Development of capacity indices for semiconductor fabrication

A typical semiconductor fabrication process contains 300 to 1000 steps and its variation depends on the product complexity. Most of the processes are re-entrance to same equipments especially at photolithography, etching, implanter, film deposition, chemical mechanical polishing (CMP) and cleaning. For example, photolithography steps for island, poly, and contact module will be processed at same equipment. Another complication is that the equipment types are different from one to another resulting in different approach for cycle time calculation, difference in availability and efficiency. The objective of this paper is to establish capacity indices to guide for monthly output in semiconductor fabrication facilities. The approach in this paper is using the waterfall chart for individual process and equipment types. Data extraction is being done through reporting systems of Advance Productivity Family (APF), an industrial standard software for data collection that is integrated with individual equipment and product processing historical data. The data was then analyzed using JMP to check for sanity. Results were used to develop capacity indices, which are wafer per hour (wph), manufacturing efficiency, and equipment availability. All these information will be later used to develop the final capacity figure. The final capacity number will then be used to guide the planning team to schedule product combination that will achieve monthly and quarterly wafer shipment goal to customers. This approach reached accuracy of 99% compared to actual throughput. In conclusion, this approach helps the company to provide planning guidelines in meeting the financial goals.