An oxidized porous silicon (OPS) microlens implemented on thick OPS membrane for a silicon-based optoelectronic-multichip module (OE-MCM)

Using the silicon bulk micromachining and selectively oxidized porous silicon (SOPS) technology, a silicon dioxide microlens was implemented on thick oxidized porous silicon (OPS) membrane. Because the surface of microlens was the interface of OPS-Si, the surface roughness of lens was directly affected by the anodization current density, substrate resistivity, and high-frequency percent in ethanol-contained electrolyte. In the SOPS technology, the porous silicon layer (PSL) was formed under the mask layer with its horizontal-vertical ratio of about 0.8. During the formation of lens part, Si₃N₄ mask layer was also etched with constant etch rate and the PSL formed on the masked area was used as a membrane supporter. The initial open area and the thickness of the mask layer controlled the focal length of the OPS lens and its range was from 20 to 110 μm. By using these microlenses, a new silicon-based optoelectronic-multichip module configuration was proposed.