田口方法於線外品管多重品質特性製程最佳化之應用研究

Abstract

田口博士提出損失函數(Loss Function)的觀念，透過改善品質來降低生 產成本，以達到產品之穩健性。傳統田口方法應用於製程之實例，於已發 表的文獻中，大都只探討單一品質特性最佳化的問題，對於製程中同時有 多個品質特性最佳化的問題，也只停留在以工程師經驗判斷的階段，而在 實務上產品往往是具有多個品質特性的，且這些品質特性損失間均可能有 極高的相關性。本研究乃是針對多重品質特性製程，提出一多重品質績效 衡量的統計量，它是將個別品質特性損失正常化，以消弭損失函數因品質 特性或衡量單位的不同所造成之差異，使各品質特性之損失能處在同一水 平線上來比較，同時依品質特性重要程度分別賦予權重作加總，並延續田 口 SN比的精神與二步驟最佳化的分析程序，達到多重品質特性製程之最 佳化。本研究以IC 製程中，電漿輔助化學氣象沉積(PECVD)SiNx的製程， 來驗證此方法之有效性。 Dr. Taguchi developed the concept of loss function and used the Signal-to-Noise(SN) ratio to evaluate the performance of product quality. By finding the optimal combination levels of factors in the parameter design, the performance of product qua- lity could be made insensitive (robust) to noise factor. Most application of taguchi methods to-date have only been concened with the optimization of a single-response process or product. Handling the more demanding multi-response cases,which require the simultaneous optimization of more than one responses in the same process, is hardly ever considered, the usual recom- mendation was "to be left to engineering judgement". In pratice, we often have to deal with multi- response process or product and it is usually to optimize such case just by engineering ex- perinces. the diffucility will become even more pronounced if these responses are highly correlated. This thesis therefore developed a technique generalized the ideas of Taguchi's SN ratio and the two-step optimization pro- cedure to optimized simultaneously the multi- response in a pro- cess. An experiment of plasma enhanced chemical vapor deposition (PECVD) process was conducted and verify the effectiveness of this new multi-response optimization technique.