Title Page
ABSTRACT
Contents
CHAPTER 1. Introduction 18
1.1. The present and the technological development of high-integrated semiconductors 18
1.2. Current issues for high-integrated semiconductor fabrication 22
1.3. Object of thesis 25
1.4. Organization of the thesis 26
CHAPTER 2. Theoretical Background 27
2.1. Carbon 27
2.2. Amorphous carbon 31
2.3. Hardmask for semiconductor process 37
2.4. Amorphous carbon for semiconductor hardmask 44
2.5. Microstructure analysis of the amorphous carbon film 48
CHAPTER 3. Nitrogen doping effect and etch characteristics 58
3.1. Introduction 58
3.2. Experimental procedure 61
3.2.1. Fabrication of nitrogen doped amorphous carbon film 61
3.2.2. Characterization of film structure 63
3.2.3. Dry etching characteristics 65
3.3. Results and Discussion 66
3.3.1. Basic characteristics 66
3.3.2. Etching characteristics 79
3.3.3. Effect of nitrogen on fluorine penetration in amorphous carbon films 84
3.4. Summary 90
CHAPTER 4. Boron doping effect and etch characteristics 91
4.1. Introduction 91
4.2. Experimental 94
4.2.1. Fabrication of doped amorphous carbon 94
4.2.2. Characterization of a-C film structure 95
4.2.3. Dry etching characteristics 97
4.3. Results and Discussion 98
4.3.1. Basic characteristics 98
4.3.2. Etching characteristics 107
4.3.3. Microstructural changes in a-C films by boron doping 112
4.4. Summary 125
CHAPTER 5. Boron-Nitrogen co-doped amorphous carbon 126
5.1. Introduction 126
5.2. Experimental 131
5.3. Results and Discussion 134
5.3.1. Basic characteristics 134
5.3.2. Etching characteristics 140
5.3.3. Ar plasma treatment effects 143
5.4. Summary 146
CHAPTER 6. Conclusion 147
6.1. Summary of results 147
6.2. Future Work and Suggested Research 149
References 150
요약(국문초록) 163
Table 2.1. Comparison of deposition method for amorphous carbon 36
Table 2.2. Various mask material comparison chart. 42
Table 3.1. The measured film thicknesses after etching, the times at which C- and CF-ions were detected, and the calculated penetration depths of fluorine in the N... 88
Table 5.1. Literature data on structural and physical properties of c-BN and h-BN 130
Table 5.2. Atomic percent based on nitrogen gas amount and thickness from XPS wide scan analysis 138
Figure 1.1. (a) Edge devices and edge nodes in relation to the cloud. [1] (b) Layered model for cloud edge-based IoT services delivery. [2] (c) Process innovations... 20
Figure 1.2. (a) Cross-sectional view of a V-NAND.[10] (b) Peri under cell of memory structure.[6] (c) The International Technology Roadmap for Semiconductors... 21
Figure 1.3. (a) Changes in resist thickness as wavelength of lithography source decreases.[11] (b) Hardmask performance as a function of carbon content in spin on... 24
Figure 2.1. Phase diagram of carbon. 29
Figure 2.2. Schematic illustration of sp³, sp² and sp¹ hybridized carbon. 30
Figure 2.3. Ternary phase diagram of amorphous carbon. 33
Figure 2.4. Correlation of (a) density, (b) hardness, (c) optical band gap against sp³ fraction 34
Figure 2.5. Schematic diagram of densification by subplantation. 35
Figure 2.6. In-depth illustration of the pre-, post-, and inter-process challenges that may arise when applying a hardmask. 40
Figure 2.7. Characteristic of plasma dry etching reaction. 41
Figure 2.8. Process failures due to increased thickness of mask layer. (a) Wiggling. (b) Bowing.[14], [44](c) Key alignment failure (Transparency). 43
Figure 2.9. (a) Precursors in CVD deposition of amorphous carbon. (b) Properties of amorphous carbon as function of hydrogen at%. 46
Figure 2.10. (a) Dry etching amount and selectivity of carbon films to SiO₂ depending on the working pressure by DC sputtering method.[48] (b) DFT calculated... 47
Figure 2.11. Basic algorithm for the combined N 1s/O 1s/C 1s deconvolution of XPS spectra of chars and amorphous carbons. 50
Figure 2.12. Diagram showing the beams interfering to form the image contrast in (a) axial phase contrast imaging in transmission electron microscopy (TEM), and (b)... 53
Figure 2.13. Schematic representation of the STEM SI acquisition process. The data cube is filed pixel-by-pixel but the spectrum is acquired in parallel. 54
Figure 3.1. Schematic structure of various nitrogen doped carbon. 60
Figure 3.2. A schematic of the DC sputtering system. 62
Figure 3.3. Deposition rate of amorphous carbon film according to nitrogen concentration. 72
