Specific Process Knowledge/Thermal Process/A4 Phosphor Pre-dep furnace

A4 Furnace Boron pre-dep

A1 Boron drive in furnace: positioned in cleanroom 2

A4 is a furnace to dope Si wafers with Phosphor to make conductive lanes, etch stops etc. The doping source is Phosphoryl chloride (commonly called phosphorus oxychloride) is a colourless liquid with the formula POCL3.

A4 is the lowest furnace tube in the A-stack positioned in cleanroom 2. The A-stack together with furnace C1 are the cleanest of all our furnaces. Please be aware of which substrates are allowed to enter this furnace. Check the cross contamination chart. If you are in doubt, please ask one from the furnace team.

Overview of the performance of the Phosphor pre-dep furnace and some process related parameters

Purpose	Doping of Phosphor
Performance
Process parameter range	Process Temperature	900-1150 ^oC
	Process pressure	1 atm
	Gasses on the system	POCL $_{3}$
Substrates	Batch size	1-30 4" wafer (or 2" wafers) per run
Substrates	Substrate material allowed	Silicon wafers (new from the box or RCA cleaned) In doubt: look at the cross contamination sheet or ask one from the furnace team
Material NOT allowed	wafers must NOT have been exposed to metal prior to A4 wafers must NOT have been stored in dirty boxes (i.e. boxes that has contained wafers with metal)