Detailed characterization of anodic bonding process between glass and thin-film coated silicon substrates

Anodic bonding between Si-based and glass substrates has been characterized in detail. The effects of magnitude of the applied voltage, surface properties (coating of Si substrate), and surface cleanliness (pre-bonding cleaning procedure) on the time required for complete bonding were thoroughly studied. First, the generic bonding time versus applied voltage plot was found to be concave in shape (viewed from the origin). For bonding between p-type Si substrate and Coming 7740 glass pre-cleaned with acetone, the time required was cut down from 38 to 4 min if the applied voltage was increased from 200 to 500 V. Second, the bonding time required for five Si-based substrates in ascending order was determined to be Si (p-type), polysilicon, silicon nitride, silicon oxide and then Si (n-type). Third, the bonding between p-type Si substrate, pre-cleaned with H2SO4-H2O, and HF, and Coming 7740 glass was completed within 1 min, which was much faster than that pre-cleaned with acetone (4 min). Finally, from bonding point of view, Coming 7740 glass was superior to Coming 7059 glass and Fisher slide due to its thermal coefficient of expansion matching with the underlying Si substrate and the presence of significant amount of sodium ions in the glass. (C) 2000 Elsevier Science B.V. All rights reserved.