Synthesis and characterization of low-k films for large area imaging applications

An organic liquid polymer based on methyltriethoxysilane has been synthesized. The material;when spin-coated onto wafers and thermally treated;lead to dielectric films of low permittivity;which can be used in hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) based large area imaging arrays as an inter-level dielectric between the TFT and pixel levels. Fourier Transform Infrared Spectroscopy (FTIR) shows prominent peaks of Si-CH3 stretch and Si-O stretch modes. The dielectric constant (k) of the film was found to decrease with increasing curing temperature (Tcure). However;k values were < 3 for Tcure < 260 °C;which is the upper limit for our a-Si:H process. Thermogravimetric analysis showed that major weight loss takes place for up to 200 °C;and the film stabilizes thereafter. The stress in the films was found to be compressive;and increased from 50 to 220 MPa when Tcure was increased from 250 to 450 °C. The low stress for low Tcure is a desirable property for film integration.