Properties of
SiO2 and Si3N4 at 300K
Dielectric layers
are just as indispensable to integrated circuit fabrication as the
semiconductor itself and interconnecting metallization. Dielectric
layers are used primarily to
isolate
active
circuits from each other and to provide mechanical and chemical
protection
to the device itself. Dielectric layers are also widely used in
the fabrication of components essential to circuit functionality such as
capacitors and MOS transistors. Lastly, dielectric layers are also
used as
masking
materials during wafer fabrication itself.
Two
dielectric workhorses in device fabrication are the
silicon
dioxide (SiO2)
and the
silicon
nitride (Si3N4).
Aside from being used for masking purposes, the former is extensively
used in electrical isolation and as capacitor dielectric and MOS gate
oxide while the latter is widely used as the final
glassivation
layer of the die. The properties of SiO2 and Si3N4
at 300 deg K are presented in Table 1.
Table 1. Properties of
Silicon Dioxide (SiO2) and Silicon Nitride (Si3N4)
at 300K
Properties |
SiO2 |
Si3N4 |
Structure |
Amorphous |
Amorphous |
Melting
Point (deg C) |
approx.
1600 |
--- |
Density
(g/cm3) |
2.2 |
3.1 |
Refractive Index |
1.46 |
2.05 |
Dielectric Constant |
3.9 |
7.5 |
Dielectric Strength (V/cm) |
107 |
107 |
Infrared
Absorption Band (µm) |
9.3 |
11.5 -
12.0 |
Energy
Gap at 300K (eV) |
9 |
approx.
5.0 |
Linear
Coefficient of Thermal Expansion,
ΔL/L/ΔT
(1/deg C) |
5 x 10-7 |
--- |
Thermal
Conductivity at 300 K
(W/cm-degK) |
0.014 |
--- |
DC
Resistivity at 25 C (ohm-cm) |
1014
- 1016 |
approx.
1014 |
DC
Resistivity at 500C (ohm-cm) |
--- |
2 x 1013 |
Etch
Rate in Buffered HF (angstroms/min) |
1000 |
5 - 10 |
LINKS:
Dielectric;
Glassivation;
Thermal Oxidation; Si, Ge,
GaAs Properties;
What
is a semiconductor?;
IC Manufacturing
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