Semiconductor Fabrication Plant Research Articles

Cement paste column for simultaneous removal of fluoride, phosphate, and nitrate in acidic wastewater

Cement paste, a cured mixture of cement and water, was reported to have considerable capacity for fluoride removal. In this study, heavily mixed fluoric acid wastewater from a semiconductor fabrication plant was applied to a column packed with cement paste granules to evaluate its capacity for the removal of fluoride and three other contaminants, phosphate, nitrate, and sulfate, as well as to investigate the interactions between these contaminants and cement components. The column reduced fluoride to remarkably low levels since fluorite was formed at highly elevated concentrations of calcium and the residual fluoride was further sorbed into the amorphous calcium phosphate that precipitated the entire amount of phosphate until breakthrough. The simultaneous removal of sulfate in the earlier stage was followed by significant removal of nitrate in exchange with the gradual release of sulfate. This behavior was explained by the co-precipitation of sulfate with calcium phosphate or calcium aluminate solids and the subsequent substitution of nitrate for the interlayer sulfate of monosulfate. However, the overall removal capacity of cement paste was reduced due to the high effluent loss of calcium and competition for calcium between fluoride and phosphate.

Evaluating the mid-term competitiveness of a product in a semiconductor fabrication factory with a systematic procedure

Yield is undoubtedly the most critical factor to the competitiveness of a product in a semiconductor fabrication plant. Therefore, evaluating the competitiveness of a product with its yield is a reasonable idea. For this purpose, a systematic procedure is established to evaluate the mid-term competitiveness of a product based on the yield learning model. Further, a new correction function is designed to incorporate expert opinions about the mid-term yield target to main the competitiveness of a product into Chen and Wang’s fuzzy yield learning model. Such expert opinions are very valuable to controlling the yield learning process and have not been considered in traditional models. The modified model ought to be more practical and accurate than the original one. To evaluate the advantages or disadvantages of the proposed methodology, it is applied to the practical data of four products. Experimental results show that the proposed model outperforms the other models by reducing MAPE to only 2%. Besides, as the evaluated competitiveness decreases, the superiority of the proposed model becomes more evident.

Vehicle Clustering Phenomenon in Automatic Materials Handling Systems in 300mm Semiconductor Manufacturing

During design and implementation of the automatic materials handling system (AMHS) for a local 300mm semiconductor wafer fab (semiconductor fabrication plant), we observed and found an interesting phenomenon Vehicle Clustering Phenomenon (VCP) from the dynamics of automated vehicles: As time evolves, the distance between any two adjacent vehicles usually becomes very close enough as if all the vehicles are a long train of vehicles running around the loop. The overall performance thus deteriorates due to this phenomenon. This paper explores the causes of the VCP problem and clarifies its impacts to automatic materials handling operations in 300mm semiconductor manufacturing.

SimPhony — A Voice Communication Tool for Distributed Workgroups

This paper describes SimPhony — a mobile, voice-controlled, voice communication system built on a PDA and designed specifically for distributed workgroups. SimPhony supports one-to-one or one-to-many communication with voice instant messages or synchronous audio transmitted over an IEEE802.11b wireless network, and it transitions between different communication styles as messages become more frequent. The SimPhony interface looks much like an instant messaging client but is accessible through a voice or visual interface on the PDA or a voice interface accessible by any telephone. SimPhony was designed specifically for, and with critique from, technicians working in a large semiconductor fabrication plant.

A fuzzy mid-term single-fab production planning model

Production planning is a complicated task for a semiconductor fabrication plant because of the uncertainties in demand, product prices, cycle times, and product yields. Traditionally, mid-term production planning for a semiconductor fabrication plant is handled with MRP systems or optimized by solving LP or FLP problems. In this study, the philosophy of prioritizing demand classes with higher certainties as proposed by Leachman (1993) is applied to the FLP model of Chen and Wang (1998), and a new FLP model for planning the mid-term production of single wafer fabrication plant is constructed. Parameters in this model are given in the form of trapezoidal fuzzy numbers. Fuzzy comparison is adopted in dealing with the fuzzy objective function and expanding inequalities. The outputs are projected using Chen and Wang's fuzzy dynamic production function. The uncertain demand is classified and satisfied with four successively optimized FLP submodels according to their ascending uncertainties. Chen and Wang's example is adopted to demonstrate the proposed methodology and to make some comparisons. By moving more capacity to demand classes with higher certainties that are usually nearer and have larger discounted revenues, the proposed methodology achieves a higher value of the discounted cash flows than the two referenced models.

