The conversion between electrical and optical signals underpins modern optical communication systems and increasingly requires tight co-integration with electronics at short length scales. Photonic integrated circuits based on thin-film lithium tantalate has emerged as a promising electro-optic platform due to its large Pockels coefficient, low birefringence, low bias drift, and high power handling, yet its integration with standardized microelectronic processes remains limited. Here we show that incorporating the copper Damascene process into thin-film lithium tantalate modulators enables a scalable, electronics-compatible fabrication approach. The resulting devices exhibit approximately 10% lower microwave loss than conventional gold-electrode designs, while simultaneously supporting watt-level on-chip optical power handling and maintaining a stable quasi-static half-wave voltage from 1 Hz to 1 MHz, with a bias point drift of only 0.4 dB over a 15-hour period when operated at 1.75 mW on-chip optical power. High-speed transmission experiments demonstrate line rates of 416 Gbit/s (PAM4) and 540 Gbit/s (PAM8) below the 25% soft-decision forward-error-correction threshold. These results establish a practical route toward scalable chip-on-wafer integration of electro-optic modulators with microelectronic circuits. Researchers demonstrate thin-film lithium tantalate modulators fabricated using a copper Damascene process, achieving lower microwave loss, exceptional bias stability, and high-speed data transmission up to 540 Gbit/s, while enabling scalable chip-on-wafer integration with microelectronics.