Investigation of PECVD dielectrics for nondispersive metal-insulator-metal capacitors

Metal-insulator-metal (MIM) capacitors with PECVD nitride exhibit trap-induced dispersive behavior, which leads to degradation in capacitor linearity at low frequencies, limiting the accuracy in precision analog circuits. While LPCVD oxide results in nondispersive behavior, the high deposition temperature excludes the use of LPCVD dielectrics for MIM capacitors using the standard back-end metal layers as capacitor bottom plates. The latter is preferred in view of the low substrate coupling needed for RF applications. In this work, alternative PECVD dielectrics have been investigated with respect to frequency dependence of voltage linearity, hysteresis, matching, and leakage characteristics. It will be shown that ONO stacks offer a combination of good voltage linearity, absence of dispersive behavior and hysteresis, excellent matching, and low leakage.