Track
Conductor tracks (also interconnect or rarely pathway ) are in the microelectronics electrically conductive compounds having a two-dimensional curve, that is, in a plane, called the conductor track or metallization. They are used to connect electronic components on printed circuit boards and integrated circuits , that is, they are used for power or voltage supply, signal transmission and also for temperature dissipation.
Printed circuit boards for very simple circuits can possibly get by with only one conductor track level, which for example was applied and structured on one side of a printed circuit board. However, very few circuits can be so strongly disentangled that no conductor tracks cross with only one level. With the exception of a few manufacturing tricks, such as bridging a conductor track with the aid of a component, at least one additional level is therefore necessary, for example two-sided printed circuit boards. In modern, very complex circuit boards, multi-layer, so-called multi- level or multilayer circuit boards are therefore used, in which conductor track levels and electrically insulating levels (e.g. fiber-reinforced plastic) alternate. The connection between individual conductor track levels is made using vertical, electrically conductive connections, so-called vias ( English vertical interconnect access ).
In the case of integrated circuits, the conductor track levels are usually only ever produced on one side of the substrate (usually a silicon wafer ) and become thicker as the distance from the chip surface increases. Current top products require up to twelve conductor track levels, e.g. B. Llano series from AMD (eleven copper levels) or Virtex-5 from Xilinx (twelve levels: eleven copper + one aluminum).
A good electrically conductive and relatively cheap material is required as the conductor track material (economical production). That is why copper is usually used in printed circuit boards . For a long time, almost exclusively aluminum (usually in an aluminum-copper alloy ) was used in integrated circuits , which can easily be structured by dry etching after a full-surface deposition ( physical vapor deposition ) . However, today's top products require better electrically conductive materials, which is why many manufacturers have switched to copper conductor tracks. Since copper cannot be structured by dry etching, new techniques ( galvanic deposition , chemical-mechanical planarization , diffusion barriers, etc.) had to be introduced, which make the manufacturing process more complex and therefore more expensive.
So that no short circuits or high leakage currents occur, the conductor tracks must be well insulated from one another. Due to the layer structure of wiring with several levels, the dielectric or the dielectrics can be divided into two classes with regard to their function: 1.) the dielectric between the conductor tracks in one level ( inter-metal dielectric , IMD) and 2.) the dielectric between two interconnect layers ( English inter-level dieletric ILD).