Applications in Semiconductor Technology

The number of transistors per chip is increasing continuously (for microprocessors, the total number of transistors per chip was 11, 21, and 40 million in the years 

Fundamentals of Electrochemical Deposition. Second Edition. By Milan Paunovic and Mordechay Schlesinger Copyright 2006 John Wiley Sons, Inc. 

The required degree of understanding of the physical properties of metal thin films used for interconnects on chips is illustrated by the following example. It was found that the performance of conductors on chips, A1 or Cu, depends on the structure of the conductor metal. For example, Vaidya and Sinha (10) reported that the measured median time to failure (MTF) of Al-0.5% Cu thin films is a function of three microstructural variables (attributes) median grain size, statistical variance (cr ) of the grain size distribution, and degree of [111] fiber texture in the film. 

The selective Cu deposition process was suggested by Ting and Paunovic (13) as an alternative means of fabricating multilevel Cu interconnections (Fig. 19.4). The first step in this through-mask deposition process (14) is the deposition of a Cu seed layer on a Si wafer, and then a resist mask is deposited and patterned to expose the underlying seed layers in vias and trenches. In the next step, Cu is deposited to fill the pattern. After the Cu deposition mask is removed, the surrounding seed layer is etched and dielectric is deposited. Electroless Cu deposition has been suggested for the blanket and selective deposition processes (15). 

There is a basic difference between the damascene and through-mask plating processes in the way the trenches and vias are filled with electrochemically deposited Cu, through either an eiectrodeposition or an electroless technique. In multilevel metal structures, vias provide a path for connecting two conductive regions separated 

The most active areas in the modern applications of electrochemical deposition are semiconductor technology and magnetic recording. 

One major recent advance in silicon-based semiconductor industry is the development of copper interconnects on chips. This new technology replaces the traditional aluminum or aluminum alloy (e.g. Al—Cu) conductors produced by physical vapor deposition (PVD) with copper conductors manufactured by electrodeposition. Copper has been replacing aluminum since 1999 owing to its low bulk electrical 

The number of transistors per chip is increasing continuously (for a microprocessor, the total number of transistors per chip was 11, 21, and 40 M (million) for years 1997, 1999, and 2001, respectively) and the physical feature size of transistors is decreasing consequently the dimensions of interconnections (interconnects) on the chip are scaling down for example, linewidths were 0.25, 0.18, 0.15, and 0.10 pm in the years 1997, 1999, 2001, and 2006, respectively. This scaling down of interconnects on chips requires interconnect metal of high quality and better understanding of physical properties of thin films [96]. 

The required degree of understanding of physical properties of thin metal films used for interconnects on chips is illustrated in 

In this section, we review the present manufacturing processes and discuss the challenges facing the extendability of these processes to the new generation of IC products. There are three primary fabrication processes (1) metal-reactive ion etching (RIE), (2) dielectric RIE, or damascene, and (3) through-mask deposition process. 

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In view of the many important applications in semiconductor technology, the interaction of hydrogen with silicon surfaces has been intensively studied. Recombinative H2 desorption from Si(100)-2 x 1 follows first-order kinetics89, unusual when compared with the second-order kinetics observed for H2 desorption from Si(lll)-7 x 7. The measured activation barriers for the desorption of H2 on Si(100) range from 45 to 66 kcalmol-189 90. 

Both AsHy and SbH3 oxidize readily to the trioxide and water, and similar reactions occur with S and Se. ASH3 and SbH3 form arsenides and antimonides when heated with metals and this reaction also finds application in semiconductor technology e.g. highly purified SbHy is used as a gaseous n-type dopant for Si (p. 332). 

Interest in Pbi, cSn,cTe solid solutions and related systems has been maintained, presumably because of their application in semiconductor technology. Three... 

Applications in Semiconductor Technology 1141 Barrier (Ta) Cu seed layer. 

The thermal conductivity is important for many applications in semiconductor technology, e.g., for thermoelectric devices. In Fig. 41 the thermal conductivity of boron carbide is plotted versus chemical composition (163-165). The strong decrease from B4.3C at the carbon-rich limit of the homogeneity range toward more boron-rich compositions can easily be explained by the change of the most homogeneous structure at 64,30 to the most distorted one at about B6.5C shown in Fig. 26. For temperature dependence, see Ref. 166. 

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