. The choice in substrate is not limited.

Q: Can you do lift-off? 
A: High-resolution metal lift-off with 10 nm feature sizes has recently been demonstrated by IBM (see the publication here).

Q: Is PPA light sensitive? If so, which wavelength? 
A: The PPA reacts to UV light, but the time to expose PPA with UV light is very long.

Q: To coat Molecular Glass or PPA on substrate or wafer, what technology (spin coating or sputter) is being used? 
A: We are using spin coating for PPA. Molecular glasses have the advantage that they can also be evaporated. However, there are some other disadvantages and we usually work with PPA.

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.
  • Negative-tone resists
    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 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.

Applications

Q: What do your university customers do? 
A: You can read our customer statements here.

Q: Where can I learn more about your amazing technology? 
A: Attend presentations from us, IBM or our customers and check out our live demos at conferences. The list of upcoming events can be found here. You are also welcome to join our thermal probe workshop in March 2018. And perhaps visit our office in Zurich to see the NanoFrazor in action and discuss funding schemes with us.

Q: What are the (nano) applications that would benefit greatly from your 3D capabilities? 
A: We have identified several potential applications listed here. Our first customers have already begun performing their experiments. We support them and stay up-to-date with their progress which can be found in the publications and talks of the groups and on our website as well.

Q: Does the NanoFrazor fabricate same patterns as a Mask Aligner or EBL? 
A: Mask Aligner: Mask Aligners can’t achieve high resolution, but they are very suitable for large area micro patterns. NanoFrazor does not require a mask. EBL: The NanoFrazor can do all patterns a EBL can. EBL is sometimes more limited due to proximity corrections and development.

Q: Can the NanoFrazor be used in fixation and alignment of quantum dots in any device? (it could be CNT or any thin film based devices) 
A: The NanoFrazor can measure the topography of the sample surface. As soon as the CNT and quantum dots are detected, you can fabricate the second overlay structure aligned to the existing CNT and quantum dots very precisely.

Q: What are the applications (Nanofluidics or Microfluidics) in Molecular Biology or Protein Engineering?
A: There are quite some possibilities whenever 3D shaped surfaces are important for those applications. Also, some people used the hot tip to chemically modify the surface and subsequently attach biological molecules like DNA and proteins.

Q: Can I change something in the software? (Can I have access to the source code?) 
A: You are free to modify the software user interface (IGOR), including the scripting functionality. We consider our software as part of our IP, so there is no source code available for this part.

Company

Q: How many products do you have? 
A: We currently have two systems in the market. NanoFrazor Explore is for up to a 4-inch wafer sample and NanoFrazor Scholar is for up to a 30 cm x 30 cm sample. The performance of both systems are quite similar. For detailed information please contact us at info@swisslitho.com.

Q: Are you a spin-off from IBM Research? Does IBM have any stakes in the company? What’s their involvement? 
A: The technology was invented at IBM Research Zurich, but we’re NOT a spinoff as we were never a business unit of IBM. We are an independent legal entity from IBM and they don’t have any shares of SwissLitho. Our two founders have worked on the technology at IBM Research and we are in close collaboration with IBM in the framework of EU/CTI projects. There are several groups at IBM working on applications with the NanoFrazor.

Q: What’s the total manpower (IBM/SwissLitho combined) that currently goes into the development of thermal scanning probe lithography in the Zurich area?) 
A: More than 15.

Q: What about all the world records? Is this serious? (Is it really a 3D printer as mentioned in the press releases?) 
A: High-publicity is important for promoting our young and still widely unknown technology. The images chosen for the world records (“Pandas”, “famous mountains”) were tailored for a popular science audience. The execution of the experiments was done on IBM premises under supervision of the people from the Guinness book of records. And it’s not exactly a 3D printer, it’s “easy to use as a 3D printer”, so much for accuracy of reporters. Anyway, it’s amazing to pattern the world map on the space smaller than your hair in few minutes.

Markets

Q: What’s the unique selling point of the NanoFrazor?
A: The NanoFrazor Explore is much faster than any AFM-based lithography method. We aspire to become a viable alternative to e-beam lithography for rapid prototyping. The pillars of our technology are: 1) fast direct write, 2) in-situ inspection 3) 3D patterning and 4) no electron damage to sensitive samples 5) flexible pattern transfer possibilities. As USP one could state: “relatively low-(maintenance)-cost, easy-to-use, key-enabling, alternative beyond the capabilities of standard electron beam lithography.”

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.

Q: What does the “low cost” mean in your brochure? 
A: It’s low cost compared to the E-beam system with similar resolution. In the maintenance point of view, it’s low cost as well.

Q: What is the annual cost of consumables including tip and resist? 
A: Between 20k to 30k$ on the daily usage basis.

Sales

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. Please contact us to discuss further.

Q: Can I buy the NanoFrazor Explore or NanoFrazor Scholar in my country?
A: We sell directly in Europe and currently have distributors in the US, China, Japan, Korea, Singapore, Israel, India, Canada, Australia, Taiwan and South America. You can always contact us if you have any questions. Let’s stay in contact!

Q: I am very satisfied with my E-beam / FIB etc. Why do I need another alternative lithography technology? 
A: There are several features of the NanoFrazor that go beyond the capabilities of an E-beam or FIB like 3D direct writing, in-situ inspection, mark less overlay and no electron damage to electron sensitive devices like nanowires and graphene. You can find a comparison list here. If the E-beam is fully booked in your facility, the NanoFrazor can be an excellent choice to complement your nanofabrication options. You will get all the functionalities of an e-beam plus some extended fabrication capabilities.

Q: Is the NanoFrazor a proprietary system? 
A: The NanoFrazor is manufactured by SwissLitho in Switzerland and the technology is patented. The name belongs to SwissLitho. No other commercial thermal scanning probe lithography system exists.