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Scientists improve chip memory by stackingcells(PhysOrg.com) -- Scientists at Arizona State University have developed an elegant method forsignificantly improving the memory capacity of electronic chips.Led by Michael Kozicki, an ASU electrical engineering professor and director of the Center for AppliedNanoionics, the researchers have shown that they can build stackable memory based on “ionic memorytechnology,” 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 oneanother 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 batterycharges.”“This is a significant improvement on the technology we developed two years ago where we made a newtype 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 memorycell merely by involving another common materia - silicon.” Kozicki outlined the new memory device in a technical presentation he made in November at the 2009International Electron Devices and Materials Symposia in Taiwan. He worked with Sarath C. PuthenThermadam, an ASU electrical engineering graduate student.Kozicki said that given current technology, electronics researchers are fast reaching the physical limits ofdevice memory. This fact has spurred research into new types of memory that can store more informationinto 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 storemore boxes (each representing a memory cell) if you stack them and take advantage of three dimensions ofthe 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 eraseeach storage cell individually.“Before, if you joined several memory cells together you wouldn’t be able to access one without accessingall of the others because they were all wired together,” Kozicki said. “What we did was put in an access, orisolation 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 accessdevice,” Kozicki asked. “You already used up the silicon on the first layer and it’s a single crystal, it is verydifficult 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 ofthe three-dimensional memory fabrication process. Kozicki said his team was wrestling with how to find away to build an electrical element, called a diode, into the memory cell. The diode would isolate the cells."Scientists improve chip memory by stacking cells." Phys.org. 21 Dec 2009. http://phys.org/news180643634.html Page 1/2