Mechanical properties of surface modified silica low-k thin films

• A sol–gel deposited low-k thin film was surface modified by using wet chemical treatment.
• Change in chemical structure was analyzed by using FTIR spectroscopy.
• The hydrophobicity of surface modified films was revealed by using water contact angle.
• Hardness and modulus of low-k films was determined by Nanoindentation technique.
• The film surface modified at 20% TMCS, observed to have lowest dielectric constant of 2.58.

The surface modification of sol–gel deposited low-k thin films has been carried out successfully by trimethylchlorosilane (TMCS) using wet chemical treatment method. Ellipsometer is used to determine the thickness of films. The changes in chemical structure after surface modification of the films have been verified by using FTIR spectra analysis. The appearance of peak around 2800–2900 cm−1 after surface treatment of low-k films confirms the incorporation of non-polar and hydrophobic group (–CH3). The water contact angle of as-deposited films (85°) is observed to be increased up to 102° after surface treatment using 20% TMCS concentration in hexane. This significant change in the water contact angle confirms the modification of film’s surface from hydrophilic to hydrophobic. The properties such as hardness (3.22 GPa) and elastic modulus (75 GPa) of surface modified low-k films using 20% TMCS have been determined by Nano-indentation technique. Dielectric constant of the film is observed to be lowered from 3.56 to 2.58 after surface treatment.

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