具有多品种晶圆混合加工的单臂组合设备调度

为了提高晶圆制造中组合设备的生产效率,在考虑晶圆驻留时间约束条件下,研究没有共享加工模块的多品种晶圆混合加工的单臂组合设备调度问题.首先,采用面向资源的Petri网模型描述多种晶圆产品的混合加工过程,引入控制变迁避免模型的死锁,采用赋时库所和赋时变迁模拟系统资源的活动时间.其次,通过虚拟加工的方法平衡工序的负载,基于系统Petri网模型和拉式调度策略,推导出单臂组合设备在多品种晶圆混合加工情形下的可调度性判定条件,并以解析形式描述.最后,提出了系统稳态调度求解算法并以实例验证了算法的有效性和可行性.     

面向单臂组合设备中紧急订单的调度

随着晶圆制造模式向多品种、小批量的转变，在实际生产过程中频繁出现紧急订单插入的情况，不合理的调度策略将降低组合设备生产效率。为了提高组合设备的生产柔性，研究了在考虑晶圆逗留时间约束条件下，单臂组合设备面对紧急插单时的调度问题。首先，对紧急插单的加工过程进行分析，提出针对单臂组合设备的机械手调度规则，实现了加工过程的可调度性。其次，对于因加工参数不同产生的两种加工状态，分别推导出可调度性判断条件，然后给出用于求解机械手等待时间的数学解析式。最后，提出组合设备面对紧急插单时的最优调度算法，并通过实例验证和对比分析的方法验证了该调度方法的有效性。     

腔室清洗的单臂组合设备初始暂态调度

为了提升腔室洁净度,晶圆厂需对组合设备腔室进行清洗操作,从而提高晶圆的加工质量.考虑腔室清洗时间和晶圆驻留时间的约束条件下,本文研究了单臂组合设备的初始暂态调度问题.首先,提出了机械手的初始暂态活动规则,并对机械手活动序列进行描述,实现了系统的初始暂态可调度性;其次,对机械手在初始暂态和稳态的活动时间进行了建模;然后,根据系统的时间特性,建立了初始暂态调度的线性规划模型;最后,通过实例验证了该方法的有效性.与已有的虚拟晶圆方法相比,该调度方法能有效减少初始暂态的完工时间,提高了组合设备的晶圆生产效率.     

具有清洗工艺的单臂组合设备终止暂态调度

随着多品种小批量生产模式的普及,导致了组合设备频繁的暂态加工过程.为了提高组合设备的生产柔性,同时考虑晶圆驻留时间约束和腔室清洗时间约束,研究了单臂组合设备的终止暂态调度问题.首先,提出了 1-周期清洗工艺的暂态调度规则,并采用了面向资源的Petri网对单臂组合设备的终止暂态过程进行建模,引入避免死锁的变迁触发规则;其次,根据系统的终止暂态时间特性并考虑不同的调度情形,建立了终止暂态调度的线性规划模型;最后,通过实例验证了该方法的可行性.实验结果表明,与运用改进拉式策略的虚拟晶圆方案相比,该调度方案可有效地减少组合设备终止暂态的完工时间,并满足晶圆制造的工艺要求.     

基于Petri网的组合设备建模与调度综述

组合设备是半导体晶圆制造的核心装备,其调度与控制优化是半导体制造领域极具挑战性的课题. Petri网因其强大的建模能力和简约的图形化表达优势,被广泛地应用于组合设备的建模与调度.对基于Petri网的组合设备建模与调度方法进行综述,归纳总结了组合设备的结构类型、晶圆流模式、调度策略及Petri网建模方法,并系统阐述组合设备的7类典型调度问题,包括驻留时间约束、作业时间波动、晶圆重入加工、多品种晶圆加工、加工模块(Process module, PM)故障、PM清洗和组合设备群.最后,讨论了当前组合设备调度存在的挑战及后续可能的研究方向.     

基于时间约束集的集束型设备群调度方法

随着300mm晶圆的加工技术问世,工业界开始采用一种全新的晶圆制造设备——集束型设备群(Multi-cluster tools).对于单个集束型设备(Single-cluster tools)调度研究已比较成熟,并提出了多种调度方法,然而对于集束型设备群调度研究尚处在一个起步阶段. 本文对带有驻留约束且具有多种晶圆类型的集束型设备群的调度问题进行了研究,在引入时间约束集概念的基础上建立了调度模型, 同时,提出了一种逐级回溯的调度方法,并对调度算法进行了仿真实验分析. 仿真结果表明本文提出的算法是有效且可行的.     

