Plasma polymerized hexamethyl disiloxane in adhesion applications

The plasma polymer of hexamethyl disiloxane (HMDSO) was investigated as an adhesive for the gluing of silicon-to-silicon for potential application in microelectronic device and sensor fabrication. The aim of this work was to determine whether nm-thick films of HMDSO deposited in excess oxygen could be used as an adhesion layer for the bonding of silicon or glass to itself or other materials. The adhesive should be stable at high temperature and it should not outgas. The chemical nature of the thin films was analysed using Fourier transform infra red spectroscopy (FTIR) and contact angle measurements. Thermal stability was investigated using gas chromatography combined with mass spectroscopy (GC/MS). Adhesive strength was determined using an Instron tensile testing apparatus. Results show that a combination of plasma surface modification and plasma deposition reactions allow for the fabrication of Si–Si sandwiches that show shear strength up to 6 MPa, which would be sufficient for bonding applications in many microelectronic devices. The deposited materials were temperature stable. Sources of errors and methods to overcome these are discussed.