化學氣相沉積於液晶顯示器薄膜電晶體製程之均勻度改善研究

Abstract

本論文主要探討在不同製程條件下電漿輔助化學氣相沉積(Plasma Enhance Chemical Vapor Deposition)設備沉積Amorphous Silicon (a-Si)薄膜之特性，首先選擇四個輸入參數(射頻功率、腔體內壓力、上電極板孔洞大小、上下電極板間距)與兩個輸出變數(沉積厚度與均勻度)來建立PECVD系統模型，將輸入參數代入不同的數據，利用實驗設計法全因子的觀念尋找四個輸入參數(射頻功率、腔體內壓力、上電極板孔洞大小、上下電極板間距)與兩個輸出變數(沉積厚度與不均勻度)之間的關係。建立PECVD系統模型，利用田口法(Taguchi method) 進行實驗分析，而此實驗法是透過實驗進行系統參數最佳化設計的方法，重視實際的應用性，而非以困難的統計為依歸，田口方法是用來改善品質的工程方法(quality engineering)，又稱穩健設計（robust design），是透過工程最佳化的方式來進行品質改善的方法，所謂「穩健」是指所設計產品品質受到周圍環境影響的敏感度為最小。經由穩健設計去控制，進行模擬分析與實驗，期望輸出參數可達目標值。期望LCD在薄膜層a-Si製程的不均勻度可控制在10%以下。不均勻度控制的理想將可改善PECVD製程之良率。 本研究經由DOE 的實驗中獲得LCD膜質均勻度可以改善的條件，發現影響膜厚平均值最主要的是上電極板孔洞大小0.4mm，其次為上下電極板間距900mil，腔體內壓力1300mtorr 與射頻功率800W 則影響較小為最佳組合。同時也達到預期的品質目標，另外也達到了減少實驗次數的效益。改善前之沉膜均勻度為16.27% ，利用最佳製程參數得到沉膜均勻度為7.85%。

In this thesis, we discussed with the characteristics of amorphous Silicon (a-Si) thin film deposition in PECVD equipment by different process conditions. Four input parameters (RF power, chamber pressure, the upper electrode plate holes, upper and lower electrode plate spacing) and two output variables (deposition thickness and uniformity) are selected to establish thin film deposition model. Different data were applied to input parameters, and used experimental design of all factor concept to seek the relationship between four input parameters and two output variables. The thin film deposition model was created by using Taguchi method for experimental analysis, and this test method is supported by experiments conducted system parameter optimization process. Taguchi method is used to improve quality engineering methods also known as robust design for quality improvement methods to minimize the sensitivity to the surrounding environmental impact. Simulation and experiments verified that the desired output parameters reached the target value. The uniformity of a-Si thin-film layer is improved from 16.27% to 7.85%, which also provided better yield rate.