Researchers from the Japanese company Mitsui have developed a new method for the production of thin-film capacitors. The components could be used as part of future 32nm and 25nm chips.
The new type of capacitor, which Mitsui calls AEC-1, uses ceramic barium titanate as the dielectric material. The material was applied in a 0.6 µm thin layer between a 20 µm thick copper electrode and a 50 µm thick nickel electrode. Compared to the usual multi-layer ceramic capacitors, the single-layer capacitors developed now have a lower inductance and a higher electrical capacitance.
Mitsui employees managed to measure the electrical capacity to increase to about 1µF per square centimeter by adjusting the manufacturing process. To bond the ceramic dielectric material to the electrodes, the researchers did not use a resin, but took advantage of the heat-resistant properties of the nickel electrodes. To this end, the ceramic material was formed directly on the electrode by means of local heating. A reduction in the electrical capacity, which would occur when resin is used, then does not occur.
The new capacitors can be incorporated directly into the substrate of chips; the necessary structures for the capacitors, such as electrodes and connection points, can be etched into the metal foil. By further reducing the thickness of the metal layers of the capacitors, the entire thin-film capacitor could reach a thickness of only 35 µm. One single-layer thin-film capacitor can replace several dozen multi-layer ‘traditional’ capacitors.
Before the thin-film capacitor is actually used, Mitsui first wants to develop a method to replace the nickel electrodes with copper ones: nickel is more difficult to etch than copper and is sensitive to magnetism.