Structural evolution and mechanical properties of nitrogen doped hydrogenated amorphous silicon thin films

Abstract

Nitrogen doped hydrogenated amorphous silicon thin films, also recorded as silicon rich hydrogenated amorphous silicon nitride thin films, were deposited by plasma enhanced chemical vapor deposition. The structural evolution and mechanical properties of the films with different nitrogen contents were studied by Fourier transform infrared spectroscopy, Raman scattering spectroscopy, and the density and stress measurement system, respectively. The results showed that with the increase in ammonia gas flow rate from 0.5 SCCM to 20 SCCM, the tensile stress and the density of the films decreased from 600 MPa to 280 MPa and from 2.31 g/cm3 to 2.08 g/cm3, respectively. The hydrogen bonding configurations, hydrogen content, and structural ordering evolution were investigated to reveal the relationship between the structural and mechanical properties of the films. A qualitative model was proposed to explain the role of nitrogen and hydrogen atoms during the film growth.

Intrinsic Mechanical Properties of Free-Standing SiNx Thin Films Depending on PECVD Conditions for Controlling Residual Stress

“…10−12 One of the ways to control the residual stresses of SiN x thin films as intended (tensile, neutral, and compressive) is to change the PECVD conditions, such as the substrate temperature, plasma power, chamber gas pressure, and feed gas ratio. 13,14 Although varying the PECVD conditions may change the intrinsic mechanical properties of the SiN x thin films, the intrinsic mechanical properties of free-standing SiN x thin films, such as Young's modulus, elongation, and fracture strength, have not been studied. Therefore, exploring the intrinsic mechanical properties of SiN x thin films deposited under different processing conditions to control residual stress is essential to ensure the mechanical reliability of flexible devices.…”

“…Controlling the residual stress is an important step in the process of deposition of SiN x thin films because high residual stress in SiN x thin films can cause structural deformation (such as buckling, delamination, and cracking); therefore, it is critical for mechanical reliability of devices. , One of the methods for compensating the built-in residual stress involves applying the SiN x thin films with a residual stress opposite to the adjacent layers (such as gate metal, barrier, and anode). − One of the ways to control the residual stresses of SiN x thin films as intended (tensile, neutral, and compressive) is to change the PECVD conditions, such as the substrate temperature, plasma power, chamber gas pressure, and feed gas ratio. , Although varying the PECVD conditions may change the intrinsic mechanical properties of the SiN x thin films, the intrinsic mechanical properties of free-standing SiN x thin films, such as Young’s modulus, elongation, and fracture strength, have not been studied. Therefore, exploring the intrinsic mechanical properties of SiN x thin films deposited under different processing conditions to control residual stress is essential to ensure the mechanical reliability of flexible devices.…”