Advanced Cu-Cu thermocompression bonding methodology for future 3DICs

A high-precision Cu-Cu bonding system for three-dimensional integrated circuit (3DIC-) fabrication adopting a new precision methodology is proposed. For Cu-Cu bonding, temperature and pressure controllability are key factors for overlay accuracy and bonding quality. A new pressure profile control system is applied in the thermocompression bonding process. The temperature characteristics of the bonding unit are analyzed using an FEM loop model of the core module, linked with a temperature control circuit utilizing the control algorithm in the actual bonding tool. Experimental results show that overlay accuracy is 230 nm or better for Cu-Cu permanent bonding. These developments will contribute to the fabrication of future 3DICs.