Nano-lithography

Nanolithography : Introduction to nanolithography head points:
Optical lithography
Optical laser nanolithography
Multiphoton lithography

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Preeti Choudhary

1. Nano-Lithography Presented by: Preeti Choudhary M.Sc. (Applied Physics)

2. Introduction to nano-lithography

3. Optical lithography Main article:  Photolithography Optical lithography, which has been the predominant patterning technique since the advent of the semiconductor age, is capable of producing sub-100-nm patterns with the use of very short optical  wavelengths . Several optical lithography techniques require the use of  liquid immersion  and a host of  resolution enhancement  technologies like  phase-shift masks (PSM) and  optical proximity correction  (OPC).  Multiple patterning  is a method of increasing the resolution by printing features in between pre-printed features on the same layer by  etching  or creating sidewall spacers, and has been used in commercial production of  microprocessors  since the 32 nm process node e.g. by  directed self-assembly  (DSA).  Extreme ultraviolet lithography  (EUVL) uses ultrashort wavelengths (13.5 nm) and as of 2015, is the most popularly considered Next-generation lithography ( NGL ) technique for mass-fabrication. Ref:  "ASML: Press - Press Releases - ASML reaches agreement for delivery of minimum of 15 EUV lithography systems" . www.asml.com. Retrieved 2015-05-11.

4. Optical laser nanolithography Optical lithography is referred to as a method for replicating patterns used to create IC configuration on a photoresist layer sensitive to radiation exposure and coated over a silicon or other semiconductor wafer. Lithography includes imprinting the circuit pattern (template), photoresist technology, and mask making. There are a few variants of realizing optical lithography (Fig. ): contact or shadow printing (a), shadow printing with a gap (b), and projection printing (c). optical lithography made use of visible (l ˆ 436 nm) and UV (l ˆ 365 nm) light emitted by a mercury vapor lamp. Nanolithography  is the branch of  nanotechnology  concerned with the study and application of fabricating  nanometer -scale  structures, meaning patterns with at least one lateral dimension between 1 and 1,000 nm. Different approaches can be categorized in serial or parallel, mask or  maskless /direct-write,  top-down  or bottom-up,  beam  or  tip-based , resist-based or resist-less methods.

5. Applications of nanolithography include among others:  Multigate devices  such as  Field effect transistors  (FET),  Quantum dots ,  Nanowires ,  Gratings ,  Zone plates  and  Photomasks , nanoelectromechanical systems ( NEMS ), or  semiconductor   integrated circuits  ( nanocircuitry ).

6. Electron-beam lithography Main article:  Electron beam lithography Electron beam lithography (EBL) or electron-beam direct-write lithography (EBDW) scans a focused beam of  electrons  on a surface covered with an electron-sensitive film or  resist (e.g.  PMMA  or  HSQ ) to draw custom shapes. By changing the  solubility  of the resist and subsequent selective removal of material by immersion in a solvent, sub-10 nm resolutions have been achieved. This form of direct-write, maskless lithography has high resolution and low throughput, limiting single-column e-beams to  photomask  fabrication, low-volume production of  semiconductor devices , and research&development .  Multiple-electron beam approaches  have as a goal an increase of throughput for semiconductor mass-production. EBL can be utilized for selective protein nanopatterning on a solid substrate, aimed for ultrasensitive sensing .

7. Nanoimprint lithography Main article:  Nanoimprint lithography Nanoimprint lithography  (NIL), and its variants, such as Step-and-Flash Imprint Lithography, LISA and LADI are promising nanopattern replication technologies where patterns are created by mechanical deformation of imprint resist, typically a  monomer  or polymer formulation that is  cured  by heat or  UV  light during imprinting. This technique can be combined with  contact printing  and  cold welding .

8. Multiphoton lithography Multiphoton lithography  (also known as  direct laser lithography  or  direct laser writing ) patterns surfaces without the use of a  photomask , whereby  two-photon absorption  is utilized to induce a change in the  solubility  of the resist. Scanning probe lithography Scanning probe lithography  (SPL) is a tool for patterning at the nanometer -scale down to individual atoms using  scanning probes .  Dip-pen nanolithography  is an additive, diffusive method,  thermochemical nanolithography  triggers chemical reactions,  thermal scanning probe lithography  creates 3D surfaces from polymers, and  local oxidation nanolithography employs a local oxidation reaction for patterning purposes

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