TFT LCD 乾蝕刻製程化學性側蝕法研究

Abstract

TFT-LCD 製程中，蝕刻功用為將所需之線路或圖形產生，將黃光製程前玻璃基板表面沉積之薄膜(通常厚度為數千Å)沒有被光阻覆蓋之區域，以化學或物理反應將之除去，以此方式將光罩定義之圖型進行轉移至原先沉積之薄膜上，這圖型或線路未來將成為TFT-LCD 中元件成員之一。 目前用於TFT-LCD 蝕刻技術上主要有濕蝕刻(Wet Etching)及乾蝕刻(Dry Etching)兩種方式，前者主要利用化學性(藥水)反應進行蝕刻;後者採用物理性(電漿)反應進行蝕刻,當然後者藉由參數之微調也有傾向化學性之乾蝕刻; 就結果而言,濕蝕刻有較佳之產能利於生產,但藥水的非等向性蝕刻會造成undercut問題而有線寬控制較差之結果;相對而言，乾蝕刻機台雖抽真空過程造成產能較低，非等向性蝕刻卻有較佳之線寬控制。 本論文所將探討如何以乾蝕刻製程方式,微調參數,進而達到類濕蝕刻之乾蝕刻製程(化學性側蝕法)，藉此提高產能並降低乾蝕刻製程中產生之瑕疵問題(Defect) 。 研究內容將利用因果舉證法與田口實驗法，進行乾蝕刻機台參數微調為化學性側蝕法之因子進行研究，對因子做出篩選，藉由實驗找出正確因子，進而對製程條件做出改善，最終可將此化學性側蝕法導入生產行列。

During TFT-LCD array process, etching plays a crucial role of creating designed circuits and patterns. By applying chemical or physical process etching can remove certain parts of the deposit film which are not protected by the photo resist. Therefore it can transfer specific patterns from the photo mask to the deposit film (usually thousands of Å) on the glass. The transferred circuit and patterns are important components in the TFT-LCD manufacturing process. Currently there are two types of etching techniques in TFT LCD etching process, Wet and Dry Etching. The former applies chemical agent while the later takes the physical reaction approach (via plasma); In practice one can fine tune some parameters to change dry etching to behave like chemical type. Conventional results show Wet etching is superior in terms of factory throughput. However its isotropic etching by chemical agent may cause undercut issue, which makes line width hard to control. To the contrary although Dry Etching has lower throughput that is introduced by vacuuming process. Its anisotropic property makes it a great method when line width quality is a top priority. The focus of this dissertation is on Dry Etching. We will show by fine tuning some dry etching parameters to make it similar to wet etching, one can achieve the benefit of both wet and dry etching, i.e. higher throughput and better line width control (less occurrence of defects). This paper applied the methodology of Evidence Act and Taguchi experimental method to research the genuine parameters that make Dry Etching process act similar to the wet one. We filtered the candidate parameters and searched for the optimized parameter set in the experiments. We hope the study results can improve existing dry etching process recipe and eventually this new concept can be introduced in the mass-production manufacturing process.