New process technology uses copper for internal electrodes

A team from Fujitsu Laboratories says the use of copper for internal electrodes lowers the impedance of the capacitor and, by mounting the capacitor directly below the lsi chip, impedance from the circuits can also be reduced. According to Fujitsu, this results in an increase of current flow efficiency by 10 times compared to previously available technology. The innovation could enable the next generation of high speed computers operate at even higher speeds. Conventional ceramic chip condensers used as power supply capacitors have been mounted on the surface or rear of the circuit board or lsi chip package, supplying current to the lsi chip through the circuit wires. This method results in a relatively long electrical pathway between the capacitor and lsi chip which raises impedance and could potentially create instabilities in future high speed computers. In addition, because nickel, which has comparatively high resistance, has conventionally been used for the internal electrodes in the capacitor, the impedance of the capacitor itself has been high – limiting the speed of the power supply current. The new production technique has been made possible using nanoparticle deposition technology. For the first time, internal electrodes have been made using low resistance copper, while employing ultrafine through hole contact construction. Fujitsu says this enables connection directly beneath the lsi chip, while a thin film dielectric layer has also been used to enable high capacitance (1 µF/cm2•layer). Fujitsu Laboratories plans to continue with development of technologies to enable miniaturisation of the capacitor terminals and multilayering, aiming to apply the new technology to computers around 2015.