Thermal treatment effects on hard and soft films measured by nanoindentation test
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S.C. Lee Department of Materials Science and Engineering, National Cheng-Kung University, Tainan 701, Taiwan
C. Wei Department of Mechanical Engineering, Tatung University, Taipei 104, Taiwan
P.J. Wei and J.F. Lin Department of Mechanical Engineering, National Cheng-Kung University, Tainan 701, Taiwan (Received 29 July 2008; accepted 13 November 2008)
Nanoindentation measurements using the Berkovich diamond tip with a load up to 700 and 210 mN were performed on 1-mm hydrogenated diamond-like carbon (DLCH) films and 6-mm polyimide (PI) films under different thermal treatment. The average nanohardness and elastic modulus from nanoindentation measurements are 25.13 and 192.18 GPa for as-deposited DLCH film and 22.93 and 174.22 GPa for as-annealed DLCH film, respectively. The ID/IG ratio of Raman spectra is 1.72 for as-deposited DLCH film and 2.04 for as-annealed DLCH film. The average nanohardness and elastic modulus from nanoindentation measurements are 0.37 and 5.58 GPa for 300 C as-cured PI film and 0.42 and 5.19 GPa for 400 C as-cured PI film, respectively. The relative cured rate is 92.1% for 300 C as-cured PI film and 100% for 400 C as-cured PI film. Both the nanohardness and elastic modulus derived from nanoindentation test results can correlate well with the trend of Raman spectra and FTIR spectra for hard DLCH film and soft PI film under different thermal treatment effects.
I. INTRODUCTION
For academic research and industrial application, diamond-like carbon (DLC) and polymer (PI) films can be viewed as the hard and soft films, and both of them can be used in ICs device as passivation layers due to their low-k property. To improve the reliability, thermal treatment is an effective method in which the mechanical properties of thin film can be tailored from simulation test.1 It is noteworthy that nondestructive optical apparatuses such as Raman (for DLC) or FTIR (for PI) are a quick and low cost method. In contrast, nanoindentation is a destructive and high cost method, where the hardness and elastic modulus of the films can be obtained to evaluate the performance. Raman is a suitable apparatus to analyze the annealed properties of DLC films,2 and many reports have shown that the mechanical properties of
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0080 J. Mater. Res., Vol. 24, No. 3, Mar 2009
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DLC films can be assessed by the nanoindentation test.3,4 However, the research for the relationship between Raman spectra and nanoindentation under thermal treatment is difficult to find.5,6 For PMDA-ODA polyimide films, many reports have shown the characteristics of the polyimide films are strongly affected by the thermal treatment for temperature varies from 250 to 400 C7,8 In evaluation of curing degree, Fourier transform infrared spectrometer (FTIR) is a feasible apparatus to verify the chemical bonding of polymer material. On the other hand, the ATR-FTIR model can be used to measure the curing
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