High-density RF MIM capacitors using high-k La₂O₃ dielectrics

The integrity of the metal-insulator-metal (MIM) capacitor with high-k La₂O₃ dielectrics formed using a 400°C back-end process I was investigated. A very high capacitance per unit area of 9.2 fF/μm² was achieved for La₂O₃ MIM capacitors at 1 MHz, significantly reducing the chip size of radio frequency (rf) circuits. A mathematical derivation, involving measured 5 parameters, yielded the small voltage-dependent capacitance (ΔC/C) ≤100 ppm at 1 GHz, indicating that the precision capacitor circuit can be applied in the rf regime. Furthermore, such a high capacitance density can be maintained as the frequency is increased from 10 KHz to 20 GHz with a large Q factor ≥90.