P5000 RIE/Processes/OXIDE BKM

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About this Process
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Process Details
Equipment	P5000 RIE
Technology	RIE
Material	SiO2
Mask Materials	PR, Polysilicon
Gases Used	Ar, CHF3, CF4
Date Modified	4/10/2014
Authored By	AMAT, Kevin Owen

The OXIDE BKM recipe is a general recipe for etching silicon dioxide films on the P5000 RIE/Processes. It has a fast etch rate (3800 Å/min) and reasonable selectivity to photoresist and polysilicon, but low selectivity to silicon nitride. This recipe can be run in chambers A or B depending on the sample's material requirements.

Procedure

1. Review the material restrictions for each chamber and choose the appropriate one for the application.
2. Follow the procedure outlined in the SOP.
3. Open the OXIDE BKM Process Program.
4. Edit the time in either ETCH A Only or ETCH B Only depending on the chamber used.
5. Select either OXIDE A BKM or OXIDE B BKM from Wafer Lot Names.

Characterization

Etch rate

Bulk etch rates for various oxides, nitrides, and masking materials are shown below. High aspect ratio (narrow) trenches will etch slower.

Material	Etch rate
Thermal oxide	3800 Å/min
HTO	3950 Å/min
LTO	4000 Å/min
PECVD oxide	1300 Å/min
Stoichiometric nitride	unknown
Low stress nitride	1300 Å/min
Polysilicon	350 Å/min
SPR 220	1500 Å/min

Uniformity

• Within-wafer uniformity: <4% (3 mm edge exclusion)
  • Etch rate is faster at the edge
• Wafer-to-wafer uniformity: <2%

Mask selectivity

Mask selectivity of Thermal oxide to a selection of materials is shown below. Selectivity for your material can be calculated using the etch rates listed above.

Mask selectivity is based on bulk material etch rates (above). Selectivity will vary slightly with feature size.

Material	Etch rate
SPR 220	2.53:1
Polysilicon	10.86:1
Stoichiometric nitride	unknown
Low stress nitride	2.92:1

Sidewall profile

Warning:

not verified

• 78 degrees - low aspect ratio features
• 87 degress - high aspect ratio, submicron features

Parameters

Parameter	Stabilization	Etch
Power	0 W	750 W
Magnetic field	40 G	40 G
Pressure	250 mTorr	250 mTorr
Argon Flow	75 sccm	75 sccm
CHF3 Flow	25 sccm	25 sccm
CF4 Flow	5 sccm	5 sccm
Time	20 s

Limitations

Etch time

Etch rate is very linear, tested down to 5 seconds. Maximum etch time is mask dependent, have demonstrated up to 4 µm etch depth.

Loading

This etch is not significantly load dependent.

Fluorocarbon deposition

This etch deposits fluorocarbon as its primary selectivity mechanism. Thickness of fluorocarbon on sidewalls increases as feature size increases and may be as thick as 100nm. A post etch ash in the YES Plasma Stripper using Recipe 2 is highly recommended.

Qualification

The bulk etch rate of thermal oxide is verified occasionally by running the recipe for 2 minutes.