Macetch: Chemical Etching Method Helps Fins Transistors Stand Tall


Nowadays, nanotechnology taking place in various sectors. Various scientists are concentrating on developing different types of devices at the nanoscale. Smaller and faster devices have become as a trend for electronic devices. But flat transistors have gotten about as small as physically possible. For researchers pushing for even faster speeds and higher performance, the only way to go is up. A novel method has been demonstrated to etch fin transistors. This technique known as MacEtch etches very tall, narrow finFETs. FinFETs a type of transistor that forms a tall semiconductor “fin” for current to pass through. This novel demonstration is done by scientists from the University of Illinois.

This novel technique addresses lots of problems while creating 3D devices. The technique is also called as metal-assisted chemical etching. It depends upon liquid, having low cost and simplest procedures as compared to ion beams. A metallic pattern is then applied to the surface. Then fins were dipped into a chemical solution, that etches away the areas around the template. Through this, fin gets vertical and smooth sides.

Xiuling Li, a U. of I. professor of electrical and computer engineering and the leader of the study, said “We are analysing instructions of electronic device against silicon. Through this technology, we are forwarding the vertical space limit, so we can put more transistors on a chip and get faster speeds. We are making the structures very tall and smooth, with aspect ratios. This is almost impossible for other existing methods to reach, and using a material with better performance than silicon.”

Macetch: Chemical Etching Method Helps Fins Transistors Stand Tall
A cross-sectional microscope image of a fin transistor. The indium phosphate semiconductor fin is overlaid with insulators and metals to make a working transistor. Credit: Yi Song

Generally, FinFETS developed by attacking semiconductor wafer with high energy ions beams. But, such techniques needs to overcome various challenges. The challenges are for shapes, performance. Instead of straightening up or down, the sides of fins angled to make like mountain ranges than fins. This type of shape means fin’s top performs more accurately. Another biggest problem was to analysing how ion beams damages semiconductor surface. This is for high-performance applications, which may cause current leakages.

Yi Song, the Graduate student, said, “This MacEtch technique gives a much higher aspect ratio, and the sidewalls are nearly 90 degrees. Thus, we can use the whole volume as the conducting channel. One very tall fin channel can get the same conduction as particular short fin channels, so we save a lot of area by improving the aspect ratio.”

For constant high performance, the interface between semiconductor and insulator must be smooth and even.

Li said, “Compound semiconductors are the future against silicon, but silicon is still the industry standard. So it is important to make it compatible with silicon and existing manufacturing processes.”

Researchers think that this MacEtch technique has various applications that use 3D semiconductor structures. They are like computing memory, batteries, solar cells and LED’s.

More information: Yi Song et al, Ultra-high Aspect Ratio InP Junctionless FinFETs by a Novel Wet Etching Method, IEEE Electron Device Letters (2016). DOI: 10.1109/LED.2016.2577046

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