Figure 3.4. XPS wide scan plot of amorphous carbon according to its plasma gas ratio. 73
Figure 3.5. Surface images of the nitrogen-doped carbon films observed with SEM and AFM. 74
Figure 3.6. XRR (a) measurement and (b) Densities of the nitrogen-doped amorphous carbon films. 75
Figure 3.7. (a) Deconvolution and (b) corresponding quantified ratios of the N1s spectra of the nitrogen-doped amorphous carbon films. The obtained ratios were... 76
Figure 3.8. XPS plot of amorphous carbon according to its plasma gas ratio (a) C1s scan (b) N1s scan 77
Figure 3.9. (a) Diffraction patterns of the nitrogen-doped amorphous carbon films. (b) RDF (Radial distribution function) plot and (c) Average distance to the first... 78
Figure 3.10. Etching characteristics of amorphous carbon films with different concentrations of nitrogen. (a) Schematic of the sample structure before etching. (b)... 81
Figure 3.11. (a) Thickness of SiO₂ and nitrogen-doped amorphous carbon films before and after etching, as measured from cross-sectional SEM images of the films.... 82
Figure 3.12. FIB cross section image of the amorphous carbon films (a, b) N 3.2 at% (a) as deposited, (b) etched, (c, d) N 9.0 at% (c) as deposited, (d) etched, (e, f) N... 83
Figure 3.13. Effect of nitrogen doping on the resistance to fluorine penetration in the amorphous carbon film. TOF-SIMS analysis of the fluorine depth profile of the (a)... 87
Figure 3.14. Schematic of the behavior of fluorine in carbon materials (a) without nitrogen doping and (b) with nitrogen doping. 89
Figure 4.1. (a) Variation of the sp 3 fraction with the ion energy for ta-C, 2% and 4% boron concentrations.[100] (b) Hardness, stress, and boron dopant and hydrogen... 93
Figure 4.2. SEM images of surface of boron-doped carbon films. 101
Figure 4.3. XPS plot of a-C wide scan. 102
Figure 4.4. (a) Surface images and (b) roughness of the boron-doped a-C films observed by AFM 103
Figure 4.5. (a) XRR measurement and (b) density results of the boron doped a- C films 104
Figure 4.6. XPS narrow scan of a-C: (a) C1s scan and (b) N1s scan 105
Figure 4.7. XPS narrow scan of a-C B1s scan 106
Figure 4.8. Selectivity of SiO₂ and boron-doped a-C films. 109
Figure 4.9. FIB cross section image of the a-C films. 110
Figure 4.10. (a) Change in a-C film thickness with etching time (b) Calculated selectivity with etching time determined by film thickness. 111
Figure 4.11. EELS analysis result of C K edge region using STEM-EELS. (a) Annular dark-field STEM image of the cross section of the boron doped a-C film. (b)... 118
Figure 4.12. Relative sp²/sp³ ratios according to the depth of the a-C layers and the atomic percent of boron. 119
Figure 4.13. EELS analysis result of B K edge region using STEM-EELS. (a) Representative spectra for each cluster. Colors are consistent with (b). (b) Spatial... 120
Figure 4.14. Dimensionality-reduced space and the clustering result obtained by applying the cluster analysis assisted by dimensionality reduction methods to the core-... 121
Figure 4.15. Coefficient maps obtained by applying non-negative matrix factorization to the core-loss EELS dataset of the boron doped amorphous carbon layers.... 122
Figure 4.16. (a) Atomic ratios of boron, carbon, nitrogen, and oxygen according to layer depth. (b) Fluorine penetration resistance with thickness of 45.9 at% boron-... 123
Figure 4.17. (a) Calculated △G° for the reaction for each phase under the deposition situation by FactSage program. (b) XPS B1s depth profile of B 45.9 at%... 124
Figure 5.1. Crystal structure of (a) cubic and (b) hexagonal BN. Hardness variation with (c) nitrogen partial pressure and (d) PLD laser energy[133] in BCN... 129
Figure 5.2. XPS curves of the boron nitrogen co-doped amorphous carbon films for different nitrogen gas flow (a) Wide scan, narrow scan of (b) B1s 136
Figure 5.3. (a) XRR measurement and (b) density fitting results as a function of nitrogen gas flow amounts. 137
Figure 5.4. Biaxial stress of a-C thin film measured by multi-beam optical sensor (MOS) system 139
Figure 5.5. Etching characteristics of a-C films with different nitrogen gas flow. (a) Change in boron nitrogen co-doped a-C film thickness with etching time. (b)... 142
Figure 5.6. (a) Thickness after Ar plasma treatment and dry etch according, (b) Etch amount after Ar plasma treatment and dry etch process on Ar plasma treatment conditions. 145