This document discusses oxidation of silicon and the thermal oxidation process. It describes how silicon is commonly oxidized using thermal oxidation in a furnace between 800-1200°C in the presence of oxygen or water vapor. Thermal oxidation grows either a dry oxide layer using oxygen or a wet oxide layer using water vapor, with wet oxidation growing faster but introducing more defects. Thermal oxidation is a key process in silicon integrated circuit fabrication for growing silicon dioxide layers.

1. by
Louis Anitha,

2.  Introduction
 Oxidation of silicon
 Classification of oxidation process
 Advantages and disadvantages
 Application

3.  Semiconductor can be oxidized by various methods, including
Thermal oxidation, electrochemical anodization and plasma
enhanced chemical vapour deposition.
 Among these thermal oxidation is most commonly used.
 It is a key process in modern silicon IC technology.

4.  The most widely used technique to grow SiO₂ on
silicon is Thermal oxidation.
 This is usually carried out in an open tube quartz
furnace at atmospheric pressure between 800-1200℃.

5.  When a silicon heated in a furnace at a high temperature in the
presence of oxygen gas. This oxidation process carried out in
the furnace which is called an oxidation Furnace.
 Schematic of an oxidation Furnace :

6. Pictorial description of oxidation process
Si Wafer Si Wafer
Si Wafer
O₂ or H₂O
800-1200℃
0.0.1-1.0μm SiO₂

7. Classification of oxidation process:
There are two type of oxidation process used in
fabrication namely,
 Dry Oxidation
 Wet Oxidation

8.  Growth of SiO₂ using O₂ is referred to as
Dry oxidation.
 In Dry oxidation –oxygen is passed through the tube
where it react with silicon to form SiO₂
 Reaction:
Si +O₂ SiO₂

9. Advantage:
 Oxide layer are very uniform.
 Relatively few defects exist at oxide interface
Disadvantage:
 Dry oxide grows slowly.

10.  High purity de-ionised water, kept in a quartz bubbler at inlet
of the furnace, is heated to a temperature close to its boiling
point
 High purity oxygen or nitrogen is passed through it so that the
gas flow into furnace is saturated with water vapour.
 Water then acts as the oxidizing agent and the oxidation
reaction is given by
Si +2H₂O SiO₂ +2H₂

11. Advantage:
Wet oxide grows fast.
Disadvantage:
Hydrogen atom liberated by decomposition of wter
molecules produce perfections that may degrade the oxides
quality.

12.  The oxidation rate of wet oxidation is significantly higher
than that of dry oxidation hence, whenever thickness oxide is
needed, wet oxidation process is used.
 Wet oxidation –Thick oxide layer
 Dry oxidation-Thin oxide layer

13. THANK YOU