Recent Advances in Step and Flash Imprint Lithography

The goal of the Step and Flash Imprint Lithography (SFIL) development program is to enable patterning of sub-100 nm features in a manner that has dramatic cost savings over conventional projection lithography techniques. The SFIL process is performed at room temperature and with minimal applied pressure, and we believe the use of low viscosity materials and photopolymerization chemistry will enable SFIL to achieve the throughput required for use in the microelectronics industry. Additionally, the rigid transparent imprint template used in SFIL enables a precision in overlay alignment that is difficult to achieve in other imprint schemes. This paper presents recent work that has focused on improving the resolution of the etch barrier formulation, modeling the free radical polymerization reaction to include oxygen inhibition, and improving the etching processes used to amplify the aspect ratio of the polymer features. Replacing the silylated crosslinker component in the etch barrier with ethylene glycol diacrylate has greatly reduced the viscosity of the solution without sacrificing feature resolution. Etch process development has shown that a CF4/O2 feed rich in CF4 provides sufficient etch selectivity to etch the residual etch barrier layer, while O2 rich feed provides sufficient selectivity for the transfer layer etch. With this recent work we have demonstrated polymer-on-Si semi-dense lines smaller than 50 nm made with the SFIL process. Studies of defectivity have not revealed significant defect generation, and in fact have revealed no substantial defect propagation. Oxygen diffusion into the polymerizing imprint material inhibits the free radical curing reaction to such an extent around the imprint perimeter so as to create a