CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

More documents

Recommendations

Info

susceptor, the flow pattern can be distorted to a certain degree at the beginning, but shortly it will restore to a balanced laminar flow between the susceptor/substrate and the tube wall. This effect should not affect the thin film growth considering the small influence on the diffusion behavior in the stationary boundary layer right above the substrate surface. In an axisymmetric CVD reactor, the flow pattern is more complicated due to the velocity change in both axial and radial directions when flowing onto the substrate surface. The velocity boundary layer thicknesses are never going to be much smaller than the susceptor radius under any reasonable flow conditions.[7] After the bulk convection delivers the gaseous precursors to the vicinity of the substrate surface, the convective transport will change to diffusive behavior in a stagnant boundary layer due to a no-slip boundary condition (velocity at the wall is zero) and viscous friction. The mass transfer through this layer is driven by the concentration gradient from the bulk gas phase to the substrate surface where the thin film forming reaction consumes incoming species. The diffusion kinetics is illustrated by Fick's law, which relates the mass diffusion flux to the concentration gradient and a diffusivity constant. This diffusivity constant is dependent on certain gas kinetic parameters introduced earlier, i.e., the mean molecular speed ( ) and mean free path. Considering the relative kinetics of this diffusion step and the following surface reaction, either of them can be a rate control step for the thin film growth. A simple model for the understanding of the control mode is introduced here. Assuming steady-state CVD thin film growth and negligible desorption/reevaporation, the diffusing species A moving from the bulk gas phase ( nb) to the growing surface (n0) possesses a diffusivity constant of D and encounters a boundary layer thickness of δ. According to Fick's law, we can obtain 13
J r J A -D n b-n 0 δ n or for the fraction depletion of reactant at the surface, f 0 n b-n 0 n b J r Dn b δ n There are two limiting cases, diffusion control and reaction control, which can be derived from Eq.(1.4). That is when f0 is very small and there is almost no difference of concentration of species A from the bulk gas phase to the substrate surface, the thin film growth is in reaction control mode and the thin film growth rate is dependent on the surface reaction rate only. The other case is when f0 is approaching 1. In this case, the surface concentration of species A is very low due to the much faster surface reaction rate than the diffusion rate and the thin film growth is in diffusion control mode. The intermediate case is more difficult to analyze and control practically, so it should be avoided in CVD process. Appropriate film growth mode can be selected/controlled to achieve the best film uniformity in different CVD reactors. For example, in the axisymmetric reactor, where the substrate temperature uniformity is difficult to achieve, the thin film growth in diffusion control mode can help get uniform films.[12] 14 (1.3) (1.4) In the processes of both convection and diffusion, a unique phenomenon of CVD is homogeneous reaction. Depending on the thermal stability/reactivity of the precursors and the temperature profile in the reactor, gas phase homogeneous reaction can start from certain points. Excessive gas phase reaction can generate particles on the grown thin film and affect its physical properties. To minimize gas phase interaction, an effective way is to reduce the system pressure and thus increase the molecular mean free path. Elimination of gas phase reaction can be achieved by ALD thin film growth, which separates the injection of different reactants by
Page 1 and 2: CHEMICAL VAPOR DEPOSITION OF THIN F
