МММ / 01_Layer_Deposition_Thermal_Oxidation_and_CVD

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Layer Deposition:

Thermal Oxidation and CVD

Rupesh Gupta

IIT Delhi

Supervisor: Dr. Chacko Jacob

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OUTLINE

Thermal Oxidation and Model

o Factors Affecting Kinetics

o Future Trends: Oxidation

o CVD and Model

o Factors Affecting Kinetics

o Future Trends: CVD

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Silicon Oxide

Si is unique as its surface can be easily passivated with oxide layer.

SiO2 layers

•adhere well

•block diffusion of impurities

•can be easily patterned and etched

•are excellent insulators (gate dielectrics)

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A Comparison

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Thermal Oxidation

Oxidation process occurs at Si/SiO2 interface by inward diffusion of oxidant.

New interface is constantly forming and moving downward into the Si substrate.

Si-Si bonds broken, Si-O bonds formed. Process involves volume expansion because of room needed for oxygen atoms.

O2 / H2O

Ambient

SiO2

Flat and Narrow

Transition Region

Si O2 SiO2

Silicon

Si 2H2O SiO2 2H2

Compressive Stress

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Modeling Oxidation

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The Deal Grove Model

Showed that over a wide range of conditions, the growth followed a linear parabolic law.

Still used today to model planar oxidation.

Cannot explain kinetics in

•shaped surfaces

•mixed ambients

•very thin oxides < 20nm

•oxides grown on heavily doped substrates

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Rigorous Solution

Henry’s Law:

C0 = HPS PS = partial pressure of oxidant

Use:

CS = N/V and PV = NkT

C0 = H (kT.CS) => CS = C0/HkT