New method for monitoring of analogue processes-evaluation of the impact of metalisation on the performance of precise analogue resistors

The high-ohmic polycrystalline (HIPO) resistor is one of the basic devices used in analogue-digital designs. The requirements for accuracy, voltage and temperature linearity, and matching performance are very high. On the other hand, from the process point of view, this is one of the least controlled devices, whose properties depend on all subsequent temperature steps and layers in the backend process. In addition, the surroundings and the topology influence the characteristics of this resistor. By using a new test structure and method, we are able to characterise the dependence of the HIPO parameters on process changes and topology as it appears in the real ASIC. In this paper, we report the most important impact we have discovered, that of metal lines placed in parallel with the HIPO resistors. Different metalisation schemes are compared with regard to the effect on the analogue characteristics of the HIPO resistor.