Going small and inexpensive

A technique derived from electronic chip production is being applied to making low cost parts with nanometre sized features – for either short- or long-run manufacturing. Applications include chips, micromechanical devices and exotic structures designed to be implanted in humans. Other applications include: photonics, data storage, displays, MEMS, NEMS, biochips, microfluidics, semiconductors and nano devices. The method, called Step and Flash Imprint Lithography, is being pioneered in the UK at the Manufacturing Engineering Centre at Cardiff University. It can be applied to the manufacture of large parts with fine features, or very small parts produced on a wafer. The first stage is to produce a quartz glass template. But while conventional micro- and nano-manufacture uses photographic methods to create features using a patterned mask, this technique depends on the actual shape pattern on the underside of the template, which has features cut into it by laser or ion beam lithography. The next stage is to deposit a monomer-based resist on a substrate, then lower the template onto the resist – the underside of which is coated with a release agent. Ultraviolet light polymerises the monomer to produce a polymer layer of varying thickness. The template is then removed, and a halogen etch breaks through the thin layers of polymer, which then allows an oxygen etch to etch through into the substrate beneath, which can be any one of a wide range of materials. This may be the finished product, if only a few items are required. On the other hand, it is possible to then deposit a thin layer of metal onto the patterned substrate, or use an organic polymer as substrate, and then electroform hard nickel to produce a tool to press, stamp, or otherwise form products. In the words of operations manager Robert Hoyle: “In principle, you should be able to knock parts out at relatively low cost”. The initial template is likely to cost around £2,000. Feature sizes in finished products can include 65nm contacts for nanoelectronics, 65nm sized pillars, 30nm wide lines, or more complex constructions. A typical application is in the production of fine-scale diffraction gratings for optical instruments, and several examples were being handed round by Dr Hoyle at the recent Medical Innovation Forum in London. Colin Maclean, principal project leader at TWI, commented that the features were small enough to encourage the directional growth of nerve cells in medical implants, and to pattern bone structures and produce nano scale textures that are increasingly becoming considered to be necessary to make human implants more biocompatible. Cardiff University Manufacturing Engineering Centre Pointers * It is possible to produce parts with feature sizes only a few tens of nanometres across * The technique is suitable for both short run and mass manufacturing