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Unformatted text preview: cility7 . For example, the lithograph equipment needed for an eight-inch fab8 is valued at 8-9 million dollars and lithograph equipment for a twelve-inch fab is valued at 20 million dollars. Because every new generation of DRAM needs new lithograph equipment, this cost is huge. Wafer size is an important factor that can enhance productivity in the same generation of product and the same process. Thousands of chips are designed from one wafer9 . After circuit is plated, a wafer is split into thousands of chips and packaged through the assembly process. Therefore wafer size can determine the productivity among the same product generation since a larger wafer can make more chips. More chips with the same process can reduce the cost of production. From this point of view, productivity is a very critical factor to overcome the rising cost of equipment and fabrication for a larger wafer and is one of the key factors for cost reduction. At this point, DRAM providers have competed to invest and build fabs which can be capable of producing chips with larger wafers. But, the cost of building a leading edge fab has increased as well as shown in table 3-2. "Chip makers gripe bitterly, but litho costs keep soaring", EETIMES, September 1999 fab means normally a factory in the semiconductor industry. 9 The number of chips is depending on product generation and wafer size. 27 7 8A Table 3-2 Rising cost of building a leading-edge fab, 1983 to 2003 Year 1983 -1990 1997 2001 2007 Wafer (inches in diameter) 4 6 8 12 12 Linewidth (microns) 1.200 0.800 0.250 0.130 0.065 Cost (US $ millions) $200 $400 $1,250 $3,000 $5,000 Source: Adapted from Hurtarte et al., Readapted from Clair Brown and Greg Linden, Chips and Change, 2009,table 2-1 As the costs of fab increase, DRAM providers have invested in new generation technology which shrinks the line width in the chip for profitability. But, the cost of new generation technology has also dramatically increased. The cost of $1.5 billion dollars for developing 65 nm increased to $2.4 billion dollars for 45nm'". As shown in figure 3-5, these kinds of R&D costs have continuously increased and reduced the revenues gaps. Annual growth rate of revenues will stay at 6.5% but annual growth rate of RD&E" will be 12.2% between 2004 and 2020 per the following by forecast of VLSI research'. 10 G. Dan Hutcheson , The R&D crisis, VLSI Research INC, 2005 " Research,~development and extension 12 G. Dan Hutcheson , The R&D crisis, VLSI Research INC, 2005, page4 28 Chip Making R&D Versus Revenues(Worldwide in $M) 1E +05 .... .................................................... 1E+06 Revenues - ----------------------------- ... .... - ..... -- " ...-----------.......---------------- -------.....--------..---..------..-- ..--.-----..- 1957 198 19- 2007 200 l 2020 2020 Figure 3-5 Chip Making R&D Versus Revenues (Source: G. Dan Hutcheson, The R&D crisis, VLSI Research INC, 2005, page 4) The increasing cost of fabrication is a critical issue as discussed but the DRAM providers don't have other options such as foundry services since design and process engineers should work together due to the DRAM process characteristics. In other words, manufacturing process is the competitive point among DRAM providers. It is a critical bottleneck for the industry profitability. 3-3-2 Limitation of technology As already discussed, the DRAM industry has grown by doubling the density with the same size of chip following Moore's law. The core technology for the new generation of DRAM is the photolithography. Photolithography equipment occupies a huge portion of total DRAM fabrication costs, i.e., 20% of total fixed cost. The reason why the price of lithography equipment is high is that it is very difficult to enhance its function. Optical lithography is currently used for photolithograph equipment. This technology is still evolving despite the fact that many experts expect that lithograph technology cannot follow Moore's law due to physical limitations. The micron light beam using wavelengths of 0.436micron has been used for 20 years and blue-light technology using wavelengths of 0.365-micron was applied to the lithograph equipment. Then the technology using wavelengths of 0.248micron appeared in 1990s. In 1999 lithograph equipment using 0.193-micron wavelength was shown and is still used for 35-nano meter fabrication process. But, experts insist that more enhancement technology is uncertain. Also, a partnership for technology development among semiconductor providers can be the debatable issue due to the issues of patent and technology roadmap. Physical limitation of the technology can be explained by S-curve of semiconductor technology shown in figure 3-6. Semiconductor Performance: Minimum Line Width over Time Year 1960 1965 1970 1985 1980 1975 1990 2000 1995 20 2- e -4-------....... ............. 4-- ------------------- ---------------------------------------- .......--- -...
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