Nanoimprinting Regular Nanostructures Of P(VDF-TrFE)with ETFE Mold

Thermal nanoimprinting is a high-throughput method for the fabrication of large-area regular arrays,and can reach the resolution down to 10 nm.It can also be used to control physical properties,orientation and crystal structure of the polymers.The crucial element of NIL is the mold fabrication.It is usually a complex process especially when template is fabricated on a stiff material such as silicon,silicon dioxide(quartz)or nickel.Small features on that material can be obtained by thoroughgoing nanofabrication methods(optical lithography,EBL,etching,electrodeposition),which require large infrastructure and increase the cost of production.Moreover,inorganic molds present a number of problems because of their physical properties(high adhesion,difficult demolding,thermal expansion,etc.)limiting their efficiency in imprint process.An economical and reliable replication method is required as an alternative for silicon and other inorganic materials.In order to provide a viable alternative to traditional inorganic materials and to achieve high-resolution NIL comparable with all modern processes,the polymer mold should own the good conformal contact and none deformation or collapse of high resolution pattern.Therefore a necessary pressure is required to counter the rigidity of the mold and to ensure a conformal contact with the resist.However,as pressure increases,distortion and stamp fracture increases as well.Using a tough material can resolve this problem and prevents brittle failure.Therefore,a balance between stiffness and flexibility,softness and toughness is crucial for conformal contact and prevention of deformation of the mold for high resolution nanostructures.Recently poly(vinylidene fluoride-trifluoroethylene),or P(VDF-TrFE),increased scientific and technologic interest,due to its an excellent solubility,a low processing temperature,large remnant polarization and little fatigue.Based on all these promising properties,P(VDF-TrFE)is an excellent candidate for next-generation Ferroelectric Random Access Memory(FRAM).To achieve micro-and nanosize ferroelectric polymer pillars it is necessary to spread P(VDF-TrFE)in ultrathin films and then patterning nanostructure without defects and damages which usually caused by conventional e-beam and photolithography.Good quality control of ultrathin ferroelectric polymer films and alternative patterning techniques are urgently demanded.ETFE fluoropolymer film is produced from a copolymer of ethylene and tetrafluoroethylene resin.This material has naturally low adhesion,high temperature and stress crack resistance.In this thesis we demonstrate that reusable flexible ETFE molds can be effectively used in nanoimprinting P(VDF-TrFE)pillar structure.These new molds are very cheap and easy to replicate from nickel and silicon master molds.A process sequence for ETFE stamp fabrication was developed.The fabricated molds can consist of different patterns like holes or pillars with the micrometer or nanometer size.The pattern was transferred by nanoimprint lithography.Optimal NIL parameters were also investigated.All ETFE molds were successfully used for patterning P(VDF-TrFE)micro and nanostructure.