This work proposes a novel unbalanced corporate-feed network antenna design with amplitude tapering of the radiated power to get a reduced sidelobe level. The phase imbalance of the asymmetric power dividers is compensated by integrated delay lines which maintain the aperture efficiency. The 10 dB beamwidth is reduced by 8.5% in E-plane and 10.2% in H-plane after the phase compensation. A 𝟏𝟔×𝟏𝟔 and a 𝟑𝟐×𝟑𝟐 array antenna have been designed for 230-290 GHz, i.e., a 23% fractional bandwidth. The 𝟏𝟔×𝟏𝟔 and 𝟑𝟐×𝟑𝟐 antenna's realized gain is between 29.4-32.1 dBi and 34.6-37.6 dBi, with sidelobe levels better than 21.2 dB and 20.5 dB, respectively. The design is optimized for being implemented by silicon micromachining. To the best of the author's knowledge, this is the first amplitude tapered corporate feed slot array antenna with delay lines for phase compensation that has been proposed in this frequency range with this wide operational bandwidth.