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 G. Herstrøm @Danchip

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

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

• Images of isotropic SiO2 etch in the Plasma asher: Test 2
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