LPCVD SiN and SiC covered with ALD alumina (Kavli)
October 2015
Overview of Samples
Tested batch contains 9 samples: 1, 2,3 …, 9.
LPCVD SiN or SiC is grown on 525 μm thick Si substrate and then covered with a thin layer of ALD
alumina at Kavli Nanolab. LPCVD layer is present on the backside of samples, while alumina is
covering only topside.
Sample
Substrate layer*
1
2
3
4
5
6
7
8
9
std SiN
Si++N
std SiN
Si++N
std SiN
Si++N
std SiN
Si++N
SiC
Thickness of substrate
[nm]
200
200
40
40
200
200
40
40
150
Thickness of ALD alumina
[nm]
12.6
12.6
12.6
12.6
25**
25**
25**
25**
12.6
*’’Substrate’’ in this case is a landing material for ALD.
**Thickness wasn’t verified by ellipsometry yet, but it’s expected to be around 2x12.6 nm.
ALD
Substrate layer (SiN or SiC)
Silicon bulk (525 μm)
Deposition method of SiN.
Deposition method of SiC.
Deposition method of alumina.
Measurements of SEY in Photonis
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ALD alumina layers show high SEY than SiN and SiC!
Best values are obtained for conductive ’’Si rich’’ SiN (Si++N) and SiC substrates with thin 12.6
nm layer of alumina.
Std SiN substrate shows lower values and stronger charge-up effects.
For 25 nm alumina SEY is worse comparing to 12.5 nm thick alumina.
To be mentioned, starting from sample 5 the focussing of electron beam has been readjusted
(cathode was degraded). The beam was focused to about 1-2 mm dia spot, and charge-up
effect was more pronounced.
The SEY values for SiC measured at the same conditions should be a little bit higher reaching
max value of about 4.