Dynamic random access memory devices

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... 

Since the early suggestion that ferroelectric thin film materials could be the high dielectric layer in the capacitor of the ultra large scale integrated dynamic random access memory devices (ULSI DRAMS) made by Parker and Tasch, there has been a great deal of research effort to deposit multi-component ferroelectric oxide thin films as well as more recent industrial activity. The term ferroelectric indicates the property of certain materials that have remnant... 

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... 

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... 

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. 

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. 

This increase in circuit density is made possible only by decreasing the minimum feature size on the chip. Figure 2 illustrates the decrease in minimum feature size as a function of time for dynamic random access memory (DRAM) devices. In 1975, the 4-kilobit DRAM (4 X 10 memory cells or about 8.2 X 10 transistors) had features in the 7-9-(xm range, and by 1987,... 

In traditional electronics - LCR circuits, for example - the Ls and the Cs are invariably oxide materials. In the area of integrated semiconductor devices, gate dielectrics [18], dielectrics in dynamic random access memories [19], ferroelectrics in non-volatile memories [20], and decoupling capacitors [21] are all oxide materials. Oxides are also at the heart of many fuel cell [22] and secondary battery materials [23]. 

The alloy W-lOTi is used as a sputtering target in the manufacture of microelectronics devices, such as VLSI, ULSI (very large resp. ultralarge-scale integration), and DRAM (dynamic random access memory) chips. Thin W-Ti layers are sputtered onto silicon substrates and act as a diffusion barrier against aluminum (intercormect). 

The dynamic random access memory (DRAM) device, a two-element circuit, was invented by Dennard in 1967. The DRAM cell contains one MOSFET and one charge-storage capacitor. The MOSFET functions as a switch to charge or discharge the capacitor. Although a DRAM is volatile and consumes relatively high power, it is expected that DRAMs will continue to be the semiconductor memory of choice for nonportable electronic systems in the foreseeable future. ... 

Chemical and physical processing techniques for ferroelectric thin films have undergone explosive advancement in the past few years (see Ref. 1, for example). The use of PZT (PbZri- cTi c03) family ferroelectrics in the nonvolatile and dynamic random access memory applications present potentially large markets [2]. Other thin-film devices based on a wide variety of ferroelectrics have also been explored. These include multilayer thin-film capacitors [3], piezoelectric or electroacoustic transducer and piezoelectric actuators [4-6], piezoelectric ultrasonic micromotors [7], high-frequency surface acoustic devices [8,9], pyroelectric intrared (IR) detectors [10-12], ferroelectric/photoconduc-tive displays [13], electrooptic waveguide devices or optical modulators [14], and ferroelectric gate and metal/insulator/semiconductor transistor (MIST) devices [15,16]. 

In the case of dynamic random access memory (DRAM), the top electrode used in capacitor for a device s high speed raises the necessity of noble mefals like rufhenium (Ru), platinum (Pt), and iridium (Ir), which have low electric resistance and are mechanically and thermally stable. These noble metals are also chemically very stable and it is not easy to form capacitors by fhe efch back process. That is why noble metal CMP is compulsory. However, Ru is divided during the CMP process as a consequence of poor adhesion of leakage of cap oxide, grain growth of Ru, and cap oxide. To protect this phenomenon, the application of new functional slurry is essential. 

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