Specific Process Knowledge/Etch/Etching of Silicon Nitride

Silicon nitride can be etched using either wet chemistry or dry etch equipment. Wet chemistry is mainly used to remove all the nitride on the surface (backside and frontside) of a wafer. Dry etching etches one side at a time and can be used to etch structures with several masking materials.

• Wet Silicon Nitride Etch
• Etch of Silicon Nitride using RIE

Comparison of wet Silicon Nitride etch and RIE etch for etching of Silicon Nitride

	Wet Silicon Nitride etch	RIE
What is it good for:	Isotropic etch Well suited for removing all nitride on a wafer surface (nitride strip) without a mask. High selctivity Si3N4/Si (>100) and Si3N4/SiO2 (>20) @ 180 C.	Anisotropic etch: vertical sidewalls
Possible masking materials:	Silicon Oxide	Photoresist Silicon Oxide Aluminium Chromium (ONLY RIE2!)
Etch rate	Stoichiometric Silicon Nitride @ 180 oC: 84 Å/min Stoichiometric Silicon Nitride @ 160 oC: 60 Å/min	Typically 40-50 nm/min can be increased or decreased by using other recipe parameters.
Process volume	25 wafers at a time	1 wafer at a time
Size of substrate	4" wafers	4" wafers or smaller pieces