臺灣博碩士論文加值系統

本文將討論在反應性離子蝕刻系統內，吾人利用實驗計畫法最佳化以氟化物為氛圍的氮化矽之電漿蝕刻特性。
隨著電子元件尺寸的縮小，蝕刻特性必須被精確的控制，諸如︰蝕刻率、均勻性等等。不僅如此，吾人更要能夠掌控處理某些相當複雜且相互抵觸的製程特性。有鑑於此，吾人利用田口法進行實驗設計，以期能相當有效率的調配製程參數並使製程特性最佳化。此實驗計畫法中，包括四個實驗的製程變數，其中有：蝕刻反應腔體內的壓力、RF能量以及兩種反應氣體。
在完成實驗後，再經由實驗結果做分析表格與點線圖，吾人可以有效的決定對蝕刻特性的重要因子並完成各實驗因子對製程的效應。最後，吾人可以建立一個簡要的二次方程式來描述整個的蝕刻模型。總的來說，田口式所發展的實驗設計法的確提供研究者相當有效的工具，能快速的掌控實驗的變數使製程達到最佳化。
經由此實驗計畫的設計，吾人在CF4/O2 和 SF6/He 的系統中分別得到蝕刻率2600與500A/min，均勻性5和6％的成果且底切寬度為1500A；而在氣體比例小於1/1的CF4/He 混合氣體系統中，得到非等向性且光滑蝕刻表面的蝕刻特性。

Reactive ion etching (RIE) of silicon nitride in a plasma system, with fluorine-based gas mixture, had been studied using an experimental design. With the dimensions of devices decreasing, the etching characteristics, such as etching rate and uniformity of etching rate, must be controlled and some complex tradeoffs need to be managed. For this reason, we initiated a program to optimize etching characteristics using Taguchi robust design as a Design of Experiment (DOE) methodology. This DOE consisted of four major variable parameters, which were RF power, chamber pressure and two processing gas. Depending on analyzed data, the effects of the each variable on etching performance are discussed and main factor is examined. The physical and chemical explanations have been based upon the etching model obtained with the DOE. Overall Taguchi method is a helpful tool to optimize the experimental variables and the aimed etching performance was investigated by using the model. The experimentally optimal results are as follows: low etching rate, 500Å/min and applicable uniformity, 6% are achieved for the etching process with two kind of etching gas mixture, CF4/O2 and SF6/He together with measurements of plasma parameters. In addition, processes with CF4/He gas mixture with gaseous ratio ≦1/1 result in non-undercutting etching profile and smooth surface.

Chapter.1 Introduction……………………………..1
1.1 Introduction………………………………………………….1
1.2 The Respect of Research…………………………………..1
Chapter.2 Theorem in Experiment………………..3
2.1 Technique Overview………………………………………..3
2.2 Basic Physics and Chemistry of Plasma Etching……….5
2.2.1 Briefly comments on plasma generation……………..5
2.2.2 Reaction chain of plasma etching mechanisms……..5
2.3 Constructs of Design of Experiment (DOE)……………...6
2.3.1 TAGUCHI robust method………………………………6
2.3.2 The orthogonal array and experimental configurations
..…………………………………………………………………8
2.3.3 Signal-to-noise (S/N) ratio and analysis techniques..9
Chapter.3 Experiment……………………………16
3.1 Measurement of Undercut in SF6 Etch…………………18
3.2 Optimization of Etching Rate Uniformity in CF4/O2 Etch
………………………………………………………………19
3.2.1 Initial experiment: L9 experiment……………………..19
3.2.2 Confirmation run……………………………………….19
3.3 Optimization of Etching Rate Uniformity and Etching Rate In SF6/He Etch……………………………………...20
3.3.1 Initial experiment: L9 experiment…………………….20
3.3.2 Confirmation run……………………………………….20
3.3.3 Finding out the more appropriate conditions by analyzing the results of L9 design…………………….…….20
3.3.4 Measurement of undercut in optimal recipe of SF6/He Etch…………………………………………………………...21
3.4 Optimization of Etching Rate Uniformity and Low Etching Rate in CF4/He Etch………………………………………22
Chapter.4 Results and Discussions………….…32
4.1 Measurement of Undercut in SF6 Etch…………………32
4.2 Optimized Results in CF4/O2 Etch.………………………33
4.2.1 Results and analysis of L9 design…………………….33
4.2.2 Results and discussions of confirmation runs………35
4.3 Optimized Results in SF6/He Etch………………………38
4.3.1 Results and analysis of L9 design…………………….38
4.3.2 Results and discussions of confirmation runs………41
4.3.3 The more appropriate etching conditions……….…..42
4.3.4 Measurement of undercut in optimal recipe…………42
4.4 Optimized Result in CF4/He Etch………………………..44
4.4.1 Results and analysis of L4 design…………………….44
4.4.2 Results and Discussions of etching morphology……46
Chapter.5 Conclusion……………………………..86
References…………………...…………………….89

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