Development of a high-performance silicon monolithic circuit

A silicon monolithic circuit consisting of reduced isolation capacitance and improved resistor design, and utilizing a new structure for dip open emitters is described. In this arrangement, the transistors are formed in a high-resistivity epitaxial layer, which reduces the parasitic isolation capacitance by more than a factor of two. The resistors are n-type rather than the conventional p-type. It is difficult to make p-type resistors in thin exitaxial layers because they tend to short to the substrate. Even using a subcollector-type layer between the p-type substrate and the expitaxial layer creates both a resistor-control problem and degradation of the high-frequency characteristics of the p-type diffused resistors. The high sheet resistivity of the epitaxial layer permits the formation of n-type resistors with excellent high-frequency performance. Typically, for identical resistor values the previous p-type resistors dropped to 90% of their value at 80 MHz whereas these n-type resistors dropped to 90% of their value at 2.5 GHz.