Quantum photolithography writes 1nm lines at industry speed
A team of researchers reveals that quantum optical lithography at a resolution down to 1nm half-pitch on a proprietary photoresist enables pattern transfer onto a silicon wafer. The research was led by Storex Technologies CEO Dr. Eugen Pavel, and published in Optics & Laser Technology.
Delivering a performance several times better than that described for any optical or Electron Beam Lithography (EBL) methods, Pavel emphasizes that the written patterns on the resist were successfully transferred to a silicon wafer at writing speeds comparable to current industry standards.
In 2012, the company had already demonstrated the direct writing of 2nm width lines through quantum optical lithography using special fluorescent photosensitive glass-ceramics to support quantum multi-photon confinement effects.
Since then, Storex Technologies has developed a proprietary photoresist material, the QMC-5, which also presents quantum multi-photon confinement effects. Spin coating a 5nm thick photoresist with such properties allows the pattern transfer to silicon through etching after the direct beam writing.
The experiment was carried out at room temperature and atmospheric pressure, using a commercial 650nm laser diode mounted on a specially-built optical pick-up stage. The piezo-controlled optical stage has a 0.6NA (Numerical Aperture) lens that controls the laser to deliver a Gaussian beam of 2µm focus diameter.
"In effect, with its multi-photon containment properties, the specially engineered photoresist material serves as a nanolens, enabling a very high resolution at the centre of the beam", explained Pavel when interviewed by EE Times Europe.
According to the paper, the quantum optical lithography taking place in the special resist involves a cooperative interaction of many photons. A three-photon process in absorption phase and a 540 photons process as suggested by quantum lithography theory for the writing phase.
This is a real breakthrough as quantum optical lithography puts aside the diffraction limits encountered by traditional optical lithography using masks.
Next on Dr Pavel's agenda is to determine accurately the resolution at which quantum optical lithography could be pushed at 650nm. "It is a difficult metrological problem to solve, but we would like to find out what the resolution limit we could reach with this approach. Is it in the 5 angstrom or in the 1 angstrom range?" he said. That would be pushing lithography to 0.5 or even 0.1nm, at atomic level. Finding an industrial partner is another matter, so disruptive is this technology.
So what are the limiting factors for the adoption of quantum optical lithography by the industry?
"Since we have the right resist and we operate at the same writing speed as the industry, I believe that the only limiting factors are psychological," said Pavel.
A lot of money has been invested in developing Electron Beam Lithography and also in Extreme UV lithography, and on that basis alone, it is certainly difficult for big players to accept such a fresh technology.
Yet, according to Pavel, the costs of implementing quantum optical lithography would be hundreds of times less than traditional optical lithography, and thousands of times less than EBL or EUV lithography which require vacuum and very complex lens systems. "That is because all these equipment require complex and costly optics. We get away with much simpler optics, and our process is done at atmospheric pressure. We could even implement multiple laser beams for parallel processing," clarifies Pavel.
- Julien Happich