應用六標準差於微機電系統三軸加速器封裝良率改善之研究

Applying Six-Sigma to Yield Rate Improvement of Die Bond Process for Piezoresistive Triaxial Accelerometers

臺灣積體電路（integrated circuit, IC）設計產業正處蓬勃發展之際，下游IC封裝廠扮演著關鍵角色。在競爭激烈的環境中，IC封裝廠積極對IC封裝製程的良率進行改善，以期提升客戶滿意度及競爭力。在微機電系統（micro electro-mechanical system, MEMS）三軸加速器（triaxial accelerometer）的IC封裝製程中，黏晶（die bond）站所產生的應力會造成晶片變形，進而導致MEMS三軸加速器的靈敏度與偏差運算產生錯誤。本研究應用了六標準差（Six-Sigma, 6σ）的DMAIC手法—界定（Define）、量化（Measure）、分析（Analysis）、改善（Improve）、控制（Control），針對MEMS三軸加速器黏晶製程進行應力分析。定義（D）階段先瞭解終端客戶的聲音，並對退貨品問題進行探討；衡量（M）階段先進行量測設備的重複性和再現性分析，再衡量製程能力以做為改善的基礎；分析（A）階段則使用原因與效果矩陣（cause & effect matrix）來找出造成應力之可能影響因子；改善（I）階段則利用實驗設計（design of experiment, DOE）方法找出影響因子的最佳設計及確認改善效益；最後，控制（C）階段運用管制圖監控後續的製造良率。研究結果顯示，透過六標準差方法可將MEMS三軸加速器的黏晶製程不良率由3.22%降低至2.07%。

Taiwan’s integrated circuit (IC) design industry is booming, and downstream IC packaging companies are playing a key role. In the competitive environment, IC packaging companies are actively improving the yield rate of IC packaging process to enhance customer satisfaction and competitiveness. In the IC packaging process of micro electro-mechanical system (MEMS) triaxial accelerometer, the stress generated by the die bond station will cause wafer deformation, which will lead to errors in the sensitivity and deviation calculation of the MEMS triaxial accelerometer. In this research, the DMAIC (Define, Measure, Analyze, Improve, and Control) approach of Six-Sigma (6σ) is applied to analyze the stress generated at die bond process for MEMS triaxial accelerometer. The Define (D) stage starts with understanding the voice of the end customer and exploring the problem of returned goods. The Measure (M) stage conducts a repeatability and reproducibility analysis for the measurement equipment and then measures the process capability as a basis for improvement. The Analyze (A) stage uses the cause & effect matrix to identify the possible influence factors for stress generation. The Improve (I) stage applies the design of experiment (DOE) method to find the optimal design of influence factors and ensure the improvement effect. Finally, the Control (C) stage uses the control chart to monitor the subsequent manufacturing yields. The research result shows that the defect rate of the die bond process for MEMS triaxial accelerometer could be reduced from 3.22% to 2.07% by using Six-Sigma method.