vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
AKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vii
CONTENTS
ix
LIST OF TABLES
xii
LIST OF FIGURES
xiii
LIST OF SYMBOLS
xvi
LIST OF APPENDIX
xviii
INTRODUCTION
1.1
Literature Review
1
1.2
Research Objective
3
1.3
Research Scope
3
1.4
Thesis Plan
4
THEORY
2.1
Magnetic Material
6
2.1.1
Ferromagnetic Material
6
2.1.2
Antiferromagnetic Material
8
viii
2.2
Band Structure
9
2.3
Thin Film Deposition
10
2.3.1
Radio Frequency (RF) Sputtering
13
2.3.2
Electron Beam (e-beam) Process
16
2.4
2.5
Thickness Measurement
17
2.4.1
17
2.4.2 Dektak3 Surface Profiler
19
The Four-Point Probe
20
2.5.1
2.6
Resistiviy of Arbitrarily Shaped
Samples
20
Giant Magnetoresistance
22
2.6.1
Theoretical Model
23
2.6.1.1 Single-Current Model
23
Benefit Of GMR
26
2.6.2
3
Film Thickness Monitor (FTM)
METHODOLOGY
3.1
Sample Preparation
29
3.1.1 Deposition by RF Sputtering Method
29
3.1.2
3.1.1.1 High Vacuum Coater Setup
30
3.1.1.2 Substrate Pre-Clean
33
3.1.1.3 Pre-sputtering Process
33
3.1.1.4 RF Sputtering Process
33
Deposition by Electron Beam Method
35
3.1.2.1 Edwards Auto 306 Evaporation
Systems
3.2
3.3
36
3.1.2.2 Substrate Pre-Clean
37
3.1.2.3 Electron Beam Evaporation Process
37
Annealing Process
38
3.2.1
40
Temperature Uncertainty Calibration
Measurement
41
3.3.1
Thickness Measurements
41
3.3.1.1 Measurement by Using FTM
42
3.3.1.2 Measurement by Using Dektak3
ix
Surface Profiler
3.3.2
4
MR Measurement
42
45
RESULT AND DISCUSSIONS
4.1
Magnetoresistance for RF Sputtering Film
48
4.1.1
Magnetoresistance (MR) Curve
48
4.1.1.1 Effect of Sample Thickness
50
4.1.1.2 Effect of Working Pressure
54
4.1.1.3 Effect of Bilayers
58
4.1.2 Effect of Annealing Process
61
4.1.2.1 Annealing Time
61
4.1.2.2 Annealing Temperature
64
4.1.2.3 Effect of Annealing Temperature
4.2
4.3
5
for Different Bilayers
68
Magnetoresistance for e-beam Film
71
4.2.1 Effect of Magnetic Field
71
4.2.2
Effect of Buffer Layers
73
4.2.3
Effect of Annealing Time on e-beam Film
76
Comparison Between Sputtering and e-beam Method 78
CONCLUSION AND SUGGESTION
5.1
Conclusion
81
5.2
Suggestion
83
REFERENCES
85
APPENDICIES
Appendix A
94
PRESENTATIONS
96
x
LIST OF TABLE
TABLES NO.
TITLE
PAGE
1.1
Material and their function in system
4
3.1
Label of samples prepared by RF sputtering
35
3.2
Parameters of samples prepared by e-beam method
38
3.3
Parameters of annealing for the sample prepared by
RF sputtering method
3.4
Annealing parameter for sample prepared by e-beam
method
3.5
4.1
40
Thickness detected by using FTM and Dektak3
Surface Profiler
3.6
39
45
Current and resistance values for current source
testing
46
Working pressure and deposition rate
55
xi
LIST OF FIGURE
FIGURE NO.
2.1
TITLE
A typical hysteresis loop of antiferromagnetic
material
2.2
PAGE
7
Variation with the temperature of the susceptibility
for an antiferromagnetic.
