News Article

GCTC Gains The Benefits Of Careful Fab Management

The manufacturing of GaAs ICs is a high-volume business, and as such is subject to the same production management techniques used in other industries. Roger Yin and colleagues describe the successful implementation of the KMTI model at GCTC.
Increasing competition in the GaAs industry is forcing manufacturers to consider and implement a total solution in GaAs fab management. Since controlling all of the activities of a fabrication line in the presence of a lengthy qualification process is a requirement, a well-executed fab management plan can result in a faster cycle time, accelerated production ramp and yield enhancement. However, to our knowledge, there is no formal strategy that is being advocated for GaAs foundry operations. Leveraging the silicon foundry experience in Taiwan, Global Communications Technology Corporation (GCTC), a provider of GaAs MMIC foundry services based in Taiwan, has successfully implemented an innovative approach for managing its manufacturing facilities. This approach is based on the knowledge, multi-skill, teamwork and innovation (or KMTI) model, and it has yielded some very encouraging results.

The model addresses five key elements: human resource management, machine utilization, dispatching methodology, epitaxial wafer inventory and organization structure, all of which can be represented using a star as shown in figure 1.

Human resource management

To achieve the optimal utilization of human capital, the total workforce in the fab line must be considered. Cross training of staff members is executed within the fab. This broadens the experience base of the operating staff, and creates what are known as responsible account engineers, who play a role similar to that of a project manager. The fact that people have widely differing work skills and habits has necessitated the evaluation of individual performance from the standpoint of his or her ability, and also on his or her motivation. We have created some new training and incentive programs such as personal growth, on-the-spot cash rewards and a listening center, in addition to the more traditional incentives such as stock options and year-end bonuses. These help to stabilize the labor force and encourage extra efforts from each individual. We have also established better communication channels at various levels to provide improved face-to-face communication for employees. This has resulted in greatly improved problem solving and goal achievement with greater efficiency.

Since implementing this approach, GCTC has seen a significant drop in its staff turnover rate, from 15% before implementation to 7% afterwards. Productivity has also increased and fab staff report enhanced job satisfaction. Staff turnover is an important consideration because of the demands for operating stability, the extended qualification periods with customers and the hands-on nature of processing even for those steps with highly automated equipment sets.

When recruiting new employees, personality as well as interests and capabilities are evaluated in an effort to place new staff members in a position that is challenging and interesting, and considers their skills and physical and mental strengths.

Machine utilization

A process variability management system has been introduced that is designed to identify and reduce local variability and improve productivity at process bottlenecks. Since the variability can be additive and can migrate from one operation to another, the root causes are determined by correlating any variability to potential sources. In particular, variability has a detrimental effect on the process bottlenecks.

The management of process tool set-up time is a good example of where process variability monitoring is important. The goal of set-up time management is to achieve the production of small lots of products with high efficiency, by increasing the equipment flexibility and optimizing the set-up procedures. The success of this process depends directly on the ability to perform equipment set-ups in a minimum amount of time, and also requires well-organized spare-parts management. Moreover, preventative maintenance is monitored and controlled by automatic systems. These systems remind operators when preventive maintenance should be done, and constrain the release of the machines following maintenance, ensuring that the proper release procedure is used. Various sets of rules have been established, as well as guidelines to ensure that machines are properly qualified after preventive maintenance. These prevent production under abnormal conditions that would lead to variation in the process.

Through set-up time management, a number of unnecessary or non-essential activities have been eliminated during machine set-up and maintenance. This has resulted in a 40% cycle-time reduction and a corresponding increased machine utilization rate.

Dispatching methodology

Implementing a work in process (WIP) diagnosis system enables a WIP profile to be built up to predict when lots will be completed and where any process bottlenecks occur, or identify batching points where process loads will place a heavy demand on a tool set for a short period of time. At GCTC, a dispatching methodology has been implemented that groups together lots at various batching points to more efficiently consume high-cost materials. Lot priority setting is automatically adjusted according to the delivery date or the customer s request. All lots processed in the GCTC fab line are dispatched in compliance with a manufacturing execution system that tracks all activities and resources through the production process to realize on-time (or early) delivery.

Good epitaxial wafer inventory management is essential to the successful operation of a GaAs fab because of the high cost of the starting materials. Inadequate control of the wafer inventory can result in both understocking and overstocking of these materials. Understocking results in missed deliveries, lost sales and dissatisfied customers. On the other hand, overstocking unnecessarily ties up capital that might be used more productively elsewhere.

At GCTC, wafer-inventory management addresses two main concerns, which are the level of customer service and the cost of carrying inventory. The system in use tracks the additions and removals from the inventory stocks and provides the current status in real time. When the epiwafer inventory reaches a predetermined minimum, a request for a reorder is then generated. The required amount in the reorder is determined by an economic order quantity model, which arrives at the optimal order quantity by considering delivery schedules and by minimizing the sum of certain costs that vary with order size (Stevenson).

Organization structure

From the outset, the organization structure at GCTC was designed to be simple, with a low degree of departmentalization and wide spans of control. The strength of the structure lies in its simplicity. It provides fast responses, flexibility and clear accountability. This structure is clearly advantageous in the early stages of a GaAs enterprise. Now that products have been qualified and operations stabilized, the company has gradually migrated to a matrix management structure.

This approach has its strength in grouping similar specialists together. It facilitates the efficient allocation of specialists without the drawbacks of the traditional functional organization, where individuals with highly specialized skills are lodged in one functional department or product group for a long time. The matrix management approach has the advantages of economies of scale by providing the organization with both the best resources and an effective way of ensuring their efficient deployment (Robbins). With a direct labor force, GCTC has adopted seven day/24 hour working across four shifts, allowing for flexibility in scheduling staff and providing a responsive service for customers.

The results of successful KMTI

The trend in recent years has been towards a knowledge-based economy. GCTC is no exception to this concept, as evidenced by the implementation of the KMTI model to reduce costs, speed up lot processing, increase flexibility, get closer to customers and empower employees. The performance of GCTC s operation following the KMTI implementation has been monitored by reporting systems to aid in making continuous improvements. The approach is result oriented, focuses on management by objectives, and organization performance is evaluated by indices and baseline experiences. Our implementation has resulted in a stable, highly motivated workforce, with increased productivity and very competitive services and products in the marketplace.

Further readingW Stevenson 2001 Production Operation Management (Irwin McGraw-Hill).
S Robbins 2001 Essentials of Organizational Behavior (Prentice Hall).

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