A study on the residual stress measurement methods on chemical vapor deposition diamond films
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A study on the residual stress measurement methods on chemical vapor deposition diamond films Jung Geun Kim and Jin Yu Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, P.O. Box 305-701, Kusung-Dong 373-1, Taejon, Korea (Received 9 January 1998; accepted 7 April 1998)
Diamond films were deposited on the p-type Si substrate with the hot filament chemical vapor deposition (HFCVD). Residual stresses in the films were measured in air by the laser curvature, the x-ray diffraction (XRD) dfc 2 sin2 c, and the Raman peak shift methods. All of the measuring methods showed similar behaviors of residual stress that changed from a compressive to a tensile stress with increasing the film thickness. However, values of residual stresses obtained through the Raman and XRD methods were 3–4 times higher than those of the curvature method. These discrepancies involved the setting of materials constants of CVD diamond film, and determination of a peak shifting on the XRD and Raman method. In order to elucidate the disparity, we measured a Young’s moduli of diamond films by using the sonic resonance method. In doing so, the Raman and XRD peak shift were calibrated by bending diamond/Si beams with diamond films by a known amount, with stress levels known a priori from the beam theory, and by monitoring the peak shifts simultaneously. Results of each measuring method showed well coincidental behaviors of residual stresses which have the stress range from 20.5 GPa to 10.7 GPa, and an intrinsic stress was caused about 10.7 GPa with tensile stress.
I. INTRODUCTION
Chemical vapor deposition (CVD) diamond film has been a subject of intense research and development for the past several decades because of its unique electronic, optical, thermal, and mechanical properties.1–3 However, despite having many excellent properties, in practice, it has been restricted to use as a poor adhesion with substrate.4,5 Many investigators6,7 concluded that the reason for poor adhesion is due to a high residual stress in the films. Therefore, understanding the origins of thin film stresses and their exact measurement are of great technological importance in order to make ubiquitous applications of diamond films possible. Residual stresses in thin films are typically measured by the curvature method, x-ray diffraction (XRD), and Raman peak shift methods. The curvature method employs parallel incident laser beams where monitoring of the position of reflected beams gives the wafer curvature and the residual stress in a direct manner with the aid of Stoney’s equation.8 The peak shift methods are more indirect and can be useful where the film curvature cannot be monitored. Both methods note that positions of diffracted x-ray beam or Raman peak are shifted as crystals are elastically distorted under stress. However, among the experimental data obtained using the three methods, measured stress values vary widely, and often differ in sign even though they have the same di
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