Transfer of small structures by bonding
The work presented in this paper deals with the bonding of small structures, down to 1 mu m. Its aim is to evaluate the dimensional limits of anodic bonding between silicon and pyrex 7740 glass. Test structures consisting in silicon pillars with controlled radii have been developed. The silicon pillars have been fabricated by deep reactive ion etching to allow a good geometry control of the structures. A collection of matrices of 3 x 3 identical silicon test structures with dimensions from 200 to 1 mu m has been fabricated to determine the smallest area that can bond anodically. The test results have been applied to the transfer of small structures from one wafer to another wafer by bonding, with the final objective of transferring tips for A FM probes. From the test results, a new test for bonding has been defined, based on the Pull test of small structures with controlled dimensions. Preliminary simulations by FEM of the pull test of the test structures are in agreement with the experimental results. The test has been used to determine the effect of the voltage and temperature conditions during the anodic bonding on the bond strength.