Are nanoparticles threatening Moore’s Law? In 1965, Gordon Moore of Woodlands, California, laid down Moore’s Law. He is the un‐
disputable prophet of the 21st Century. Moore did not make a new discovery like the old 19th and 20th century physicists, Fara‐
day and Watt. He did not create a new contraption like the inventors Edison and Tesla. He did not discover new atomic particles or develop an atomic bomb like Fermi and Op‐
penheimer. He pronounced something that at the time looked just like a hit and miss opinion. But it turned out not only to be accurate, but to predict the most fantastic leap in human history. "The future of integrated electronics is the future of electronics itself," Gordon Moore wrote in 1965. "The advantages of integration will bring about a proliferation of elec‐
tronics, pushing this science into many new areas. Integrated circuits will lead to such wonders as home computers..." Moore’s Law = progress in IT The gist of Moore’s Law is that we can have more and more of everything that we con‐
sider modern in today’s society. Specifically Moore’s Law states that the numbers of transistors on a single chip will double every 18 to 24 months without increase in cost. This law underpins all of IT‐developments. Without the “smaller, faster and cheaper” that this law predicts, there would have been no PC:s, no mobile phones, no Internet and virtually no progress in today’s industry. Development has taken us to circuitry on the dies which are the basis of microproces‐
sors with transistor gates that measure 70 nano in length and gate oxides as thin as 1.5 nano. The 130 nano channel length process technology that has just been introduced means that the wires in the circuitry are so thin that it takes 1000 wires placed side by side to equal the width of a human hair. In money terms, this development entails that the cost per transistor has fallen dramati‐
cally just as Moore predicted. In 1954, a transistor cost, on average, $5.52. By now, its price tag is not much more than a billionth of a dollar. That’s why we get value for the money in IT. The future is always unthinkable When Gordon Moore first made his prediction in 1965 he was talking about ten years to come. Now the Law has reached the age of 35 years. In a recent lecture Gordon Moore predicted that Moore’s Law may very well hold its own in the next two decades, but that the nature of matter will put an end to it about twenty years from now. The size of one atomic layer, for instance, is around 0.25 nano. You cannot get beyond that level of re‐
finement, or can you? 2
It’s a fascinating question! Just like history did not end at the Berlin Wall, technological progress will not end at Moore’s Wall. There will be all but insurmountable difficulties because of the actual size of atomic particles. But isn’t there a world also below this level ‐ inside the atom– among neutrinos, muons, mesons, quarks and other such quantum particles ‐ or anti‐matter and sub‐atomic black holes for that matter? Wouldn’t human technology master also this world in due course! Or, what do you think!? But who cares what we think. The future is always unthinkable and future technology is unimaginable. In a recent interview, Gordon Moore has expressed this very eloquently: “I ought to calibrate myself as a seer on this first of all. If you'd have asked me in 1980, I would have missed the importance of the PC. If you'd asked me in 1990, I would have missed the Internet. So now you are asking me in 2000, I don't know what I'm going to miss (laughs). It's clear that communications is a very rapidly expanding area.” (Ingenu‐
ity, May 2000) Of course, everyone today sees a great future in communications. And there certainly will be. But there are of course greater surprises around the corner than what can be seen by everybody already today. One of the surprises will perhaps be discovered once we break through Moore’s Wall. Perhaps there is a truth to the adolescent fantasy that each atom is a planetary system, a world of its own. The brightest scientists are working on this fantastic challenge But that is taking us too far. Long before we reach the Wall, there are more imminent challenges to the progress charted by the Law. Long before we reach these nanogalactic levels we must fight other rather more mundane threats against advances in miniaturi‐
zation and consequently to all industrial development. Constant innovation in architecture, lithography, materials and the achievement of abso‐
lute purity is already now needed to uphold Moore’s Law. Tens of thousands of disciples are working fervently around the world to keep the prom‐
ise of 20 years. The brightest scientists are obviously attracted by this fantastic chal‐
lenge. The battle is on a field from today’s few hundred nanos (0.18 and 0.13 micron ar‐
