Silicon to Silicon Wafer Bonding at Low Temperature Using Residual Stress Controlled Evaporated Glass Thin Film
Silicon to silicon wafer bonding at low temperature of 300 °C using residual stress controlled evaporated 2 ㎛ thick Pyrex glass thin film (briefly, glass thin film) on silicon wafer was investigated. It was found that residual stresses of 2 ㎛ thick glass films on silicon wafers were strongly dependent upon moisture contents and annealing processes. Residual stresses of asdeposited glass films with compressive stress of -150 MPa could be changed to more compressive stress of -230 MPa by moisture absorption. However, after annealing process at 200 °C to 400 °C for 30 min, residual stresses were remarkably changed to tensile stresses of about 75 MPa to 130 MPa, respectively. For the reliable wafer bonding process, the evaporated glass thin films should be annealed in the range of 200 °C to 500 °C for 30 min. So, bare silicon to bare silicon and bare silicon to patterned silicon were bonded at 300 °C and 30 V ~ 60 V for 15 min using 2 ㎛ thick glass film with residual stress of 130 MPa which were generated after the annealing process of 400 °C for 30 min. These results could be used for low temperature silicon to silicon wafer bondings for applications of micro sensors, micro actuators and micro fluidics devices.
Hyung Sun Kim, Yu Bao Li and Soo Wohn Lee
J. S. Park et al., "Silicon to Silicon Wafer Bonding at Low Temperature Using Residual Stress Controlled Evaporated Glass Thin Film", Materials Science Forum, Vols. 510-511, pp. 1054-1057, 2006