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Semiconductor Technologies Guide
An anonymous reader writes "X-bit labs have posted an interesting article on manufacturing technologies used in the semiconductor industry. Good reading if you want to get a really indepth idea of technologies used for semiconductor manufacturing by IBM, Intel, AMD, and others."
My guess is that no other industry in the world has the pace of tangible progress as microprocessors (except perhaps magnetic storage). Look back 30 years. Microprocessors were still in their infancy. The product of microprocessors have gotten 10's of thousands of times more powerful. Automobile manufacturing was, however, much as it still is today. The vast majority of textiles manufacturing is similarly unchanged in the last 30 years. History has demonstrated, though, that any fundamentally new technology goes through a very rapid period of development in a relatively short period of time. Eventually, all technologies level off in their pace of development.
I'm not sure I can answer your question, but I want to clarify something. I found this on google: diagram of a mosfet transistor.
Here's a simplified explanation. Think of a switch with source at one terminal and drain on the other. When sitting without a voltage on the gate, the source and drain are not connected. When the switch is turned on (ie. gate high), electrons are allowed through the pathway created.
Anyways, the yellow in the diagram is an insulator. The switching is all done without touching the doped silicon connecting the source and the drain. My point is that the silicon needs to be there. It's integral to how the switching works. I don't know anything about nano-tubes but it cannot replace the silicon unless it can act like a semiconductor (both as a conductor and insulator depending on temp, etc). Perhaps it could replace the SiO2 currently used as the insulating layer but no matter what, the smaller the channels get, the more the electrons are going to want to jump..
Anyone that knows more about SOI want to comment?
They aren't currently used in CPU production, but IBM has developed a "Carbon NanoTube Field Effect Transistor" (CNTFET) which they seem to think will replace silicon. Look up "carbon nanotube FET" on google for links.
Carbon nanotubes are still very much in the experimental phase. While there are a lot of uses in which they may be useful, like as interconnects on ICs, the technology for mass manufacturing of nanotubes still does not exist.
I believe they can only be grown at the moment on AFM tips, or at least that is the only way they can really test them at the moment.
Well, the idea of using carbon nanotubes as transistors uses a completely different transistor model than a mosfet. The conductance of CNTs come about due to their orientation (imagine a plane of graphite rolled up - there are many ways to make the ends meet, akin to the steepness of a circular staircase). A few orientations are conducting, the rest are insulating.
Semiconducting CNTs occur when you put a twist on the CNT - i don't know the mechanism for that nor the theory behind it, but it is unrelated to the traditional transistor.
SOI is silicon on insulator, which is just an advanced technique used in transistor design - not necessary for the fundamentals of mosfets.
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Boy, thats 70ies stuff. Today, wet processing is avoided as much as it is possible. But you are right in one point, purely physical etching is not used frequently. However there are combined physical/chemical methods. Do a websearch on Reactive Ion Etching, Plasma Etching etc.
Carbon nanotubes can be mass produced. The problem is that modern production techniques are not selective, so the result is a jumble of nanotubes, some of which possess the desired electrical properties and many of which do not. The challenge then becomes removing the undesirable nanotubes and then organizing the remaining nanotubes into electrical circuits. Researchers are making great strides in removing the undesired nanotubes, but organizing those that remain is much more difficult.
On a small scale this can be done using AFM tips and I believe this is how IBM and others have demonstrated working nanotube-based devices. However, such a technique is impractical for large-scale production, where you need to interconnect millions of devices and significant work still remains to reach this goal.
this is THE most poorly written article i've actually tried to read on the web in years.
:D
I take it you don't read many articles on the web...
Anyway I agree the article is not really well written and the English is horrible, but it does give a nice, though very simplified, overview of some of the key problems of semiconductor processing and what various companies are doing to overcome them.
Being completely technically accurate for such an article is quite difficult. For example, when discussing high-k dielectrics, the article states that, "This material should be 10,000 more effective in preventing electron leakage from the channel to the gate than SiO2. If you have been reading attentively, you should realize the importance of this: the thickness of the nonconductive layer may now be reduced to tenths of nanometer keeping an acceptable gate leakage value."
The above contains many errors. For example the quantum mechanical tunneling through a layer (any material) a few tenths of a nanometer thick is enormous, so it can't be true that the high-k layer is thinner than SiO2. The reality is that high-k means the material has a higher dielectric constant than SiO2. This means that electric fields are transmitted more readily through the high-k material and so a thick high-k film exhibits the same electrical behavior as a much thinner SiO2 film.
Thus, the reality is that replacing SiO2 with a high-k material allows the use of a much thicker film, which behaves electrically as if it were thinner than the corresponding SiO2 film. Quantum mechanical tunneling of electrons through the gate dielectric drops exponentially with increasing thickness, so the leakage current is reduced dramatically through the use of the thicker film.