Memory-device, random-access

Today, dynamic random-access memories (DRAMs) are transistor/capacitor-based semiconductor devices, with access times measured in nanoseconds and very low costs. Core memories were made of magnetic rings not less than a millimetre in diameter, so that a megabyte of memory would have occupied square metres, while a corresponding DRAM would occupy a few square millimetres. Another version of a DRAM is the read-only memory (ROM), essential for the operation of any computer, and unalterable from the day it is manufactured. We see that developments in magnetic memories involved dramatic reductions in cost and... 

Dynamic random access memory (DRAM) silicon-based semiconductors and, 22 229, 230, 231, 250, 257, 258 vitreous silica in, 22 443 Dynamic random access memory devices, 10 3... 

Capacitors are charge storage devices that are essential in many circuit families, including dynamic random access memory, DRAM, and RF chips. For example, in RF chips, capacitors occupy a large fraction (at present about 50 %) of the area of the... 

Figure 1. Minimum feature size on a MOS random access memory device as a function of the year the devices were first commercially available.

Magnetic random-access memory (MRAM) is a new type of computer memory. MRAMs retain their state of magnetization even with the power off, but unlike present forms of nonvolatile memory, they have switching and rewritability rates that challenge (are faster than) those of conventional RAM. In today s read heads as well as those of MRAMs, key features are made of ferromagnetic metallic alloys. Such metal-based devices make up the first—and most mature—of the various categories of spintronics. 

The nanotechnology report issued in February 2004 by the UK Royal Society makes the general observation that Electrical transport properties across interfaces remain poorly understood in terms of science/predictive capability. This affects all nanomaterials . This observation most keenly summarizes the present state of play for Gbit level random access memories (RAMs), and it is our view that the electrode interface issues may dominate the device physics. Within the nanotech roadmap , high-dielectric ( high-K ) materials are strongly emphasized, as are nanotubes and new interconnects. 

Catenane 404+ was also incorporated into a solid-state device that could be used for random access memory (RAM) storage.42 In addition, this compound could be employed for the construction of electrochromic systems, because its various redox states are characterized by different colors.41,43... 

Figure 2. Minimum feature size on MOS random access memory devices as a function of year of commercial availability. (Reproduced with premission...

As an example of Si technology, Figure 1 illustrates a packaged 1-megabit dynamic-random-access-memory (DRAM) chip on a 150-mm-diameter Si substrate containing fabricated chips. Each of the chips will be cut from the wafer, tested, and packaged like the chip shown on top of the wafer. The chip is based on a l- xm minimum feature size and contains 2,178,784 active devices. It can store 1,048,516 bits of information, which corresponds to approximately 100 typewritten pages. 

Figure 5. Characteristic chip length scales illustrated by comparison to a ladybug. The magnification increases for each picture in the clockwise direction starting with the upper left corner, which shows a ladybug on 62-kilobit random-access-memory chips on a 75-mm-diameter silicon wafer. The final magnification in the lower left corner shows the metal lines (2 fim) at the device level. (Reproduced with permission from reference 3.

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