Enhancing silicon’s strength

Materials World magazine
15 Jun 2020

Tiny silicon structures can be made stronger and more deformable than previously thought possible, with potential for making smaller and more robust sensors in smartphones. Researchers from ETH in Zurich, Switzerland, switched production methods from ion beam to lithography to reduce damage and defects.

Ion beams of charged particles can mill desired shapes in a silicon wafer but leave traces in the form of defects that make the material prone to breaking. When tested, the pillars milled with an ion beam collapsed at a width of less than half a micrometre.

By using lithography, the pillars produced only suffered brittle fractures at widths above four micrometres, while thinner pillars were able to withstand the strain much better.

‘These lithographic silicon pillars can deform at sizes ten times greater than what we’ve seen in ion beam-​machined silicon with the same crystal orientation, with double the strength’ says Jeff Wheeler, Senior Scientist at the Laboratory for Nanometallurgy at ETH.

Wheeler and his team claim that the results could have an immediate impact on the fabrication of silicon microelectromechanical systems. He adds, ‘In this way, the gyroscopes used in smartphones, which detect rotations of the device, could be made even smaller and more robust.’