DEPTH-PROFILES WITHIN GLASS SAMPLES FROM ANODIC BONDING EXPERIMENTS WITH COPPER USING SNMS

The bonding of copper plates to Pyrex 7740 glass has been studied for the encapsulation of microstructures fabricated with the LIGA technique. Although sufficient to join silicon to glass with 1 kV bonding voltage and 300-degrees-C, successful bonds of copper to glass could not be obtained. Depth-profiles using plasma-based SNMS with 410 eV argon ions were measured to check for migration processes within the glass component. To prevent charging of the insulating samples a 100 mpi woven Ta grid was used. Detection factors for the relevant elements were found to be unaffected by the grid. A matrix dependence of ca. +/- 30% was found. The depth resolution was 30 nm using the grid. The analysis of the glass after bonding attempts showed that massive migration of copper into the glass is probably preventing the necessary electrostatic attraction of the components at high temperatures. The temperature dependence of the copper migration was shown to increase steeply above 200-degrees-C. Insufficient sodium ion mobility prevents stable bonding at lower temperatures.