Specific Process Knowledge/Etch/Etching of Silicon

Etch of silicon can be done by either wet etch or dry etch. The standard setups for this here at DANCHIP are:

Wet etches:

• KOH Etch
• Wet PolySilicon etch

Dry etches:

• Si etch using RIE1 or RIE2
• Si etch using ASE (Advanced Silicon Etch)
• Si etch using DRIE-Pegasus (Silicon Etch)
• Si etch using IBE/IBSD Ionfab 300

Comparison of KOH etch, wet PolySilicon etch, RIE etch, ASE etch and DRIE-Pegasus for etching of Silicon

	KOH	PolySilicon etch	RIE	ASE	DRIE-Pegasus
General description	Anisotropic etch in the (100)-plan High selectivity to the other plans	Isotropic etch in Silicon and Polysilicon	Can etch isotropic and anisotropic depending on the process parameters Anisotropic etch: vertical sidewalls independent of the crystal plans	As RIE but better for high aspect ratio etching and deep etches (higher etch rate) Good selectivity to photoresist	State-of-the-art dry silicon etcher with atmospheric cassette loader Extremely high etch rate and advanced processing options
Possible masking materials	Silicon Nitride Silicon Oxide	Photoresist	Photoresist 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!)	Photoresist Silicon Oxide Silicon Nitride Aluminium	Photoresist and zep resist Silicon Oxide Silicon Nitride Aluminium oxide
Etch rate	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	<40nm/min to >600nm/min depending on recipe parameters and mask design	<130nm/min to >5.6 µm/min depending on recipe, mask design and aspect ratio.	Up to 18-20 µm/min depending on recipe, mask design and aspect ratio.
Size of substrate	4" in our standard bath 4", 2" in "Fumehood KOH"	4" in our standard bath	4" (or smaller with carrier)	6" (when it is set up for 6") and 4" (or smaller if you have a carrier)	6" (when it is set up for 6") and 4" (or smaller if you have a carrier)
Batch size	25 wafers at a time 1-5 wafers in "Fumehood KOH"	25 wafers at a time	One wafer at a time	One wafer at a time	One wafer at a time but you can load a whole batch of 25 wafers and set up an individual for each one
Allowed materials	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Other materials (only in "Fumehood KOH")	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resist Aluminium Chromium (ONLY RIE2!) Other metals if they cover less than 5% of the wafer area (ONLY RIE2!)	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resist Aluminium	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist zep resist Aluminium oxide

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Comparing silicon etch methods at Danchip

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

Wet etches:

• KOH Etch
• Wet PolySilicon etch

Dry etches:

• Si etch using RIE1 or RIE2
• 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

	KOH Etch	Wet PolySilicon etch	RIE (Reactive Ion 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	Can etch isotropic and anisotropic depending on the process parameters and mask design.	State-of-the-art dry silicon etcher with atmospheric cassette loader Good selectivity to photoresist Extremely high etch rate and advanced processing options	As RIE but better for high aspect ratio etching and deep etches (higher etch rate) Good selectivity to photoresist The ASE is dedicated to polymer etch, 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	Silicon Nitride Silicon Oxide Photoresist	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	<40nm/min to >600nm/min depending on recipe parameters and mask design	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 in KOH2 #1-5 wafers of 100mm or 50mm in "Fumehood KOH" #25 wafers of 100mm or 150mm in KOH3	#25 100 mm wafers in our 100mm bath	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 100mm wafer #1 50 mm wafer fitted on a 100mm wafer #1 100 mm wafer #1 150 mm wafers (only RIE2 when set up for 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 "Fumehood KOH")	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist	Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photo-, DUV- and e-beamresist Other metals if they cover less than 5% of the wafer area (ONLY RIE2!) Quartz/fused silica	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	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