Total operational efficiency (TOE): the determination of two capacity and cycle time components and their relationship to productivity improvements in a semiconductor manufacturing line

Abstract

Short cycle time manufacturing (SCM) concepts have been developed to help understand and manage the performance of a manufacturing line. SCM assumes that each tool/toolset (and hence the overall line) can be described by a performance curve that relates cycle time to throughput, with cycle time increasing non-linearly as throughput approaches capacity. Productivity improvements are realized by reducing the components of capacity loss, which increases the overall capacity and, thus, shifts the performance curve. To implement SCM, all major components of capacity loss must be defined, including the primary driver for cycle time: idle-no-WIP. In order to achieve this, the analysis must look beyond a strictly tool-centric focus to a system view focus so that the interaction between the tool, operator, work-in-progress, etc., can be included in the components of capacity loss. This paper develops and explains total operational efficiency (TOE), which is a key component of SCM. TOE describes the capacity and cycle time components of a tool/toolset in a self-consistent and hierarchical way that reflect a system level view and where the interaction of the tool, operator, WIP, etc., are taken into account. Once these components and their relationship have been defined, it is then possible to more clearly articulate responsible owners and assess the possibility of improvement. The reality of most semiconductor manufacturing lines is that tool availability is rarely the largest detractor from capacity. Instead, other issues such as the amount of automation, line layout, cycle time requirements, technology mix, etc., become the prime determiners of the effective capacity. In addition, TOE enables meaningful comparisons to be made between different lines and for the better tracking of improvements over time in any given line on a component by component basis.