We have studied the problem of critical dimension (CD) control in trilayer nanoimprint lithography. A newly developed hyperbranched polymer, named Hybrane, is used as the top imaging resist instead of the frequently used PMMA, because of the higher etch resistance of the former polymer. Dot arrays of 100 nm are fabricated with a good reproducibility and a CD control accuracy better than 10 nm. Moreover, an over-etch process can be used to tailor the dot dimensions over a wide range. Thus, metallic dot arrays of different diameters and thicknesses can be obtained by nanoimprint using the same mold. Magneto-optical measurements have been performed on fabricated Co dot arrays to demonstrate the usefulness of the method.