Photolithographic and chemical fabrication processes for three-dimensional LTCC-tape systems

This thesis deals with the development of fabrication techniques that make possible the use of Low Temperature Co-fired Ceramic (LTCC) Tapes for the construction of three-dimensional meso (intermediate) scale electro mechanical systems. We brought together technologies from the packaging, silicon and ceramics industries to develop a photolithographic technique for LTCC tapes. To that end, it was necessary to investigate and define an appropriate heat preprocess that we called partially sintering. Jet Vapor Etching is another patterning technique developed during this research effort. It has the advantage of being more directional than wet etching and therefore vias with high aspect ratio can be patterned. A jet of atomized solvent impinges on the surface of the LTCC tape dissolving the organic binder of the tape and mechanically removing the alumina and glass grains. When the vertical dimension is introduced, sagging problems appear; however, we solved these problems by using sacrificial materials and the appropriate atmosphere and firing profile. We also experimentally found the processing parameters for the photoformables LTCC tapes and showed that the diffusion model is a good candidate to model transport of light in the ceramic. The firing of photoformable LTCC is problematic because of non-uniform drying but it was resolved by constrain lamination. The discovery of the exfoliation phenomenon played an essential role in the development of a high temperature pressure sensor