Silicon Dioxide (SiO2) and Silicon Nitride (Si3N4) Properties

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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