Researchers build microchips using self-assembling polymers

Researchers in the US have developed a way of building complex microchips using self-assembling polymers that could lead to more densely arranged components.

The team from Massachusetts Institute of Technology (MIT) has created a way to guide self-assembling molecules to produce wires with right angles or curves as opposed to the hexagonal shapes they create naturally.

The researchers used a template array of tiny posts on the surface of the substrate to guide the pattern of the polymer molecules, which arrange themselves in specific ways owing to the forces acting between them.

Karl Berggren, associate professor of electrical engineering at MIT and co-author of a paper on the research, said the template was coated with a substance that repels one of the polymer components, creating strain on the molecular pattern.

‘The polymer then twists and turns to try to avoid this strain and in so doing rearranges on the surface,’ he said in a statement. ‘So we can defeat the polymer’s natural inclinations and make it create much more interesting patterns.’

Self-assembling polymers tend to naturally form hexagons to create a honeycomb pattern, said Caroline Ross, Toyota professor of materials science and engineering and another co-author. ‘But that’s not what circuit designers want. They want patterns with 90° angles.’

The new technique allowed the researchers to create not just perfect squares and rectangles but also a variety of other shapes including cylinders, spheres, ellipsoids and double cylinders. ‘You can generate this astounding array of features with a very simple template,’ said Ross.

The system can also produce features such as arrays of holes that are much closer together than those created with conventional chip-making methods, meaning it could produce microchips with more densely arranged components.

Because the technique can produce multiple, complex shapes or patterns simultaneously and in fewer steps than conventional methods, it could also reduce the time needed to manufacture these chips.

Although it would still take several days (as opposed to several months using electron-beam lithography) to create a large area of complex circuitry, the researchers argue this could be used as a master pattern to stamp a coating on other chips in a more rapid fabrication process.

Craig Hawker, a professor of chemistry and biochemistry at the University of California at Santa Barbara who was not involved in this work, said in a statement: ‘There is a growing need and requirement for industry to find an alternative to traditional photolithography for the fabrication of cutting-edge microelectronic devices.

‘This work represents a pivotal achievement in this area and clearly demonstrates that structures once considered impossible to achieve by a self-assembly strategy can now be prepared with a high degree of fidelity.’

The research is due to be published in the journal Advanced Materials in August and is available online now.