Micro and nanolevel patterning of substrates

Materials World magazine
,
1 Jan 2008

A team exploring more cost effective 3D, non-planar, micro- and nanolevel patterning of substrates at Newcastle University, UK, has received £90,000 worth of additional funding from NorthStar Equity Investors, also based in Newcastle.

EnFACE technology uses electrochemical dissolution to transfer patterns in a single step, without the need for a master mask.

The pattern resist is defined on a counter electrode (electrochemical tool) rather than the substrate, which has to be a conducting material. Placed in an electrochemical reactor, optimised for the geometry of the substrate, the tool and the substrate face each other, with electrolyte flowing between them. As a current is applied, the substrate (anode) is selectively etched, replicating the pattern on the tool (cathode). Features as small as three micrometres can currently be fabricated.

Professor Sudipta Roy, who heads the EnFACE project, believes the technology could have a particularly big impact on SMEs that want to produce microdevices but do not have a large initial capital investment.

Photolithography, which is traditionally used to transfer micro-patterns by applying electromagnetic radiation, can be expensive and labour-intensive. The resist on the substrate is exposed to UV light through a master mask, containing the pattern to be transferred, for through-mask plating and etching. ‘There are a lot of areas where you need rapid prototyping,’ explains Roy. But, she says, the rigid mask process is not conducive to flexible substrates and quick testing, due to the need for a stable mask for each substrate and product design.

She adds, ‘With our technique, you can have a tool made to produce 50 substrates. And you can use it in a normal laboratory or on a factory floor. You don’t have the huge process of development for the mask, and you no longer need clean room technology. The cost is reduced by a quarter.’

The team has tested the technology on a range of substrates, including copper, titanium and nickel-chromium. It plans to increase the breadth of materials explored, as well as gain a better understanding of the electrochemical phenomena, using the recent grant.

Areas of application include improving cell and tissue adhesion to medical implants via precise surface structuring, rather than ‘randomised roughening’ by sand or grit blasting, as well as in portable energy cells and air bags.

However, to compete with lithographic tools and achieve high precision and resolution micro- and nanoscale patterning, Roy suggests that a hybrid of this technnique with other maskless methods (micro-machining with nanosecond voltage pulsing), and tools such as focused ion beam microscopy, would be necessary.

Colin Seabrook, a consultant in materials science and technology with a specialism in surface science, says, ‘This is an interesting early technological idea obviously in need of proof-of-concept funding to move it on. There are claims about “lower capital costs”, but, at this stage, these are of little consequence in the business world. The real driver is better technological achievement (such as quality and compactness) at a significantly lower price. It remains a candidate in the maskless technology race.’

 

Further information:

Centre of Excellence for Nanotechnology, Micro and Photonic Systems