Claude Yugma

A smart sampling algorithm to minimize risk dynamically

In order to maximize the information and thus to minimize risk from measurement and to take into account measurement capacities, an algorithm is proposed to sample lots. An indicator, called Global Sampling Indicator (GSI), has been defined to select the lots to sample, and to schedule them on the measurement tools. A simulator called S5 (Smart Sampling Scheduling and Skipping Simulator) has been implemented and validated on actual data. It shows that the risks can be strongly reduced while keeping a limited number of measures.

A Literature Review on Sampling Techniques in Semiconductor Manufacturing

This paper reviews sampling techniques for inspection in semiconductor manufacturing. We discuss the strengths and weaknesses of techniques developed in the last last 20 years for excursion monitoring (when a process or machine falls out of specifications) and control. Sampling techniques are classified into three main groups: static, adaptive, and dynamic. For each group, a classification is performed per year, approach, and industrial deployment. A comparison between the groups indicates a complementarity strongly linked to the semiconductor environment. Benefits and drawbacks of each group are discussed, showing significant improvements from static to dynamic through adaptive sampling techniques. Dynamic sampling seems to be more appropriate for modern semiconductor plants.

A Batching and Scheduling Algorithm for the Diffusion Area in Semiconductor Manufacturing

This paper proposes an efficient heuristic algorithm for solving a complex batching and scheduling problem in a diffusion area of a semiconductor plant. Diffusion is frequently the bottleneck in the plant and also one of the most complex areas in terms of number of machines, constraints to satisfy and the large number of lots to manage. The purpose of this study is to investigate an approach to group lots in batches and to schedule these batches on machines. The problem is modelled and solved using a disjunctive graph representation. A constructive algorithm is proposed and improvement procedures based on iterative sampling and Simulated Annealing are developed. Computational experiments, carried out on actual industrial problem instances, show the ability of the iterative sampling algorithms to significantly improve the initial solution, and that Simulated Annealing enhances the results. Furthermore, our algorithm compares favourably to an algorithm reported in the literature for a simplified version of our problem. The constructive algorithm has been embedded in software and is currently being used in a semiconductor plant.

Scheduling jobs on parallel machines to minimize a regular step total cost function

This paper deals with a parallel machine scheduling problem whose objective is to minimize a regular step total cost function. A real world application of the problem is presented, and Mixed Integer Linear Programming models are described for the cases with and without release dates, as well as a dedicated constraint generation procedure. Experimental results are reported and discussed to evaluate the relevance of the different approaches on well-known special cases and the general case.

Simulation of a full 300MM semiconductor manufacturing plant with material handling constraints

Generally, simulation models encountered in the literature in the context of semiconductor manufacturing are obtained with many assumptions (aggregations) and from partial model simulation of the facility (also called fab). The results obtained can be satisfactory for certain types of studies but, when precise results and understanding of the detailed behavior of local or global parts of the fab are needed, these simplifications may no longer be adequate. A more detailed model and a full-scale simulation are then needed. This article presents a detailed simulation model of the production system and Automated Material Handling System for a 300 mm semiconductor plant. Some of the studies performed with this model are discussed.

Dynamic management of controls in semiconductor manufacturing

In order to optimize the number of controls in semiconductor manufacturing, a Permanent Index per Context (IPC) has been developed to evaluate in real-time the risk on production tools. Depending on the context which can be defined at tool level, chamber level or recipe level, the IPC allows a very large amount of data to be managed and helps to compute global risk indicators on production. A prototype based on the IPC has been developed and deployed for the CMP workshop. Results show that various indicators can be determined in real time to control risks. The number of measurements without actual added value can be strongly reduced. Moreover, the dispatching of lots on production tools can be improved.

A memetic algorithm to solve an unrelated parallel machine scheduling problem with auxiliary resources in semiconductor manufacturing

In this paper, we propose a metaheuristic for solving an original scheduling problem with auxiliary resources in a photolithography workshop of a semiconductor plant. The photolithography workshop is often a bottleneck, and improving scheduling decisions in this workshop can help to improve indicators of the whole plant. Two optimization criteria are separately considered: the weighted flow time (to minimize) and the number of products that are processed (to maximize). After stating the problem and giving some properties on the solution space, we show how these properties help us to efficiently solve the problem with the proposed memetic algorithm, which has been implemented and tested on large generated instances. Numerical experiments show that good solutions are obtained within a reasonable computational time.

Integration of scheduling and advanced process control in semiconductor manufacturing: review and outlook

Scheduling in semiconductor manufacturing is of vital importance due to the impact on production performance indicators such as equipment utilization, cycle time, and delivery times. With the increasing complexity of semiconductor manufacturing, ever-new products and demanding customers, scheduling plans for efficient production control become crucial. Scheduling and control are mutually dependent as control requires information from scheduling, for example, where jobs are processed, and scheduling requires control information, for example, on which equipment operations can be processed. Based on a survey of the literature, this article proposes a review and an outlook for the potential improvements by binding scheduling decisions and information coming from advanced process control systems in semiconductor manufacturing.

An exact approach for scheduling jobs with regular step cost functions on a single machine

This paper studies a single-machine scheduling problem whose objective is to minimize a regular step total cost function. Lower and upper bounds, obtained from linear and Lagrangian relaxations of different Integer Linear Programming formulations, are compared. A dedicated exact approach is presented, based on a Lagrangian relaxation. It consists of finding a Constrained Shortest Path in a specific graph designed to embed a dominance property. Filtering rules are developed for this approach in order to reduce the size of the graph, and the problem is solved by successively removing infeasible paths from the graph. Numerical experiments are conducted to evaluate the lower and upper bounds. Moreover, the exact approach is compared with a standard solver and a naive branch-and-bound algorithm.

Impact of qualification management on scheduling in semiconductor manufacturing

A qualification management software that proposes recipe qualifications on tools in toolsets for semiconductor manufacturing has been developed. The qualification proposals are based on flexibility measures that have been shown to model capacity allocation in semiconductor workshops. In this paper, qualifications are used in order to see how increased flexibility for the capacity allocation improve scheduling. For this a scheduler simulator for the photolithography area has been used. Tests prove that qualifications - if they are well managed - both enable the simulator to achieve better scheduling and enable toolsets to be less sensitive to tool breakdowns.