Characterization of Al2O3-HfO2-Al2O3 sandwiched MIM capacitor under DC and AC stresses

Metal-insulator-metal (MIM) Capacitors are widely used for radio frequency (RF) and analog mixed signal (AMS) circuits, and dynamic random access memory (DRAM) applications [1]. Although high capacitance density of MIM capacitor for RF and AMS circuits is required to reduce the chip size and system cost, the conventional dielectric materials, such as SiO
2
and Si
3
N
4
, as the thickness of dielectric scales down, emerge as key limitations due to high leakage current and reliability issues. High-k (HK) dielectric, such as HfO
2
, Al
2
O
3
, ZrO
2
, Ta
2
O
5
, and La
2
O
3
, is necessary to achieve the high capacitance density and to reduce the leakage current [2]. Among the various HK dielectric candidates, hafnium-based MIM capacitors are widely used due to their high capacitance density, good thermal stability, and high band gap [3]. However, HK dielectric for MIM capacitors induces high voltage linearity and poor reliability characteristics after electrical stress, due to defects in the metal-insulator interface. The reliability characteristic of MIM capacitor under electrical stress is related to the injected charge in the interface of HK dielectrics [4]. These degradations cause the distortion of MIM capacitors, which limits the performance of the RF and AMS circuits. Hence, an accurate analysis of the degradation of MIM capacitor under electrical stress is required in order to stabilize these characteristics. Moreover, various kinds of voltage shape can be applied to the MIM capacitors. However, there was little study on the effect of stress voltage type on the reliability of advanced MIM capacitors. In this work, reliability of MIM capacitor with high capacitance density was analyzed using three kinds of voltage stress; constant voltage stress (CVS), unipolar voltage and bipolar voltage stresses.