The process steps described in the previous section have to be combined properly to produce an IC. This task is commonly referred to as process integration. Process integration [Chi92][Pim93] can be generally divided into three basic components:
The complexity of process integration tasks can vary from low level, like the modification of just one module, to high level, like the development of a new technology from scratch. One popular approach between these two extremes is the enhancement of a complete process sequence by shrinking the minimum feature size used in an already available technology. While such `technology-shrinks' are generally less complex than the tasks involved in the development of an entirely new complete process sequence they usually entail more than just the implementation of smaller devices. Thus, many of the process steps must be modified, and even new ones may have to be developed.
The process components are realized by so called process modules. The process modules are the fundamental building blocks of the entire manufacturing process. Usually one module comprises a lithography step followed by pattern transfer and several layer formation as well as modification steps. The combination of the process modules constitutes the process sequence and is described and documented in a flowchart. Most of the modules can be used in different technologies or at least for different circuit types realized in one technology. However, they cannot be processed independently from each other as a more or less strong interrelation exists. An obvious example is the thermal budget of a process module that influences all previous steps in a similar way.