Specific Process Knowledge/Etch/Etching of Silicon Oxide/SiO2 etch using ASE/Unstable recipes - SiO2 etch

SiO2 etch with resist mask on wafer with clamping and He backside cooling

Unless otherwise stated, all content in this section was done by Berit Herstrøm, DTU Nanolab, May 2018

The ASE is now the "dirty" plasma etcher at Nanolab meaning small amount of metals are allowed to be exposed by the plasma. That calls for recipes etching Silicon oxide and silicon nitride as well as silicon in this machine.

Not a lot experiments have been done yet etching SiO2 on wafers that are clamped and cooled but here is the best result so fare.

*This recipe is no longer stable.

Parameter	SiO2 before etch	Resist before etch	Coil power	Platen power	Pressure	Flow rate C4F8	Flow rate H2	Flow rate He	T	Process time	Comment	Results	CD change	Profile angles	Etch rate in SiO2	Etch rate in resist	Selectivity (SiO2:resist)	Etch rate in Si and SiN
1SIOICP1	1892nm	1.4µm	800W	15 W	2.5mTorr	13sccm	26 sccm		20	15:00 min	Residues on the surface is coming when the resist is removed by plasma ashing, so remove the resist with 1165 remove and ultra sound to avoid this.			.	63 nm/min	27 nm/min	2.3	bghe@Nanolab 2019-01-17 Si:16-17 nm/min in the middle of the wafer (80% load) Si:14-15 nm/min at the edge of the wafer (80% load) Emil Christian Stillhoff Jensen @Nanolab 2021-07-31 SiN(700 nm PECVD nitrid): >46nm/min

Recommended recipe for SiO2 etch using a carrier

Parameter	Recipe name: 1SiO2_02	Recipe name: 1SiO2_03	Testing other settings to increase etch rate in nitride
Coil Power [W]	150	100	150
Platen Power [W]	25	25	25
Platen temperature [oC]	20	20	20
C4F8 flow [sccm]	36	10	20
H2 flow [sccm]	13	10	0
He flow [sccm]	0	100	100
Pressure [mTorr]	2.5	2.5	2.5

Results when etching a piece of wafer on a Si carrier

Material to be etched	Recipe: 1SiO2_02 *This recipe is no longer stable.	Recipe: 1SiO2_03	Testing other settings to increase etch rate in nitride
Etch rate in SiO2	22.1 nm/min	26.8 nm/min	?
Etch rate in PECVD nitride	.	20.8nm/min (kabi@nanolab 20190301) - ~0nm/min (ecsj@nanolab 20210729)	?
Etch rate in LPCVD nitride	.	only around 6 nm/min (20190820)	23.7 nm/min in the middle, 17 nm/min close to the edge
Etch rate in resist (MIR)	12.5 nm/min	13.9 nm/min	Not tested properly (still more than 1 µm left (1.5µm MIR) after 12 min
Selectivity (SiO2:resist)	1.8	1.9	?
Etch rate in silicon		4 nm/min in the middle of the wafer (80% load) bghe@Nanolab 20190117 2-3 nm/min at the edge of the wafer (80% load) bghe@Nanolab 20190117
Profile Images			Profile not analyzed

Results when etching a whole wafer on an Al carrier

Material to be etched	Recipe: 1SiO2_02
Etch rate in SiO2	22.1 nm/min
Etch rate in resist (MIR)	16.6 nm/min
Selectivity (SiO2:resist)	1.3
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