Planarization of Nonmagnetic Films on Bit Patterned Substrates by Gas Cluster Ion Beams

We studied Ar gas cluster ion beam (GCIB) planarization effect on patterned surfaces refilled with Cr, Ta and SiO₂. The patterns of 20 nm in depth were fabricated on Si substrate by using electron beam lithography and CHF₃ -reactive-ion-etching. The bit pattern pitches and the height of peak-to-valley were 150/200/300/400 nm and 20 nm, respectively. Then, refilling materials were deposited 30 nm in thickness on the patterned substrates. The test samples were irradiated by Ar-GCIB and the resultant surface profiles were measured by atomic force microscopy. Acceleration energy for a cluster was 20 keV. The dose was set from 2 × 10¹⁵ to 5 × 10¹⁵ ion/cm². Although there was a difference in the dose, the patterns disappeared clearly by irradiating GCIB. The reduction rate of peak-to valley height decreased with decreases of the pattern pitch. We indicated that GCIB irradiation is effective for the planarization of patterned surface refilled with Cr, Ta, and SiO₂.