Specific Process Knowledge/Etch/Etching of Silicon Oxide/SiO2 etch using AOE/Standard recipe with resist mask

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The standard recipe

The standard recipe for oxide etching with photo resist as masking material is called: SiO2_res. The parameters and results so fare are as follows:

Parameter	Recipe name: SiO2_res (SiO2 etch with resist mask)	Variations over SiO2_res made in 2010 by BGHE
Coil Power [W]	1300	1000-1600
Platen Power [W]	200	150-300
Platen temperature [oC]	0	0
He flow [sccm]	174	174, 300
C4F8 flow [sccm]	5	5
H2 flow [sccm]	4	0, 4
Pressure [mTorr]	4	2.3, 4

Etch rates in different materials using the standard "Silicon oxide etch with resist mask"

Material to be etched	Etch rate using SiO2_res
Thermal oxide	~230nm/min (5% etch load) - etch load dependency see here
TEOS oxide (5% load)	233nm/min ±0.7% - "±" represents the non-uniformity over a 100mm wafer - etched in Marts 2013 by LN/BGE@danchip
PECVD1 (standard) oxide (5% load)	242nm/min ±0.6% - "±" represents the non-uniformity over a 100mm wafer - etched in Marts 2013 by LN/BGE@danchip
Al2O3 from the ALD	50nm can be etched in 10min - etched in November 2014 by FRSTO@danchip
Silicon rich nitride from furnace B2	136nm was etched in 1min (whole wafer) - etched in October 2015 by bghe@danchip

Using different resist masks: results using the standard recipe for "Silicon oxide etch with resist mask"

.	Az	MIR	nLof	KRF	CSAR
Selectivity to thermal oxide [:1]	2-3 - etch load dependency see here 1.9 - tested November 2015 by BGHE	1.8 - tested November 2015 by BGHE	2.0 - tested November 2015 by BGHE	~2 - tested May 2013 by Christian Østergaard @nanotech.	.
Profile [o]	~90	.	.	.	.
Roughness of the resist after etch - striation on sidewalls	see here	see here	see here	.	.
Images	See here	.	.	See images here	.
Comments	A negative resist process was done to make the mask. I have not had so good results with a positive resist process.	.	.	.	Using the standard oxide recipe (SiO2_res) for 1 min the CSAR looked burned and could not be removed by CSAR stripper (AR600-71). For a better recipe look here

Variations over the standard "SiO2 etch with resist mask" recipe

Typical results	Variations over SiO2_res made in 2010 by BGHE See results here
Etch rate of thermal oxide	~160-340nm/min
Selectivity to AZ resist [:1]	2.7-4.3
Profile angle	83-90
Images	See here
Comments	.

Etching of micro structures in Aluminum oxide

by Fredrik Stöhr

Aluminum oxide (Al₂O₃, Alumina) can be etched with the standard recipe for silicon oxide etching. The parameters including the chuck temperature are identical to the recipe described above: SiO2_res. The etch is probably very physical and gives redeposition, so please consider using a Cl2 etch on the ICP metal instead (BGHE 2015-04-17)

General Description

Process date: Summer 2014

Aluminum Oxide with a thickness of 50 nm has been deposited by atomic layer deposition using the respective standard recipe.

Substrates: Blank 525 µm Silicon wafers or Silicon wafers with thermally grown Silicon Oxide prior to Alumina deposition.

Mask: [XOP8] AZ5214E 1.5 µm thick (HMDS pretreatment, 6-inch aligner 3 sec exposure, 60 sec development).

Etch Load (Total Exposed SiO2): ~ 5 %

Post process: O2 Plasma Ashing 10 min

Etch time: 3 min. Substrate: Blank Si. Bird View. The dark area is Silicon. The bright area is Alumina. The black flakes stem from redeposited sputtered material and is most likely aluminum oxide, since it is almost non-volatile in the used plasma chemistry. It must have been laying on top of the photo resist mask and landed on the alumina after resist ashing.	Etch time: 3 min. Substrate: Blank Si. Bird View. Close-up. The dark area is Silicon. The bright area is Alumina. The black flakes stem from redeposited sputtered material.	Etch time: 3 min. Substrate: Blank Si. Bird View. Close-up. The dark area is Silicon. The bright area is Alumina.	Etch time: 3 min Cross section of deep reactive ion etched silicon (DRIE Pegasus), where the structured alumina was used as a mask. Remarkably, the etch selectivity of Alumina to Silicon is >1:10000.

Etch time: 10 min. Substrate: Blank Si. The view tilt angle is 30°. The edge is corrugated, which is most likely to the corrugated resist mask.	Etch time: 10 min. Substrate: Blank Si. The view tilt angle is 30°. Vertical striations and considerable over-etching of the Silicon substrate are apparent. It seems as if less material has been redeposited, which may be due to the prolonged etch time in comparison to the above.	Etch time: 10 min. Substrate: Blank Si. The view tilt angle is 30°. Vertical striations and considerable over-etching of the Silicon substrate are apparent. It seems as if less material has been redeposited, which may be due to the prolonged etch time in comparison to the above.

Etch time: 15 min. Substrate: Silicon with 1 µm thermally grown SiO2 The view tilt angle is 45°. Alumina and Silicon Oxide may be etched in one go.	Etch time: 15 min. Substrate: Silicon with 1 µm thermally grown SiO2 The view tilt angle is 45°. Alumina and Silicon Oxide may be etched in one go. Considerable over-etchign of the Silicon substrate is apparent.	Etch time: 15 min. Substrate: Silicon with 1 µm thermally grown SiO2 The view tilt angle is 45°. Alumina and Silicon Oxide may be etched in one go. Considerable over-etchign of the Silicon substrate is apparent.