Specific Process Knowledge/Etch/Etching of Silicon Nitride/Etch of Silicon Nitride using RIE

For a general introduction to RIE at Danchip see RIE (Reactive Ion Etch)

Etching of silicon nitride using RIE can be done with several recipes. It can be etched by our standard silicon etch recipe: OH_PolyA which is based on SF6. It can also be etched using the recipe 1Nitride which is based on CHF3. The difference of these two etches has not been investigate in details. Look in the table below to see what we know

Some RIE recipes for etching of silicon nitride:

Name	SF6 flow	O2 flow	CHF3 flow	N2 flow	Pressure	Power
OH_PolyA	32 sccm	8 sccm			80 mTorr	30 W
BGE-NITR			8 sccm	32 sccm	38 mTorr	50 W

Expected result using the above RIE recipes for etching of silicon nitride:

You should be aware that the result can deviate quit a lot from what is written here depending on ex. the mask loading.

Name	Etch rate	Anisotropy	Selectivity to resist	Selectivity to oxide	Selectivity to silicon	Comments
OH_PolyA	0.05 µm/min	?	~1:1	~1:2-3	~1:13
BGE-NITR	0.04 µm/min	Expected to be very anisotropic - not verified	?	~1:1	~1:1	Especially good to remove nitride on one side of the wafer avoiding getting anything etched on the back side.