Home > Press > ASU scientists improve chip memory by stacking cells
Scientists at Arizona State University have developed an elegant method for significantly improving the memory capacity of electronic chips.
ASU scientists improve chip memory by stacking cells
Tempe, AZ | Posted on December 22nd, 2009
Led by Michael Kozicki, an ASU electrical engineering professor and director of the Center for Applied Nanoionics, the researchers have shown that they can build stackable memory based on "ionic memory technology," which could make them ideal candidates for storage cells in high-density memory. Best of all, the new method uses well-known electronics materials.
"This opens the door to inexpensive, high-density data storage by ‘stacking' memory layers on top one another inside a single chip," Kozicki said. "This could lead to hard drive data storage capacity on a chip, which enables portable systems that are smaller, more rugged and able to go longer between battery charges."
"This is a significant improvement on the technology we developed two years ago where we made a new type of memory that could replace Flash, using materials common to the semiconductor industry (copper-doped silicon dioxide). What we have done now is add some critical functionality to the memory cell merely by involving another common materia - silicon."
Kozicki outlined the new memory device in a technical presentation he made in November at the 2009 International Electron Devices and Materials Symposia in Taiwan. He worked with Sarath C. Puthen Thermadam, an ASU electrical engineering graduate student.
Kozicki said that given current technology, electronics researchers are fast reaching the physical limits of device memory. This fact has spurred research into new types of memory that can store more information into less and less physical space. One way of doing this is to stack memory cells.
The concept of stackable memory is akin to one's ability to store boxes in a small room. You can store more boxes (each representing a memory cell) if you stack them and take advantage of three dimensions of the room, rather than only putting each box on the floor.
Kozicki said stacking memory cells has not been achieved before because the cells could not be isolated. Each memory cell has a storage element and an access device; the latter allowing you to read, write or erase each storage cell individually.
"Before, if you joined several memory cells together you wouldn't be able to access one without accessing all of the others because they were all wired together," Kozicki said. "What we did was put in an access, or isolation device, that electrically splits all of them into individual cells."
Up until now, people built these access elements into the silicon substrate.
"But if you do that for one layer of memory and then you build another layer, where will you put the access device," Kozicki asked. "You already used up the silicon on the first layer and it's a single crystal, it is very difficult to have multiple layers of single crystal material."
The new approach does use silicon, but not single crystal silicon, which can be deposited in layers as part of the three-dimensional memory fabrication process. Kozicki said his team was wrestling with how to find a way to build an electrical element, called a diode, into the memory cell. The diode would isolate the cells.
Kozicki said this idea usually involves several additional layers and processing steps when making the circuit, but his team found an elegant way of achieving diode capability by substituting one known material for another, in this case replacing a layer of metal with doped silicon.
"We can actually use a number of different types of silicon that can be layered," he said. "We get away from using the substrate altogether for controlling the memory cells and put these access devices in the layers of memory above the silicon substrate."
"Rather than having one transistor in the substrate controlling each memory cell, we have a memory cell with a built-in diode (access device) and since it is built into the cell, it will allow us to put in as many layers as we can squeeze in there," Kozicki said. "We've shown that by replacing the bottom electrode with silicon it is feasible to go any number of layers above it.
With each layer applied, memory capacity significantly expands.
"Stackable memory is thought to be the only way of reaching the densities necessary for the type of solid state memory that can compete with hard drives on cost as well as information storage capacity," Kozicki said. "If you had eight layers of memory in a single chip, this would give you almost eight times the density without increasing the area."
Kozicki said the advance mimics an idea employed in early radios.
"We created a modern analog to the ‘cat's whisker,' where we are growing a nanowire, a copper nanowire, right onto the silicon to create a diode," he said.
Cat's whisker radios, a product of the 1930s, were simple devices that employed a small wire to scratch the surface of a semiconductor material. The connection between the semiconductor and the wire created a diode that they could use as part of a radio.
"It turns out to be a ridiculously simple idea, but it works," Kozicki said of his stackable memory advance. "It works better than the complicated ideas work."
"The key was the diodes, and making a diode that was simple and essentially integrated in with the memory cell. Once you do that, the rest is pretty straightforward."
About Arizona State University
Arizona State University is a creating a new model for American higher education, an unprecedented combination of academic excellence, entrepreneurial energy and broad access. This New American University is a single, unified institution comprising four differentiated campuses positively impacting the economic, social, cultural and environmental health of the communities it serves. Its research is inspired by real world application, blurring the boundaries that traditionally separate academic disciplines. ASU serves more than 64,000 students in metropolitan Phoenix, Arizona, the nation's fifth largest city. ASU champions intellectual and cultural diversity, and welcomes students from all fifty states and more than one hundred nations across the globe.
For more information, please click here
Copyright © Arizona State University
If you have a comment, please Contact
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
News and information
Graphene reduces wear of alumina ceramic March 26th, 2015
FEI Technology Award of the German Neuroscience Society Goes to Benjamin Judkewitz of the University of Berlin: Bi-annual award honors excellence in brain research during the German Neuroscience Society’s Annual Meeting, held 18-21 March 2015 March 26th, 2015
SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015
Hong Kong Investors Bullish on Dais Analytic Invest $5.75M, Provide $60M Contract, and Create New Joint Venture Company March 26th, 2015
Nanotechnology in Medical Devices Market is expected to reach $8.5 Billion by 2019 March 25th, 2015
Nanotechnology Enabled Drug Delivery to Influence Future Diagnosis and Treatments of Diseases March 21st, 2015
Nanocomposites Market Growth, Industry Outlook To 2020 by Grand View Research, Inc. March 21st, 2015
Nanotechnology Drug Delivery Market in the US 2012-2016 : Latest Report Available by Radiant Insights, Inc March 16th, 2015
Nano piano's lullaby could mean storage breakthrough March 16th, 2015
Nanotechnology Helps Increasing Rate of Digital Data Processing, Storage March 9th, 2015
Iranian Scientists Apply Nanotechnology to Produce Electrical Insulator March 7th, 2015
Magnetic vortices in nanodisks reveal information: Researchers from Dresden and Jülich use microwaves to read out information from smallest storage devices March 4th, 2015
SUNY POLY CNSE to Host First Ever Northeast Semi Supply Conference (NESCO) Conference Will Connect New and Emerging Innovators in the Northeastern US and Canada with Industry Leaders and Strategic Investors to Discuss Future Growth Opportunities in NYS March 25th, 2015
UW scientists build a nanolaser using a single atomic sheet March 24th, 2015
Iranian Researchers Present Model to Determine Dynamic Behavior of Nanostructures March 24th, 2015
Sharper nanoscopy: What happens when a quantum dot looks in a mirror? March 19th, 2015
Industrial Nanotech, Inc. Announces Next Large Order from the Oil and Gas Industry March 26th, 2015
Quantum compute this -- WSU mathematicians build code to take on toughest of cyber attacks: Revamped knapsack code offers online security for the future March 26th, 2015
Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015
Square ice filling for a graphene sandwich March 26th, 2015