晶圆重入加工的组合设备终止暂态的调度与分析

晶圆重入是半导体组合设备加工中典型的复杂加工工艺,分析和优化暂态加工过程对于晶圆重入加工具有重要意义.为了满足加工需求和提高组合设备的加工性能,基于稳态重入加工的双臂组合设备Petri网模型和1-晶圆周期调度策略,采用虚拟晶圆的加工模式分析了系统的终止暂态过程,讨论了系统终止暂态的加工时间分布,并给出相应的解析式进行描述.利用eM-Plant仿真平台建立了重入加工的双臂组合设备终止暂态的仿真模型,并用例子验证了1-晶圆周期调度的可行性及解析式的有效性,为研究晶圆重入加工过程的优化提供了有效方法和手段.     

基于调度长路径的复杂产品综合调度算法

针对目前复杂产品加工和装配综合调度算法中考虑纵横双向调度优化时以横向为主,而忽略产品工序内在纵向约束对制造效率产生主要影响的问题,提出了以关键路径为主的纵横双向调度优化算法——基于调度长路径的复杂产品调度算法。该算法考虑了复杂产品树状工艺结构,根据优先级策略并结合调度长路径和长用时等策略来确定工序的调度次序。采用优先级策略可以兼顾其他分支上的同层工序;采用调度长路径策略是在兼顾其他分支的同时优先考虑了关键路径上工序对总加工时间的影响;采用长用时策略可以优先调度对加工时间影响大的工序。对已定调度次序的工序采用工序尽早加工的原则确定开始加工时间。实例表明,提出的调度策略简便可行且调度结果更优。     

可动态生成具有优先级工序集的动态Job-Shop调度算法

为了在满足约束条件的前提下使不同时刻加入到作业集合中的全部作业所用的加工总时间尽可能地少,提出算法:根据动态的作业集合构造虚拟加工树,虚拟加工树上的叶结点代表最先加工的工序,虚拟根节点代表最后一道工序,边代表偏序关系;以层优先为虚拟加工树上的工序设置优先级,工序的优先级可作为调度过程中考虑的一个因素;除了在工序需要动态调整的情况下,在调度过程中始终遵循着机器忙原则.在调度过程中,首先根据虚拟加工树动态地生成备选工序集合,然后根据工序的优先级并且结合其它的调度策略从备选集合中调度工序,直到备选集合为空,即所有作业加工完毕.这里提到的调度策略包括短用时策略、长路径策略和动态调整策略.通过实例验证,该算法对于动态Job-Shop问题可以获得比较好的解.     

实时控制系统中固定优先级调度的延迟与抖动控制

在基于固定优先级调度实时控制系统中,任务的延迟与抖动是影响系统稳定性的重要因素,提出一种基于可抢占时间阈值的延迟与抖动控制策略,给出一种保证系统可调度的最优闽值分配算法,并通过对任务延迟和抖动的分析量化出阀值分配后的争最大可能IO延迟及抖动.最后通过仿真实验验证了该策略的有效性.     

Post-Processing Time-Aware Optimal Scheduling of Single Robotic Cluster Tools

Integrated circuit chips are produced on silicon wafers. Robotic cluster tools are widely used since they provide a reconfigurable and efficient environment for most wafer fabrication processes. Recent advances in new semiconductor materials bring about new functionality for integrated circuits. After a wafer is processed in a processing chamber, the wafer should be removed from there as fast as possible to guarantee its high-quality integrated circuits. Meanwhile, maximization of the throughput of robotic cluster tools is desired. This work aims to perform post-processing time-aware scheduling for such tools subject to wafer residency time constraints. To do so, closed-form expression algorithms are derived to compute robot waiting time accurately upon the analysis of particular events of robot waiting for single-arm cluster tools. Examples are given to show the application and effectiveness of the proposed algorithms.      

Optimal Integrated Schedule of Entire Process of Dual-blade Multi-cluster Tools From Start-up to Close-down

Multi-cluster tools are widely used in majority of wafer fabrication processes in semiconductor industry. Smaller lot production, thinner circuit width in wafers, larger wafer size, and maintenance have resulted in a large quantity of their start-up and close-down transient periods. Yet, most of existing efforts have been concentrated on scheduling their steady states. Different from such efforts, this work schedules their transient and steady-state periods subject to wafer residency constraints. It gives the schedulability conditions for the steady-state scheduling of dual-blade robotic multi-cluster tools and a corresponding algorithm for finding an optimal schedule. Based on the robot synchronization conditions, a linear program is proposed to figure out an optimal schedule for a start-up period, which ensures a tool to enter the desired optimal steady state. Another linear program is proposed to find an optimal schedule for a close-down period that evolves from the steady state period. Finally, industrial cases are presented to illustrate how the provided method outperforms the existing approach in terms of system throughput improvement.      