chitecture is 180 and 139 nanos, respectively) down to single nanos. Remember that the size of one atomic layer is around 0.25 nano. Sometimes it's a down hill battle, but it’s mostly up‐hill like most scientific battles. At times the battle flows like a river along a warm and gentle slope. On such days a dream will arise like a mist on the river. A dream where the battle is taken to the sub‐nano level. “Hello quarks and mesons of my dream, one‐day Moore’s Law will be pushed be‐
yond Moore’s Wall! See you then!” One millimeter is one thousand of a meter. Our fathers thought that was small, very small. One micron is one millionth of a meter. One nano is a billionth of a meter, i.e. one thousandth of a micron and a millionth of a millimeter. One millimeter consists of one million nanos. So, nano, that’s real small. Four layers of atoms is one nano, regardless of what an atom actually is ‐ the smallest unit in matter or an entire world of its own. 3
Lithography, architecture, new materials and clean processing are probably the most important battlefronts where legions of scientists are battling to avert the obvious threats to Moore’s Law. In all these areas progress is a sine qua non to guarantee per‐
formance of future microchips. Smarter architecture is the king‐pin of development, but new materials for dies, cir‐
cuitry and components will be necessary. And since no chain is stronger than its weakest link, interconnect development is just as important. A basic development is finding new methods for lithography. Lines are now so thin that when the architecture is projected on the die, normal light is much too thick to be able to draw those thin lines. One has to use thinner beams ‐ lower bandwidth beams – for the projections. At present the most promising move seems to be from present deep ultra violet light which surpassed the normal ultra violet light some time ago to extreme UV‐ light (EUV) abetted by specific mirrors that reduce bandwidth. With EUV it has been demonstrated possible to print a minimum feature size of 50 nano with expectations of 30 nano. Intel expects that EUV beta tools will be available by 2003 and manufacturing tools by 2005 and becoming the dominant high volume production technology before the end of the decade. Some of the improvements for EUV presently talked about are replacing laser‐produced plasma with z‐pinch, capillary discharge or plasma discharge. Who knows what the next step will be but once the Wall is reached the drawings will certainly have to be projected by e‐beam lithography featuring the use of single elec‐
trons. Absolute purity – is there such a thing? Another major threat to the new nanoarchitecture chips is presented by nanoparticles in the clean‐room. Both in air and water, there are particles that can be inferred but not correctly measured. These are less than one micron (1000 nano) in diameter and there‐
fore called nanoparticles. Another absolutely necessary development therefore involves instruments that are capable to trace and detect all nanoparticles and thus to monitor the quality of future generations of chips and ensure sufficient yield rates also on the lowest nanoarchitecture levels. Yield and reliability of all nanodevices are determined primarily by the ability to avoid incorporation of deleterious impurities such as organic contaminants, alkali ions and metal atoms/ions into the device during fabrication processes. Competitiveness and market share in nanodevices will therefore depend on new cleaning methodology to remove nanoparticles. Technologies are being developed in order to remove also these minute particles effi‐
ciently and totally. In air purification, the basic method is to charge all particles and then remove them with charged collectors. In water purification, the basic method is to trap the particles in water clusters and then to clean the clusters as such outside of the clean room. In water treatment, nanoparticles that are electrically loaded are quite easily trapped, and removed, by conventional ion‐exchange equipment, but non‐loaded particles are not as easily removed. Typically, materials that are crucial in semiconductor manufacture 4
such as silica, boron and arsenic are especially difficult to remove. Other threatening contaminants are small organic particles and acids. Unless methods are found to detect and remove all contaminants, these will, sooner or later, cause havoc to any manufacturer pressing further on the path of Moore, which could mean dreadful losses, since new semiconductor factories are billion dollar invest‐
ments designed to recoup costs in a very short time period. Xzero is a Swedish company dedicated to develop Zero Liquid Discharge equipment for semiconductor process water. The company brings entirely new technology called Membrane Distillation (MD) into the battle to uphold Moore’s Law. With this technology absolute purity is obtainable – if there is such a thing. Aapo Sääsk, May 19, 2001