Specific Process Knowledge/Etch/Etching of Silicon Oxide

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Comparing silicon oxide etch methods at DTU Nanolab

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

• Wet Silicon Oxide Etch

• SiO2 etch using III-V RIE
• SiO2 etch using AOE
• SiO2 etch with DRIE Pegasus 4
• SiO2 etch using ASE
• SiO2 etch using ICP metal
• IBE/IBSD Ionfab 300
• SiO2 etch using Plasma Asher (isotropic)

Compare the methods for Silicon Oxide etching

	Wet Silicon Oxide etch (BHF/HF)	ASE	III-V RIE	AOE (Advanced Oxide Etch)	DRIE Pegasus 4	ICP metal	IBE/IBSD Ionfab 300	HF Vapour Phase Etch
Generel description	Isotropic etch	Anisotropic etch: vertical sidewalls	Anisotropic etch: vertical sidewalls Premarily for III-V samples	Anisotropic etch: vertical sidewalls	Anisotropic etch: almost vertical sidewalls	Anisotropic etch: almost vertical sidewalls We prefer that SiO2 etch on 6" wafers takes place in the Pegasus 4.	Primarily for pure physical etch by sputtering with Ar-ions	Gas phase HF etching with ethanol as carrier
Possible masking materials	Photoresist PolySilicon Silicon nitride (LPCVD) Blue film Cr/Au for deeper etches (plastic beaker)	Photoresist DUV resist E-beam resist Silicon Silicon Nitride Metals if they cover less than 5% of the wafer area	Photoresist DUV resist E-beam resist Aluminum Silicon Silicon Nitride	Photoresist DUV resist E-beam resist Silicon Silicon Nitride Aluminium Chromium (Please try to avoid this)	Photoresist DUV resist E-beam resist Si Silicon Nitride Chromium (ask for permission)	Photoresist DUV resist E-beam resist Si Silicon Nitride Aluminium Chromium Ti	Any material that is accepted in the machine	Aluminium Aluminium oxide Polysilicon
Etch rate range	~75 nm/min (Thermal oxide) in BHF ~80 nm/min (Thermal oxide) in BOE 7:1 Etchant VLSI with Surfactant ~25 nm/min (Thermal oxide) in 5%HF ~3-4µm/min in 40%HF	Process dependent Tested range: ~20nm/min - ~250nm/min	Process dependent Tested range: ~1nm/min - ~30nm/min	Process dependent Tested range: ~60nm/min - ~550nm/min	Process dependent <500nm/min	Process dependent Tested range: ~40nm/min - ~200nm/min	Process dependent Tested once ~22nm/min	Sample and load dependent Expected range: 12 - 175 nm/min
Substrate size	#1-25 100mm wafers in our 100mm bath What can be fitted in a plastic beaker	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 set up for 150mm)	Up to 20cm in diameter	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 when the system is set up to 150mm)	As many small samples as can be bonded on a 150mm wafer #1 50 mm wafer bonded on a 150mm wafer #1 100 mm wafer bonded on a 150nm wafer #1 150 mm wafers	As many small samples as can be fitted on a 150mm wafer #1 50 mm wafer fittesd on a 150mm wafer #1 100 mm wafer fitted on a 150nm wafer #1 150 mm wafers	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	Pieces #1 50 mm wafer #1 100 mm wafer #1 150 mm wafer
Allowed materials	In the dedicated bath: Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist Blue film In a plastic beaker: No limits cross contamination wise	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist DUV resist E-beam resist Other metals if they cover less than 5% of the wafer area Quartz/fused silica	Please take a look in the cross contamination sheet in LabManager for details GaAs, GaN, InP, with epitaxial layers Aluminum Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist DUV resist E-beam resist	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist DUV resist E-beam resist Aluminium Chromium (try to avoid it) Quartz/fused silica	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist DUV resist E-beam resist Chromium Quartz/fused silica	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist DUV resist E-beam resist Aluminium Chromium Titanium W Quartz/fused silica	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon oxides Silicon (oxy)nitrides Metals Alloys Stainless steel Glass III-V materials Resists Polymers Capton tape	Please take a look in the cross contamination sheet in LabManager for details Silicon Silicon oxides Aluminium

Dry etch with Hard mask

By Martin Lind Ommen - fall 2016
Testing selectivities for SiO₂ etching with hard masks on AOE and ICP metal with different recipes.All tests are done with 100% etching load

MLO_psi is the version of SiO2_psi on labadviser that is shown under low line with reduction.
The recipe ICP is on ICP metal call: A SiO2 etch with C4F8 with resist mask
I had problems with this recipe - it gave polymer on the surface, therefor I do not have more info on that.