Effect of substrate material on crosstalk in mixed analog/digital integrated circuit

As the level of integration increases in ICs, the combination of analog and digital functions on the same silicon substrate has become increasingly common. One of the most difficult problems in mixing analog and digital functions is crosstalk through the common substrate. Although there has been some analysis of the crosstalk problem in the literature, there has been relatively little discussion of the effect of different kinds of substrate material on crosstalk. In this paper we discuss crosstalk results obtained in a CMOS process with different epi thicknesses (including no epi), bonded wafer silicon-on-insulator, and junction isolated p-wells and n-wells. The results show that is possible to obtain crosstalk reduction of 10 times or more compared to traditional CMOS epi substrates, thereby enabling circuits to be built with higher levels of integration and better performance.<<ETX>>