Specific Process Knowledge/Thermal Process/A4 Phosphor Pre-dep furnace: Difference between revisions
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''This page is written by DTU Nanolab internal'' | ''This page is written by DTU Nanolab internal'' | ||
[[Category: Equipment |Thermal A4]] | [[index.php?title=Category:Equipment|Thermal A4]] | ||
[[Category: Thermal process|Furnace]] | [[index.php?title=Category:Thermal process|Furnace]] | ||
[[Category: Furnaces|A4]] | [[index.php?title=Category:Furnaces|A4]] | ||
==Phosphorus Pre-dep furnace (A4)== | ==Phosphorus Pre-dep furnace (A4)== | ||
[[Image:A4.JPG|thumb|300x300px|Phosphorus Pre-dep furnace (A4). Positioned in cleanroom B-1/ Photo: DTU Nanolab internal]] | [[Image:A4.JPG|thumb|300x300px|Phosphorus Pre-dep furnace (A4). Positioned in cleanroom B-1/ Photo: DTU Nanolab internal]] | ||
The Phosphorus Pre-dep furnace (A4) is used to dope Si wafers with phosphorus to | The Phosphorus Pre-dep furnace (A4) is mainly used to dope Si wafers with phosphorus. The furnace can also be used for dry oxidation of Si wafers. | ||
The A4 furnace is the lowest furnace tube in the A-stack positioned in cleanroom B-1. The furnaces in the A-stack are the cleanest of all furnaces in the cleanroom. Be aware of that all wafers (including new wafers) have to be RCA cleaned before they enter the furnace, and please check the cross contamination information in LabManager before you use the furnace. | |||
'''Phosphorous doping of Si wafers''' | |||
Phosphorus is an n-type dopant that can be diffused into Si wafers (normally p-type) to form an n-type layer near the wafer surface. The doping will change the electrical properties of the silicon, so that for instance conductive structures, etch stop layers can be made. | |||
The phosphorus doping source is phosphoryl chloride (commonly called phosphorus oxychloride) which a colourless liquid with the chemical formula POCl<sub>3</sub>. Furthermore, an oxygen (O<sub>2</sub>) flow is needed for the doping process.The POCl<sub>3</sub> is stored in a bubbler, and nitrogen (N<sub>2</sub>) gas is flowing though the bubbler. | |||
There are two primary steps within a phosphorus doping/pre-deposition process: A pre-deposition step and a diffusion/drive-in step (not a drive-in process). The final profile of the doping concentration near the wafer surface depends on the pre-deposition and the drive-in temperatures and times. | |||
After the phosphorous pre-deposition process, a phosphorus doped silicon oxide layer, i.e. a phosphosilicate glass layer, remains in the surface of the wafers. This layer can be removed by hydroflouric acid (HF) in the BHF etch bath at the RCA cleaning bench. When the phosphosilicate glass layer has been removed, a drive-in process (an annealing or a thermal oxidation) is done. | |||
Normally, only the phosphorous doping/pre-deposition is done the Phosphorus Pre-dep furnace (A4), while the drive-in process is done in the A3 Phosphorus Drive-in furnace. | |||
'''Dry oxidation of Si wafers (or phosphorus phase layers created in the phosphorus doping/pre-deposition process)''' | |||
For dry the dry oxidation processes, oxygen (O<sub>2</sub>) is used as oxidant. | |||