МММ / 01_Layer_Deposition_Thermal_Oxidation_and_CVD
.pdf
C* = Concentration in the solid oxide which would be in 11 equilibrium with the partial pressure in the bulk of the gas (PG)
C* = HPG
F1 = h(C*-C0) ; h = hG/HkT
Steady state:
F1 = F2 = F3
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k t |
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CO |
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S |
OX |
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kstox |
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RUPESH GUPTA |
Indo German Winter Academy |
12
Solution of Deal Grove Model
F F3 kS Ci |
N1 |
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t 2 |
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B t |
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2DC * |
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B C1 exp( |
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C2 exp( |
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kT |
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RUPESH GUPTA |
Indo German Winter Academy |
13
Rate Limiting
The slowest step out of oxidant diffusion and interface reaction will determine the overall process rate.
The resultant oxide growth rate is
tox2 Atox B t
RUPESH GUPTA |
Indo German Winter Academy |
14
Rate Limiting Steps
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tox |
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CG |
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CG |
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C* |
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CS C* |
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CS |
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Ci |
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Reaction Controlled |
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Diffusion Controlled |
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Regime |
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tox2 Bt |
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RUPESH GUPTA |
Indo German Winter Academy |
15
Common Oxidation Methods
Dry Oxidation
Si O2 SiO2
Slow Growth
For films up to 100-200 nm
Wet Oxidation
Si 2H2O SiO2 2H2
Faster growth due to high solubility of H2O in SiO2
(Higher B, B/A values )
For thicker films
RUPESH GUPTA |
Indo German Winter Academy |
16
Oxidation Equipment
Quartz |
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Resistance Heating
Flat temperature profile maintained using thermocouples
RUPESH GUPTA |
Indo German Winter Academy |
17
OUTLINE
Thermal Oxidation and Model
Factors Affecting Kinetics
o Future Trends: Oxidation
o CVD and Model
o Factors Affecting Kinetics
o Future Trends: CVD
RUPESH GUPTA |
Indo German Winter Academy |
18
Factors Affecting Growth Kinetics
Temperature
B C exp( |
E1 |
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B |
C |
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exp( |
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Crystal Orientation
Pressure
RUPESH GUPTA |
Indo German Winter Academy |
Crystal Orientation |
19 |
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(111)
Difference more
(110) |
obvious for thin |
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1.68 |
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oxides |
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(100) |
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orientation |
Most ICs made with (100) Si |
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RUPESH GUPTA |
Indo German Winter Academy |
Pressure 20
Increase in oxidation rate even at low temperatures
RUPESH GUPTA |
Indo German Winter Academy |