R. Wolf et al., Low-temperature ICPECVD of silicon nitride in SiH4-NH3-Ar discharges analyzed by spectroscopic ellipsometry and etch behavior in KOH and BHF, SURF COAT, 142, 2001, pp. 786-791
Low-temperature (80-130 degreesC) high-quality silicon nitride was grown on
Si substrates using a SiH4 (5%, in He)/NH3/Ar chemistry and ICPECVD techno
logy. The influence of percentage SiH4, temperature, chamber pressure and s
ource power on the wet etch rate, deposition rate, refractive index at 632.
8 run and extinction coefficient at 320 nm was investigated. The SiNx films
were characterized by spectroscopic ellipsometry and by the etch rate in K
OH and BHF. The lowest etch rates (BHF, KOH) are found for nearly stoichiom
etric silicon nitride with a refractive index close to 2 and deposition rat
es above 40 nm min(-1). The etch rates at 130 and 80 degreesC were only two
- and four-fold, respectively, higher than those for LPCVD SiN (780 degrees
C). The mechanical stress of these films is compressive and below 0.1 GPa.
To check the surface temperature during ICPECVD, we deposited a 200-nm-thic
k silicon nitride layer at 90 degreesC on a photoresist degrading at temper
atures above 100 degreesC. A 50-nm-thick SiNx film was used as a capacitor
layer using lift-off techniques. This film showed a breakdown field strengt
h of 4 MV cm(-1). These films were also deposited on InGaAs Mesa diodes. Af
ter removal, no damage by the ICPECVD process could be found by comparing t
he reverse current before deposition and after removal of the SiNx, film. (
C) 2001 Elsevier Science B.V. All rights reserved.