Intrabay System Research Articles

Optimal vehicle allocation for an Automated Materials Handling System using simulation optimisation

The Automated Materials Handling System (AMHS) in the semiconductor industry plays a vital role in reducing wafer cycle times and enhancing fabrication facility (fab) productivity. Due to the complexity of the manufacturing process and the stochasticity introduced by the inherent variability of processing times, the vehicle allocation for the AMHS is a challenging task, especially in 300 mm wafer fabs where the AMHS comprises both the interbay and intrabay systems to perform the timely deliveries. This paper studied the vehicle allocation problem in a typical 300 mm wafer fab. We formulated it as a simulation optimisation problem and proposed a conceptual framework to handle the problem. A discrete event simulation model was developed to characterise the AMHS, and the technique of simulation optimisation was applied to obtain the optimal vehicle allocation for both the interbay and intrabay systems. To demonstrate the feasibility and advantages of the simulation optimisation approach, a photobay example was used to compare the solution derived from the analytical model and simulation optimisation model. Finally, an empirical problem based on real data was conducted to show the viability of the proposed framework in practice.

The performance of the number of vehicles in a dynamic connecting transport AMHS

A new concept of the dynamic connecting transport automated material handling system (AMHS) is proposed. This paper analyses the performance of the number of vehicles in a dynamic connecting transport AMHS in a simplified 300 mm wafer fab. Discrete-event simulation models are developed in e-M Plant™ to study the system performance. To avoid congestion or idle time in the intrabay system, the control of the upper limit or the lower limit on the number of vehicles can be the feasible solution. Thus, four strategies are identified and their performances are also investigated. In addition, several different operation environments such as the flow rate and the product-mix are used to investigate the performance of the dynamic connecting transport AMHS.

VEHICLE ANAGEMENT OF AMHS IN 300MM WAFER FAB

ABSTRACT In this paper, a vehicle management framework for connecting transport of automated material handling system (AMHS) in 300mm wafer fab, which integrates the interbay and intrabay systems, is proposed. Based on operational area of vehicles, we extend our previous study and propose “vehicle type” concept for vehicle management in the AMHS. Three types of vehicle management scheme are analysed and discussed, in order to assign vehicles flexibly and improve performance of transport environment. These include 1) fixed vehicle type, 2) virtual vehicle type, and 3) dynamic vehicle type.