metalinsulatormetaltype

Metal-insulator-metal type, commonly called a MIM structure, is a sandwich-like arrangement used in electronics in which a thin insulating layer separates two metal electrodes. In microelectronics, MIM capacitors rely on this configuration to achieve higher capacitance in small areas and to offer fast response times compared with bulk dielectric structures.

The insulating layer is a dielectric material chosen for low leakage and controlled thickness, typically from a few angstroms to tens of nanometers. Common dielectrics include SiO2, Si3N4, Al2O3, HfO2, and Ta2O5; high-k dielectrics are often used to increase capacitance. Electrodes are usually compatible metals such as aluminum, copper, or noble metals depending on the fabrication process.

Fabrication involves sequential deposition of the bottom metal, the dielectric, and the top metal, using sputtering, evaporation, chemical vapor deposition, or atomic layer deposition. Patterning defines individual capacitor cells, and annealing may be used to tune material properties.

Performance and trade-offs include high capacitance density and fast switching, limited by leakage current through thin dielectrics and dielectric breakdown at high fields. Leakage is often dominated by tunneling in very thin films, and interfacial traps can affect voltage dependence and reliability.

Applications span decoupling and timing capacitors in CMOS and RF circuits, tunable components in analog microelectronics, and storage elements in certain types of integrated circuits. The MIM capacitor is related to, but distinct from, MIM diodes, which use a similar stack for tunneling-based rectification rather than capacitive energy storage.