High Value and Low Value Polysilicon Resistors With Self-Aligned Ohmic Contacts Using One Mask Level
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a technique whereby polysilicon resistors of two different resistor values may be obtained with only one mask level. The resulting resistors have self-aligned ohmic contacts. Polysilicon load resistors have found increasing use in high performance bipolar circuit technologies because their low capacitance properties translate into increased switching speed. For maximum flexibility, circuit designers desire two values of resistor sheet resis (Image Omitted) tance (typically on the order of 500 ohms per square and 2000 ohms per square). Achieving these two types of resistors involves two mask sequences for the two different implant doses. In the technique disclosed herein, the two resistor values are still achieved, but the mask number is reduced to one. Fig.