設計調整發光二極體光激螢光光譜波長之自動化回饋系統

Abstract

綠色環保已經是全世界科技產業發展的首要目標，發光二極體(Light Emitting Diode , LED)產品最終勢必會取代白熾燈泡。然而，LED產品的出貨規格完全是訂定在波長和亮度上，波長又是由磊晶(Epitaxy, EPI)製程所決定，如何在磊晶製程的過程中控制變因，使生產出來的LED成品皆能在客戶要求之規格內，則是每個工廠致力研究的目標。由於EPI製程是同時對同一批次中的多片晶圓進行製造程序，此與半導體僅針對單片晶圓之製程大不相同。因此本研究之主要目的即是建構一個發光二極體光激螢光光譜波長的先進製程控制系統。本研究先利用迴歸分析建立影響EPI製程之變動因子與LED產品波長間之線性關係式，然後再利用指數加權移動平均(Exponentially Weighted Moving Average, EWMA)和權重法結果相互比較，選出效益較佳之演算法來建立一套自動化回饋控制系統，以藉由調整變動因子來對波長進行快速的補償與控制。本系統在產品生產過程中持續收集產品的製程參數值和量測值，再計算出新的製程參數值並輸入到機台內，以使下一批LED半成品可以快速調整到目標值，進而提升LED產品之良率。本研究最後由新竹科學園區一個4吋LED廠之實際案例來說明本研究所提出之自動回饋系統確實有效可行。

Green environmental protection becomes a global goal for high-tech industry; therefore, LED will imperatively replace the incandescent lamps in the near future. The quality of LED is determined by the wavelength and brightness. Moreover, the wavelength is determined by the EPI process. The LED manufacturers try to control the manufacturing process in order to meet the customer’s specifications. Because EPI process is a multi-wafer batch process which is different from the signal-wafer process in the semiconductor, the advanced process control utilized in semiconductor must be modified for the EPI process. This study first constructs a linear model (LM) to describe the correlations between the control factors and the wavelength of LED using regression analysis, then the Exponentially Weighted Moving Average (EWMA) is utilized to build a suitable feedback control to achieve fast compensation and control of the wavelength. The system can continuously collects the data of process parameters from the manufacturing process and calculates new values of the process parameters. These new values of the process parameters will be input into the machine, so the next batch of semi-finished LED products can be adjusted to the target. Finally, a real case from a 4-inch LED manufacturer is utilized to illustrate the effectiveness of the proposed method.