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:

• Dry etch using RIE1 or RIE2
• ASE (Advanced Silicon Etch)
• DRIE-Pegasus (Silicon Etch)
• 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 methodes 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.

• Process description using methode 1

• Process description using methode 2

Comparison methode 1 and methode 2 for the process

	KOH Etch	Wet PolySilicon etch	Dry etch using RIE1 or RIE2	DRIE-Pegasus (Silicon Etch)	ASE (Advanced Silicon Etch)	ICP Metal Etch	IBE/IBSD Ionfab 300
Generel description	Anisotropic etch in the (100)-plan High selectivity to the other plans Anisotropic etch: vertical sidewalls independent of the crystal plans	Isotropic etch in Silicon and Polysilicon	Can etch isotropic and anisotropic depending on the process parameters	State-of-the-art dry silicon etcher with atmospheric cassette loader 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		Primarily for pure physical etch by sputtering with Ar-ions
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 and zep resist Silicon Oxide Silicon Nitride Aluminium oxide	Photoresist 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
Resist type	UV sensitive: AZ SU8	DUV sensitive fff	E-beam sensitive ZEP502A (positive) HSQ (negative) SU8	Imprint polymers: ??	?? sensitive: ??
Resist thickness range	~0.5µm to 20µm?	~50nm to 2µm?	~30nm to 0.5 µm	~20nm to 10µm?	?nm - ?µm
Typical exposure time	2s-30s pr. wafer	?-? pr. ?	?-? pr. µm2	? pr. wafer	? pr. µm2
Substrate size	# small samples # 50 mm wafers # 100 mm wafers # 150 mm wafers	# small samples # 50 mm wafers # 100 mm wafers # 150 mm wafers	We have cassettes that fit to # 4 small samples (20mm, 12mm, 8mm, 4mm) # 6 wafers of 50 mm in size # 2 wafers of 100 mm in size # 1 wafer of 150 mm in size	# small samples # 50 mm wafers # 100 mm wafers # 150 mm wafers	# small samples # 50 mm wafers # 100 mm wafers # 150 mm wafers
Allowed materials	Allowed material 1 Allowed material 2	Allowed material 1 Allowed material 2 Allowed material 3	Si, SiO2, III-V materials	Allowed material 1 Allowed material 2 Allowed material 3	Allowed material 1 Allowed material 2 Allowed material 3