Polysilicon Resistor Process
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
It is a well known fact that considerable improvement in both chip density (greater than 20%) and performance can be obtained by the replacement of a single crystal silicon resistor by a higher sheet rho polysilicon resistor. There are several other advantages of using polysilicon resistors: Polysilicon resistors can be placed over the ROI (recessed oxide isolation) rather than in the EPI, giving added increase in the chip density; and the capacitance of polysilicon resistors over ROI is considerably reduced over the conventional I/I (ion implanted) resistors. By contrast, high Rs (sheet resistance) I/I single crystal silicon resistors cannot be obtained with extensions of conventional processes. This is because the relatively highly doped epitaxial layers make Rs control extremely difficult.