Specific Process Knowledge/Etch/KOH Etch - Revision history

Kabi: /* KOH etching baths */

2026-02-12T10:48:09Z

KOH etching baths

← Older revision		Revision as of 12:48, 12 February 2026
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	*TEOS oxide from furnace: 300nm etched in 11 min		*TEOS oxide from furnace: 300nm etched in 11 min
	jemafh@nilt 2019-Marts:		jemafh@nilt 2019-Marts:
	*Standard from PECVD3: selectivity 1:100 to Si		*Standard from PECVD3: selectivity 1:100 to Si(100)
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	.		.

Kabi: /* KOH etching baths */

2026-02-12T10:47:11Z

KOH etching baths

← Older revision		Revision as of 12:47, 12 February 2026
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	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]		\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]
			\|style="background:WhiteSmoke; color:black"\|
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Etch rates in LPCVD Si3N4 and SiN		\|style="background:LightGrey; color:black"\|Etch rates in LPCVD Si3N4 and SiN

Kabi: /* KOH etching baths */

2026-02-12T10:46:15Z

KOH etching baths

← Older revision		Revision as of 12:46, 12 February 2026
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	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]		\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]
			\|-
			\|style="background:LightGrey; color:black"\|Etch rates in LPCVD Si3N4 and SiN
			\|style="background:WhiteSmoke; color:black"\|
			*Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
			\|style="background:WhiteSmoke; color:black"\|
			*Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	\|-		*Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
	~~!Etch rates in LPCVD Si3N4 and SiN~~
	~~\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000~~
	~~\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000~~
	\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Roughness		\|style="background:LightGrey; color:black"\|Roughness

Kabi: /* KOH etching baths */

2026-02-12T10:37:26Z

KOH etching baths

← Older revision		Revision as of 12:37, 12 February 2026
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	Key facts for the different etch baths available at DTU Nanolab are resumed in the table:		Key facts for the different etch baths available at DTU Nanolab are resumed in the table:
	<br clear="all" />		<br clear="all" />


	{\| border="2" cellspacing="0" cellpadding="2"		{\| border="2" cellspacing="0" cellpadding="2"

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	*:[http://kemibrug.dk/KBA/CAS/106882/?show_KBA=1&portaldesign=1 see SDS here]		*:[http://kemibrug.dk/KBA/CAS/106882/?show_KBA=1&portaldesign=1 see SDS here]
	\|-		\|-
	!style="background:silver; color:black" align="center" valign="center~~" rowspan="7~~"\|Performance		! rowspan="8" style="background:silver; color:black" align="center" valign="center" \|Performance
	\|style="background:LightGrey; color:black"\|Etch rates in crystalline silicon (100)		\|style="background:LightGrey; color:black"\|Etch rates in crystalline silicon (100)
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
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	\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]		\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
			\|-
			!Etch rates in LPCVD Si3N4 and SiN
			\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
			\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
			\|Etch rates in LPCVD nitrides is very low. Etch selectivities to Si(100) is higher than 1:10.000
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Roughness		\|style="background:LightGrey; color:black"\|Roughness

Hvje: Deleted the mixing option with pellets

2025-09-24T11:51:38Z

Deleted the mixing option with pellets

← Older revision		Revision as of 13:51, 24 September 2025
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	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*Mixing ratios giving 28 wt% KOH solutions		*Mixing ratios giving 28 wt% KOH solutions
	~~KOH:H<sub>2</sub>O - 500 g : 1000 ml, when using pills~~
	KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution		KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*Mixing ratios giving 28 wt% KOH solutions		*Mixing ratios giving 28 wt% KOH solutions
	~~KOH:H<sub>2</sub>O - 500 g : 1000 ml, when using pills~~
	KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution		KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution
	\|-		\|-

Hvje: cleaning recommandation

2025-07-28T09:55:31Z

cleaning recommandation

← Older revision		Revision as of 11:55, 28 July 2025
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	[[Category: Equipment\|Etch Wet KOH etch]]		[[index.php?title=Category:Equipment\|Etch Wet KOH etch]]
	[[Category: Etch (Wet) bath\|KOH etch]]		[[index.php?title=Category:Etch (Wet) bath\|KOH etch]]

	==Si etch - ''Anisotropic silicon etch''==		==Si etch - ''Anisotropic silicon etch''==
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	KOH belongs to the family of anisotropic Si-etchants based on aqueous alkaline solutions. The anisotropy stems from the different etch rates in different crystal directions. The {111}-planes are almost inert whereas the etch rates of e.g. {100}- and {110}-planes are several orders of magnitude faster.		KOH belongs to the family of anisotropic Si-etchants based on aqueous alkaline solutions. The anisotropy stems from the different etch rates in different crystal directions. The {111}-planes are almost inert whereas the etch rates of e.g. {100}- and {110}-planes are several orders of magnitude faster.

