Front end, Back end

In the semiconductor industry all the process steps a wafer undergoes are called the front-end process, i.e. lithography, diffusion, ion implantation and applying the wiring levels. A wafer may pass through some stations several times, covering a distance of several kilometers in its up to seven-week odyssey. In the end the individual process steps may number as many as 500, all taking place in the front-end production hall, casually referred to simply as the front-end fab.

Front-end fabs are very capital-intensive. Furthermore, automation has reached a high degree. That’s why the labor cost does not make so great an impact on the manufacturing costs and front-end fabs are often also operated in high-wage countries.

Once the wafer has left the front-end fab, it goes to an intermediate storage facility, known as the “die bank”, and from there to the back-end fab. Here the second part of the chip manufacturing process begins. In the back-end process – taking one to two weeks – the wafer is cut up into individual ICs using lasers or dicing saws with diamond blades. They’re tested, assembled, re-tested and at the end they’re packed ready for dispatch.

Compared to front-end fabs, the labor cost in back-end fabs accounts for a larger share of the manufacturing costs. The machines are not as expensive and the proportion of manual work is higher. That’s why back-end sites are mostly located in low-wage countries.

Companies who have specialized exclusively on the front-end process are called foundries. The largest are TSMC, UMC (both in Taiwan), Chartered Semiconductor (Singapore) and SMIC (China).Companies who have specialized exclusively on the back-end process are called back-end subcontractors. The largest are Amkor (USA), ASE, Siliconware Precision (both Taiwan). There the specialization has already progressed to such a stage that some do only the testing and others only the assembly and packaging.
Mastery of front-end and back-end processes alike belongs to the concept of an IDM (Integrated Device Manufacturer). Infineon is an IDM of this kind. What’s more an IDM doesn’t just manufacture its chips, it also develops and markets them itself.

(extracted from IFX Emag 29 Nov 2006, Joe corner)