An invention by Bengaluru-based scientists at IISc is all set to make inroads into the billion-dollar nanoelectronics industry.
This is disruptive because the technology can drastically reduce the cost of the existing state-of-the-art e-beam lithography and optical lithography. This invention is a new way to etch thin lines on a substrate using electrodes, termed electrolithography.
This will come in very useful in inscribing, for instance, nanometer-scale circuits which make up IC chips, minute transistors among others. Once developed into prototypes, this technique could in principle reduce the cost of the equipment used presently from about five crore rupees per piece to merely Rs.15-20 lakhs. This would come in useful not just in the industry but in academia, too, with more colleges being able to afford research in nanotechnology.
The people behind this are Dr Praveen Kumar of Department of Materials Engineering, Professor Rudra Pratap, Chairperson of Centre of Nanoscience and Engineering, and Santanu Talukder, their PhD student. Once this technology is developed into a prototype for commercial use, it can vie with, and, as the researchers claim, even surpass, the existing state-of-the-art technology and break into the billion-dollar, nanoelectronics industry.
Since it does not require high currents or vacuum atmosphere it is a relatively more environment-friendly method than existing ones. The group has filed for the patent in December 2014.
In the process of taking their invention from the lab to the industry, the scientists will have to recruit mechanical engineers and electrical engineers to help them develop the prototype.
Technically the main steps they have to take will be in putting the whole assemblage into a black box which can be easily operated using the proverbial “push-button.”
The usual challenges of getting people to adopt it may not be difficult, as IISc organises various workshops, attended by academicians as well as people from industry, where the product may be showcased. Not just that, the Centre for Nano-Science and Engineering, at IISc, has several industry affiliates who can understand the power of the invention and communicate its worth to others.
The process of lithography is straightforward. You take a transparent glass plate, coat it with a layer of a suitable polymer.
On top of this, add a layer of chromium, then you dig a trench of the desired pattern on the chromium layer so that parts of the polymer layer are exposed. Using acetone, dissolve the exposed polymer and remove those parts of it. This caused a gap to be formed in the polymer-chromium sandwich.
This whole assemblage functions like the negative of a developed photo film. Now, if the metal of choice is “sputtered” on to this sandwich, it will go and occupy the gap that’s been created and directly fall on the glass plate. In this way, the desired pattern using a metal of choice can be formed. This pattern will have a width equal to the width of the trench and thickness equal to the polymer layer.
The crucial difference between existing processes and this one is in the manner of digging the trench.
Here, the researchers use electrodes that are widely separated from each other. The very thin cathode, when it moves like a nib over the chromium layer, causes the metal to heat up, dissolve and flow out. This makes a trench whose width is nearly that of the electrode tip. Other techniques, the e-beam lithography which is very popular, or the optical lithography using ultraviolet light, involve machines that cost a few crores of rupees whereas this set up could be assembled at a cost price of some Rs20 lakhs.
Dr. Kumar says it was serendipitous!
“We were working on a method to enhance the sensing property of a piezo-resistive material. We had developed a method to create controlled damage in a metallic structure… [While doing this] we got interested in understanding this liquefaction of the chromium layer and the flow of the liquefied chromium away from the cathode. We performed a series of experiments to understand its fundamentals.
“Once we got the science behind the phenomenon we started working on the invention of electrolithography,” he says.
It can work well in making trenches that are microns thick as well as those that measure only nanometers in thickness.
