CREATING ELECTRICAL CONTACTS BETWEEN METAL PARTICLES USING DIRECTED ELECTROCHEMICAL GROWTH

Electrical connections in microelectronics are usually established by means of photolithography to define the conducting channels, But metho ds that do not involve lithography have been explored, such as the use of electrodeposition(1) or electropolymerization(2-6) to grow random structures of conducting-material between two electrodes. This approac h has been used to make diodes, transistors and signal amplifiers base d on conducting polymers(2,3). Template-based(7-12) and thermal platin g(13) strategies have also been used to direct the growth of electrica lly conducting: media, One advantage of these approaches over photolit hography is the possibility of forming contacts in three dimensions an d so achieving enhanced data-processing densities. Previous electroche mical approaches have required that the electrodes to be connected are physically linked to the external voltage source. Here we show that e lectrodissolution and electrodeposition processes in an applied electr ic held can be exploited to create directional growth of copper deposi ts between copper particles that are not connected to an external circ uit. Moreover, the particles distort the electric field in such a way as to focus the diffusion of copper ions and consequently the directio n of 'wire' growth, enabling the particles to be connected to one anot her in a directional and controllable manner. This suggests that appro priately directed electric fields may be used to connect an array df s uch particles into an arbitrary circuit pattern.