Economies of Scale
Posted date : May 27, 2009

For Silex Microsystems, SOI and TSI™ substrates figure among the company’s key starting materials.

Silex’s Through Silicon Via technology, marketed as Sil-Via™, can be incorporated into the handle side of an SOI wafer, allowing the combination of a highly doped handle wafer and a low doped device layer.

Silex Microsystems is the worldwide leading pure-play MEMS foundry, providing state-of-the-art, complete manufacturing capability in its two fabs (6” & 8”). Silex customers are found in the medical, biotech, telecommunications, consumer electronics and automotive industries. With its brand new 8” inch fab, unparalleled in the MEMS foundry industry, Silex provides the industry’s most advanced process technologies in combination with state-of-the-art tool capability. SOI substrates and the company’s proprietary TSI™ technology are widely used in all the market segments of the products manufactured by Silex.

SOI technology

Among the advantages of using SOI, one can name the superior device performance or the high reproducibility obtained. The BOX layer is often used as an etch-stop and to release 3D structures (e.g. for gyros, accelerometers). SOI wafers also enable us to manufacture devices that would not be possible with conventional silicon substrates (e.g. for micromirrors).

Last but not least the increase of yield and the decrease of the manufacturing costs (due to better process control and reduced number of processing steps) enabled by the use of SOI are especially interesting when it comes to production. This naturally has to be balanced with the extra initial cost of the SOI substrate compared to a standard silicon substrate, but very often it is more advantageous to start with SOI.

Complementary processes

Many MEMS products comprise a combination of analogue and digital signal processing. The typical sensor readout for MEMS sensors is analogue but also incorporate digital signal processing, taking place in an ASIC, flip chip mounted to the MEMS die. In many cases, the system will be sensitive to signal contamination between the analogue and digital side of the system.

With Silex’s TSI technology, isolators are buried vertically into the wafer. The TSI technology can be used to create through silicon vias (TSV). Silex is marketing this proprietary through-silicon wafer interconnect process under the brand name “Sil-Via™”.

TSI can also be used to separate certain regions of an IC chip from a MEMS die in order to reduce signal contamination and crosstalk. Silex is offering this feature of the TSI technology under the brand name Zero-Crosstalk™.

The advantages of SOI- and TSI-based MEMS devices can offer substantial economies of scale, just when the industry needs it most.

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