Research On High Density MIM Capacitance Based On High K Composite Media

High-permittivity (high-K) metal-insulator-metal (MIM) capacitors have recently been studied for the application of radio frequency (RF) and analog/mixed-signal (AMS) integrated circuits. However, a relatively large quadratic voltage coefficient of capacitance (Vcc) remains a serious challenge for the high-K MIM capacitors. To decrease the Vcc, it is proposed to employ the composite materials with positive and negative quadratic Vcc values, i.e., combination of high-K materials (usually positive quadratic Vcc values) and other negative quadratic Vcc values materials. Our research work mainly focuses on the combination of the HfO2and other materials, in order to find the MIM capacitor with high capacitance density and low quadratic Vcc.Two HfO2and BZT-HPO2MIM capacitors have been engineered with reactively sputtered (PVD) technique. It is found that the BZT-HfO2MIM capacitor can effectively reduce the quadratic Vcc value, while remain the relatively high capacitance density. Under100KHz measurement frequencies, the HfO2MIM capacitor has the capacitance density of12.9fF/μm, and the quadratic Vcc value of4270ppm/V2; The BZT-HfO2MIM capacitor has the capacitance density of10.2fF/μm2, and the quadratic Vcc value of2200ppm/V2; The quadratic Vcc value of the BZT mixed BZT-HfO2MIM capacitor reduces to about half value compared with that of the HPO2MIM capacitor. Furthermore, the Schottky emission also has been identified for both capacitors.The deposition of SiO2with plasma enhanced atomic layer deposition (PEALD) technique has been carefully investigated in this research work. In our experiment, the SiO2has been deposited by PEALD technique with Trisdimethylamino-silane (TDMAS) precursor and oxygen as follows:1, the films are deposited at different temperature from100℃to350℃;2, the films are also deposited at different substrate (Si, TiN). The investigation reveals that the deposition rate of the SiO2has the negative relationship with the temperature. The9nm and13nm PEALD SiO2MIM capacitor has been fabricated under200℃in order to investigate the electrical characteristics of the SiO2films. At100KHz measurement frequencies, the capacitance density of both capacitors is4.21and4.16fF/μm2, respectively; the quadratic Vcc is-1450and-2340ppm/V2, respectively.Since the combination of the HfO2and SiO2dielectrics can reduce the quadratic Vcc, the atomic layer deposition (ALD) technique based stacked MIM capacitors have been engineered in this research. The research results indicate that the insert of the SiO2films can reduce the quadratic Vcc of the MIM capacitor. However, the capacitance density also drops. With the adjustment of the thickness of the SiO2and the structures of the MIM capacitors, the ALD SiO2/HfO2/SiO2MIM capacitors have been engineered finally. Under100KHz frequency, SiO2(1nm)/HfO2(10nm)/SiO2(l nm) MIM capacitor has the capacitance density of10.2fF/μm2, and the quadratic Vcc value of1150ppm/V2. And SiO2(1.5nm)/HfO2(9nm)/SiO2(1.5nm) MIM capacitor has the capacitance density of9.3fF/μm2,and the quadratic Vcc value of615ppm/V2. For this structure, with the increase of total1nm SiO22, the capacitance density of the MIM capacitor drops by9%, and the quadratic Vcc drops by46%. With the proper arrangement of the SiO2and HfO2structure and thickness, our research reveals that the high capacitance density and low quadratic Vcc MIM capacitor can be achieved, approaching the critical requirement of the RF and AMS integrated circuits.