Process Integration, Characterization, Modeling and Reliability of a 10K Poly Resistor for Low Power Mixed Signal VLSI Applications

Many IC applications employ both analog and digital circuits, and therefore it is desirable to integrate both analog and digital functions on the same chip (mixed signal chip). A mixed signal chip uses logic gates to perform digital signal processing while the analog cells allow the chip to interface with the analog environment. These analog cells include I/O blocks containing resistors, capacitors, reference voltage sources and comparators. Integration of all these digital and analog components on a single chip offers high packing density and low power CMOS at a lower cost. Most commonly used materials for high R value resistors are nichrome, tantalum and cermet (Cr-SiO). Extra manufacturing steps involved in depositing and patterning of these films is expensive and therefore new and innovative process for high R value resistors is needed. The authors have integrated very reliable high R value poly silicon thin film resistors at the cost of one extra masking step in a CMOS process. The authors present the results on matching, flicker noise performance and reliability of poly silicon thin film 10K resistors. Also a comparison is performed with thin film HIPO (IK) resistor