Falk Stefan Pappert

Implementation of a simulation-based short-term lot arrival forecast in a mature 200mm semiconductor fab

The ability to perform lot arrival forecast at work center level is a key requirement for pro-active FAB operation management. Visibility to this information enables preemptive resource allocation and bottleneck management. Today, the work center lot arrival forecast is achieved through the use of short term simulation technique in Infineon Dresden. High fidelity simulation model that includes detailed modeling feature such as attribute-based sampling procedure, dedication and temporary tool blocking is built automatically through the transformation of data queries from data sources. In this paper, we present the results of our model validation work, comparing the FAB and forecasted lot arrival of the defect density measurement work center. Due to the high capacity demand of automotive product that requires more than 20 inspection steps; engineering lots and preventive maintenance of DDM must be scheduled at the right time. This can only be achieved with high quality lot arrival forecast.

A prototype simulation tool for a framework for simulation-based optimization of assembly lines

General purpose simulators offer an easy way to create simulations for a large variety of scenarios, although they are prepackaged with some drawbacks. To achieve their usefulness for most cases they need additional overhead and custom made extensions for special behavior which comes at enormous runtime and development cost. Especially when working with simulation-based scheduling, these are severe issues since runtime is precious and automated generation of the models is a necessity. Another approach to simulation challenges is the creation of a very specific custom-built simulator which focuses on a chosen domain where it excels compared to other simulators. In our paper, we introduce a simulator designed specifically for the simulation of complex assembly lines with their common characteristics including thousands of activities, realistic schedules, priority rules, resources and model restrictions. It furthermore allows the creation of new strategies for different aspects of scheduling in this environment.

Framework for simulation based scheduling of assembly lines

Planning and scheduling of assembly lines is a complex problem which is often very hard to solve with classical scheduling approaches. A promising way of dealing with problems of this domain is simulation based scheduling. We introduce the architecture of a framework which is designed to aid in the creation of solutions for assembly line workforce scheduling. The framework combines a meta model to describe production networks and facilities with a complete modular design. Through the combination and reuse of exchangeable modules the framework offers the opportunity to focus on the development of optimization. Besides necessary input and output components there is a generic KPI data structure which allows to manage and calculate new values without the need to adapt existing modules. Optimizer modules are considered to be implementations of solution. To prove our concept we implemented scheduling solutions from previous industry projects with our new framework.

Time bound control in a stochastic dynamic wafer fab

Time bounds are a common constraint in wafer fabs. Releasing wafer into a time bound sequence leads to a tradeoff between capacity loss and yield loss due to violations. Two common approaches to tackle this challenge are static scheduling and dispatching rules. While static scheduling faces problems with the dynamic and stochastic nature of a wafer fab dispatching rules often lack the global perspective causing either unnecessary violations or capacity waste. In this paper, we present an approach taking elements of both these solution approaches to address time bound constraints and compare it to existing approaches.

Impact of time bound constraints and batching on metallization in an opto-semiconductor fab

Time bound sequences are constraints deemed necessary to ensure product quality and avoid yield loss due to time dependent effects. Although they are commonly applied in production system control they cause severe logistical challenges. In this paper, we evaluate the effects of time constraints in combination with batching on a real metallization work center of an opto-semiconductor fab. We use simulation to analyze the impact of these production constraints and point out potentials to increase work center performance. We have a closer look at the required planning horizon, the influence of dedication, the capacity loss due to time bounds and the effects of batching strategies on wafer cost. Our results show the importance to tackle these issues. Furthermore, we will discuss actions taken in response to the experiments.

Cluster based analytical method for the lot delivery forecast in semiconductor fab with wide product range

The usual forecast method in semiconductor industry is simulation. Due to the manufacturing environment, the number of processes and the multitude of disturbing factors the development of high-fidelity simulation model is time-consuming and requires a huge amount of high quality basic data. The simulation facilitates a detailed prediction possible, but in many cases this level of detail of the forecast information is not required. In this paper, we present an alternative forecast method. It is considerably faster and the results for a subset of parameters are comparable to simulation. The solution does not need a complete fab model but a limited mathematical system and some fast algorithms which make the forecast of important parameters or characteristics possible. The prediction is based completely on statistics extracted from historical lot data traces. It is already implemented and tested in a real semiconductor fab environment and we also present some validation results.

Personaleinsatz- und Ablaufplanung für komplexe Montagelinien mit MARTA 2

Der folgende Bericht beschreibt eine prototypische Implementierung fur eine simulationsbasierte Personaleinsatzplanungsheuristik fur komplexe Montagelinien. Der Ansatz wurde bereits bei verschiedenen Unternehmen getestet und wird hier fur die Flugzeugmontage vorgestellt.