Effect of Post Metallization Annealing for La 2 O 3 Thin Film

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4.2 Considerations ions about an Occurrence and a Recovery of VFBVShiftBy some conditions of PMA, VFB shift toward negative side wascompletely and dramatically recovered. However, not only the mechanismof this recovery but also the mechanism of VFB shift toward negative side hasnot clarified yet. From the results we have obtained, some assumptions forthis phenomenon can be enumerated and some of them will be cited in thepages that follow.It can be considered that there are principally two possibilities tobring about the VFB shift toward negative side. The one is the absorption ofmoisture ambience into rare earth oxides thin films. It is well known thatall of rare earth oxides have the property of absorbing readily moisture, andthis absorption could make the rare earth oxides change into hydroxide asshown in Figure 4-1.H 2 OH 2 OLn 2 O 3Ln(OH) 3+3Silicon SubstrateSilicon SubstrateLn 2 O 3 +3H 2 O 2La(OH)3+3 +3(OH) -Figure 4-1: Schematic illustration of hydroxylation mechanismThe presence of (OH) - ion place of O 2- site could become a primary factor ofthe VFB shift toward negative side.Another is the oxygen deficiency. If the oxygen leaves from rareearth oxides films by some reasons, stoichiometry can not be preserved, andthat result in the generation of positive charge in films. Three possibilitiescan be considered when oxygen vacancies occur as shown in Figure4-2. Theone is a moment when rare earth oxides are deposited on silicon substratesin ultra high vacuum. This presumption seems to be consistent because theVFB shift toward negative side was observed in as-deposited sample in my- 94 -
esults. The second is the time when the annealing process is performed.This one also seems to be consistent because larger VFB shift toward negativeside than as-deposited sample was also observed in PDA sample in myresults. The third is the time when the aluminum upper electrodes areevaporated on the rare earth oxides thin films. It is well known thataluminum has the property of the strong affinity with oxygen and thisproperty worked on this result. In other words, aluminum inhales theoxygen in rare earth oxides at a moment aluminum cone into contact withrare earth oxides thin films. This assumption also seems to be reasonablebecause the value of VFB shift in the case of aluminum upper electrodes waslarger than the one in the case of platinum upper electrodes.O O AluminumSilicon SubstrateLn 2O 4+ or Ln 2O2+2 Ln 2O2+2 Ln 2O 4+Ln 2 O 4+ or Ln 2 O2+2 Silicon SubstrateO O O OLn 2 O 4+ or Ln 2 O2+2 Silicon SubstrateDeposition ProcessAnnealing ProcessContact with AluminumFigure 4-2: Schematic illustrations of oxygen vacancies mechanismThen, the reason why VFB shift toward negative side recovered byPMA with aluminum must be made clear. There are also two possibilitieshere. One is the effect of covering surface of rare earth oxides films beforethe annealing process. That seems to prevent oxygen from getting away tooutside. However, this assumption is leaving one question. If thisassumption is correct, PMA with all kind of metal upper electrodes issupposed to have an effect on the suppression of VFB shift toward negativeside. Actually, however, PMA with gold upper electrodes did not only yield- 95 -
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CONTENTSChapter 1 Introduction-----
Page 5 and 6:
Chapter 1Introduction-1 -
Page 7 and 8:
Miniaturization with a scaling fact
Page 9 and 10:
Table 1-2: Electrical Properties fo
Page 11 and 12:
LSI fabrication, such as activation
Page 13 and 14:
Table 1-4 shows the properties of t
Page 15 and 16:
1.3 Purpose of My StudyIt is consid
Page 17 and 18:
Chapter 2FabricationAndCharacteriza
Page 19 and 20:
2.1.1 1 Wet Cleaning Method of Sili
Page 21 and 22:
2.1.3 Molecular Beam Deposition (MB
Page 23 and 24:
2.1.4 Rapid Thermal Annealing (RTA)
Page 25 and 26:
2.1.5 Vacuum Evaporation MethodAlum
Page 27 and 28:
1 1 1 t 1 kTC = C + C = εε+ q ε
Page 29 and 30:
In C-V curve, the two type of hyste
Page 31 and 32:
2.2.2 Leakage Current Density-Volta
Page 33 and 34:
2.2.3 Ellipsometry MethodEllipsomet
Page 35 and 36:
3.1 IntroductionIn this chapter, th
Page 37 and 38:
3.3 Electrical Characteristics in t
Page 39 and 40:
Capacitance (µF/cm 2 )21Al/La O /
Page 41 and 42:
Current Density [A/cm 2 ]10 2 10 1A
Page 43 and 44:
3.3.2 Effects of Chemical Oxidation
Page 45 and 46:
3.3.3 Dependence on the Annealing T
Page 47 and 48: Capacitance (µF/cm 2 )210Al_As-dep
Page 49 and 50: Capacitance (µF/cm 2 )210Al/La O /
Page 51 and 52: Al/La O / n-Si(100)/Al2 3 250 o C d
Page 53 and 54: As the summary of this sub-section,
Page 55 and 56: Current Density[A/cm 10 2 PDAAs-de
Page 57 and 58: Equivalent Oxide thickness [nm]32.5
Page 59 and 60: Figure 3-29 shows the plots of VFB
Page 61 and 62: 3.4.1.4 Dependence on the Ambience
Page 63 and 64: V Shift [V]FB0.60.40.20-0.2-0.4-0.6
Page 65 and 66: Capacitance (µF/cm 2 )21PDA 300 o
Page 67 and 68: case of aluminum electrodes as comp
Page 69 and 70: 3.4.2.2 Effects of Chemical Oxidati
Page 71 and 72: V Shift [V]FB-0.4-0.5-0.6-0.7-0.8-0
Page 73 and 74: 2.62.5EOT [nm]2.42.3As-depo.2.2PDA_
Page 75 and 76: Capacitance (µF/cm 2 )21Au_PMA_N2_
Page 77 and 78: 3.4.2.5 The comparison with the cas
Page 79 and 80: 3.4.3 Effects of PMA for Platinum U
Page 81 and 82: 4Pt/La O / n-Si(100)/Al2 3EOT [nm]3
Page 83 and 84: EOT [nm]2.82.62.42.221.81.6Pt/La O
Page 85 and 86: On the other hand, there was almost
Page 87 and 88: V Shift [V]FB0.2Pt/La O / n-Si(100)
Page 89 and 90: Capacitance (µF/cm 2 )21Pt/La O /
Page 91 and 92: Capacitance (µF/cm 2 )21Pt_As-depo
Page 93 and 94: Chapter 4Conclusions- 89 -
Page 95 and 96: 4.1.2 Summary of the Investigation
Page 97: Table 4-2: Summary of my investigat
Page 101 and 102: AluminumAl 2 O 3 or LaAlO 3Al Al Al
Page 103 and 104: AcknowledgementIn the first place,
Page 105 and 106: Reference[1] International Technolo
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Effect of Post Metallization Annealing for La 2 O 3 Thin Film

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