This is Science: 3D Mass Electronic Lithography

Today you will not surprise anyone with electronic lithography; a very successful future in microelectronics is prophesied to it. Even RosNano plans to purchase Mapper electron beam lithography. And what about materials - what will become the basis of the photoresist of the future?

Ion beam lithography , in the generalized sense of the word, sooner or later has to replace traditional photolithography , as it has incomparable resolution and pattern accuracy due to the use of particles (ions or electrons) with a very short wavelength (less than 1 Angstrom or 0.1 nm). In addition, this is a method of directly creating patterns and patterns that does not require the development of expensive masks (the price of which can reach hundreds of thousands of dollars apiece), as is the case with photolithography.

For example, in the presented scheme of the photolithographic process, in the case of ion-beam lithography, we can safely exclude the mask at stage number 3:



However, in the capitalist world everything is decided by money, including the cost of equipment and raw materials - of course, photoresist, which is consumed in large volumes , since the most common chip can contain from a dozen of the most diverse layers. And in fact, it is the photoresist that is responsible for how accurately the pattern will be reproduced on the substrate.

So, a group of Chinese scientists from Canada have proposed a way to use extremely cheap polystyrene as a photoresist in electron beam lithography, allowing you to create 3D objects up to 1.5 microns high with an unusually small thickness (below a hundred nanometers).

Polydimethylsiloxane polymer ( PDMS ) is usually used in electronic lithography , but scientists have found a way to replace it with cheaper polystyrene (the market value is about 2 times lower). This increases the sensitivity, and with it the performance of the whole method as a whole, since it takes less time to create one “pixel”.

The essence of the proposed method is that polystyrene is applied to the substrate due to thermal evaporation, and then after exposure to the electron beam, the exposed area can be easily dissolved with a mixture of xylenes. As a result, a cavity forms, which can subsequently be filled with various materials: aluminum (to create contacts), silicon dioxide (to create waveguides or insulating planes) and so on.


Examples of patterns obtained on polystyrene using electron beam lithography

In addition, if you wish, you can simultaneously “draw” on curved surfaces and even create waveguides on such surfaces:


Using an electron beam, you can print on virtually any surface, creating complex patterns

Thus, the combination of properties: low cost, low dose or short exposure time, combined with the ability to create patterns on curved surfaces, actually make polystyrene in demand in the emerging market of electronic industrial lithography.

Original article in ACSNano (DOI: 10.1021 / nn4064659)

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