The New Lithography System with 0.768nm Resolution

Zyvex Labs has announced the launch of Zyvex Litho 1, a sub-nanometer resolution lithography system that is claimed to achieve a resolution of 0.768nm, which is about the width of two silicon atoms.

And this lithography system does not use the current mainstream EUV technology. Zyvex Litho 1 is based on STM (scanning tunneling microscope) and EBL (electron beam lithography) technology. What's even more exciting is that this product doesn't just exist in the experimental stage, as Zyvex Labs says it is already taking orders for the Zyvex Litho 1 system, with a lead time of about six months. The current ASML ArF lithography delivery cycle has come to 24 months. EUV lithography also takes about 18 months.

How to achieve 0.768nm resolution?

From the Zyvex Labs website, we know that Zyvex Labs was founded in 1997 to develop and commercialize atomic-level precision manufacturing (APM) technology to manufacture products with atomic-level precision. APM technology can be utilized to manufacture a variety of products, including design materials, supercomputers to, advanced medical devices, and more.

The company's founder, Jim Von Ehr, first worked at TI as manager of the design automation division. The team developed three generations of CAD tools for IC layout over 11 years.

Notably, Zyvex Litho 1 is supported by the U.S. Department of Defense Advanced Research Projects Agency, the Army Research Office, the Department of Energy's Office of Advanced Manufacturing, and Professor Reza Moheimani of the University of Texas at Dallas for his work "supporting the development of controls for single-atom scale quantum silicon Professor Reza Moheimani was also recently awarded the Industrial Achievement Award by the International Federation of Automation Control for his research on "Control Development to Support Single-Atomic Scale Quantum Silicon Device Manufacturing.

Zyvex Litho 1 system

As mentioned earlier, Zyvex Litho 1 uses STM-based electron beam lithography, which works by exploiting the "quantum tunneling effect," which means that electrons will pass through an insulator (air) on the other side of a conductor if they are close enough to the conductor, even though there is a layer of insulator (air) between the electrons and the conductor. This is called "quantum tunneling" because it is like a "tunnel" through the insulator.

The STM uses a probe with a tip the size of an atom and applies a voltage between the probe and the sample under test, and keeps reducing the distance between the probe and the sample so that when the distance is small enough, a very small current is generated in the circuit. The current size is related to the distance between the probe and the sample, so we can use the current size to invert the distance between the probe and the sample to "feel" the surface undulation of the sample and finally get the microscopic image of the sample.

The role of STM is to observe the microscopic world, but with STM, you can do the work of manipulating atoms.

Traditional electron beam lithography requires large electron optical systems and energies of up to 200 Kev to achieve small spot sizes. The high-energy electrons needed to obtain small spot sizes at the same time are dispersed in the polymer resist used in traditional electron beam lithography and disperse the deposited energy, producing a larger structure.

Zyvex Labs' STM-based electron-beam lithography employs hydrogen depassivation lithography (HDL). As described by Prof. Reza Moheimani's team in a research paper published last year, HDL involves first attaching a layer of hydrogen atoms to the surface of a flat silicon substrate to prevent other atoms or molecules from being absorbed into the surface while acting as a very thin resist layer; then a probe is placed on top of the hydrogen atoms, a high-frequency signal is added to the probe sample bias voltage, and the high-frequency signal is increased in amplitude until the hydrogen atoms are removed from the surface, exposing the silicon beneath; after a predetermined number of hydrogen atoms are selectively removed from the surface, phosphine gas is introduced into the environment and, after a specific process, phosphorus atoms are adsorbed onto the surface, each acting as a quantum site element.

Zyvex Labs says that with HDL, it is possible to expose individual atoms that are more than 10 times smaller than the 10% threshold radius for electron beam lithography. And HDL does not even require the use of optics but simply places the tungsten tip about 1 nm above the hydrogen-passivated silicon sample.

However, as shown above, it is unlikely that the electrons will move only along the solid arrow path required to expose a single hydrogen atom, so it is thought that the exposure region is difficult to narrow without the optics in focus. The electrons are not emitted from the tip (in imaging and atomic precision lithography modes) but rather tunnel from the sample to the tip (in imaging mode) or from the tip to the sample (in lithography mode).

By calculating the normalized current distribution and the normalized exposure efficiency due to the quantum tunneling effect, the radial distance from the peak as a function of the hydrogen atom per electron desorbed eventually led to a common pattern of Zyvex Litho 1 exposure patterns with HDL to a lateral distance of about 0.47 nm without exposure, resulting in an error rate of 10-6.

Of course, as a complete system, Zyvex Litho 1 includes a UHV system for STM lithography, precursor gas metrology and Si MBE, digital vector lithography, automation, and scripting. Zyvox labs say that a 7.7nm (10 pixels) square exposure is impossible without sub-nanometer resolution and precision.

For manufacturing quantum processors, but difficult to mass-produce

Zyvex Litho 1 is completely different from the current large-scale chip manufacturing methods. Current large-scale chip fabrication methods require photomask plates to precisely position and project the chip's functional graphics onto the wafer for selective exposure of the photoresist coating.

And the use of electron beam lithography, there have been several laboratories that have previously successfully resolved about 1nm. In 2017, the U.S. Department of Energy under the Brookhaven National Laboratory announced the successful use of the electron beam lithography process to create a resolution of 2nm; Lawrence Berkeley National Laboratory also announced in 2016 the use of carbon nanotubes and molybdenum disulfide and other materials to achieve 1nm process.

However, this technology has long lithography times and low yields and is difficult to put into large-scale applications. Similarly, Zyvex Litho 1's STM-based electron beam lithography suffers from these problems, such as its displacement time of 200 seconds for a distance of 500 nm. So what fields is it suitable for?

Zyvex Labs says that quantized energy levels and quantum tunneling transport are extremely sensitive to the size of individual atomic layers or even individual atoms, and their technology is an order of magnitude more accurate than the best commercially available electron beam lithography, so Zyvex Litho 1 will be most useful in quantum technology.

Final words

Although it is not the first time that 1 nm resolution lithography has been achieved in the lab, the commercialization of lithography equipment accurate to the atomic scale is a milestone for Zyvex Litho 1. As the old saying goes, "If you want to do a good job, you must first improve your tools," and having tools with higher precision may lead to more future innovations in the semiconductor field.

Previous: Microwave oven transformer working principle and common troubleshooting

Next: M-LVDS Optimizes High-Density Systems for Compact Modular Design