SCHEDULING WAFER FABRICATION OPERATIONS: STATE-OF-THE-PRACTICE AND FUTURE NEEDS

John Fowler and Michele Pfund Arizona State University, Tempe, USA

Abstract: In this presentation, we provide an overview of the challenges in scheduling wafer fabrication operations, present the current state-of-the-practice, and discuss the needs that are not currently being met by today’s practice. The material in this presentation is based on the results of a survey conducted of major semiconductor manufacturing companies.

Key words: Semiconductor Manufacturing, Wafer Fabrication, Scheduling, Dispatching.

1. OVERVIEW

In order to understand the tools that are currently being utilized in semiconductor wafer fabrication facilities, a survey instrument was created and sent to major semiconductor manufacturing companies. The survey was designed to ask specific questions regarding the types of scheduling methodologies currently implemented, the limitations of these methodologies, and the needs for future generation scheduling systems. In total, 16 respondents from 14 companies participated in this survey, representing fabs from Europe, Asia, and North America. From this report, we have found that many dispatching systems are in place and are mature installations (install time greater than 5 years). These systems have been considered to be only “satisfactory” in that benefits are being received, but the majority of respondents believe that more benefits are possible. Specifically, respondents indicated that better scheduling / dispatching rules, test environments, and reporting tools are needed. Compared to the 1994 SEMATECH Measurement and Improvement of Manufacturing Capacity (MIMAC) survey and interview results, cycle time and on-time delivery have gained significant importance in the fab. Respondents indicated that these performance metrics are most impacted by a bottleneck machine breakdown and jobs going on hold (for process reasons), which were also the two most frequently occurring events as indicated by respondents. Thus, scheduling/rescheduling methodologies that incorporate these events are needed.

392

With regard to the frequency of rescheduling, respondents had mixed opinions. While most respondents favored rescheduling either at every shift or within a shift, many cited management challenges (operator stability/morale, staging for setup) as well as technical challenges such as hardware support. However, over 35% of respondents would like to reschedule after every job movement.

393