A new semiconductor fabrication process developed by engineers at the University of Wisconsin (Madison, WI) is opening up a wide range of possibilities for flexible electronics

Historically, the semiconductor industry has relied on flat, two-dimensional chips upon which to grow and etch the thin films of material that become electronic circuits for computers and other electronic devices. But, a new semiconductor fabrication process developed by engineers at the University of Wisconsin (Madison, WI) will open up a wide range of possibilities for flexible electronics.

A team led by electrical and computer engineer Zhenqiang Ma and materials scientist Max Lagally have created a process to remove a single-crystal film of semiconductor from the substrate on which it is built. This thin layer, which is only a couple of hundred nanometers thick, can be transferred to glass, plastic or other flexible materials.

In addition, the semiconductor film can be flipped as it is transferred to its new substrate, making its other side available for more components. This doubles the possible number of devices that can be placed on the film. By repeating the process, layers of double-sided, thin-film semiconductors can be stacked together, creating powerful, low-power, three-dimensional electronic devices.

“It’s important to note that these are single-crystal films of strained silicon or silicon germanium,” says Ma. “Strain is introduced in the way we form the membrane. Introducing strain changes the arrangement of atoms in the crystal such that we can achieve much faster device speed while consuming less power.”

For noncomputer applications, flexible electronics are beginning to have significant impact. Solar cells, smart cards, radio frequency identification tags, medical devices and active-matrix flat panel displays could all benefit from the development. The techniques could allow flexible semiconductors to be embedded in fabric to create wearable electronics or computer monitors that roll up like a window shade.

“This is potentially a paradigm shift,” claims Lagally. “The ability to create fast, low-power, multilayer electronics has many exciting applications.”

According to Lagally, silicon germanium membranes are particularly interesting. “Germanium has a much higher adsorption for light than silicon,” he points out. “By including the germanium without destroying the quality of the material, we can achieve devices with two to three orders of magnitude more sensitivity.” Lagally says that increased sensitivity could be applied to create superior low-light cameras, or smaller cameras with greater resolution.