CV Measurement

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C-V Measurement

• Andreas Schön

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Outline

• Basics
• MIS structure
• Energy band diagram
• Surface charge
• Capacitance-Voltage Curve
• Real MOS
• Influences on the C-V Measurement

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MIS Structure
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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Energy Band Diagram
Energy band diagram for an ideal MIS diode at
V0 (p-typeSemiconductor)
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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Energy Band Diagram
Vlt0
Vgt0
Pictures taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
accumulation
depletion
inversion
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Surface Charge
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Surface Charge
Calculated dependence of surface charge density
on the surface potential
Picture taken from M. Shur, Physics of
Semiconductor Devices, 1990
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Capacitance-Voltage Curve
Picture taken from M. Shur, Physics of
Semiconductor Devices, 1990
Calculated dependance of gate capacitance on the
gate voltage for different values of doping
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Capacitance-Voltage Curve
Picture taken from M. Shur, Physics of
Semiconductor Devices, 1990
Calculated dependance of gate capacitance on the
gate voltage at different frequencies
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Capacitance-Voltage Curve
Picture taken from M. Shur, Physics of
Semiconductor Devices, 1990
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Thickness Dependence
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
Computed ideal MIS C-V curve for various oxide
thicknesses
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Real Measurement
Picture taken from M. Shur, Physics of
Semiconductor Devices, 1990
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Influences on the C-V curve

• Interface Trapped Charge
• Oxide Charges
• Fixed Oxide Charge
• Oxide Trapped Charge
• Mobile Ionic Charge
• Work Function Difference
• External Influence
• Carrier Transport in Insulating Films

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Conduction Processes in Insulators
Table taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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MOS-Structures
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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Interface Trapped Charge
Equivalent circuit
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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Interface Trapped Charge
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
Capacitance stretch-out due to interface trapped
charges
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Interface Trapped Charge
Interface trap density in thermally oxidized
silicon
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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MOS-Structures
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
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Fixed Oxide Charge
Picture taken from S. M. Sze, Physics of
Semiconductor Devices 2nd Edition, 1981
C-V shift due to fixed oxide charge
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Outlook
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