Specific Process Knowledge/Etch/Etching of Silicon

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Comparing silicon etch methods

There are a broad variety of silicon 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 etches:

• Si Etch: KOH
• Wet PolySilicon etch

Dry etches:

• Si etch using ASE (Advanced Silicon Etch)
• Si etch using DRIE-Pegasus (Silicon Etch)
• Si etch using IBE/IBSD Ionfab 300

Compare the methods for Si etching

	Si Etch	Wet PolySilicon etch	DRIE-Pegasus (Deep Reactive Ion Etch)	ASE (Advanced Silicon Etch)	ICP Metal Etch	IBE/IBSD Ionfab 300
Generel description	Anisotropic etch in crystalline silicon High selectivity to the {111}-planes	Isotropic etch in crystalline silicon and polysilicon	State-of-the-art dry silicon etcher with atmospheric cassette loader Good selectivity to photoresist Extremely high etch rate and advanced processing options	Can etch isotropic and anisotropic depending on the process parameters and mask design Good selectivity to photoresist The ASE open for same metal on the samples and SiO2 etching, which can affect the Si etch stability.	This is dedicated to metal etch. So fare only Si etch of nanostructures has been explored on the system.	Primarily for pure physical etch by sputtering with Ar-ions
Possible masking materials	Silicon Nitride Silicon Oxide	Photo-, DUV- and e-beamresist E-beam resist Silicon Oxide Silicon Nitride Aluminium Chromium (ONLY RIE2!) Other metals if they cover less than 5% of the wafer area (ONLY RIE2!)	Photo-, DUV- and e-beamresist Silicon Oxide Silicon Nitride Aluminium oxide	Photo-, DUV- and e-beamresist Silicon Oxide Silicon Nitride Aluminium	Photo-, DUV- and e-beamresist Silicon Oxide Silicon Nitride Aluminium Cr Ti	Any material that is accepted in the machine
Etch rate range	Si(100) @80oC: 1.29+0.05 µm/min Si(100) @70oC: ~0.7 µm/min Si(100) @60oC: ~0.4 µm/min	~100-200 nm/min, highly dependent on doping level	Up to 18-20 µm/min depending on recipe, mask design and aspect ratio.	<130nm/min to >5.6 µm/min depending on recipe, mask design and aspect ratio.	Process dependent. The nano etch is in the range 59-311 nm/min	Process dependent. Has been tested in the range 17-31 nm/min
Substrate size	#25 wafers of 100mm or 150nm in Si Etch 1 & 2 #25 wafers of 100mm or 150nm and smaller samples in Si Etch 3 (fume hood)	##25 wafers of 100mm or 150nm mm wafers	As many small samples as can be fitted on the 100mm carrier. #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 when the system is set up to 150mm)	As many small samples as can be fitted on a 150mm wafer #5 50 mm wafers fitted on a 150mm wafer #1 100 mm wafer on a 150mm wafer #1 150 mm wafers (The system is normally 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
Allowed materials	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Other materials (only in "Si Etch 3 (fume hood))	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photo-, DUV- and e-beamresist Aluminium oxide Quartz/fused silica	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photo-, DUV- and e-beamresist Aluminium Quartz/fused silica Other metals if they cover less than 5% of the wafer area	Silicon Photo-, DUV- and e-beamresist PolySilicon Silicon oxide Silicon (oxy)nitride Aluminium Titanium Chromium 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