Modified silicon oxide barrier coatings produced by microwave CVD deposition on polymeric substrates

A composite material having an oxygen transmission rate of less than about 2.0 cm.sup.3 /m.sup.2 /day at room temperature and 0% relative humidity and a water vapor transmission rate of less than about 3 g/m.sup.2 /day at 38.degree. C. and 100% relative humidity including:

• a microwave-plasma-enhanced-chemical-vapor-deposited silicon oxide barrier coating;
• said barrier coating is 100 to 500 Angstroms thick and being substantially free of Si--H bonds;
• and
• a temperature sensitive substrate, said coating deposited atop said temperature sensitive substrate;
• said composite having been produced by the method including the steps of:
• providing an evacuable deposition chamber having a deposition region defined therein;
• providing a source of microwave energy;
• providing said temperature sensitive substrate within said deposition region in said deposition chamber;
• evacuating said deposition chamber to a sub-atmospheric pressure;
• performing a plasma pretreatment of said temperature sensitive substrate;
• introducing a precursor gaseous mixture into said deposition region within said deposition chamber, said precursor gaseous mixture including at least a silicon-hydrogen containing gas and an oxygen containing gas;
• directing microwave energy from said source of microwave energy to said deposition region, thereby creating a plasma in said deposition region by interaction of said microwave energy and said precursor gaseous mixture;
• depositing from said plasma, onto said temperature sensitive substrate, said silicon oxide barrier coating, said coating providing the coated substrate with oxygen and water vapor barrier properties greater than the non-coated substrate;
• and
• introducing a sufficient flow rate of oxygen-containing gas into said precursor gaseous mixture to substantially eliminate the inclusion of silicon-hydrogen bonds into the deposited coating.