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

Abstract

Silicon nitride (SiN x ) thin films are crucial in electronic devices and are used as gate dielectrics and diffusion barriers for thin-film transistors (TFTs). Plasma-enhanced chemical vapor deposition (PECVD) has been used for the deposition of SiN x thin films because it allows the tuning of the properties of SiN x thin films by changing the deposition conditions depending on their usage. However, the intrinsic mechanical properties of SiN x thin films depending on the PECVD conditions have rarely been studied because of extreme brittleness and inherent residual stress of SiN x thin films. In this study, the intrinsic mechanical properties of PECVD SiN x thin films are measured from free-standing tensile tests. For the test, 130−150 nm-thick SiN x thin films are prepared using three types of PECVD conditions to induce tensile (T-SiN x ), neutral (N-SiN x ), and compressive (C-SiN x ) residual stress. Compared with the T-SiN x thin films (77 GPa, 0.10%, and 83 MPa, respectively), the C-SiN x thin films shows an approximately 45% increase in Young's modulus (112 GPa), a twofold enhancement of the elongation (0.21%), and a threefold improvement in the fracture strength (226 MPa). The improved intrinsic mechanical properties of C-SiN x thin films compared with those of the T-SiN x and N-SiN x thin films are attributed to increased film density (2.42−2.64 g/cm 3 ) and reduced dangling H of the N−H bonding, which are induced by their deposition conditions of higher RF power, lower chamber pressure, and lower NH 3 feed ratios. We anticipate that the mechanism of changing the mechanical properties can be extended to fabricate mechanically robust SiN x thin films as dielectric layers for flexible devices.

Elucidating the effect of Ag interlayer formation on the intrinsic mechanical properties of free-standing ITO/Ag/ITO thin films

“…Additionally, the effect of residual stress was excluded because the IAI thin films on the water surface could freely release the substrate constraint. 33 Moreover, the effect of surface roughness was negligible because there was no significant difference in root mean square roughness ( R q ) with respect to the Ag interlayer thickness (Fig. S5, ESI†).…”

Study of mechanical degradation of freestanding ALD Al2O3 by a hygrothermal environment and a facile protective method for environmentally stable Al2O3: toward highly reliable wearable OLEDs

“…ALD Al 2 O 3 films after exposure to a hygrothermal environment can be considered bilayers composed of degraded and pure ALD Al 2 O 3 . The E values of the bilayer thin films were calculated using eqn (1), which is a method of approach to approximate estimation of composite material properties, called the rule of mixture: 35–37 E b = E u *( t u / t b ) + E d *( t d / t b ) ≈ E u …”

“…It is well known that the mechanical reliability of ceramics is highly dependent on surface conditions, such as cracks, pores, flaws, residual stress, and surface roughness. 38,39 Previous studies have reported that the e and S of brittle materials such as Al 2 O 3 are improved with decreased surface roughness. 38,40 Cheng et al conducted a digital image correlation analysis and showed a recognizable stress concentration at the valleys of a rough surface, where the stress concentration was induced around the pores, reducing S and e. 41 In addition, the interaction between the pores and other defects, such as pores and cracks, can affect the stress concentration and risk of crack propagation.…”

Intrinsic Thermomechanical Properties of Freestanding TEOS-SiO2 Thin Films Depending on Thickness

“…It is worth noting that excessive tensile residual stress can result in selfcracking during the delamination of the thin film, making it challenging to accurately measure its mechanical properties. 27 Lastly, the dielectric constant of the TEOS-SiO 2 film was explored to gain insights into the changes in mechanical properties. The dielectric constant is a coefficient related to the material's porosity 28,29 and has a positive correlation with Young's modulus.…”