EFAB ("Electrochemical FABrication") is a new micromachining process promising to rapidly and automatically batch fabricate high-aspect-ratio microstructures with arbitrary 3-D geometry using inexpensive equipment. Conventional microfabrication processes have so far produced fairly simple geometries (e.g., 1-5 structural layers), yet many MEMS could benefit if more sophisticated shapes could be manufactured. By using "Instant Masking" (IM)-a novel in-situ micropatterning method-to simplify, accelerate, and automate through-mask electroplating, EFAB can produce extremely complex shapes by depositing hundreds-thousands of layers at high speed. While other processes often do not allow integration with ICs, EFAB operates at less than 60 degrees C, making IC compatibility a possibility. Alternative processes require costly facilities and equipment; EFAB separates photolithography from device fabrication, requiring a cleanroom only for mask-making, then depositing all layers in a low-cost, self-contained machine. All Instant Masks required can be prepared simultaneously, without repeating the lithography on each layer. Selective electrodeposition requires simply mating the mask with the substrate and applying current; in this way we have patterned well-defined features as small as 20 x 20 mu m. The procedures in EFAB are selective electrodeposition, blanket electrodeposition, and planarization. To date we have built metal structures with up to 12 layers consisting of independently-moving components.
