Random access memory, dynamic

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... 

FIGURE 4.1 Chemical reactions are used to achieve the fine structures seen in modern integrated circuits. This electron micrograph shows a transistor in a "cell" of a 1-mega-bit dynamic random access memory chip. The distance between features is about 1 pm. Courtesy, AT T Bell Laboratories. 

One of the more important applications of ion implantation is well engineering at relatively high ion energies. For the protection of dynamic random access memories from soft errors, different structures have been proposed and employed. The conventional procedure is to use epitaxial wafers well engineering beneath the active p- and n-channels provides a less expensive alternative. 

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... 

Fig. 4.15 The use of etch stops to visualize defects in a dynamic random access memory (DRAM) structure for subsequent electron microscopy inspection. If a bias is applied to the silicon substrate, as shown in (a), the polysili-...

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... 

In addition to requiring high dielectric films for DRAM capacitors (dynamic random access memories) and for the active memory elements in FRAMs, the microelectronics industry has a stated demand for a replacement for Si02 gate oxides very soon. The leading candidate is hafnia (Hf02), and there are significant opportunities for the ferroelectrics community to contribute to the solution of this problem. 

Hwang CS (1998) (Ba,Sr)Ti03 thin films for ultra large scale dynamic random access memory. A review on the process integration. Materials Science and Engineering B-Solid State Materials for Advanced Technology 56(2-3), 178-190... 

Mass production poses strict requirements on resist materials, most important of which are sensitivity, spatial resolution, contrast, and etch resistance. The sensitivity of the next-generation resists is required to be less than 10 pC/cm (EB), 100 mJ/cm (x-ray), and 25 mJ/cm (EUV) [89]. It should be noted that the resist sensitivity is traditionally expressed not by absorbed dose but exposure charge or energy per unit area. As for the spatial resolution, 45 nm is needed for the production of dynamic random access memory (DRAM) in 2010 [89]. Although resist patterns below 10 nm are presently fabricated by some kinds of resists, they do not have enough sensitivity required for the mass production [90,91]. 

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 1. A packaged 1-megabit dynamic-random-access-memory (DRAM) silicon chip on a processed 150-mm-diameter Si wafer. (Used by courtesy of G. B. Larrabee, Texas Instruments.)...

Note These specifications were developed at Balazs Analytical Laboratory. Abbreviations are defined as follows DRAM, dynamic random access memory VLSI, very-large-scale integration ULSI, ultralarge-scale integration TOC, total oxidizable carbon THM, trihalomethane SEM, scanning electron microscopy and EPI, epifluorescence... 

In the case of dynamic random access memories (DRAMs) the cell is a thin film capacitor. The state of the cell ( 0 or T ) is read by the current pulse following an addressing voltage pulse. Because the charge stored in the capacitor leaks away in time (z = RC) then, for the information to be retained it must be periodically refreshed, the rate of leakage determining the necessary refresh interval. 

Over the past three decades, enormous progress has been made in materials and materials processing used to fabricate electronic devices. This progress has made possible an astonishing increase in device complexity and decrease in the dimensions of features used to fabricate the circuit, which, in turn, has led to improved performance and reduced cost per function. Figure 1 illustrates these trends for dynamic random access memory (DRAM), historically the most complex chip produced in terms of feature size and components per chip. 

DRAM (dynamic random access memory) — A type of a commonly used random access memory that allows the stored data to be accessed in any order, i.e., at random, not just in sequence. That type of computer memory stores each bit of data in a separate capacitor charged and discharged by only one logic element transistor. However, the DRAM capacitors are not ideal and hence leak electrons the information eventually fades unless the capacitor charge is periodically refreshed (circa every 64 ms). This makes this type of memory more power... 

Dynamic Random Access Memory FeRAM = Ferroelectric Random Access Memory HCP = Hexagonal close packed HREM = High-resolution electron microscopy HTB = Hexagonal tungsten bronze MPTBh = Monophosphate tungsten bronzes with hexagonal tunnels MPTBp =... 

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