	KOH-etching is a highly versatile and cheap way to realize micro mechanical structures if you can live with the necessary Si<sub>3</sub>N<sub>4</sub>- or SiO<sub>2</sub>-masking materials and the potassium contamination of the surface. '''The latter necessitates in most cases a wet post-clean ([[Specific Process Knowledge/Wafer cleaning/7-up & Piranha\|'7-up']] or [[Specific Process Knowledge/Wafer cleaning/RCA\|RCA-clean]]) if the wafer is to be processed further.'''		KOH-etching is a highly versatile and cheap way to realize micro mechanical structures if you can live with the necessary Si<sub>3</sub>N<sub>4</sub>- or SiO<sub>2</sub>-masking materials and the potassium contamination of the surface. '''The latter necessitates in most cases a wet post-clean ([[Specific Process Knowledge/Wafer cleaning/7-up & Piranha\|'7-up']] or [[Specific Process Knowledge/Wafer cleaning/RCA\|RCA-clean]]) if the wafer is to be processed further. we also recommend to rinse the wafers in a 5% HCL solution to remove metal ions from the KOH solution.'''

	At DTU Nanolab we use as a standard a 28 wt% KOH. The etch rate - and the selectivity towards a SiO<sub>2</sub>-mask - is depending on the temperature. We normally use T=80 <sup>o</sup>C but may choose to reduce this to e.g. 60 <sup>o</sup>C or 70 <sup>o</sup>C in case of a high-precision timed etch (e.g. defining a thin membrane). In some cases we recommend to saturate the standard 28 wt% KOH with IPA with an etch temperature at T=70 <sup>o</sup>C (reduce evaporation of IPA). One example is for boron etch-stop, where the selectivity towards the boron-doped silicon is improved compared to the standard etch. Etching with IPA added to the KOH solution (250ml IPA/1000ml KOH) can be done in KOH fumehood.		At DTU Nanolab we use as a standard a 28 wt% KOH. The etch rate - and the selectivity towards a SiO<sub>2</sub>-mask - is depending on the temperature. We normally use T=80 <sup>o</sup>C but may choose to reduce this to e.g. 60 <sup>o</sup>C or 70 <sup>o</sup>C in case of a high-precision timed etch (e.g. defining a thin membrane). In some cases we recommend to saturate the standard 28 wt% KOH with IPA with an etch temperature at T=70 <sup>o</sup>C (reduce evaporation of IPA). One example is for boron etch-stop, where the selectivity towards the boron-doped silicon is improved compared to the standard etch. Etching with IPA added to the KOH solution (250ml IPA/1000ml KOH) can be done in KOH fumehood.

Hvje: /* KOH etching baths */

2024-04-11T11:13:20Z

KOH etching baths

← Older revision		Revision as of 13:13, 11 April 2024
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	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*Etch of Silicon in 28 wt% KOH		*Etch of Silicon in 28 wt% KOH
	The bath is dedicated ~~wafer~~ with ~~electroplated Nickel~~ or otherwise dirty wafers		The bath is dedicated wafers with metal or otherwise dirty wafers
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Link to safety APV and SDS		\|style="background:LightGrey; color:black"\|Link to safety APV and SDS

Hvje: /* KOH etching baths */

2023-12-14T09:11:18Z

KOH etching baths

← Older revision		Revision as of 11:11, 14 December 2023
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	*Theoretical values:		*Theoretical values:
	*1.2 nm/min (60 °C)		*1.2 nm/min (60 °C)
	*6 nm/min (80 °C)		*7.5 nm/min (80 °C)
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*Theoretical values:		*Theoretical values:
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	*Theoretical values:		*Theoretical values:
	*1.2 nm/min (60 °C)		*1.2 nm/min (60 °C)
	*6 nm/min (80 °C)		*7.5 nm/min (80 °C)
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Etch rates in other oxides		\|style="background:LightGrey; color:black"\|Etch rates in other oxides

Hvje: /* KOH etching baths */

2023-12-14T09:10:37Z

KOH etching baths

← Older revision		Revision as of 11:10, 14 December 2023
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	*Theoretical values:		*Theoretical values:
	*1.2 nm/min (60 °C)		*1.2 nm/min (60 °C)
	*6 nm/min (80 °C)		*7.5 nm/min (80 °C)
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*Theoretical values:		*Theoretical values:

Hvje: /* KOH etching baths */

2023-09-20T08:59:27Z

KOH etching baths

← Older revision		Revision as of 10:59, 20 September 2023
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	KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution		KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution
	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	*~~Custom made~~		*Mixing ratios giving 28 wt% KOH solutions
			KOH:H<sub>2</sub>O - 500 g : 1000 ml, when using pills
			KOH:H<sub>2</sub>O - 1000 ml: 1200 ml, when using premixed 50% KOH solution
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Temperature		\|style="background:LightGrey; color:black"\|Temperature

← Older revision		Revision as of 12:47, 12 February 2026
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	\|style="background:WhiteSmoke; color:black"\|		\|style="background:WhiteSmoke; color:black"\|
	\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]		\|style="background:WhiteSmoke; color:black"\|See etchrates for PECVD SiN [https://labadviser.nanolab.dtu.dk/index.php?title=Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Silicon_Nitride/Deposition_of_Silicon_Nitride_using_PECVD/PECVD3:_Low_stress_nitride_testing#DOE_made_to_find_a_good_QC_nitride_recipe_with_low_stress_and_low_KOH_etch_rate_(by_Berit_Herstrøm_@_DTU_Nanolab_2016_Marts) here]
			\|style="background:WhiteSmoke; color:black"\|
	\|-		\|-
	\|style="background:LightGrey; color:black"\|Etch rates in LPCVD Si3N4 and SiN		\|style="background:LightGrey; color:black"\|Etch rates in LPCVD Si3N4 and SiN