Specific Process Knowledge/Etch/Etching of Silicon Oxide/SiO2 etch using Plasma Asher

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SiO2 can be etched in the Plasma Asher using CF4

Test work done January 2014 by Lis Nielsen and Berit Herstrøm @Nanolab

SiO2 can be etched in the Plasma Asher using CF4 and aluminum as a masking material. This gives an isotropic etch. In test2 the SiO2 layer has been etched through and there is a small over etch in the Silicon substrate. The masking material is 100 nm Al. Etch rate and uniformity measurements have been done on wafers with no mask.

• Images of isotropic SiO2 etch in the Plasma asher: Test 2
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Plasma Asher parameter settings and results for the tests
	Test1	Test2
O2 flow	0 sccm	0 sccm
N2 flow	0 sccm	0 sccm
CF4 flow	200 sccm	200 sccm
Power	1000 W	1000 W
Process Time	10 min	50 min
Average Etch rate on wafer (5 points measured)	22.6 nm/min	31.8 nm/min
Non-uniformity over the wafer (5 points measured)	±10.8 %	±11.0 %
Non-uniformity plot