活性離子蝕刻於TFT-LCD之蝕刻率改善研究

Abstract

電漿技術在TFT LCD面板製程中廣泛被應用，例如乾蝕刻、薄膜沈積、去光阻等等都與電漿技術相關，乾蝕刻的優勢在於微結構控制良好，尤其台灣半導體製造技術的發達，轉移至TFT LCD製程，其線寬(line width)，深寬比(aspect ratio)，表面粗糙度(surface roughness)， via角度控制，均有極佳的水準，對電性上也可以得到較佳的表現。 本實驗主要使用活性離子蝕刻機台來進行乾式蝕刻，機台內使用氯氣來進行多晶矽（Poly silicon）AL鋁層蝕刻，建立電漿蝕刻機制的實驗模型，研究電漿蝕刻設備參數： 腔體壓力、功率、上電極封孔率、CLAMP 高度等，與蝕刻率、均勻度的關係。 研究方法是利用田口式方法來觀察電漿設備與蝕刻率、均勻度之間的關係，由實驗結果顯示出:蝕刻率主要影響為電漿功率為最大，壓力次之，封孔率再次之，CLAMP高最少。均勻度主要影響為封孔率為最大，CLAMP次之，壓力再次之，功率最少 電漿功率增加相對的也增加電漿密度，因為解離率上升會使得氯原子濃度及蝕刻率增加，再者因為基板為方形的關係，封孔率會改變電漿的均勻度，使得原本基板中間過快，四周過慢的蝕刻速率達到平衡。最後再加上CLAMP加高將電漿集中於基板，進而達到均化及優化。

Plasma technology has already widely been used in the TFT LCD panel manufacturing process. Such as dry etching, thin films deposited, and stripper…etc. Those are related to Plasma technology. The advantage of dry etching is well controlled in microstructure. Taiwan has the advantage in semiconductor manufacture and knowledge. With the strong foundation and know-how that could smoothly transferred to the TFT LCD manufacturing process and lead to well-controlled in the line width, depth-width ratio (aspect ratio), surface roughness, via angle control…etc., and also with better performance in electrical characteristics. In this thesis, we establish an experimental model of plasma etching mechanism. We use the chemical gases CL2/BCL3 on aluminum layer for Poly silicon in the Reactive Ion Etching machine (RIE) to do dry etching as our model. The plasma etching device parameters include: chamber pressure power, the electrode sealing rate, CLAMP height, the etch rate, and uniform degree of relationship. The method is using Taguchi methods to observe the relation with plasma equipment and the etching rate and uniformity. The results show: The major impact of etching rate is plasma power, and then followed by pressure, sealing rate, the last one is CLAMP. The major impact of uniformity is sealing rate, and then followed by CLAMP, pressure, the last one is plasma power. Plasma power also increases the plasma density, Due to dissociation rate rise will make the chlorine atom concentration and the etching rate increases. Furthermore, because the substrate is a square, in the past, etching speed rate in the middle of the substrate is faster than outside of substrate. Sealing rate will change the uniformity of the plasma and will make etching rate reach to balance. Finally, increasing the height of CLAMP let the plasma concentration on the substrate, thus achieving the homogenization and optimization.