Page 3 and 4: ABSTRACT Chemical vapor deposition
Page 5 and 6: DEDICATION This dissertation is ded
Page 7 and 8: φ In-plane tilt angle of X-ray dif
Page 9 and 10: ACKNOWLEDGMENTS It is my pleasure t
Page 11 and 12: CONTENTS ABSTRACT .................
Page 13 and 14: 3.2.1 Introduction ................
Page 15 and 16: LIST OF TABLES Table 1. Hafnium ami
Page 17 and 18: indicated by the complex FMR curve.
Page 19 and 20: Fig. 49. Ferromagnetic resonance cu
Page 21 and 22: growth rate, good step coverage and
Page 23 and 24: growth of thin film oxides due to t
Page 25 and 26: one can uniformly deliver precursor
Page 27 and 28: for the next reaction step as shown
Page 29 and 30: Fig. 3. Schematic of a typical dire
Page 31: is predominantly dependent on syste
Page 35 and 36: surface passivation with certain in
Page 37 and 38: ay spectroscopy (EDS), Wavelength d
Page 39 and 40: incidence angle is larger than cert
Page 41 and 42: epresenting those characteristic ph
Page 43 and 44: 1.2.3.3 X-ray Diffraction (XRD) X-r
Page 45 and 46: exhibit diffraction peaks in the no
Page 47 and 48: (nanometers to tens of nanometers),
Page 49 and 50: strongest absorption of microwave s
Page 51 and 52: pinch-off to indicate the lack of a
Page 53 and 54: coupling is from unbound ferrite-fe
Page 55 and 56: diffusion barrier material in micro
Page 57 and 58: Fig. 14. A cross sectional scanning
Page 59 and 60: In spite of the same spinel structu
Page 61 and 62: ferrites has been investigated exte
Page 63 and 64: systems is showed in Fig.18.[83] As
Page 65 and 66: precursor vaporization process, e.g
Page 67 and 68: CHAPTER 3. PLASMA ENHANCED ATOMIC L
Page 69 and 70: the initial surface chemistry for t
Page 71 and 72: delay time of 2 seconds between spe
Page 73 and 74: Kcal/mol respectively. The stronger
Page 75 and 76: negative slope) behavior in the pum
Page 77 and 78: the existence of both physisorbed a
Page 79 and 80: decomposition products (Hf-H) and g
Page 81 and 82: dried by ultra high purity N2 gas.
Page 83 and 84:
pressure for XPS analysis is around
Page 85 and 86:
Hf and N elements, incorporation of
Page 87 and 88:
[150,151] This is a unique feature
Page 89 and 90:
software. The thickness results are
Page 91 and 92:
CHAPTER 4. DIRECT LIQUID INJECTION
Page 93 and 94:
film growth region. The properties
Page 95 and 96:
solution was accurately controlled
Page 97 and 98:
size). For the rocking curve analys
Page 99 and 100:
oxygen does not participate in the
Page 101 and 102:
ecause vapor velocity cannot be cha
Page 103 and 104:
Fig. 40. Cross-sectional view by fi
Page 105 and 106:
the MgAl2O4 substrate confirms cube
Page 107 and 108:
pattern. Fig.44(b) has diffraction
Page 109 and 110:
We have used an AGM (Alternating Gr
Page 111 and 112:
as derived equations for different
Page 113 and 114:
deposited at 600˚C is the lowest.
Page 115 and 116:
wave states degenerate with the FMR
Page 117 and 118:
Fig. 53. ϕ-scan of nickel ferrite
Page 119 and 120:
Surface roughness characterized by
Page 121 and 122:
Fig. 56. X-ray diffraction θ-2θ c
Page 123 and 124:
4.4 Conclusion In summary, we have
Page 125 and 126:
CHAPTER 5. DIRECT LIQUID INJECTION
Page 127 and 128:
eaction zone of the tube furnace is
Page 129 and 130:
Fig. 58. X-ray diffraction characte
Page 131 and 132:
interface. This phenomenon probably
Page 133 and 134:
6.1 Conclusion CHAPTER 6. CONCLUSIO
Page 135 and 136:
the temperature range of 600˚C to
Page 137 and 138:
such as PMN-PT and PZN-PT. CVD proc
Page 139 and 140:
[18]. L. S.-J. Peng, X. X. Xi, B. H
Page 141 and 142:
[54]. B. O. Johansson, J. -E. Sundg
Page 143 and 144:
[96]. J. D. Adam, S. V. Krishnaswam
Page 145 and 146:
[136]. J. Zhao, V. Fuflyigin, F. Wa
Page 147 and 148:
APPENDIX A: LabVIEW PROGRAM FOR PEA
Page 149 and 150:
APPENDIX B: TDMAH MOLECULAR STRUCTU
Page 151 and 152:
H 18 B19 2 A18 1 D17 H 18 B20 2 A19
show all

CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?