SOFT LITHOGRAPHY

Soft Lithography

This term covers a variety of approaches akin to traditional printing. A mold is created that can then is used to make an imprint in a material or apply ink to it, plus there are several other variations. A variant already used in creating optical components is nanoimprinting, which uses a hard mold to make an impression in a polymer. A recent variation on this uses a quartz mold, which is placed in contact with silicon. The silicon is then melted with a powerful laser, leaving an impression of the mold.

In general, no special technology is required for these techniques, nor are the fantastically clean environments required for existing silicon chip production, for example. Additionally, a wide variety of materials can be used.

Soft lithography is already used to make micro fluidic systems, such as those in labon- a-chip systems, and it scales readily down to the nanoscale—depending on the variant of the technology used, resolution can get below 10 nanometers. The attraction for nanoelectronics is clear—the technology is simple, offers a high level of parallelism (and thus economies of scale from high production runs), and can produce complex patterns with nanoscale features. As a replacement for traditional lithography for creating electronic devices, however, there is currently a major obstacle—the technique is not well suited to making the precisely aligned, multilayered structures currently used in microelectronics, although work is being done to overcome this limitation.

The alignment problem is lessened if larger feature sizes are acceptable and the approach has been investigated for making flexible displays. Additionally, the creation of the master is much cheaper than for photolithography and the process would become economical for much lower production runs, such as for device specific electronics.