控片存貨水準之設定

Abstract

半導體業是台灣的重點工業，而晶圓製造(Wafer Fabrication)更為其中最重要的一環。它具有最複雜的製程技術與製造環境，而控片則是製造時一重要的工具，能有效對晶圓廠作持續的監控與改善。然而傳統的控片存貨水準之設定，由於較無系統化的方法，因而往往造成浮濫及成本上的問題。 由於控片對於製造現場正常晶圓之生產具有嚴重的交互作用與影響性，必須審慎評估。因此，針對計劃的生產目標設定合宜的控片存貨水準是相當重要的。本論文之目的是建構一套系統化的控片存貨水準設定方法，以三階段的方式來達成目標產出下的控片存貨水準設定，並利用一實例進行驗證，試圖找出控片存貨水準與整體產出、週期時間及控片週期時間之間的關係，並提出在控片存貨水準決策上的建議。

Semiconductor manufacturing is one of the focal industries in Taiwan in recent years. Wafer fabrication plays the most important role in semiconductor industry and is perhaps the most technologically complex one in modern manufacturing processes. In wafer fabrication, control wafer is one of important tools for continuously monitoring and improving the performance of the shop floor. However, conventional methods in determining control wafers inventory levels are usually unsystematic, which may result a variety of problems on control wafer management. Because control wafers management has a serious interaction with normal wafer-lot production, control wafers must be appraised cautiously. To determine a suitable inventory level of a specific type of control wafer under a planned throughput target is very important. The objective of this study is to establish a framework to determine appropriate inventory levels for control wafers under a planned throughput target. The proposed methodology is applied to a numerical example. An analysis is made to demonstrate the effectiveness of the proposed framework. The relationships among throughput, cycle time, bottleneck utilization, availability of machines and PUR cycle times of control wafers are also illustrated. Some advices on determining the inventory levels of control wafers are finally suggested.