Coupling coefficient improvement for inductor coupled vertical interconnect in 3D IC die stacking

We proposed a vertical magnetic coupled interconnect design procedure for 3D IC stacking. As the interconnect is modeled as a coupled inductor pair, we can convert it into a bandpass filter by adding series and shunt capacitors. With given center frequency and bandwidth of the bandpass filter, the required self and mutual inductance in magnetic coupled interconnect and serial and parallel capacitance can be calculated quickly. In our design using TSMC 0.18µm CMOS process, the addition of capacitors increased the transmission coefficient by 7dB. The size of loops for magnetic coupled interconnect is 200µm, the communication distance is 30µm. By using an ASK modulation scheme, we can up-covert the baseband signal spectrum to the lower loss passband of the filter. Our bandpass interconnect can achieve 3.5 Gbps data rate and 6.77pJ/bit power consumption.