Optimal scheduling techniques for cluster tools with process-module and transport-module residency constraints

Rostami, Salim; Hamidzadeh, Babak

doi:10.1109/robot.2001.933131

Cited by 13 publications

(15 citation statements)

References 10 publications

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“…There have been many studies on scheduling cluster tools or robotised systems assuming cyclic schedules (Sethi, Sidney, and Sriskandarajah 2001;Shin, Sidney, and Sriskandarajah 2001;Lee, Lee, and Shin 2004;Lee, Lee, and Lee 2007;Paek and Lee 2008;Yi et al 2008;Shafiei-Mondared, Salehi-Gilani, and Jenab 2009;Che et al 2010;Lati and Gilad 2010;Yan et al 2010;Chan, Yi , and Ding 2011;Kim, Jung, and Lee 2011;Kujawski and Światek 2011;Zahrouni and Kamoun 2012). Some studies analyse the schedulability issues when time window constraints or activity time variations in processing times occur (Rostami, Hamidzadeh, and Camporese 2001;Rostami and Hamidzadeh 2002;Kim et al 2003;Zhou 2010, 2012;Che et al 2011). In addition to studies on cluster tools, there have been works on robotic cells that are logically similar to cluster tools.…”

Section: Introductionmentioning

confidence: 99%

Scheduling dual-armed cluster tools with cleaning processes

Kim

Lee

et al. 2013

International Journal of Production Research

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Modern cluster tools tend to clean the chambers each time a specified number of wafers have been processed. Such cleaning processes are intended to reduce the quality risk due to the residual chemicals within the chambers. When such cleaning processes are introduced, the conventional scheduling methods for cluster tools, such as the swap sequence for dual-armed cluster tools, are no longer effective. Therefore, we examine a cyclic scheduling problem for a dual-armed cluster tool that performs cleaning processes periodically. We first identify sufficient conditions for which the conventional backward and swap sequences give the minimum cycle time. We then develop a systematic way of generating all feasible robot task sequences, for which the cycle times can be computed. However, the number of feasible robot task sequences increases too fast to be enumerated as the cleaning cycle and the number of process steps increase. To address the complexity problem, we propose two heuristic scheduling strategies and compare them with the conventional scheduling methods and the lower bound of each schedule, respectively, to verify their effectiveness experimentally. IntroductionCluster tools are widely used for most semiconductor fabrication processes, such as lithography, etching, and deposition. Cluster tools consist of several processing modules (PMs), a wafer-handling robot, and loadlocks. They have various architectures depending on the configuration of the PMs and the number of robot arms. Figure 1(a) illustrates a radial cluster tool with four PMs and a dual-armed robot. Each PM has a chamber in which wafers are processed, and PM i indicates the PM corresponding to the i th process step. When a cassette containing identical wafers arrives at the loadlock, the robot unloads a wafer and transports it to the first processing chamber according to its recipe.In a one-unit cyclic schedule, each time the robot completes a predefined sequence, one wafer finishes all processes and returns to the loadlock. For example, when each PM in the tool of Figure 1(a) is filled with a wafer, if the robot unloads a wafer from PM 4 , transports it, and loads it into the loadlock, one wafer completes its processing in the tool. Then, if the robot repeats the same operation to the wafers in PM 3 , PM 2 , PM 1 , and the loadlock in sequence, all PMs again have a new wafer and the robot finishes all tasks in a cycle. When the robot loads or unloads a wafer at a PM, the next robot task should be determined depending on the tool state and the number of available robot arms. For example, if the robot is holding two wafers, it should load one of the two wafers into a PM, and if it has one empty arm, it can unload a wafer as the next task.To improve the quality of the wafers, it is very important to clean the processing chambers periodically because, each time they process wafers, residual chemicals remain on the internal surface of the chamber wall, and the residues can contaminate wafers. Such chamber cleaning is used for all chemical vapour deposi...

