Specific Process Knowledge/Thermal Process/Oxidation

Oxidation

At Danchip we have six furnaces for oxidation: A1,A3,C1,C2,C3 and D1. Oxidation can take place either by a dry process or a wet process. The film quality of dry oxide is better than for wet oxide with regards to density and dielectric constant. If the film quality for the wet oxide is acceptable then the thickness and the time it takes to grow the oxide often decides if a dry or wet oxidation is chosen.

• Dry oxide is used from 5nm - 200nm. Can be grown in furnaces: A1,A3,C1,C2,C3.
• Wet oxide with O$_{2}$ and H$_{2}$ can be grown in furnace: A1,A3.
• Wet oxide with H$_{2}$O in a bubbler can be grown in furnaces: C1,C2,C3,D1.

Comparison of the six oxidation furnaces

'	A1 Boron drive-in	A3 Phosphorous drive-in	C1 Anneal oxide	C2 Gate oxide	C3 Anneal bond	D1 APOX	Noble
General description	Drive-in of boron deposited in the boron pre-dep furnace(A2) or drive-in of ion implanted boron. Can also be used for dry and wet oxidation.	Drive-in of phosphorous deposited in the phosphorous pre-dep furnace(A2) or drive-in of ion implanted phosphorous. Can also be used for dry and wet oxidation.	Oxidation and annealing of wafers from the B-stack and PECVD1.	Oxidation of gate-oxide and other especially clean oxides. At the moment also used for general oxidation of 6" wafers.	Oxidation and annealing of wafers from NIL.	Oxidation of very thick oxides	Oxidation and annealing for all materials.
Dry oxidation	x	x	x	x(with special permission)	x	.	x (after request)
wet oxidation with torch (H$_{2}$+O$_{2}$)	x	x	.	.	.	.	.
Wet oxidation with bubbler (water steam + N$_{2}$)	.	.	x	x (with special permission)	x	x	.
Process temperature [ oC ]	800-1150	800-1150	800-1150	800-1150	800-1150	1150	.
Cleanliness of dry oxide (rated 1-5, 1 is best)	2	2	3	1	4	.	>5
Cleanliness of wet oxide (rated 1-4, 1 is best)	1	1	3	2	4	3	.
Batch size	max. 30 wafers of 4" or 2"	max. 30 4" wafers or 2" wafers	max. 30 wafers of 6",4" or 2"	max. 30 4" wafers or 2" wafers	max. 30 4" wafers or 2" wafers	max. 200 4"	?
Which wafers are allowed to enter the furnace:	A1 Boron drive-in	A3 Phosphorous drive-in	C1 Anneal oxide	C2 Gate oxide	C3 Anneal bond	D1 APOX	Noble
New clean* Si wafers 4" (6" in C1)	x	x	x	x (with special permission)	x	x	x
RCA clean** Si wafers with no history of Metals on	x	x	x	x (with special permission)	x	.	x
From Predep furnace directly (e.g. incl. Predep HF**)	From A2	From A4	x	.	x	.	x
Wafers directly from PECVD1	.	.	x	.	x	.	x
Wafers directly from NIL bonding	.	.	.	.	x	.	x
All materials must enter the furnace	.	.	.	.	.	.	x

*New clean: only right from the new clean box. It is not allowed to put them in another box first.

**These wafers must be placed in a "transport box from RCA to furnace" using the RCA carrier when doing RCA or the pre-dep carrier after pre-dep.

Oxidation curves

Generic calculator for wet/dry oxide thickness calculation

The following links give an approximate oxide time/thickness based on a general formula.

• Know thickness - want time

• Know time - want thickness

The curves below are based on measurements in our specific furnaces and give more accurate results.

A1 Furnace <100>-Si Wet Oxidation

A3 Furnace <100>-Si Wet Oxidation

Dry Oxidation on <100> and <111> wafer

• Dry oxidation
• 
  Dry oxide on <100> wafer
• 
  Dry oxide on <111> wafer