IBM developed Copper interconnect technology increases computer performance Put
ID: 1644129 • Letter: I
Question
IBM developed Copper interconnect technology increases computer performance Put simply, copper is a more efficient conductor than aluminum, making it useful in processors because it allows for smaller, thinner interconnects. Interconnects are tiny pieces of wire that connect transistors inside a pro- cessor. Smaller interconnects make for smaller, higher-performance chips because chip makers can pack more transistors into a smaller space. Cop- per's properties also make it more power-efficient than aluminum. Copper increases microprocessor performance substantially compared with chips that use traditional aluminum wire. A single POWER3-II chip-about the size of a thumbnail-contains a quarter mile of copper wiring. Copper Is the Answer After nearly 15 years of research, IBM scientists announced in September 1997 a new advance in semiconductor process that entails re- placing aluminum with copper. Copper has less "resistance" than alu- minum, and therefore transmits electrical signals faster. However, it doesn't mix as well with silicon, the base material of semiconductor chips. The IBM researchers found a way to put a microscopic barrier between the copper of steps needed to complete a chip. r and silicon in a way that actually reduced the number With this development, IBM is able to produce extremely intricate circuit designs with copper at widths of 0.20 microns-down from the current industry standard of 0.25 microns-a reduction far more difficult for aluminum. (A micron is over 100 times thinner than a human hair.) The copper-stimulated reduction in dimensions will permit designers to pack 150 million to 200 million transistors on a single chip. Copper will become more widespread in the semiconductor industry for several compelling reasons. Copper wires conduct electricity with about 40 percent less resistance than aluminum. That translates into a speedup of as much as 15 percent in microprocessors that contain copper wires. Copper wires are also far less vulnerable than those made of aluminum to electromigration, the movement of individual atoms through a wire, caused by high electric currents, which creates voids and ultimately breaks the wires. As a remarkable added benefit, IBM's method of depositing copper wires on chips means a potential cost saving of up to 30 percent for the wiring or 10 to 15 percent for the full wafer Despite its many virtues, copper didn't become a success overnight. For, while the semiconductor industry recognized its potential more than 30 years ago, the perceived danger of using copper acted as a brake on its development as an interconnect. Not only does copper rapidly diffuse into silicon, the substrate in which the transistors are formed, but it changes the electrical properties of silicon in such a way as to prevent the transistors from functioning. "Copper was considered to be a killer to semiconductor devices," says IBM Fellow Lubomyr Romankiw. "The conventional wisdom was to stay as far away from copper as you could. IBM's copper program managed to solve all the problems that faced the use of the element. One by one, scientists and engineers overcame the hurdles standing in the way of a viable technology. These ranged from a means of depositing copper on silicon to the development of an ultrathin barrier to isolate copper wires from silicon. Since introducing copper technology into volume production, IBM has incorporated copper into stand-alone processors in S/390 and RS/6000 systems, Apple Computer's iBook and PowerBook, as well as a variety of custom chips for leading networking products. IBM has said a copper-based PowerPC chip will also power a forthcoming game console from Nintendo. Major portions excerpted from Internet article, "Copper supercharges IBM supercomputers," by John G. Spooner, ZDNet News, Wednesday February 09, 2000 and IBM web site.Explanation / Answer
the resistivity of copper = 1.68x10-8 ohm m= 1.68x10-2 ohm m
the resistivity of aluminium= 2.65 x10-8 ohm m =2.65 x10-2 ohm m
1)Copper resistance = *(l/A) = 1.68x10-2 *[100/(0.2*1)]
=8.4 micro ohms
=8.4 x10-6 ohms
2) Al resistance = *(l/A) = 2.65 x10-2 *[100/(0.2*1)]
=13.25 micro ohms
=13.25 x10-6 ohms
3) Ratio = Copper /Al = (8.4 x10-6 ohms)/(13.25 x10-6 ohms) = 0.6339
4) power dissipation
= I*R2
= 1 x10-3 A* (8.4 x10-6 ohms)2
=7.056 x10-14 W
5) power ratio = IRcu2/IRal2
=Rcu2/Ral2
= (8.4 x10-6/13.25 x10-6)2
=0.4019