Papers by Keyword: Intrinsic Stress

Abstract: The polycarbonate (PC) screw cap part had cracking problem during storage, which mechanism needed to be studied. The effect of mechanical processing on the intrinsic stress and its distribution in PC screw cap part was investigated in the paper. The analytical results indicated that the round pieces cut from polycarbonate bar had certain intrinsic stress residue from processing course, which decreased obviously after de-stress heat treatment. Mechanical processing also led to obviously increased intrinsic stress in screw cap part, which could be decreased obviously by another de-stress heat treatment. But the heat treatment increased the aging degree and cracking probability for polycarbonate screw cap part, and was not suggested to carry out on screw cap. Based on the experimental results, some suggestions were also given to lower the intrinsic stress in screw cap.

Abstract: Technique of bulk-like 3C-SiC film (up to 300 µm) growth on undulant-Si substrate is known to be very effective to reduce stacking fault density as well as that of other planar defects. However, freestanding 3C-SiC wafer shows anisotropic warpage involving large convex curvature in the direction perpendicular to the ridge of undulation ([110] direction), and slight concave curvature in parallel direction ([-110] direction), i.e. saddle shape. In this paper the origin of the warpage of the 3C-SiC wafer is investigated. Ex-situ curvature measurements and stress calculation reveal that large compressive intrinsic stress is generated during high-temperature growth process (1623 K) in both parallel and perpendicular directions. In order to investigate the intrinsic stress distribution along the [001] direction, a reactive ion etching (RIE) is conducted for the 3C-SiC on Si substrate to observe the dependence of the SiC/Si system curvature as a function of 3C-SiC thickness. This observation shows that the intrinsic stress component perpendicular to the ridge of undulation presents nonuniform distribution in [001] direction. The remarkable change in the intrinsic stress is observed in the 50 µm-thick region from SiC/Si interface. A finite element method simulation using the obtained intrinsic stress distribution clearly explains that the anisotropic warpage of SiC wafer is induced by the intrinsic stress distribution in quantitative manner. Microstructure change induced by stacking fault reduction process (stacking fault collision) would be the cause of the intrinsic stress variation.

Abstract: High residual stress that includes thermal and intrinsic stress is an obstacle to the further application of chemical vapor deposited diamond thick film. In this paper, CVD diamond thick film was deposited on silicon substrate by hot filament chemical vapor deposited (HFCVD) system. The finite element analysis (FEA) simulation and experimental research were carried out on the thermal and intrinsic stress of large area diamond thick film. The FEA model is set up to investigate the distribution and magnitude of thermal stress. The intrinsic stress is studied by X-Ray diffraction “sin2ψ” method. The thermal stress and intrinsic stress are both compression stress. Simulation results show the discontinuous sharp of the diamond film result in the stress concentration and low cooling velocity is a good way to reduce thermal stress. The intrinsic stress is correlative with the microstructure and non-diamond component of diamond film. The origin of the intrinsic stress is discussed in detail in this paper.

Abstract: Titanium containing carbon nitride (CNx) films are prepared by radio frequency magnetron sputtering method. The evolution of intrinsic stress within the nanocomposite films is monitored during growth by using an in situ bending-plate method. The effect of Ti-containing concentration on intrinsic stress is investigated. XRD data shows that TiN nanocrystals are synthesized to embed into the CNx matrix. The film intrinsic stress depends obviously on the content of Ti. We suggest that grain boundary effect is responsible to the intrinsic stress variation as a function of the content of Ti.

Abstract: A laser beam profilometry technique was used to investigate residual stress accumulation during TiN deposition and stress relaxation during post-deposition heat treatment. The test coatings were reactively sputtered on silicon and steel substrates using a UMS technique. TiN coatings, deposited at different bias and pressure levels, were evaluated for residual stress and microhardness. It was found that both the residual stress and the hardness were strongly affected by the coating deposition conditions. In addition, stress-temperature correlations were obtained by subjecting the coatings to temperature cycles up to 450°C. Stress-temperature plots revealed that the level of residual stress relaxation depended on deposition conditions and only coatings deposited at low ion bombardment could be fully annealed. The role of intrinsic and thermal stresses in the total residual stress in the coating/substrate system was also discussed.