Semiconductor Manufacturing Process Description

Abstract

In this chapter, we provide a process description of semiconductor manufacturing. Therefore, we describe the front-end and back-end areas in some detail. We introduce the notion of base system, base process, control system, control process, planning system, planning process, and finally of the information system from systems theory. Then we discuss important wafer fabrication operations including a description of the most important characteristics of the semiconductor manufacturing process. We also introduce the notion of complex job shops because this is the way wafer fabs are organized. Finally, we discuss the production planning and control (PPC) hierarchy in semiconductor manufacturing. From an operations management point of view, we differentiate between planning at the highest level, order release, scheduling, and finally dispatching at the lowest level. Each of these different functionalities is related to a certain horizon. Planning has a time horizon ranging from months to years. Order release takes place in a weekly or biweekly frequency. Scheduling is performed each shift or day. Finally, dispatching is carried out in a minute-by-minute manner depending on the speed of the material flow. We develop this PPC hierarchy because it forms the skeleton for the remainder of this monograph. 2.1 Semiconductor Manufacturing Overview A semiconductor chip is a highly miniaturized, integrated electronic circuit consisting of thousands of components. Every semiconductor manufacturing process starts with raw wafers, thin discs made of silicon or gallium arsenide. Depending on the diameter of the wafer, up to several thousand identical chips can be made on each wafer by building up the electronic circuits layer-by-layer in a wafer fab. There are about 40 layers for the most advanced technologies. Next, the wafers are sent to sort or probe, where electrical tests identify the individual dies that are not likely to be good when packaged.