Levels of Capacity and Material Handling System Modeling for Factory Integration Decision Making in Semiconductor Wafer Fabs

Abstract

As the costs of building a new wafer fab increase, a detailed simulation model representing the production operations, the tools, the automated material handling systems (AMHS), and the tool-AMHS interactions is needed for accurately planning the capacity of these facilities. The problem is that it currently takes too long to build, experiment, and analyze a sufficiently detailed model of a fab. The key for building accurate and computationally efficient fab models is to decide on the right amount of model details, specifically those details representing the equipment capacity and the AMHS. This paper identifies a method for classifying a fab model by the level of capacity detail, the level of AMHS detail, or the level of capacity/AMHS detail. Within the capacity/ AMHS modeling level, our method further differentiates between detailed integrated capacity/AMHS models and abstract coupled capacity/AMHS models. The proposed classification method serves as the basis of a framework that helps users select the system components to be modeled within a desired level of detail. This research also provides a review of past-published literature summarizing the work done at each of the proposed fab modeling levels. A case study comparing the performance between an integrated capacity/AMHS model and a coupled capacity/AMHS model is presented. The study demonstrates that the coupled model generates cycle time estimates that are not statistically different than those generated by the integrated model. This paper also shows that the coupled model can improve CPU time by approximately 98% in relation to the integrated model.

The correct level of model complexity in semiconductor fab simulation — Lessons learned from practice

“…While in general simulation models produce more accurate results with increasing model detail [18] the achievable level of detail is limited: From a certain point on, not all required information regarding the real system's behavior is available. In this case, assumptions have to be made.…”

Reducing simulation model complexity by using an adjustable base model for path-based automated material handling systems - a case study in the semiconductor industry

“…So for instance, if the objective consists in roughly estimating the queue length in front of a tool, a less detail model is needed than if the aim is to investigate the fabs throughput under the condition of varying lot sizes. Nevertheless, the literature provides some guidelines to support choosing the right abstraction level and to appropriately classify them (e. g. Thesen and Travis 1989, Robinson 2007and Jimenez et al 2008). The proposed model in section 3 refers to this.…”

“…However, to give an idea of the herein presented model's complexity Jimenez et al (2008) is cited. Accordingly, the level of detail of the AMHS model can be described approximately as an integrated model with "a few, but not necessarily all components" (class E) and some facets "not represented accurately" (class 5).…”

“…Accordingly, the level of detail of the AMHS model can be described approximately as an integrated model with "a few, but not necessarily all components" (class E) and some facets "not represented accurately" (class 5). Since the process model triggers the AMHS to execute transportation tasks the overall wafer fab model is classified as case (d) in quadrant 4-for explanation in detail see Jimenez et al (2008).…”

Simulation of a full 300mm semiconductor manufacturing plant with material handling constraints

“…Our approach completes all of his recommendations. In Jimenez et al (2008), the authors describe a method for classifying wafer fab models by their level of details. Six levels of details for building production capacity and six levels of details for building the AMHS.…”