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Photolytic silicon nitride deposition for gallium arsenide by 193 excimer laser radiation

Photolytische Abscheidung von Siliziumnitrid auf GaAs mit 193 nm Laser Bestrahlung
: Rothemund, W.; Dischler, B.; Eisele, K.M.

Vacuum 41 (1990), Nr.4-6, S.1081-1083 : Abb.,Lit.
ISSN: 0042-207X
Fraunhofer IAF ()
laser CVD; silicon nitride; Silizium Nitrid

GaAs technology requires low temperature processes for any film deposition. Furthermore, processes without particle bombardment are also preferred, two conditions which photolytic deposition does fulfil. An excimer laser beam of 20 x 1 qmm cross-section skimmed over the wafer surface at 0.2 mm distance. The feed gases used were monosilane, NH sub 3 and NF sub 3. At a temperature of 150 degree C, an oxide was obtained containing almost no nitrogen. With higher temperatures the nitrogen content of the film increased raising the index of refractive correspondingly, while the deposition rate decreased. The deposition per pulse was proportional to the pulse energy by a factor of 6.25 A min high -1 mJ high -1, but decreased with increasing pulse frequency, indicating a diffusion-limited deposition rate. The films have been analysed by ellipsometry, by quantitative energy dispersive electron microprobe measurements and also by ir absorption. When 50% of NF sub 3 was substituted for the same a mount of the NH sub 3 gasflow, the peak of the Si-H sub n bond did not decrease. We conclude that this is due to the insufficent absorption of the laser radiation by the NF sub 3, as the deposition rate reduced to almost zero when only NF sub 3 and no NH sub 3 was used.