8
2.3
Moment spin of an antiferromagnet
9
2.4
Thin film processes
12
2.5
Schematic of the ion-solid interactions and the
sputtering process
13
2.6
The schematic of RF sputtering system
14
2.7
Basic configuration of e-beam
17
2.8
Film Thickness Monitor
18
2.9
Schematic of measurement for Film Thickness Monitor
18
3
2.10
Dektak Surface Profiler
19
2.11
A Collinear Four-point Probe
20
2.12
Four-point Van der Pauw method
21
2.13
The magnetic multilayer type, in which the
magnetizations are forced from natural AF-mode
(θ = 0°) to F-mode (θ = 180°) by H
23
2.13
GMR phenomena showing a) low and b) high resistance
24
2.14
Resistance effectiveness in parallel configuration
25
2.15
Resistance effectiveness in anti-parallel configuration
25
2.16
Basic IBM suspended head design
27
3.1(a)
High Vacuum Coater
31
3.1(b)
Control panel of High Vacuum Coater
32
3.2
Internal part of High Vacuum Coater
32
xii
3.3
Direction of magnetic fields applied to samples
36
3.4
Edwards Auto 306 Evaporation Systems
37
3.5
Set up of annealing process
40
3.6
Graph of quartz temperature versus heater set point
41
3.7
The straight line used for thickness measurement
43
3.8(a)
3
Thickness of (Co/Cu) x 5 measured by Dektak
Surface Profiler
3.8(b)
Thickness of (Co/Cu) x 10 measure by Dektak3
Surface Profiler
3.8(c)
44
44
Thickness of (Co/Cu) x 15 measure by Dektak3
Surface Profiler
45
3.9
Magnetic fields applied in plane to sample
47
4.1
Magnetoresistance curve of Co /Cu /Co (6nm/
2.5nm/ 6nm) sandwich structures
4.2
49
Magnetoresistance curve for Co/Cu for 6 various
thickness of Co layer
51
4.3
Graph of MR% versus thickness
52
4.4
Graph of resistance versus film thickness of Co layer
53
4.5
Graph of resistance change versus film thickness
of Co layer
54
4.6
Effect of working pressure on MR%
56
4.7
Effect of working pressure on resistance of samples
57
4.8
Graph of resistance change versus working pressure
57
4.9
Effect of number of bilayers on MR%
59
4.10
Graph of resistance versus number of bilayers samples
60
4.11
Graph of resistance change versus number of bilayers
samples
60
4.12
Influence of annealing time on MR%
62
4.13
Graph of resistance versus annealing time
63
4.14
Graph of resistance change versus annealing time
63
4.15
Effect of annealing temperature as a function of MR%
in Co/Cu
4.16
65
MR% effect of annealing temperature as a function of
MR% in NiFe/Cu
65
xiii
4.17
Graph of resistance versus annealing temperature
66
4.18
Graph of resistance change versus annealing temperature
67
4.19
Graph of resistance of NiFe/Cu versus annealing
temperature (°C).
4.20
67
Effect of number bilayers of Co/Cu before and after
Annealing at 400°C towards MR%
69
4.21
Graph of resistance versus number bilayers of samples
70
4.22
Magnetoresistance curve of Co/Cu/Co (5.5 nm
/3.5 nm/5.5 nm) when magnetic fields applied along
and perpendicular to the sample
72
4.23
Easy and hard axis in Co hexagonal crystal lattice
72
4.24
Magnetoresistance Curve of Co/Cu/Co (5.5 nm/
3.5 nm/5.5 nm) with and without buffer layers (Cr) layer
4.25
Dependence of MR% on Cr buffer layer thickness in
Co/Cu/Co (5.5 nm/3.5 nm/5.5 nm) sandwich structures
4.26
74
75
Magnetoresistance curve of Cr/Co/Cu/Co (8 nm/5.5 nm
/3.5 nm/5.5 nm) when magnetic fields applied along and
perpendicular to the sample
4.27
7c
Magnetoresistance Curve of Co/Cu/Co (12 nm/2.5 nm
/12 nm) with different annealing time
77
4.28
Effect of annealing on Co/Cu/Co (12 nm/2.5 nm/12 nm)
77
4.29
Resistance of Co/Cu/Co (12 nm/2.5 nm/12 nm) in
different annealing time
4.30
78
Magnetoresistance Curve of Co/Cu/Co (12 nm/2.5 nm
/12 nm) prepared by RF sputtering and e-beam
method at two different working pressures.
80
xiv
LIST OF SYMBOLS
GMR
Gaint Magnetoresistance
MR
Magnetoresistance
MR%
Magnetoresistance ratios
SSF
Surface Spin-Flop
H
Magnetic field
M
Magnetization
µ0
Permeability of free space
β
Bohr magnetron
B
Magnetic induction
χ
Susceptibility
TN
Neel temperature
EF
Fermi Energy
n
Number of multilayers
ρ
Resistivity
Rmin
Resistance in maximum external
magnetic field
Rmax
Resistance in zero field
Rtotal
Total resistance
∆R
Distance between Rmax and Rmin
t
Thickness
tCo
Thickness of Co layers
RF
Radio frequency
e-beam
electron beam
xv
HVC
High Vacuum Coater
Auto 306
Edwards Auto 306 Evaporation Systems
Sccm
Standard cubic centimeter per minute
FTM
Film Thickness Monitor
Z value
Acoustic impedance
3
DEKTAK
Dektak3 Surface Profiler
LVDT
Linear Variable Differential
Transformer
RAM
Random access memory
MRAM
Magnetic RAM
FM-layers
Ferromagnetic layers
NM-layers
Non-magnetic spacer layers
P
Paramagnetic
F-mode
Ferromagnetic mod
AF-mode
Anti-ferromagnetic mode
α
Direction of magnetic field
Co
Cobalt
Cu
Copper
Cr
Chromium
Fe
Iron
Ni
Nickel
NiFe
Nickel Iron
GaAs
Gallium Arsenide
xvi
LIST OF APPENDICIES
APPENDIX NO.
A
DESCRIPTION
Temperature Uncertainty Calibration
PAGE
94