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Comparison of Elastic Modulus of Very Thin DLC Films Deposited by r.f.-PACVD and FVA. Jin-Won Chung, Churl-Seung Lee, Dae Hong Ko * , Jun-Hee Hahn ** and Kwang-Ryeol Lee Future Technology Research Division, Korea Institute of Science and Technology
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Comparison of Elastic Modulus of Very Thin DLC Films Deposited by r.f.-PACVD and FVA Jin-Won Chung, Churl-Seung Lee, Dae Hong Ko*, Jun-Hee Hahn** and Kwang-Ryeol Lee Future Technology Research Division, Korea Institute of Science and Technology * Department of Ceramics, Yonsei University ** Korea Research Institute of Standard Science
High Residual Compressive Stress of DLC Films DLC Coating • Causes the Instability of the Coating • Affects the Physical Properties in Some Cases
Self Delamination of DLC Films • K.-R. Lee et al., Diam. Rel. Mater. 2 (1993) 208. • M.-W. Moon et al., Acta Mater., 50 (2002) 1219.
Key Idea of the Method For Isotropic Thin Films
Measurement of Residual Stress • Assumption • 1-D Treatment of Elastic Equilibrium • Sufficient Adhesion • df << ds • ds << R ds df R
Key Idea of the Method For Isotropic Thin Films
Preparation of DLC Bridge by Micro Fabrication SiO2 Isotropic Wet Etching Wet Cleaning DLC film Deposition ( on SiO2 ) Strain Estimation DLC Patterning
Microstructure of DLC Bridges 150mm C6H6, 10mTorr, -400V, 0.5mm
Preparation of Free-overhang by Anisotropic Substrate Etching Si Etching (by KOH Solution) Wet Cleaning DLC film Deposition Cleavage along [011] Direction Strain Measurement
Elastic Modulus for Various Ion Energies Nanoindentation t>1.0 ㎛
Advantages of This Method • Simple • Completely Exclude the Substrate Effect • Can Be Used for Very Thin Films • The possibility of elastic modulus measurement in very thin film
a-C:H, C6H6 -400V ta-C (-50Vb) Elastic Modulus of Very Thin Films J.-W. Chung et al, Diam.Rel. Mater. 10 (2001) 2069.
RF PACVD (13.56MHz) Precursor : CH4 Vb/ P1/2 : 20 ~ 233 Vb/mTorr1/2 Substrate : P type (100) Si Film Thickness : ~ 50nm Synthesis of DLC Film by r.f.-PACVD
Biaxial Elastic Modulus 100 20
Biaxial Elastic Modulus 100 166 20
Biaxial Elastic Modulus 100 166 233 20
G-peak Position of Raman Spectra 100 233 166 166 100 233 20 20
Si Substrate 233 166 100 20 Si Substrate Schematic Film Structure Si Substrate
Synthesis of ta-C Films • ta-C films on Si (100) Wafer • Vb : from 0 to –500V
Summary • Presently suggested method for the elastic modulus measurement enabled us to compare the mechanical properites and thus the atomic bond structures of very thin amorphous carbon films. • ta-C films showed insignificant structural evolution during the initial period of deposition. • a-C:H showed the significant structural evolution in both polymeric and graphitic film deposition condition. • a-C:H film deposited in optimum ion energy condition didn’t show the structural evolution.