 |
Jan. 15, 2003 — MEMS are used in an increasing number of areas in the semiconductor-making process. Right now, the market is small, but it should grow as semiconductor feature sizes shrink and MEMS-based devices prove themselves in chip-making equipment.
Two of the major uses for MEMS in making semiconductors are optics and gas control. Historically, semiconductor makers have relied on finer and finer control in order to achieve the feature sizes they need for new generations of products. Also historically, chip makers have changed technologies to get the results they need. MEMS simply represent the next logical step. Specifically, makers of chip-making equipment are turning to MEMS to help them control the light that fixes the patterns on the chips and the gases needed to turn those patterns into functioning semiconductors.
Gas control is critical because most reactants are applied to the silicon wafer as gas and the amount and flow of gas into the processing chamber have to be very carefully controlled to get the proper depth and evenness of coating. Gases are controlled from a gas panel, which usually feeds several different gases into the same tool. Normally a gas panel is several cubic feet of stainless steel tubing, pressure and flow sensors and valves.
 |
“(MEMS gas panels) are typically about less than one-quarter of the size and maybe 20 percent of the weight of a conventional gas panel,” said James Harris, chief executive of Redwood Microsystems Inc. of Menlo Park, Calif., which makes MEMS-based gas systems.
Size matters because in a modern semiconductor production line, floor space is precious. “A square foot of fab costs at least $100,000” to equip and set up properly, Harris said. “If a piece of equipment can shrink even a square foot, it’s a measurable savings.”
MEMS gas panels can also improve process accuracy. “Smaller size also enables the customer to move the gas panel from a big, clunky box 5 to 10 feet from the tool to build right on top of the chamber,” Harris said. That puts the valves much closer to the work and reduces a source of inaccuracy. “You get process enhancement because you’ve cut out all that dead volume.”
Redwood isn’t the only company building MEMS products for gas control, although most of the others are concentrating on individual parts such as sensors and valves rather than complete panels. For example, SenSym Inc. of Milpitas, Calif., and the Veriflo division of Parker-Hannifin Corp. of Richmond, Calif., are making a MEMS-based pressure transducer for ultrahigh purity gases that has applications in chip making.
Another major area for MEMS and related technologies is in optical systems. Semiconductors are built layer by layer by photolithography. Smaller feature sizes require shorter wavelengths of light and much better control so the light energy is evenly diffused across the exposed surface.
“As steppers get smaller and smaller, the feature sizes of optics become more challenging,” said Rod Clark, president and founder of MEMS Optical Inc., a Huntsville, Ala., maker of MEMS-based optical components. “(The equipment manufacturers) want the beam to spread out at bigger angles,” Clark said, adding that the shorter wavelength and bigger bending angles are the key advantages of his company’s diffuser, which spreads the light evenly across the area being exposed. “It becomes a pretty critical part to make these devices work properly.”
MEMS Optical makes its diffusers by etching a field of precise three-dimensional prisms into silicon and using that to make a field of high-accuracy lenses.
For semiconductor optics, Clark sees an analogy with semiconductors themselves. “When they started out in electronics, everything was discrete (components). Then they went to integrated circuits. Optics today is kind of like discrete components. But now we can integrate whole optical systems onto wafers.”
It’s apparent MEMS are moving into semiconductor manufacturing, but what is less apparent is how much and how fast. The chip business such a new market for MEMS that it is under the radar screens of analysts, and equipment makers themselves are notoriously secretive about what goes into their products. Also, MEMS components are hard to track because they are usually hidden in subsystems within the equipment. MEMS Optical’s products, for example, are bought by the makers of excimer laser light sources, which sell their products to the equipment makers.
There is also the simple fact that most MEMS products for the semiconductor industry are new. Redwood’s Harris, for example, said his company’s gas systems are being tested by several of the major chip equipment makers, but so far he has no confirmed customers.
Still, Harris and the other executives aiming MEMS at the chip-making market are confident. Harris freely admits that MEMS isn’t a major player in gas controls today, but he adds, “In three years it will be.”