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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.
| About this Process | |
|---|---|
| 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 |
| Warning: | This process has been minimally characterized. Use caution when running this for the first time. |
Contents
Procedure
- Review the material restrictions for each chamber and choose the appropriate one for the application.
- Follow the procedure outlined in the SOP.
- Open the
OXIDE BKMProcess Program. - Edit the time in either
ETCH A OnlyorETCH B Onlydepending on the chamber used. - Select either
OXIDE A BKMorOXIDE B BKMfrom 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.
| 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.
 | This process has incomplete or incorrect characterization data. |
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.