Dr. Simon Elliott from the Tyndall National Institute in Ireland is coordinating the EU research project REALISE and working on the next generation of USB flash memories. Rare earth oxides have been introduced to improve their storage capacity
How is it possible to improve memory chips?
Improvements in memory chips are now only possible by bringing in new materials that can be laid down with the high quality needed. And the advances that we have made in the REALISE project are going to allow more data capacity in flash memories and faster transistor operation.
Which are these new materials?
The new materials are rare earth oxides: a fine powder that functions as an electronic insulator. It will isolate the electrical information on computer chips. The material itself is not costly and also the amounts used for nano thin layers are tiny. Of all the elements in the periodic table the rare earth elements were discovered relatively late. They were in the same mineral deposit and so they were all classified together. We now know that they are not all that rare and that they are useful elements for a variety of purposes. Like other metals they form oxides. The rare earth oxides are safe and inert and they have useful electrical characteristics. For those reasons they were aimed to be used in this project because they behave as very good insulators
How are these materials integrated into the memory chips?
The crucial element of the REALISE project is how to bring these oxides down onto the chips and integrate them into the structures that are needed. The process used is called ALD, atomic layer deposition. As the name implies, the scientists try to lay down the layers atom by atom at a very fine scale. The chemical process has been developed since the 1970ies and has now been used in the electronics industry to make transistor chips. Another advantage: ALD can coat complicated three-dimensional structures at the nano scale. Using the REALISE materials in 3D structures for capacitors means that each capacitor uses less surface area on the wafer, leading to an associated saving of 70 percent in cost. The project partners are sure that the huge benefits these new materials will bring for the electronics industry will more than outweigh the costs. Therefore, the aim is to produce a highly-insulating dielectric material, with a so called high k-value, which enables a large capacitance in memory chips
Which is the role of nanotechnology in this project?
The electronics industry is probably the main example where we use nano technology every day in our daily lives. All electronic components are now down on the nano meter scale. And the new films that are needed for memory chips now must be as thin as two or three nano meters. It is very hard to manufacture films that are this thin with the high quality and the high uniformity that’s needed. So that is what the REALISE project was aiming to achieve, to lay down these with that nano meter scale quality.
Have you already performed some tests?
Our institute was responsible for simulation of the deposition process and for testing rare earth oxide material properties. To measure the capacitance that is gained with the new process, probe tips contact one of the chips on the processed wafer to apply a voltage across the rare earth films on it. The electrical tests determined that the new material performs in terms of its insulating properties three times better than alumina, the previous best material. Devices could therefore be made that are three times smaller than the current record, with the bonus of double the working lifetime. The REALISE project has developed a technology that is now ready for industry application. It is the basis for manufacturing a one terabyte USB stick in the near future.
Which are the prospects of your project’s achievements?
The trend is moving towards 3D and this process can be used in 3D. What that will deliver is lower cost and higher performance on a given surface area and that’s what’s needed for the future of the electronic’ industry and to continue following Moore’s law.
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