P5000 RIE/Processes/NITRIDE 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 NITRIDE BKM recipe is a general recipe for etching silicon nitride films on the P5000 RIE/Processes. It has a fast etch rate (4000 Å/min) and reasonable selectivity to photoresist and polysilicon, but little selectivity to silicon oxide. This recipe can be run in chambers A or B depending on the sample's material requirements.

Warning:

This process has been minimally characterized. Use caution when running this for the first time.

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
Stoichiometric nitride	4200 Å/min
Low stress nitride	3800 Å/min
Thermal oxide	3800 Å/min
HTO	unknown
LTO	unknown
PECVD oxide	unknown
Polysilicon	1900 Å/min
SPR 220	2800 Å/min

Uniformity

• Within-wafer uniformity: <4% (10 mm edge exclusion)
  • Etch rate drops significantly in the outer 5 mm and often leaves a residue
• Wafer-to-wafer uniformity: <2%

Mask selectivity

Mask selectivity of silicon nitride (stoichiometric) 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	1.5:1
Polysilicon	2.2:1
Thermal oxide	1.2:1
Low stress nitride	1.1:1

Sidewall profile

Sidewall angle has not been tested.

Parameters

Parameter	STAB	ETCH
Chamber Selection	A or B
Step end control	By Time
Maximum step time	20 s
Endpoint selection	No Endpoint
Pressure	Servo 200 mTorr
Pressure ramp rate	0 mTorr/Second
RF Power	0 W	750 W
RF match, mode	Auto, B-to-B
RF tune setpoint	0.0 V
DC Bias Limit	-1000 to 0 V
Magnetic field	20 G
Ar Flow	75 sccm
CHF3 Flow	12 sccm
CF4 Flow	20 sccm
O2 Flow	10 sccm

Limitations

Etch time

Etch rate vs time has not been tested.

Loading

Etch loading has not been tested.

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 100 nm. A post etch ash in the YES Plasma Stripper using Recipe 2 is highly recommended.

Qualification

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