Characteristics and process stability of complete electrical interconnection structures for a low cost interposer technology
Silicon interposers enable the heterogeneous integration of high performance systems. This paper focuses on interconnections from one chip to a neighboring chip in a side-by-side interposer approach. We investigate the performance of interconnections on a typical silicon interposer with polymer applied to the redistribution layer on both sides using electromagnetic simulations. The simulations are valued by measurements. Our measurements show that microstrip lines with <0.3 dB/mm insertion loss at 30 GHz can be achieved with a typical polymer based interposer process. In contrast to other work we extend the microstrip line model with pads on both ends to form a complete interconnection. Our investigations show that an insertion loss of <0.55 dB/mm can be achieved assuming dense inter-connections. We investigate the impact of technological variations during the manufacturing process of a silicon interposer. This is important to ensure electrical functionality (signal and power integrity) of the system in mass production. The results on technology variations during the manufacturing process of an interposer show that variations of 20 % in trace width and trace height are changing the characteristic impedance of the line, but do not significantly affect the signal integrity of sufficiently long lines. In contrast, variations of 20 % in polymer height and polymer permittivity in the redistribution layer have more influence on signal integrity of sufficiently long interposer interconnections.