ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
We have deposited silicon nitride films by plasma-enhanced chemical vapor deposition (PECVD) at 250 °C with properties similar to films prepared at 700 °C by low-pressure chemical vapor deposition (LPCVD). Films are prepared using silane and nitrogen source gases with helium dilution. The film properties, including N/Si ratio, hydrogen content and electrical quality are most sensitive to changes in the silane flow rate during deposition. For films deposited under optimized conditions at a substrate temperature of 250 °C, current versus voltage measurements in metal-insulator-semiconductor structures show the onset of carrier injection at 3–4 MV/cm, slightly lower than LPCVD films. When bias-stressed to 2 MV/cm, capacitance versus voltage measurements show some hysteretic behavior and evidence for positive fixed charge, similar to LPCVD films. For the optimized films: N/Si=1.33±.02; refractive index (λ=6328 A(ring))=1.980±0.01; dielectric constant (1 MHz) ∼7.5; density=2.7±0.1; and the etch rate in 10% buffered HF ranges from 32 to 70 A(ring)/min. In addition, the hydrogen is distributed equally in Si-H and N-H groups, with a total hydrogen content 〈10 at.%. These films have a significantly lower hydrogen content than observed in other PECVD silicon nitride films deposited at this temperature. When the substrate temperature is increased to 350 °C, the films have the same Si/N ratio, and similar electrical properties; the hydrogen content is reduced to 〈6×1021 cm−3, and the etch rate is 17 A(ring)/s in 10% buffered HF solution.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.349544
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