Thermal oxidation (Thermal processing) is a process used to grow a thin layer of oxide (SiO2) on silicon semiconductor wafers.
|Equipment||List of Thermal processing equipment|
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Tempress S3T1 - Dry Oxide
The Tempress S3T1 furnace tube is a CMOS clean horizontal furnace tube that is used for growing dry oxide.
Tempress S3T2- Wet Oxide
The Tempress S3T2 furnace tube is a CMOS clean horizontal furnace tube that is used for growing dry/wet/dry oxide.
Tempress S5T2 - Phosphorous Anneal Oxidation
The Tempress S5T2 furnace tube is a CMOS clean horizontal furnace tube that is used for growing dry oxide, on heavily doped phosphorous wafers.
Tempress S5T4 - Boron Anneal Oxidation
The Tempress S5T4 furnace tube is a CMOS clean horizontal furnace tube that is used for growing dry oxide, on heavily doped boron wafers.
Tempress S6T1 - Annealing
The Tempress S6T1 furnace tube is a metals allowed horizontal furnace tube that can be used for growing dry oxide.
- Dry oxide
- Wet oxide
Method of operation
The thermal oxidation process is performed in a hot walled quartz reactor, called a furnace tube. An oxidizing gas (oxygen) or steam (oxygen + hydrogen) is injected into the reactor which is heated to a high temperature, typically 800° to 1200°C. The high temperature allows oxygen to diffuse into the silicon substrate and react with it, forming silicon dioxide. These reaction are diffusion limited and growth decreases exponentially with time limiting the practical thickness that can be grown.
Dry Oxidation happens in the presence of oxygen. The O2 molecule reacts with the Si on the surface of the wafer to create SiO2. For dry oxide films the practical thickness limit is 3000 Å.
Wet oxidation uses clean steam, H2O. Hence the name wet oxide. In LNF Tempress furnaces, the steam is made H2 and O2 sent through a pyrolyzer and converted into H2O. The H2O molecule is smaller than the O2 molecule and diffuses through the silicon dioxide layer faster. This allows for the growth of thicker films. A 2um thermal silicon dixoide film is the practical limit in these tools.
Parameters that affect thermal oxidation are time, and temperature.
Examples of processing applications
Thermally grown silicon dioxide is very high quality compared to silicon dioxide deposited by other techniques. It is dense, exhibits high breakdown voltage, and can be uniform and free from impurities and pinhole defects. Thermal oxide is used for applications where these properties are needed, e.g. in MOS transistor gates, MOS capacitors, and field oxides.
Complete tool list