Specific Process Knowledge/Etch/Etching of Silicon Nitride

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Comparing silicon nitride etch methods at DTU Nanolab

There are a broad variety of silicon nitride etch methods at DTU Nanolab. The methods are compared here to make it easier for you to compare and choose the one that suits your needs.

• Wet Silicon Nitride Etch
• Etch of Silicon Nitride using AOE
• IBE/Ion Beam Etching using IBSD Ionfab 300
• Silicon nitride etch using the ICP metal

Compare the methods for Silicon Nitride etching

	Wet Silicon Nitride Etch	BHF	ASE	AOE (Advanced Oxide Etch)	IBE/IBSD Ionfab 300	ICP Metal
Generel description	Isotropic etch Well suited for removing all nitride on a wafer surface (nitride strip) without a mask. High selectivity Si3N4/Si (>100) and Si3N4/SiO2 (>20) @ 160 C.	Isotropic etch Well suited for removing all PECVD nitride on a wafer surface (nitride strip) without a mask. Etches LPCVD nitride very slowly	Anisotropic etch: vertical sidewalls	Anisotropic etch: vertical sidewalls Deep etch	Primarily for pure physical etch by sputtering with Ar-ions	Anisotropic etch: vertical sidewalls
Possible masking materials	Silicon Oxide PolySilicon	Photoresist PolySilicon Blue film	Photoresist DUV resist E-beam resist Silicon Oxide Silicon Nitride Aluminium Metals if they cover less than 5% of the wafer area	Photoresist DUV resist E-beam resist Silicon Oxide Silicon Nitride Aluminium Chromium (please try to avoid it)	Any material that is accepted in the machine	Resists other materials from the allowed list of materials
Etch rate range	Si3N4 @ 160 oC: ~26 Å/min	PECVD nitride: ~400-1000 Å/min Stoichiometric LPCVD nitride: ~0.65-8 nm/min (Yannick Seis, KU, 2019)	Probably betweeb 20-300 nm/min depending on the process parameters	Process dependent. Tested once to ~60nm/min	Process dependent. Has not been tested yet.	Process dependent 60-65 nm/min has been tested
Substrate size	#1-25 4" and 6" wafers	#1-25 4"-6" wafers	As many small samples as can be fitted on the 100mm carrier (bad/no cooling!) #1 100mm wafer (or smaller with carrier) #1 150mm wafer (only when the system is set up for 150mm)	As many small samples as can be fitted on a 100mm wafer #1 50 mm wafer fitted on a 100mm wafer #1 100 mm wafer #1 150 mm wafers (only RIE2 when set up to 150mm)	As many samples as can be securely fitted on a up to 200mm wafer #1 50 mm wafer with special carrier #1 100 mm wafer with special carrier #1 150 mm wafers with special carrier #1 200 mm wafer	Set up for 150mm wafers Smaller samples can be processes when fixed to a 150mm carrier wafer.
Allowed materials	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist Blue film	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resists DUV resists Other metals if they cover less than 5% of the wafer area Quartz/fused silica	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resists DUV resists Aluminium Chromium (try to avoid it) Quartz/fused silica	Silicon Silicon oxides Silicon (oxy)nitrides Metals from the +list Metals from the -list Alloys from the above list Stainless steel Glass III-V materials Resists Polymers Capton tape	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resists DUV resists Aluminium (Al, Al2O3, AlN) Chromium Titanium (Ti, TiW, TiN, TiO2) Tungsten (W) Molybdynem Quartz/fused silica