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Scheduling of multicluster tools has received much attention due to its complexity of interaction among cluster tools. A cluster tool comprises several modules such as processing modules, a transfer module with a single or dual-armed handling robot, and loadlock modules. A multicluster tool comprises two, three, or more cluster tools that are interconnected with each other. In this paper, we propose a deadlock prevention policy for noncyclic scheduling of dual-armed multicluster tools. The proposed deadlock prevention policy is effective for generating an efficient schedule for two or three-connected multicluster tools with a single or a dual-path flow. This is proven by analyzing the strict minimal siphon of the Petri net model. The performance of the proposed method is compared with that of a maximal permissible deadlock prevention policy. The results demonstrate that the proposed method is computationally efficient for larger state spaces and more suitable than conventional deadlock prevention policies for generating effective schedules for noncyclic scheduling of multicluster tools. Note to Practitioners—Scheduling of multicluster tools has recently attracted attention in the growing semiconductor manufacturing industry. Most conventional studies on multicluster tools focus on cyclic scheduling to minimize cycle time with swap strategy. The challenge addressed by this paper is to derive a deadlock-free schedule for multicluster tools with noncyclic operations. We propose a simple deadlock prevention policy that can be applied to large-scale timed Petri net (PN) model of general multicluster tools without enumeration of siphon computations or solution of mixed integer programming. A timed PN model is developed for noncyclic operations of dual-armed multicluster tools with a dual ath. The computational results show that the approximately 10% of the total throughput of the proposed method is better than those of the conventional methods. It enables more efficient operations for noncyclic scheduling under transient periods including cleaning operations. [ABSTRACT FROM AUTHOR]

There is growing interest in multifunctional sensors that expand sensing capabilities, especially for environmental measurement needs. This paper aims to develop a multifunctional penta-needle thermo-dielectric sensor (MPTDS) by coupling an electromagnetic (EM) sensor for determining water content with a penta-needle heat pulse probe (PHPP) for determining thermal properties. The thermal properties were inverse fit to the measured temperature rise at four surrounding thermistor needles from an 8-s heat pulse on a central heater needle. The dielectric permittivity was obtained from an impedance measurement made on the heater needle and two adjacent thermistor needles, leading to water content estimates. To determine water content and thermal properties for porous media, a two-step permittivity calibration and an in-situ effective needle spacing calibration were also made. The prototype MPTDS was evaluated in fine quartz sand across a range of water contents from dry to saturated to determine dielectric permittivity, thermal conductivity, and thermal diffusivity, followed by the accurate calculation of water content and soil heat capacity. The limited comparison here demonstrates substantially improved substrate water content determination accuracy from the EM sensor (RSME = 0.012 cm3/cm ^3) when compared with heat-pulse estimates (RSME = 0.042 cm3/cm3). [ABSTRACT FROM PUBLISHER]