Research On The Electroforming Filling Process Of Nano Trench Structures

Compared with traditional complex optical Lithography,nanoimprint lithography has the advantages of ultra-high resolution,high yield and low cost,so that it is regarded as one of the most potential nano lithography technique to fabricate nanostructures.Imprint stamps are the most important part of nanoimprint lithography.At present,the imprint stamps made of metal nickel have been applied to fabricate micro-nano structure.And compared with traditional silicon stamp,nickel stamp has high mechanical strength and long service life.Therefore,metal nickel is praised as the most potential material in promoting nanoimprint lithography to be widely used in industrial production in the 21 st century.However,the aspect ratio of the nanoimprint stamp made of metal nickel is small.it has great significance for promoting nanoimprint lithography to be widely used in industrial production that fabricating a nickel stamp with high strength,long life,and high-aspect-ratio nanotrench structures.In order to fabricate this nickel stamp,the filling of nanotrench structures with high-aspect-ratio has to be done firstly.In this paper,according magnetron sputtering technology,physical vapor deposition technology and micro-electroforming technology are used to fill nanotrench structures with different aspect ratios based on the characteristics of each thin film deposition process.Compared with the step effect occurred in filling of nanotrench structures by using magnetron sputtering technology and the double metal grating happened in filling of nanotrench structures by using evaporation technology,the filling of nanotrench structures with high-aspect-ratio by using micro-electroforming has many advantages,such as high filling efficiency and good controllability,So in this paper,the micro-electroforming is used to fill nanotrench structures with high-aspect-ratio ultimately.However,a void is usually formed in the filled process due to the different abilities of mass-transportation inside and outside of the trench structure with high-aspect-ratio during the electroforming process.It makes the distribution of electron density of different locations is non-uniform.With higher electron density,the edge of the nanotrench is deposited faster than the side wall and the bottom,forming a void after the trench is sealed.In order to improve this phenomenon,this paper uses the electrostatic adsorption principle of Janus green B molecule to eliminate the process defect by adding the leveling agent JGB to the electroforming bath.During the electroforming process,Janus green B mainly adsorbs at the edge of the nanotrench due to the electrostatic attraction caused by the locally high electron density and decreases the rate of metal electroforming process.Based on this,this paper completes the filling of nanotrenches without voids and the trenches have aspect ratio with 1:1(100 nm depth,100 nm linewidth)and 2:1(200 nm depth,100 nm linewidth).Based on the combination of nanoimprint technology and electroforming process,a nickel nanoimprint stamp on the flexible basement with six nanograting areas of 1.3 mm× 1.3 mm size,200 nm pitch,100 nm linewidth and 100 nm depth was replicated successfully.And a monolayer film was deposited on the surface of the replica nickel stamp to reduce the adhesive force between the resist or polymer substrate and the stamp surface during demolding,it also reduces the deformation of the substrate surface structure.Finally,a set of verification tests were done using nickel stamp with lower surface energy.The experimental results show that the feature dimensions of the replicated stamp is almost the same as that of the corresponding master stamp.And the mechanical strength of the replica is sufficient for the hot embossing process.