A purposed semi-cylindrical hyperlens is designed for nanolithography, which can form 20nm (or less) line width patterns with 193nm working wavelength. The hyperlens employs aluminum (Al, @193nm wavelength) and magnesium oxide (MgO, ) as the materials of alternating metal and dielectric thin layers. Taking aluminum instead of silver is a more economic solution for manufacture, and the dielectric coating acts as an anti-reflectivity of aluminum to enhance transmission. The optimum thickness of aluminum for best image fidelity has been found based on two 20nm wide slits with 40nm spacing. Incorporated with phase shifting mask (PSM) technology, the image contrast is much better than that of ordinary mask (Chrome on Glass, COG). The full wave simulations are executed and the results validated our approaches. The semi-cylindrical hyperlens made of aluminum and magnesium oxide gives potential for nano-scale manufacture, optical information storage and biomedical imaging.