Building Microstructures One Slice at a Time

Originally Published MDDI November 2002

MACHINING

As medical components shrink to microdimensions, manufacturers are pushing the limits of conventional machining techniques such as CNC and EDM. Microelectromechanical systems (MEMS) manufacturing processes are an alternative, but these processes are often slow and complex.

So MEMGen Corp. (Burbank, CA) has introduced a fabrication process designed to deliver finished microstructures just days after they're designed. The process, called EFAB, uses a patterning technology called Instant Masking. By eliminating many of the steps in conventional photolithography, Instant Masking makes it possible to rapidly deposit cross-sectional layers of a structure. As the EFAB process proceeds, these layers stack up to form complex three-dimensional shapes.

EFAB creates layers by depositing two different materials: the structural material and a so-called "sacrificial" material (usually copper) that supports the structural material during fabrication. To start the process, the Instant Mask and a substrate are brought into contact in an electrodeposition bath. A current triggers the deposition of material onto the unmasked areas of the substrate (see the illustration). The second material is then electroplated onto the entire exposed surface. Next, a polishing operation takes the second material off the first, leaving a flat layer consisting of the two deposited materials.

These steps are repeated over and over until all the layers have been deposited. Then a selective chemical etch removes the sacrificial material, leaving the finished device.

According to MEMGen, EFAB can create 3-D micromachines with features as small as 0.001 in. and dimensional tolerances of less than 0.0001 in. In theory, at least, these machines can be made of large numbers of layers.

"MEMS devices tend to be rather flat. The state of the art is about five layers," notes Dan Feinberg, MEMGen's director of sales. EFAB, by contrast, has already produced 38-layer structures. Soon, Feinberg adds, the process may be making devices of 100 or more layers.

Since EFAB makes structures directly from computer design files, designers don't have to be microfabrication experts to use the process. According to Feinberg, all they need is a 3-D CAD version of their design and a basic understanding of the EFAB process, which can be picked up in a matter of days.

EFAB can create a structural layer in hours, Feinberg says, compared with days for a conventional MEMS process. "We know of one MEMS foundry that takes 12 weeks to deliver a three-layer MEMS device," he reports. By contrast, EFAB has built parts with dozens of layers in just a few days. So EFAB gets devices to market much faster than other microfabrication techniques, MEMGen claims.

EFAB also saves time when a product design changes. In conventional MEMS manufacturing, Feinberg points out, the production process must be altered when the product design changes. But the flexible EFAB process doesn't have to change to accommodate new design specifications.

MEMGen doesn't sell or license EFAB technology; instead, the firm uses EFAB to manufacture MEMS devices for customers. According to Feinberg, the process requires far less capital equipment than competitive systems, which make parts in cleanroom facilities filled with exotic machines. In contrast, EFAB manufacturing takes place in a single self-contained machine. As a result, Feinberg says, EFAB offers "substantial" cost and speed advantages over other microfabrication processes.

Copyright ©2002 Medical Device & Diagnostic Industry