IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Microelectromechanical Systems (MEMS) Thursday Sessions
       Session MM-ThA

Paper MM-ThA9
Elimination of Defects on Quartz Plate Surface Induced by Deep Drying Etching and Subsequent Quartz Plate Bonding

Thursday, November 1, 2001, 4:40 pm, Room 130

Session: Fabrication and Integration Processes for MEMS
Presenter: T. Fukasawa, The University of Tokyo, Japan
Authors: T. Fukasawa, The University of Tokyo, Japan
H. Ogawa, The University of Tokyo, Japan
Y. Horiike, The University of Tokyo, Japan
Correspondent: Click to Email
Two issues were studied for fabrication of a microcapillary on a quartz plate in the Bio-MEMS chip. One is generation of the cone-like defects on the quartz bottom surface which were etched deeply with fluorocarbon plasmas. The other is less tight bonding of a pair of quartz plate which is performed at 1.3 MPa, RT and 24 hours following dipping them in a 1% HF solution. In the former issue, we noticed that defects were distributed randomly, nevertheless these diameters were almost same. Increasing RF-s elf bias voltage (Vdc) decreased the number of defects. No defect was observed on the quartz surface at high Vdc of 940V, while the masking Cr film was eroded considerably. The results imply that certain masking materials remain on the quartz surface after its finishing, while AFM and XPS measurement of the surface do not reveal the origin of materials at present. Hence, at first high Vdc of 900V added to the sample during 2 min. to remove the mask materials by sputtering, and then Vdc was decreased down to 500V to etch the quartz plate. Eventually, no defects and high etch selectivity to the Cr mask was achieved. For the latter issue, the quartz bonding mechanism was studied employing an in-situ IR-ATR spectroscopy. 10wt % HF solution was introduced between a quartz plate and a trapezoidal Ge prism whose surface was covered by a sputtered grown SiO@sub 2@ film with 70nm thickness. Elapse time dependence of IR absorption spectra was measured under 5 MPa. H@sub 2@SiF@sub 6@ was observed at the interface and this intensity decreased with increasing the pressing time. Thus the bonding mechanism was considered as follows: At first, H@sub 2@SiF@sub 6@ is produced by etching of SiO@sub 2@ in a HF solution, then it changes to SiO@sub 2@ at presence of H@sub 2@O, thereby acting as a paste layer to bind both surfaces. Based on the mechanism, high strength bonding of quartz plates was performed successfully using a H@sub 2@SiF@sub 6@ solution instead of a 1% HF one.