考慮加工時間變異之晶圓製造在製品量訂定模式

摘要

在晶圓製造廠中，於機台前保留適量的在製品，除了可消弭因週期時問過長所帶來的諸多不確定變異外，尙可以之作爲投片及派工的依據。本文探討標準在製品量在晶圓製造廠之重要性，同時以存貨管理中之再訂購點模式爲基礎，提出一個適合晶圓製造廠中， 各機台之標準在製品量的計算模式。本文所提之在製品盘量計算摸式，假設加工時問服從常態分配，適度地將加工時間的變異考慮進去。最後，本文將所求得之在製品量資訊應用至投片及派工上，以驗證此在製品量之有效性，並針對瓶頸機台設計一個以機台之標準在製品量爲參數的派工法則，將園區某晶園廠之實際資料利用模擬方法進行驗證。結果顯示以本法所訂之各機台在製品量進行投片及派工，可提高之系統之平均產出率。同 時也確認本文所提之在製品量估算模式是一有效且快速之求解方法。

Abstract

The standard WIP level in front of equipment in wafer fabrication is an important parameter which can be properly used to diminish system disturbances owing to long cycle time. It can also be used to trigger the decisions of when to release particular wafer lots and how to dispatch them. This paper explores the importance of the role of the standard WIP in wafer fabrication and presents a method, based on the reorder point(ROP) model, to estimate the standard WIP level in front of each equipment with the consideration of processing time variations. A numerical example is provided to elaborate the method. A simulation model of a real-world wafer fabrication factory in Taiwan is built and experimented with the wafer input control rule, Uniform and a dispatching rule for the bottleneck workstation. The results of a single factor experimental design indicate that under the corresponding input control and dispatching rule, the standard WIP level estimated from this study can achieve an ultimate throughput rate. The results also demonstrate that tile ROP-based WIP computing method is a very useful method to determine the standard WIP level in a quick and accurate way.

關鍵詞:

• 標準在製品量
• 再訂購點
• 投片
• 派工

Key Words:

• standard WIP level
• reorder point
• wafer release
• dispatching