| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 736896 | Sensors and Actuators A: Physical | 2015 | 7 Pages |
•ICP-CVD SiN thin film properties are tailored by auxiliary capacitively coupled plasma.•Concurrent processes govern the film growth, according to the applied plasma power.•Abrupt occurrence of compressive stress up to 2.5 GPa is observed.•Direct links between the physical properties and chemical composition are identified.
In this study, we report on the properties of amorphous hydrogenated silicon nitride (a-SiNx:H) thin films synthesized by inductively coupled plasma enhanced chemical vapour deposition (ICP-CVD), combined with an auxiliary capacitively coupled plasma excitation. Physical properties, such as the deposition rate, refractive index and film stress, as well as the chemical composition, microstructure and etch resistance of the samples were investigated. Depending on the capacitively coupled plasma power PRF, two regions can be distinguished which are dominated either by an increased generation of plasma radicals or by an enhanced ion bombardment. At PRF = 35 W, a maximum in the deposition rate is observed as well as an abrupt change in the chemical composition, resulting in an extremely high (>2.5 GPa) compressive stress, in comparison to the layers deposited with PRF = 0. In addition, the wet etch rate in hydrofluoric acid (HF) decreases substantially. Above, up to PRF = 150 W, ion bombardment of the growing film surface is more pronounced due to an increased self-bias of the substrate decreasing the effective deposition rate. Fourier-transform infrared spectroscopy measurements indicate that this behaviour is in close relation to the NH bond density in the samples. Additionally, the continuous increase of the refractive index and SiH bond density, accompanied by the redshift of the SiN infrared absorption peak show that with higher PRF the Si content of the films increases.