Participative management: an empirical study of the semiconductor manufacturing industry

In order to stay competitive, semiconductor fabrication plants (fabs) must increase throughput and lower costs. At the same time, processes are becoming more complex with shorter life cycles. In this environment, some fabs are turning to their workforce for the added capacity, flexibility, and speed. This paper examines the effect of participative management techniques on manufacturing performance. Analyzing an international sample of 15 fabrication plants, the authors show that participative management has a statistically significant and positive correlation with manufacturing quality and a positive, but not statistically significant, correlation with quantity. The analysis also shows that the fabs in their sample tend to drive the individual components of participative management-power, information, rewards and knowledge-to the lowest level of the organization in a congruent fashion. This suggests that those fabs that utilize participative techniques do so efficiently.

Temperature measurement of wafers with varying multilayer structures during rapid thermal annealing

Rapid thermal processing for advanced semiconductor production demands improved temperature and uniformity control because the optical properties of the dielectric layers deposited on the wafer front- and backside strongly influence the temperature measurement. The measurement of temperature gets more and more important because the semiconductor fabs do not stay with only one product. In recent years, the diversity in product and technology has increased within many semiconductor fabrication plants. As a result, there can be large differences in substrate film stacks between wafers for any rapid thermal annealing step. This variety in products and consequently the differences in emissivity have to be controlled with a precise, simple temperature measurement. One possible solution is the PinTC/sup TM/ presented here. This is a low-cost, thermocouple-based alternative to classical pyrometric temperature measurement and works in closed-loop control. The PinTC/sup TM/ is in contact with the wafer backside and almost emissivity independent. It was found that the optical properties of the wafer backside influence the temperature slightly. To show the improvement in temperature measurement this technology is compared to open-loop processing on wafers with different layer stacks on the backside. The absorptivity of the coatings dominate the direct contact measurement. For the various backside coatings power absorption by the wafer element per unit time and emissivity calculations are performed to understand and explain the experiments. Nevertheless, this direct contact temperature measurement technology is reliable for wafer production in closed-loop control or as a secondary temperature monitor. Furthermore, the PinTC/sup TM/ offers good repeatability in the production environment.

Solving two application problems

In this article application stories illustrate two rather uncommon network remodelings—one for a semiconductor fabrication plant, the other for a supermarket—in which recently developed hardware is applied to redesign and optimize the networks. © 1997 John Wiley & Sons, Ltd.

Scheduling and simulated annealing application to a semiconductor circuit fabrication plant

This paper addresses the scheduling problem of the input order of multiproduct batch processing systems. This type of plant configuration is typically used in the production of paints, medicines, cosmetics, electronics componants, etc. In a general way, the scheduling problem of large multiproduct batch plants (MPBP) cannot be solved exactly because its dimension is very high (problem NP-complete). An optimization technique called Simulated Annealing (SA) has already been successfully used to solve several large combinatorial problems ( for example, travelling salesman), and so we have implemented a SA methodology for determining the input order of a given set of products so as to minimize the average residence time of these products in the plant with unlimited intermediate storage (UIS) policy. The discrete simulation program developped in a previous part of this study is used to determine the value of the objective function. The proposed technique is applied to a real world problem - a semiconductor circuit fabrication plant of MOTOROLA Inc. (Toulouse) -.

Scheduling and simulated annealing application to a semiconductor circuit fabrication plant

Scheduling and simulated annealing application to a semiconductor circuit fabrication plant