Specific Process Knowledge/Etch/Wet Silicon Oxide Etch (BHF)

Wet Silicon Oxide Etch (BHF and SIO Etch (wetting agent))

Silicon oxide can be etched using HF. At Danchip it is mainly used in a buffered version BHF (premixed). The BHF has a more stabile etch rate and more gentle to photoresist due to an almost pH neutral solution which makes photoresist a good masking material for the oxide etch.

SIO etch (BHF with wetting agent) can also be used for etching silicon oxide. This is mainly for etching small holes. If you have wetting problems in BHF try the SIO etch. It is also a good idea to wet the sample in water before etching.

Silicon oxide etch data

	BHF	5% HF	SIO
General description	Etching of silicon oxide with a stabil etch rate	Mainly for removing native oxide	Etching of silicon oxide - especially for etching small holes
Chemical solution	BHF	5% HF	BHF with wetting agent
Process temperature	Room temperature	Room temperature	Room temperature
Possible masking materials	Photoresist Silicon nitride PolySi Blue film	Photoresist (in beaker or PP-bath in fume hood RR2) Silicon nitride (in beaker) PolySi (in beaker) Blue film (in beaker)	Photoresist Silicon nitride PolySi Blue film
Etch rate	Wet thermal oxide:~80nm/min PECVD1 (standard):~147nm/min TEOS:~265nm/min	Wet thermal oxide:~25nm/min PECVD1 (standard):~87nm/min TEOS:~153nm/min	Wet thermal oxide:~80nm/min PECVD1 (standard):~147nm/min TEOS:~265nm/min
Selectivity R_Si₃N₄ / R_SiO₂	~21	<21
Batch size	1-25 wafers at a time	1-25 wafer at a time
Size of substrate	2-6" wafers	2-6" wafers
Allowed materials	Silicon Silicon nitrides Silicon oxides	Silicon Silicon nitrides Silicon oxides