半導體晶圓廠零配件庫存決策模式之研究--以某IDM晶圓廠個案公司為例

Abstract

零配件庫存管理為晶圓廠成本控制與生產競爭力之核心關鍵之一，零配件庫存管理不當不僅僅造成庫存金額偏高、資金積壓，而因缺料造成瓶頸機台產能的損失更是驚人。在半導體設備零配件成本高、使用率低、種類繁多、採購時間長短不一的情況下，要降低庫存成本又不致因缺料造成產能損失，如何兼顧兩者一直是各晶圓廠的棘手問題。而多年來，半導體晶圓廠零配件管理實務上卻缺乏一套客觀有系統的運作方式。 除此之外，現行對於半導體零配件庫存管理研究大多只將零配件分為快速流動零配件及慢速零配件兩類來做探討。但是半導體零配件種類繁多，並無法如此單純分兩類管理，因此本研究希望針對現行半導體零配件的特性做更詳細的分類，不同特性的零配件必須運用不同的備料模式。在備料模式的決策上，更須加入生產力、生產瓶頸的直接連結，庫存管理的績效指標改為以生產總成本的損益來作導向，因為畢竟只有瓶頸機台才會造成產能的損失。 本研究除了採取有效的零配件特性分類管理模式來導出正確的備料決策，還提出積極的零配件帳齡管理是有效預防呆滯庫存的關鍵。透過零配件帳齡系統性的解析可以審視變動中的零配件庫存是否健康、合理；除了讓每一項零配件的入庫流程達到應有的控管，再配合積極的呆滯料處理原則，讓庫存品項的資源活化並得到有效的運用。 最後的結論提出供應鏈正確的資訊流才是庫存管理成敗的關鍵。成功的零配件庫存管理需要正確的使用需求資訊，這需要物料管理部門、設備部門與生產管理部門共同以最大產出為績效標準，確認有限的資源必須優先用在整個生產體系的瓶頸上。未來此零配件庫存決策模式在施行上若能配合自動化資訊系統的發展，即可落實為可長可久的執行系統。

In IC manufacturing Fab, the spare parts inventory management plays an important role on operation performance, cost structure, as well as competition strength. The inefficient spare parts inventory management either comes out higher running cost and lower cash flow, or induces huge production loss by the required spare parts shortage. It’s always to be difficult to handle this issue balanced in IC Fab practice. In the previous study on spare parts, it’s normally classified to be just fast moving parts and slow moving parts. There’s no further study to characterize those different application parts in terms of life time, behavior on production tools and connection to the productivity bottleneck. In this case study, the performance index of spare parts inventory management is switched from traditional material control point of view to consolidated Fab overall net productivity result. The balance of reasonable parts inventory cost and minimized production loss is considered. The solid actions to achieve this index are through several effective procedures. They are 1: Monthly review of spare parts inventory idle time and followed by prompt treatment for the slow moving & dead parts. 2: Identify production bottleneck tools and allocate enough spare parts resource to them. Ensure bottleneck tools are protected by right spare parts, and minimize the parts inventory level for non-bottleneck tools. 3: Classify spare parts characteristics and assign proper inventory ways to them. Derive the decision model for go or no-go of safe stock spare parts in IC Fab warehouse. 4: Provide correct information to spare parts vendor to get efficient Supply Chain. Finally, the key success factors for efficient spare parts inventory management are 1: Allocate resources for the bottleneck. 2: Implementation of advanced automation platform with inventoty decision model. 3: Strong execution capability. Based on the developed decision model by the study, after practice performing in this IDM IC Fab, it’s shown the great improvement on spare parts inventory level reduction and the success of productivity ramp up. Contributed by effective spare parts inventory management, the productivity bottleneck can be well protected and the spare parts resource has been utilized much more efficiently than before.