Scheduling Dual-Arm Cluster Tools With Multiple Wafer Types and Residency Time Constraints

Accompanying the unceasing progress of integrated circuit manufacturing technology, the mainstream production mode of current semiconductor wafer fabrication is featured with multi-variety, small batch, and individual customization, which poses a huge challenge to the scheduling of cluster tools with single-wafer-type fabrication. Concurrent processing multiple wafer types in cluster tools, as a novel production pattern, has drawn increasing attention from industry to academia, whereas the corresponding research remains insufficient. This paper investigates the scheduling problems of dual-arm cluster tools with multiple wafer types and residency time constraints. To pursue an easy-to-implement cyclic operation under diverse flow patterns,we develop a novel robot activity strategy called multiplex swap sequence. In the light of the virtual module technology, the workloads that stem from bottleneck process steps and asymmetrical process configuration are balanced satisfactorily. Moreover, several sufficient and necessary conditions with closed-form expressions are obtained for checking the system's schedulability. Finally, efficient algorithms with polynomial complexity are developed to find the periodic scheduling, and its practicability and availability are demonstrated by the offered illustrative examples.     

Cycle time analysis of dual-arm cluster tools for wafer fabrication processes with multiple wafer revisiting times

For some wafer fabrication processes, the wafers need to visit some processing modules for a number of times, which is referred to as the revisiting process. With wafer revisiting, it is very complicated to analyze the cycle time of a dual-arm cluster tool. Due to the fact that atomic layer deposition (ALD) process is a typical revisiting process in the semiconductor industry, study is conducted on cycle time analysis of dual-arm cluster tools for the ALD process with multiple revisiting times. The system is modeled by a type of Petri net. With this model, it is revealed that the system may never reach a steady state. Based on this finding, a method is presented to analyze the cycle time and analytical expressions are derived to calculate the cycle time for different cases. Several illustrative examples are given to show the applications of the proposed approach.     

基于eM-Plant的虚拟晶圆制造自动组合装置

针对难以用解析法验证半导体加工装置的调度可行性问题,提出仿真建模研究的新方法。利用仿真软件eM-Plant建立晶圆制造中单臂自动组合装置的参数化仿真模型,构建一个虚拟的晶圆制造系统。该系统为研究自动组合装置控制问题提供有效手段,是验证半导体制造生产调度可行性的仿真平台。     

Schedulability Analysis of Time-Constrained Cluster Tools With Bounded Time Variation by an Extended Petri Net

Cluster tools for some wafer fabrication processes such as low-pressure chemical vapor deposition have strict wafer delay constraints. A wafer that completes processing in a processing chamber should leave the chamber within a specified time limit. Otherwise, the wafer suffers from severe quality troubles due to residual gases and heat within the chamber. An important engineering problem is to verify whether for given task times there exists a tool operation schedule that satisfies the wafer delay limit. There have been studies on the problem, which all assume deterministic task times. However, in reality, the task times are subject to random variation. In this paper, we develop a systematic method of determining schedulability of time-constrained decision-free discrete-event systems, where time variation can be confined within finite intervals. To do this, we propose an extended Petri net for modeling such systems. We then develop a necessary and sufficient condition for which there always exists a feasible schedule and one for which there never exists any feasible schedule. We develop a graph-based computational procedure for verifying the schedulability conditions and determining the worst-case task delay. We demonstrate how the procedure can be used for cluster tool engineering to control wafer delays against wafer alignment failures and time variation.      

Scheduling cluster tools in wafer fabrication using candidate list and simulated annealing

This paper presents a new method for scheduling cluster tools in semiconductor fabrication. A cluster tool consists of a group of single-wafer chambers organized around a wafer transport device, or robot. Cluster fabrication system considered in this paper consists of serial cluster tools. Due to constraints imposed by multiple routes of each wafer type and machines with no buffer, it is difficult to find an optimal or near-optimal schedule. In order to determine the sequence of the operations to be released and the assignment of the machine to each operation, the proposed method uses a job requirement table with random keys as a solution representation. Simulated annealing seeks the optimal or near-optimal sequence and machine assignment of the operations. In this paper, the scheduling objective is to find a schedule with minimum makespan. A Gantt chart is obtained as the final schedule. To handle the constraints, the proposed method uses a candidate list. To determine which operation can be scheduled in considering the constraints, a negotiation procedure between the operations in the candidate list and a current state of the system is introduced. To show the effectiveness of the proposed method, scheduling example of a real cluster fabrication system is presented. Scheduling results are compared with those obtained by using several dispatching rules. From the experimental results, it is shown that the proposed method is promising.