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Section: Introductionmentioning

confidence: 99%

Scheduling dual-armed cluster tools with cleaning processes

Kim

Lee

et al. 2013

International Journal of Production Research

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“…Examples of studies of cluster tools with dual-armed robots include Kim et al [42], Rostami et al [53], Rostami and Hamidzadeh [54], Shin et al [57], and Venkatesh et al [61]. In these tools, the robot's two arms extend from the central robot in diametrically opposed directions.…”

Section: Introductionmentioning

confidence: 99%

Productivity Improvement From Using Machine Buffers in Dual-Gripper Cluster Tools

Geismar

Dawande

Sriskandarajah

2011

IEEE Trans. Automat. Sci. Eng.

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Cluster tools (also referred to as robotic cells) are extensively used in semiconductor wafer fabrication. We consider the problem of scheduling operations in an -machine cluster tool that produces identical parts (wafers). Each machine is equipped with a unit-capacity input buffer and a unit-capacity output buffer. The machines and buffers are served by a dual-gripper robot. Each wafer is processed on each of the machines, and the objective is to find a cyclic sequence of robot moves that minimizes the long-run average time to produce a part or, equivalently, maximizes the throughput.We first obtain a tight upper bound on the optimal throughput and then use this bound to obtain an asymptotically optimal sequence under conditions that are common in practice. Next, we quantify the improvement in productivity that can be realized from the use of unit-capacity input and output buffers at the machines. Finally, we illustrate our analysis on cluster tools with realistic parameters, based on our work with a Dallas-based semiconductor equipment manufacturer.Note to Practitioners-Semiconductor manufacturers often seek methods to increase the productivity of their cluster tools. This paper considers the option of adding single-unit-capacity input and output buffers at each processing chamber of a cluster tool with a dual gripper robot. We demonstrate that this is an effective approach for tools that are transport-bound, i.e., those in which the robot is the bottleneck resource. We also present a sequence of robot movements that provides the optimum throughput for such a tool. The use of these internal buffers is not beneficial for tools that are process-bound, i.e., those in which a processing chamber is the bottleneck.

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“…The former means that the processing time on each machine is exactly a given constant time, while in the latter the processing time should be within a given time window. The processing time windows are more common in practical automated manufacturing environments and are also called flexible processing times (Paul et al 2007) or residency constraints (Rostami and Hamidzadeh 2002) in different practical background. Additionally, there is no buffer between the machines and any delay on the machines or on the robot will impact the quality of the parts.…”

Section: Introductionmentioning

confidence: 99%

“…Note that a similar robotic scheduling problem also exists in more general manufacturing cells where the parts are not only allowed to wait on the machine but also allowed to wait on a robot for finite or infinite time upon completion of their processing International Journal of Production Research 6463 (see Sethi et al 1992, Ioachim and Soumis 1995, Crama and van de Klundert 1997, Sriskandarajah et al 1998, Kamoun et al 1999, Rostami et al 2001, Rostami and Hamidzadeh 2002, Kim et al 2003, Lee and Park 2005, Kim and Lee 2008, Wu and Zhou 2009. Detailed description and classification of robotic cells scheduling problem can be found in (Crama et al 2000.…”

Section: Introductionmentioning

confidence: 99%

A branch and bound algorithm for optimal cyclic scheduling in a robotic cell with processing time windows

Yan

Chen

Yang

et al. 2009

International Journal of Production Research

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A branch and bound algorithm is described for optimal cyclic scheduling in a robotic cell with processing time windows. The objective is to minimise the cycle time by determining the exact processing time on each machine which is limited within a time window. The problem is formulated as a set of prohibited intervals of the cycle time, which is usually applied in the robotic cyclic scheduling problem with fixed processing times. Since both bounds of these prohibited intervals are linear expressions of the processing times, we divide these prohibited intervals into a series of the subsets and transform the problem into enumerating the nonprohibited intervals of cycle time in each subset. This enumeration procedure is completed by an efficient branch and bound algorithm, which could find an optimal solution by enumerating partial non-prohibited intervals. Computational results on the benchmark instances and randomly generated test instances indicate that the algorithm is effective.

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Optimal scheduling techniques for cluster tools with process-module and transport-module residency constraints

Cited by 13 publications

References 10 publications

Scheduling dual-armed cluster tools with cleaning processes

Scheduling dual-armed cluster tools with cleaning processes

Productivity Improvement From Using Machine Buffers in Dual-Gripper Cluster Tools

A branch and bound algorithm for optimal cyclic scheduling in a robotic cell with processing time windows

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