Intel Using New Material for Chips---In Addition to Silicon Dioxide

As reported on page B7 of the Wall Street Journal today, a historic shift is occurring as Intel starts utilizing a key new substance in its IC chips, added to the ubiquitous silicon dioxide. The material being utilized by Intel in their new chip called the Core 2 Extreme QX9650 is called hafnium dioxide.

"Hafnium [all general info on hafnium and hafnium dioxide to follow quoted from Wikepedia] is a chemical element that has the symbol Hf and atomic number 72. A lustrous, silvery gray tetravalent transition metal, hafnium resembles zirconium chemically and it is found in zirconium minerals.

"Hafnium dioxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride. It is used in optical coatings, and as a high-k dielectric in DRAM capacitors.

"The term high-k dielectric refers to a material with a high dielectric constant (k) (as compared to silicon dioxide) used in semiconductor manufacturing processes which replaces the silicon dioxide gate dielectric. The implementation of high-k gate dielectrics is one of several strategies developed to allow further miniaturization of microelectronic components, colloquially referred to as extending Moore's Law." [end Wikepedia]

from http://www.genus.com/glossary.html:

High k dielectric: An insulator which will not conduct electricity but which, when sandwiched between metal plates, will easily allow these plates to talk to each other via electric fields (this is called a capacitor structure). These can be used as memories, and one structure that is being considered for very high density DRAMs (dynamic random access memories) is a layer of barium strontium titanate (BST -- a high k dielectric) between platinum electrodes. While high k dielectrics are good for capacitors, the opposite is true of the insulators used to separate metal lines, for which low k dielectrics are desirable (see low k dielectric).

Next Material from:"Hafnium oxide helps make chips smaller and faster," Chemistry World, March 2007, http://www.rsc.org/chemistryworld/Issues/2007/March/HafniumOxideHelpsMakeChipsSmallerFaster.asp


"'Researchers have learnt to deposit very thin films of hafnium oxide and mix it with silica or silicon nitride at the molecular scale to tailor their insulating and charge storage properties,' explained Paul McIntyre from the Stanford University Engineering and Science Institute, California...

"But depositing conducting silicon gate materials on top of the insulating hafnium oxide is problematic. Though hafnium oxide is tough stuff, the high temperatures needed to lay down the silicon gate damage the insulator's surface, drastically reducing the transistor's clock speed compared to typical silicon gate/silica insulator devices. Enter Intel and IBM's secret new gate materials, which can be stuck to the dielectric at less extreme conditions.

'Research groups worldwide have demonstrated hafnium oxide-containing transistors with a variety of gate metal materials,' said McIntyre. 'These include titanium and hafnium nitrides, tungsten, ruthenium and ruthenium oxide and certain metal silicides,' he said. 'But mass producing reliable chips is a whole different ball game from single-device manufacture in the lab,' McIntyre told Chemistry World. 'Until we can buy the new chips and cut them open, we can't really know what gate metals Intel have chosen'...

"According to Gordon Moore, 'the implementation of high k and metal materials marks the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s.'"

These "new chips" are now on the market. Incredibly cool stuff and unfortunately I am buried with work and cannot pursue this. Here is some paraphrased material from the Chemistry World web site.

As they have been making the gates of transistors and IC chips smaller and smaller, they have now gotten down to gates that are only a few atoms wide. So, the electrons are utilizing quantum tunneling to go right through the gate, causing leakage of current and messing up the circuit. (Digital means everything is on or off---you don't want and off transistor leaking current. Quantum tunneling is a super cool phenomenon whereby electrons on one side of an impenetrable barrier sometimes appear on the other side of the barrier---without ever having actually passed through it---All in the parentheses are my own, possibly incorrect contributions.)

It has been known for a while that adding hafnium dioxide to the gate can rectify this problem. Unfortunately, silicon dioxide must be added on top of the HfO2, in this requires temperatures so high that the HfO2 is destroyed. So essentially, Intel and IBM came up with the "secret sauce" that solves this problem. Now that the chips are on the market, the techies can cut them open and figure out what this material is.