New plasma etching techniques for control over Si and SiO2 etch profiles : Slanted plasma etching and advanced cyclic etching
New plasma etching techniques for control over Si and SiO2 etch profiles : Slanted plasma etching and advanced cyclic etching
- 주제(키워드) Plasma etching , Slanted plasma etching , Advanced cyclic etching , Etch profile
- 발행기관 아주대학교
- 지도교수 김창구
- 발행년도 2015
- 학위수여년월 2015. 8
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000020493
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
This thesis focuses on the development of new etch techniques for control over etch profiles of Si and SiO2. Slanted plasma etching was proposed for the fabrication of slanted Si structures with various angles and aspect ratios. In addition, advanced cyclic etching technique was developed for improving etch profiles of high aspect ratio SiO2 contact holes. Subjects of this work is presented in the following two parts. (1) A slanted plasma etching technique was developed for control over Si etch profiles under the practical plasma etching conditions. A Faraday cage system was used to control the angle and direction of ions incident on the substrate. A cyclic process consisting of alternating etching and deposition steps was performed using SF6 and C4F8 plasmas, respectively. The single-directional etch profiles was fabricated using a Faraday cage with a cylindrical type having a single horizontal grid plane. Mask shadowing effect and erosion of mask sidewall played an important role in the evolution of etch profiles during the single-directional slanted plasma etching. Double- and quadruple-directional slanted plasma etching were also conducted using Faraday cages with slanted-grid planes having an angle of 30˚ with respect to the horizontal substrate, respectively. Consequently, single-, double-, and quadruple-directional slanted etch profiles could be fabricated under practical plasma processing conditions using various types of Faraday cages. A novel process for the fabrication of 3-dimensional slanted Cu nanostructures was demonstrated using slanted Si nanostructures. First, slanted plasma etching of Si was conducted to form the 3-dimensional etch profiles of Si. Then, the slanted channels were filled with Cu by electroless plating. The SiO2 mask and overdeposited Cu films were removed by chemical mechanical polishing. Finally, wet chemical etching was performed to remove poly-Si between the Cu. By doing this, 3-dimensional slanted rod structures of Cu having periodic arrays in large area were successfully fabricated. (2) An advanced cyclic etching (ACE) technique was developed to reduce the diameter of contact holes having a high anisotropy and aspect ratio. The ACE technique consisted of the pre-deposition of a protection layer on the mask and a subsequent cyclic process of alternating etching and deposition steps. The protective layers for reducing the diameter of the amorphous carbon layer (ACL) mask were firstly deposited on the sidewall of the ACL mask using a C4F6/Ar/CH2F2 plasma. After depositing the protective layer, the contact hole was etched in a C4F6/Ar/O2/CH2F2 plasma. The diameter of the contact hole was reduced depending on the reduction in the diameter of the ACL mask. Consequently, the diameter of contact hole was successfully reduced to more than 26% of the original diameter of the ACL mask, and fabricated the contact hole having anisotropic etch profile with the high aspect ratio.
more목차
Chapter 1. Introduction 1
1.1 Plasma etching for the fabrication of Si and SiO2 structures 1
1.2 Control over etch profiles 5
1.3 Objectives 10
Chapter 2. Control over Si etch profiles using slanted plasma etching 11
2.1 Introduction 11
2.2 Experimental 14
2.2.1 Plasma system 14
2.2.2 Faraday cage 14
2.3.3 Slanted plasma etching 18
2.3 Fabrication of slanted channel structures of Si using slanted plasma etching 21
2.3.1 Single-directional slanted etch profiles 21
2.3.2 Multi-directional slanted etch profiles 30
2.4 Fabrication of slanted Cu nanostructures using slanted plasma etching 36
2.4.1 Single-directional slanted Cu structures 40
2.4.2 Multi-directional slanted Cu structures 47
2.5 Summary 58
Chapter 3. Etch profile improvement of SiO2 contact holes 60
3.1 Introduction 60
3.2 Experimental 64
3.2.1 Plasma system 64
3.2.2 Sample 64
3.2.3 Process conditions 67
3.2.4 Analysis of etch profiles 68
3.3 Etch profiles of SiO2 contact holes using a conventional continuous etching process 71
3.4 Etch profiles of SiO2 contact holes using an advanced cyclic etching process 73
3.5 Summary 83
Chapter 4. Conclusions 84
Bibliography 88
Abstract (국문초록) 102
