Specific Process Knowledge/Thermal Process/A3 Phosphor Drive-in furnace

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Phosphorus Drive-in furnace (A3)

Phosphorus Drive-in furnace (A3). Positioned in cleanroom B-1/ Photo: DTU Nanolab internal

The Phosphorus Drive-in furnace (A3) is a Tempress horizontal furnace for thermal oxidation of silicon wafers. Furthermore, the furnace is used for phosphorus drive-in afte pre-deposition/doping or after boron ion implantation.

The furnace is mostly used for wet and dry thermal oxidation of silicon wafers. The oxidation recipes are named e.g. "WET1000" and "DRY1000", where "WET" or "DRY" indicates whether it is a wet or dry oxidation process, and the number indicates the oxidation temperature.

The purpose of phosphorus doping is to make conductive structures, etch stop layers etc. After a phosphorus pre-deposition/doping or ion implantation process, a drive-in process with or without an oxide growth is done in the furnace. The phosphorus pre-deposition is normally done in the Phosphorus Pre-dep (A4) furnace, and ion implantation have to be done elsewhere.

The Phosphorus Drive-in furnace is the third 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. Please be aware of that all wafers have to be RCA cleaned before they enter the furnace (except wafers coming form the Phosphorus Pre-dep furnace that have been BHF etched in the dedicated bath in the RCA bench), and please check the cross contamination information in LabManager, before you use the furnace.

The user manual, quality control instruction and results, technical information and contact information can be found in LabManager:

Phosphorus Drive-in furnace (A3)

Process knowledge

• Oxidation: look at the Oxidation page
• Phosphorus drive-in: look at the Dope with Phosphorus page

Quality Control - Recipe Parameters and Limits

Quality Control (QC) for the processes "Wet1050" and "Dry1050"

The QC procedure for Phosphorus drive-in furnace (A3) The newest QC data for wet and dry oxide QC Recipe: WET1050 DRY1050 H2 flow 3 slm 0 slm O2 flow 2 slm 5 slm Temperature 1050 oC 1050 oC Oxidation time 30 min 100 min QC limits Thickness Non-uniformity (both over a single wafer and over the boat) DRY1050 110-116 nm 3 % WET1050 305-321 nm 5 % Numbers from March 2020

Overview of the performance of the phosphorus drive-in furnace and some process related parameters

Purpose	Thermal oxidation of Si wafers Driving-in pre-deposited or ion-implanted phosphorus	Thermal oxidation: Dry oxidation using O2 Wet oxidation using H2O vapour Driving-in pre-deposited or ion-implanted phosphorus Dry or wet oxidation recipes are normally used for this purpose
Performance	Film thickness	Dry oxide: ~ 0 nm - 300 nm (it takes too long to grow a thicker oxide) Wet oxide: ~ 0 nm - 3 µm (23 hours wet oxidation at 1100 oC for Si[100] wafers)
Process parameter range	Process Temperature	800 oC - 1150 oC
	Process pressure	1 atm (no vacuum)
	Gasses on the system	N2 O2 H2 (in a torch, H2 and O2 burns into H2O for wet oxidation)
Substrates	Batch size	1-30 100 mm wafers (or 50 mm wafers) per run
	Substrate materials allowed	Silicon wafers (RCA cleaned) Wafers coming from the Phosphorus Pre-dep furnace that have been BHF etched in the dedicated bath in the RCA bench can go directly into the furnace