晶圓製造成本估算模式之建置 - 以某晶圓代工廠為例

A cost estimation model development for wafer manufacturing cost - using a wafer foundry Fab as example

陳士文(Shih-Wen Chen)

指導教授 ： 劉志明

國立清華大學/工學院/工業工程與工程管理學系碩士在職專班/碩士(2008年)

摘要

摘要

晶圓代工的製程複雜，產品製造流程高達數百個步驟，執行特定製程功能的機器群達數十種，而使用的物料繁多，包括化學品、特殊氣體、石英、零件、耗材等，這些因素增加了估計晶圓製造成本的困難性。

本論文針對晶圓製造成本，參考作業基礎成本制的兩階段架構，運用成本分配原則，以直接歸屬的成本優先考慮，具因果關係的分攤次之，最後考慮量的分攤的核心觀念，建立不同層級的作業，包括機器中心層級的機器作業、部門層級的工程作業與製造作業，以及與全廠層級的支援作業，用以將全廠資源透過不同層級的作業，將成本分配至產品的加工站點。本模式主要採用作業時間為成本分攤因子，驗證模式的可行性。

本研究有下列幾點結論：(1)本研究所計算的產品成本可反應產品在生產途程的複雜性 (2)產品於工廠使用的資源可能差異性很大，採用平均每站成本與平均每光罩層成本的簡單估計，可能造成很大誤差(3)本研究的模式可經修改而適用於採分步成本制的標準成本建立(4)本研究發現在晶圓製造中有許多物料可不需透過複雜工程資料而可估得該物料於加工站點的物料成本。有些物料僅用於單一機器群，這些都是監控單位用量成本的適合對象。(5) 成本習性分析發現大致只有在有物料與零件偏變動成本的性質，其餘的成本大致有經常性支出的特性，這兩類成本是成本改善的重點。

關鍵詞：晶圓製造成本、成本估計、作業基礎成本制

關鍵字

晶圓製造成本 ； 成本估計 ； 作業基礎成本制

並列摘要

Abstract

The process of semiconductor manufacturing is complex. There are hundreds of operation steps to complete a product and there involve various materials and machine groups during the process. The complexity of manufacturing process and manufacturing resources make the cost estimation difficult.

This research presents a manufacturing cost estimation model which uses two-stage allocation structure and considers the preferential sequence for cost assignment to establish 3 levels of activities including machine center activity, production/engineering activity, and supporting activity. The manufacturing resources can be properly allocated to operation steps through the activities. This research uses process time as the main allocation factor to simplify the calculation.

The cost estimation result from proposed model has the conclusions (1) the cost estimation can reflect the process complexity of products (2) the resources consumes by products varies, there may have significant estimation bias based on a simplied estimation such as per layer cost or per move cost basis (3) the cost estimation model may be modified for generating standard cost (4) some materials can be easily traced the operation usage cost without too much effort and those resources used by a sigle machine group are good for cost monitor and control (5) cost behavior analysis shows that the materials and parts are two major cost groups with variable cost nature and they are important areas for cost improvement.

Keywords: Wafer Cost, Cost Estimation, Activity-Based Costing

並列關鍵字

Wafer Cost ； Cost Estimation ； Activity-Based Costing

參考文獻

1. Bharara, A. and Lee, C.-Y.(1996), “Implementation of an activity-based costing system in a small manufacturing company”, INT. J. PROD. Res., V34, No. 4, 1109-1130.

3. Cooper, R.and Kaplan, R. S. (1988), “How Cost Accounting Distorts Product Cost,” Management Accounting, P20-P27.

4. Cooper, R.and Kaplan, R. S. (1990), “Measure Costs Right: Make the Right Decision,” The CPA Journal, Feb, 38-45.

7. Moinuddin, K., Collins, T., Bansal, A. et al(2007) ”Process Activity Mapping – Activity Based Costing for Semiconductor Enterprises”, Cost Management, Mar/Apr, 29-33

參考文獻